Fluid tactile sensors
A topographical measurement system may include a tactile sensor using a contained fluid as an imaging medium.
1. A system comprising:
a fluid tactile sensor including:
a substrate, the substrate formed of a rigid material and the substrate including a window of optically transparent material,
a membrane, the membrane formed of a flexible, elastic sheet of a material, and the membrane having a surface, wherein the membrane is an opaque, reflective membrane with a predetermined reflectance suitable for supporting topographical imaging of the membrane independent of optical properties of a target surface,
a reservoir having a volume contained at least in part within the substrate and the membrane, and
an imaging medium within the reservoir, the imaging medium including an optically transparent fluid; and
an imaging system including:
an illumination source directed through the window of the substrate toward the surface of the membrane when the membrane is positioned for use within an imaging volume of the imaging system, and
an imaging device positioned to capture images of the surface of the membrane through the window of the substrate when the membrane is placed for use within the imaging volume of the imaging system.
2. The system of claim 1 , further comprising a processor configured by computer executable code stored in a memory to acquire images from the imaging system and to calculate a quantitative surface topography of the target surface contacting the membrane.
3. The system of claim 1 , wherein the illumination source includes a structured light source.
4. The system of claim 3 , wherein the structured light source creates a three-dimensional illumination pattern within the imaging volume of the reservoir.
5. The system of claim 1 , further comprising a cartridge housing the fluid tactile sensor, the cartridge removable from and replaceable to the imaging system.
6. The system of claim 1 , further comprising one or more containing walls mechanically coupling the membrane to the substrate.
7. The system of claim 1 , wherein the window includes at least one of a glass, a polycarbonate, an acrylic, a polystyrene, a polyurethane, or an optically transparent epoxy.
8. The system of claim 1 , wherein the window has a first index of refraction matched to a second index of refraction of the imaging medium within the reservoir.
9. The system of claim 1 , wherein the imaging medium includes at least one of a gas and a liquid.
10. The system of claim 1 , wherein the membrane is formed of an elastic polymer.
11. The system of claim 1 , further comprising an optical pattern on the membrane visible to the imaging device of the imaging system through the window.
12. The system of claim 1 , wherein the illumination source includes at least one of a laser and a light emitting diode.
13. The system of claim 1 , wherein the imaging system uses two or more imaging modalities including at least one of photometric stereo imaging, multi-view stereo imaging, structured light imaging, and focus stacking.
14. The system of claim 1 , further comprising a pressure sensor coupled to the reservoir and configured to measure a pressure of the imaging medium within the reservoir.
15. The system of claim 1 , wherein the membrane has an optically reflective coating.
16. The system of claim 1 , wherein the membrane has a patterned surface.
17. The system of claim 1 , wherein the membrane has an exterior surface facing away from the window, the exterior surface including a friction-reducing coating.
18. The system of claim 1 , wherein the window includes one or more light shaping features for at least one of filtering, polarizing, focusing, or diffusing light passing through the window.
19. The system of claim 1 , wherein the imaging system includes a diffractive optical element positioned to create a three-dimensional illumination pattern from the illumination source within the imaging volume.
20. The system of claim 1 , wherein the imaging device includes one or more of a photometric stereo imaging system and a triangulation-based 3D reconstruction system.