Optical target detection

Patent metadata

Field	Value
Publication number	US-9245445-B2
Application number	US-201213401738-A
Country	US
Kind code	B2
Filing date	Feb 21, 2012
Priority date	Feb 21, 2012
Publication date	Jan 26, 2016
Grant date	Jan 26, 2016

Abstract

An optically-based target detection system includes a holographic detection filter designed to produce a concentrated spot when a target is present.

First claim

What is claimed is:

1. An optical target detection system for detecting a presence of a target in a scene, the system comprising:
an optical subsystem including a holographic detection filter, the optical subsystem receiving light from the scene and producing an optical detection signal at a detection plane of the optical subsystem, the holographic detection filter resulting in a more concentrated optical detection signal when the target is present and a more dispersed optical detection signal when the target is not present; and
a light-distribution-sensitive detector located at the detection plane to receive the optical detection signal, the detector made of only a single pixel that produces a single electrical output, the detector producing a lower electrical output when the optical detection signal having a certain optical power incident on the pixel is more concentrated in its distribution across the pixel, and producing a higher electrical output when the optical detection signal having the same optical power incident on the pixel is less concentrated in its distribution across the pixel, wherein presence of the target is determined based on the electrical output.

2. The optical target detection system of claim 1 wherein the holographic detection filter is a correlation filter for the target.

3. The optical target detection system of claim 1 wherein the holographic detection filter is an inverse filter of the target.

4. The optical target detection system of claim 1 wherein the holographic detection filter is a programmable filter.

5. The optical target detection system of claim 1 wherein the holographic detection filter is a phase-only filter.

6. The optical target detection system of claim 1 wherein the holographic detection filter is a binary filter.

7. The optical target detection system of claim 1 wherein the optical subsystem includes imaging optics.

8. The optical target detection system of claim 1 wherein the detection plane is located at an image plane conjugate for the imaging optics, and the holographic detection filter is located at a Fourier plane conjugate.

9. The optical target detection system of claim 1 wherein optical subsystem receives incoherent light from the scene.

10. The optical target detection system of claim 1 wherein the target is based on a combination of component targets.

11. The optical target detection system of claim 1 wherein the target is based on QR codes.

12. The optical target detection system of claim 1 wherein the optical subsystem is passive and the light-distribution-sensitive detector does not require continuous power for continuous operation of the optical target detection system.

13. The optical target detection system of claim 1 further comprising:
an ambient light detector for receiving light from the scene and producing an output signal indicative of the average illumination of the scene; and
a target detection module coupled to the light-distribution-sensitive detector and to the ambient light detector, for determining presence of the target based on the electrical output of the light-distribution-sensitive detector and the output signal from the ambient light detector.

14. The optical target detection system of claim 1 wherein the light-distribution sensitive detector is a photodiode.

15. The optical target detection system of claim 1 wherein the holographic detection filter is space invariant.

16. The optical target detection system of claim 15 wherein the optical target detection system has a field of view of at least 30 deg×30 deg.

17. The optical target detection system of claim 1 wherein the optical target detection system is implemented within a mobile computer device.

18. The optical target detection system of claim 17 wherein the optical subsystem includes an optical element that functions as a combination of a lens and the holographic detection filter.

19. A method for detecting a presence of a target in a scene, the method comprising:
receiving light from the scene, the light propagating through an optical subsystem including a holographic detection filter;
producing an optical detection signal at a detection plane of the optical subsystem, the holographic detection filter resulting in a more concentrated optical detection signal when the target is present and a more dispersed optical detection signal when the target is not present;
receiving the optical detection signal at a light-distribution-sensitive detector, the detector made of only a single pixel that produces a single electrical output, the detector producing a lower electrical output when the optical detection signal having a certain optical power incident on the pixel is more concentrated in its distribution across the pixel and producing a higher electrical output when the optical detection signal having the same optical power incident on the pixel is less concentrated in its distribution across the pixel; and determining a presence of the target in the scene based on the electrical output.

20. A mobile computer device that includes an optical target detection system, the optical target detection system comprising:
an optical subsystem including a holographic detection filter, the optical subsystem receiving incoherent light from the scene and producing an optical detection signal at a detection plane of the optical subsystem, the holographic detection filter resulting in a more concentrated optical detection signal when the target is present and a more dispersed optical detection signal when the target is not present;
a light-distribution-sensitive detector located at the detection plane to receive the optical detection signal, the detector made of only a single pixel that produces a single electrical output, the detector producing a lower electrical output when the optical detection signal having a certain optical power incident on the pixel is more concentrated in its distribution across the pixel and producing a higher electrical output when the optical detection signal having the same optical power incident on the pixel is less concentrated in its distribution across the pixel;
an ambient light detector for receiving light from the scene and producing an output signal indicative of the average illumination of the scene; and
a target detection module coupled to the light-distribution-sensitive detector and to the ambient light detector, for determining presence of the target based on the electrical output of the light-distribution-sensitive detector and the output signal from the ambient light detector, wherein the light-distribution-sensitive detector is large enough to detect presence of the target over a field of view of at least 30 deg×30 deg.

Assignees

• Pavani Sri Rama Prasanna
• Hull Jonathan J
• Chemishkain Sergey
• Berkner Kathrin
• Ricoh Co Ltd

Inventors

• Pavani Sri Rama Prasanna
• Hull Jonathan J
• Chemishkain Sergey
• Berkner Kathrin

Classifications

• G08G1/166

  for active traffic, e.g. moving vehicles, pedestrians, bikes · CPC title

• G06E3/003

  forming integrals of products, e.g. Fourier integrals, Laplace integrals, correlation integrals; for analysis or synthesis of functions using orthogonal functions · CPC title

• G08G1/09623 Primary

  Systems involving the acquisition of information from passive traffic signs by means mounted on the vehicle (G08G1/0967 takes precedence) · CPC title

• G01V8/10

  Detecting, e.g. by using light barriers (by reflection from the object G01S17/00) · CPC title