FIELD

The invention relates to acoustic transducing apparatus and method. BACKGROUND

User interfacing and interaction technologies are used in communication between a person and a device. A keyboard and a screen are at the moment the most usual user interfaces. Additionally, optical imagers are mainly used for three-dimensional (3D) gesture recognition, and for eye tracking optical imaging is currently the only available solution.

With the emerging of more intuitive computing devices, e.g. smart handsets, smart TV, tablet, head mounted display, gaming device and so on, new user interfacing and interaction technologies are strongly and urgently needed to improve users' experience towards immersive environment or augmented reality, in which 3D gesture recognition and eye tracking are accepted to be important enabling technologies. Hence, there is a need to improve the measurements.

BRIEF DESCRIPTION

The present invention seeks to provide an improvement in interfacing.

According to an aspect of the present invention, there is provided an acoustic transducing apparatus as specified in claim 1.

According to another aspect of the present invention, there is provided an eyewear in claim 9.

According to another aspect of the present invention, there is provided screen of a display in claim 10.

According to another aspect of the present invention, there is provided an acoustic transducing method in claim 11.

The invention has advantages. The visibly transparent transducing structure is compact and it is possible to apply it on an eyewear or a screen of a display.

LIST OF DRAWINGS Example embodiments of the present invention are described below, by way of example only, with reference to the accompanying drawings, in which

Figure 1 illustrates an example of a visually transparent acoustic transducing structure;

Figure 2 illustrates an example of a transducing apparatus which is based on capacitive effect;

Figure 3A illustrates an example of a transducing apparatus which is based on piezoelectric effect;

Figure 3B illustrates another example of the piezoelectric transducing apparatus;

Figure 4A illustrates an example of a transducing apparatus for deriving information about an eye;

Figure 4B illustrates another example of the transducing apparatus for deriving information about the eye;

Figure 5 illustrates an example of a transducing apparatus for deriving information about a hand and/or finger;

Figure 6 illustrates an example of an eyewear with the transducing apparatus;

Figure 7 illustrates an example of a processing unit;

Figure 8A illustrates an example of a phase in manufacturing a transducing structure;

Figure 8B illustrates an example of another phase in manufacturing the transducing structure;

Figure 8C illustrates an example of a further phase in manufacturing the transducing structure;

Figure 9A illustrates an example of a phase in a different manufacturing method of a transducing structure;

Figure 9B illustrates an example of another phase in the different manufacturing method of the transducing structure; Figure 10 illustrates an example of a flow chart of an acoustic transducing method; and

Figure 11 illustrates of an example of a flow chart of a method of manufacturing an acoustic transducing structure. DESCRIPTION OF EMBODIMENTS

The following embodiments are only examples. Although the specification may refer to "an" embodiment in several locations, this does not necessarily mean that each such reference is to the same embodiment(s), or that the feature only applies to a single embodiment. Single features of different embodiments may also be combined to provide other embodiments. Furthermore, words "comprising" and "including" should be understood as not limiting the described embodiments to consist of only those features that have been mentioned and such embodiments may contain also features/structures that have not been specifically mentioned.

It should be noted that while Figures illustrate various embodiments, they are simplified diagrams that only show some structures and/or functional entities. The connections shown in the Figures may refer to logical or physical connections. It is apparent to a person skilled in the art that the described apparatus may also comprise other functions and structures than those described in Figures and text. It should be appreciated that details of some functions, structures, and the signalling used for measurement and/or controlling may be irrelevant to the actual invention. Therefore, they need not be discussed in more detail here.

Figure 1 illustrates an example of a visually transparent acoustic transducing structure 102. The visually transparent acoustic transducing structure 102 comprises: a visually transparent substrate 101; a first electric conductor 104 disposed on the visually transparent substrate 101; a membrane 108 disposed on the first electric conductor 104, the membrane 108 having a visually transparent acoustically active part 120 and the first electric conductor 104 having a portion extending into the membrane 108; a cavity 110 formed between the visually transparent acoustically active part 120 and the first electric conductor 104; and a second electric conductor 104' disposed on the membrane 108 and having a portion electrically coupled to the visually transparent acoustically active part 120 and extending above the cavity 110, the visually transparent acoustically active part 120 being further electrically coupled to the first electric conductor 104 via the portion extending into the membrane 108.

Visually transparent means the visible optical radiation passes through the acoustic transducing structure 100. Visible optical radiation refers to electromagnetic radiation which can be seen with the human eye. The visible optical radiation may be determined to have at least a part of a wavelength range about 380 nm to 700 nm. The acoustic transducing structure 100 may be formed of layers. The thickness of layers may vary from less than a micrometer to a few millimeters without limiting to this range. The visually transparent acoustic transducing structure 100 comprises a substrate 101, visually transparent first and second electric conductors 104, 104', and a visually transparent membrane 108. The visually transparent membrane 108 may at least partly be an electric insulator. However, the visually transparent membrane 108 may also comprise electrically conducting sections.

The substrate 101 may comprise glass, quartz, polymer, such as plastic, or the like. The visually transparent membrane 108 comprises at least one layer. If the visually transparent membrane 108 comprises more than one layer, all layers may at least partly be electrically insulating. Alternatively, at least one layer may be electrically conductive and at least one layer may be electrically insulating. In any case, the visually transparent membrane 108 forms an electrical insulation between the electric conductors 104, 104' in order to avoid an electrical short circuit.

In Figure 1, the visually transparent acoustic membrane 108 comprises two layers which are separated by a dashed line. The visually transparent membrane 108 may comprise, for example, zinc oxide (ZnO), aluminium oxide (AI2O3), silicon nitride (S13N4), silicon dioxide (S1O2), Silicon Carbide (SiC), Diamond, Diamond like carbon (DLC), fused silica or the like. The visually transparent acoustic transducing structure 100 also comprises a cavity 110 between the visually transparent acoustic membrane 108 and the first electric conductor 104. The cavity 110 may be located in the visually transparent acoustic membrane 108. The cavity 110 is also located between the visually transparent first and the second electric conductors 104, 104'.

The first visually transparent electric conductor 104 is mounted or fabricated on the visually transparent substrate 101. Both the first and second visually transparent electric conductors 104, 104' are in contact with the acoustic membrane 108. Particularly, an acoustically active part 120 of the membrane 108 which is over the cavity 100 may comprise electrically conductive material 122 which has an electric coupling with the second electric conductor 104'. In an embodiment, the electrically conductive material 122 may be made of the same material as the second electric conductor 104'. In an embodiment, the electrically conductive material 122 may be a part of the second electric conductor 104'. In Figure 1, the electrically conducting material 122 is on the membrane 108 which is over the cavity 110. In general, the electrically conductive material 122 may be on either side of the membrane 108 or it may be a continuous part of the membrane 108 over the cavity 110. The electrically conductive material 122 on the part 120 of the membrane 108 results in electroacoustic activity which may be utilized as a visually transparent acoustic transducer.

The visually transparent electric conductors 104, 104' may comprise indium tin oxide (ITO) or other transparent conductive oxides (TCOs), for example. The visually transparent electric conductors 104, 104' may also comprise titanium nitride (TiN). The visually transparent electric conductors 104, 104' may alternatively or additionally comprise conducting polymers, metal grids, carbon nanotubes, graphene, ultra-thin metal films, metal nanowire-based electrodes, free-standing metallic nanotrough network or the like. The cavity 110 allows the visually transparent acoustic membrane 108 to vibrate over the cavity 110 which, in turn, enables the visually transparent acoustic transducing structure 100 to receive and transmit acoustic signals and convert them into an electric form. Figure 2 illustrates a general example of a transducing apparatus 100 which comprises a plurality of visually transparent acoustic transducing structures 102 in a two-dimensional array. Alternatively, the plurality of visually transparent acoustic transducing structures 102 may also be arranged in one- dimensional array (row). The plurality of transducing structures 102 receive an acoustic signal and convert the acoustic signal into an electric signal. The acoustic signal may be an ultrasound signal. Alternatively or additionally, the acoustic signal may be an audio signal. An ultrasound signal has sound the frequency of which is greater than an assumed upper limit of human hearing. An ultrasound signal sound may also be defined as sound the frequency of which is greater than 20,000 Hz. An audio signal is sound which has frequencies below the upper limit of human hearing. It may also be defined that an audio signal has frequencies in a frequency range of about 20 to 20,000 Hz.

The visually transparent electric conductors 104, 104' of transducing apparatus 100 lead operational electric power to the plurality of the acoustic transducing structures 102 and output the electronic signal from the plurality of acoustic transducing structures 102.

In an embodiment, the operation of the visually transparent acoustic transducing structures 102 may be based on capacitance between the first and second electric conductors 104, 104' at the cavity 110. When the operational electric power has been applied to the first and second electric conductors 104, 104', the acoustic signal from the environment causes vibration in the membrane 108 over the cavity 110 which, in turn, causes corresponding changes in the capacitance between the first and second electric conductors 104, 104'. The changes in the capacitance provide a corresponding electric signal into the first and second electric conductors 104, 104' which carry the signal to further processing. Figure 2 also shows an electric power source 200 and a signal processing unit 202 coupled with the electric conductors 104, 104'. The electric power source 200 and the signal processing unit 202 may be coupled with the electric conductors 104, 104' through one or more connectors 106. In an embodiment an example of which is illustrated in Figure 3A, the operation of the visually transparent acoustic transducing structures 102 may be based on piezoelectric effect. In an embodiment, the part 120 of the visually transparent membrane 108 may comprise piezoelectric material 300 at or over the cavity 110. The piezoelectric material 300, which is electroacoustically active material, is in electric contact with the visually transparent electric conductors 104, 104' in a vertical direction and thus receives operational power from the visually transparent electric conductors 104, 104'. The piezoelectric material 300 may be partly inside the cavity 110. In this case, at least one section of the membrane 108 may be replaced by the first electric conductor 104. When the operational electric power has been applied to the first and second electric conductors 104, 104', the acoustic signal from the environment causes vibration in the membrane 108 and the piezoelectric material 300 at or over the cavity 110 which, in turn, causes corresponding changes in the piezoelectric material 300 between the first and second electric conductors 104, 104'. The changes in the piezoelectric material 300 provide a corresponding electric signal into the first and second electric conductors 104, 104' which carry the signal to further processing. The piezoelectric material 300 of the membrane 108 results in electroacoustic activity which may be utilized as a visually transparent acoustic transducer.

The cavity 110 enhances the acoustic operation of the acoustic transducing structures 102. The cavity 110 also directs the acoustic beam of the acoustic transducing structures 102.

In an embodiment an example of which is illustrated in Figure 3B, the piezoelectric material 300 may be contacted with the electric conductors 104, 104' from opposite sides in a lateral direction.

In an embodiment, the plurality of the acoustic transducing structures 102 receives an audio frequency signal in an electric form from the signal processing unit 202 through visually transparent electric conductors 104 and outputs a corresponding audio signal on the basis of the audio frequency signal in the electric form. The audio signal can be heard by the user. In an embodiment, the plurality of the acoustic transducing structures 102 may detect pressure applied thereto. In an embodiment, the plurality of the acoustic transducing structures 102 may detect air pressure which can be used for altimeter, for example.

In an embodiment, the plurality of the acoustic transducing structures

102 may detect pressure caused by a touch on the acoustic transducing structures 102. An array of the acoustic transducing structures 102 may act as haptic interface, and the transducing apparatus 100 may be used as a touch user interface (TUI).

In an embodiment, the plurality of acoustic transducing structures 102 of the acoustic transducing apparatus 100 may receive an audio frequency signal in an electric form from the signal processing unit 200 through the visually transparent electric conductors 104, and output audio transmission on the basis of the received audio frequency signal. The audio signal may be directed to a specific direction. The audio signal may be directed towards a person.

In an embodiment, a transmission or reception beam of the transducing apparatus 100 with a plurality of transducing structures 102 may be directed by beam forming and steering. The acoustic beam may be formed and steered by phasing the acoustic signals in the electric form fed to or received from each of the plurality of transducing structures 102 in a suitable manner. Thus, the acoustic signals may be received from or sent to a desired direction. The beam width in a solid angle may be controlled by distance between the plurality of transducing structures 102. To avoid large side lobes, the distance d between the plurality of transducing structures 102 should be d ≤ λ/2, where λ is the wavelength of the acoustic signal in the air. A large aperture of the transducing apparatus increases resolution: Θ ¾ 2.78 /(i½d), where N is the number of the transducing structures 102, π is about 3.1415926, d is the distance between adjacent transducing structures 102.

In an embodiment an example of which is illustrated in Figures 4A and 4B, direction of gaze and/or movement of an eye 400 is detected. The arrow shows the direction of the eye 400. The plurality of acoustic transducing structures 102 of the acoustic transducing apparatus 100 may receive an ultrasound frequency signal in an electric form from the signal processing unit 200 through the visually transparent electric conductors 104, and output ultrasound transmission on the basis of the received ultrasound frequency signal towards an eye of a person. Alternatively, the acoustic signal may also come from other source. The plurality of acoustic transducing structures 102 may then detect reflection of the ultrasound transmission from the eye. The signal processing unit 202 may receive the electronic signal converted from the received reflection of the ultrasound transmission, and the signal processing unit 202 may derive information about the eye of the person on the basis of the electronic signal.

A contour of the eye 400 may be determined on the basis of the reflection to the plurality of acoustic transducing structures 102 on the basis of time-of-flight between the ultrasound transmission and the reception of the reflection. Because the curvature of the eye 400 varies in different parts of the eye 400, a position of the eye 400 and the direction of gaze may be determined. In a similar manner, movement of the eye 400 may be tracked on the basis of a plurality of determined positions of the eye 400. The position of the eye 400 determines also the direction of the gaze of the eye 400.

In an embodiment examples of which are illustrated in Figures 4A, 4B and 5, the signal processing unit 202 may derive position related information about a part of a body of a person. Thus, the signal processing unit 202 may derive a position or movement of at least one of the following: an eye 400, a hand 500 and a finger 502 of the person. The information may be derived in a similar manner as described in association with Figures 4A and 4B. In a similar manner, movement of these body parts 400, 500, 502 may be tracked on the basis of a plurality of determined positions of the body parts 400, 500, 502. A detection of a position or movement of a whole body is also possible in a manner corresponding to detection of the eye 400 and the hand 500.

In general, the plurality of acoustic transducing structures 102 may then detect reflection of the ultrasound transmission from a part of the body of the person. The signal processing unit 202 may receive the electronic signal converted from the received reflection of the ultrasound transmission, and the signal processing unit 202 may derive information about the part of the body of the person on the basis of the electronic signal. Ultrasound technology is preferable over optical imagers because it requires less data processing, lower operational power. Additionally, a larger field of view can be achieved with less ambient dependence, e.g. working in darkness.

In general, the plurality of acoustic transducing structures 102 may receive an ultrasound frequency signal in an electric form through the visually transparent electric conductors 104, and output ultrasound transmission on the basis of the received ultrasound frequency signal towards a part of a body of a person.

In an embodiment, the ultrasound frequency signal may be scanned over the plurality of acoustic transducing structures 102 one by one. Then each of the acoustic transducing structure 102 may transmit at different moments. Correspondingly, each of the acoustic transducing structures 102 is configured to receive the reflection of the acoustic transmission at different moments which are synchronized with the transmission of the same acoustic transducing structure 102. In this manner, the reflections may be distinguished on the basis of time division modulation (TDM) in the signal processing unit 202.

In an embodiment, the scan may also be achieved by transmitting from one or multiple transducing structures 102 while receiving from multiple transducing structures 102 without beam forming and steering.

In an embodiment, each of the acoustic transducing structure 102 may transmit at the same time using different frequencies. Then the reflections may be distinguished on the basis of frequency division modulation (FDM) in the signal processing unit 202.

In an embodiment, each of the acoustic transducing structure 102 may transmit at the same time or at a different time using different coding. Then the reflections may be distinguished on the basis of code division modulation (CDM) in the signal processing unit 202. In an embodiment an example of which is illustrated in Figure 6, the transducing apparatus 100 may be an eyewear 600 which comprises a plurality of visually transparent acoustic transducing structures 102. The material of a lens 602 of the eyewear 600 may be the substrate 101. In this manner, a more efficient eye tracking solution can be achieved for head mounted devices. The eyewear 600 may refer to spectacles, sunglasses, goggles or contact lenses, for example. In this embodiment, the power requirement is low and no light source is needed. The transducing apparatus is compact.

In an embodiment an example of which is similar to that illustrated in Figure 2, the transducing apparatus 100 may be a screen of a display. The material of a screen of the display may be the substrate 101. In this embodiment, the transducing apparatus is compact but still the solution fits large and small screens. The screen may be framed or frameless. The resolution and accuracy is high (higher than in the case when the transducing structures are only in the frames). The distance between any two transducing structures which are next to each other is small. A lot of transducing structures may be packed in the area of interest.

In an embodiment an example of which is illustrated in Figure 7, the signal processing unit 202 comprises one or more processors 700 and one or more memories 702. The one or more memories 702 may include also a computer program code. The one or more memories 702 and the computer program code may, with the one or more processors 700, cause the transducing apparatus 100 at least to derive the information about the part of the body of the person on the basis of the electronic signal converted from the received acoustic reflection, the signal processing unit 202 may control the whole operation of the transducing apparatus 100.

Below is a table showing some examples of indicative system parameters of the transducing apparatus.

Table 1, Parameters

Parameter Gesture Eye

footprint 2cm x 2cm 2cm x 2cm central frequency 200 kHz 2 MHz working distance 5 to 50 cm 7 to 10 mm

dynamic range 90 dB 60 dB

pitch size (λ/2) 850 μιη 85 μιτι

fractional bandwidth 10 % 20 %

distance resolution 5 mm 200 μιη

The distance resolution R may be expressed as R = /(4BW%), where BW is fractional bandwidth.

Figures 8A to 8C illustrate a manufacturing procedure of the transducing apparatus 100. When layers of the first visually transparent electric conductors 104 and the visually transparent membrane 108 have been formed on the substrate 101, a location for a sacrificial release 110' is determined in Figure 8A. In Figure 8B, a tiny hole may be made to the transparent membrane 108 at a location of the location for a sacrificial release 110' and the sacrificial release 110' of the membrane 108 may be removed. The material of the sacrificial release 110' may be silicon dioxide (Si0 ₂ ), polymer, silicon (SI), for example. The removal may be performed using etching or the like. As shown in Figure 8C, the second visually transparent electrodes 104' are formed on the membrane 108 over the cavity 110 which corresponds to the removed sacrificial release 110'. Also as shown in Figure 8C, a layer of the membrane 108 which is on the top of the layered structure may further be covered by a visually transparent seal material 116. The visually transparent seal material 116 may comprise silicon dioxide (Si0 ₂ ), parylene, or other polymers, for example.

Figure 9A to 9B illustrate another manufacturing procedure of the transducing apparatus 100. When layers of the first visually transparent electric conductors 104 and the visually transparent membrane 108 have been formed on the substrate 101, the sacrificial release 110' has been removed from the visually transparent membrane 108 which is on the top of the layered structure. The removal of the sacrificial release 110' has resulted in the cavity 110. Figure 9A shows the layered structure where the sacrificial release 110' has been removed. The removal may have been performed using etching or the like. The layer of a membrane 108 may be laid over the cavity 110 and on the membrane 108 which is already on the top of the layered structure. The membrane 108 which is to be laid over the cavity 110 may be attached to a second substrate 900 which is used to treat and move the membrane 108 as shown in Figure 9B. When the membrane 108 is moved over the cavity 110, the membrane 108 is released from the second substrate 900 and the membrane 108 remains on the top of the layered structure. After that the process may continue as shown in Figure 8C.

Figure 10 is a flow chart of an example of an acoustic transducing method. In step 1000, an acoustic signal is received from the environment on a basis of its interaction with an acoustic membrane 108 of an acoustic transducing structure 102, the membrane 108 being disposed on a first electric conductor 104, and having a visually transparent acoustically active part 120, the first electric conductor 104 having a portion extending into the membrane 108, the visually transparent acoustically active part 120 being further electrically coupled to the first electric conductor 104 via the portion extending into the membrane 108; the acoustic transducing structure 102 comprising a cavity 110 between the visually transparent acoustically active part 120 and the visually transparent first electrode 104, and the acoustic transducing structure 102 comprising a second electric conductor 104' disposed on the membrane 108 and having a portion electrically coupled to the visually transparent acoustically active part 120 and extending above the cavity 110. In step 1002, operational electric power is lead to the acoustic transducing structure 102 by the visually transparent first and second electric conductors 104, 104' which are in contact with the acoustic membrane 108. In step 1004, the acoustic signal received from the environment is converted into an electric signal by the acoustic transducing structure 102. In step 1006, the electronic signal is output from the acoustic transducing structure 102 through the electric conductors 104, 104'.

Figure 11 is a flow chart of an example of a manufacturing an acoustic transducing structure. In step 1100, a first layer of visually transparent electric conductor 104 is formed on a substrate 101. In step 1102, at least one layer of visually transparent acoustic membrane 108 is formed on the first visually transparent electrode 104. In step 1004, a cavity 110 is formed between the at least one visually transparent acoustic membrane 108 and the first electric conductor 104. In step 1006, a layer of a second visually transparent electric conductor 104' is formed in contact with the visually transparent acoustic membrane 108.

The transducing apparatus 100 may find use in on-screen 3D gesture recognition, on-spectacle eye tracking and/or on-screen audio projection, for example.

The transparent ultrasonic transducers (TUTs) built on screen may detect and/or scan the 3D space for gesture recognition and high resolution 3D object tracking by transmitting and receiving ultrasonic signals. Such an application may be used for user interfacing and 3D virtual reality, for example.

On-spectacle transparent ultrasonic transducers may track blink, eye movement, eye activity, which may be used for user interfacing or monitoring. A possible application may be to increase driver safety in traffic, for example. By tracking both eyes of a user it is possible to recognize long range gaze of a user (e.g. on a large TV in front), and thus provide user interfacing and interaction.

The transparent ultrasonic transducers may be built on the front side of the spectacles which may then work as a touchless input panel using gesture recognition, for example.

The transparent ultrasonic transducers may be built on the top of a screen for forming on-screen audio projection. The same type of transducers may also work for user tracking and interfacing for providing private audio with real- time and active feedback. The audio projection together with user tracking and interfacing may avoid generation of noise to ambient.

Transparent ultrasonic transducers may be piezoelectric micro- machined ultrasonic transducers (PMUT) or capacitive micro-machined ultrasonic transducers (CMUT). The transparent ultrasonic transducers may be integrated with (transparent) thin film transistors (TFTs) which may be uses as a base for liquid crystal and organic light emitting diode displays, to provide onscreen front-end circuits i.e. transmitter and receiver.

The method of deriving position related information about the part of the body of the person on the basis of the electronic signal may be implemented as a logic circuit solution or computer program.

The control of the transducing apparatus 100 may also be implemented as a logic circuit solution or computer program.

The computer program may be placed on a computer program distribution means for the distribution thereof. The computer program distribution means is readable by a data processing device, and it encodes the computer program commands, carries out the required operations and optionally controls the processes.

The computer program may be distributed using a distribution medium which may be any medium readable by the signal processing unit 202. The medium may be a program storage medium, a memory, a software distribution package, or a compressed software package. In some cases, the distribution may be performed using at least one of the following: a near field communication signal, a short distance signal, and a telecommunications signal.

It will be obvious to a person skilled in the art that, as the technology advances, the inventive concept can be implemented in various ways. The invention and its embodiments are not limited to the examples described above but may vary within the scope of the claims.