Optical image analyzer using optical correlation and opto-electronic feedback

• US 5,323,472 A
• Filed: 02/11/1993
• Issued: 06/21/1994
• Est. Priority Date: 03/27/1990
• Status: Expired due to Term

• Current Assignee: Regents of the University of California (University of California), University of California San Diego (University of California)
• Original Assignee: The Boeing Co.
• Inventors: Falk, R. Aaron
• Primary Examiner(s): Boudreau, Leo H.
• Assistant Examiner(s): Prikockis, Larry J.
• Application Number:
  US08/017,408
• Time in Patent Office: 495 Days
• Field of Search: 382/31, 382/42, 382/43, 382/46, 359/11, 359/29, 359/561, 359/239, 364/822
• US Class Current: 382/103
• CPC Class Codes: G06E 3/005 using electro-optical or opto-electronic means
• 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 apparatus and method for image analysis utilizing an optical-electronic hybrid device. A light source generates light through an alternating series of lenses and electronically addressable spatial light modulators to an optical correlation plane. A first modulator introduces an input image and a second modulator introduces a Fourier transformed reference image into the device. The device correlates the input image and the reference image in the optical correlation plane. The optical correlation plane feeds back information through a processor to the second modulator which varies a parameter of the reference image. The second modulator varies parameters to determine the greatest correlation between the input image and the reference image. The parameters at the point of greatest correlation are used together with the reference image to identify the input image.

Claims

1. An optical image analysis device, comprising:

a first lens for projecting a spatially coherent light beam onto an image plane;

a first spatial light modulator for introducing an input image onto said image plane through which said light beam passes, said input image corresponding to an object in question;

a second lens positioned downstream from said image plane by its focal length so as to receive said light beam after said light beam passes through said first spatial light modulator, said second lens producing a Fourier transformed input image at a Fourier plane positioned downstream from said second lens by a distance of the second lens focal length;

a second spatial light modulator positioned at said Fourier plane;

driving means coupled to said second spatial light modulator to produce a Fourier transformed reference image using a predetermined reference image and predetermined filter parameters, said predetermined filter parameters corresponding to parameters of said predetermined reference image;

a third lens positioned downstream of said Fourier plane by a focal length of said third lens, said third lens correlating said Fourier transformed input image and said Fourier transformed reference image by producing a correlation image at a focal plane of said third lens;

imaging means for detecting a magnitude of correlation of said correlation image;

feedback means, coupled to said imaging means and said driving means for varying said Fourier transformed reference image in a Fourier domain by varying parameter values of said predetermined filter parameters until said magnitude of correlation is maximized to identify best fit parameter values; and

identifying means for identifying said object in question according to said predetermined reference image and said best fit parameter values.

2. An optical image analysis device as recited in claim 1, wherein said first, second and third lenses are comprised of graded-index-of-refraction lenses.

3. An optical image analysis device as recited in claim 1, wherein said feed back means includes a processor which utilizes a template matching algorithm so as to vary said parameter values of said Fourier transformed reference image.

4. A method of analyzing optical images comprising the steps of:

a) projecting a spatially coherent light beam onto an image plane using a first lens;

b) introducing via a first spatial light modulator an input image onto said image plane through which said light beam passes, and input image corresponding to an object in question;

c) positioning a second lens downstream from said image plane by its focal length so as to receive said light beam after said light beam passes through said first spatial light modulator;

d) producing a Fourier transformed input image at a Fourier plane positioned downstream from said second lens by a distance of a focal length of said second lens;

e) producing a Fourier transformed reference image on a second spatial light modulator at said Fourier plane using a predetermined reference image and predetermined filter parameters, said predetermined filter parameters corresponding to parameters of said stored reference image;

f) producing, via a third lens, a correlation image representing a correlation of said Fourier transformed reference image and said Fourier transformed input image at a correlation plane located downstream of said Fourier plane by a focal length of said third lens;

g) varying said Fourier transformed reference image in a Fourier domain by varying values of said predetermine filter parameters to determine particular parameter values producing a maximum correlation; and

comparing said particular parameter values with known parameter values associated with said predetermined reference image and identifying said object in question on a basis of said comparison.

5. The method of claim 4, wherein said varying step comprises the step of utilizing a template matching algorithm so as to vary said predetermined filter parameters.

6. A method of analyzing optical images, as claimed in claim 4, varying step includes the step of stopping said varying of said values of said predetermined filter parameters when said correlation image corresponds to a point at which a correlation curve has a slope of zero.

7. An optical image analysis device, comprising:

means for generating light through an optical path and onto an image plane;

first modulator means for introducing an input image into said image plane of said optical path, said input image corresponding to an object being analyzed;

second modulator means for introducing a filter image onto said optical path at a Fourier plane and for receiving said input image at said Fourier plane, said filter image being generated from a predetermined reference image and values of a plurality of predetermined filter parameters, said predetermined filter parameters corresponding to parameters of said predetermined reference image;

correlation means for correlating said input image and said filter image at an optical correlation plane and for outputting a correlation signal;

feedback means coupled to said correlation means and said second modulator means for varying said filter image in a Fourier domain by varying said values of said plurality of predetermined filter parameters until said correlation signal is optimized in order to identify best fit parameter values; and

identifying means for identifying said input image on a basis of said predetermined reference image and said best fit parameter values.

8. An optical image analysis device as recited in claim 7, wherein said feedback means comprises a processor which utilizes a template matching algorithm so as to vary said values of said plurality of predetermined filter parameters.

9. A method of analyzing optical images comprising the steps of:

a) introducing a Fourier transformed input image of an input image corresponding to an object to be identified at a Fourier plane of an optical path;

b) introducing, via a spatial light modulator, a Fourier transformed filter image at said Fourier plane representative of a predetermined reference image;

c) producing a correlation image representative of a correlation between said Fourier transformed input image and said Fourier transformed filter image;

d) directly varying said Fourier transformed filter image in a Fourier domain by varying values of predetermined filter parameters of driving signals supplied to said spatial light modulator so as to successively introduce new filter images in said Fourier domain until said correlation between said Fourier transformed input image and said filter images, represented by a particular Fourier transformed filter image, is maximized, said filter parameters corresponding to parameters of said predetermined reference image;

e) determining particular values of said predetermined filter parameters when said correlation is maximized in step d);

f) identifying said object on a basis of said predetermined reference image and said particular values of said predetermined filter parameters.