Stress and displacement sensors and methods of sensing
Sensors include an optical source configured to emit a beam directed to an opposing surface having a reflectance pattern, and an optical detector situated in relation to the optical source to detect a portion of the beam reflected by the opposing surface and to produce an output signal that varies based on (i) a relative displacement between the reflectance pattern and the optical detector and (ii) a spatially variable reflectance resulting from the relative displacement. Reflectance patterns can be spatially variable and/or randomly arranged. Displacements in a compressive or tensile direction can be detected. Methods of operation and fabrication of sensors are also disclosed.
1 . A sensor, comprising:
an optical source situated in relation to a first surface and configured to emit a beam directed to an opposing surface having a spatially variable reflectance pattern; and
an optical detector that comprises a single detection element situated in relation to the optical source to detect a portion of the beam reflected by the opposing surface and to produce an output signal that varies based on (i) a relative displacement between the reflectance pattern and the optical detector and (ii) a spatially variable reflectance resulting from the relative displacement, and that provides multi-axis displacement information along perpendicular shear axes.
2 . The sensor of claim 1 , further comprising an intermediate layer situated adjacent to the optical source and optical detector, wherein the layer is configured to deform to provide the displacement through a mechanical coupling with the opposing surface.
3 . The sensor of claim 2 , wherein the intermediate layer includes one or more windows situated to receive and transmit the beam and the reflected portion through the one or more windows.
4 . The sensor of claim 2 , wherein the intermediate layer comprises an elastomer transducer layer.
5 . The sensor of claim 4 , wherein the elastomer transducer layer comprises a thickness and curing characteristics configured to define a shear modulus.
6 . The sensor of claim 2 , further comprising a sensor housing configured to support the optical source, optical detector, and/or intermediate layer in fixed relation to each other.
7 . The sensor of claim 6 , further comprising a base plate attached to the sensor housing, and/or intermediate layer, wherein the base plate comprises the opposing surface.
8 . The sensor of claim 6 , wherein the optical detector comprises an aperture mask configured to define the amount of the detected portion by controlling the amount of area of the opposing surface viewed by the optical detector.
9 . The sensor of claim 8 , wherein the spatially variable reflectance pattern comprises a repeating reflectance pattern and the aperture mask comprises a repeating aperture mask pattern associated with the repeating reflectance pattern.
10 . The sensor of claim 9 , wherein respective repetition periods of the repeating reflectance pattern and repeating reflectance pattern are configured to provide a tolerance for recalibrating the sensor after a slip displacement between the optical detector and the opposing surface.
11 . The sensor of claim 1 , wherein the spatially variable reflectance pattern comprises a spatially variable color reflectance pattern configured to reflect light by different amounts according to the spatially variable color.
12 . The sensor of claim 11 , wherein the spatially variable color reflectance pattern comprises a first pattern area having a first color profile, a pair of second pattern areas having a common second color profile and situated on opposing sides of the first pattern area along a first shear axis, and a pair of third pattern areas having a common third color profile and situated on opposing sides of the first pattern area along a second shear axis perpendicular to the first shear axis.
13 . The sensor of claim 12 , wherein the spatially variable color reflectance pattern further comprises four fourth pattern area having a fourth color profile having a reflectance common with the second and third color profiles, wherein the four fourth pattern areas are situated in a corner relationship to the first pattern area and the second and third opposing pattern areas.
14 . The sensor of claim 12 , wherein the optical source comprises a red, green, blue (RGB) light emitting diode (LED).
15 . The sensor of claim 14 , wherein the first color profile is a green color configured to reflect the green light of the RGB LED, the second color profile is one of blue or red color configured to reflect the corresponding blue or red light of the RGB LED, and the third color profile is other one of the blue or red color configured to reflect the corresponding blue or red light of the RGB LED, wherein the fourth color profile is a magenta color configured to reflect both the blue and the red light of the RGB LED.
16 . The sensor of claim 1 , further comprising a processor and memory configured with processor-executable instructions that cause the processor to:
vary the spectral content of the beam produced by the optical source over time,
receive the output signal from the optical detector and associate different output signal times with the timing of the variable spectral content, and
determine a reflectance change associated with the relative displacement.
17 . The sensor of claim 16 , wherein the memory is configured with processor-executable instructions that cause the processor to measure, based on the reflectance change, a shear stress and/or displacement between (i) the opposing surface and the (ii) optical source and optical detector.
18 . The sensor of claim 1 , wherein the spatially variable reflectance pattern comprises a spatially variable gray scale reflectance pattern configured to reflect light by different amounts according to an intensity dependent gray scale spatial variation.
19 . The sensor of claim 1 , wherein the optical source comprises a white light source.
20 . The sensor of claim 1 , wherein the optical detector comprises one or more optical filters configured to attenuate light outside of a selected wavelength or wavelength range.
21 . The sensor of claim 20 , wherein the one or more optical filters comprise a plurality of bandpass filters configured to attenuate different wavelengths or wavelength ranges of a spectrum of light of the beam reflected by the opposing surface.
22 . The sensor of claim 20 , further comprising a processor and memory configured with processor-executable instructions that cause the processor to:
receive the output signal from the optical detector, wherein the optical detector is configured to detect a variation of spectral content of the reflected beam based on the optical filters, and
determine a reflectance change associated with the relative displacement and the detected variation of spectral content.
23 . The sensor of claim 22 , wherein the memory is configured with processor-executable instructions that cause the processor to measure, based on the reflectance change, a shear stress and/or displacement between (i) the opposing surface and the (ii) optical source and optical detector.
24 . The sensor of claim 1 , wherein the optical detector comprises a transducer configured to provide an output signal comprising a variable electrical quantity.
25 . The sensor of claim 1 , wherein the opposing surface comprises an integral or attached part of an object.
26 . The sensor of claim 1 , wherein the opposing surface comprises an adhesive layer arranged on one or both of a side presenting the opposing surface and a side opposite the side presenting the opposing surface.
27 . The sensor of claim 26 , wherein the adhesive layer is configured to adhere to a sensor housing or an elastomer transducer layer arranged between the sensor housing and the opposing surface;
wherein the adhesive layer is configured to adhere the side opposite the side presenting the opposing surface, to a shearing surface.
28 . The sensor of claim 1 , wherein the opposing surface comprises a randomized pixel pattern.
29 . The sensor of claim 28 , wherein the randomized pixel pattern is configured to provide a variation in the output signal through the relative displacement, wherein the variation is configured to provide a discrimination between a positive and negative directionality based on the randomized pixel pattern and a data classifier.
30 . A prosthesis, comprising the sensor of claim 1 .
31 . The prosthesis of claim 30 , wherein the opposing surface is arranged on a residual limb, and wherein the prosthesis comprises a prosthetic socket and the sensor housing is embedded within the socket.
32 . A shoe comprising the sensor of claim 1 , wherein the opposing surface is arranged at an insole of the shoe such that it is facing down towards a midsole, and wherein the sensor housing is embedded within a midsole of the shoe.
33 . A method, comprising:
emitting a beam from an optical source and directing the beam to an opposing surface having a spatially variable reflectance pattern; and
with a single detection element of an optical detector situated in relation to the optical source, detecting a portion of the beam reflected by the opposing surface and producing an output signal that varies based on (i) a relative displacement between the reflectance pattern and the optical detector and (ii) a spatially variable reflectance resulting from the relative displacement and that provides multi-axis displacement information along perpendicular shear axes.