This invention relates to systems for projecting light, e.g. images onto a target surface and detecting light emitted from the surface.

Figs, la-lf show a known so-called "semantic lighting" system comprising a projector 1 for projecting an image onto a target surface 2 such as a table top. A detector 3 such as a digital camera is arranged to receive light emitted (e.g. reflected) from the target surface. A processor 4 receives signals from the detector 3 which represent the light received from the target surface, indicating characteristics of the target surface and of the image projected onto the target surface. The processor is arranged to modify the image responsive to the signals from the detector. In the illustrated example, the projector 1 is arranged to project a moving image representing a series of spots 5 which move across the target surface (Figs, la, lb). The processor detects an interruption such as a physical object 6 in the ta get surface and correlates the position of the interruption with the position of the moving spots (Fig. lc). The processor modifies the image so that the spots move around the obstacle (Figs. Id, le, If).

Such systems may be used for example for playing a game in which a static image such as a chess board or a deck of playing cards is projected onto a target surface. Physical entities, e.g. physical chess pieces or indicia, may also be present on the target surface. The processor processes the signals received by the detector using a suitable algorithm as known in the art to identify when the user interacts with a physical or virtual entity on the target surface , for example, by touching a playing card or a chess piece represented by a predefined element of the image. The processor modifies the projected image to represent a predefined action corresponding to the user's movement on the target surface; for example, by flipping over the card, or moving the card, or moving the chess piece to the indicated square on the board.

In order to ensure that the user can interact with the image projected onto a two dimensional (2D) target surface without interrupting the light from the projector and losing the image, the projector and detector may be arranged in defined positions relative to the user or at a shallow angle relative to the surface. More than one projector and detector may also be arranged to view the surface simultaneously. However, it is more difficult to use such systems on a three dimensional (3D) target surface, which can distort the image and make it more difficult to correlate the projected and detected image content so as to identify user interaction with a particular element of the image.

The human body presents a 3D target surface which may be irradiated with a laser or other light source in various procedures. For example, laser light may be used for the removal of tattoos.

In fluorescence-guided surgery a fluorescent composition is introduced into the body and irradiated with laser or LED light. The fluorescent signal is detected so that the composition acts as a marker for the target tissues.

Where only limited radiant intensity is required, e.g. for diagnostic procedures or laparoscopic fluorescence-guided surgery, it is known to use a camera with a ring of LEDs surrounding the lens, as described in van Driel et al, Characterization and Evaluation of the Artemis Camera for Fluorescence-Guided Cancer Surgery, Molecular Imaging and Biology, June 2015, Volume 17, Issue 3, pp 413-423

(available at https://link.springer.com/article/10.1007%2Fsll307-014-0799- z)

In photodynamic therapy for the treatment of skin cancers the light source may comprise an array of light emitting diodes (LEDs) mounted on a support which may be shaped to direct the light over the affected body part. A therapeutic composition comprising a photosensitizing agent is applied to the skin surface and activated by irradiation with light at a specified wavelength. A fluorescent agent may be incorporated into the composition so that the clinician can observe the emitted light to determine when its therapeutic activity is exhausted. Since substantial power may be required to generate the required radiant intensity over the target surface area in the target spectral band, the light source may be heavy and somewhat cumbersome to manoeuvre into the correct position, and may become undesirably warm in use. For procedures requiring both a light emitter and a detector or camera, or where several units are required to surround a target body part, the array of equipment can clutter the treatment environment and impede the clinician's access to the target site. it is a general object of the present invention in view of the abovementioned problems to more conveniently or effectively project and detect light or images on a target 2D or 3D surface.

Accordingly in its various aspects the invention provides an apparatus and a method as defined in the claims. In a first aspect, an apparatus for projecting and detecting light on a target surface comprises a light source; a light emitter for directing light from the light source onto the target surface; and a detector for detecting light from the target surface. The light emitter comprises at least first and second lenses and a reflector. The light emitter is arranged so that the light from the light source passes through the first lens to the reflector and then from the reflector through the second lens to the target surface, said light from the light source leaving the second lens along a projection axis, and the light from the target surface entering the second lens along the projection axis passes through the second lens to the detector.

The apparatus may include a processor, wherein the apparatus is arranged to project an image onto the target surface, and the processor is arranged to receive a signal from the detector representing the light received from the target surface and to identify, by said signal, a spatial coincidence between a predefined element of the image and a physical feature at the target surface. The processor may be arranged to modify said predefined element of the image responsive to identifying, by said signal, a spatial coincidence between said predefined element and a physical feature at the target surface, for example, to provide a virtual user interface such as a chessboard.

The novel apparatus combines projection and detection of light along a common axis, optionally with a steerable beam, providing a more compact and convenient arrangement with more reliable correlation between the projected and detected image, particularly on 3D surfaces, when compared with prior art systems in which the projection and detection axes are not aligned. In a second aspect, a method and apparatus are provided for projecting and detecting light on a target surface by means of a processor; a light source; at least one waveguide; a light emitter for directing light from the light source onto the target surface, the light emitter comprising at least a lens; and a detector for detecting light from or incident on the target surface. The light emitter is arranged so that the light from the light source passes through the at least one waveguide to the lens and then through the lens to the target surface, said light from the light source leaving the lens along a projection axis. The light source comprises a plurality of light emitting elements, each of the light emitting elements being individually controllable by the processor to adjust a radiant intensity of its emitted light. The processor is arranged to receive a signal from the detector representing the light received from or incident on the target surface and to adjust the radiant intensity of the light emitted by each of the light emitting elements responsive to the signal to obtain an even radiant intensity over the target surface.

By delivering the light from all of the light emitting elements along a common projection axis, the radiant energy is delivered in a more compact and convenient arrangement which provides better access to the target surface, for example, during light based therapy.

Optionally, the light emitter and the detector may be arranged so that the light from the target surface entering the lens along the projection axis passes through the lens to the detector, in which case the light emitter may be arranged generally as in the first aspect. The detector may obtain a 3D contour of the target surface, e.g. by scanning the surface, before adjusting the light emitting elements.

More particular objects and advantages, relating for example to applications in semantic lighting or in therapy will be understood from the various illustrative embodiments which will now be described, purely by way of example and without limitation to the scope of the claims, and with reference to the accompanying drawings, in which:

Figs, la - If show a prior art semantic lighting system comprising a projector and a detector;

Fig. 2 shows an apparatus comprisiing a spherical light emitter for projecting an image via a reflector onto a target surface in accordance with an embodiment of the invention, wherein a detector is arranged to detect light from the target surface which passes around the reflector;

Fig. 3 shows a similar apparatus in accordance with another embodiment wherein the reflector is arranged as a beam splitter so that light fromthe target surface passes through the reflector to the detector;

Fig. 4 shows an apparatus similar to that of Fig. 2;

Fig. 5 shows how the spherical light emitter of the apparatus of Fig, 4 can be rotated to steer the projected image;

Fig. 6 shows a similar apparatus incorporating a waveguide;

Fig. 7 A shows a similar apparatus with an array of light emitting elements coupled to the light emitter via a bundle of parallel waveguides;

Fig. 7B shows an individual light emitting element of Fig. 7A;

Fig. 7C shows a plan view of the distal (upper) end of the waveguide of Fig. 7A;

Fig. 8A shows a similar apparatus with an array of light emitting elements coupled to the light emitter via a single waveguide;

Fig. 8B shows a plan view of the distal end array of bundled optical fibres which feed into the base of the waveguide of Fig. 8A;

Fig. 9 shows a similar apparatus comprising a second reflector providing background illumination of the target surface;

Fig. 10 shows another embodiment wherein light fromthe target surface passes through a central aperture in the reflector to the detector;

Fig. 11 shows another embodiment wherein light from the target surface is reflected onto the detector;

Fig. 12 shows another embodiment similar to that of Fig. 11 wherein the reflected light from the target surface is conducted via a waveguide to the detector; and

Fig. 13 shows another embodiment similar to that of Fig. 11 wherein the reflected light from the target surface is directed via a beam splitter to the detector.

Reference numerals occurring in more than one of the figures indicate the same or corresponding elements in each of them.

Referring to Fig. 2, an embodiment comprises a light source 10, a light emitter 20 for directing light from the light source 10 onto a target surface 2, which may be for example the top of a desk or table, a wall or screen in a room, an exterior ground or building surface, a mannequin or model or a human or animal body. A detector 40 is arranged to detect light from the target surface 2, which may be for example light emitted (e.g. by fluorescence) from the target surface, or light reflected from the target surface; the reflected light may be ambient light or may be light projected onto the target surface from the light source 10. Optionally, the apparatus may be arranged to project an image 02 onto the target surface 2 as further described below.

The light emitter 20 comprises a first lens 21, a second lens 22, and a reflector 23. Light from the light source 10 passes through the first lens 21 to the reflector 23 and is reflected from the reflector 23 through the second lens 22 to the target surface 2. The light 7 from the light source 10 leaves the second lens along a mean projection axis XP, while the light 8 from the target surface 2 which enters the second lens 22 along the projection axis XP passes through the second lens 22 to the detector 40.

Advantageously, the light emitter may be arranged so that the light 8 from the target surface 2 entering the second lens 22 along the projection axis XP passes through or around the reflector 23 and then through a third lens 25 to the detector 40. Fig. 2 illustrates a particularly preferred arrangement in which the first and second lenses 21, 22 are respective first and second refractive surface regions of a transparent, substantially spherical optica! body 24 containing the reflector 23, each surface region having positive refractive power, so that light entering the body is refracted by the first surface and then travels through the body to the reflector, which reflects the light out of the body via the second surface at which the light is again refracted. A third surface region of the solid body 24 may form the third lens 25 as shown which focuses the light received from the target surface 2 onto the detector 40.

In the illustrated example, the light emitter is arranged to form a catadioptric system wherein the reflector 23 is smaller than the transparent optical body 24, so that it only occupies a central portion of the sphere. The refractive surface regions forming the first, second and third lenses 21, 22, 25 act like a biconvex spherical lens for both the projected beam of light 7 going out from the reflector as well as the light 8 travelling back from the target suface which is focussed onto the detector 40.

Those skilled in the art will appreciate that a catadioptric system is one in which an obstructing object is deliberately introduced into the axis of the optical system, for example, as known in a catadioptric telescope. Although an object placed intrabeam as a 'field stop' into an optical system would obscure a portion of the field of view, obscuration may not occur if the object is positioned at other locations such as the 'aperture stop' location, so that the normal rules of conjugate imaging apply.

The spherical optical body 24 functions as a biconvex lens or "thick" lens . The curvature of the body 24 and its refractive index effectively define the focal length of the 'thick' lens and thereby its conjugate imaging properties. Typically for example, for an acrylic ball of diameter 70 mm and refractive index n = 1.5, the back vertex focal length of the lens is of the order of 17 mm or so. Those skilled in the art will readily select the materials and dimensional parameters to suit applications involving near or distant target planes.

The first and second lenses may be configured as a conjugate imaging system so that an image generated by a graphic object 01 at an object plane PI may be imaged onto a conjugate image plane P2 represented by the target surface 2 as a projected image 02, and light emitted from the target surface (which may represent both the physical features of the target surface 2 and the image projected onto it) is imaged onto a conjugate detector plane P3.

The object plane PI may comprise for example the upper (exit) end surface of the waveguide, a mask or GOBO, a graticule, and/or any other graphic object 01, for example, a display unit such as an LCD or other digital light projection source displaying a graphic object 01 such as a static or moving image to be imaged onto the target surface 2. In the illustrated example, the first lens 21 is spaced apart from the object plane PI by a distance Dl, and a manual or automatic focussing adjustment means 30 may be provided for altering the distance Dl so as to maintain the conjugate relationship between the object plane PI and image plane P2 and focus the projected beam of light 7 onto the target surface 2. Corresponding focussing adjustment (not shown) may be provided for the detector plane P3. The focus may be adjusted progressively or continuously, for example, to move the projected image over a 2D or 3D surface. An adjustable lens may be interposed between the exit face of the waveguide and the first lens.

Other focusing and adjustment means may be used as known in the art. For example, the display unit may be located immediately in front of a variable focus optical system such as a liquid Sens as described below.

An autofocus mechanism can allow the ball optic and waveguide rod to remain in physical contact with each other while allowing the refraction of light between the waveguide and ball optic to be adjusted. For example, a variable focus liquid lens (as taught for example in

EP1674892 and other patents to Varioptic SA) may be placed between the waveguide and the first lens. The exit window of the liquid lens chamber may have a radius of curvature that matches that of the first lens. The focal length of the liquid lens may be altered by changing the relative curvature of the surface of a droplet (e.g. of oil) inside the chamber by means of a variably applied voltage from a voltage source, allowing remote control via a low current wire connection, for example, in applications where it is desired to minimise weight and mechanical complexity in the light emitter 20.

This system allows for the size of the cone of light leaving the optical system to be adjusted automatically without the need to physically translate the waveguide end face relative to the light emitter 20. This can be used to change the spot size on the target plane 2.

Other variable focus optical elements nay be used instead of a liquid lens. For example, a so- called "solid tuneable lens" could be used, comprising a pair of translucent plates with opposed, equally and oppositely curved surfaces, as disclosed by Yongchao Zou, Wei Zhang, Fook Siong Chau, and Guangya Zhou, "Miniature adjustable-focus endoscope with a solid electrically tunable lens," Opt. Express 23, 20582-20592 (2015).

When the plates are perfectly aligned, they behave as one unit without any focusing power— any wave phase shift induced by one plate is cancelled out by the other. However, when the plates are slightly offset to each other in a transverse direction (across the optical axis) the overall refractive effect of free form surfaces is to refract light like a traditional lens. The advantage of the solid tuneable lens is that the means of adjustment does not necessarily require an electrical supply and so that entire optical system can be passive (i.e. no electricity required) other than at the location of the light source.

If the light source 10 is a laser light source then the reflector 23 may be very small relative to the diameter of the spherical optical body 24, whic h may be rotated to direct the laser beam without affecting the imaging of the target surface 2 by the detector 40. The small cone of divergence of the laser beam reduces the potential for scattering of light within the ball optic and maximises the optical throughput of light onto the target surface. The optical body 24 may be a body of transparent material, either a unitary solid material such as glass or a transparent shell containing a liquid or gel with a suitable refractive index. In each case the reflector may be fixed to an external surface of the body or, as illustrated, fixed within the body. Alternatively the reflector may be mounted for rotation inside the optical body. The lenses and the reflector may be arranged in mutually fixed relation so that the light emitter 20 comprising the optical body 24, the reflector 23 and the first and second lenses 21, 22 may be rotated together as a single assembly about one, two or three axes and if desired, freely rotated without limitation in any direction relative to the light source 10 to move the light 7 from the light source over the target surface 2. The light emitter 20 may be mounted for rotation by an actuator (not shown) controlled by a processor as further described below, so that the projection axis XP can be moved across the target surface while maintaining the conjugate imaging relationship between the target surface 2 and the object plane PI at which the image or pattern 01 may be generated. This may be useful for example where the apparatus is controlled to selectively project, modify or move an image over the target surface 2 responsive to user interaction, or where the light source 10 includes or consists of a laser light source, so that the laser beam can be moved rapidly across the target surface to project a pattern (e.g. defined by the trajectory of the moving beam) onto the target surface, whereby the surface is scanned to form a digital representation of its 3D surface contour.

The optical body 24 may be a ball of solid transparent material (e.g. glass or plastics material), formed in two halves or hemispheres which are assembled together with a specular reflector 23 formed by a thin, mirrored surface layer sandwiched between their facing surfaces. The reflector 23 may alternatively be formed as a cavity between the two hemispheres, so that light incident on the wall of the cavity facing the hemisphere defining the first and second lenses is reflected by total internal reflection within the hemisphere. The spherical body 24 may be slidably mounted for rotation on a support element, e.g. in a circular aperture of a supporting frame or on the end surface of the waveguide, providing a simple and robust adjustment system for directing the projected beam of light 7.

Advantageously, the origin of the spherical body 24 may lie at the centre of the first reflector and on the central length axis of the light from the light source or waveguide. This makes it possible to maintain the centre of the reflector in constant alignment with the light source and to provide a constant focusing power as the light emitter is rotated.

The sliding interface between the surface of the spherical body 24 and the support element may provide a self cleaning action which wipes dirt from the first lens 21 every time the light emitter 20 is adjusted. The materials of the light emitter and waveguide or other contacting surfaces at the interface may be of different hardness so that the interface remains smooth as it wears by sliding friction between the two surfaces. For example, the light emitter 20 may be made from glass or hard plastics material and the waveguide from a softer plastics material, or one of the surfaces may be provided with a hard or soft coating. A layer of a relatively soft, optionally elastomeric, and transparent bearing material may be applied to the sliding interface, for example by 3D printing, to cushion the light emitter 20 and (if arranged at a distal end of the waveguide) to reduce Fresnel reflections. A layer of felt or other soft or antistatic bearing material could similarly be provided, optionally as a replaceable pad, to reduce wear on the surface of the spherical body 24 of the light emitter and wipe away dust as the light emitter is rotated in use.

A powered, e.g. motorised actuator (not shown) can also be provided for rotating the light emitter 20 relative to the light source 10 or waveguide. In this way for example the light emitter may be configured as an elevated light with the light source 10 being positioned at a lower level and connected to the light emitter 20 via a vertical or inclined light conductor, and remotely controlled to direct the beam 7. A handle or a textured surface region (not shown) such as a knurled ring may be formed on the light emitter 20 so that the user can more easily rotate it. Further alternatively, magnets or magnet-responsive elements (e.g. steel bodies) may be embedded within the light emitter so that it can be rotated by a magnetic or magnet-responsive wand.

The reflector 23 may be circular and of the same or smaller diameter relative to the spherical optical body 24. Where the reflector occupies only a small central region of the spherical optical body 24, the illumination beam from the light source 10 may be limited in its cone angle, so that the emitted light does not bypass the reflector 23.

Alternatively, if part of the emitted light is allowed to bypass the reflector, the escaping light may be used for monitoring the output of the light source 10 or re-directed towards the target surface 2 to provide off-axis illumination for illuminating the sides of an object in the field of view. For example, in the embodiment of Fig. 2 a light sensor or second reflector 31 may be provided for these purposes.

DETECTOR

The light source 10 may be arranged to project separate illumination and detection light beams, wihch may be emitted by different light emitting elements (e.g. laser and LED) and may be chosen as required from different bands of the electromagnetic spectrum, for example, ultraviolet, visible, and/or infrared. For example, a detection beam 7 may be emitted in one part of the spectrum (e.g. infra red) and superimposed onto an image 02 emitted in another part of the spectrum, e.g. the visible part of the spectrum. The detection beam7 might be detected by the detector 40 and used for example by projecting a pattern onto the target surface 2 to build a 3D image of the surface or as a graticule to identify the spatial coordinates of each pixel of the image.

The detector 40 may comprise a simple light detector for discriminating between the presence and absence of light, and/or any other suitable means for detecting light 8 in the visible or non- visible parts of the spectrum, which may be emitted from the target surface 2 and/or reflected from ambient light or from the illumination or detection light beams7 projected onto the target surface 2. The detector may detect radiant intensity, wavelength, and/or other measurable parameters. The detector 40 may be arranged to provide a response to the detected light 8, for example, to indicate the intensity of light detected in a particular wavelength. For example, the detector 40 might provide an indication (sound, light) if the detected intensity in the ultraviolet band drops below a threshold level (indicating that a fluorescent composition is no longer therapeutically effective) or if the detected intensity in the infrared band is above a target level (ndicating that the target surface 2 is hot). Or the detector might provide an indication that the detected light falling on a target surface, e.g. a human body surface or a group of growing plants, is deficient in a particular wavelength.

The detector 40 may comprise a charge coupled device or digital camera system for resolving images. The detector 40 may be configured to produce an output signal representing an image of the target surface 2, wherein the signal can be processed by the processor 50 to indicate individual pixels of the image representing the light 8 received from individual portions or pixels of the target surface 2. Thus, the processor 50 may determine from the signal the distribution of light over the target surface 2. The digitised image from the detector40 may comprise a matrix of pixels, each pixel corresponding to a spatial coordinate in the observed target plane P2, and may include both physical features of the target surface 2 and any pattern or image 02 projected onto the target surface 2.

PROCESSOR

The apparatus may include a processor 50, which may form part of a computer system including a memory, a physical user interface with a screen and keyboard, and suitable software for controlling the light source 10, actuators for focussing and rotating the light emitter 20, and other elements of the system. The processor 50 may control the projected light 7 responsive to signals from the detector 40 which receives the light 8 emitted or reflected from the target surface 2. For example, the processor 50 may analyse the signal from the detector 40 and invoke an adjustment of the direction of the beam 7 or the wavelength or intensity of the illumination from the light source 10. For example, if the signal indicates a deficiency in a particular wavelength of light falling on the target surface, the processor might be arranged to energise the light source to emit light in the deficient portion of the spectrum, for example, to enhance the therapeutic application of natural daylight to the human body, or to promote healthy plant growth in a greenhouse. Where the system is arranged to project an image 02 onto the target surface, the processor 50 may be arranged to receive a signal from the detector 40 representing the light 8 received from the target surface and to identify, by said signal, a spatial coincidence between a predefined element of the image 02 projected onto the target surface 2, and a physical feature at the target surface 2.

For example, the processor may indentify a physical obstruction 6 on the target surface 2 of Fig. 1C, and recognise that it occupies those pixels of the image which lie in the trajectory of the moving spots 5.

The processor may take an action responsive to identifying the spatial coincidence. For example, if the target surface 2 is a physical model of a physical road junction and the spots represent the expected future positions ofvehicles using the junction, the processor might generate a warning signal to indicate a potential collision.

Alternatively or additionally, the processor 50 may be arranged to modify the predefined element of the image responsive to identifying, by said signal, a spatial coincidence between the predefined element and a physical feature at the target surface. For example, in the scenario of Fig. 1C, the processor might be configured to adapt the trajectory of the moving spots 5 so that they move around the obstacle 6 (Fig. ID).

As in the scenario of Figs. 1A - IF, the detector may generate a moving image 02 on the target surface 2. Optionally, the image may include static elements and moving elements which move relative to static elements (e.g. chess pieces on a chess board.) The processor may identify, based on the signal from the detector 40, changes in a spatial relationship on the target surface 2 between an element of the moving image and a physical element (e..g. object 6, Fig 1C) present on the target surface . The processor may identify a change in the position or presence of such an object 6 on the target surface 2; for example, when a user moves a physical object on the surface, or removes the object from the surface, or places the object onto the surface. The detector may modify the static and/or moving elements of the image, e.g. their relationship to one another, responsive to the identified change (for example, by moving the chess piece on the board). The digitised image from the detector 40 may be converted via the processor 50 using a suitable image or pattern recognition algorithm as known in the art to identify both physical features of the target surface 2 and elements of the pattern or image 02 projected onto it. The processor 50 may identify an object (e.g. a user's hand or finger, a pointer) and based on the identification may take an action or not take an action. The processor 50 may correlate the physical features of the target surface or object with their spatial position relative to each pixel of the projected patttern or image 01. The processor may store the projected pattern or image data and correlate an identifed element of the received image with the coordinate values of the stored data. Thus, the processor 50 may correlate the coordinate position of an object or user intervention at the target surface 2 with a predefined entity (e.g. a moving spot, a playing card, a chess piece, a square on a chessboard, a virtual Iever on a virtual control panel) occupying that coordinate position in the projected pattern or image 02. The processor may then take an action or not take an action (e.g. move the spot, flip the card, modify the position of the Iever in the image and simultaneously send a command to a physical system, e.g. a machine controllable by the virtual Iever position) in response to the correlation.

For example, where a chess board is projected onto a target surface, the detector 50 may recognise the edges of the squares on the chess board using pattern recognition, so that when a user places their hand onto the image of the board, the processor may identify from the received image data which square on the board is indicated by the user's hand (and hence which piece to move). The piece might be modified to a flashing image to indicate that it has been selected, and then the user may touch another square to indicate the destination of the piece. The processor 50 may be configured to receive another command (e.g. via another sensor, e.g. a microphone and voice processor configured to recognise the spoken command "MOVE"), and to modify the image 01 to show the piece in the target square, and modify the other pieces accodingly, responsive to the command.

Advantageously, by combining both projection and detection along a common projection axis XP, the detected image and other features of the target surface 2 are more reliably correlated with the projected image 02, particularly on 3D surfaces. The example of Fig. 2 illustrates how a light source 10 and a detector 40 may be arranged to emit and receive light travelling coaxially on the projection axis XP without the use of a beamsplitter. Optionally, one or more additional light sources and detectors may be arranged, e.g. each as a respective annular array surrounding the primary light source or detector, so that a number of light sources and detectors may be arranged to emit and receive light travelling coaxialiy on the projection axis XP without the use of a beamsplitter.

BEAM SPLITTER

In alternative embodiments, the light emitter may be arranged so that the light from the light source passes via a beam splitter to the second lens, and the light from the target surface passes from the second lens via the beam splitter to the detector.

For example, instead of a specular reflector or a reflector operating by total internal reflection, the reflector may be configured as a beam splitter.

A beam splitter may be considered as a partially transmitting and partially reflecting surface and may be formed for example by a thin deposition of silver, or it may be designed in the form of specialised reflector such as an thin film stack (interference filter). Interference filters are useful in that they can be designed to be wavelength selective. An example of a so-called 50:50 beamsplitter is one that reflects 50% of an incident light signal whilst transmitting 50% of the signal directly through the mirror.

Such a partially transmitting, partially reflecting mirror has the advantage in that it may occupy the entirety of any plane intersecting the ball, whilst still allowing light to pass through the ball in orthogonal directions. One disadvantage of a beam splitter is the potential to lose a significant proportion of an incident light beam in either transmission or reflection mode i.e. a beam path is created that might serve no useful function or may create ghost reflections.

Figure 3 shows one such alternative arrangement in which the reflector 23' is formed as a partially reflecting and partially transmitting beamsplitter which extends across the whole diameter of the spherical body 24. For the case of a 50:50 beamsplitter half of the light signal from the source is reflected off the mirror and imaged onto the target scene and half of the light is transmitted onto the throughput system for use in additional optical process such as source output power monitoring or diffuse, background iilumination of the target surface 2 via a second reflector 31. A proportion of the light 8 received from the target plane passes through the reflector 23' and is imaged at the detector 40. ROTATION

Figure 4 shows how the preferred light emitter 20 of the Fig. 2 embodiment can project an image 02 onto the target surface 2, where the image is derived from a graphic object 01 that is illuminated by the light source 10. The detector 40 is positioned to receive light 8 from the target surface entering the second lens 22 along the projection axis XP.

The detector may be fixed relative to the spherical body 24 or may be rotated around the light emitter or spherical body 24 as required to maintain its field of view of the image 02 projected onto the target surface 2. Depending upon the orientation of the reflector 23, the field of view of the detector 40 may not always be directed along the projection axis XP; thus, the beam emitted along the projection axis XP might be directed out of the field of view of the detector 40. The detector 40 may be rotated circumferentially around the spherical body 24, under either manual control or automated control by the processor 50, to re-align the received light 8 with the projection axis XP, bringing the projected beam back into the field of view.

Figure 5 shows how the light emitter 24 can be adjusted where the projected spot of light is tracked across the scene by rotation of the ball optic under the control of the processor responsive to the signal from the detector. The beam of projected light 7 has moved the projected image 02 over the target surface 2 while the detector 40 observes another part of the target surface 2. The detector 40 may be moveable in fixed relation to the light emitter 20 or optical body 24 or, as shown, independently of the light emitter 20 or optical body 24 to adjust its field of view so as to re-align the optical axis of its received light beam 8 with the projection axis XP as shown in Fig. 4.

Rotation of the spherical optical body 24 may be accomplished by an actuator controlled by the processor 50 based on the signal from the detector 40, which may simultaneously adjust the focus and the generated image. Advantageously, a spherical optical body 24 can be rotated without affecting the conjugate imaging properties of the camera or other detector 40 which effectively 'sees around' the rotating central reflector 23.

The actuator (not shown) may be controlled by the processor 50, optionally responsive to the signal from the detector 40, to rotate the light emitter 20 so that the projected beam 7 is tracked across the target surface 2. This can be used for example to scan the target surface with a pattern of light (so-called "structured light"), which may be formed for example by a moving straight line or a rapidly moving beam of conventional or laser light. The beam 7 may be projected as a static pattern or moved across the target surface to produce a static or moving patttern on the target surface, so that the distortion of the known pattern produced on the surface and represented by the signal from the detector represents a 3-D contour of the target surface 2. Advantageously, the spherical optical body 24 can be rotated about a fixed mechanical centre of rotation without interfering with the refractive properties of the system. WAVEGUIDE

Figure 6 shows how a waveguide 60 may be provided to deliver the light via the object plane to the first lens, optionally also functioning as a stand to support the light emitter on the base in which the light source is housed. The use of a waveguide 60 distances the light emitter 20 and display unit from the heat produced by the light source 10, and allows the use of a larger and more powerful light source 10 without increasing the size of the light emitter 20. The light source unit and electrical power supply may be arranged e.g. in a base unit 73 to provide mechanical stability and allow for heat management, control and cooling.

Waveguiding can also be used to establish certain modal conditions that provide optimal uniformity of illuminance at the distal end of the waveguide where an image display device may be located, and to control exit ray paths to reduce aberrations and stray light. The waveguide may be a hollow tube, preferably with a reflective inner surface and, optionally, beam transfer lenses spaced apart along its length. More preferably however the waveguide is a body of solid transparent material which conducts light by total internal reflection and so rejects deviant rays which leave the waveguide at angles greater than the angle of total internal reflection. The waveguide may be a parallel sided rod or tube with a circular or elliptical, polygonal or other non-circular cross section made from glass, acrylic or other suitable plastics material. The waveguide may also support the light emitter 20, optionally for rotation, or a separate support element such as a ring, a gimballed frame or an axle (not shown) may be provided.

Optionally, an additional coupling optic (not shown) might be used between the light source and the waveguide to form the desired family of rays within the waveguide and to maximise coupling of light into the system. In these regards it can be understood that establishing a certain family of guided rays within a waveguide lighting system may be desirable in order to achieve for example, good uniformity of projected illuminance in the task plane. For example, it may be desirable to achieve a family of rays that are all guided at low angles to the optical axis with no extremal rays propagating at high angles to the axis, alternatively it may be desirable to exclude the presence of rays guided at low angles and establish rays at a high angle etc.; the choice of guided ray family will depend upon the specific lighting task, and may be determined for example by a ray trace optimisation procedure.

Preferably, all or most of the light emitted by the light source 10 is coupled into the waveguide as known in the art to form a well-defined family of rays which are guided by refraction and total internal reflection, which for acrylic and glass is typically within a cone angle of about 50 degrees centred on the length axis of the waveguide, so that rays outside the desired angular range are not conducted to the light emitter. It should be noted that depending on the specific nature of the optical launch into the waveguide it is possible either to establish and maintain a specific family of guided light rays, or instead to scramble the ray paths within the guide, according to the lighting effect to be achieved.

For example, random mixing of the rays propagating in the guide may advantageously prevent the light source from being imaged when observed from within the beam leaving the light emitter, so that LEDs or other point light sources can be used without dazzling or causing a persistent retinal image. As an example, such random mixing might be achieved by applying a diffuse surface finish to the launch end of the waveguide rod. Thus, a powerful array of LEDs may be provided whose rays are scrambled within the waveguide to obviate the risk of damage to the user's eyes. Alternatively, and in the absence of a diffusing structure within the launch, it is possible to establish and maintain a fixed set of ray paths in the waveguide that can usefully convey desired features from the light source (such as the light output from individual LED dies) to the distal end of the waveguide.

When illuminated by the family of rays emitted from the end of the waveguide, which may be randomly mixed within the waveguide and which are confined by conduction through the waveguide within a well defined angular envelope, the light emitter can generate a well defined beam of the desired cone angle, for example, about 45 degrees, and with even intensity throughout its cross section and sharp cut-off at its edges.

The shape of the projected spot on the target surface 2 may be determined by the cross section of the waveguide or a mask arranged at its emission surface or object plane PI. For example, a circular profile waveguide rod may project an elliptical spot while a square profile rod may project a rectangular spot. If the light emitter 20 is arranged to project light along a shallow angle relative to the task plane P2 and a circular or square spot is desired, then the waveguide may have an elliptical or rectangular cross section with the shorter axis aligned with the horizontal vector of the beam to compensate for the angle of incidence of the beam on the target surface.

Different types of light source may be combined and projected onto the target surface 2 using appropriate degrees of in- and out-of-focus imaging of the different illumination spectra as required. For example, a targeting beam may be directed via a secondary waveguide, (e.g. a tubular waveguide coaxially surrounding the primary waveguide or an optical fibre or rod arranged in parallel with or coaxially inside the primary waveguide) could be used to identify and define a subject in the target plane 2, by for example projecting a ring or annular image onto the task plane, before the primary waveguide is used to project therapeutically effective light onto the target plane 2.

This could be utilised for example in laser surgery to ensure that the surgeon is targeting the correct location for surgery prior to firing of the main (surgical) beam. Advantageous features include the centration of the various optical elements around a common optical axis XP, and the ease with which that axis can be directed towards a target surface 2.

An outer cylindrical secondary waveguide could be used for example to project a circle onto the target to define a specific area of observation to be viewed by the detector 40. In another example, if defocused, a secondary, outer cylindrical waveguide (such as illustrated in Figs. 11 and 12) could project a patch of light onto the target surface 2 from which any resulting fluorescence could be observed by the detec tor 2, for example, to monitor the progress of treatment during photodynamic therapy as described above.

Optonally, other beam modifiers 71 (Fig. 2) such as a filter or a polariser may be positioned (permanently or adjustably) between the end face of the waveguide and the incident surface of the light emitter. LIGHT SOURCE

The light source 10 may comprise a lamp, a laser light source, and/or one or more LEDs or other poiint light sources.

A plurality of high intensity or point light emitting elements 11 such as light emitting diodes may be arranged with a plurality of individual waveguides, each conveying the light emitted from a respective one or ones of the multiple light emitting elements. Optionally, the plurality of waveguides may be bundled together to conduct light to the light emitter 20, or may conduct light to one or more principal waveguides which in turn conduct(s) the light to the light emitter. The multiple light emitting elements 11 could be arranged for example in a base 73 of the lighting device, with the multiple waveguides arranged as optical fibres or rods and converging to the base of the or each principal waveguide, which extends upwardly to the light emitter.

For example, a 2D array of light emitting elements 11, e.g. LEDs, may be arranged or selectively energised to project a pattern or image (e.g. an alphanumeric symbol) 02 onto the target surface 2. The detector 40 may be used for example to determine the brightness of the image 02 and adjust the radiant intensity of each light emitting element 11 accordingly. Figure 7A illustrates an apparatus including a processor 50 (not shown), a light source 10, and at least one waveguide 60. A detector 40 is arranged to detect light 8 from or incident on the target surface 2; for example, the detected light 8 may be emitted by radiation from the target surface, or by fluorescence from the target surface excited by light emitted by the light source 10, or may be reflected from ambient light falling on the target surface or from light emitted by the light source 10 and projected onto the target surface.

The light source 10 comprises a plurality of light emitting elements 11, each of the light emitting elements 11 being individually controllable by the processor 50 to adjust a radiant intensity of its emitted light. The processor 50 is arranged to receive a signal from the detector 40 representing the light received from or incident on the target surface 2, and to adjust the radiant intensity of the light emitted by each of the light emitting elements responsive to the signal to obtain an even radiant intensity over the target surface. Each light emitting element 11 may be a single source such as an LED or may be a compound element comprising a n array of primary light emitting elements 12, e.g. LEDs, each emitting light at a different wavelength (Fig. 7A). An example is the LZ7 7 wavelength emitter supplied by Led Engin of California, USA. The primary light emitting elements 12, e.g. LEDs may be individua lly addressable. The processor 50 may be configured to select a desired wavelength of the emitted light 7 by adjusting together all the primary light emitting elements 12 of the same wavelength, e.g. to increase the output at the red end of the spectrum. The spatial distribution of light across the target surface 2 will be determined by the optical system and by the spatial distribution of light across the 2D array of light emitters 11 and so can be adjusted by individually adjusting the radiant intensity (power input) of each group of primary light emitting elements 12 forming a compound light emitting element 11 - i.e. the power to the compou nd element 11 can be adjusted to tweak up or down the output of all its primary elements 12. Thus, overall wavelength can be adjusted across the whole light source 10, and radiant intensity can be adjusted pixel by pixel. Of course, other adjustment regimes may be implemented by suitably configuring the electrical control lines (not shown) to address the LEDs 12 individually or group by group, as required.

As in the previously described embodiments, a light emitter 20 is arranged to direct light from the light source 10 onto the target surface 2. The light emitter comprises at least a lens 22 and is arranged so that the light 7 from the light source 10 passes through the at least one waveguide 60 to the lens 22 and then through the lens 22 to the target surface 2. The light from the light source leaves the lens 22 along a projection axis XP. Advantageously, as illustrated by the examples of Fig. 7A and Fig. 8A, the light emitter 20 may be arranged generally as described above with reference to the embodiment of Fig. 2 to include first and second lenses 21, 22 and a reflector 23, so that the light 7 from the light source 10 passes from the at least one waveguide 60 through the first lens 21 to the reflector 23 and then from the reflector through the second lens 22 to the target surface 2 along the projection axis XP, while the light 8 from the target surface entering the second lens 22 along the projection axis XP passes through the second lens 22 to the detector 40.

In alternative embodiments, only one lens 22 may be provided without lens 21 or reflector 23. As illustrated by the example of Fig. 7A, the at least one waveguide 60 may comprise a plurality of elongate waveguides 61 which are arranged in parallel relation, each of the waveguides 61 being arranged to transmit the light from a respective one or ones of the light emitting elements 11 to the light emitter 20. The multiple waveguides 61 may be for example acrylic or glass rods or optical fibres, and form a 2D array 62 of light emission regions at their distal (upper) end as seen in Figure 7C. The light emitted from each light emitting element 11 in the array forming the light source 10 is shown as being delivered via a flexible fibre optic cable 65, which advantageously allows each light source to be mounted and driven in a larger spatial area than that defined by the waveguide itself. This offers benefits in terms of thermal management (cooling), physical mounting of the light emitting elements and modular 'plug-and-play' capability where different light sources 10 can be configured in the system remotely from the waveguide and lamp system.

The system has the advantage that the light emitter system can transfer (image) the 2D light pattern at the distal end array 62 of the waveguide multiplex whilst also varying the light contained within each guide (e.g. radiant power level, spectrum) to achieve a desired light pattern on the scene, such as a 'top-hat' flattened 2D irradiance profile across a planar or curved surface, a graphic symbol such as a projected 'matrix' style letter or number formed by lighting up individual waveguides in the matrix. The light pattern so projected onto the scene can be observed through the light emitter 20 by the detector 40.

The detector 40 could detect the uniformity or otherwise of the projected light pattern and adjust the illumination accordingly. For example, if the edges of the projected light pattern were observed to be relatively low in power compared to the centre of the matrix, the light output in the corresponding waveguides could be adjusted accordingly (e.g. heuristically) until a suitable degree of uniformity is detected by the detector 40. Instead of a bundle of individual waveguides 61 as illustrated in the embodiment of Fig. 7A, a single waveguide 60 may be arranged to transmit the light from the light source 10 to the lens 22, each of the light emitting elements 11 being arranged to emit light into the single waveguide 60. Figure 8A exemplifies such an arrangement, wherein the multiplex of waveguides 61 of Fig. 7A is replaced by a single waveguide 60 that combines the light from a 2D array of light emitting elements 11 and transfers their combined output to the distal (upper) end of the waveguide 60 for projection onto the target surface 2. As in the example of Fig. 7A, each individual light emitting element 11 is coupled to the single waveguide by an individual waveguide 65, e.g. an optical fibre, which are bundled together to form an array 64 at their upper (emission) ends as shown in Figure 8B. The detector 50 is arranged in the same way as the Fig. 2 and Fig. 7A embodiments, forming a control loop with the detector 40 and light source 10, but is not shown. ADJUSTING RADIANT INTENSITY

Because of the potential for complex mode paths in the waveguide there may not be a simplistic relationship between the nature of the light field at the distal end of the waveguide 60 relative to the illumination at the launch end. However, a complex spatial relationship may exist, so that the radiant intensity of the light emitted by each light emitting element 11 can be adjusted to modify the projected light pattern on the target surface 2 under control from the processor 50 responsive to the signal from the detector 40 so as to obtain a substantially even distribution over the target surface 2. This ensures for example that photodynamic therapy will be effective over the whole target body surface without disproportionately irradiating parts of the surface.

The processor may be arranged to adjust the radiant intensity of the light emitted by each of the light emitting elements based on an algorithm, i.e. a defined process (whether comprising a predefined number of steps or not). Optionally, an heuristic algorithm may be used to approximate or converge on an optimal light distribution .

Adantageously, the use of a single or compound waveguide 60 to deliver the light from an array of light emitting elements 11 via a lens 22 to the target surface 2 makes it possible to deliver more radiant power along a single emission axis XP without obstructing access to the target surface. At the same time, the detector 40 and processor 50 make it possible to adjust the output from each element 11 in the array so as to deliver an even radiant intensity over the target surface. The waveguide or waveguide bundle may further be arranged for safety to scramble the light rays from each point light source to provide a family of non-parallel rays within a small cone angle, the rays being randomised within the beam so that the light source cannot be imaged onto the user's retina.

Further advantageously, as discussed in relation to the foregoing embodiments and as similarly illustrated in the examples of Figs. 7A and 8A, the light emitter 20 and the detector 40 may be arranged so that the light from the target surface 2 entering the lens 22 along the projection axis XP passes through the lens 22 to the detector 40. Thus, the light 8 is detected along the same projection axis as the emitted light 7, whereby the pattern of emitted light (whiich may be imaged onto the target suraface 2 from the distal end of the waveguide or waveguide bundie) can be more reliably correlated with the pattern of detected light. This provides simpler and more effective control of the light distribution, particularly on a 3D surface.

CALIBRATION STEP

It is desirable, e.g .for effective light therapy, to ensure that the signal from the detector 40 acurately indicates the radiant intensity of the emitted light 7 over the surface area of each region of the target surface 2, irrespective of variations in surface colour or texture or the angular orientation of each region of the target surface 2 relative to the projection axis XP. One way to ensure this is to adjust the radiant intensity of the light emitting elements 11 responsive to a calibration step which is carried out prior to energising the light emitting elements 11 for the main procedure in which the target surface 2 is irradiated for therapeutic or other purposes. The light source 10 may include more than one light emitting element 11 of the same or different types, which may be used respectively for the calibration step and for the main procedure. For example, the Ight source 10 may comprise an array of LEDs for emitting the therapeutic radiation, and a laser for scanning the surface 2 with a pattern of light in the calibration step. During the calibration step, the apparatus may be arranged to project a pattern onto the target surface 2, the pattern being arranged so that the signal from the processor 40 I is indicative of a three dimensiona l contour of the target surface 2. The processor 40 may be arranged to adjust the radiant intensity of the light emitted by each of the light emitting elements 11 responsive to the signal indicative of said three dimensional contour so as to obtain an even radiant intensity over the target su rface 2.

The pattern could be represented by a static pattern such as a shaped or structured beam of light (e.g. a grid, an array of dots, a circle or a straight line) generated by an image display unit or a selected pattern of energised light emitting elements 11 in the array, or a moving pattern formed e.g. by a laser beam, which might be guided for example by an actuator rotating the light emitter 20 or by a separate mirror or laser guiding means (not shown) as known in the art of scanning.

After projecting a known pattern, the processor compares the known pattern with the signal from the detector 40 indicating the pattern as imaged on the target su rface 2. For example, a circle projected onto an inclined plane may produce an ellipse whose 'stretch' is proportional to the projection angle deviation from the normal (by cosine theta) . Thus, a known 'a priori' projection detection algorithm may be used to map the target surface 2, as known in the art of 3D scanning. Advantageously, the coaxial arrangement of the projected and detected light beams 7, 8 along the projection axis XP may provide more accurate scanning by obviating the need to adjust the algorithm to allow for offset or skew in the optical system. As an alternative to carrying out a calibration step on the target surface 2, where for example the surface is a human or animal body surface, the calibration step may be carried out on a dummy target (e.g. a moulded polystyrene model of the target body part) before commencing the treatment. The corresponding actual target surface (e.g. body part) could be correlated via the detector 40 (e.g. based on its 3D spatial coordinates as detected by a camera) and processor 50 with the scanned dummy target surface and the output intensity of the light emitting elements 11 adjusted accordingly. The radiant intensity of the light emitting elements 11 and/or the focus or rotational position of the light emitter 20 might subsequently be adjusted (e.g. via actuators) to follow movements of the target surface 2 as it is tracked bythe detector 40.

ALTERNATIVE DETECTOR CONFIGURATIONS

In alternative embodiments (not illustrated), the detector might be arranged differently. For example, it might be disconnected from the light emitter 20. In such embodiments the detector could be a hand held detector which is moved over the target surface 2 in a preliminary calibration step.

For example, the apparatus may be configured to project a reference pattern, e.g. a 'dot' map grid on the target surface 2, while a small (e.g . 5 mm diameter) detector is moved by hand to the centre of each dot on the grid as imaged on the target surface.

The detector may transmit a signal to the processor indicative of the momentary position of the detector and the radiant intensity of the received light incident on the detector in that position. It should be understood that in such embodiments, the light 7 incident on the detector at any given position oft he detector on the target surface 2 is construed to be incident on the target surface 2, in the sense that it would, if the detector were absent, be incident on the same region of the target surface 2 as that momentarily covered by the detector during the calibration procedure.

In such alternative embodiments, instead of a moving detector, the detector might be flexible or shaped to lie over the contours of the target surface 2, comprising an array of individual detecting elements to detect the radiant intensity of light 7 falling onto each pixel of the target surface 2. For example, the detector might comprise a diode mesh having silicon detectors embedded in a flexible sheet, similar to a flexible light sheet as well known in the art but arranged to function as a detector rather than a light emitter.

METHOD OF USE

From the foregoing discussion it will be understood that an apparatus comprising an array of individually adjustable light emitting elements 11 coupled via at least one waveguide 60 to at least one lens 22, whether or not including the additional features of the the embodiments of Figs. 7A and 8A, may be used in a method for projecting and detecting light on a target surface 2. A processor 50 receives a signal from a detector (optionally but not necessarily a detector 40 mechanically connected to the light emitter 20} representing the light received from or incident on the target surface 2, and adjusts the radiant intensity of the light from each of the light emitting elements 11 responsive to the signal, optionally based on an heuristic algorithm, to obtain an even radiant intensity over the target surface 2. Advantageously, the light emitter 20 and the detector 40 may be arranged so that the light 8 from the target surface 2 entering the lens 22 along the projection axis XP passes through the lens 22 to the detector 40. Optionally, the method may include projecting a pattern onto the target surface 2, the pattern being arranged so that the signal is indicative of a three dimensional contour of the target surface 2; and adjusting, by the processor 40, the radiant intensity of the light emitted by each of the light emitting elements 11 responsive to the signal indicative of said three dimensional contour, so as to obtain an even radiant intensity over the target surface 2.

POINTING DEVICE

In embodiments, the apparatus may be configured in the manner of an overhead projector with a flat table at the object plane PI so that a transparent graphic 01 placed on the table can be imaged onto the target surface 2, or may be configured to project a static or moving image generated on the user's laptop and fed to the image display unit at the object plane PI via the processor 50 or via a USB connection or the like.

In these and other embodiments, a hand held pointing device 80 (Fig. 2) may be provided for generating an indicating beam 81 of light, optionally laser light, which may be directed ontoi the target surface to indicate a feature in the image 02 projected by the light emitter 20 onto the target surface 2. The pointing device could be powered by a local battery or via a cable from the rest of the apparatus.

During a presentation to an audience, the presenter might point the pointing device 80 at the target surface 2 to point out to the audience certain features of the image 02 (graphs, pictures, etc.) as he refers to them.

One problem of prior art laser pointing devices is that they can be inadvertently pointed towards the audience. To solve this problem, the apparatus (e.g. via processor 50, or if no processor is provided, by suitable circuitry responsive to detector 40) may be arranged to send a control signal to the pointing device 80 via a communication link (e.g. via Bluetooth (RTM) or other near field communications link, or via a flexible cable) with the pointing device, so as to modify the indicating beam 81 responsive to detecting, via the detector 40, the presence or absence of the indicating beam 81 on the target surface 2. For example, the apparatus might be configured to reduce the radiant intensity or change the wavelength of the indicating beam 81 responsive to the spot of light produced by the indicating beam moving off the target surface 2, and to increase the intensity or change the wavelength of the indicating beam responsive to the spot re-appearing on the target surface. Thus, if the user inadvertently waves the pointing device 80 at the audience, the laser or other indicating beam 81 may be turned off or dimmed.

The indicating beam 81 may be generated by a light source within the pointing device 80, the light source optionally including more than one light emitting device. The light source 80 may be operable to generate selectively a main (full power) indicating beam 81 and a lower energy pilot indicating beam 81 which can be detected by the detector 40 so as to energise the main beam. The main and/or pilot indicating beam 81 may include a recognisable feature (e.g. may be pulsed at a certain frequency, or may comprise a defined mix of wavelengths) so that it can be reliably detected on the target surface 2 by the detector 40.

OTHER FEATURES

Figure 9 shows an off-axis illumination scheme where the light that misses the reflector 23 is converted by an extraneous reflector 31 (mirror or diffuser) to provide 'off-axis' illumination. The lamp system could be used to create a simultaneous spot light and diffuse light source for use in illuminating a space or task with both direct and indirect illumination. Furthermore if the diameter of the mirror could be adjusted {similar to an iris diaphragm) the balance of light power used for spotlight illumination and the general diffuse illumination could be adjusted, !n all of these modes the detector 40 can observe and provide feedback on the illumination properties of the system.

In yet further alternative arrangements, a central aperture 75 may be arranged in the reflector 23", and the detector 40 arranged to receive the light 8 from the target surface 2 entering the second lens 22 along the projection axis XP and passing through the second lens 22 via the aperture 75 to the detector 40.

The light source may be arranged to direct the emitted light 7 in an annular beam, e..g. via a tubular, cylindrical waveguide as illustrated in Figs. 11 and 12, so that all of its emitted light is reflected by the annular reflector 23" without passing through the aperture. Alternatively, part of the emitted light from the light source 10 may be allowed to pass through the aperture 75.

Figure 10 shows one such alternative embodiment incorporating background illumination of the target surface 2. The ight 7 from the light source 10 that passes through the aperture 75 in the reflector 23" is converted by an extraneous reflector 31 (either specular or diffusive) to provide Off-axis' illumination of the target surface 2. The lamp system could be used for example to create a simultaneous spot light and diffuse light source for use in illuminating a space or task with both direct and indirect illumination. In a development (not shown) the diameter of the mirror 23" may be adjustable (similar to an iris diaphragm) to alter the the balance of light power used for spotlight illumination and the general diffuse illumination. The focussing properties and curvatures of the various optical elements could be varied to create various combinations of on-axis and off-axis illumination; conceivably the light from the central mirror 23" could be made to diffusely illuminate the scene and the light from the secondary, upper reflector 31 used for the spotlight. Figure 11 illustrates how the detector 40 may be located at the conjugate image detector plane P3 of the optical system (relative to the task plane P2) to receive the light 8 from the target surface 2 which is reflected by the reflector 23. Simultaneous focussing of the projected and detected light 7, 8 is provided by rotating a cylindrical support element 66 in a collar 67, with the spherical body 24 being rotatabiy and slidably supported on the support element so that it can be rotated about its geometric centre in any desired direction to direct the beam.

In the example shown, a specular reflector 23 is arranged across the diameter of the spherical body 24, which may be replaced for example with a hemisphere.

It is a property of physically large 'macro' optical waveguides (for example, of tens of millimetres in diameter) that dependent upon the quality (e.g. polishing) of the end face surfaces of the waveguide, an image focussed upon one end of the waveguide can be transferred reasonably well to the other end of the waveguide, whereupon it can be viewed by a camera system if so desired. Alternatively, if the waveguide end faces are made diffuse, the light rays in the waveguide can become scrambled with no such imaging possible.

Figure 12 shows how a secondary waveguide 68 may be arranged to deliver the light 8 from the target surface 2 as an image to a detector 40 arranged at the lower end of the waveguide in the base of the assembly. The spherical body 24 of the light emitter20 may be rotated, e.g. to follow a target as it moves across the target surface 2, without disrupting the image delivered to the detector 40. In the illustrated example, a tubular, primary waveguide 60 of solid transparent material transmits the projected light 7 from the light source 10 to the first lens 21, while an elongate rod of solid transparent material is arranged coaxially inside the primary waveguide to form the secondary waveguide 68 which transmits the received light 8 reflected from the reflector 23 to the detector 40 located at the base of the assembly.

The end facesof the primary and secondary waveguides may not necessarily be co-planar. For example, the end 70 of the primary waveguide may be set closer towards the light emitter 20 than the end face 69 of the secondary waveguide 68. In this manner, when the end face 69 of the secondary waveguide 68 and the target surface 2 form a conjugate image pair, the light 7 from the primary waveguide 60 may be blurred or distributed across the target surface 2. Such a situation might be useful in analysis of e.g. fluorescence from an object located at the target surface 2, where the (blurred) light 7 from the primary waveguide stimulates fluorescence from the object by broadly illuminating it with light, whilst the fluorescent light 8 emitted by the object is imaged back via the secondary waveguide 68 for detection by the detector 40.

If instead the end faces 69, 70 of the primary and secondary waveguides 60, 68 are arranged to be coplanar a nd conjugate to the target plane 92, the projected light 7 will form an annulus (circle or ellipse) around the central region of the target surface 2, and any light 8 from within the projected ellipse will be imaged back onto the end face 69 of the secondary waveguide 68 and via the secondary waveguide to the detector 40. Figs. 11 and 12 illustrate how simple sliding a nd rotating mechanisms may provide relative adjustment between the or each waveguide 60, 68 and the light emitter 20. For example, rotation of the outer cylindrical tubular waveguide 60 or a tubular support element 66 within a threaded collar 67 may provides a focusing mechanism 30 whose action causes relative axial (up and down ) movement between the light emitter 20 and the outer waveguide 60, which guides the light 7 to be projected onto the target surface 2, as well as the inner waveguide 68 whose upper end surface 69 defines the detector plane P3. The mechanism 30 could be automated, for example, to be driven using a stepper type motor.

Alternative means of adjustment could be devised to allow for the primary waveguide 60 to be adjusted relative to both the light emitter 20 and the secondary waveguide 68 to allow for a range of conjugate imaging scenarios (i.e. blurred or in-focus).

Figure 13 shows another alternative embodiment which uses a beam splitter 76 as a 'combiner'. The beamsplitter is illustrated in a com mon format known as a 'cube' beamsplitter wherein a mirror 77 is embedded within a cube shaped optical element. In this way, the light 7 from the light source 10 (eg an LCD display illuminated by the waveguide) is combined co-axially with the light 8 returning from the target surface 2 to the detector 40. In a development (not shown), the optical body 24 might be arranged i n sliding contact with the beam splitter 76, e.g. in a spherically concave depression in its upper surface as shown.

The optical system in each of the abovedescribed embodiments may include other components as required for the application, for example, correction plates, spectral filters, polarising elements, or lenses, filters, beamsplitters, or other components that are wavelength and/or polarisation sensitive.

An object corrector piate (not shown), e.g. a Schmidt plate, may be provided to correct for any aberrations or distortions introduced into the system by the spherical optical body 24. A detector corrector plate 45 may similarly be provided to correct for distortion or geometrical optics aberration or to provide spectral filtering of the light 8 received by the detector 40. Optionally, aspheric surfaces mght be provided on the optical body 24 or other optical elements to further correct for aberrations. Other distortion correction techniques may be employed, either by means of further optical elements or via software for processing the projected and detected images, as known in the art of catadioptric systems. Although not shown, any corrector plates or other additional optical elements may have an outer curvature that matches the curvature of the spherical body 24 to provide a sliding optical interface. The or each lens, reflector, correction plates, or other elements of the optical system may be selected and arranged in the optical pathway as generally known in the art to provide anamorphic distortion of the projected or received light, for example, to compensate for the angle of the projection axis XP relative to the target surface 2. A similar corrective effect may be obtained by suitable manipulation of the image 01, 02, for example, by the processor 50 responsive to the received signal. For example, if the image 01 is projected onto a 3-D contoured surface 2, the processor 50 may determine from the received signal a distortion in the image 02, and may correct the distortion by rotating the light emitter 20 to bring different reflective or refractive surfaces or other corrective optical elements into the optical pathway, by adjusting the conjugate imaging focus of the system, and/or by modifying the image 01.

For example, the apparatus could be used to project a spotlight whose projected profile is always circular regardless of the orientation of the target surface 2, Thus for example by using an elliptically shaped graphic 01 the elliptical distortion of the projected beam 7 could be counteracted regardless of the surface inclination. If a waveguide 60 with a noncircular section is used to deliver the light to the first lens 21, then the system may similarly adapt or maintain the beam profile defined by the section of the waveguide 60 independently of the angle of the projection axis XP relative to the target surface 2 (creating e.g. a square frame or a chessboard which remains the same shape as the beam is tracked diagonally across the slanting surface 2). APPLICATIONS

Embodiments of the invention may be configured for use in diagnosis, therapy or surgery or as a "semantic lighting" system to provide a user interface for many different purposes, including for example an interactive virtual keyboard, a control panel for controlling a machine, or a virtual interface for interacting with another entity (e.g. a virtual aircraft cockpit, another human being or a virtual human being) in a system also providing haptic and other sensory feedback to the user. Possible applications are as follows:

Presence Detection

The detector confgured as a camera within the lamp system can be used to survey a scene for the presence or movement of personnel and the illumination level from the lamp modified as appropriate for e.g. observation in the infrared region of the spectrum, or automatically raising the illumination levels as needed. The rotation of the spherical body 24 can be used for directing the illumination beam 7 towards the personnel as they move within the field of view of the system if desired. Advantageously the system would not necessarily be noted to have the function of a camera and can otherwise be aesthetically designed as a light fitting as desired.

Object Recognition

The system could be used to recognise objects on e.g. a production line wherein the means of simultaneous on-axis illumination, projection and detection could be enhanced by the system.

Semantic Detection - Retail

The camera within the lamp system can be used to survey a scene for appropriate sensing information pertinent to a task and alter the projected light onto the task plane 2 as necessary. For example in a retail application a person touching an item on display could have relevant information such as the retail price of the item, the stock level etc projected onto the scene in response to the user interaction. Semantic Detection - Safety

The camera within the lamp system can be used to survey a scene for appropriate sensing information relating to safety and alter the illumination level as necessary. For example, the lamp system is used to illuminate a cooker as general task light to assist with e.g. cooking - the light emitter 20 could project the temperature of eg a cooking utensil onto the utensil. The detector 40 could also detect the temperature of a hot plate, or note whether a gas ring has been left on; it may then change the illumination level or emit an audible or visual warning to alert personnel as necessary. If the system was designed to operate in the infrared for example, then the apparatus could function both as a spotlight as well as fire sensor.

Semantic Detection - Table Top Interactive System

The LCD display or other means for producing the object image 01 can be used to project a graphic 02 onto a suitable surface 2 such as a wall or a table that is under observation by the detector 40 configured as a camera. The information displayed could be dynamically adjusted depending upon user interaction in the scene within the field of view of the camera. Thus a board game such as chess or a card game could be projected onto a table top and the component pieces moved in correspondence with user interaction such as touching the displayed image or a verbal command (e.g. to move a chess piece). The processor 50 would then display the updated graphic onto the display surface 2 in readiness for subsequent user interaction.

Automated Beam Steering Device

The apparatus could be used as a means of steering a beam of light 7 reflected from the central mirror 23, whilst the beam direction XP is tracked within the field of view by the detector 40 configured as a camera. A laser source 10 of reduced divergence would allow the use of a relatively small diameter mirror 23, which would not obstruct the rays 8 utilised for the imaging process. One advantage of this method is that the camera system can be located along the main axis XP of the field of view of the system tracking the beam within the field of view (as eg projected onto a target 2 within the field of view). Thus as the laser beam 7 moves across the target area 2 the beam could be steered automatically by moving the mirror 23 as desired - the spherical body 24 is, in mechanical terms, very robust in a way that is akin to that of a movable ball joint mechanism; hence when mounted in a suitable supporting holder, the orientation of the optic 24 (and possibly the entire camera head assembly 40) can be achieved rapidly (via rotation of the spherical body 24 over two axes) with very likely a minimal 'walk-off of the beam 7 and field of view of the camera 40 during the a rotation. As an example, the system could be utilised for alignment of complex laser systems on an optical table as a low cost USB camera 40 and light emitter 20 could be affixed to each optical element and used to assist with remote axial steering of the beam 7 with each camera 40 looking directly along the laser path towards the target location 2.

Medical Treatments

The apparatus could be used for medical treatments wherein the detector configured as a camera 40 is arranged to view a designated treatment site 2 (such as a skin lesion) and the treatment beam 7 (such as derived from a laser or LED source 10) directed across the treatment site 2 under manual or automatic control. In one treatment such as photodynamic therapy, the apparatus could utilise two beams of light 7, one beam 7 as required for the medical treatment (e.g. artificial daylight) and the other beam 7 for checking for the presence of certain manifestations of the treatment. For example, certain PDT medical creams can be made to fluoresce and thus the detector 40 could measure the level of fluorescence during the treatment and detect when the cream has been expended by the treatment. In this manner, the detector 40 could be used to analyse the treatment site 2 for detection of local regions for treatment, to then steer the direction of the irradiating beam across the treatment site 2, and for detecting fluorescence from the treatment site 2 as the topical cream is expended during the treatment.

Tattoo Removal

A treatment such as tattoo removal could be undertaken in the same way wherein the detector configured e.g. as a camera 40 detects the colour and shape of the tattoo and directs the laser removal laser beam 7 (including its power and spectral content) onto the treatment site 2. In this way a high irradiance laser beam 7 could be steered automatically over the region of the tattoo under observation of a clinician; the treatment clinician would not need to manually hold and control a laser source over the tattoo site and could instead monitor the progress of the treatment as undertaken automatically by the apparatus.

Graffiti Removal

Similar to the tattoo removal, the apparatus could form an automatic graffiti removal system where the graffiti is imaged onto the detector 40 configured as a camera and an erasing laser beam 7 directed onto the pigment/paint of the graffiti.

Dipping Headlights The apparatus could comprise part of the headlight system of a vehicle wherein the detector 40, configured e.g. as a camera located behind the Sight emitter 20 surveys the roadway in front of the vehicle at all times. This might obviate the need for a dashboard mounted camera and could also assist with automated steering / collision detection. The light 7 projected from the light emitter could be both an illumination beam as well as for object detection (e.g. in the infrared) and the light source output could dimmed for e.g. an oncoming vehicle.

Structured Lighting

By projecting a light pattern of a specific form such as an array of lines, it is possible to determine the surface contour of the target surface 2 by comparing the nature of the pattern of the projected light 7 from the source 10 with the pattern observed by the detector 40 configured as a camera.

For example, by projecting a series of horizontal lines onto a target surface 2, the observation of curved lines would indicate a hollow or bump present in the surface.

The processor 50 could fine tune the structured light projection onto the target surface 2 until the specific details of the surface contour have been mapped and contoured. In principle, this could be implemented very rapidly due to the control loop between camera 40, processor 50 and light source 10.

Intelligent Smart Lamp System

The apparatus wherein the detec tor 40 is configured as a camera can be used in the home to assist with medical diagnostics and treatments all via a single instrument. For example, the patient at home may direct the emitted light 7 to the skin and take a photograph using the integral camera 40 in the system, so that the clinician can download the light emission settings for the light source 40 to the processor 50 which controls the light source to carry out the treatment at home. The processor can monitor the treatment and store or transmit to the clinician a record, e.g. a video of the treatment process.

IN SUMMARY, a preferred embodiment provides a combined light projection and detection apparatus comprising a light emitter 20 and a detector 40. The light emitter 20 preferably comprises a spherical, lensed body 24 containing a reflector 23. The light emitter receives light 7, preferably via a waveguide 60 from a light source 10 controlled by a processor 50, and projects the light 7 along a projection axis XP onto a target surface 2. The target surface 2 is observed bytne detector 40, e.g .a camera, which preferably receives light 8 along the same projection axis XP. The projected light 7 may comprise a pattern or image which is modified by the processor 50 to provide a semantic lighting system, e.g . for playing virtual chess on a target surface. The light source may comprise an array of light emitting elements 11, e.g. LEDs, which are individually adjusted to obtain an even radiant intensity over the target surface 2, e.g. for photodynamic therapy. In alternative embodiments, the first lens 21 may be arranged at a fixed distance from, or in contact with the exit end surface of the waveguide.

The reflector may be flat as shown or curved, for example, convexly or concavely curved. It may be specular or diffuse or Lambertian. Two or more reflectors with different shape or reflective surface characteristics may be provided, optionally back-to-back, so that by rotating the light emitter to position different ones of the reflectors in the optical pathway the focus or other characteristics of emitted beam may be altered as required. The transparent body of the light emitter may similarly include correction plates or different regions producing different optical effects.

Additional illumination waveguides or light sources may be located adjacent to the detector 40, optionally concentrically with respect to the detector. The detector may include a radiometric detector or sensing element such as a spectrometer. The system could operate in ultraviolet, visible and infrared regions of the spectrum as desired. It will be understood that the light 8 radiating from the target area may not necessarily be derived from the light 7 projected from the light source 10, but could be for example ambient light such as daylight, fluorescent light, or light emitted by a radiant light source in the target area, e.g. a visible light source, a hot plate, or a li-fi transmitter for communications purposes. The novel system may incorporate general lighting, communications, signalling, and sensing functions as required.

In alternative embodiments, the lighting device may comprise a plurality of selectively interchangeable light emitters, each of which has different optical properties. For example, different light emitters may have differently shaped lenses or reflectors to change the focal length or other parameters of the optical system. Different ones of the transparent bodies may be more or less transparent or diffusive. Different ones of the reflectors 23 may be respectively specular and Lambertian. Where the light emitter is mounted in a circular aperture in a support element, the light emitter may be simply lifted out of the aperture and replaced with another light emitter to provide the required effect.

The optical body 24 is preferably spherical but may be spheroidal. For example, it may be an oblate or prolate spheroid or an asphere (which is to say, nearly but not quite spherical). It may be ovoidal (egg shaped). In this specification, the term "substantially spherical" means generally ball-shaped with spherical or nearly spherical (e.g. spheroidal or ovoidal) curvature over all or nearly all of its surface.

In yet further alternative embodiments, the transparent body of the light emitter need not be substantially spherical. It could include a spherically or non-spherically curved surface which is slidably mounted for rotation on a support element so as to provide rotation with one or more degrees of freedom. For example, the light emitter could be hemispherical, or could be cylindrical and mounted for rotation in a rectangular aperture in a support element.

The or each reflector is preferably fixed in relation to the transparent body of the light emitter, although an adjustable mounting could be provided if required. In further alternative embodiments, the reflector or reflectors could be arranged externally of the transparent body, for example, as a surface coating or a solid shell or mirrored plate.

In the illustrated examples the Iight7 from the light source leaving the second lens 22 travels directly to the target surface 2 along the projection axis XP, with the reflected light 8 from the target surface travelling directly back along the same pathway. In alternative embodiments, an additional reflector or other optical elements may be arranged anywhere in the optical pathway, e.g. between the second lens 22 and the target surface 2. In alternative embodiments, rather than combining the lenses and reflector in a unitary optical body 24, the light emitter 20 could be formed as an assembly of separate elements including one or more lenses and optionally a reflector. The first and second lenses may be configured as a converging system comprising individual, single or compound lenses, for example, biconvex lenses, optionally with spherical curvature, arranged in the optical pathway respectively before and after the reflector. The reflector may be rotatable with respect to the or each lens, either as a moving element within a transparent optical body defining the lenses or as part of an assembly in spaced relation to the separate lenses.

The light source 10 could transmit light directly to the light emitter 20 without using a waveguide.

In a yet further embodiment, referred to below as the laser tracking embodiment, an apparatus for projecting and detecting light on a target surface comprises a light source, a light emitter for directing iight from the light source onto the target surface, and a detector for detecting light from the target surface. The Iight emitter comprises first and second lenses and a reflector, which are arranged in mutually fixed relation, and the Iight emitter is rotatable relative the Iight source to move the Iight from the Iight source over the target surface. In this embodiment, the Iight source is a laser Iight source, and the apparatus further includes a processor and an actuator. Laser Iight from the laser Iight source passes through the first lens to the reflector and then from the reflector through the second lens to the target surface, said Iight from the Iight source leaving the second lens along a projection axis. The Iight from the target surface entering the second lens along the projection axis passes through the second lens to the detector. The processor is arranged to receive a signal from the detector representing the Iight received from the target surface and, by said signal, to confirm or detect the alignment of the projection axis with the target surface. The actuator is controllable by the procesor to rotate the Iight emitter to direct the laser Iight onto the target surface as the target surface moves. The processor may confirm the alignment of the projection axis with the target surface, for example, by determining the presence or absence, or intensity, or wavelength, or pattern, or modulated signal, or a time delay between transmission and reflection, or any other measurable parameter, of the Iight received from the target surface. The Iight from the target surface entering the second lens along the projection axis may pass through or around the reflector and then through a third lens to the detector. For example, the Iight may pass through a partially transmissive reflector, for example, in an arrangement such as shown in Fig. 3, or may pass through an aperture in the reflector, for example, in an arrangement such as shown in Fig. 10, or may pass around the reflector in a catadioptric arrangement, for example, as shown in Fig. 2 or any of Figs. 4 - 9.

The laser light may impinge on the target surface, for example, to illuminate the target surface to act as a tracking signal which can be detected as an emission from the target surface, e.g .by another moving apparatus so as to guide the other apparatus towards the target surface, or to exert an energetic effect to degrade the target surface.

The light source may be arranged to emit the laser light at a first, higher intensity (for example, for degrading the target surface) and a second, lower intensity (for example, for tracking or illuminating the target surface).

The actuator may be arranged to rotate the light emitter with at least two degrees of freedom about a centre of rotation, so that the emitted beam can be scanned over a 2-D or 3-D target surface facing the light emitter.

Optionally, the processor may be arranged to receive a signal from the detector representing the light received from the target surface and, by said signal, to track movement of the target surface relative to the light emitter. In this way, the movement of the light emitter is controlled by the processor responsive to the light received by the detector.

The projected beam of laser light may be projected as a static pattern or moved across the target surface to produce a static or moving pattern on the target surface, so that the distortion of the known pattern produced on the surface and represented by the signal from the detector represents a 3-D contour of the target surface.

The processor may be arranged to analyse the signal from the detector to obtain an image of the target surface, for example, as said 3-D contour, and to iteratively compare a first such image with subsequent such images at successive time intervals and, by said comparison, to identify a direction of movement of the target surface so as to track the movement of the target surface. The detector may be configured as a camera, and may include, for example, as an array of detection elements angularly offset with respect to the projection axis, or to be angularly moveable around the light emitter with respect to the projection axis, or as an array of detection elements with the array being angularly moveable about the light emitter with respect to the projection axis. In each case the detector may receive light from the target surface which enters the second lens along the projection axis and along one or more detection axes, the or each detection axis being arranged to define a small angle with the projection axis. The processor may thus obtain an image of the target surface simultaneously or nearly simultaneously from multiple angles in a close array, and by iteratively obtaining and comparing the multiple images, may identify the direction of movement of the target surface.

Alternatively, the detector may be fixed in relation to the light emitter so that by moving the light emitter through a small angle about a mean or nominal position of the projection axis, the detector may detect light entering the second lens along the projection axis to obtain said multiple images in multiple different angular positions of the light emitter. By rapidly moving the light emitter, the multiple images may be generated and compared to track the movement of the target surface.

Alternatively or additionally, the light source may be arranged to modulate the laser light with a signal, and the detector may be arranged to detect the signal which is analysed by the processor (e.g. as a time interval between transmission and reflection of a defined signal element) to determine the distance from the light emitter to the target, whereby the processor may determine movement of the target surface towards or away from the light emitter. Instead of or additionally to controlling movement responsive to the light received by the detector, a separate tracking system (for example, a radar system) may be arranged to track movement of the target surface and send a signal to the processor which controls the movement of the light emitter. In this case, the signal received from the detector serves to confirm the correct alignment of the projection axis with the moving target surface, so that the emitted laser light may be selectively controlled to impinge on the target surface but not on any other surface. For example, the processor may control the light source to interrupt or reduce the intensity of the emitted laser light if the processor detects that the emitted beam ceases to be reflected from the target surface or is reflected from a surface other than the target surface. This concludes the description of the laser tracking embodiment, which may be implemented for example in an arrangement generally as shown and described with reference to Fig. 5. In each embodiment of the present invention, and as exemplified by the illustratrated examples, a light emitter comprising first and second lenses and a reflector may be arranged so that the light (7) from the light source entering the light emitter passes through the first lens to the reflector, and then some or a ll of said light is reflected from the reflector before it leaves the light emitter through the second lens (22) to impinge on the target surface. I n some embodiments, all, or substantially all, or most of the light entering the light emitter is reflected by the reflector before it leaves the light emitter through the second lens to impinge on the target surface. In other embodiments (as exemplified by Figs. 9 and 10), a first part of the light entering the light emitter is reflected by the reflector before it leaves the light emitter through the second lens to impinge on the target surface, and another part of the light entering the light emitter passes through or around the reflector, without being reflected by the reflector, before it leaves the light emitter through the second lens to impinge on the target surface. I n each case, it will be understood of course that the target surface is external to the light emitter.

It will be understood that generally in this specification, references to radiant intensity may be construed as either total radiant intensity or spectral radiant intensity. For example, where the apparatus is configured to detect light of a particular wavelength or to analyse the spectral distribution of light on the target surface and emit light of a target wavelength, the apparatus may be configured to adjust the spectral radiant intensity of the light emitted from each light emitting element, which is to say, the radiant intensity of the light emitted in the target wavelength.

The features of the various aspects and embodiments of the invention may be combined together in any desired combination. Further possible adaptations within the scope of the claims wili be apparent to those skilled in the art.

In the claims, reference numerals and characters in parentheses are provided for ease of reference and should not be construed as limiting features.