Contact force sensor and input system

Abstract

A contact force sensor is disclosed which indicates the location and magnitude of a contact force on the input surface of the sensor. The sensor may be used to provide an input to a computer processor and may be used in the fields of robotics, teleoperation, AR or VR. Contact force sensor (200) comprises input layer (210), emission layer (220), transmission layer 230 and masking layer (240). The input layer (210) and emission layer (220) are deformable when the contact force is applied. The emission layer (220) is configured to emit electromagnetic radiation (e.g. light). The transmission layer (230) is also deformable and transmits the electromagnetic radiation received from the emission layer (220) to a plurality of projections (231) which project through the masking layer (240). The projections are the output points on the output surface of the sensor. The deformation of the transmission layer caused by the application of a force to the input layer (210) causes a change in the intensity of electromagnetic radiation transmitted to at least one of the output points closest to the point of application of the contact force on the sensor. The location of the changed intensity and the relative change of the intensity provides the indication of the location and magnitude of the contact force received by the input surface of the sensor.

Description

[0001] Contact Force Sensor and Input System

[0002] Technical Field

[0003] The present invention relates to a contact force sensor which indicates the location and magnitude of a contact force on the input surface of the sensor. The sensor may be used to provide an input to a computer processor and may be used in the fields of robotics, teleoperation, augmented reality (AR) or virtual reality (VR).

[0004] Background

[0005] With the growth of robots in the fields of medical treatment, nursing, and industrial processing, the demand for interaction between humans and robots has gradually increased. It is desirable that robots have perception capabilities such as vision and touch to improve their ability to interact with humans. In recent years, although visual sensing has enabled robots to have observation capabilities similar to human eyes, the acquisition of physical interaction data is still lacking. As one of the important communication methods in human-robot interaction, touch is an important way for robots to achieve flexible operation and perception of the surrounding environment. Specifically, there is a need for tactile sensing technology that has a large area of sensing, high resolution and accuracy at a low cost.

[0006] Although the tactile sensor of the invention is particularly useful in the field of robotics, the sensor may be useful in any application where the location and magnitude of a contact force applied to the sensor can be converted into an input to a device.

[0007] Summary of the Invention

[0008] In accordance with a first aspect, the invention provides a contact force sensor configured to receive a contact force as an input on one, input surface of the sensor and to provide an indication of the location and magnitude of the contact force on the opposite, output surface of the sensor, the contact force sensor comprising: an emission layer configured to emit electromagnetic radiation, and a deformable transmission layer configured to transmit electromagnetic radiation received from the emission layer to at least one of a plurality of output points on the output surface of the sensor, wherein the sensor is configured to deform at the point of application of the contact force which deforms the transmission layer and causes a change in the intensity of electromagnetic radiation transmitted to the at least one of the plurality of output points closest to the point of application of the contact force on the sensor, and wherein the location of the changed intensity and the relative change of the intensity of electromagnetic radiation on the output surface of the sensor provides the indication of the location and magnitude of the contact force received by the input surface of the sensor.

[0009] The contact force sensor may also be referred to as a tactile sensor.

[0010] In some embodiments, the transmission layer is immediately adjacent the emission layer although this is not essential and there could be a spacer layer or another layer between. The main requirement is that the transmission layer receives the electromagnetic radiation from the emission layer.

[0011] The relative change in the intensity of the electromagnetic radiation when a contact force is applied could be an increase or a decrease in intensity. The change could be an increase from zero or a decrease to zero. In a preferred embodiment, the change is from one intensity to another intensity, either increased or decreased.

[0012] The sensor may be constructed from a plurality of layers. For the purpose of describing features or properties of the sensor, the x- and y-directions are considered to be in the plane of the layers and the z-direction is orthogonal to the plane of the layers. In some embodiments, the sensor is generally thin (in the z-direction) relative to the x and y dimensions. The sensor as a whole may be generally planar but it could alternatively be formed with a specific shape, such as curved, cylindrical or spherical, or any other shape which is required for the given application.

[0013] In general, a contact force received on one side of the sensor (the input surface) is converted into a changed intensity of electromagnetic radiation which is emitted on the other side of the sensor (the output surface). This provides an indication of the location of the contact force, which on the output surface is the point closest to the point of application of the contact force on the input surface in the x and y directions, spaced by a distance in the z direction (i.e. typically spaced by the z-dimension of the sensor, i.e. the sensor thickness). The indication of the magnitude of the contact force is determined by the relative change in the intensity of the electromagnetic radiation. The relevant force indicated by the sensor is the force in the z-direction, or the component of the force applied to the input surface in the z-direction.

[0014] As mentioned above, the sensor is configured to deform at the point of application of the contact force which deforms the transmission layer and causes a change in the intensity of electromagnetic radiation. Preferably, at least the transmission layer deforms but other layers, such as the emission layer, may also deform on application of the contact force. The other layers may be flexible such that they accommodate the deformation of the transmission layer. The sensor as a whole may deform. The deformation may be bending / flexing and / or compression of the relevant layer or the sensor. The deformation is preferably at least in the z-direction.

[0015] In some embodiments, the input surface may be formed by the emission layer, the transmission layer or another layer. In a preferred embodiment, the sensor further comprises an input layer forming the input surface of the sensor which is configured to receive the contact force in use. The input layer is preferably deformable (e.g. flexible and / or compressible) and is preferably made of silicone. In a preferred embodiment, the input layer is a thin, opaque layer. A preferred material is commercial silicone of shore hardness 30 (such as Ecoflex 0030) mixed with black pigment.

[0016] The emission layer may be any suitable layer which emits electromagnetic radiation. In some embodiments, the emission layer emits electromagnetic radiation via electroluminescence. In a preferred embodiment, the emission layer is an electroluminescent panel. In another embodiment, the emission layer is a stretchable electroluminescent device. In some embodiments, the emission layer emits electromagnetic radiation across a continuous section of surface area or substantially the entire surface area of the layer when connected to a power source. Preferably, the emission layer is thin, flexible and optionally stretchable. The panel may deform on application of the contact force. The emission layer may emit visible light or infra-red electromagnetic radiation. Preferably the emission layer emits light in the visible spectrum.

[0017] In some embodiments, the transmission layer is configured to deform at least in the z-direction (thickness direction) of the sensor. The transmission layer may be bendable / flexible and / or compressible at least in the z-direction (thickness direction) of the sensor. In a preferred embodiment, the transmission layer is resilient and is preferably made from silicone. The transmission layer may be soft and / or stretchable. A preferred material for the transmission layer is commercial silicone of shore hardness 30 (such as Ecoflex 0030) mixed with white pigments mixed in varying proportions to control the transmittance of the layer.

[0018] In some embodiments, the output surface includes the plurality of output points where the electromagnetic radiation may be transmitted from the sensor. The sensor may further comprise an output layer adjacent to the output surface of the sensor. The output layer may be an additional electromagnetic radiation-transmissive layer adjacent to the output surface, such as a clear acrylic or silicone layer.

[0019] In a preferred first embodiment, the emission layer is configured to receive the contact force on a first surface and to emit electromagnetic radiation on a second surface opposite the first surface, the emission layer is configured to deform at the point of application of the contact force on the emission layer which deforms the transmission layer, and the transmission layer has a first surface configured to receive the electromagnetic radiation from the second surface of the emission layer, and wherein the transmission layer is configured to transmit the electromagnetic radiation to the at least one of the plurality of output points closest to the point of application of the contact force on the sensor.

[0020] In this embodiment, the transmission layer transmits the electromagnetic radiation from the emission layer to the output surface of the sensor at the point of deformation. The emission layer is configured to deform at the point of application of the contact force on the emission layer, the deformation preferably being at least in the z-direction. The deformation of the emission layer deforms (flexes and / or compresses) the transmission layer.

[0021] The sensor deformation brings the source of the electromagnetic radiation closer to the output surface, which causes an increase in the intensity of the electromagnetic radiation transmitted to the at least one of the plurality of output points closest to the point of application of the contact force on the sensor.

[0022] The transmission layer may form the output surface of the sensor. In a preferred embodiment, the sensor further includes a masking layer adjacent to the transmission layer comprising an opaque layer with a plurality of apertures forming the output points, through at least one of which the electromagnetic radiation is transmitted from the transmission layer. The masking layer may be opaque, thin, flexible and / or compressible. A preferred material for the masking layer is commercial silicone of shore hardness 30 (such as Ecoflex 0030) mixed with black pigment.

[0023] The apertures may be any suitable shape - e.g. square, rectangular, circular. The size and spacing of the apertures are determined by configuration of sensor - shape, dimensions, distance from / location of camera, etc. - such that the aperture boundaries are discernible in the image.

[0024] In a preferred embodiment, the transmission layer includes a plurality of projections which project from a second surface of the transmission layer opposite the first surface, and wherein the transmission layer is configured to transmit the electromagnetic radiation from the emission layer through the projections on the second surface to the output surface of the sensor. The output surface may be the projections themselves, such as a plane containing the ends of the projections. The masking layer may or may not be present when the transmission layer includes projections. If the masking layer is present, the projections of the transmission layer may project into and optionally through the apertures of the masking layer.

[0025] The projections preferably project in the z-direction from the second surface of the transmission layer to the output surface. They may comprise the same material as the transmission layer or be formed from a different material. The projections may have any suitable shape, such as pyramidal, conical, hemispherical, cylindrical, dome-shaped. The size and spacing of the projections may be determined by configuration of sensor - shape, dimensions, distance from / location of camera, etc. - such that there is no occlusion of projections in the image. A typical size (in the z-direction) is about 3mm.

[0026] In a preferred second embodiment, the contact force sensor further comprises a reflective layer configured to receive the contact force on a first surface and to deform at the point of application of the contact force which deforms the transmission layer, wherein the reflective layer has a reflective surface on a second surface opposite the first surface, the transmission layer is located between the reflective layer and the emission layer, and the emission layer is configured to emit electromagnetic radiation on a first surface towards the transmission layer and wherein the emission layer further comprises a plurality of apertures forming the output points, through at least one of which reflected electromagnetic radiation is transmitted from the transmission layer, the arrangement being such that the electromagnetic radiation is transmitted from the emission layer, through the transmission layer, reflected back by the reflective surface of the reflective layer, through the transmission layer and through the at least one aperture forming an output point closest to the point of application of the contact force on the sensor.

[0027] The reflective layer is configured to deform (bending / flexing and / or compression) at the point of application of the contact force on the emission layer, the deformation preferably being at least in the z-direction. The deformation of the reflective layer deforms (flexes and / or compresses) the transmission layer.

[0028] The sensor deformation reduces the distance between the effective source of electromagnetic radiation (i.e. the reflective layer) and the output surface, and changes the shape of the reflective layer opposite the relevant emission layer aperture, which reduces the amount of electromagnetic radiation reflected and thereby causes a reduction in the intensity of the electromagnetic radiation transmitted through the emission layer aperture to the at least one of the plurality of output points closest to the point of application of the contact force on the sensor.

[0029] The reflective layer is preferably opaque, soft and / or stretchable. A preferred material is commercial silicone of shore hardness 30 (such as Ecoflex 0030) mixed with a relatively high concentration of white pigment to cause reflection.

[0030] In this embodiment, the apertured emission layer effectively forms a masking layer adjacent to the transmission layer comprising an opaque layer with a plurality of apertures forming the output points, through at least one of which the reflected electromagnetic radiation is transmitted from the transmission layer.

[0031] The second surface of the transmission layer may be flat or may comprise a plurality of projections as above which project from the second surface. The projections may project into or through the apertures of the emission layer. The size and configuration of the apertures and projections may be the same as described above for the masking layer and transmission layer respectively.

[0032] The invention may also provide an input system comprising the contact force sensor described above and a detector to detect the electromagnetic radiation at the output surface, wherein the detector outputs data relating to the indication of the location and magnitude of the contact force on the input surface of the sensor based on the location of the changed intensity and the relative change of the intensity of electromagnetic radiation on the output surface of the sensor. The detector may comprise a camera. The system may comprise more than one detector or camera.

[0033] In a preferred embodiment, the input system is configured to provide the data relating to the indication of the location and magnitude of the contact force on the input surface of the sensor to a robot or to a prosthesis.

[0034] In a preferred embodiment, the input system is configured to provide the data relating to the indication of the location and magnitude of the contact force on the input surface of the sensor to a computer processor. The sensor may be used in the fields of robotics, teleoperation, AR or VR.

[0035] At least in preferred embodiments, the invention provides a vision-based tactile sensor. By employing an electroluminescent panel or device directly embedded inside the silicone layers of the sensor, reflection e.g. inside a tubular sensor is reduced or minimised. Internal reflection may be an issue for other techniques employing analysis of displacement of markers illuminated by light sources (e.g. LED) to estimate force.

[0036] Brief Description of the Drawings

[0037] Embodiments of the invention will now be described by way of example only and with reference to the accompanying drawings, in which:

[0038] Fig. 1 shows a schematic, part-sectional view of a contact force input system in accordance with the invention;

[0039] Fig. 2 shows an exploded schematic view of a contact force sensor in accordance with a first embodiment which may be employed in the contact force input system of Fig. 1;

[0040] Fig. 3 shows an exploded schematic view of a contact force sensor in accordance with a second embodiment which may be employed in the contact force input system of Fig. 1;

[0041] Fig. 4 illustrates the principle of operation of the second embodiment of Fig. 3;

[0042] Fig. 5A shows an external view of the contact force input system of Fig. 1 with a user applying a contact force to the external surface of the sensor;

[0043] Figs. 5B and 5C show internal views of the contact force input system of Fig. 5A, with no force applied and with the force applied in Fig. 5A respectively;

[0044] Fig. 5D shows the visualisation of the sensor data; Fig. 6 shows data collected from a contact force sensor in accordance with the invention at various locations during calibration; and

[0045] Figs. 7A to 7D show examples of different configurations of contact force sensor in accordance with the invention.

[0046] Detailed Description of Preferred Embodiments

[0047] Fig. 1 shows a schematic, part-sectional view of a contact force input system 100 in accordance with the invention. The contact force input system may be used to provide input data (e.g. force position, magnitude) to a robot. The system in Fig. 1 is generally cylindrical in shape and may be used as part of a robotic arm. The contact force may be used to guide or move the robotic arm, so that the robot learns a specific movement for example.

[0048] Input system 100 comprises two flanges 110 at either end of a cylinder formed from the contact force sensor 200, 300 of the invention, discussed further below, which is formed around a cylinder 120 of a rigid transparent material such as a clear acrylic material. A schematic representation S of the contact force sensor is shown. A digital camera 130 is positioned at one end of the cylinder so that the internal sensor area (i.e. the output surface) can be seen in the image and processed.

[0049] Fig. 2 shows an exploded schematic view of a contact force sensor 200 in accordance with a first embodiment which may be employed in the contact force input system of Fig. 1. Contact force sensor 200 comprises input layer 210, emission layer 220, transmission layer 230 and masking layer 240. Acrylic layer 120 from Fig. 1 is shown in dashed lines.

[0050] Input layer 210 forms the input surface of the sensor which is configured to receive the contact force in use. In this embodiment, the input layer is deformable (e.g. flexible and / or compressible) and is a thin, opaque layer made from commercial silicone of shore hardness 30 (such as Ecoflex 0030) mixed with black pigment.

[0051] In this embodiment, emission layer 220 is an electroluminescent panel and emits electromagnetic radiation across substantially the entire surface area of the layer when connected to an electronic driving circuit. In this embodiment, the emission layer 220 is thin and flexible and also deforms on application of the contact force. The emission layer emits visible light. A suitable electroluminescent panel may be obtained from EL Wire Craft (www.elwirecraft.co.uk), although there are other commercially-available panels.

[0052] In this embodiment, the transmission layer 230 is resiliently deformable (flexible and / or compressible) in the z-direction (the thickness direction) of the sensor. The transmission layer is made from commercial silicone of shore hardness 30 (such as Ecoflex 0030) mixed with white pigments, mixed in varying proportions to control the transmittance of the layer.

[0053] In this embodiment, the sensor further includes a masking layer 240 adjacent to the transmission layer comprising an opaque layer with a plurality of apertures 241 forming the output points. The masking layer is made from commercial silicone of shore hardness 30 (such as Ecoflex 0030) mixed with black pigment. The apertures in this embodiment are substantially square.

[0054] The transmission layer 230 includes a plurality of pyramidal-shaped projections 231 which project from the second surface of the transmission layer into the apertures 241 of the masking layer 240. The projections 231 are preferably formed from the same material as the transmission layer 230 and are unitary with the transmission layer. The transmission layer is configured to transmit the electromagnetic radiation (visible light) from the emission layer through the projections on the second surface to the output surface of the sensor.

[0055] In this embodiment, the emission layer 220 receives the applied contact force via the input layer 210 on a first surface and emits electromagnetic radiation on a second surface. The emission layer is configured to deform at the point of application of the contact force, which in turn deforms the transmission layer 230. The transmission layer has a first surface which receives the electromagnetic radiation from the second surface of the emission layer and transmits the electromagnetic radiation to at least one of the projections 231, which in combination with the masking layer 240 form the output surface.

[0056] The sensor deformation brings the source of the electromagnetic radiation (the emission layer 220) closer to the output surface, which causes an increase in the intensity of the electromagnetic radiation transmitted to the projection or projections 231 closest to the point of application of the contact force on the sensor. These projection(s) will therefore appear brighter than the other projections. This indicates the location of the contact force. The difference in brightness compared to the other projections (i.e. the relative change in intensity), indicates the magnitude of the contact force.

[0057] Fig. 3 shows an exploded schematic view of a contact force sensor 300 in accordance with a second embodiment which may be employed in the contact force input system of Fig. 1. Contact force sensor 300 comprises input layer 310, reflective layer 320, transmission layer 330 and apertured emission layer 340. Acrylic layer 120 from Fig. 1 is shown in dashed lines.

[0058] Input layer 310 forms the input surface of the sensor which is configured to receive the contact force in use. In this embodiment, the input layer is deformable (e.g. flexible and / or compressible) and is a thin, opaque layer preferably made from commercial silicone of shore hardness 30 (such as Ecoflex 0030) mixed with black pigment.

[0059] The reflective layer 320 is also deformable (e.g. flexible and / or compressible) and is opaque, soft and / or stretchable. A preferred material is commercial silicone of shore hardness 30 (such as Ecoflex 0030) mixed with a relatively high concentration of white pigment to cause reflection. In this embodiment, the transmission layer 330 is resiliently deformable (flexible and / or compressible) in the z-direction (the thickness direction) of the sensor. The transmission layer is made from commercial silicone of shore hardness 30 (such as Ecoflex 0030) mixed with white pigments, mixed in varying proportions to control the transmittance of the layer

[0060] The apertured emission layer 340 in this embodiment is an electroluminescent panel which emits electromagnetic radiation across the majority of the surface area of the layer (apart from the edges and the apertures) when connected to a driving circuit. In this embodiment, the emission layer emits the electromagnetic radiation towards the transmission layer 330. The emission layer emits visible light. A supplier for an electroluminescent panel is mentioned above, and apertures may be milled into this panel. However, pre-apertured electroluminescent panels are also available commercially.

[0061] In this embodiment, the reflective layer 320 receives the applied contact force via the input layer 310 on a first surface. The input layer 310 and the reflective layer 320 are configured to deform (bending / flexing and / or compression) at the point of application of the contact force, the deformation preferably being at least in the z-direction. The deformation of the input layer 310 and the reflective layer 320 deforms (flexes and / or compresses) the transmission layer 330. The reflective layer 320 has a reflective surface facing the transmission layer 330. The apertured emission layer 340 emits electromagnetic radiation (visible light) on the surface facing towards the transmission layer 330, which is transmitted through the transmission layer 330, reflected back by the reflective layer, through the transmission layer again and through the apertures 341 of the emission layer 340. In this embodiment, the apertured emission layer 340 effectively forms a masking layer adjacent to the transmission layer 330.

[0062] The sensor deformation reduces the distance between the effective source of electromagnetic radiation (i.e. the reflective layer 320) and the output surface, and also changes the shape of the reflective layer 320, which reduces the amount of electromagnetic radiation reflected and thereby causes a reduction in the intensity of the electromagnetic radiation transmitted through the relevant emission layer aperture 341 to the at least one of the plurality of output points closest to the point of application of the contact force on the sensor. These aperture(s) will therefore appear dimmer than the other projections. This indicates the location of the contact force. The difference in brightness compared to the other projections (i.e. the relative change in intensity), indicates the magnitude of the contact force.

[0063] Fig. 4 illustrates the principle of operation of the second embodiment of Fig. 3. In 4(a), electromagnetic radiation from the apertured emission layer 340 passes through the transmission layer 330 and is reflected by reflective layer 320 to pass through the apertures 341. When pressure is applied, deformation changes the angles of incidence which reduces the amount of electromagnetic radiation emitted through the aperture at the point of pressure application. 4(b) shows images of the apertures before and after the application of pressure. The aperture at the point of pressure application shows a reduced intensity of electromagnetic radiation.

[0064] Figs. 5A-5D show the operation of the contact force input system of Fig. 1, with the first embodiment of contact force sensor of Fig. 2, i.e. in which the output electromagnetic radiation increases in intensity at the point of force application. However, the skilled person will understand that the principle of operation of the contact force input system with the second sensor embodiment of Fig. 3 will be very similar with appropriate technical changes to accommodate the decrease in intensity at the point of force application.

[0065] Fig. 5A shows a user applying a contact force to the external input surface 250 of the sensor 200 of the system 100. Fig. 5B shows the view inside the system, i.e. the internal / output surface 260 of the sensor 200 as seen by the digital camera 130, without a force being applied to the external surface. A plurality of output points 261 are shown, which generally all emit a similar intensity of light transmission when no force is applied to the external surface of the sensor. The output points may be grouped into defined areas, and / or more than one sensor may be employed in a contact force input system. The output points 261 further away from the camera may appear dimmer due to the distance and / or the angle of view. This can be factored into the image processing software. The output points in the dashed circle A in Fig. 5B all have the same light intensity.

[0066] Fig. 5C shows the same view as Fig. 5B, with a force being applied to the external surface of the sensor. Some of the output points 262 in the dashed circle A now have an increased intensity compared to the other projections 261. The location of these brighter projections indicates the location of the contact force and the relative increase in intensity compared to the other projections indicates the magnitude of the contact force.

[0067] Fig. 5D shows the visualisation of the sensor data. An image processing algorithm is employed which is based on monocular vision using intensity as the detection index to realise the location of the contact point and to estimate the force magnitude.

[0068] A skilled person would be able to use a spherical indenter of a diameter comparable to the aperture size and a load cell, and conduct measurements of an intensity feature calculated from the image captured by the camera for varying applied forces at various points on the input surface of the sensor. An example of the intensity feature is the average brightness of a set of pixels corresponding to the sensor output surface closest to the point of application of the force on the input surface of the sensor. The skilled person would be able to obtain a calibration function for force as a function of intensity and optionally, the position of the force application. An example of the data collected from the sensor at various locations using a spherical indenter of tip radius of 10mm and a commercial load-cell is shown in Fig. 6.

[0069] The skilled person will be able to develop a suitable method for image processing to realize force localization and estimation. An example method is to set a suitable intensity feature threshold in the image to identify where a force has been applied. The skilled person would then be able to calculate the real-world 3D co-ordinates corresponding to the pixel co-ordinates identified to complete the localization of applied force. The skilled person will then be able to use the intensity feature measurement at that set of pixels and the calibration curve to calculate the estimated force magnitude. Figs. 7A to 7D show examples of different configurations of contact force sensor in accordance with the invention. Fig. 7A shows a flat / planar sensor 200, 300. Fig. 7B shows a curved sensor 200, 300 with convex and concave portions. Fig. 7C shows a cylindrical / curved sensor and a circular, planar sensor on the same input system. Fig. 7D shows multiple sensors situated on the surface of a curved, three-dimensional dome-like structure.

Claims

Claims1. A contact force sensor configured to receive a contact force as an input on one, input surface of the sensor and to provide an indication of the location and magnitude of the contact force on the opposite, output surface of the sensor, the contact force sensor comprising: an emission layer configured to emit electromagnetic radiation, and a deformable transmission layer configured to transmit electromagnetic radiation received from the emission layer to at least one of a plurality of output points on the output surface of the sensor, wherein the sensor is configured to deform at the point of application of the contact force which deforms the transmission layer and causes a change in the intensity of electromagnetic radiation transmitted to the at least one of the plurality of output points closest to the point of application of the contact force on the sensor, and wherein the location of the changed intensity and the relative change of the intensity of electromagnetic radiation on the output surface of the sensor provides the indication of the location and magnitude of the contact force received by the input surface of the sensor.

2. The sensor of claim 1, wherein the sensor is flexible.

3. The sensor of claim 1 or 2, further comprising an input layer forming the input surface of the sensor which is configured to receive the contact force in use.

4. The sensor of claim 3, wherein the input layer is deformable and is preferably made of silicone.

5. The sensor of any preceding claim, wherein the emission layer is an electroluminescent panel.

6. The sensor of any of claims 1 to 4, wherein the emission layer is a stretchable electroluminescent device.

7. The sensor of claim 5 or 6, wherein the emission layer emits light in the visible spectrum.

8. The sensor of any preceding claim, wherein the transmission layer is configured to deform at least in the z-direction (thickness direction) of the sensor.

9. The sensor of claim 8, wherein the transmission layer is flexible or compressible at least in the z-direction (thickness direction) of the sensor.

10. The sensor of claim 8 or 9, wherein the transmission layer is resilient and is preferably made from silicone.

11. The sensor of any preceding claim, wherein the output surface includes the plurality of output points where the electromagnetic radiation may be transmitted from the sensor.

12. The sensor of any preceding claim, further comprising an output layer adjacent to the output surface of the sensor.

13. The sensor of any preceding claim, wherein: the emission layer is configured to receive the contact force on a first surface and to emit electromagnetic radiation on a second surface opposite the first surface, the emission layer is configured to deform at the point of application of the contact force on the emission layer which deforms the transmission layer, and the transmission layer has a first surface configured to receive the electromagnetic radiation from the second surface of the emission layer, and wherein the transmission layer is configured to transmit the electromagnetic radiation to the at least one of the plurality of output points closest to the point of application of the contact force on the sensor.

14. The sensor of claim 13, further including a masking layer adjacent to the transmission layer comprising an opaque layer with a plurality of apertures forming the output points, through at least one of which the electromagnetic radiation is transmitted from the transmission layer15. The sensor of claim 13 or 14, wherein the transmission layer includes a plurality of projections which project from a second surface of the transmission layer opposite the first surface, and wherein the transmission layer is configured to transmit the electromagnetic radiation from the emission layer through the projections on the second surface to the output surface of the sensor.

16. The sensor of claim 14 and 15, wherein the projections of the transmission layer project into and optionally through the apertures of the masking layer.

17. The sensor of any of claims 1 to 12, wherein: the contact force sensor further comprises a reflective layer configured to receive the contact force on a first surface and to deform at the point of application of the contact force which deforms the transmission layer, wherein the reflective layer has a reflective surface on a second surface opposite the first surface, the transmission layer is located between the reflective layer and the emission layer, and the emission layer is configured to emit electromagnetic radiation on a first surface towards the transmission layer and wherein the emission layer further comprises a plurality of apertures forming the output points, through at least one of which reflected electromagnetic radiation is transmitted from the transmission layer, the arrangement being such that the electromagnetic radiation is transmitted from the emission layer, through the transmission layer, reflected back by the reflective surface of the reflective layer, through the transmission layer and through the at least one aperture forming an output point closest to the point of application of the contact force on the sensor.

18. The sensor of claim 17, wherein the apertured emission layer forms a masking layer adjacent to the transmission layer comprising an opaque layer with a plurality of apertures forming the output points, through at least one of which the reflected electromagnetic radiation is transmitted from the transmission layer.

19. The sensor of claim 17 or 18, wherein the transmission includes a plurality of projections which project into or through the apertures of the emission layer.

20. An input system comprising the contact force sensor of any preceding claim and a detector to detect the electromagnetic radiation at the output surface, wherein the detector outputs data relating to the indication of the location and magnitude of the contact force on the input surface of the sensor based on the location of the changed intensity and the relative change of the intensity of electromagnetic radiation on the output surface of the sensor.

21. The input system of claim 20, wherein the detector is a camera22. The input system of claim 20 or 21, wherein the input system is configured to provide the data relating to the indication of the location and magnitude of the contact force on the input surface of the sensor to a robot or to a prosthesis.

23. The input system of claim 20, 21 or 22, wherein the input system is configured to provide the data relating to the indication of the location and magnitude of the contact force on the input surface of the sensor to a computer processor.

Images