Depth measurement using a phase grating

Patent metadata

Field	Value
Publication number	US-10317205-B2
Application number	US-201615548745-A
Country	US
Kind code	B2
Filing date	Jan 25, 2016
Priority date	Feb 24, 2015
Publication date	Jun 11, 2019
Grant date	Jun 11, 2019

Abstract

Binocular depth-perception systems use binary, phase-antisymmetric gratings to cast point-source responses onto an array of photosensitive pixels. The gratings and arrays can be manufactured to tight tolerances using well characterized and readily available integrated-circuit fabrication techniques, and can thus be made small, cost-effective, and efficient. The gratings produce point-source responses that are large relative to the pitch of the pixels, and that exhibit wide ranges of spatial frequencies and orientations. Such point-source responses make it easy to distinguish the point-source responses from fixed-pattern noise the results from spatial frequencies of structures that form the array.

First claim

What is claimed is:

1. A method of measuring a depth to an object in a scene, the method comprising:
receiving light in a wavelength band of interest from the scene at a phase grating, the phase grating inducing near-field spatial modulations producing a diffraction pattern;
capturing an image of the diffraction pattern induced by the phase grating;
computing a disparity between the image of the diffraction pattern induced by the near-field spatial modulations and a reference; and
estimating the depth to the object based on the disparity between the image of the diffraction pattern induced by the near-field spatial modulations and the reference.

2. The method of claim 1 , wherein the phase grating is a first phase grating, the method further comprising:
receiving the light from the scene at a second phase grating, the second phase grating inducing second near-field spatial modulations producing a second diffraction pattern;
capturing a second image of the second diffraction pattern; and
using the second image as the reference.

3. The method of claim 2 , wherein estimating the depth comprises computing a distance between the image and the second image.

4. The method of claim 1 , further comprising shining a laser source of the light on the object.

5. The method of claim 4 , further comprising filtering out second light outside the wavelength band of interest.

6. The method of claim 5 , wherein the filtering uses at least one of a color filter and a cross-polarized filter.

7. The method of claim 1 , wherein capturing the image comprises sampling the diffraction pattern with an array of pixels of a pixel pitch.

8. The method of claim 7 , wherein computing the disparity comprises measuring a lateral shift of the diffraction pattern on the pixels.

9. A method of measuring a depth to an object in a scene, the method comprising:
receiving light in a wavelength band of interest from the scene at a phase grating, the phase grating inducing near-field spatial modulations producing a diffraction pattern;
capturing an image of the diffraction pattern;
computing a disparity between the image and a reference; and
estimating the depth to the object based on the disparity;
wherein capturing the image comprises sampling the diffraction pattern with an array of pixels of a pixel pitch; and
wherein the diffraction pattern produces a point-source response with a maximum dimension of at least six times the pixel pitch on the array of pixels and features with smaller dimensions less than a third the maximum dimension.

10. The method of claim 9 , wherein the image includes band-limited noise at spatial frequencies that correspond to known attributes of the array of pixels, the method further comprising filtering out the band-limited noise at those frequencies.

11. The method of claim 10 , wherein computing the disparity comprises computing a Fourier cross-correlation of the captured image.

Assignees

• Rambus Inc

Inventors

• Gill Patrick R

Classifications

• G02B27/1086

  operating by diffraction only · CPC title

• G01C3/14 Primary

  with binocular observation at a single point, e.g. stereoscopic type (G01C3/20 takes precedence) · CPC title

• H04N13/10

  Processing, recording or transmission of stereoscopic or multi-view image signals · CPC title

• G06T7/593

  from stereo images · CPC title

• H04N13/271

  wherein the generated image signals comprise depth maps or disparity maps · CPC title