WO2019073424A1

WO2019073424A1 - A deformation sensing device, apparatus and system

Info

Publication number: WO2019073424A1
Application number: PCT/IB2018/057870
Authority: WO
Inventors: Poul Michael Fonss Nielsen
Original assignee: Auckland Uniservices Limited
Priority date: 2017-10-11
Filing date: 2018-10-10
Publication date: 2019-04-18

Abstract

A sensing device (200) for sensing deformations is disclosed. The sensing devices (200) comprises an optical source (204), an optical sensor (206) and a waveguide (202). The optical source (204) is configured to emit light of at least two wavelengths or at least two frequencies. The waveguide (202) includes an inlet (220) and an outlet (222). The optical source (204) is positioned at or adjacent an inlet (220). The optical sensor (206) is positioned at or adjacent an outlet (222). The waveguide (202) is configured to transmit light emitted by the optical source (204) to the optical sensor (206). The sensing device (200) is configured to indicate, or generate a signal indicative of a deformation of a portion of the sensing device (200) based on a relationship of at least two wavelengths or at least two frequencies.

Description

A DEFORMATION SENSING DEVICE, APPARATUS AND SYSTEM

FIELD OF THE INVENTION

The present invention relates to a sensing device, apparatus and system, particularly to a sensing device, apparatus and system for detecting or indicating deformation.

BACKGROUND

Flexible deformation sensors (i.e. strain sensors) currently exist and are used to measure deformations due to applied forces. Many currently used flexible deformation (i.e. strain) sensors are mostly electrical, transducing mechanical deformations into electrical signals. For example, resistive transducers are typically constructed from electrically conductive sensing films coupled to flexible substrate. Another example of a current flexible strain sensor is a capacitive transducer. A capacitive transducer uses a compliant dielectric layer sandwiched between two stretchable electrodes. Both of these types of sensors transduce a mechanical deformation i .e. strain into a corresponding electrical signal. These methods typically suffer from several disadvantages. For example, such sensors require relatively complicated fabrication, are susceptible to electronic interference, have highly nonlinear responses, have limited stretchability, and also provide poor repeatability.

Soft stretchable sensors have also become more commonplace for use in several applications such as for example in soft robotics. Soft sensors that have been developed have utilised a range of polymer materials such as for example Polydimethylsiloxane (PDMS) and silicone rubbers. Conductive liquids have been a commonly used as a material in the construction of soft sensors due their conductive ability as well as being soft and highly deformable. The conductive liquid channels in these type of soft sensors can be used as a sensing element by changing their electrical resistance when the host material deforms. These conductive liquid type stretch sensors have several limitations such as for example encapsulation of the conductive liquid. These sensors often need complex construction to adequately encapsulate and contain the conductive liquid.

Further these type of sensors can be difficult and expensive to manufacture. Finally, these sensors may not be biocompatible. Although these conductive liquids are not generally considered toxic they can be dangerous if they come into contact with the human body, and further there is the risk of these liquids leaking from the sensor.

Stretchable optical waveguides have also been used as flexible deformation (i.e. strain sensors). WO2017/015563 is an example of a document that discloses the use of a flexible and stretchable sensor using a soft optical waveguide to detect deformations. The document discloses using a waveguide and a flexible housing made of silicone rubber. The waveguide is encapsulated with an outer layer e.g. a gold leaf layer. The sensor disclosed in WO2017/015563 detects deformation by measuring light that escapes the waveguide due to gaps or cracks opening within the gold leaf layer when the sensor is stretched.

US5, 044,205 discloses a method for monitoring deformations with light waveguides. US5, 044,205 also discloses a further sensor that uses a stretchable waveguide to detect or monitor deformations. The sensor includes a light source and a light conducting fibre that conducts light to a sensor. The deformation of the light guide is measured based on the damping effect on the light pulses which are sent through the light conducting fibre. The light guide or guides are pre-stressed such that they remain in tension at all expected levels of deformation.

The sensors described in the referenced documents still suffer from certain problems such as errors in determining deformation due to the inability of being able to measure light accurately, especially if the light source is remote from the sensitive region of the waveguide. Further there may be unknown losses that may occur in the waveguide especially if the waveguide is subject to large deformations. Therefore, accuracy of deformation detection or measurement can be a challenge using sensors that simply rely on detecting the change in light intensity. Finally, at least some of these devices are also susceptible to inaccuracies due to spacing between the waveguide and the light source and inaccuracies due to the difficulty in accurately measuring the light intensity arriving at the sensitive region. These sensors can be greatly affected by variation in the intensity of the light from the light source, and these sensors require very accurate source intensity. This can make their use limited in some instances and can lead to increased inaccuracy that needs to be compensated.

In this specification where reference has been made to patent specifications, other external documents, or other sources of information, this is generally for the purpose of providing a context for discussing the features of the invention. Unless specifically stated otherwise, reference to such external documents or such sources of information is not to be construed as an admission that such documents or such sources of information, in any jurisdiction, are prior art or form part of the common general knowledge in the art.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a sensing device apparatus and/or system for sensing deformations that goes some way to overcoming at least one of the above mentioned disadvantages, or which at least provides the public with a useful choice. In a first aspect, the present invention resides in a sensing device for sensing deformations comprising :

an optical source emitting light of at least two wavelengths; an optical sensor; and

a waveguide including an inlet and an outlet,

wherein the optical source positioned at or adjacent an inlet of the waveguide,

the optical sensor positioned is at or adjacent an outlet,

the waveguide configured to transmit light emitted by the optical source to the optical sensor, and

the sensing device is configured to indicate, or generate a signal indicative of a deformation of a portion of the sensing device based on a relationship of the at least two wavelengths or the at least two frequencies.

In one configuration the deformation of a portion of the sensing device is based on a relative relationship of the at least two wavelengths or the at least two frequencies. In one configuration the relationship is a ratio of intensities of the at least two wavelengths or the at least two frequencies of light.

In one configuration the relationship is a change in intensities of the at least two wavelengths or the at least two frequencies of light.

In one configuration the deformation is related to a ratio of intensities of the at least two wavelengths or the at least two frequencies of light.

In one configuration the deformation detected by the sensing device is a single axis deformation.

In one configuration the optical source comprises a broadband optical source configured to emit white light. In one configuration the optical source is a broadband LED or a broadband diode laser. In one configuration the optical sensor comprises one or more wavelength sensitive optical sensors.

In one configuration the optical sensor comprises one or more wavelength sensitive photodetector. In one configuration the optical source comprises at least two optical sources, each optical source emitting light comprising a single wavelength or single frequency.

In one configuration the optical source comprises a multi-wavelength optical source configured to generate light of the at least two wavelengths or at least two frequencies. In one configuration the optical sensor is a wavelength insensitive optical sensor.

In one configuration the optical sensor is a wavelength insensitive photodetector.

In one configuration the waveguide is resiliently deformable.

In one configuration the waveguide comprises a coloured region, the coloured region partially absorbing or attenuating light of one or more frequencies or one or more wavelengths.

In one configuration the coloured region forms a sensitive region and a deformation of the coloured region is determined based on the relationship of the at least two wavelengths or the at least two frequencies.

In one configuration the waveguide is an elongate, hollow member. In one configuration the waveguide comprises a substantially circular or rectangular or triangular or oval shaped cross section.

In one configuration the waveguide comprises an inner layer and an outer layer encasing the inner layer, wherein the inner layer comprises a higher refractive index than the outer layer. In one configuration the inner layer is a tubular core or planar sheet.

In one configuration the waveguide may be folded or bent such that the optical source and optical sensor are collocated. In one configuration the optical source and the optical sensor may be co-located or located adjacent each other.

In one configuration, the optical source and optical sensor may be positioned on a common Printed Circuit Board (PCB). In one configuration the waveguide comprises a reflective member positioned within it such that light received at the inlet from the optical source reflects off the reflective member and is directed to the outlet for detection by the optical sensor such that optical source and the optical sensor are located adjacent each other.

In one configuration the waveguide comprises a substantially transparent or substantially translucent material.

In one configuration the waveguide comprises a silicone or a polyurethane or an elastomer material or a liquid contained in a solid elastomeric tube.

In one configuration, the solid tube is an elastomeric tube.

In one configuration the light emitted by the optical source is in a visible light spectrum.

In one configuration waveguide may comprise one or more transparent regions disposed within a substantially opaque waveguide.

In one configuration the sensing device as hereinbefore described is configured to detect a deformation that is an axial or linear deformation. In one configuration, the axial or linear deformation may be tension (i.e. stretch) or compression.

In one configuration the sensing device as hereinbefore described is configured to detect a deformation that is a single axis deformation.

In one configuration the optical source may be held adjacent or in contact with the waveguide.

In one configuration the sensing device further comprises a refractive member comprising a refractive index that is the same or similar to the refractive index of the waveguide, and wherein the optical source is positioned adjacent or embedded within the refractive member. In one configuration the member is positioned between the optical source and the waveguide such that light from the optical source is emitted into the waveguide through the refractive member.

In one configuration the waveguide may be clamped to the refractive member. In a second aspect, the present invention resides in a sensing device as hereinbefore described wherein the sensing device comprises:

a plurality of optical sources positioned at or adjacent the inlet of the waveguide; and

a plurality of optical sensors positioned at or adjacent the outlet of the waveguide,

wherein the sensing device configured to generate a signal indicative of a multi axis deformation or deformation about multiple axes based on a difference of light intensity measured by the plurality of optical sensors.

In one configuration the waveguide is a substantially cylindrical member comprising a circular cross section and pair of opposing planar faces.

In one configuration three optical sources are placed on one planar face, three optical sensors are positioned on an opposing planar face, the three optical sensors are located out of phase to the optical sources.

In one configuration the optical sensors are positioned 60 degrees out of phase with the optical sources.

In a third aspect, the present invention resides in a sensing apparatus for sensing deformation, the sensing apparatus comprising :

a plurality of sensing devices according to any one of the above statements disposed on or within a substrate,

wherein a deformation of the sensing apparatus being based on a relative deformation of each of the plurality of sensing devices.

In one configuration the deformation of the sensing apparatus is based on a comparative deformation of each sensing device relative to the other sensing devices within the sensing apparatus. In one configuration the plurality of sensing devices are arranged parallel to each other on or within the substrate material, wherein the sensing apparatus is configured to determine a bending deformation based on a relative deformation of each of the plurality of sensing devices.

In one configuration the plurality of sensing devices are arranged in a helical arrangement on or within the substrate, wherein the sensing apparatus is configured to determine a torsion deformation based on a relative deformation of each of the plurality of sensing devices.

In one configuration the plurality of sensing devices are arranged in a two dimensional array such that a plurality of sensing devices are arranged parallel to a first axis and a plurality of sensing devices are arranged parallel to a second axis wherein the first axis and second axis are transverse to each other.

In one configuration a flexible, reflective material is disposed on the two dimensional array of sensing devices.

In one configuration the sensing apparatus is configured to generate a signal indicative of a multi-axis deformation of the sensing apparatus, wherein the multi-axis deformation is determined based on the relative deformation of the sensing devices.

In a fourth aspect the present invention resides in a sensing device for sensing deformation, the sensing device comprising :

an optical source configured to emit a light of two or more wavelengths, or of two or more frequencies;

a light or optical sensor;

an optical guide for transmitting light emitted from the optical source to the light or optical sensor,

wherein the sensing device is configured to indicate or generate a signal indicative of a deformation of the sensing device or the optical guide based on one or more of:

I . a ratio of intensity of the two or more wavelengths or two or more

frequencies of light,

II . a change in the intensity of the two or more wavelengths of light or two or more frequencies of light,

II I . a relative attenuation of the two or more wavelengths of light or two or more frequencies of light,

IV. an attenuation ratio of the two or more wavelengths of light or two or more frequencies of light, v. a change in an attenuation ratio of the two or more wavelengths of light or two or more frequencies of light, and

vi. a change in attenuation of the two or more wavelengths of light or two or more frequencies of light. In a fifth aspect, the present invention resides in a sensing system for sensing deformation comprising :

a sensing device according to any one of the above statements; and a processor in electronic communication with the sensing device, wherein the processor is configured to receive a signal indicative of a deformation from the sensing device, and wherein the processor is further configured to determine a deformation based on a relationship of the at least two wavelengths or the at least two frequencies.

In a sixth aspect, the present invention c resides in a sensing device for sensing deformations, the sensing device comprising :

a source configured to emit electromagnetic waves of two or more wavelengths or two or more frequencies;

a sensor configured to detect the emitted electromagnetic waves; and a waveguide including an inlet and an outlet;

wherein the source is positioned at or adjacent the inlet of the waveguide, the sensor positioned at or adjacent the outlet of the waveguide, the waveguide configured to transmit the electromagnetic waves of the at least two wavelengths or two or more frequencies from the source to the sensor,

the sensing device configured to indicate or generate a signal indicative of a deformation of a portion of the sensing device based on a relationship of the two or more wavelengths or two or more frequencies.

In one configuration the deformation of a portion of the sensing device is based on a relative relationship of the two or more wavelengths.

In one configuration the relationship is at least one of:

i. a ratio of intensity of the at least two or more wavelengths or two or more frequencies of the electromagnetic waves,

ii. a change in the intensity of the at least two or more wavelengths of the electromagnetic waves or two or more frequencies of the electromagnetic waves,

iii. a relative attenuation of the two or more wavelengths of the electromagnetic waves or two or more frequencies of the electromagnetic waves, iv. an attenuation ratio of the two or more wavelengths of the electromagnetic waves or two or more frequencies of the electromagnetic waves, v. a change in an attenuation ratio of the two or more wavelengths of the

electromagnetic waves or two or more frequencies of the electromagnetic waves, and

vi. a change in attenuation of the two or more wavelengths of light or two or more frequencies of light.

In one configuration the waveguide is an elongate member defining a lumen within it to transmit or propagate the electromagnetic waves of two or more wavelengths or two or more frequencies along the length of the waveguide.

In one configuration the electromagnetic waves may be any suitable waves along the electromagnetic spectrum.

In one configuration the electromagnetic waves of two or more wavelengths or two or more frequencies may be any one of:

a. visible light

b. infrared

c. microwave

d. ultraviolet

The term 'comprising' as used in this specification and claims means 'consisting at least in part of. When interpreting statements in this specification and claims which include the term 'comprising', other features besides the features prefaced by this term in each statement can also be present. Related terms such as 'comprise' and 'comprised' are to be interpreted in a similar manner.

It is intended that reference to a range of numbers disclosed herein (for example, 1 to 10) also incorporates reference to all rational numbers within that range (for example, 1, 1.1, 2, 3, 3.9, 4, 5, 6, 6.5, 7, 8, 9 and 10) and also any range of rational numbers within that range (for example, 2 to 8, 1.5 to 5.5 and 3.1 to 4.7) and, therefore, all sub-ranges of all ranges expressly disclosed herein are hereby expressly disclosed. These are only examples of what is specifically intended and all possible combinations of numerical values between the lowest value and the highest value enumerated are to be considered to be expressly stated in this application in a similar manner.

As used herein the term '(s)' following a noun means the plural and/or singular form of that noun. As used herein the term 'and/or' means 'and' or 'or', or where the context allows both.

The invention consists in the foregoing and also envisages constructions of which the following gives examples only. BRIEF DESCRIPTION OF DRAWINGS

Figure 1 shows a graph of intensity of light as a function of distance travelled by light through an absorbing and/or scattering medium.

Figure 2A shows an embodiment of a sensing device for detecting deformations.

Figure 2B shows a rest configuration and a deformed (i.e. stretched)

configuration of the sensing device illustrated in figure 2a.

Figure 3 shows a diagram of an exemplary construction of the waveguide of the sensing device shown in figure 2a.

Figure 4A shows an exemplary configuration of a sensing device including a plurality of optical sources (i.e. light sources) and a single optical sensor. Figure 4B shows an exemplary configuration of a sensing device including a single optical source (i.e. a light source) and a plurality of optical sensors.

Figure 5 shows a graph of the intensity of red light and green light as a function of stretch.

Figure 6A shows an embodiment of a sensing device including a coloured region. Figure 6B shows a further embodiment of a sensing device including a plurality of coloured regions.

Figure 7A shows an embodiment of a sensing apparatus for use with a coloured video sensor.

Figure 7B shows an embodiment of a sensing apparatus for use with a monochrome video sensor.

Figure 8 shows a bent configuration of a sensing device where the optical source and optical sensor are co-located. Figure 9 shows an embodiment of a sensing device including a reflective member.

Figure 10 shows an embodiment of a sensing device for detecting or indicating a multi axis deformation . Figure 11A shows a sensing apparatus for detecting force or pressure or stress in an un-deformed state

Figure 11B shows a sensing apparatus of figure 11A in a deformed state.

Figure 12 shows a sensing apparatus in form of a two dimensional array.

Figure 13 shows a sensing apparatus for detecting an applied force or pressure using total internal reflection .

Figure 14 shows a sensing apparatus for sensing bending that includes a plurality of sensing devices disposed on or within a body.

Figure 15 shows a sensing system including a controller in electronic

communication with a sensing device. Figure 16 shows an example configuration of a light source arrangement.

Figure 17 shows an exa mple configuration of a clamp used to clamp the waveguide or light pipe to the light source.

DETAILED DESCRIPTION

Various aspects of a sensing device, sensing system and sensing device for sensing deformations, in particular physical deformations, will now be described with reference to the accompanying drawings.

Light is attenuated and scattered as it passes through any material, in particular an absorbing or scattering or reflecting material. The rate of light intensity reduction passing through such a material or medium is approximated by the Beer-Lambert law. The intensity of light passing through a homogenous absorbing and/or scattering medium can be approximated by /^' = /Ό exp(-l / A), where A is the mean free path length (i .e. the length at which the intensity is attenuated by 1/e), / is the distance from the source at which the intensity is measured, /Ό is the light intensity at the source and /^' is the intensity at the distance /. Most media will absorb and/or scatter light as it passes through it. Figure 1 shows a graph of the intensity of light as a function of distance travelled through an absorbing and/or scattering medium with a mean free path length of one. The graph 100 of figure 1 shows the intensity of light (intensity being on the y axis) reducing nonlinearly i.e. exponentially as the distance from the optical source increases.

For very transparent materials such as glass or plastic used in optical fibres, the mean free path length is very large. On the other hand, opaque materials have a comparatively small mean free path length. Translucent materials, such as turbid fluids and many elastomers, have an intermediate mean free path length. These materials appear to have a mean free path length relatively independent of their state of deformation. For example, if light is passed through such a material, the relative change in light intensity will be approximated by the Beer-Lambert law / = λ log (/Ό / /^'). When the material is stretched the distance at which the intensity measured is increased and hence the intensity will decrease, allowing deformation (i.e. strain) to be calculated. Different wavelengths (or frequencies) of electromagnetic waves have different mean free path lengths. For example, light of different colours (i.e. of different wavelengths or frequencies) generally have different mean free path lengths in a material. The present invention uses the wavelength dependent (or frequency dependent) absorbing and/or scattering properties of a material in order to detect or indicate deformation. Further details are provided below with reference to the figures.

The present invention can be said to be a sensing device, apparatus and system for detecting or indicating deformation. "Deformation" as used herein is means any strain due to an applied stress (i.e. applied force). The deformation may be a single axis or a multi-axis deformation. The sensing device, sensing apparatus and sensing system in accordance with the present invention can be used to detect or indicate one or more deformation modes i.e. various types of deformation.

In general, the present invention is a sensing device comprising an emitter emitting electromagnetic waves of at least two wavelengths or at least two frequencies, a sensor (i.e. detector), a waveguide to guide the emitted waves, the emitter positioned at or adjacent to an inlet of the waveguide, the sensor (i.e. detector) positioned at or adjacent to an outlet, the waveguide configured to transmit electromagnetic waves emitted by the emitter to the sensor, the sensing device configured to indicate or generate a signal indicative of a deformation of a portion of the sensing device based on a relationship of the at least two wavelengths or the at least two frequencies. In one embodiment the present invention is a sensing device comprising : an optical source emitting light of at least two wavelengths or at least two frequencies, an optical sensor, a waveguide, the optical source positioned at or adjacent to an inlet of the waveguide, the optical sensor positioned at or adjacent to an outlet, the waveguide configured to transmit light emitted by the optical source to the optical sensor, and wherein the sensing device configured to indicate or generate a signal indicative of a deformation of a portion of the sensing device based on a relationship of the at least two wavelengths or the at least two frequencies. The optical sensor may be any suitable optical sensor that can detect light intensity. The optical source is preferably a light source that emits visible light. However alternatively depending on the specific use and configuration of sensing device, the optical source may emit waves in the

electromagnetic spectrum e.g . infrared waves or ultraviolet waves or any other waves. The deformation is detected or indicated based on a relationship of the at least two wavelengths or at least two frequencies of electromagnetic waves generated. The relationship used to detect or indicate deformation is preferably a relative relationship of the at least two wavelengths or at least two frequencies of light detected at the optical sensor. The relationship used to detect or indicate deformation is based on the ratio of the two (or more) wavelengths or frequencies of light. The ratio of intensities can be determined based on a signal from the optical sensor. Alternatively, the relationship used to detect or indicate deformation may be a change in the ratio of intensities of the at least two wavelengths or frequencies of light. The change in the ratio may be compared to a baseline or threshold ratio. Deformation in this case relates the length of a sensitive region of the sensing device.

This approach is advantageous because it factors out unknown losses of light thereby providing more accurate determination of deformation. The approach of determining deformation based on a relationship of at least two wavelengths or frequencies of light e.g. a ratio of intensities of the at least two wavelengths or frequencies of light can also provide a signal having a better signal to noise ratio since errors in the source intensity will have a smaller effect on the output. Figure 2A shows an embodiment of the sensing device 200. The sensing device

200 comprises a waveguide 202, an optical source 204 (i.e. an emitter), and an optical sensor (detector) 206. The waveguide 202 is preferably an optical waveguide. The waveguide 202 is configured to transport or guide light e.g. visible light from an inlet to an outlet. The waveguide 202 may be configured to transport or guide any other suitable electromagnetic waves. The term waveguide as used herein means a structure or device that guides waves e.g. electromagnetic waves or light waves from one end of the waveguide to the other end with minimal loss from the structure. The optical source 204 (i.e. emitter) preferably is a light source that emits light of two or more wavelengths or two or more frequencies. The optical sensor 206 is a suitable sensor to detect light.

The waveguide 202 is preferably an elongate member defining a passage for electromagnetic waves emitted from the emitter 204 to be transported to the sensor 206. As seen in Figure 2A the optical source 204 is positioned at or adjacent an inlet 220 (i.e. a first end) of the waveguide 202 and the optical sensor 206 is positioned at or adjacent an outlet 222 (i.e. a second end) of the waveguide 202. The waveguide 202 configured to transmit light of two or more wavelengths or frequencies from the optical 204 to the optical sensor 206. The optical sensor 206 (i.e. detector) can receive and detect light of the at least two wavelengths (or at least two frequencies). The waveguide 202 is of a shape and configuration to reduce losses of electromagnetic waves as they propagate through the waveguide 202.

The optical source 204 is configured to emit least two wavelengths or two frequencies of light. In one example the optical source 204 emits light in the invisible light spectrum and emits a plurality of different wavelengths or frequencies of light, that correspond to different colours. In this example the optical source 204 is configured to generate a light of two colours, for example a red light and a green light. The optical source 204 however may emit light having any number of wavelengths or frequencies (i.e. the optical source 204 may emit a plurality of colours) . The optical sensor 206 is configured to detect the intensity of the emitted light of at least two different

wavelengths or at least two different frequencies. The optical sensor 206 is preferably configured to generate a signal indicative of an intensity of the received light. In one example the optical sensor 206 may be configured to generate a signal indicative of the intensity of each colour detected by the optical sensor 206. The optical sensor 206 can be any suitable sensor that measures the intensity of light impinging on an active or sensitive area. The optical sensor 206 may generate a signal indicative of an intensity of light. The optical sensor 206 may also be any suitable sensor that can detect the intensity of any other electromagnetic wave.

The sensing device 200 may be configured to generate a signal indicative of the deformation. Alternatively, the sensing device 200 may visually indicate deformation based on the change in the intensity of the light of the two or more wavelengths or frequencies. Figure 2B shows the sensing device 200 in a rest position and a deformed position. The upper sensing device 200 (in figure 2A) is a sensing device at rest position. The lower sensing device 200 (in figure 2B) is a sensing device in a deformed position. The deformation is a linear deformation i.e. an axial deformation. The sensing device 200 is preferably configured to detect or indicate linear deformation e.g. stretching of the sensing device, in particular stretching of the waveguide 202. The deformation as shown in figure 2B can be detected based on at least the ratio of measured intensities of the at least two (or more) wavelengths or frequencies of light transmitted through the waveguide 202. The optical sensor 206 may be any suitable optical sensor such as a

photodetector or a colour sensor. The optical source 204 can be any light source e.g. a light emitting diode (LED) or a diode resistor or any other suitable light source. In alternative configurations the source 204 may be a source of electromagnetic waves.

The sensing device 200 is configured generate a signal indicative of a

deformation of a portion of the sensing device 200 based on a relationship of the at least two wavelengths or at least two frequencies of light. In one example a relationship is a ratio of intensities of the at least two wavelengths or two frequencies of light. The deformation of a portion of the sensing device e.g. a sensitive region of a waveguide 202 can be calculated or determined based on the ratio of measured intensities of the two (or more) wavelengths or frequencies of light or two (or more) frequencies of light detected by the optical sensor 206.

The sensing device 200 indicates deformation of a portion of the sensing device 200, in particular, a portion of the waveguide 202 based on. An amount of deformation is related to the ratio of intensities of at least two wavelengths or frequencies of light detected by the optical sensor 106. The amount of deformation may be related to an absolute value of a ratio of intensities of the at least two wavelengths or frequencies of light or a change in the ratio of intensities of the at least two wavelengths or frequencies of light.

Alternatively, the relationship may be a change in the ratio of intensities of the two (or more) wavelengths or frequencies of light, or the relationship may be a ratio of measured intensities of the two (or more) wavelengths or frequencies of light compared to a baseline or threshold ratio of intensities. In a further alternative the relationship between the at least two (i.e. two or more) wavelengths or frequencies of light may be the relative attenuation of the two or more wavelengths or frequencies of light. The relationship may be a change in the attenuation of each wavelength or frequency compared to a threshold or baseline. The relationship may be an attenuation ratio or a change in an attenuation ratio of the two or more wavelengths or frequencies of light. Attenuation ratio may be a ratio of intensities or a ratio of the difference in intensities.

In one example the optical response of the sensing device 200 may be characterised to be in a rest state. The rest state characterisation allows determination of the attenuation of different wavelengths or frequencies of light when the waveguide is at rest. The intensity of each wavelength or frequency of light and/or the ratio of intensity of two or more wavelengths or frequencies of light, at rest, can be calculated as part of the characterisation process. The characterisation process may be performed after manufacture of the sensing device or prior to use of the sensing device 200 or at any other suitable time. The deformation e.g. stretch can be determined based on the ratio of intensities, as compared to the characterised optical response of the sensing device.

In another example the optical response i.e. light intensities and/or ratio of light intensities at various stretched configurations and rest configurations may be determined as part of the characterisation process of the sensor 206. The deformation e.g. stretch of a portion of the sensing device 200 can be determined by checking the ratio of intensities of the two or more wavelengths or frequencies with the characterised response. The characterised response in this case may be stored in a database or a lookup table or as a graph etc. In a further example an approach to calibration of the sensing device can be to make many measurements and use a smooth interpolant to determine intermediate values. Another exemplary calibration approach can be to use an exponential interpolant and identify the parameters of the exponential that best match measured values. A further example would rely on assumed optical properties of the waveguide to determine length (i.e. stretch or deformation) from intensity ratios analytically.

Figure 3 shows an embodiment of the construction of the waveguide 202. The waveguide 202 is preferably made from a relatively transparent material e.g. a silicone or a polyurethane elastomer. Alternatively, the waveguide 102 may be made from a substantially translucent material e.g. an elastomer or a turbid material. Alternatively, the waveguide 202 may be made from a liquid contained in a solid e.g. an elastomeric tube.

The specific material choice for the waveguide can be selected depending on the particular use of the sensing device. For example, it is feasible to construct the waveguide 202 using a relatively absorbent medium (i.e. that has a very small mean free path length). Such a sensing device will have a large change in intensity for small changes in length. Alternatively, a relatively transparent material may be used for constructing the waveguide 202 (i.e. a material that has a large mean free path length). Such a sensing device will have a small change in intensity for large changes of length. For example, if large displacements are required, a long section of relatively transparent material can be used as the sensitive region i.e. for the waveguide to measure small displacements or small deformations, a relatively opaque material may be used as sensitive region i.e. to form the waveguide 202.

Referring again to Figure 3, the illustrated waveguide 202 may be formed from a substantially clear silicon or polyurethane elastomer can be used to construct the waveguide 202. In one example the waveguide 202 is formed from Smooth-On Sorta- clear 37 silicone elastomer. Alternatively, the waveguide 202 may be formed from a low absorbance silicone that can stretch up to 5 times its original length. The silicone may be medical grade silicone. The waveguide 202 comprises a core 210 and an outer jacket 212 i .e. cladding that surrounds the core 210. The core 210 is substantially hollow and defines a passage for transmitting light (or electromagnetic waves) through the core 210. The core 210 preferably has a higher reflective index than the jacket 212 i.e. cladding. As shown in Figure 3 the core 210 has a first reflective index nO and the jacket 212 i.e. cladding has a second reflective index nl . The reflective index nO of the core 210 is preferably higher than the reflective index n l of the jacket 212 i.e. cladding. The core 210 having a higher reflective index than the jacket 212 allows for total reflection allows transmission of light (or other electromagnetic waves) through the core 210 with minimal losses. Figure 3 shows the light path 214 as it travels through the core 210, within minimal loss through the core due to total internal reflection.

The jacket 212 (i.e. cladding) protects the core 210 and allows the sensing device to remain relatively immune to objects touching its surface. In one example the core 210 may be formed from a resiliently deformable silicone having refractive indices ranging from 1.38 to 1.58. Other materials having other refractive indices may be used in alternative constructions depending on the particular use or implementation of the sensing device 200.

The waveguide 202 is preferably formed from a material that is resiliently deformable material e.g. a silicone elastomer, such that the waveguide 202 can be resiliently stretched axially. The waveguide 202 may include a sensitive absorbing and/or scattering section. The sensing device 200 can respond to stretch i.e. deformation to stretching in the sensitive region.

In an alternative construction, the waveguide 202 may include a composite material core 210. The core 210 may be formed from two or more different materials. In this alternative example a sensitive absorbing and/or scattering section may be formed from a resilient material e.g. a silicone or polyurethane elastomer and the rest of the core 210 may be formed from a substantially rigid, transparent material such as for example glass. The jacket 212 (i.e. cladding) is preferably formed from a stretchable or resiliently deformable material that has a smaller refractive index than the material of the core 210. The light guide including the core and the jacket may be formed by continuously extruding the core 210 and the cladding. The jacket 212 i.e. cladding provides protection for the waveguide from external forces.

As shown in figure 3 the waveguide 202 comprises a substantially circular cross section. The core 210 is a substantially tubular or cylindrical member. In alternative configurations the waveguide 202 may be a substantially planar to flat shape. In this alternative configuration the waveguide 202 may comprise a substantially rectangular or square cross section. For example, the waveguide 202 may be constructed of thin films of elastomer. Preferably the thickness of the films of elastomer are greater than 10 micrometres. A rectangular waveguide 202 could be manufactured by laminating a relatively high refractive index elastomeric sheet between two relatively low refractive index sheets. The high refractive index sheet forms the core 210 while the lower refractive index material forms the jacket 212 i.e. cladding.

The material of the waveguide 202 is formed of a material that has a wavelength dependent mean free path length i.e. different wavelengths of light (or other

electromagnetic waves) attenuate different amounts through the waveguide 202.

Deformation e.g. stretch of the waveguide (or a sensitive region of the waveguide) is calculated from the ratio of the measured intensities of at least two or more wavelengths of light supplied. This approach factors out any unknown losses of light as well as any potential effects of ambient light, on the assumption that the losses outside the sensitive region are not significantly wavelength dependent.

In one example the entire waveguide 202 may be the sensitive region.

Alternatively, only a portion of the waveguide 202 may function as the sensitive region.

Figure 4A shows an exemplary configuration of the sensing device 400. As seen Figure 4A shows an optical source 404 comprising three separate optical sources 404a, 404b and 404c that are positioned at or adjacent to an inlet of a waveguide 402. Each optical source 404a-404c is configured to generate a narrow spectrum of wavelengths of light i.e. a single colour of light. In one example, the three optical sources 404a-404c may generate red, green and blue light respectively. An optical sensor 406 is located at or adjacent a second end (i.e. outlet) of the waveguide 402. The optical sensor 406 is configured to detect an intensity each wavelength of light e.g. the intensity of different colours such as red, green and blue light emitted from the three optical sources 404a- 404c. The optical sources 404A-404C may be LEDs (light emitting diodes) or diode lasers. One example of the optical source is the T-13/4 (5mm) suitable for illuminating 5mm diameter waveguide s (e.g . silicon light pipes).

The optical sensor 406 can be any suitable optical sensor that can detect three different wavelengths or frequencies of light such as red, green blue wavelengths or frequencies of light. One example is the Hamamatsu S9702 RGB colour sensor that is able to distinguish red, green and blue wavelengths or frequencies. Diode lasers are advantageous because they provide narrower wavelength bandwidths and improved wavelength stability as compared to LEDs. Further diode lasers can be fairly inexpensive and are available in a wide range of wavelengths ranging from deep blue (approximately 400 nanometres) to infrared (approximately 1600 nanometres).

Figure 4B shows a further exemplary configuration of the sensing device 410. The sensing device may comprise a waveguide 412 and a single optical source 414 e.g. light emitter. The optical source 414 is preferably configured to generate at least two wavelengths or frequencies of light. The optical source 414 can generate more than two wavelengths or frequencies of light or alternatively may be configured to emit broadband light e.g. white light. In the illustrated example the optical source 414 generates red green and blue wavelengths or frequencies of light. The sensing device 410 further includes three separate optical sensors 416a, 416b and 416c. Each optical sensor 416a-416c is configured to an intensity measure a narrow band of wavelengths of light (i.e. detect a single colour of light) . For example, optical sensor 416a is configured to measure intensity of red light, optical sensor 416b is configured to measure intensity of green light and optical sensor 416c is configured to measure intensity of blue light. Either

construction 400 or 410 may be used for creating the sensing device. Either construction 400 or 410 can be adopted to create sensing device 200. The particular construction used may depend on the particular implementation or application the sensing device is being used for. Red light generally has a mean free path that is longer than green light.

Therefore, the intensity of red light will diminish slower than the intensity of green light. The intensity and ratio of green to red light will thus diminish along the length of the transducer. Figure 5 shows an example graph of the intensities of red and green light measured by the optical sensor as a function of stretch of the sensing device. The vertical axis represents intensity and the horizontal axis represents stretch. One along the horizontal axis represents a rest state of the sensing device, in particular the waveguide. The other numbers along the horizontal axis represent stretch of the waveguide. The graph 502 shows the intensity of red light diminishing as the waveguide stretches. Line 506 represents the green light diminishing in intensity as the waveguide stretches. As can be seen green light diminishes more than the red light due to stretch. Again, this is due to the mean free path of the red light being longer than the green light. Line 504 represents the ratio of green light intensity to red light intensity.

The ratio of intensity of the red light to green light is independent of light lost within the waveguide due to cracks etc. The use of multiple wavelengths or frequencies of light and determining stretch based on either the ratio of measured intensities or the change in the ratio of measured intensities relative to a reference is advantageous as it provides sensing device that is independent of the source intensity. The stretch i.e.

deformation of the sensing device holds a nonlinear relationship to the ratio of the measured intensities. As can be seen in figure 5, the ratio of measured intensities decreases and changes based on the amount of stretch i.e. deformation of the

waveguide.

Figure 6A and 6B show further configurations of the sensing device. Referring to Figure 6A there is shown an exemplary configuration of the sensing device 600. The sensing device 600 comprises a waveguide 602. An optical source 604 is positioned at or adjacent the inlet end of the waveguide 602 and an optical sensor 606 positioned at or adjacent an outlet end of the waveguide 602. The optical source 604 preferably emits light of at least two different wavelengths or frequencies i.e. two different colours of light. The optical sensor 606 is configured to detect the intensity of each wavelength or frequency of light. The waveguide 602 includes a coloured or dyed region 608 which has higher attenuation than the rest of the waveguide. The waveguide 602 may be formed from a substantially opaque material and the sensitive regions may be coloured or dyed regions. Alternatively, the waveguide 602 may be substantially opaque and the sensitive regions may be formed from substantially transparent material. As shown in Figure 6A the coloured region occupies a portion of the overall waveguide 602. The coloured region 608 forms a sensitive region of the waveguide 602. The stretch or deformation of the sensitive region 608 is based on a relationship of the at least two different wavelengths or frequencies of light. The relationship. In one example the relationship is the ratio of the intensities of the two different wavelengths or frequencies of light. The light intensity will change as the light from the optical source 604 passes through the coloured region 608, and the intensity of each wavelength or frequency changes due to stretch in the coloured region 608.

The dyed region 608 may be dyed in a suitable colour using a fluorescent dye. The coloured region 608 may be located at any point within the waveguide 602 e.g. at the beginning of the waveguide 602 or in the middle of the waveguide. Figure 6A shows the coloured region is located in the middle of the waveguide 602. The coloured region 608 produces a fluorescent response proportional to the intensity of light being received within the waveguide. The stretch i.e. deformation of the coloured region 608 can be calculated from the ratio of intensities of the two or more wavelengths or frequencies of light.

For example, if the coloured region 608 is a red coloured region, then the red wavelength or frequency of light will be transmitted while the other wavelengths or frequencies of light are absorbed. Different colour dyes have different absorption spectra depending on the colour of the dye. The ratio of intensities received at the outlet end i .e. at the optical sensor 606 will vary by a particular amount as the light passes through the coloured region. The change in the ratio of intensities or the calculated ratio of intensities would be dependent on the stretch of the dyed or coloured region 608.

Figure 6B shows a further configuration of the sensing device 610. The sensing device 610 comprises a waveguide 612 with an optical source 614 positioned at or adjacent an inlet of the waveguide 612 and an optical sensor 616 positioned at or adjacent an outlet of the waveguide 612. As shown in Figure 6B the waveguide 612 may comprise a plurality of coloured regions 618 and 620. The plurality of coloured regions may represent or correspond to multiple sensing or sensitive regions of the sensing device. As shown in figure 6B the first coloured region 618 is located closer to the inlet and the second coloured region 620 is located closer to the outlet of the waveguide 612. The stretch of the sensing regions again can be determined based on the change and the ratio of intensities of the different wavelengths or frequencies of light received at the sensor 606. In one example the sensor is calibrated with the base line intensity ratio. For example, at rest the sensing device is calibrated and a known change in intensity can be determined and stored. A deviation from this reference ratio of intensities represents a particular deformation that can be calculated.

In a further alternative configuration, the entire waveguide 602 may be coloured a particular colour. Different coloured dyes have different absorption spectra. The type of coloured dye and location of the coloured dye can be used to create a customized sensor for a specific use or application. The specific selection of coloured regions, the number coloured regions and the particular colour used selected based on the particular use required by the sensor. The optical properties of the constituents can be tailored e.g. by using coloured or fluorescent dyes to create materials that suit the task. The spectral absorbance of the dye can also be tailored to match either the particular use of the sensor or the optical sources being used. The spectral absorbance of the dye and the selection of the particular dye can be tailored such that particular wavelengths or frequencies are more absorbed than other wavelengths or frequencies. For example, one can choose from a wide range of dyes with different spectral absorbent characteristics depending on a particular use.

The use of dye to colour one or more regions of the waveguide can be used to control the sensitive region. The use of specific dyed or coloured regions of the waveguide can allow customised sensing devices to be created . The type of dye used can be customised for the type or amount of deformation e.g. stretch that needs to be detected.

Figures 7A and 7B shows two configurations of a sensing apparatus 700, 710. The sensing apparatus comprises a plurality of sensing devices as described earlier.

Figure 7A and 7B show a sensing apparatus that comprises an array of sensing devices arranged linearly enabling multiple length sensors i .e. sensing devices to be operated from a single inexpensive unit. Configuration 7A enables a single broadband light source to illuminate many independent waveguides, with the relative absorption of different wavelengths or frequencies through each being measured by a colour video detector array. Configuration 7B enables multiple broadband light sources to illuminate many independent waveguides, with the relative absorption of different wavelengths or frequencies through each being measured by a monochrome video detector array.

The configuration shown in Figure 7A comprises a single optical source 704 (e.g . a white LED or a white diode laser) providing illumination to a bundle of waveguides 702. The plurality of waveguides in the bundle 702 are preferably arranged axially and substantially parallel to each other as shown in Figure 7A. The bundle of waveguides 702 may be arranged in a cylindrical orientation or may be arranged tightly together. An optical sensor is located at the end of each of the waveguides. The bundle 702, as shown in figures 7A comprises eight waveguides. The sensing apparatus 700 comprises a plurality of optical sensors. In the illustrated example the configuration 700 comprises eight optical sensors 706a, 706b, 706c, 706d, 706e, 706f, 706g, 706h (706a-706h). Each optical sensor preferably includes three optical sensors located at the end of each waveguide bundle 702. Each optical sensor measures the intensity of one wavelength or frequency of light. Each optical sensor 706a-706h each comprise a single three photo resistor or photo diode of three colours, e.g. red, green and blue photo resistor or photo diode. The configuration shown in figure 7A uses continuous measurement of different wavelengths (e.g. red, green and blue) by the optical sensors and the optical source 704 is a broadband light source (e.g. white LED). The sensors 706a-706h are wavelength sensitive photodetectors. The configuration 700 may incorporate a colour video sensor.

The configuration 710 shown in Figure 7B might consists of a bundle of fibres i.e. plurality of waveguides 712 arranged parallel to each other. Alternatively, the

waveguides 712 may be bound tightly together. The sensing apparatus 710 comprises three optical sources 714a, 714b and 714c (714a-714c) positioned at one end of the waveguide 712. Each optical source is configured to transmit a single wavelength or frequency of light e.g. red, green, blue light through each waveguide 712. The

configuration 710 comprises a plurality of optical sensors e.g . eight optical sensors 716a- 716h. Each optical sensor is positioned at an outlet of each waveguide. The optical sensors 706a - 706h may each be multiplexed based on time or frequency to measure red, green and blue light intensities transmitted along each waveguide. The optical sensors 706a- 706h can measure different wavelengths or frequencies. The optical sensors 706a - 706h may be wavelength insensitive photodetectors. The configuration 710 may incorporate a monochrome video sensor.

The configuration shown in Figure 7A may be used as a colour video sensor. The configuration of Figure 7B may be used as a monochrome video sensor. The

configurations in figures 7A and 7B can take advantage of video sensor technologies to achieve high throughput thereby enabling many length sensors to be operated from a single unit.

There is flexibility in the geometry and composition of the light guides. The use of a flexible light guide allows for additional uses as compared to traditional strain sensors. Preferably the light guide comprises a circular cross section but alternatively the light guide may comprise any other suitable shape e.g. a rectangular cross section, a square cross section or an oval cross section or a trapezoid cross section, or a planar cross section.

The waveguide e.g. 202 is preferably made of a stretchable or resiliently deformable material. The waveguide 202 is preferably formed from a substantially flexible or a malleable material such that the waveguide can be folded or bent. The passageway defined in the body of the waveguide 202 can be bent to direct light from the source 204 to the sensor 206. Figure 8 shows an example of the sensing device 200, where the waveguide 202 is arranged in a folded or bent arrangement. The optical source 204 and the optical sensor 206 can be co-located together or may be located near each other. The waveguide 202 can be bent in order to allow the optical source 204 and the optical sensor 206 to be co-located. This provides the advantage that both the optical source 204 and optical sensor 206 can be mounted on a single printed circuit board, thereby allowing for a simplified design.

Figure 9 shows an alternative configuration the sensing device 200 comprising a waveguide 202. The waveguide 202 comprises an inlet opening 220 and an inlet passageway 230. The inlet opening 220 is defined in the inlet passageway 230 such that light from the source 204 is directed into the inlet passageway 230. The waveguide 202 also comprises an outlet opening 222 defined in an outlet passageway 232. The inlet passageway 230 and the outlet passageway 232 are arranged parallel to each other, or they may share the same waveguide. The waveguide 202 further comprises a reflective member 240 positioned within the light guide such that light received in the inlet opening 220, from the light source 204 is reflected off the reflective member 240 and is directed to the outlet opening 222 for detection by the optical sensor 206. The optical source 204 (i.e. emitter) and the optical sensor 206 are preferably co-located. The illustrated configuration in figure 9 provides the advantage that both the optical source 204 and optical sensor 206 can be mounted on a single printed circuit board, thereby allowing for a simplified design.

The configurations shown in figure 8 and 9 can be used for various applications. One example is the waveguide 202 may be implanted for stretch sensing within a human or animal body. The light source 204 and the sensor 206 can be positioned outside the body and the waveguide 202 can be bent like in figure 8 and positioned inside a human or animal body. The waveguide 202 is preferably made of a biocompatible material or coated in a biocompatible material to allow these types of sensors to be implanted. The sensing devices shown in figures 8 and 9 can also be incorporated into clothing or garments to detect deformation. A plurality of sensing devices can be incorporated into clothing to detect multiple modes of deformation.

Figure 10 show a further configuration of a sensing device 800. The sensing device 200 described earlier comprises a single light source and a single optical sensor. The sensing device 800 comprises a wave transmission member i.e. a waveguide 802. The sensing device 800 may comprise a plurality of light sources and a plurality of optical sources. In the illustrated configuration in figure 10, the sensing device 800 comprises three light sources 804a, 804b and 804c and three optical sensors 806a, 806b and 806c. The sensing device 800 may comprise an equal number of light sources and optical sensors. The configuration of multiple light sources 804a - 804c and optical sensors 806a - 806c can be configured to measure many components of deformation i.e. multiple modes of deformation such as for example displacement, shear, rotation etc.

The waveguide 802 is substantially cylindrical and includes a pair of flat faces 850 and 852. The flat faces are opposing faces and define ends of the waveguide 802. The light sources 804a - 804c are disposed on the first face 850 are spaced apart from each other. As shown in figure 10, the light sources 804a-804c are arranged in a substantially triangular layout. The optical sensors 806a - 806c are arranged on the second face 852. The optical sensors 806a - 806c preferably arranged out of phase with the light sources 804a-804c. The optical sensors 806a-806c are preferably arranged 60 degrees out of phase with the light sources 804a-804c. With the illustrated arrangement of figure 10, six distances between each light source and its two nearest neighbouring sensors can be determined. This allows for six translation and rotation degrees of freedom between two rigid bodies to be determined. The relative intensity of light emitted from the three light sources 804a-804c, measured by the three optical sensors 806a-806c enables the distance between each of the nine pairs of sources and sensors to be determined. Six axes of relative translation and rotation between the first face 850 and second face 852 can be calculated using least squares fitting. The least squares fitting can be used on the ratio of intensities of the different wavelengths or frequencies of light that are detected by the sensors. The waveguide 802 may be made from a substantially transparent material and may include a cladding layer (i.e. a jacket) disposed around the outside thereof. The waveguide 802 may use similar materials as the waveguide 202 described earlier. The waveguide 802 may also include specific coloured regions to create a desired frequency dependent sensing zone. Figures 11A and 11B show a sensing apparatus used to detect pressure or force applied to it. The sensing apparatus comprises positioning a member having first optical and/or first mechanical properties on one or between two or more members having a second optical and/or second mechanical properties, wherein the first optical and/or mechanical properties are different to the second optical and/or mechanical properties. Such a sensing arrangement can be used to detect or measure pressure or force.

Figure 11A shows an embodiment of a sensing apparatus 900. The sensing apparatus 900 can function or operate as a pressure transducer. The sensing apparatus 900 comprises a pair of support members 902a, 902b and a compliant member 902c. The sensing apparatus further comprises a light source 904 and an optical sensor 906. The support members 902a, 902b are substantially rigid or stiff and transparent members. The support members 902a, 902b carry the compliant member 902c. The support members 902a, 902b are transverse members that are arranged substantially parallel to each other. The support members 902a, 902b are preferably formed from a relatively stiff and transparent material e.g. glass or a rigid, transparent elastomer. The compliant member 902c is resiliently deformable. The compliant member 902c is preferably formed from a resiliently deformable, light absorbing material e.g. an elastomer or a silicone. The support members 902a, 902b comprises patterned regions 910, 912. Preferably each support member 902a, 902b comprises at least one patterned region. The patterned regions are located adjacent the compliant member 902c. The patterned regions 910, 912 are configured to direct some light through support member into the compliant member 902c.

The optical sensor 906 is configured to generate a signal indicative of an intensity of light being measured by the optical sensor 906. The optical sensor 906 may be a photodetector or a photo resistor or any other suitable optical sensor. The optical sensor 906 may be a signal indicative of a pressure or force applied to the sensing apparatus 900. The amount of pressure or force may be related to a difference in intensity of the light or preferably related to a ratio of intensities of two or more wavelengths or frequencies of light detected by the optical sensor 906. The light source 904 preferably generates light of two or more wavelengths. Figure 11A shows a rest position of the sensing apparatus 900. As pressure or force is applied to a support member (e.g. 902a as shown in figure 11B), the compliant member 902c deforms and becomes thinner, allowing more light to pass though it and to the optical sensor 906. The pressure causes a reduction in the length of the compliant member 902c, which will cause a change in the intensity of light measured by the optical sensor 906. The change in length will change the ratio of intensities of the two or more wavelengths or frequencies of light that are measured by the optical sensor 906. The amount of deformation corresponds to the measured ratio or change in the ratio of intensities, which in turn also corresponds to the pressure. The sensing apparatus 900 as illustrated can be used as a pressure sensor. Figures 12 illustrates a sensing apparatus 1000. Figure 12 shows a view of the sensing apparatus 1000. The sensing apparatus 1000 may comprise a plurality of sensing devices disposed on or within a substrate. The sensing apparatus 1000 is configured to generate a signal indicative of deformation of at least a portion of the sensing apparatus 1000, based on a relative deformation of each of the plurality of sensing devices. The sensing apparatus 1000, shown in figure 12 is a two dimensional force/ pressure sensitive array. The array 1000 may comprise a plurality of sensing devices including a waveguide, a light source and an optical sensor. The sensing apparatus 1000 comprises a plurality sensing devices arranged in a two dimensional array. The array may be an m x n two dimensional array. As shown in the example of figure 12 the sensing apparatus 1000 comprises a plurality of horizontal waveguides

1002a-1002h and a plurality of vertical waveguides 1002i-1002o. The light sources 1004 are arranged aligned with horizontal waveguides. The optical sensors 1006 are arranged aligned with the vertical waveguides. The arrangement can be interchanged. Every element of the array can be resolved by time or frequency multiplexing the m light sources i.e. light sources 1004. Such an arrangement can be used to provide dynamic two dimensional pressure/force maps using relatively thin components. The array 1000 can be used to determine pressure/force applied to an area .

For example, the array 1000 or the sensing apparatus can be incorporated into clothing or garments to determine force/ pressure applied to particular areas of the clothing. Similarly, the array 1000 may be incorporated into any other planar device or element to detect pressure/force applied to the planar device.

Figure 13 shows a further configuration of a sensing apparatus 1010 that is used to determine pressure or force applied to the sensing apparatus or another element that incorporates the sensing apparatus 1010. The array 1010 utilises a plurality of compliant or resiliently deformable light absorbing elements. The array 1010 comprises a light reflecting top layer 1012, a base layer 1016 and an absorbing layer 1014 sandwiched between the top layer 1012 and a base layer 1016. The top layer 1012 is preferably made of a reflective material e.g. metallised polymer film. The top layer 1012 acts as an interfacing layer i.e. to interface with a user and may comprise a sheet of reflecting material. The base layer 1016 is preferably a substantially transparent layer that can be made from a substantially rigid, transparent material e.g. toughened glass. The base layer 1016 may comprise a sheet of toughened glass. The absorbing layer 1014 may comprise a plurality of resiliently deformable members 1018. The deformable members 1018 are preferably light absorbing members that can be formed from a suitable elastomer and may be translucent or substantially transparent. The deformable members 1016 may be formed of silicone or thermoplastic elastomer (TPE) or any other suitable light absorbing, resiliently deformable material.

The array 1010 or the sensing apparatus may be simultaneously illuminated with one or more light sources that may be positioned adjacent the base layer 1016. The light sources may be configured to generate light having two or more wavelengths or frequencies. Alternatively, the light sources may be configured to generate (i.e. emit) polarized light to reduce confounding effects of specular reflection. In a further alternative configuration, the light may be guided through a transparent backing layer that forms the base layer 1016. The base layer 1016 can act as a planar waveguide. The array or the sensing apparatus 1010 may also comprise one or more optical sensors arranged below or adjacent the base layer 1016, such that the light sources and the optical sensors are substantially co-planar. Alternatively, a video camera may be used instead of the optical sensors. The optical sensors are configured to generate a signal indicative of deformation of the absorbing layer 1014 Pressure applied to the top layer 1012 (i.e. interface layer 1012) causes the deformable members 1018 to deform or flex. Figure 13 shows an example of this deformation. This reduces the thickness of each of the deformable members 1018 as a function of the applied pressure. Light 1020 passing through each element will be attenuated, specifically the intensity will be attenuated as a function of the applied pressure. The attenuation is inversely related to the pressure. Similar to the

configuration shown in figures 11A and 11B, the greater the pressure, the greater the deformation of the deformable members 1018, resulting in less attenuation. The light from the light source is reflected by the reflective top layer 1012 toward the optical sensors. The optical sensors can detect the change in intensity or the absolute value of the intensity that is indicative of the pressure 1022 applied. The optical sensors may be configured to determine pressure based on the ratio of intensities of two or more wavelengths or frequencies of light. The pressure may be determined based on the change in colour or the change in the intensity of two or more colours of light detected by the optical sensors. Each element of the array can be resolved by time or frequency multiplexing the light sources. The array configuration 1010 shown in figure 13 can be used to provide a force or pressure map. The intensity of the light detected at the light sensors (i.e. optical sensors) will increase due to pressure applied to the top layer 1012 since the length of each member 1018 reduces in length. This causes reduced absorption of light passing through each member 1018. In some forms the sensing apparatuses 1000 and 1010 comprise a plurality of sensing devices arranged in a two dimensional array. Any sensing device structure disclosed herein (e.g. sensing device 200, 400, 600, 610) can be used as part of the apparatus 1000. Any combination of sensing devices disclosed herein may be used to construct the apparatus 1000 or sensing apparatus 1010. Figure 14 shows a further configuration of a sensing apparatus 1100. The sensing apparatus 1100 comprises a plurality of sensing devices 1110 disposed on or within a body i.e. a substrate. The sensing devices 1110 may be similar to sensing devices 200 or 400 or may include coloured regions like the sensing devices 600, 610. Any sensing device described herein can be used in the apparatus 1100. The sensing devices 1110 are all arranged substantially parallel to each other and are longitudinally arranged on or within the body 1102. As shown in figure 14, the sensing devices may be equally spaced about the body 1102. Preferably in order to detect or determine bending deformation, the sensing devices 1110 are equally spaced about the body. Alternatively, the sensing devices 1110 i.e. sensors may be arranged at angles relative to each other. In a further alternative configuration each sensing device 1110 may be arranged at an angle relative to either one or both of a horizontal or vertical axis of the body (i.e.

substrate).

The sensing apparatus 1100 comprises a substrate or body 1102. The body 1102 may be of any suitable shape. In the illustrated example, the body 1102 is substantially cylindrical in shape. The sensing devices 1110 are disposed on or within the substrate or body 1102. Each sensing device comprises a waveguide 1112, a light source 1114 and an optical sensor 1116. The light sources may be other electromagnetic wave emitters. The light sources 1114 preferably generate light of two or more wavelengths or frequencies e.g. two or more colours of light. The optical sensors 1116 are configured to determine a deformation of each waveguide 1112 (or sensing device) based on a ratio of the intensities of the two or more wavelengths or frequencies or a change in the ratio of two or more wavelengths or frequencies of light received by the optical sensors 1116.

The sensing apparatus 1100 can be used to detect bending type deformation. The bending is determined based on the relative deformation of each of the sensing devices. For example, some sensing devices will deform in compression while others will deform in tension as the body (i.e. substrate) 1102 bends. The sensing device that bends may see an increase in the intensities of the two or more wavelengths or frequencies while the sensing devices in tension may see a decrease due to the overall distance increasing. The sensing devices 1110 are arranged to be equally spaced and substantially parallel to each other in order to detect bending of the body 1102. As the body 1102 bends the sensing devices experience differential deformation i.e. bending. The deformation of the body 1102 may be determined by processing the signals from each sensor of each sensing device. The deformation of the body 1102 can be determined based on the differential deformation e.g. differential bending of each sensing device 1110. Other arrangements of sensing devices are contemplated to detect bending or other modes of deformation based on the differential deformation of each sensing device relative to the other sensing devices positioned on or within or along a body 1102.

This arrangement of multiple sensing devices in a suitable configuration can be used to determine different modes of deformation. The specific arrangement or configuration of the sensing devices can be selected based on the type of deformation mode that is required or desired to be detected. In another example the sensing devices 1110 may be disposed in a helical arrangement, extending along the body 1102. The sensing device 1110 may be disposed on or embedded within the body 1102, and arranged in a helical arrangement in order to determine torsion of the body. Torsion of the body 1102 is determined based on relative deformation of each sensing device.

Alternatively, each sensing device may be arranged at an angle relative to each other or may be arranged offset from a vertical and/or horizontal axis. In one example the sensing devices are arranged in a twisted configuration along or within the body 1102 to allow determination of a twisting. In some alternative configurations the local optical properties of the sensing device, in particular the waveguide may be tailored for a desired attenuation at rest and/or during use. The waveguide or a portion of the waveguide may be tailored by patterning the surface of the waveguide or structuring the refractive index. For example, a prismatic surface profile could be used to redirect some of the light propagating through the waveguide to a neighbouring element e.g. an absorbing structure. In another example the surface of the waveguide may have line spacing or a refractive index pattern to construct a Bragg grating. Very fine (submicron) grating can be created by

differentially curing elastomers using interference of coherent UV light. For example, a line spacing of 225nm in silicone of refractive index 1.4 would reflect light of a

wavelength of 630nm. If the waveguide is made of elastomer, the reflected wavelength would be directly proportional to the stretch of the grating, providing another method of length transduction. Since the reflected wavelength changes would be large for high strains, the need for expensive sensitive optics can be avoided. In further configurations the waveguide may be formed from materials with structures that create light absorbing and/or scattering at meso scales (e.g. elastomers with large inclusions or voids), with patterns of transparent and opaque films. The waveguide may include optically active constituents (polarisers) that can modulate light intensity with mechanical deformation.

Figure 15 shows an exemplary sensing system for sensing deformations. The sensing system 1200 shown in figure 15 is an exemplary configuration. The system 1200 includes a sensing device 1210, which could be like any sensing device described herein. The sensing device 1210 comprises at least a waveguide 1212, a light source 1214 (i.e. an optical source) and an optical sensor 1216. The waveguide directs light from the light source 1214 to the optical sensor 1216. The system further includes an electronic controller 1220 coupled light source 1214. The electronic controller 1220 may be any suitable light source controller that is in electronic communication with the light source 1214.

The system 1200 also includes a processor 1230 that is in electronic

communication with the optical sensor 1216. The processor 1230 is configured to receive signals from the optical sensor 1216 and process these signals in order to determine a deformation. The processor 1230 may also be configured to determine a pressure or force exerted on the sensing device. The deformation or pressure/force is preferably determined based on a ratio of the intensities of two or more wavelengths or frequencies detected by the optical sensor 1216. The processor 1230 is configured to receive the electrical signals indicative of a deformation from the optical sensor (or sensors) and process them using a suitable processing method to determine or detect a deformation or pressure/force applied. The processor 1230 may also include a memory unit 1232 in electronic communication with the processor 1230. The memory unit 1232 preferably stores computer readable instructions that are executed by the processor to determine deformation. The memory unit 1232 may include temporary memory to function as a buffer, wherein the temporary memory unit may be any suitable type of memory, preferably a non-volatile memory or a solid state memory unit.

The processor 1230 and memory unit 1232 may be in electronic communication with the controller 1220 or preferably are formed as part of or integral to the controller 1220. The processor 1230 preferably acts as the controller to control the light sources.

The effects of ambient light interfering with the sensing device can be avoided by modulating the light sources. Both frequency domain and time domain multiplexing schemes can be used to reject interference by ambient light. For example, if red, green and blue sources are switched on and off, in a specific pattern e.g. Gray Code, the eight distinct combinations of sources can be resolved at the optical sensor. This combination will enable relatively slow varying external sources to be distinguished from the optical signal i.e. the red, green and blue sources detected at the optical sensor (or sensors). Similarly, if the red, green and blue sources (i.e. light sources) are each modulated at relatively high, but distinct frequencies, bandpass filters can be used to separate the relative intensities. The controller 1220 as described or processor 1230 can be used to control the light sources of a sensing device or sensing apparatus to operate in this manner for noise reduction. Further the processor 1230 is configured to process the output of the optical sensors, e.g. by implementing the band pass filters or any other suitable filters.

The sensing device operates on the principle of varying ratio of intensities of two or more wavelengths or frequencies. This is because different wavelengths (i.e. different frequencies) are absorbed at different rates along the length of the waveguide. It is known shorter wavelength (i.e. higher frequency) waves e.g. light are absorbed quicker along the waveguide. There are many schemes for determining the relative absorbance of two wavelengths. One exemplary method is to modulate the intensity of each wavelength at different frequencies. Filters may then be used to determine the relative amplitudes of the modulated light, and hence the relative absorbance. The filter may be an electronic filter implemented in a processor or may be implemented as an electronic circuit in electronic communication with either the light source or an optical sensor. This frequency modulation has the advantage that it can remove effects of ambient light entering the waveguide. Time modulation of the sources can also be used to remove effects of ambient light entering the waveguide.

Figure 15 shows a configuration where the processor 1230 and memory unit 1232 form part of the controller 1220. The controller 1220 may also comprises additional interfacing circuitry blocks 1234 and 1236. The interfacing circuitry blocks are in electronic communication with the processor 1230. The interfacing circuit block 1234 is electrically coupled to the optical source 1214 and the interfacing circuit block 1236 is electrically coupled to the optical sensor 1216. The interfacing circuit blocks comprise suitable electronic components that allow interfacing between the various system components and also may include smoothing circuits, power regulation/management circuits and protection circuits e.g. surge protection circuits. The components of the controller 1220 shown in figure 15 are preferably formed in a single unit and may be disposed on a suitable Printed Circuit Board (PCB). The controller 1220 can also be used to control the operation and detect deformation or pressure/ force applied to one of the sensing apparatus disclosed herein.

Launching light from the optical sources i.e. light sources into the optical waveguides can be achieved in a number of ways. For example light can be focussed onto a planar end of the waveguide. Using an index matching fluid can reduce the effects of reflections from the step changes in the refractive index, as the light enters the waveguide.

Figure 16 shows an example of a configuration of a light source arrangement 1300. The light source arrangement 1300 comprises a light source 1304 that emits light. The light source may be any other suitable electromagnetic wave generator. The light source 1304 is embedded in a wedge 1306 of similar refractive index to the waveguide 1302 (i.e. light pipe). Light from the source 1304 embedded in the wedge 1306 will be directed into the waveguide 1302 since the wedge has a sufficiently shallow angle that total internal reflection will occur in the waveguide. In one example the angle of the wedge is less than 90 degrees and in a further example is less than 60 degrees. This manner of launching light can be particularly useful for rectangular or square cross section waveguides.

Figure 17 shows an example of a clamp 1308 used to clamp the waveguide 1302 to the wedge 1306 using a suitable clamp. The clamp 1308 holds the waveguide 1302 in contact with the wedge 1306 such that light is directed into the waveguide 1302 to achieve total internal reflection. The clamp 1308 can be any suitable clamp. For example, a soft hydraulic actuator or a mechanical clamp. The clamp 1308 may include a reflective surface to maximise guidance of the light into the waveguide 1302.

The sensing devices disclosed herein, as well the sensing apparatus provides a sensor for determining deformation and/or force applied that is more stable as it factors out unknown losses of light from the source. The sensing device operates on the wavelength or frequency dependent properties of a material thereby making the sensor less susceptible to interference from ambient light entering the light guide or any changes to the source intensity. The sensing principles disclosed herein provide for sensor technology that is based on the comparatively stable intrinsic absorbing/scattering optical properties of translucent materials. Such properties make the sensing device, apparatus and system disclosed herein substantially immune from electromagnetic interference and temperature changes. Further the sensing device can include a coating of opaque materials e.g. opaque elastomers to isolate at least the sensitive region from interfering light sources. The materials used to fabricate the sensing devices e.g. translucent silicone or polyurethane elastomers are relatively inexpensive and can be readily fashioned into many configurations. The sensing devices can be easily and cheaply mass prod uced. Further the sensing devices can be made to be flexible and stretchy (i.e. can be stretched many times their unextended length), and so can be fashioned into devices that can mould to irregular shaped objects or objects that move dynamically irregularly. The sensing devices can dynamically mould various bodies. The materials used to fabricate the sensing devices can be customised for the response required but also can be made from biocompatible materials allowing the sensor (i.e. sensing device or apparatus or system) to be used in medical applications such as implanted sensors or sensors within a body cavity. Further the sensing device, in particular the optical waveguide can be made flexible or malleable such that the electronics of the sensing device can remain remote from a patient while the waveguide is used on or inside the patient.

The technology is applicable to many length and time scales. Flexible light pipes can be manufactured down to micrometer scale. The response of absorbing/scattering and fluorescent materials to light is very fast. Communication technologies provide us with light sources and detectors that can respond at gigaHertz frequencies.

The optical properties of constituents can be tailored (e.g. by using coloured or fluorescent dyes) to create materials to suit the task. For example, if large displacements are required, a long section of relatively transparent material should be used as the sensitive absorbing/scattering medium. To measure very small displacements, a thin relatively opaque material should be used as the sensitive absorbing/scattering medium. The spectral absorbance of the dye can also be tailored to match the light sources, absorbing more of some sources than others. One can choose from a wide range of dyes with different spectral absorbance characteristics.

Further the response of absorbing and/or scattering and fluorescent materials to light is fast allowing for quick responses from the sensing devices.

Some exemplary applications of the sensing device or sensing apparatus can be integration into clothing at the fibre level in order to determine stretch or deformation at various points e.g. at joints of a person wearing the clothing. These can be used in rehabilitation in order to detect the amount of stretch (or deformation or loading) at a joint for example. Unlike electrical counterparts (e.g. resistive or capacitive stretch sensors), the sensing device is simple and inexpensive to use. The only electronic components are the source and sensor at the sensing device level, and an associated controller. Large arrays i.e. a sensing apparatus incorporating multiple sensing devices can be constructed using video technology. For example, the configurations shown in figures 7A and 7B where multiple independent sensing devices can be used. The advantage of using video photosensors is that these are generally relatively low in price and have a relatively high sampling rate, thus offering several independent deformation measurements (e.g. length or stretch measurements) using a single arrangement such as for example using a single chip construction. The sensing device can also be used to make disposable pressure sensor arrays or disposable pressure sensing components (that may incorporate one or more sensing devices) to measure dynamic pressure produced by the body e.g. an in-sole pressure array providing information and feedback about dynamics or a disposable pressure sensor array for monitoring pelvic floor pressure profiles in women, providing diagnostics and feedback about pelvic floor health.

The sensing device of the present invention is also advantageous because it may be used as a visual indicator of deformation due to a force being applied to it. The sensing device is an optical sensing device that can visually indicate deformation based on the change in intensity or the change in colour (i.e. wavelength or frequency) within the waveguide due to a force being applied to it. Similarly, the sensing apparatus may also be used to visually indicate a deformation occurring. This allows the sensing device and/or sensing apparatus disclosed herein to act as visual indicators of deformation due to forces. The sensing devices/sensing apparatus may be used as a safety indicator in hazardous environments or may be visual indicators to be mounted on people or in clothing to indicate deformation or forces.

The sensing device (i.e. sensing technology) disclosed herein provides a high adaptable device that can be used in a number of configurations for a number of different uses. The sensing device and apparatus disclosed herein is also advantageous because it can be customised for use in a number of different applications.

One or more components and functions illustrated in the figures may be rearranged and/or combined into a single component or embodied in several components without departing from the scope of the invention. Additional elements or components may also be added without departing from the scope of the invention. Various

combinations of the described sensing devices or sensing arrangements herein are also contemplated. Additionally, features described herein may be implemented in software, hardware and/or a combination thereof. The processor as described may include a combination of hardware, software and firmware modules. The processor and its associated components may be implemented or performed by a general purpose processor, a digital signal processor, an application specific integrated circuit (ASIC), a field programmable gate array (FPGA) or other programmable logic components, discrete gates or transistor logic, discrete hardware components or any combination thereof design to perform the functions or methods described herein. The memory unit may be any suitable storage memory e.g. read only memory, random access memory, magnetic disk storage mediums, optical storage mediums, flash memory or other machine non transitory machine readable mediums.

Preferred embodiments of the invention have been described by way of example only and modifications may be made thereto without departing from the scope of the invention.

Claims

1. A sensing device for sensing deformations comprising :

an optical source emitting light of at least two wavelengths or at least two frequencies;

an optical sensor; and

a waveguide including an inlet and an outlet,

wherein the optical source is positioned at or adjacent an inlet of the waveguide, the optical sensor is positioned at or adjacent an outlet, the waveguide configured to transmit light emitted by the optical source to the optical sensor, and

2. A sensing device according to claim 1 wherein the deformation of a portion of the sensing device is based on a relative relationship of the at least two wavelengths or the at least two frequencies.

3. A sensing device according to claim 1 wherein the relationship is a ratio of intensities of the at least two wavelengths or the at least two frequencies of light.

4. A sensing device according to claim 1 wherein the relationship is a change in intensities of the at least two wavelengths or the at least two frequencies of light.

5. A sensing device according to according to claim 1 or claim 3 wherein the deformation is related to a ratio of intensities of the at least two wavelengths or the at least two frequencies of light.

6. A sensing device according to according to any one of claims 1 to 5 wherein the deformation detected by the sensing device is a single axis deformation.

7. A sensing device according to any one of claims 1 to 6 wherein the optical source comprises a broadband optical source configured to emit white light.

8. A sensing device according to claim 7 wherein the optical source is a broadband LED or a broadband diode laser.

9. A sensing device according to claim 7 or claim 8 wherein the optical sensor comprises one or more wavelength sensitive optical sensors.

10. A sensing device according to claim 9 wherein the optical sensor comprises one or more wavelength sensitive photodetector.

11. A sensing device according to any one of claims 1 to 6 wherein the optical source comprises at least two optical sources, each optical source emitting light comprising a single wavelength or single frequency.

12. A sensing device according to any one of claims 1 to 6 wherein the optical source comprises a multi-wavelength optical source configured to generate light of the at least two wavelengths or at least two frequencies.

13. A sensing device according to claim 11 or claim 12 wherein the optical sensor is a wavelength insensitive optical sensor.

14. A sensing device according to claim 11 or claim 12 wherein the optical sensor is a wavelength insensitive photodetector.

15. A sensing device according to any one of claims 1 to 14 wherein waveguide is resiliently deformable.

16. A sensing device according to any one of claims 1 to 15 wherein the waveguide comprises a coloured region, the coloured region partially absorbing or attenuating light of one or more frequencies or one or more wavelengths.

17. A sensing device according to claim 16 wherein the coloured region forms a sensitive region and a deformation of the coloured region is determined based on the relationship of the at least two wavelengths or the at least two frequencies

18. A sensing device according to any one of claims 1 to 17 wherein the waveguide is an elongate and hollow member.

19. A sensing device according to claim 17 wherein the waveguide comprises a substantially circular or rectangular or triangular or oval shaped cross section.

20. A sensing device according to any one of claims 1 to 19 wherein the waveguide comprises an inner layer and an outer layer encasing the inner layer, wherein the inner layer comprises a higher refractive index than the outer layer.

21. A sensing device according to claim 20 wherein the inner layer is a tubular core or planar sheet.

22. A sensing device according any one of claims 1 to 21 wherein the waveguide may be folded or bent such that the optical source and optical sensor are collocated.

23. A sensing device according to any one of claims 1 to 21 wherein the waveguide comprises a reflective member positioned within the waveguide such that light received at the inlet from the optical source reflects off the reflective member and is directed to the outlet for detection by the optical sensor, and wherein the optical source and the optical sensor are located adjacent each other.

24. A sensing device according to any one of claims 1 to 23 wherein the waveguide comprises a substantially transparent or substantially translucent material.

25. A sensing device according to any one of claims 1 to 24 wherein the waveguide comprises a silicone or a poiyurethane or an elastomer material or a liquid contained in a solid tube, preferably an elastomeric tube.

26. A sensing device according to any one of the preceding claims wherein the light emitted by the optical source is in a visible light spectrum.

27. A sensing device according to any one of the preceding claims wherein the deformation is an axial or linear deformation.

28. A sensing device according to any one of the preceding claims wherein the deformation is a single axis deformation.

29. A sensing device according to any one of the preceding claims wherein the sensing device comprises:

a plurality of optical sources positioned at or adjacent the inlet of the waveguide, a plurality of optical sensors positioned at or adjacent the outlet of the waveguide,

30. A sensing device according to claim 29 wherein the waveguide is a substantially cylindrical member comprising a circular cross section and pair of opposing planar faces.

31. A sensing device according claim 30 wherein three optical sources are placed on one planar face, three optical sensors are positioned on an opposing planar face, the three optical sensors are located out of phase to the optical sources.

32. A sensing device according to claim 31 wherein the optical sensors are positioned 60 degrees out of phase with the optical sources.

33. A sensing apparatus for sensing deformation, sensing apparatus comprising; a plurality of sensing devices according to any one of claims 1 to 32 disposed on or within a substrate

a deformation of the sensing apparatus being based on a relative deformation of each of the plurality of sensing devices.

34. A sensing apparatus according to claim 33 wherein the deformation of the sensing apparatus is based on a comparative deformation of each sensing device relative to the other sensing devices within the sensing apparatus.

35. A sensing apparatus according to claim 33 or claim 34 wherein the plurality of sensing devices are arranged parallel to each other on or within the substrate material, wherein the sensing apparatus is configured to determine a bending deformation based on a relative deformation of each of the plurality of sensing devices.

36. A sensing apparatus according to claim 33 or claim 34 wherein the plurality of sensing devices are arranged in a helical arrangement on or within the substrate, wherein the sensing apparatus is configured to determine a torsion deformation based on a relative deformation of each of the plurality of sensing devices.

37. A sensing apparatus according to claim 33 or claim 34 wherein the plurality of sensing devices are arranged in a two dimensional array such that a plurality of sensing devices are arranged parallel to a first axis and a plurality of sensing devices are arranged parallel to a second axis wherein the first axis and second axis are transverse to each other.

38. A sensing apparatus according to claim 37 wherein a flexible, reflective material is disposed on the two dimensional array of sensing devices.

39. A sensing apparatus according to claim 33 wherein the sensing apparatus is configured to generate a signal indicative of a multi-axis deformation of the sensing apparatus, wherein the multi-axis deformation is determined based on the relative deformation of the sensing devices.

40. A sensing device for sensing deformation comprising :

an optical source configured to emit a light of two or more wavelengths, or of two or more frequencies; a light or optical sensor; and

i. a ratio of intensity of the two or more wavelengths or two or more

frequencies of light,

ii. a change in the intensity of the two or more wavelengths of light or two or more frequencies of light,

iii. a relative attenuation of the two or more wavelengths of light or two or more frequencies of light,

iv. an attenuation ratio of the two or more wavelengths of light or two or more frequencies of light,

v. a change in an attenuation ratio of the two or more wavelengths of light or two or more frequencies of light, and

41. A sensing system for sensing deformation comprising :

a sensing device according to any one of claims 1 to 32 or 40; and

a processor in electronic communication with the sensing device, wherein the processor is configured to receive a signal indicative of a deformation from the sensing device, and wherein the processor is further configured to determine a deformation based on a relationship of the at least two wavelengths or the at least two frequencies.

42. A sensing device for sensing deformations, the sensing device comprising :

a source configured to emit electromagnetic waves of two or more wavelengths or two or more frequencies,

a sensor configured to detect the emitted electromagnetic waves, and a waveguide including an inlet and an outlet,

43. A sensing device according to claim 42, wherein the deformation of a portion of the sensing device is based on a relative relationship of the two or more wavelengths.

44. The sensing device according to claim 43, wherein the relationship is at least one of:

i. a ratio of intensity of the two or more wavelengths or two or more

frequencies of the electromagnetic waves,

ii. a change in the intensity of the two or more wavelengths of the

electromagnetic waves or two or more frequencies of the electromagnetic waves,

45. The sensing device according to any one of claims 42 to 44, wherein the waveguide is an elongate member defining a lumen within the waveguide to transmit or propagate the electromagnetic waves of two or more wavelengths or two or more frequencies along the length of the waveguide.

46. A sensing device according to any one of claims 42 to 45, wherein the electromagnetic waves are any suitable waves along the electromagnetic spectrum.

47. A sensing device according to any one of claims 42 to 46, wherein the electromagnetic waves of two or more wavelengths or two or more frequencies is any one of:

a. visible light,

b. infrared,

c. microwave, and

d. ultraviolet.