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US5214534A
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Coding intensity images as phase-only images for use in an optical correlator
Assignee: UNITED STATES OF AEMRICA AIR FORCE, Secretary of
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Filing: 1991-06-19
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Granted: 1993-05-25
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Expires: 2011-06-19
Abstract
Abstract A method of performing image correlation in a Fourier transform correlator utilizes phase-encoding of the input image as a phase object with a normalized amplitude component. Phase-only reference image filters are used in conjunction with the phase-encoded input objects to improve the signal to clutter ratio. This technique can employ optical or digital implementation.
Inventors
- 👤 Robert R. Kallman
- 👤 Dennis H. Goldstein
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-05 04:08
CPC Classifications
G; G06; G06E; G06E3/00; G06E3/001; G06E3/005
Claims Analysis
Total Claims: 16
Claim 1
Independent Claim
91 words
A method of improving the signal-to-clutter ratio in a Fourier transform correlator comprising the steps of: (a) inputting an input image signal into said Fourier transform correlator; (b) phase-encoding said input image signal into a first phase-only encoded signal; (c) providing a second phase-only encoded reference filter image signal; (d) producing the Fourier transform of the first phase-only encoded signal; and (e) inverse Fourier transforming the product of the Fourier transform of the first phase-only encoded signal and the second phase-only encoded reference filter image signal to obtain a correlation signal.
Claim 2
Independent Claim
91 words
A method of improving the signal-to-clutter ratio in a Fourier transform correlator comprising the steps of: (a) inputting an input image signal into said Fourier transform correlator; (b) phase-encoding said input image signal into a first phase-only encoded signal; (c) providing a second phase-only encoded reference filter image signal; (d) producing the Fourier transform of the first phase-only encoded signal; and (e) inverse Fourier transforming the product of the Fourier transform of the first phase-only encoded signal and the second phase-only encoded reference filter image signal to obtain a correlation signal.
Claim 3
Independent Claim
101 words
A method of improving the signal-to-clutter ratio in a Fourier transform correlator comprising the steps of: (a) inputting an input image signal into said correlator; (b) producing a first amplitude-normalized phase-encoded signal which is a function of said input image signal; (c) providing a second amplitude-normalized phase-encoded reference filter image signal which is a function of a reference image signal; (d) producing the Fourier transform of the first phase-encoded signal; and (e) inverse Fourier transforming the product of the Fourier transform of the first amplitude-normalized phase-encoded signal and the second amplitude-normalized phase-encoded reference filter image signal to obtain a correlation signal.
Claim 4
Independent Claim
101 words
A method of improving the signal-to-clutter ratio in a Fourier transform correlator comprising the steps of: (a) inputting an input image signal into said correlator; (b) producing a first amplitude-normalized phase-encoded signal which is a function of said input image signal; (c) providing a second amplitude-normalized phase-encoded reference filter image signal which is a function of a reference image signal; (d) producing the Fourier transform of the first phase-encoded signal; and (e) inverse Fourier transforming the product of the Fourier transform of the first amplitude-normalized phase-encoded signal and the second amplitude-normalized phase-encoded reference filter image signal to obtain a correlation signal.
Claim 5
Dependent Claim
48 words
The method of claim 2 wherein the phase-encoding of step (b) is such that the intensity I of each pixel of said input image signal is divided by M and then multiplied by π, where M is an integer such that Iπ/M ranges between 0 and π radians.
Claim 6
Dependent Claim
9 words
The method of claim 3 where M equals 255.
Claim 7
Independent Claim
110 words
A method of improving the signal-to-clutter ratio in a Fourier transform correlator comprising the steps of: (a) inputting an input image signal into said Fourier transform correlator; (b) producing a first amplitude-normalized phase-only encoded signal which is a function of the intensity of said input image signal; (c) providing a second amplitude-normalized phase-only encoded reference filter image signal which is a function of a reference image signal; (d) producing the Fourier transform of the first phase-only encoded signal; and (e) inverse Fourier transforming the product of the Fourier transform of the first amplitude-normalized phase-only encoded signal and the second phase-only encoded reference filter image signal to obtain a correlation signal.
Claim 8
Independent Claim
110 words
A method of improving the signal-to-clutter ratio in a Fourier transform correlator comprising the steps of: (a) inputting an input image signal into said Fourier transform correlator; (b) producing a first amplitude-normalized phase-only encoded signal which is a function of the intensity of said input image signal; (c) providing a second amplitude-normalized phase-only encoded reference filter image signal which is a function of a reference image signal; (d) producing the Fourier transform of the first phase-only encoded signal; and (e) inverse Fourier transforming the product of the Fourier transform of the first amplitude-normalized phase-only encoded signal and the second phase-only encoded reference filter image signal to obtain a correlation signal.
Claim 9
Dependent Claim
46 words
The method of claim 5 wherein the intensity I of each pixel of said input image signal is divided by M and then multiplied by π during the performance of step (b), where M is an integer such that Iπ/M ranges between 0 and π radians.
Claim 10
Independent Claim
152 words
A method of improving the signal-to-clutter ratio in a Fourier transform correlator comprising the steps of: (a) providing a first and second phase-modulating spatial light modulator; (b) inputting an input image signal into said correlator; (c) producing a first phase-only encoded signal which is proportional to the intensity of the input image signal; (d) applying said first phase-only encoded signal to said first phase-modulating spatial light modulator; (e) applying a second phase-only encoded reference filter image signal to said second phase-modulating spatial light modulator; (f) producing the Fourier transform of the first phase-only encoded signal in said first phase-modulating spatial light modulator at the second phase-modulating spatial light modulator; and (g) inverse Fourier transforming the product of the Fourier transform of the first phase-only encoded signal in said first spatial light modulator and the second phase-only encoded reference filter image signal in said second spatial light modulator to obtain a correlation signal.
Claim 11
Independent Claim
152 words
A method of improving the signal-to-clutter ratio in a Fourier transform correlator comprising the steps of: (a) providing a first and second phase-modulating spatial light modulator; (b) inputting an input image signal into said correlator; (c) producing a first phase-only encoded signal which is proportional to the intensity of the input image signal; (d) applying said first phase-only encoded signal to said first phase-modulating spatial light modulator; (e) applying a second phase-only encoded reference filter image signal to said second phase-modulating spatial light modulator; (f) producing the Fourier transform of the first phase-only encoded signal in said first phase-modulating spatial light modulator at the second phase-modulating spatial light modulator; and (g) inverse Fourier transforming the product of the Fourier transform of the first phase-only encoded signal in said first spatial light modulator and the second phase-only encoded reference filter image signal in said second spatial light modulator to obtain a correlation signal.
Claim 12
Dependent Claim
46 words
The method of claim 7 wherein the intensity I of each pixel of said input image signal is divided by M and then multiplied by π during the performance of step (c), where M is an integer such that Iπ/M ranges between 0 and π radians.
Claim 13
Dependent Claim
9 words
The method of claim 8 where M equals 255.
Claim 14
Independent Claim
137 words
A method of improving the signal-to-clutter ratio in a Fourier transform correlator comprising the steps of: (a) providing a first and second phase-modulating spatial light modulator; (b) inputting a phase-only encoded input image signal into said first phase-modulating spatial light modulator; (c) reading out a phase-only encoded optical signal from said first phase-modulating spatial light modulator; (d) inserting a phase-only encoded reference filter image signal into said second phase-modulating spatial light modulator; (e) producing the Fourier transform of the first phase-only encoded optical signal produced by the first phase-modulating spatial light modulator at the second phase-modulating spatial light modulator; and (f) inverse Fourier transforming the product of the fourier transform of the first phase-only encoded optical signal and the phase-only encoded reference filter image signal in the second phase-modulating spatial light modulator to obtain a correlation signal.
Claim 15
Independent Claim
137 words
A method of improving the signal-to-clutter ratio in a Fourier transform correlator comprising the steps of: (a) providing a first and second phase-modulating spatial light modulator; (b) inputting a phase-only encoded input image signal into said first phase-modulating spatial light modulator; (c) reading out a phase-only encoded optical signal from said first phase-modulating spatial light modulator; (d) inserting a phase-only encoded reference filter image signal into said second phase-modulating spatial light modulator; (e) producing the Fourier transform of the first phase-only encoded optical signal produced by the first phase-modulating spatial light modulator at the second phase-modulating spatial light modulator; and (f) inverse Fourier transforming the product of the fourier transform of the first phase-only encoded optical signal and the phase-only encoded reference filter image signal in the second phase-modulating spatial light modulator to obtain a correlation signal.
Claim 16
Dependent Claim
27 words
The method of claim 10 wherein step (c) includes illuminating said first phase-modulating spatial light modulator with collimated coherent light to produce said phase-only encoded optical signal.
References Cited (Backward Citations)
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