Methods and Apparatus for Virtual Sensor Array

Patent metadata

Field	Value
Publication number	US-2016014393-A1
Application number	US-201514795113-A
Country	US
Kind code	A1
Filing date	Jul 9, 2015
Priority date	Jul 9, 2014
Publication date	Jan 14, 2016
Grant date	—

Abstract

A time-of-flight camera images an object around a corner or through a diffuser. In the case of imaging around a corner, light from a hidden target object reflects off a diffuse surface and travels to the camera. Points on the diffuse surface function as a virtual sensors. In the case of imaging through a diffuser, light from the target object is transmitted through a diffusive media and travels to the camera. Points on a surface of the diffuse media that is visible to the camera function as virtual sensors. In both cases, a computer represents phase and intensity measurements taken by the camera as a system of linear equations and solves a linear inverse problem to (i) recover an image of the target object; or (ii) to compute a 3D position for each point in a set of points on an exterior surface of the target object.

First claim

What is claimed is:

1 . An apparatus comprising, in combination:
(a) an active light source; (b) a time-of-flight camera, which camera is configured for taking measurements of phase and amplitude of incident light at each pixel, respectively, in a set of pixels of the camera, which incident light comprises amplitude-modulated continuous-wave light that (i) is emitted by the active light source and reflects from the object, and then (ii) travels to a diffusely reflective surface, and then (iii) reflects from the diffusely reflective surface and travels to the time-of-flight camera; and (c) a computer for performing a calculation that computes, for each respective point in a set of points on a surface of the object, a 3D position of the respective point, wherein the calculation involves solving a system of linear equations that represents the measurements.

2 . The apparatus of claim 1 , wherein the calculation includes solving Equation 17.

3 . The apparatus of claim 1 , wherein the calculation includes solving Equation 18.

4 . The apparatus of claim 1 , wherein the calculation includes executing a pseudoinverse algorithm.

5 . The apparatus of claim 1 , wherein the calculation includes executing a basis pursuit denoising algorithm.

6 . The apparatus of claim 1 , wherein the calculation includes determining a distance traveled by light based on a phase difference between light incident on the time-of-flight camera and a reference signal.

7 . The apparatus of claim 1 , wherein the calculation includes computing an image of the object in real time.

8 . The apparatus of claim 1 , wherein the diffusely reflective surface is not a Lambertian reflector.

9 . The apparatus of claim 1 , wherein:
(a) an occluder prevents light from traveling in a straight line from the object to the time-of-flight camera; and (b) the light source is on the same side of the occluder as the object.

10 . The apparatus of claim 1 , wherein:
(a) an occluder prevents light from traveling in a straight line from the object to the time-of-flight camera; and (b) the light source is on the same side of the occluder as the time-of-flight camera.

11 . The apparatus of claim 1 , wherein the system of linear equations is represented by a matrix.

12 . An apparatus comprising, in combination:
(a) an active light source; (b) a time-of-flight camera, which camera is configured for taking measurements of phase and amplitude of incident light at each pixel, respectively, in a set of pixels of the camera, which incident light comprises amplitude-modulated continuous-wave light that (i) is emitted by the active light source and reflects from the object, and then (ii) travels through a diffuse media, and (iii) then travels to the time-of-flight camera; and (c) a computer for performing a calculation that computes, for each respective point in a set of points on a surface of the object, a 3D position of the respective point, wherein the calculation involves solving a system of linear equations that represents the measurements.

13 . The apparatus of claim 12 , wherein the diffuse media comprises a solid diffuser.

14 . The apparatus of claim 12 , wherein the diffuse media comprises an aerosol, colloid, suspension or emulsion.

15 . The apparatus of claim 12 , wherein the system of linear equations is represented by a matrix.

16 . A method comprising, in combination:
(a) a light source emitting amplitude-modulated continuous-wave light which light, after leaving the light source (i) is at least partially scattered during transmission through a diffuse media or during diffuse reflection, and (ii) then travels to a time-of-flight camera; (b) the time-of-flight camera taking measurements at each pixel, respectively, in a set of pixels of the camera, of phase and amplitude of the light; and (c) a computer performing a calculation that computes, for each respective point in a set of points on a surface of the object, a 3D position of the respective point, wherein the calculation involves solving a system of linear equations that represents the measurements.

17 . The method of claim 16 , wherein the light reflects from a diffusely reflective surface during the diffuse reflection.

18 . The method of claim 16 , wherein the light is transmitted through a diffuse media that comprises a solid diffuser, aerosol, colloid, suspension or emulsion.

19 . The method of claim 16 , wherein the calculation includes solving Equation 17.

20 . The method of claim 16 , wherein the system of linear equations is represented by a matrix.

Assignees

• Kadambi Achuta
• Zhao Hang
• Shi Boxin
• Bhandari Ayush
• Raskar Ramesh
• Massachusetts Inst Technology

Inventors

• Kadambi Achuta
• Zhao Hang
• Shi Boxin
• Bhandari Ayush
• Raskar Ramesh

Classifications

• H04N2213/003

  Aspects relating to the "2D+depth" image format · CPC title

• H04N13/0253 Primary

  Electricity · mapped topic

• G01S17/89

  for mapping or imaging · CPC title

• G01S17/003 Primary

  Bistatic lidar systems; Multistatic lidar systems · CPC title

• G01S17/894

  Three-dimensional [3D] imaging with simultaneous measurement of time-of-flight at a two-dimensional [2D] array of receiver pixels, e.g. time-of-flight cameras or flash lidar · CPC title