Methods and Systems for Distinguishing Point Sources

• US 20180275323A1
• Filed: 03/15/2018
• Published: 09/27/2018
• Est. Priority Date: 03/24/2017
• Status: Active Grant

• Current Assignee: Rambus Inc.
• Original Assignee: Rambus Inc.
• Inventors: Schneider, Alexander C., Gill, Patrick R.
• Granted Patent: US 10,641,934 B2
• Time in Patent Office: Days
• CPC Class Codes: G02B 5/1842 Gratings for image generation G02B5/1847 takes precedence
• CPC Class Codes: G02F 1/01 for the control of the intensity, phase, polarisation or colour G02F1/29, G02F1/35 take precedence
• CPC Class Codes: G06T 2207/20164 Salient point detection; Corner detection
• CPC Class Codes: G06T 7/11 Region-based segmentation
• CPC Class Codes: H04N 25/44 by partially reading an SSIS array

Abstract

An optical smart sensor combines a phase grating with a rolling shutting to distinguish between modulated point sources. Employing a phase grating in lieu of a lens dramatically reduces size and cost, while using timing information inherent to imaging techniques that used a rolling shutter allows the smart sensor to distinguish point sources quickly and easily using a single frame of image data.

Claims

1. An optical system to sense incident light, the optical system comprising:

an optic exhibiting a point-spread function, the optic to produce a point-spread response responsive to the incident light;

rows of pixels, each pixel to sample a respective region of the point-spread response, each of the rows of pixels producing a row of sample values, the rows of sample values providing an image frame; and

at least one processor to;

read the rows of sample values within the image frame; and

use a difference in relative intensity between the successively read rows of sample values within the image frame to identify modulation information.

2. The optical system of claim 1, wherein the incident light comprises point sources, the at least one processor to distinguish the point sources responsive to the modulation information.

3. The optical system of claim 1, further comprising memory to store a kernel representative of the point-spread function of the optic.

4. The optical system of claim 3, the at least one processor to detect a point-spread function from the rows of sample values and align the point-spread function with the kernel before comparing each of the rows of sample values with a corresponding slice of the kernel.

5. The optical system of claim 3, wherein demodulating the intensity values comprises comparing each of the rows of sample values to a corresponding slice of the kernel.

6. The optical system of claim 3, the memory to store a modulation signature, the at least one processor to compare the modulation information to the modulation signature.

7. The optical system of claim 6, the memory to store a second modulation signature, each of the first-mentioned and second modulation signatures corresponding to a respective one of a first illumination source and a second illumination source, the at least one processor to distinguish between the first illumination source and the second illumination source using the modulation information.

8. The optical system of claim 1, further comprising a modulated illumination source to produce at least a portion of the incident light.

9. The optical system of claim 8, the modulated illumination source exhibiting a modulation period.

10. The optical system of claim 9, the at least one processor to read each successive row a row time less than the modulation period after a prior row, and to read all of the rows of sample values over a frame time greater than the modulation period.

11. The optical system of claim 9, further comprising a second modulated illumination source exhibiting a second modulation period different from the first-mentioned modulation period.

12. The optical system of claim 11, the at least one processor to read each successive row a row time less than the first-mentioned modulation period and the second modulation period after a prior row, and to read all of the rows of sample values over a frame time greater than the first-mentioned modulation period and the second modulation period.

13. The optical system of claim 1, the point-spread response illuminating R of the pixels and defining a convex hull over S of the pixels, wherein S>

2R.

14. A method for identifying a modulated point source, the method comprising:

exposing rows of pixels to a pattern from the modulated point source;

sampling the pattern using the rows of pixels;

locating a point-spread response in the sampled pattern, the sampled pattern having a row of sample values for each of the rows of pixels;

accumulating an intensity value for each of the rows of sample values; and

demodulating the accumulated intensity values.

15. The method of claim 14, further comprising cropping the point-spread response before accumulating the intensity values.

16. The method of claim 14, wherein locating a point-spread response in the sampled pattern comprises correlating the sampled pattern with a kernel representative of the point-spread response.

17. The method of claim 16, further comprising storing the kernel.

18. The method of claim 14, further comprising forming the pattern from light emanating from a scene through a phase grating.

19. The method of claim 14, further comprising successively sampling the rows of of pixels.

20. The method of claim 19, wherein the modulated point source exhibits a modulation period, and wherein each successive row is sampled a row time less than the modulation period after a prior row.

21. The method of claim 20, wherein all of the rows are sampled over a frame time greater than the modulation period.

22. An optical system to sense incident light, the optical system comprising:

an optical grating exhibiting a point-spread function, the optical grating to produce a diffractive response to the incident light;

rows of pixels, each pixel to sample a respective region of the diffractive response, each of the rows of pixels producing a row of sample values; and

means for a processor to use a difference in relative intensity between successively read rows of sample values within a frame to identify modulation information.