Description Field of the invention

The invention relates to a data reader for reading data from an optical data carrier as well as to a data reader system comprising the data reader and at least one optical data carrier. The invention further relates to a method for controlling a light beam in a data reader. The devices and methods according to the present invention generally may be applied in any field of data storage technology in which an optical readout of information contained in an optical data carrier by using at least one light beam is performed. Specifically, the invention may be applied in the field of compact discs (CDs) and/or in the field of digital versatile disks (DVDs). Still, other applications are feasible.

Prior art

The present invention is based on the general ideas on optical detectors as set forth e.g. in WO 2012/1 10924 A1 , US 2012/0206336 A1 , WO 2014/097181 A1 , US 2014/0291480 A1 or so far unpublished US provisional applications number 61/867,180 dated August 19, 2013,

61/906,430 dated November 20, 2013, and 61/914,402 dated December 1 1 , 2013, as well as unpublished German patent application number 10 2014 006 279.1 dated March 6, 2014, European patent application number 14171759.5 dated June 10, 2014, international patent application number PCT/EP2014/067466 dated August 15, 2014, US patent application number 14/460,540 dated August 15, 2014 and EP patent application number 14 186 792.9 filed on September 29, 2014, the full content of all of which is herewith included by reference.

In the art, a plurality of optical data carriers and devices for data readout from optical data carriers are known. Generally, one or more light beams are focused onto the optical data carrier and are reflected by information modules within the data carrier. The reflected light beam is monitored by a photodiode, which generates a modulated signal. By decoding the signal, information contained in the information modules may be recovered. Well known examples of optical data carriers are compact discs (CDs) and digital versatile disks (DVDs). In CD players or DVD players, typically, a laser beam is focused in a diffraction-limited fashion onto the CD or DVD disc, in order to read the data. As an example, for CD players, tracks having a width of approximately 600 nm are used. The discs rotate at high speed, which generally leads to the problem that, besides the rotation, an additional movement or oscillation of the disc in a direction of the rotation axis occurs. This uncontrolled vibrational movement of the optical data carrier typically necessitates a constant refocus of the laser. In known devices, this refocusing is performed by using an electromagnetic lens coupled to an electromagnetic coil. DE 25 01 1 24 A discloses a device for focussing a read-out light beam on a moving data carrier. It comprises an objective lens which causes said read-out beam to converge on the data carrier; a cylindrical lens arranged in the path of a light beam reflected by the data carrier; and photoelectric means for detecting the reflected beam and arranged in such a fashion that the light spot obtained there, normally substantially circular in shape, is distorted by elongation if focussing of the read-out beam on the data carrier is incorrect.

In order to generate control signals for controlling the laser beam, various controllers are used, such as for keeping the focused laser beam centered on the data track. Further, for keeping the laser beam in focus, a system referred to as the "Philips RAFOC" system is known which is based on the use of a photodiode array having four photodiodes arranged in a rectangular matrix. If in focus, all photodiodes provide identical signals. Thus, by comparing the signals of the single photodiodes, control signals for positioning the laser beam and for refocusing the laser beam may be generated.

Still, known methods and devices for controlling light beams in optical data storage systems face several technical challenges and drawbacks. Thus, as an example, systems based on an array of photodiodes generally are highly dependent on a beam quality of the laser beam, since the refocusing control signal is based on the fact that the laser beam provides an elliptic cross- section, the longer axis of which turns by 90° when comparing the cross-section on both sides of the focal plane. Further, control signals obtained by these arrays of photodiodes provide indirect information only, since no real information regarding the size of the light spot is generated. Further, with regard to a transversal positioning, no clear signal indicating a position of the light spot on the photodiodes is generated. Consequently, specifically in case high oscillations occur, a tracking of the focus may become technically challenging.

Generally, in the art, a large number of optical sensors which can be based generally on the use of inorganic and/or organic sensor materials are known from the prior art. Examples of such sensors are disclosed in US 2007/0176165 A1 , US 6,995,445 B2, DE 2501 124 A1 ,

DE 3225372 A1 or else in numerous other prior art documents. To an increasing extent, in particular for cost reasons and for reasons of large-area processing, sensors comprising at least one organic sensor material are being used, as described for example in US 2007/0176165 A1. In particular, so-called dye solar cells are increasingly of importance here, which are described generally, for example in WO 2009/013282 A1.

As a further example, WO 2013/144177 A1 discloses quinolinium dyes having a fluorinated counter anion, an electrode layer which comprises a porous film made of oxide semiconductor fine particles sensitized with these kinds of quinolinium dyes having a fluorinated counter anion, a photoelectric conversion device which comprises such a kind of electrode layer, and a dye sensitized solar cell which comprises such a photoelectric conversion device.

A large number of detectors for detecting at least one object are known on the basis of such optical sensors. Such detectors can be embodied in diverse ways, depending on the respective purpose of use. Examples of such detectors are imaging devices, for example, cameras and/or microscopes. High-resolution confocal microscopes are known, for example, which can be used in particular in the field of medical technology and biology in order to examine biological samples with high optical resolution. Further examples of detectors for optically detecting at least one object are distance measuring devices based, for example, on propagation time methods of corresponding optical signals, for example laser pulses. Further examples of detectors for optically detecting objects are triangulation systems, by means of which distance measurements can likewise be carried out. In US 2007/0080925 A1 , a low power consumption display device is disclosed. Therein, photoactive layers are utilized that both respond to electrical energy to allow a display device to display information and that generate electrical energy in response to incident radiation. Display pixels of a single display device may be divided into displaying and generating pixels. The displaying pixels may display information and the generating pixels may generate electrical energy. The generated electrical energy may be used to provide power to drive an image.

In EP 1 667 246 A1 , a sensor element capable of sensing more than one spectral band of electromagnetic radiation with the same spatial location is disclosed. The element consists of a stack of sub-elements, each capable of sensing different spectral bands of electromagnetic radiation. The sub-elements each contain a non-silicon semiconductor where the non-silicon semiconductor in each sub-element is sensitive to and/or has been sensitized to be sensitive to different spectral bands of electromagnetic radiation.

In WO 2012/1 10924 A1 and US 2012/0206336 A1 , the full content of which is herewith included by reference, a detector for optically detecting at least one object is proposed. The detector comprises at least one optical sensor. The optical sensor has at least one sensor region. The optical sensor is designed to generate at least one sensor signal in a manner dependent on an illumination of the sensor region. The sensor signal, given the same total power of the illumination, is dependent on a geometry of the illumination, in particular on a beam cross section of the illumination on the sensor area. The detector, furthermore, has at least one evaluation device. The evaluation device is designed to generate at least one item of geometrical information from the sensor signal, in particular at least one item of geometrical information about the illumination and/or the object. US 2014/0291480 A1 and WO 2014/097181 A1 , the full content of all of which is herewith included by reference, disclose a method and a detector for determining a position of at least one object, by using at least one longitudinal optical sensor and at least one transversal optical sensor. Specifically, the use of sensor stacks is disclosed, in order to determine a longitudinal position of the object with a high degree of accuracy and without ambiguity.

EP patent application number 14 186 792.9 filed on September 29, 2014, the full content of all of which is herewith included by reference discloses a detector for optically determining a position of at least one object, comprising: at least one optical sensor for determining a position of at least one light beam traveling from the object to the detector, wherein the optical sensor has at least a first electrode and a second electrode, wherein at least one photovoltaic material is embedded in between the first electrode and the second electrode, wherein the photovoltaic material is adapted to generate electric charges in response to an illumination of the photovoltaic material with light, wherein the first electrode or the second electrode is a split electrode having at least three partial electrodes, wherein each partial electrode is adapted to generate at least one sensor signal, wherein the sensor signal is dependent on a beam cross-section of the light beam in a sensor region of the optical sensor;

- at least one evaluation device, wherein the evaluation device is designed to generate at least one item of information on a transversal position of the object, the transversal position being a position in at least one plane perpendicular to an optical axis of the detector, by evaluating the sensor signal of pairs of the partial electrodes, and wherein the evaluation device is designed to generate at least one item of information on a longitudinal position of the object (1 12) by evaluating a sum of the sensor signals of all partial electrodes.

Despite the advantages implied by the above-mentioned devices and detectors, there still is a need for a simple, cost-efficient and, still, reliable data reader for reading data from an optical data carrier. Specifically, reliability regarding a stability of the control of the light beam even at high rotational speeds of the data carriers remains an issue.

Problem addressed by the invention

It is therefore an object of the present invention to provide a data reader, a data reader system and a method for reading data from an optical data carrier which fully or partially avoid the above-mentioned technical problems. Specifically, the instant devices shall be disclosed which, in a simple, cost-efficient and still reliable fashion provide control of light beams in data readers even at high rotational speed. Summary of the invention

This problem is solved by the invention with the features of the independent patent claims. Advantageous developments of the invention, which can be realized individually or in

combination, are presented in the dependent claims and/or in the following specification and detailed embodiments.

As used in the following, the terms "have", "comprise" or "include" or any arbitrary grammatical variations thereof are used in a non-exclusive way. Thus, these terms may both refer to a situation in which, besides the feature introduced by these terms, no further features are present in the entity described in this context and to a situation in which one or more further features are present. As an example, the expressions "A has B", "A comprises B" and "A includes B" may refer to both a situation in which, besides B, no other element is present in A (i.e. a situation in which A solely and exclusively consists of B) and to a situation in which, besides B, one or more further elements are present in entity A, such as element C, elements C and D or even further elements.

Further, it shall be noted that the terms "at least one", "one or more" or similar expressions indicating that a feature or element may be present once or more than once typically will be used only once when introducing the respective feature or element. In the following, in most cases, when referring to the respective feature or element, the expressions "at least one" or "one or more" will not be repeated, non-withstanding the fact that the respective feature or element may be present once or more than once.

Further, as used in the following, the terms "preferably", "more preferably", "particularly", "more particularly", "specifically", "more specifically" or similar terms are used in conjunction with optional features, without restricting alternative possibilities. Thus, features introduced by these terms are optional features and are not intended to restrict the scope of the claims in any way. The invention may, as the skilled person will recognize, be performed by using alternative features. Similarly, features introduced by "in an embodiment of the invention" or similar expressions are intended to be optional features, without any restriction regarding alternative embodiments of the invention, without any restrictions regarding the scope of the invention and without any restriction regarding the possibility of combining the features introduced in such a way with other optional or non-optional features of the invention.

In a first aspect of the present invention, a data reader for reading data from an optical data carrier is disclosed. As used herein, a "data reader" generally refers to a device adapted for retrieving data stored in a data carrier. The data reader may further be adapted to decode data and to transform data into another format. The term "data carrier" generally refers to a device adapted for storing data. Consequently, the term "optical data carrier" generally refers to a data carrier in which data may be stored in such a way that an optical readout, i.e. a data readout by using optical means such as one or more light beams is possible. Specifically, the optical data carrier may comprise a plurality of information modules which exhibit distinguishable optical properties such as a reflectance, an index of refraction, a transmissivity or another optical property which distinguishes an information module from a surrounding matrix. Consequently, a data readout may take place by using one or more light beams which are transmitted, reflected or in any other way affected by the information modules. As an example, the at least one data carrier may be or may comprise at least one compact disc (CD) and at least one digital versatile disc (DVD). Thus, specifically, the data reader may be or may comprise a CD player and/or a DVD player. Still, other formats of data carriers and/or data readers are feasible. Thus, generally, the present invention may be applied in the field of optical data readers in which a precise alignment of the optical data carrier is required. Thus, as an example, one or more of the following data readers or data reader systems may be named in which the invention may be implemented: CD, Mini Disc, Blue Ray, versatile multilayer disc, Holographic versatile disc, Universal media disc, multiplexed optical storage disc. Still, other applications are feasible. The data reader comprises at least one light source for generating at least one light beam. As an example, the light source may comprise one or more semiconductor light sources such as one or more laser diodes and/or one or more light-emitting diodes. Still, other types of light sources may be used in addition and/or alternatively.

The data reader is configured to direct the light beam onto the optical data carrier. For directing the light beam onto the optical data carrier, the data reader may directly shine the light beam onto the optical data carrier or may comprise at least one beam positioning device such as one or more reflective elements like mirrors and/or lenses adapted for changing one or more of a position, an orientation or a focus of the light beam.

The data reader further comprises at least one beam alignment module, wherein the beam alignment module comprises:

at least one longitudinal optical sensor, the longitudinal optical sensor being configured to detect the light beam or a part thereof after reflection by the optical data carrier, wherein the longitudinal optical sensor has at least one sensor region, wherein the longitudinal optical sensor is designed to generate at least one longitudinal sensor signal in a manner dependent on an illumination of the sensor region by the light beam, wherein the longitudinal sensor signal, given the same total power of the illumination, is dependent on a beam cross-section of a light spot generated by the light beam in the sensor region;

at least one control device configured to compare the longitudinal sensor signal with at least one predetermined longitudinal sensor signal and to generate at least one longitudinal control signal;

at least one beam positioning device configured to receive the control signal and to modify a focal position of the light beam in a controlled fashion.

As used herein, a "longitudinal optical sensor" generally refers to a sensor which is adapted to provide a longitudinal sensor signal being dependent on a beam cross-section of a light spot generated by the light beam in the sensor region. Thus, generally, any optical sensor may be used which exhibits a nonlinear behavior in such a way that, in case a light beam is shone onto a sensor region, the sensor signal varies when the light beam is focused or defocused.

Specifically, the sensor region may be a large area sensor region which is not subdivided into partial sensor regions and which generates a uniform sensor signal. Nonlinear behavior, with the sensor signal, given the same total power of illumination, depending on a size of the light spot and, thus, varying with focusing or a defocusing, occurs in organic optical sensors, inorganic optical sensors as well as in hybrid devices.

As discussed in earlier applications, such as in WO 2012/1 10924 A1 , US 2012/0206336 A1 , US 2014/0291480 A1 or WO 2014/097181 A1 , this effect of non-linearity of optical sensors may also be referred to as the "FiP" effect, since, given the same total power P of illumination, the signal i depends on a flux or photon density of the illumination. Consequently, in the following, the longitudinal optical sensor exhibiting the mentioned effect is also referred to as a "FiP sensor". For potential embodiments of the at least one longitudinal optical sensor, reference may be made to one or more of the above mentioned earlier applications. Specifically, the layer setups and/or materials mentioned therein may also be used in the context of the present invention, specifically in the context of the at least one longitudinal optical sensor. Still, other embodiments are feasible, such as the use of one or more other optical sensors exhibiting the nonlinearity mentioned above, such as nonlinear inorganic photodiodes or nonlinear photo- conducting devices.

For the skilled person, determining whether an optical sensor exhibits the above-mentioned nonlinearities or not, is rather simple. Thus, as an example, a simple experiment is sufficient for empirically determining whether the optical sensor is linear (i.e. does not show the above- mentioned FiP effect) or nonlinear (i.e. shows the above-mentioned FiP effect). For this purpose, a light beam may be shone onto a sensor region of the optical sensor to be tested, and the sensor signal is monitored. When changing a size of a light spot generated by the light beam on the sensor region, such as by using a lens and shifting lens along an optical axis of the light beam, in linear optical sensors, the sensor signal does not change, as long as the light spot is fully located within the sensor region. Contrarily, in nonlinear optical sensors, the sensor signal changes when the size of the light spot is changed.

The nonlinear behavior may occur with unmodulated light beams, i.e. continuous light beams, or may occur when modulated light beams are used, such as light beams modulated by a chopper, a modulated source current in laser diodes or the like. Testing the behavior of the optical sensor in question as various modulation frequencies and with unmodulated light beams may be part of the above-mentioned simple experiment for determining if the optical sensor is a FiP sensor or not. By way of example, the data reader can be designed to bring about a modulation of the light beam with a frequency of 0.05 Hz to 1 MHz, such as 0.1 Hz to 10 kHz. As outlined above, for this purpose, the data reader may comprise at least one modulation device, which may be integrated into the at least one light source and/or may be independent from the light source. Thus, at least one light source might, by itself, be adapted to generate the above-mentioned modulation of the light beam, and/or at least one independent modulation device may be present, such as at least one chopper and/or at least one device having a modulated

transmissibility, such as at least one electro-optical device and/or at least one acousto-optical device. The at least one control device generally may be an arbitrary device, specifically a controller, which is adapted to compare two or more signals and to generate at least one control signal in response. These controllers are widely used in the field of electronics. As a simple example, the controller may comprise an operational amplifier with two input ports and an output port. Other, more complex setups are feasible and generally known to the skilled person in the field of control electronics. The control device may be or may comprise one or more electronic components, such as one or more transistors and/or operational amplifiers, as well as one or more additional electronic components such as passive components like e.g. resistors and/or capacitors. The control device may also be embodied as an integrated circuit such as an integrated circuit chip, more specifically an application-specific integrated circuit (ASIC). Still, other embodiments are feasible.

The at least one control device may, thus, comprise one or more electronic components.

Besides the above-mentioned components, the control device may also comprise one or more data processing devices and/or data storage devices. As an example, the control device may comprise one or more computers. The operation of the data reader may fully or partially be supported and/or performed by one or more computer programs. Alternatively, however, a purely non-software-controlled operation may be feasible, as is the case for many electronic controllers. The at least one control device may further comprise one or more of an amplifier, a filter or a converter, such as an analogue-digital converter and/or a digital-analogue-converter or the like.

The at least one predetermined longitudinal sensor signal generally may be an arbitrary electronic signal like a voltage and/or a current. The electronic signal may be provided by one or more voltage and/or current sources which may be part of the control device or which may be fully or partially embodied as external components. Specifically, the at least one predetermined longitudinal sensor signal may be an adjustable sensor signal which may be adjusted by a user, operator or another electronic component. For adjusting and, thus, for determining the at least one predetermined longitudinal sensor signal, a manual adjustment and/or an automatic adjustment may thus be feasible.

The at least one predetermined longitudinal sensor signal corresponds to a desired longitudinal sensor signal which is generated by the at least one longitudinal optical sensor when the light spot generated by the light beam in the sensor region has a predetermined or desired size. Thus, as an example, the light beam generated by the light source may have well defined optical properties, per se or after one or more beam-shaping processes by one or more beam- shaping elements like one or more lenses, prisms or the like. Specifically, the light beam may be shaped such that a focal position of the light beam is on or in the optical data carrier. When the light beam is reflected by the optical data carrier, such as by one or more information modules contained therein, the light beam widens again. As an example, the light beam may have Gaussian beam propagation properties and may widen according to well-known Gaussian beam equations. Consequently, after reflection by the optical data carrier, once the reflected light beam hits the at least one longitudinal optical sensor, the light beam has a beam cross- section which is determined by the position of the optical data carrier by the length of the beam path between the light source, the optical data carrier and the at least one longitudinal optical sensor. Therefore, by predetermining the predetermined longitudinal sensor signal, a

predetermined length of the beam path is defined and, thus, a predetermined position of the optical data carrier.

As further used herein, a "beam positioning device" generally refers to an arbitrary device adapted for modifying one or more of a focal position of the light beam, an orientation of the light beam or an optical axis of the light beam. As an example, the at least one beam positioning device may be or may comprise at least one lens and/or curved mirror, as known in the above- mentioned CD player technology. Still, additionally or alternatively, one or more other optical elements may be used in the beam positioning device. The beam positioning device is adapted to receive the control signal and to modify the focal position of the light beam in a controlled fashion. As an example, the beam positioning device may comprise one or more actuators such as electromechanical actuators, which are used for modifying one or more of a position and/or an orientation of one or more lenses and/or curved mirrors, wherein the one or more actuators are controlled by the control signal provided by the control device and/or by one or more secondary signals derived thereof. Specifically, the control signal may be or may comprise at least one current and/or at least one voltage, wherein the beam positioning device modifies the position and/or orientation of the at least one lens and/or curved mirror according to the current and/or voltage. The control device specifically may be configured to generate the control signal in such a way that a focal position of the light beam is on the optical data carrier. Thus, as outlined above, the predetermined longitudinal sensor signal predetermines a beam cross-section of the light spot, such as a beam width like e.g. a Gaussian beam width, a diameter, an equivalent diameter, a radius or an equivalent radius, and, thus, predetermines a length of a beam path along which the light beam travels. Since the actual length of the beam path depends on the position of the optical data carrier, the control signal may be generated in such a way that the focal position of the light beam is located on or in the optical data carrier. As an example, when the optical data carrier moves away from the light source and the beam positioning device, the actual length of the beam path is increased and, thus, the actually generated light spot in the sensor region of the longitudinal optical sensor widens, thereby changing the longitudinal sensor signal.

Consequently, a control signal may be generated, which moves the beam positioning device, thereby repositioning the focal position of the light beam onto or into the optical data carrier. Thereby, the beam cross-section of the light spot generated by the reflected light beam in the sensor region of the longitudinal optical sensor, decreases until the predetermined or desired cross-section is reached.

The light beam generated by the light source may be used for positioning purposes, only.

Alternatively, the light beam may also be used for data readout from the optical data carrier. In the first case, the light beam is a positioning light beam, only, whereas, in the second case, the at least one light beam is a dual use light beam which functions both as a positioning light beam and as a readout light beam. As an example, the reflected light beam may be split into two or more partial light beams, wherein at least one of the partial light beams is directed onto the at least one longitudinal optical sensor and wherein at least another one of the partial light beams is directed onto a data reader sensor such as a photo diode or the like, for the purpose of demodulation and/or decoding information contained therein.

The data may further comprise at least one data carrier actuator for positioning the optical data carrier. The data carrier actuator may be adapted for modifying at least one of an absolute position of an orientation of the optical data carrier. Thereby, in order to readout various positions within the optical data carrier, a position of the readout light beam, a position of the optical data carrier with respect to the light beam or both may be modified. As an example, the data carrier actuator may comprise at least one motor for rotating the optical data carrier, specifically in case rotationally symmetric optical data carriers like CDs or DVDs are used.

The data reader may further comprise at least one receptacle configured to receive the optical data carrier. As an example, the data reader may comprise a housing having an opening or a slot or another type of accessible or openable port for receiving the optical data carrier. As outlined above, the optical data carrier preferably may have a disc shape, such as a circular disc shape. However, other types of optical data carriers are feasible.

The beam positioning device may comprise at least one movable lens and at least one lens positioning actuator configured to adjust one or more of a position or an orientation of the movable lens. The lens positioning actuator may comprise at least one electromagnetic actuator. Additionally or alternatively, other types of beam positioning devices and/or actuators may be used, as outlined above.

Further possible details refer to the at least one longitudinal optical sensor. Thus, specifically, the longitudinal sensor signal may steadily rise or steadily decrease with decreasing cross- section of the light spot. The longitudinal sensor signal may thus be a steady function of the cross-section of the light spot, i.e. of the diameter, equivalent diameter, radius, equivalent radius or any other parameter indicating a width or size of the light spot. As outlined above, the at least one predetermined longitudinal sensor signal may be

predetermined such that a focal position of the light beam is located on or in the optical data carrier.

The longitudinal optical sensor, as outlined above, may comprise at least one nonlinear photosensitive element. The nonlinear photosensitive element specifically may comprise at least one of: a photoconductor having a nonlinear behavior, specifically one of an organic photoconductor, an inorganic photoconductor or a hybrid photoconductor; a photovoltaic element having a nonlinear behavior, specifically one of an organic photovoltaic element or an inorganic photovoltaic element; an organic solar cell, more specifically a dye-sensitized solar cell. With regard to the expression "nonlinear", reference may be made to the definition given above. Specifically, the nonlinearity of the behavior resides in the fact that the sensor signal, given the same total power of illumination, is dependent on a size of the light spot in the sensor region. The longitudinal optical sensor may comprise at least one first electrode, at least one n- semiconducting metal oxide, at least one dye, at least one p-semiconducting organic material, preferably a solid p-semiconducting organic material, and at least one second electrode. At least one of the first electrode and the second electrode may be transparent. Specifically, in order to generate a fully transparent longitudinal optical sensor, both the first electrode and the second electrode may be embodied as transparent electrodes.

The data reader may comprise a single longitudinal optical sensor or may comprise a plurality of longitudinal optical sensors, wherein the longitudinal optical sensors may be stacked. The longitudinal optical sensors may be arranged such that the light beam illuminates all longitudinal optical sensors, wherein at least one longitudinal sensor signal is generated by each

longitudinal optical sensor, wherein the data reader is adapted to normalize the longitudinal sensor signals independent from an intensity of the light beam. Thereby, by normalizing the signals, e.g. by dividing all signals by a mean value or a maximum value of the longitudinal sensor signals, the longitudinal sensor signals may have been rendered independent from the intensity of the overall power of the light beam.

In case a stack of longitudinal optical sensors is provided, a last longitudinal optical sensor may be arranged in a manner that the light beam illuminates all other longitudinal optical sensors apart from the last longitudinal optical sensor, until the light beam impinges on the last longitudinal optical sensor. The last longitudinal optical sensor may be transparent or intransparent with respect to the light beam. By using the above-described FiP effect and the at least one longitudinal optical sensor, a longitudinal position of the optical data carrier and/or of the focal position of the light beam may be monitored and controlled, specifically such that the focal position of the light beam is always in and/or on the optical data carrier. Therein, the direction of propagation of the light beam defines a longitudinal position, in the following also referred to as z-position. Additionally, however, at least one transversal position may be monitored and/or controlled. Thus, the position of the light beam in and/or on the optical data carrier may be controlled. For this purpose, a transversal position of the reflected light beam or a part thereof may be monitored.

For monitoring the transversal position of the light beam, i.e. a position in a direction

perpendicular to a direction of propagation of the light beam, at least one transversal optical sensor may be provided. Specifically, at least one transversal optical sensor may be used which is based on the fact that photo-generated charge carriers may induce electrical currents in a plurality of electrodes provided in a lateral arrangement next to each other on a sensor surface facing the incoming light beam, wherein the electrical currents depend on the distance between the place of the photo-generation of the charge carriers and the respective electrode. Thus, by comparing the electrical currents, the location of the photo-generation of the charge carriers, and, thus, the location of the light spot may be determined. This principle of generating a transversal optical sensor is generally described in US 2014/0291480 A1 or WO 2014/097181 A1 , both of which are herewith included by reference. The transversal optical sensors described therein may also be used in the present invention. Still, the use of other types of transversal optical sensors is feasible. Implementing this idea of monitoring the transversal position of the light beam on or in the optical data carrier, the data reader may further comprise:

at least one transversal optical sensor, the transversal optical sensor being configured to detect the light beam or a part thereof after reflection by the optical data carrier, the transversal optical sensor further being configured to determine a transversal position of the light beam or the part thereof, the transversal position being a position in at least one dimension

perpendicular to an optical axis of the transversal optical sensor, the transversal optical sensor further being configured to generate at least one transversal sensor signal. In this setup, the control device may further be configured to compare the transversal sensor signal with at least one predetermined transversal sensor signal and to generate at least one transversal control signal.

As an example, the predetermined transversal sensor signal may be a transversal sensor signal which is generated when the light beam is in a predetermined position, such as by generating a light spot on or in the transversal optical sensor in a predetermined location or position on or in the transversal optical sensor. As an example, when the light beam hits a predetermined position on or in the optical data carrier and is reflected, the light beam or reflected light beam hits the transversal optical sensor in the predetermined position, whereas deviations lead to a deviating position of the light spot.

The beam positioning device may further be configured to receive the transversal control signal and to modify a transversal position of a light spot generated by the light beam on or in the optical data carrier. Thus, as an example, the beam positioning device may be adapted to transversely shift and/or pivot the light beam before illuminating the optical data carrier, thereby changing a transversal position of the light beam on and/or in the optical data carrier. Again, as outlined above, this shifting and/or pivoting may be performed by at least one movable or controllable lens which may be identical to the above-mentioned lens for controlling a focal position or which may also be a different lens. Additionally or alternatively, other types of optical elements may be used for changing the position and/or orientation of the light beam, such as one or more reflective elements and/or prisms.

As used herein, the term "transversal optical sensor" generally refers to an arbitrary optical sensor which is adapted to determine a transversal position of a light beam or a part thereof, such as by determining a position of a light spot generated on a sensitive area or sensor area, also referred to as a sensor surface, of the transversal optical sensor, in a plane of the sensor area, which typically is oriented substantially perpendicular to the incoming light beam.

Consequently, the optical axis of the transversal optical sensor may be defined by an axis perpendicular to a sensor surface of the transversal optical sensor. As outlined above, the optical axis of the data reader, at a specific location, may be defined by a direction of propagation of the light beam or a part thereof in this location. Preferably, the optical axis of the transversal optical sensor and the optical axis of the data reader are substantially parallel, such as parallel or deviating from a parallel orientation by no more than 10°, preferably no more than 5°.

As outlined above, a local coordinate system may be defined, with a z-axis parallel to a direction of propagation of the light beam, i.e. a longitudinal direction. A direction perpendicular to the z- axis is referred to as a transversal direction, and a coordinate system with an x-axis

perpendicular to the z-axis and with a y-axis perpendicular to both the z-axis and the x-axis may be defined, thereby generating a Cartesian coordinate system. However, other transversal coordinates may be used, such as cylindrical coordinates with a radius and an angle, in order to define a transversal position.

As outlined above, the transversal optical sensor, as an example, may comprise a

photosensitive element having two or more electrodes located in the sensor area, wherein a position of a light spot generated by the light beam in the sensor area causes differing signals such as currents detectable by the electrodes, the signals depending on the distance between the respective electrode and the light spot. Examples of these multiple electrode or split electrode setups are given in US 2014/0291480 A1 or WO 2014/097181 A1 , the full disclosure of which is herewith included by reference. Further, reference may also be made to US

6,995,445 or US 2007/0176165 A1 , which both disclose further potential embodiments of optical sensors which may be used as transversal optical sensors in the present invention. Still, other transfers optical sensors may be used in addition or alternatively.

The at least one longitudinal optical sensor and the at least one transversal optical sensor may be located in various ways. As an example, one or both of the longitudinal optical sensor or the transversal optical sensor may be transparent, thereby allowing for the light beam or reflected light beam or a part thereof firstly passing through the transversal optical sensor before hitting the longitudinal optical sensor or firstly passing through the longitudinal optical sensor before hitting the transversal optical sensor. Thus, as an example, the at least one transversal optical sensor and the at least one longitudinal optical sensor may be stacked. Alternatively, the reflected light beam or a part thereof may be split into two or more partial light beams, wherein one partial light beam is directed onto the at least one longitudinal optical sensor and wherein at least another partial light beam is directed onto the at least one transversal optical sensor.

Again, alternatively, the at least one longitudinal optical sensor and the at least one transversal optical sensor, besides the option of forming these devices as separate devices, may fully or partially be integrated into one and the same device, sharing one or more or even all components.

As outlined above and as will be outlined in further detail below, various embodiments of the at least one transversal optical sensor are feasible. Thus, as an example, the transversal optical sensor may comprise at least one photo detector having at least one first electrode, at least one second electrode and at least one photovoltaic material, wherein the photovoltaic material is embedded in between the first electrode and the second electrode, wherein the photovoltaic material is adapted to generate electric charges in response to an illumination of the photovoltaic material with light, wherein the second electrode is a split electrode having at least two partial electrodes, wherein the transversal optical sensor has a sensor region, wherein the at least one transversal sensor signal indicates a position of the light beam in the sensor region. Therein, electrical currents through the partial electrodes may be dependent on a position of the light beam in the sensor region. The transversal optical sensor may be adapted to generate the transversal sensor signal in accordance with the electrical currents through the partial electrodes. As an example, the electrical currents through the partial electrodes themselves may be used as transversal sensor signals, and each electrical current may be compared with a predetermined current by the control device. Alternatively, one or more combined transversal sensor signal may be generated by the transversal optical sensor and/or the control device, such as by combining the currents. The at least one combined sensor signal may be compared with at least one predetermined transversal sensor signal. As an example, a combined sensor signal may be generated for an x-direction, and at least one combined sensor signal may be generated for a y-direction, and the signal for the x-direction may be compared with a predetermined signal for the x-direction, and the signal for the y-direction may be compared with a predetermined signal for the y-direction. Other embodiments are feasible.

The control device may be configured to generate the transversal control signal in such a way that the electrical currents through the partial electrodes are equalized. In other words, the control device may be configured to control the position and/or orientation of the light beam in such a way that the light beam, by the at least one optical data carrier, is reflected right into the middle between the partial electrodes, thereby generating a light spot which is equidistantially spaced apart from the partial electrodes. The control device may thus be configured to generate the transversal control signal in such a way that the light beam impinges onto the photovoltaic material right in the middle between the partial electrodes.

The photo detector specifically may be or may comprise at least one dye-sensitized solar cell. Still, other embodiments are feasible. The first electrode may at least partially be made of at least one transparent conductive oxide, and the second electrode may at least partially be made of an electrically conductive polymer, preferably a transparent electrically conductive polymer. Other embodiments are feasible.

The transversal optical sensor may be intransparent or transparent. Transparency specifically may be generated by using appropriate transparent electrode materials for both electrodes.

As outlined above, the above-mentioned FiP effect may occur in continuous waves or unmodulated light beams. In some optical sensors, however, the FiP effect may be provoked or increased by using a modulated light beam. Thus, the longitudinal optical sensor may be designed in such a way that the longitudinal sensor signal, given the same total power of the illumination, is dependent on a modulation frequency of a modulation of the illumination. In these embodiments, the modulation of the light beam may be generated in various ways.

Specifically, the data reader may further comprise at least one modulation device for modulating the light beam. The modulation device may be integrated into the light source and/or may fully or partially be located in a beam path in between the light source and the at least one longitudinal optical sensor. As an example, a chopper may be used. The data reader may further comprise at least one decoding module configured to decode information contained in the reflected light beam or a part thereof. Thus, as outlined above, the light beam used for positioning may also be used for data readout. Alternatively, different light beams may be used. In a further aspect of the present invention, a data reader system is proposed, comprising the data reader according to any one of the above-described embodiments and/or according to one or more of the embodiments described in further detail below. Further, the data reader system comprises at least one optical data carrier. In a further aspect of the present invention, a method for controlling a light beam in a data reader is disclosed. Therein, a data reader according to the present invention, i.e. according to any one of the embodiments described above and/or according to any one of the embodiments described in further detail below, is used. The method comprises the following steps which, preferably, are performed in the given order. However, another order of the method steps may be used. Further, two or more of the method steps may be performed in parallel or in a fashion overlapping in time. Further, one, more than one or even all of the method steps may be performed repeatedly. The method may further comprise one or more additional method steps which are not listed. The method steps comprised by the method are as follows:

detecting the light beam or a part thereof after reflection by an optical data carrier and generating at least one longitudinal sensor signal in a manner dependent on an illumination of the sensor region of the longitudinal optical sensor by the light beam, wherein the longitudinal sensor signal, given the same total power of the illumination, is dependent on a beam cross- section of a light spot generated by the light beam in the sensor region;

comparing the longitudinal sensor signal with at least one predetermined longitudinal sensor signal and generating at least one longitudinal control signal; and

modifying a focal position of the light beam in accordance with the longitudinal control signal.

The detecting of the light beam takes place by using the at least one longitudinal optical sensor. For definitions and optional details, reference may be made to the above-mentioned disclosure of the data reader. The modification of the focal position of the light beam in a controlled fashion, as outlined above, may take place by using at least one movable lens and/or another type of beam positioning device. The modification takes place in a controlled fashion, i.e.

controlled by the control device and the at least one longitudinal control signal generated by the control device. In a further embodiment of the method, any one of the embodiments of the data reader having the at least one above-mentioned and above-defined transversal optical sensor is used. Thus, in a further embodiment of the method, the data reader further comprises the at least one transversal optical sensor, wherein the method further comprises:

- detecting the light beam or a part thereof after reflection by the optical data carrier by using the transversal optical sensor and generating at least one transversal sensor signal;

comparing the transversal sensor signal with at least one predetermined transversal sensor signal and generating at least one transversal control signal; and

modifying a transversal position of a light spot generated by the light beam on or in the optical data carrier in accordance with the transversal control signal.

Again, for potential details, definitions and options, reference may be made to the disclosure of the data reader given above or given in further detail below. As discussed above, various types of transversal optical sensors and/or longitudinal optical sensors may be used in the context of the present invention. Without limiting the scope of the invention, and without precluding the option of using inorganic devices, the at least one transversal optical sensor and/or the at least one longitudinal optical sensor may be or may comprise one or more photodetectors, preferably one or more organic photodetectors and, most preferably, one or more dye-sensitized organic solar cells (DSCs, also referred to as dye solar cells), such as one or more solid dye-sensitized organic solar cells (s-DSCs). Thus, preferably, the detector may comprise one or more DSCs (such as one or more sDSCs) acting as the at least one transversal optical sensor and one or more DSCs (such as one or more sDSCs) acting as the at least one longitudinal optical sensor, preferably a stack of a plurality of DSCs (preferably a stack of a plurality of sDSCs) acting as the at least one longitudinal optical sensor.

As outlined above, preferably, the transversal optical sensor is a photo detector having at least one first electrode, at least one second electrode and at least one photovoltaic material, wherein the photovoltaic material is embedded in between the first electrode and the second electrode. As used herein, a photovoltaic material generally is a material or combination of materials adapted to generate electric charges in response to an illumination of the photovoltaic material with light.

As used herein, the term light generally refers to electromagnetic radiation in one or more of the visible spectral range, the ultraviolet spectral range and the infrared spectral range. Therein, the term visible spectral range generally refers to a spectral range of 380 nm to 780 nm. The term infrared (IR) spectral range generally refers to electromagnetic radiation in the range of 780 nm to 1000 μηη, preferably in the range of 780 nm to 3.0 μηη. The term ultraviolet spectral range generally refers to electromagnetic radiation in the range of 1 nm to 380 nm, preferably in the range of 100 nm to 380 nm. Preferably, light as used within the present invention is visible light, i.e. light in the visible spectral range. The term light beam generally refers to an amount of light emitted into a specific direction. Thus, the light beam may be a bundle of the light rays having a predetermined extension in a direction perpendicular to a direction of propagation of the light beam. Preferably, the light beam may be or may comprise one or more Gaussian light beams which may be characterized by one or more Gaussian beam parameters, such as one or more of a beam waist, a Rayleigh-length or any other beam parameter or combination of beam parameters suited to characterize a development of a beam diameter and/or a beam propagation in space.

Preferably, the second electrode of the transversal optical sensor may be a split electrode having at least two partial electrodes, wherein the transversal optical sensor has a sensor area, wherein the at least one transversal sensor signal indicates a position of the light beam in the sensor area or of a light spot generated by the light beam in the sensor area. Thus, as outlined above, the transversal optical sensor may be or may comprise one or more photodetectors, preferably one or more organic photodetectors, more preferably one or more DSCs or sDSCs. The sensor area may be a surface of the photodetector facing towards the optical data carrier and/or facing towards the incoming light beam. The sensor area preferably may be oriented perpendicular to the optical axis. Thus, the transversal sensor signal may indicate a position of a light spot generated by the light beam in a plane of the sensor area of the transversal optical sensor.

Generally, as used herein, the term partial electrode refers to an electrode out of a plurality of electrodes, adapted for measuring at least one current and/or voltage signal, preferably independent from other partial electrodes. Thus, in case a plurality of partial electrodes is provided, the second electrode is adapted to provide a plurality of electric potentials and/or electric currents and/or voltages via the at least two partial electrodes, which may be measured and/or used independently.

When using at least one transversal optical sensor having at least one split electrode having two or more partial electrodes as a second electrode, currents through the partial electrodes may be dependent on a position of the light beam in the sensor area. This may generally be due to the fact that Ohmic losses or resistive losses may occur on the way from a location of generation of electrical charges due to the impinging light to the partial electrodes. Thus, besides the partial electrodes, the second electrode may comprise one or more additional electrode materials connected to the partial electrodes, wherein the one or more additional electrode materials provide an electrical resistance. Thus, due to the Ohmic losses on the way from the location of generation of the electric charges to the partial electrodes through with the one or more additional electrode materials, the currents through the partial electrodes depend on the location of the generation of the electric charges and, thus, to the position of the light beam in the sensor area. For details of this principle of determining the position of the light beam in the sensor area, reference may be made to the preferred embodiments below and/or to the physical principles and device options as disclosed e.g. in one or more of US 2014/0291480 A1 , WO 2014/097181 A1 , US 6,995,445 or US 2007/0176165 A1 . The partial electrodes generally may be defined in various ways, in order to generate at least one transversal sensor signal and/or in order to determine a position of the light beam in the sensor area. Thus, two or more horizontal partial electrodes may be provided in order to determine a horizontal coordinate or x-coordinate, and two or more vertical partial electrodes may be provided in order to determine a vertical coordinate or y-coordinate. Thus, the partial electrodes may be provided at a rim of the sensor area, wherein an interior space of the sensor area remains free and may be covered by one or more additional electrode materials. As will be outlined in further detail below, the additional electrode material preferably may be a transparent additional electrode material, such as a transparent metal and/or a transparent conductive oxide and/or, most preferably, a transparent conductive polymer.

Further preferred embodiments may refer to the photovoltaic material. Thus, the photovoltaic material of the transversal optical sensor may comprise at least one organic photovoltaic material. Thus, generally, the transversal optical sensor may be an organic photo detector. Preferably, the organic photo detector may be a dye-sensitized solar cell. The dye-sensitized solar cell preferably may be a solid dye-sensitized solar cell, comprising a layer setup embedded in between the first electrode and the second electrode, the layer setup comprising at least one n-semiconducting metal oxide, at least one dye, and at least one solid p- semiconducting organic material.

The at least one first electrode of the transversal optical sensor preferably is transparent. As used in the present invention, the term transparent generally refers to the fact that the intensity of light after transmission through the transparent object equals to or exceeds 10%, preferably 40% and, more preferably, 60% of the intensity of light before transmission through the transparent object. More preferably, the at least one first electrode of the transversal optical sensor may fully or partially be made of at least one transparent conductive oxide (TCO). As an example, indium-doped tin oxide (ITO) and/or fluorine-doped tin oxide (FTO) may be named. Further examples will be given below. Further, the at least one second electrode of the transversal optical sensor preferably may fully or partially be transparent. Thus, specifically, the at least one second electrode may comprise two or more partial electrodes and at least one additional electrode material contacting the two or more partial electrodes. The two or more partial electrodes may be intransparent. As an example, the two or more partial electrodes may fully or partially be made of a metal. Thus, the two or more partial electrodes preferably are located at a rim of the sensor area. The two or more partial electrodes, however, may electrically be connected by the at least one additional electrode material which, preferably, is transparent. Thus, the second electrode may comprise an intransparent rim having the two or more partial electrodes and a transparent inner area having the at least one transparent additional electrode material. More preferably, the at least one second electrode of the transversal optical sensor, such as the above-mentioned at least one additional electrode material, may fully or partially be made of at least one conductive polymer, preferably a transparent conductive polymer. As an example, conductive polymers having an electrical conductivity of at least 0.01 S/cm may be used, preferably of at least 0.1 S/cm or, more preferably, of at least 1 S/cm or even at least 10 S/cm or at least 100 S/cm. As an example, the at least one conductive polymer may be selected from the group consisting of: a poly-3,4-ethylenedioxythiophene (PEDOT), preferably PEDOT being electrically doped with at least one counter ion, more preferably PEDOT doped with sodium polystyrene sulfonate (PEDOT:PSS); a polyaniline (PANI); a polythiophene.

As outlined above, the conductive polymer may provide an electrical connection between the at least two partial electrodes. The conductive polymer may provide an Ohmic resistivity, allowing for determining the position of charge generation. Preferably, the conductive polymer provides an electric resistivity of 0.1 - 20 kQ between the partial electrodes, preferably an electric resistivity of 0.5 - 5.0 kQ and, more preferably, an electric resistivity of 1 .0 - 3.0 kQ.

Generally, as used herein, a conductive material may be a material which have a specific electrical resistance of less than 10 ⁴ , less than 1 0 ³ , less than 1 0 ² , or of less than 10 Qm.

Preferably, the conductive material has a specific electrical resistance of less than 10 ^_1 , less than 1 0 ^"2 , less than 10 ^"3 , less than 1 0 ^"5 , or less than 10 ^"6 Qm. Most preferably, the specific electrical resistance of the conductive material is less than 5 x 1 0 ^"7 Qm or is less than

1 x 1 0 ^"7 ΩΓΠ, particularly in the range of the specific electrical resistance of aluminum. As outlined above, optionally, at least one of the transversal optical sensor and the longitudinal optical sensor is a transparent optical sensor. Thus, the at least one transversal optical sensor may be a transparent transversal optical sensor and/or may comprise at least one transparent transversal optical sensor. Additionally or alternatively, the at least one longitudinal optical sensor may be a transparent longitudinal optical sensor and/or may comprise at least one transparent longitudinal optical sensor. In case a plurality of longitudinal optical sensors is provided, such as a stack of longitudinal optical sensors, preferably all longitudinal optical sensors of the plurality and/or the stack or all longitudinal optical sensors of the plurality and/or the stack but one longitudinal optical sensor are transparent. As an example, in case a stack of longitudinal optical sensors is provided, wherein the longitudinal optical sensors are arranged along the optical axis of the detector, preferably all longitudinal optical sensors but the last longitudinal optical sensor facing away from the object may be transparent longitudinal optical sensors. The last longitudinal optical sensor, i.e. the longitudinal optical sensor on the side of the stack facing away from the optical data carrier, may be a transparent longitudinal optical sensor or an intransparent longitudinal optical sensor. Exemplary embodiments will be given below.

In case at least one of the transversal optical sensor and the longitudinal optical sensor is a transparent optical sensor or comprises at least one transparent optical sensor, the light beam may pass through the transparent optical sensor before impinging on the other one of the transversal optical sensor and the longitudinal optical sensor. Thus, the light beam from the object may subsequently reach the transversal optical sensor and the longitudinal optical sensor or vice versa. Further embodiments refer to the relationship between the transversal optical sensor and the longitudinal optical sensor. Thus, in principle, the transversal optical sensor and the longitudinal optical sensor at least partially may be identical, as outlined above. In this context, reference may e.g. be made to the hybrid devices combining a transversal optical sensor and a longitudinal optical sensor as disclosed in European patent application number EP 14 196 942.8, filed on December 9, 2014, the full content of which is here with included by reference. Additionally or alternatively, reference may be made to European patent application number EP 14 186 792.9, filed on September 29, 2014, the full content of which is also included by reference. Alternatively, however, the transversal optical sensor and the longitudinal optical sensor at least partially may be independent optical sensors, such as independent photo detectors and, more preferably, independent DSCs or sDSCs, such as in a stacked

configuration.

As outlined above, the transversal optical sensor and the longitudinal optical sensor preferably may be stacked along the optical axis. Thus, a light beam travelling along the optical axis may both impinge on the transversal optical sensor and on the longitudinal optical sensor, preferably subsequently. Thus, the light beam may subsequently pass through the transversal optical sensor and the longitudinal optical sensor or vice versa. As outlined above, the at least one longitudinal sensor signal, given the same total power of the illumination by the light beam, is dependent on a beam cross-section of the light beam in the sensor region of the at least one longitudinal optical sensor. As used herein, the term beam cross-section generally refers to a lateral extension of the light beam or a light spot generated by the light beam at a specific location. In case a circular light spot is generated, a radius, a diameter or a Gaussian beam waist or twice the Gaussian beam waist may function as a measure of the beam cross-section. In case non-circular light-spots are generated, the cross- section may be determined in any other feasible way, such as by determining the cross-section of a circle having the same area as the non-circular light spot, which is also referred to as the equivalent beam cross-section.

Thus, given the same total power of the illumination of the sensor region by the light beam, a light beam having a first beam diameter or beam cross-section may generate a first longitudinal sensor signal, whereas a light beam having a second beam diameter or beam-cross section being different from the first beam diameter or beam cross-section generates a second longitudinal sensor signal being different from the first longitudinal sensor signal. Thus, by comparing the longitudinal sensor signals, an information or at least one item of information on the beam cross-section, specifically on the beam diameter, may be generated. For details of this effect, reference may be made to one or more of WO 2012/1 10924 A1 , US 2012/0206336 A1 , US 2014/0291480 A1 or WO 2014/097181 A1. Specifically in case one or more beam properties of the light beam propagating from the light source to the optical data carrier and from the optical data carrier to the at least one longitudinal optical sensor are known, at least one item of information regarding a position of the at least one optical data carrier may thus optionally be derived from a known relationship between the at least one longitudinal sensor signal and the position of the optical data carrier reflecting the light beam. The known relationship may be stored in the data reader as an algorithm and/or as one or more calibration curves. As an example, specifically for Gaussian beams, a relationship between a beam diameter or beam waist and a position of the optical data carrier may easily be derived by using the Gaussian relationship between the beam waist and a longitudinal coordinate.

Generally, the at least one longitudinal optical sensor may be designed in such a way that the at least one longitudinal sensor signal, given the same total power of the illumination, is dependent on a modulation frequency of a modulation of the illumination. Further details and exemplary embodiments will be given below. This property of frequency dependency is specifically provided in DSCs and, more preferably, in sDSCs. However, other types of optical sensors, preferably photo detectors and, more preferably, organic photo detectors may exhibit this effect. Further, as outlined above, the nonlinear behavior also occurs in other photosensitive devices such as photo conductors, both organic and inorganic. In this regard, reference may be made to European patent application number EP 15 153 215.7, filed on January 13, 2015.

Preferably, the transversal optical sensor and the longitudinal optical sensor both are thin film devices, having a layer setup of one or more layers including one or more electrodes and one or more photovoltaic materials, the layer setup having a thickness of preferably no more than 1 mm, more preferably of at most 500 μηη or even less. Thus, the sensor region of the transversal optical sensor and/or the sensor region of the longitudinal optical sensor preferably each may be or may comprise a sensor area, which may be formed by a surface of the respective device, wherein the surface may face towards the object or may face away from the optical data carrier. Hereby, it may further be feasible to arrange the at least one transversal optical sensor and the at least one longitudinal optical sensor in a way that some surfaces comprising the sensor regions may face towards the optical data carrier wherein other surfaces may face away from the optical data carrier. Such a kind of arrangement of the respective devices, which might be helpful to optimize the path of the light beam through the stack and/or to reduce reflections within the light path, may, for any reason or purpose, be implemented in an alternating manner, such as with one, two, three or more devices where the sensor regions may face towards the optical data carrier alternating with one, two, three or more other devices where the sensor regions may face away from the optical data carrier.

Preferably, the sensor region of the transversal optical sensor and/or the sensor region of the longitudinal optical sensor may be formed by one continuous sensor region, such as one continuous sensor area or sensor surface per device. Thus, preferably, the sensor region of the longitudinal optical sensor or, in case a plurality of longitudinal optical sensors is provided (such as a stack of longitudinal optical sensors), each sensor region of the longitudinal optical sensor, may be formed by exactly one continuous sensor region. The longitudinal sensor signal preferably is a uniform sensor signal for the entire sensor region of the longitudinal optical sensor or, in case a plurality of longitudinal optical sensors is provided, is a uniform sensor signal for each sensor region of each longitudinal optical sensor. The at least one transversal optical sensor and/or the at least one longitudinal optical sensor each, independently, may have a sensor region providing a sensitive area, also referred to as a sensor area, of at least 1 mm ² , preferably of at least 5 mm ² , such as a sensor area of 5 mm ² to 1000 cm ² , preferably a sensor area of 7 mm ² to 100 cm ² , more preferably a sensor area of 1 cm ² . The sensor area preferably has a rectangular geometry, such as a square geometry.

However, other geometries and/or sensor areas are feasible.

The longitudinal sensor signal preferably may be selected from the group consisting of a current (such as a photocurrent) and a voltage (such as a photo voltage). Similarly, the transversal sensor signal preferably may be selected from the group consisting of a current (such as a photocurrent) and a voltage (such as a photo voltage) or any signal derived thereof, such as a quotient of currents and/or voltages. Further, longitudinal sensor signal and/or the transversal sensor signal may be preprocessed, in order to derive refined sensor signals from raw sensor signals, such as by averaging and/or filtering.

Generally, the longitudinal optical sensor may comprise at least one semiconductor detector, in particular an organic semiconductor detector comprising at least one organic material, preferably an organic solar cell and particularly preferably a dye solar cell or dye-sensitized solar cell, in particular a solid dye solar cell or a solid dye-sensitized solar cell. Preferably, the longitudinal optical sensor is or comprises a DSC or sDSC. Thus, preferably, the longitudinal optical sensor comprises at least one first electrode, at least one n-semiconducting metal oxide, at least one dye, at least one p-semiconducting organic material, preferably a solid p- semiconducting organic material, and at least one second electrode. In a preferred

embodiment, the longitudinal optical sensor comprises at least one DSC or, more preferably, at least one sDSC. As outlined above, preferably, the at least one longitudinal optical sensor is a transparent longitudinal optical sensor or comprises at least one transparent longitudinal optical sensor. Thus, preferably, both the first electrode and the second electrode are transparent or, in case a plurality of longitudinal optical sensors is provided, at least one of the longitudinal optical sensors is designed such that both the first electrode and the second electrode are transparent.

As outlined above, in case a stack of longitudinal optical sensors is provided, preferably some or even all longitudinal optical sensors of the stack are transparent but the last longitudinal optical sensor of the stack. The last longitudinal optical sensor of the stack, i.e. the longitudinal optical sensor of the stack furthest away from the optical data carrier, may be transparent or intransparent. The stack may, besides the at least one transversal optical sensor and the at least one longitudinal optical sensor, comprise one or more further optical sensors which may function as one or more of a transversal optical sensor, a longitudinal optical sensor (also referred to as an imaging device) and an imaging sensor. Thus, it may be possible to locate an imaging device in the optical path of the light beam in a manner that the light beam travels through the stack of the transparent longitudinal optical sensors until it impinges on the imaging device. Thus, generally, the detector may further comprise at least one imaging device, i.e. a device capable of acquiring at least one image. The imaging device can be embodied in various ways. Thus, the imaging device can be for example part of the detector in a detector housing. The optional stack of at least two optical sensors, such as the stack comprising at least one longitudinal optical sensor and at least one transversal optical sensor, optionally may partially or fully be immersed in an oil, in a liquid and/or in a solid material in order to avoid and/or decrease reflections at interfaces. Hereby, the oil, the liquid, and/or the solid material may preferably be transparent, preferentially to a high degree, at least over a part of the ultraviolet, visible, and/or infrared spectral range. In a preferred embodiment, the solid material may be generated by inserting at least one curable substance into a region between at least two optical sensors and treating the curable substance with a treatment, such as by incident light, particularly with light within the ultraviolet range, and/or by an application of a temperature above or below room temperature, by which treatment the curable substance might be cured, preferentially by hardening the curable substance into the solid material. Alternatively, at least two different curable substances may be inserted into a region between at least two optical sensors, whereby the two different curable substances are selected in a manner that they begin to set into the solid material with or without the treatment as indicated above. However, further treatments and/or other procedures of providing the transparent solid material may be possible. Thus, at least one of the optical sensors of the stack may fully or partially be immersed in the oil and/or the liquid and/or covered with the solid material.

Alternatively or additionally, the region between the at least two optical sensors may be partially or fully filled with a substance, such as the oil, the liquid and/or the solid material. Hereby, the substance may preferably exhibit a refractive index with a value which may differ from that of the optical sensors adjoining to the substance on one or both sides of the region. However, inserting the additional substance in the regions may require the optical sensors within the stack to observe a minimum spacing between them. The present invention provides a plurality of advantages over known data readers. Thus, specifically, it is generally feasible to control the focal position of the light beam and the lateral position of the light beam on and/or in the optical data carrier simultaneously. As an example, using the above-mentioned FiP-effect allows to obtain the position on the photodiode or another type of light source and the distance from the light source in a single measurement. The sensor signals of the at least one longitudinal optical sensor and, optionally, of the at least one optional transversal optical sensor, can directly be used to tune a lens of the light source such as of the laser for focus correction. Since the optical system may generally be well defined and known, including the signal strength of the light source, a single FiP-sensor may be enough to detect the xyz position of the reflection of the light beam. This single FiP-sensor may be a combined xyz-FiP sensor, wherein one electrode is split into four partial electrodes in order to measure the xy-position, while the FiP-effect is used for the z-position. It shall be noted, however, that the at least one longitudinal optical sensor and the at least one transversal optical sensor may also be separated, as outlined above. Further, the present invention generally allows for a larger transversal measurement range than e.g. a quadrant detector.

Thus, generally, the present invention allows for a precise alignment of a light beam in a data reader, by using a simple and efficient sensor setup.

Overall, in the context of the present invention, the following embodiments are regarded as preferred. It shall be noted, however, that other embodiments are feasible. Embodiment 1 : A data reader for reading data from an optical data carrier, the data reader comprising at least one light source for generating at least one light beam, wherein the data reader is configured to direct the light beam onto the optical data carrier, wherein the data reader further comprises at least one beam alignment module, wherein the beam alignment module comprises:

- at least one longitudinal optical sensor, the longitudinal optical sensor being configured to detect the light beam or a part thereof after reflection by the optical data carrier, wherein the longitudinal optical sensor has at least one sensor region, wherein the longitudinal optical sensor is designed to generate at least one longitudinal sensor signal in a manner dependent on an illumination of the sensor region by the light beam, wherein the longitudinal sensor signal, given the same total power of the illumination, is dependent on a beam cross-section of a light spot generated by the light beam in the sensor region;

at least one control device configured to compare the longitudinal sensor signal with at least one predetermined longitudinal sensor signal and to generate at least one longitudinal control signal; and

- at least one beam positioning device configured to receive the longitudinal control signal and to modify a focal position of the light beam in a controlled fashion.

Embodiment 2: The data reader according to the preceding embodiment, wherein the control device is configured to generate the control signal in such a way that a focal position of the light beam is on the optical data carrier.

Embodiment 3: The data reader according to any one of the preceding embodiments, wherein the data reader further comprises at least one data carrier actuator for positioning the optical data carrier.

Embodiment 4: The data reader according to the preceding embodiment, wherein the data carrier actuator comprises at least one motor for rotating the optical data carrier.

Embodiment 5: The data reader according to any one of the preceding embodiments, wherein the data reader further comprises at least one receptacle configured to receive the optical data carrier. Embodiment 6: The data reader according to any one of the preceding embodiments, wherein the optical data carrier has a disk shape, preferably a circular disk shape.

Embodiment 7: The data reader according to any one of the preceding embodiments, wherein the beam positioning device comprises at least one movable lens and at least one lens positioning actuator configured to adjust one or more of a position or an orientation of the movable lens.

Embodiment 8: The data reader according to the preceding embodiment, wherein the lens positioning actuator comprises at least one electromagnetic actuator.

Embodiment 9: The data reader according to any one of the preceding embodiments, wherein the longitudinal sensor signal one of steadily rises or steadily decreases with decreasing cross- section of the light spot.

Embodiment 10: The data reader according to any one of the preceding embodiments, wherein the predetermined longitudinal sensor signal is predetermined such that a focal position of the light beam is located on or in the optical data carrier. Embodiment 1 1 : The data reader according to any one of the preceding embodiments, wherein the longitudinal optical sensor comprises at least one nonlinear photosensitive element.

Embodiment 12: The data reader according to the preceding embodiment, wherein the nonlinear photosensitive element comprises at least one of: a photoconductor having a nonlinear behavior, specifically one of an organic photoconductor, an inorganic photoconductor or a hybrid photoconductor; a photovoltaic element having a nonlinear behavior, specifically one of an organic photovoltaic element or an inorganic photovoltaic element; an organic solar cell, more specifically a dye-sensitized solar cell. Embodiment 13: The data reader according to any one of the preceding embodiments, wherein the longitudinal optical sensor comprises at least one first electrode, at least one n- semiconducting metal oxide, at least one dye, at least one p-semiconducting organic material, preferably a solid p-semiconducting organic material, and at least one second electrode. Embodiment 14: The data reader according to the preceding embodiment, wherein both the first electrode and the second electrode are transparent.

Embodiment 15: The data reader according to any one of the preceding embodiments, wherein the data reader comprises a plurality of longitudinal optical sensors, wherein the longitudinal optical sensors are stacked.

Embodiment 16: The data reader according to the preceding embodiment, wherein the longitudinal optical sensors are arranged such that the light beam illuminates all longitudinal optical sensors, wherein at least one longitudinal sensor signal is generated by each longitudinal optical sensor, wherein the data reader is adapted to normalize the longitudinal sensor signals independent from an intensity of the light beam. Embodiment 17: The data reader according to any of the two preceding embodiments, wherein a last longitudinal optical sensor is arranged in a manner that the light beam illuminates all other longitudinal optical sensors apart from the last longitudinal optical sensor, until the light beam impinges on the last longitudinal optical sensor, wherein the last longitudinal optical sensor is intransparent with respect to the light beam.

Embodiment 18: The data reader according to any one of the preceding embodiments, wherein the longitudinal optical sensor is transparent.

Embodiment 19: The data reader according to any one of the preceding embodiments, wherein the data reader further comprises:

at least one transversal optical sensor, the transversal optical sensor being configured to detect the light beam or a part thereof after reflection by the optical data carrier, the transversal optical sensor further being configured to determine a transversal position of the light beam or the part thereof the transversal position being a position in at least one dimension perpendicular an optical axis of the transversal optical sensor, the transversal optical sensor further being configured to generate at least one transversal sensor signal;

wherein the control device is further configured to compare the transversal sensor signal with at least one predetermined transversal sensor signal and to generate at least one transversal control signal;

wherein the beam positioning device is further configured to receive the transversal control signal and to modify a transversal position of a light spot generated by the light beam on or in the optical data carrier.

Embodiment 20: The data reader according to the preceding embodiment, wherein the transversal optical sensor comprises at least one photo detector having at least one first electrode, at least one second electrode and at least one photovoltaic material, wherein the photovoltaic material is embedded in between the first electrode and the second electrode, wherein the photovoltaic material is adapted to generate electric charges in response to an illumination of the photovoltaic material with light, wherein the second electrode is a split electrode having at least two partial electrodes, wherein the transversal optical sensor has a sensor region, wherein the at least one transversal sensor signal indicates a position of the light beam in the sensor region.

Embodiment 21 : The data reader according to the preceding embodiment, wherein electrical currents through the partial electrodes are dependent on a position of the light beam in the sensor region, wherein the transversal optical sensor is adapted to generate the transversal sensor signal in accordance with the electrical currents through the partial electrodes. Embodiment 22: The data reader according to the preceding embodiment, wherein the control device is configured to generate the transversal control signal in such a way that the electrical currents through the partial electrodes are equalized. Embodiment 23: The data reader according to any one of the two preceding embodiments, wherein the control device is configured to generate the transversal control signal in such a way that the light beam impinges on to the photovoltaic material right in the middle between the partial electrodes. Embodiment 24: The data reader according to any one of the three preceding embodiments, wherein the photo detector is a dye-sensitized solar cell.

Embodiment 25: The data reader according to any of the four preceding embodiments, wherein the first electrode at least partially is made of at least one transparent conductive oxide, wherein the second electrode at least partially is made of an electrically conductive polymer, preferably a transparent electrically conductive polymer.

Embodiment 26: The data reader according to any one of the seven preceding embodiments, wherein the transversal optical sensor is transparent.

Embodiment 27: The data reader according to any one of the eight preceding embodiments, wherein the transversal optical sensor and the longitudinal optical sensor are stacked along the optical axis such that a light beam travelling along an optical axis both impinges on the transversal optical sensor and on the longitudinal optical sensor.

Embodiment 28: The data reader according to any of the preceding embodiments, wherein the longitudinal optical sensor is furthermore designed in such a way that the longitudinal sensor signal, given the same total power of the illumination, is dependent on a modulation frequency of a modulation of the illumination.

Embodiment 29: The data reader according to the preceding embodiment, wherein the data reader further comprises at least one modulation device for modulating the light beam.

Embodiment 30: The data reader according to any one of the preceding embodiments, wherein the data reader further comprises at least one decoding module configured to decode information contained in the reflected light beam or a part thereof.

Embodiment 31 : A data reader system, comprising the data reader according to any one of the preceding embodiments and at least one optical data carrier.

Embodiment 32: A method for controlling a light beam in a data reader according to any one of the preceding embodiments, the method comprising the following steps: detecting the light beam or a part thereof after reflection by an optical data carrier and generating at least one longitudinal sensor signal in a manner dependent on an illumination of the sensor region of the longitudinal optical sensor by the light beam, wherein the longitudinal sensor signal, given the same total power of the illumination, is dependent on a beam cross- section of a light spot generated by the light beam in the sensor region;

comparing the longitudinal sensor signal with at least one predetermined longitudinal sensor signal and generating at least one longitudinal control signal; and

modifying a focal position of the light beam in accordance with the longitudinal control signal.

Embodiment 33: The method according to the preceding embodiment, wherein the data reader furthermore comprises the at least one transversal optical sensor, wherein the method further comprises:

detecting the light beam or a part thereof after reflection by the optical data carrier by using the transversal optical sensor and generating at least one transversal sensor signal; comparing the transversal sensor signal with at least one predetermined transversal sensor signal and generating at least one transversal control signal;

modifying a transversal position of a light spot generated by the light beam on or in the optical data carrier in accordance with the transversal control signal.

Brief description of the figures

Further optional details and features of the invention are evident from the description of preferred exemplary embodiments which follows in conjunction with the dependent claims. In this context, the particular features may be implemented alone or with several in combination. The invention is not restricted to the exemplary embodiments. The exemplary embodiments are shown schematically in the figures. Identical reference numerals in the individual figures refer to identical elements or elements with identical function, or elements which correspond to one another with regard to their functions.

Specifically, in the figures:

Figure 1 shows an exemplary embodiment of a data reader, a data reader system and a beam alignment module; and

Figure 2 shows an enlarged partial view of the beam alignment module of Figure 1.

Exemplary embodiments

Longitudinal optical sensor and transversal optical sensor As outlined in the general description above, a data reader according to the present invention may comprise at least one longitudinal optical sensor and, optionally, at least one transversal optical sensor. The longitudinal optical sensor and the transversal optical sensor may be embodied as separate devices, such as disclosed in Figures 1A, 1 B and 1 C of US

2014/0291480 A1 and WO 2014/097181 A1 . Consequently, for potential embodiments of the at least one longitudinal optical sensor, reference may e.g. be made to the embodiment of the longitudinal optical sensor shown in Figures 4A-4C of WO 2014/097181 A1 as well as to the corresponding description, and for potential embodiments of potential longitudinal sensor signals, reference may contain to Figures 5A-5E of WO 2014/097181 A1 as well as to the corresponding description. For potential embodiments of the at least one optional transversal optical sensor, embodied as a separate device and independent from the longitudinal optical sensor, reference may be made e.g. to the exemplary embodiments shown in Figures 2A and 2B of WO 2014/097181 A1 as well as to the corresponding description, and with regard to embodiments of transversal sensor signals such as photocurrents -i ₄ , reference may be made to Figures 3A-3D of WO 2014/097181 A1 as well as to the corresponding description. It shall be noted, however, that other embodiments are feasible.

Additionally or alternatively, the at least one optional transversal optical sensor may also be fully or partially integrated into or combined with the at least one longitudinal optical sensor, or, in case a plurality of longitudinal optical sensors is provided, with at least one of the longitudinal optical sensors. In this context, generally, reference may be made to European patent application number EP 14 196 942.8, filed on December 9, 2014, the full content of which is here with included by reference. Additionally or alternatively, reference may be made to

European patent application number EP 14 186 792.9, filed on September 29, 2014, the full content of which is also included by reference

In order to provide a simple example of a combined longitudinal optical sensor and transversal optical sensor, again, reference may be made to the setup shown in Figures "a-2B and 3A-3D as well as the corresponding description of WO 2014/097181 A1 . In addition to using the sensor shown therein as a transversal optical sensor, this optical sensor may also be used as a longitudinal optical sensor. For this purpose, the photocurrents -i ₄ may be used and combined in different ways, in order to provide transversal sensor signals and longitudinal sensor signals. As an example, the following sensor signals may be combined: - longitudinal sensor signal: z = ∑ ₌₁ i _n , transversal sensor signal, x-direction: x = (i ₄ — i ₃ )/ (i ₄ + i ₃ ), and transversal sensor signal, y-direction: y = (h - i ₂ )/ (h + ), with the nomenclature and definition of axes as given in WO 2014/097181 A1 . In order to provide at least one longitudinal control signal, signal z may be compared with at least one predetermined z signal, such as by using a first electronic comparator. In order to provide at least one transversal control signal for an x-direction, signal x may be compared with at least one predetermined x signal, such as by using a second electronic comparator. In order to provide at least one transversal control signal for a y-direction, signal y may be compared with at least one predetermined y signal, such as by using a third electronic comparator.

Data reader and data reader system In Figure 1 , a data reader system 1 10 is shown, comprising a data reader 1 12 and an optical data carrier 1 14 to be read out by the data reader 1 12. As an example, the optical data carrier 1 14 may be or may comprise a compact disc (CD) and/or a digital versatile disc (DVD).

The data reader 1 12 comprises at least one light source 1 16 for generating at least one light beam 1 18. The data reader 1 12 is configured to direct the light beam 1 18 onto the optical data carrier 1 14, preferably such that a focal position 120 of the light beam is located on or in the optical data carrier 1 14. The light beam 1 18 is fully or partially reflected by the optical data carrier 1 14 and/or by information modules contained therein, such as in information tracks on or in the optical data carrier 1 14. The reflected light beam or a part thereof, in this embodiment, is directed by a first beam-splitting device 122 onto a photo diode 124 or another type of photo detector. The photo diode 124 generates a readout signal 126 which is provided to a decoding module 128 adapted for demodulating the readout signal 126 and for retrieving information stored therein. In order to align the light beam 1 18 and the focal position 120 on or in the optical data carrier 1 14, the data reader 1 12 comprises an alignment module 130. The beam alignment module comprises at least one second beam-splitting device 132 adapted to split off a part of the light beam 1 18 returning from the optical data carrier 1 14, thereby creating a partial light beam 134 which is detected by at least one optical sensor 136. The at least one optical sensor 136 generates at least one sensor signal 138 which is provided to at least one control device 140 of the beam alignment module 130. The control device 140 is configured to generate at least one control signal 142 and to provide the control signal 142 to at least one beam positioning device 144 in the path of the light beam 1 18. The beam positioning device 144 is configured to receive the longitudinal control signal 142 and to modify the focal position 120 of the light beam in a controlled fashion, i.e. in response to the longitudinal control signal. For this purpose, the beam positioning device 144 may comprise at least one movable lens 146 and at least one lens positioning actuator 148 for controlling a position and/or an orientation of the movable lens 146. As symbolically depicted in Figure 1 , the focal position of the light beam 1 18 may be modified by the at least one movable lens 146 in various directions, such as in a z-direction parallel to the light beam 1 18 and/or in one or more directions perpendicular to the z-direction, denoted by x and y in Figure 1. It shall be noted that, in the schematic setup of the data reader 1 12 shown in Figure 1 , the optical sensor 136 of the beam alignment module 130 is separate and independent from the photo diode 124 for data readout. Still, as depicted by the optional data connection 150, the optical sensor 136 and the photo diode 124 may also fully or partially be combined, such that the first beam-splitting device 122 and the photo diode 124 may be omitted. Further, it shall be noted that, in the setup of Figure 1 , one and the same light beam 1 18 are used both for data readout and for alignment. Thus, as an example, the longitudinal optical sensor 158 discussed in further detail below with reference to Figure 2 may, additionally, be used for data readout and, thus, may fully or partially be combined with the photo diode 124. Therein, modulations in the signal provided by the longitudinal optical sensor 158, which are due to the reflections by the data modules of the optical data carrier 1 14, may be detected and demodulated and/or decrypted in order to retrieve that data encrypted therein. For this process, the FiP sensor properties and the FiP effect discussed above may be used, too. It is also feasible to use independent light beams, wherein at least one light beam is used for data readout and at least a second light beam is used for alignment. Various options are feasible.

The data reader 1 12, in the setup shown in Figure 1 , further comprises at least one data carrier actuator 152. In the exemplary embodiment shown in Figure 1 , the data carrier actuator 152, which is generally used for positioning the optical data carrier 1 14, comprises a motor 154, which, via at least one axle 156, is configured to rotate the optical data carrier 1 14. It shall be noted that, besides the at least one beam alignment module 130, further positioning systems may be present, such as one or more track controllers for keeping the focal position 120 on a predetermined track of data information modules within the optical data carrier. In Figure 2, a detailed view of the optical sensor 136 in Figure 1 is shown. As outlined above, the optical sensor 136 comprises at least one longitudinal optical sensor 158, such as defined in the preceding section. Further, optionally, the optical sensor 136 comprises at least one transversal optical sensor 160, as also defined in the preceding section. It shall be noted that in the schematic setup shown in Figure 2, the longitudinal optical sensor 158 and the transversal optical sensor 160 are designed as separate optical sensors. As outlined above, these optical sensors 158, 160 may also be designed as an integrated optical sensor combining both functionalities.

The at least one longitudinal optical sensor 158 creates at least one longitudinal sensor signal 162, in Figure 2 symbolically denoted by z. Similarly, the transversal optical sensor 160 comprises at least one transversal sensor signal. In the embodiment shown in Figure 2, two transversal sensor signals 164, 166 are generated, according to the coordinate system shown in Figure 1 . It shall be noted, however, that other coordinate systems are feasible. The longitudinal sensor signal 162 and the transversal sensor signals 164, 166 each are provided to the control device 140. The control device 140, in the exemplary embodiment shown in Figure 2, comprises three comparators 168, 170, 172. Thereof, comparator 168 compares the transversal sensor signal 164 (x-signal) with at least one predetermined transversal sensor signal x _p . Similarly, comparator 170 compares the second transversal sensor signal 166 with at least one predetermined transversal sensor signal y _p . Consequently, transversal control signals c _x and c _y (reference number 174 and 176) are generated and may be provided to the at least one lens positioning actuator 148. As an example, the at least one lens positioning actuator 148 may be or may comprise at least one stage, wherein the control signals Cx, Cy may be used for controlling the stage.

Similarly, the z-comparator 172 is configured to compare the longitudinal sensor signal 162 with at least one predetermined longitudinal sensor signal z _p and to generate at least one

longitudinal control signal 178. The longitudinal control signal 168, as an example, may also be provide to the at least one lens positioning actuator 148, such as for shifting the movable lens 146 along the z-axis of the setup in Figure 1 , which may also function as an optical axis.

List of reference numbers

1 10 data reader system

1 12 data reader

1 14 optical data carrier

116 light source

1 18 light beam

120 focal position

122 first beam-splitting device

124 photo diode

126 readout signal

128 decoding module

130 beam alignment module

132 second beam splitting device

134 partial light beam

136 optical sensor

138 sensor signal

140 control device

142 control signal

144 beam positioning device

146 movable lens

148 lens positioning actuator

150 data connection

152 data carrier actuator

154 motor

156 axle

158 longitudinal optical sensor

160 transversal optical sensor

162 longitudinal sensor signal z

164 transversal sensor signal x

166 transversal sensor signal y

168 comparator x

170 comparator y

172 comparator z

174 transversal control signal c _x

176 transversal control signal c _y

178 longitudinal control signal c _z