Tactile sensor using elastomeric imaging

Abstract

A tactile sensor includes a photosensing structure, a volume of elastomer capable of transmitting an image, and a reflective skin covering the volume of elastomer. The reflective skin is illuminated through the volume of elastomer by one or more light sources, and has particles that reflect light incident on the reflective skin from within the volume of elastomer. The reflective skin is geometrically altered in response to pressure applied by an entity touching the reflective skin, the geometrical alteration causing localized changes in the surface normal of the skin and associated localized changes in the amount of light reflected from the reflective skin in the direction of the photosensing structure. The photosensing structure receives a portion of the reflected light in the form of an image, the image indicating one or more features of the entity producing the pressure.

What is claimed is: 
     
       1. A tactile sensor comprising:
 a photosensing structure;   a volume of elastomer capable of transmitting an image; and   a reflective skin covering said volume of elastomer, said reflective skin being illuminated through said volume of elastomer by one or more light sources, said reflective skin having particles that non-directionally reflect light incident on the reflective skin from within the volume of elastomer, said reflective skin being geometrically altered in response to pressure applied by an entity touching said reflective skin, said geometrical alteration causing localized changes in the surface normal of said skin and associated localized changes in the amount of light reflected from said reflective skin in the direction of said photosensing structure; wherein   said photosensing structure is positioned to receive a portion of said reflected light in the form of an image, said image indicating one or more features of the entity producing said pressure.   
     
     
       2. The tactile sensor of  claim 1 , wherein said volume of elastomer comprises silicone rubber, polyurethane, plastisol, thermoplastic elastomer, natural rubber, polyisoprene, polyvinyl chloride or a mixture thereof. 
     
     
       3. The tactile sensor of  claim 1 , wherein said volume of elastomer comprises a Shore A hardness between 5 and 90. 
     
     
       4. The tactile sensor of  claim 1 , wherein the volume of elastomer is in the form of a slab. 
     
     
       5. The tactile sensor of  claim 1 , wherein said photosensing structure comprises a camera. 
     
     
       6. The tactile sensor of  claim 1 , wherein said photosensing structure comprises an array of sensing elements. 
     
     
       7. The tactile sensor of  claim 1 , wherein said one or more features comprise roughness of said entity. 
     
     
       8. The tactile sensor of  claim 1 , wherein said one or more features comprise the location, amplitude, or direction of the applied pressure. 
     
     
       9. The tactile sensor of  claim 1 , wherein said one or more features comprise the shape, size, or profile of an object producing said pressure. 
     
     
       10. The tactile sensor of  claim 1 , wherein said one or more features comprise the motion or slip of a surface touching the reflective skin. 
     
     
       11. The tactile sensor of  claim 1 , wherein the sensor has physical properties that are similar to those of human skin. 
     
     
       12. The tactile sensor of  claim 1 , wherein the sensor is formed in the shape of a specified object. 
     
     
       13. The tactile sensor of  claim 1 , wherein the reflective skin is illuminated by two or more light sources of different colors. 
     
     
       14. A method of performing tactile sensing, comprising:
 (a) providing a volume of elastomer capable of transmitting an image;   (b) covering the elastomer with a reflective skin having an inner surface facing the elastomer and an outer surface, wherein the reflective skin comprises particles that non-directionally reflect light incident on the inner surface from within the volume of elastomer;   (c) illuminating the reflective skin through the volume of elastomer with one or more light sources, wherein at least a portion of the light is reflected by the inner surface of the reflective skin;   (d) contacting the outer surface of the reflective skin with an entity, wherein the contact produces pressure that geometrically alters the reflective skin, wherein the alteration causes localized changes in the inner surface of the reflective skin, and wherein the localized changes in the inner surface of the reflective skin cause associated localized changes in the light reflected from the inner surface of the reflective skin;   (e) positioning a photosensing structure to receive a portion of the light reflected from the inner surface of the reflective skin in the form of an image indicating one or more features of the entity contacting the outer surface of the reflective skin.   
     
     
       15. The method of  claim 14 , wherein said volume of elastomer comprises silicone rubber, polyurethane, plastisol, thermoplastic elastomer, natural rubber, polyisoprene, polyvinyl chloride or a mixture thereof. 
     
     
       16. The method of  claim 14 , wherein said volume of elastomer comprises a Shore A hardness between 5 and 90. 
     
     
       17. The method of  claim 14 , wherein the volume of elastomer is in the form of a slab. 
     
     
       18. The method of  claim 14 , wherein said photosensing structure comprises a camera. 
     
     
       19. The method of  claim 14 , wherein said photosensing structure comprises an array of sensing elements. 
     
     
       20. The method of  claim 14 , wherein said one or more features comprise roughness of said entity. 
     
     
       21. The method of  claim 14 , wherein said one or more features comprise the location, amplitude, or direction of the applied pressure. 
     
     
       22. The method of  claim 14 , wherein said one or more features comprise the shape, size, or profile of an object producing said pressure. 
     
     
       23. The method of  claim 14 , wherein said one or more features comprise the motion or slip of a surface touching the reflective skin. 
     
     
       24. The method of  claim 14 , wherein the sensor has physical properties that are similar to those of human skin. 
     
     
       25. The method of  claim 14 , wherein the sensor is formed in the shape of a specified object. 
     
     
       26. The method of  claim 14 , wherein the reflective skin is illuminated by two or more light sources of different colors. 
     
     
       27. A method of reconstructing a 3-dimensional shape of an object, the method comprising:
 providing a volume of elastomer capable of transmitting an image, the volume of elastomer having a reflective surface that reflects light incident on the reflective surface from within the volume of elastomer;   illuminating the reflective surface through the volume of elastomer with at least a first light source and a second light source, each light source disposed to illuminate the reflective surface from substantially different azimuths relative to each other;   contacting the reflective surface with an object to cause the reflective surface to deform in response to the contact by the object, the deformation causing localized changes in the surface normal of the reflective surface and associated localized changes in the amount of light from each of the light sources reflected from reflective surface;   receiving in a photosensing structure at least a portion of the light from the first light source reflected from the reflective surface in the form of a first image indicating one or more features of the object contacting the reflective surface;   receiving in the photosensing structure at least a portion of the light from the second light source reflected from the reflective surface in the form of a second image indicating one or more features of the object contacting the reflective surface, the first image differing from the second image; and   analyzing information about the one or more features indicated in the first and second images to estimate at least one of a surface normal and a surface height of the object at a plurality of positions on the object.    
     
     
       28. The method of claim 27, wherein the reflective surface comprises reflective particles bound to the elastomer. 
     
     
       29. The method of claim 27, wherein the reflective surface comprises reflective particles included in a paint, the paint being applied to the elastomer. 
     
     
       30. The method of claim 27, wherein the reflective surface comprises a reflective skin in contact with the elastomer. 
     
     
       31. The method of claim 30, wherein the reflective skin is bound to the elastomer. 
     
     
       32. The method of claim 27, the photosensing structure comprising a camera. 
     
     
       33. The method of claim 27, the reflective surface comprising reflective particles that reflect light substantially uniformly in all directions, the reflective particles causing the reflective surface to reflect light substantially non-directionally. 
     
     
       34. The method of claim 27, the reflective surface comprising flakes that exhibit at least one of surface roughness, irregular shape, and random alignment relative to each other, the reflective particles causing the reflective surface to reflect light moderately directionally. 
     
     
       35. The method of claim 27, the reflective surface comprising flakes that are substantially flat, have a mirror-like surface, and are substantially well aligned relative to each other, the reflective particles causing the reflective surface to reflect light highly directionally. 
     
     
       36. The method of claim 27, the photosensing structure comprising a first camera and a second camera, the first image based on light reflected from the reflective surface being received in the first camera and the second image based on light reflected from the reflective surface being received in the second camera. 
     
     
       37. The method of claim 27, the illuminating the reflective surface comprising alternating between:
 illuminating the reflective surface with the first light source and receiving in the photosensing structure at least a portion of the light from the first light source reflected from the reflective surface; and   illuminating the reflective surface with the second light source and receiving in the photosensing structure at least a portion of the light from the second light source reflected from the reflective surface.   
     
     
       38. The method of claim 27, wherein:
 the illuminating the reflective surface comprises illuminating the reflective surface simultaneously with each of the first and the second light sources;   the first light source provides light of a first color and the second light source provides light of a second color;   the photosensing structure comprises a camera responsive to light of the first color and to light of the second color; and   the analyzing information about the one or more features indicated in the first and second images comprises distinguishing between the first and second images based on the color of the light reflected from the reflective surface.   
     
     
       39. The method of claim 38, the photosensing structure comprising a first and a second camera, the first camera being responsive to light of the first color and the second camera being sensitive to light of the second color. 
     
     
       40. A sensor comprising:
 a volume of elastomer capable of transmitting an image, the volume of elastomer having a reflective surface that reflects light incident on the reflective surface from within the volume of elastomer, the reflective surface being deformable in response to pressure applied by an object touching the reflective surface, the deformations causing localized changes in the surface normal of the reflective surface and associated localized changes in the amount of light reflected from the reflective surface in the direction of a photosensing structure, the photosensing structure being disposed to receive a portion of the reflected light in the form of an image, the image indicating one or more features of the object producing said pressure;   at least a first light source and a second light source, each light source disposed to illuminate the reflective surface from within the volume of the elastomer, and each light source disposed to illuminate the reflective surface from substantially different azimuths relative to each other, the first light source producing a first image and the second light source producing a second image; and   a photometric stereo analyzer for receiving information about the one or more features indicated in the first and the second images, the analyzer estimating at least one of a surface normal and a surface height of the object at a plurality of positions on the object based on the information.   
     
     
       41. The tactile sensor of claim 40, wherein the reflective surface comprises reflective particles bound to the elastomer. 
     
     
       42. The tactile sensor of claim 40, wherein the reflective surface comprises reflective particles included in a paint, the paint being applied to the elastomer. 
     
     
       43. The tactile sensor of claim 40, wherein the reflective surface comprises a reflective skin in contact with the elastomer. 
     
     
       44. The tactile sensor of claim 43, wherein the reflective skin is bound to the elastomer. 
     
     
       45. The sensor of claim 40, the photosensing structure comprising a camera. 
     
     
       46. The sensor of claim 40, the reflective surface comprising reflective particles that reflect light substantially uniformly in all directions, the reflective particles causing the reflective surface to reflect light substantially non-directionally. 
     
     
       47. The sensor of claim 40, the reflective surface comprising flakes that exhibit at least one of surface roughness, irregular shape, and random alignment relative to each other, the reflective particles causing the reflective surface to reflect light moderately directionally. 
     
     
       48. The sensor of claim 40, the reflective surface comprising flakes that are substantially flat, have a mirror-like surface, and are substantially well aligned relative to each other, the reflective particles causing the reflective surface to reflect light highly directionally. 
     
     
       49. The sensor of claim 40, the photosensing structure comprising a plurality of cameras, each camera of the plurality being disposed at an orientation that differs from any other camera relative to the reflective surface. 
     
     
       50. The sensor of claim 40, further comprising an illumination controller for alternating between illuminating the reflective surface with the first light source and illuminating the reflective surface with the second light sources. 
     
     
       51. The sensor of claim 40, wherein:
 the first light source provides light of a first color and the second light source provides light of a second color;   the photosensing structure comprises a camera responsive to light of the first color and to light of the second color; and   the photometric stereo analyzer configured to estimate at least one of surface normal and the surface height of the object at a plurality of positions on the object based on the information by distinguishing between the first and the second images based on the color of the light reflected from the reflective surface.   
     
     
       52. The sensor of claim 51, the photosensing structure comprising a first and a second camera, the first camera being responsive to the light of the first color and the second camera being responsive to the light of the second color.