Systems and methods for lensed and lensless optical sensing
A sensing device with an odd-symmetry grating projects near-field spatial modulations onto an array of closely spaced pixels. Due to physical properties of the grating, the spatial modulations are in focus for a range of wavelengths and spacings. The spatial modulations are captured by the array, and photographs and other image information can be extracted from the resultant data. Pixels responsive to infrared light can be used to make thermal imaging devices and other types of thermal sensors. Some sensors are well adapted for tracking eye movements, and others for imaging barcodes and like binary images. In the latter case, the known binary property of the expected images can be used to simplify the process of extracting image data.
1. A system for tracking movement of an eye, the system comprising:
an array of photoelements;
a grating to collect light reflected from the eye, the grating having a point spread function that focuses light from a point-source to a pattern spatially distributed across non-adjacent ones of the photoelements; and
a processor coupled to the array of photoelements to compute a location of the point source from features of the pattern.
2. The system of claim 1 , wherein the grating is a diffraction grating.
3. The system of claim 2 , wherein the grating comprises a zone plate.
4. The system of claim 2 , wherein the pattern comprises bright lines.
5. The system of claim 4 , wherein the lines form open curves.
6. The system of claim 1 , further comprising a light source to direct the light to the eye.
7. The system of claim 6 , wherein the light reflected from the eye comprises Purkinje spots, the processor to compute the locations of the Purkinje spots.
8. The system of claim 7 , the processor to compute positions of the eye from the locations of the Purkinje spots.
9. The system of claim 1 , wherein the grating is disposed over and in contact with the array.
10. The system of claim 9 , wherein the grating is integrated with the array.
11. The system of claim 1 , further comprising a frame to hold the grating and the array of photoelements near the eye.
12. The system of claim 11 , further comprising a light source supported by the frame and positioned to direct the light to the eye.
13. The system of claim 12 , wherein the light comprises infrared light of a wavelength band.
14. The system of claim 13 , further comprising a filter adjacent the grating to block second light outside the wavelength band.
15. The system of claim 14 , further comprising a lens, supported by the frame, to admit third light from a scene to the eye.
16. The system of claim 15 , further comprising a second filter adjacent the lens to block fourth light within the wavelength band.
17. The system of claim 11 , further comprising an image sensor fixed to the frame to image a scene opposite the eye.
18. The system of claim 17 , the processor to correlate the movement of the eye with the scene.
19. The system of claim 11 , wherein the frame supports the processor.