Spatial symmetry cueing image processing method and apparatus

• US 5,020,111 A
• Filed: 10/14/1988
• Issued: 05/28/1991
• Est. Priority Date: 10/14/1988
• Status: Expired due to Fees

• Current Assignee: United States Of America As Represented By The Secretary Of The Army (Government of the United States of America)
• Original Assignee: The United States Of America As Represented By The Secretary Of The Army
• Inventors: Weber, Bruce A.
• Primary Examiner(s): Bovernick, Rodney B.
• Assistant Examiner(s): Parsons, David R.
• Application Number:
  US07/260,424
• Time in Patent Office: 956 Days
• Field of Search: 382/36, 382/42, 382/46, 382/31, 350/3.64, 350/162.12, 350/162.13, 350/162.14, 364/822
• US Class Current: 382/211
• CPC Class Codes: G06V 10/88 Image or video recognition using optical means, e.g. reference filters, holographic masks, frequency domain filters or spatial domain filters

Abstract

An optical correlation method and apparatus recognizes and locates specific patterns in a scene based on the spatial symmetries associated with that pattern. An input scene is divided into two identical scenes, one of which plays the role of the input scene and the other the role of the filter scene. The filter image is passed through a spatial operator before being sent, along with the input image, to a real-time correlator. The real-time output from the correlator is compared to the input scene. Bright spots or regions in the correlation image represent objects with symmetry. This technique does not depend on comparison of the received image with a standard or stored image, consequently, it overcomes the traditional handicap of sensitivity to both the aspect and range of the viewer.

Claims

1. A method of finding man-made objects in an arbitrary scene comprising the steps of:

detecting an image of said arbitrary scene;

creating a duplicate representation of said image;

performing a symmetry transformation on said duplicate representation forming a symmetry transformed duplicate representation;

performing a crosscorrelation between said image and said symmetry transformed duplicate representation; and

identifying the presence of said man-made object in said image by matching crosscorrelation information with said image.

2. The method of finding man-made objects in an arbitrary scene as defined in claim 1 wherein the step of forming a duplicate representation of said arbitrary scene comprises the steps of:

edge enhancing said image; and

forming a duplicate representation of said edge enhanced image.

3. The method of finding man-made objects in an arbitrary scene as defined in claim 1 wherein the step of performing symmetry transform on said duplicate representation comprises the steps of:

generating a Fourier transform of said duplicate representation;

dividing said Fourier transform of said duplicate representation image into its original magnitude component and its phase component;

changing said original magnitude component to a unity magnitude component;

forming a duplicate of said unity magnitude component and said original phase component;

spatial frequency transforming said duplicate representation in accordance with a particular spatial symmetry test.

4. The method of finding man-made objects in an arbitrary scene as defined in claim 3 wherein the step of performing a crosscorrelation comprises the steps of:

multiplying said spatial frequency transformed duplicate of said unity magnitude component and said original phase component with said Fourier transform of said duplicate representation forming a product;

generating an inverse Fourier transform of said product; and

generating crosscorrelation information by squaring the magnitude of said inverse Fourier transform of said product.

5. The method of finding man-made objects in an arbitrary scene as defined in claim 1 wherein the step of forming an image of said arbitrary scene comprises the step of:

digitizing said image of said arbitrary scene for viewing.

6. The method of finding man-made objects in an arbitrary scene as defined in claim 5 wherein the step of forming a duplicate representation of said arbitrary scene comprises the steps of:

generating a Fourier transform of said digitized image of said arbitrary scene;

dividing said Fourier transform of said digitized input image into its original magnitude component and its original phase component; and

generating a duplicate of said original phase component.

7. The method of finding man-made objects in an arbitrary scene as defined in claim 6 wherein the step of performing a symmetry transform on said duplicate representation comprises the steps of:

generating a spatial symmetry testing Fourier filter component by spatial frequency transforming said duplicate of said original phase component;

impressing electronically on a first spatial light modulator said symmetry testing Fourier filter component; and

impressing electronically on a second spatial light modulator said original phase component of said Fourier transform of said digitized input image.

8. The method of finding man-made objects in an arbitrary scene as defined in claim 7 wherein the step of performing crosscorrelation between said image and said symmetry transformed duplicate representation comprises the steps of:

producing a beam of coherent light;

directing said beam of coherent light to said first spatial light modulator;

reflecting said beam of coherent light off said first spatial light modulator;

directing said beam of coherent light, after it has reflected off said first spatial light modulator, to said second spatial light modulator;

reflecting scatteringly said beam of coherent light off said second spatial light modulator if there are matches between said original phase component and said symmetry testing phase component;

directing said beam of coherent light, after it has reflected scatteringly off said second spatial light modulator, to a lens;

generating an inverse Fourier transform of said beam of coherent light by passing said beam through said lens.

9. A method of cueing in real time the presence of an object or object part having symmetry within an arbitrary scene comprising the steps of;

forming an input image from said arbitrary scene for viewing;

generating a Fourier transform of said input image;

dividing said Fourier transform of said input image into its original magnitude values and its original phase values;

changing said original magnitude values to a new value of unity;

forming a duplicate of said original phase values;

generating a symmetry testing Fourier filter by spatial frequency transforming said duplicate of said original phase values and said unity magnitude values;

crosscorrelating said symmetry testing Fourier filter with said unity magnitude values and said original phase values; and

forming a crosscorrelation image from said crosscorrelation of said symmetry testing Fourier filter with said original magnitude values and said original phase values;

whereby bright regions in said crosscorrelation image represent objects or object parts having symmetry in said arbitrary scene.

10. A method of cueing in real time the presence of an object or object part having symmetry within an arbitrary scene comprising the steps of;

forming an input image of said arbitrary scene on a first plane;

forming a duplicate of said input image on a second plane maintaining spatial orientation;

spatially transforming said duplicate of said input image in relation to said input image;

crosscorrelating said spatially transformed duplicate of said input image with said input image using Fourier transforms in spatial frequency space; and

forming a crosscorrelation image from said crosscorrelation of said spatially transformed duplicate of said input image with said input image for comparison with said input image;

whereby bright regions in said crosscorrelation image represent objects or object parts having symmetry in said arbitrary scene.

11. A method of cueing in real time the presence of an object or object part having symmetry within an arbitrary scene comprising the steps of;

digitizing an input image from said arbitrary scene for viewing;

forming a Fourier transform of said digitized input image;

dividing said Fourier transform of said digitized input image into its original magnitude component and its original phase component;

forming a duplicate of said original phase component;

generating a spatial symmetry testing Fourier component by spatial frequency transforming said duplicate of said original phase component;

impressing electronically on a first spatial light modulator said symmetry testing Fourier filter component;

impressing electronically on a second spatial light modulator said original Fourier phase component of said digitized input image;

producing a beam of coherent light;

directing said beam of coherent light to said first spatial light modulator;

reflecting said beam of coherent light off said first spatial light modulator;

directing said beam of coherent light, after it has reflected off said first spatial light modulator, to said second spatial light modulator;

reflecting scatteringly said beam of coherent light off said second spatial light modulator if there are matches between said original phase component and said symmetry testing phase component;

directing said beam of coherent light, after it has reflected scatterively off said second spatial light modulator, to a lens; and

forming an inverse fast Fourier transform of said beam of coherent light by passing said beam through said lens to a means for viewing said inverse fast Fourier transform;

whereby said means for viewing said inverse fast Fourier transform of said beam of coherent light shows bright intensity patterns relating to objects or object parts having symmetry in said arbitrary scene.

12. An apparatus for cueing in near real-time the presence of an object or object part having symmetry within an arbitrary scene comprising:

means for forming an input image of said arbitrary scene and a duplicate image of said input image preserving spatial orientation of said duplicate image with said input image;

a first means for viewing said input image;

means for performing a Fourier transform on said duplicate image;

means for dividing said Fourier transform of said duplicate image into magnitude and phase components;

means for spatial frequency transforming said magnitude and phase components, in accordance with a particular spatial symmetry test, forming a symmetry testing Fourier filter;

means for correlating said symmetry testing Fourier filter with said magnitude and phase components forming a correlation image; and

a second means for viewing said correlation image;

whereby bright regions in said correlation image represent objects or object parts having symmetry in said input image.

13. An apparatus for cueing in near real-time the presence of an object or object part having symmetry within an arbitrary scene as defined in claim 12 wherein said means for performing a Fourier transform on said duplicate image comprises:

a digital computer Fourier transform array processor.

14. An apparatus for cueing in near real-time the presence of an object or object part having symmetry within an arbitrary scene as defined in claim 12 wherein said means for performing a Fourier transform on said duplicate image comprises:

a lens.

15. An apparatus for cueing in near real-time the presence of an object or object part having symmetry within an arbitrary scene comprising:

means for digitizing an input image of said arbitrary scene and a duplicate image of said input image;

a first means for viewing said input image;

a Fourier transform array processor for performing a Fourier transform on said duplicate image and for dividing said Fourier transform of said duplicate image into magnitude and phase components;

means for spatial frequency transforming said phase component;

a first spatial light modulator for storing said phase component;

a second spatial light modulator for storing said spatial frequency transformed phase component;

a laser for generating a light beam which is directed to said second spatial light modulator causing said light beam to become encoded with said spatial frequency transformed phase component;

means for directing said light beam, after it has been encoded with said spatial frequency transformed phase component, to said first spatial light modulator where said encoded light beam reflectively scatters from said first spatial light modulator;

a lens;

means for directing said light beam, after is has reflectivley scattered from said first spatial light modulator, to said lens for focusing said light beam into a correlation image; and

a second means for viewing said correlation image;

whereby bright regions in said correlation image represent objects or object parts having symmetry in said input image.