Method and apparatus for camouflage signature measurement

• US 4,223,345 A
• Filed: 06/20/1979
• Issued: 09/16/1980
• Est. Priority Date: 06/20/1979
• Status: Expired due to Term

• 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: Hannigan, Joseph F.
• Primary Examiner(s): Britton, Howard W.
• Application Number:
  US06/050,391
• Time in Patent Office: 454 Days
• Field of Search: 358/93, 358/106, 358/107, 358/108, 358/903, 364/515
• US Class Current: 382/191
• CPC Class Codes: G01S 7/412 based on a comparison between measured values and known or stored values
• CPC Class Codes: G01S 7/539 using analysis of echo signal for target characterisation; Target signature; Target cross-section

Abstract

A method and apparatus for measuring the extent of camouflage applied to aarget is disclosed. The apparatus includes a direct electronic Fourier transform device responsive to first and second conditions of camouflage of a target for producing spectra signals of first and second limited Fourier transforms, respectively. Each of the spectra signals has a plurality of amplitude and principal frequency components, and a base clipper circuit is provided for deleting the spectra signal amplitude components below a given value. A radio frequency voltmeter and a first analog-to-digital converter cooperate to produce digital signals corresponding with the magnitude of the amplitude components. Similarly, a radio frequency frequency meter and a second analog-to-digital converter cooperate to produce digital signals corresponding with the principal frequency components. A control device controls the operating sequence of the digital signal producing devices for subsequent spectra signals and a memory stores the first and second digital amplitude and principle frequency signals. The first and second amplitude signals are compared in a comparator, thereby to indicate the difference between the extent of camouflage of the target in the first and second conditions.

Claims

1. Apparatus for measuring the extent of camouflage applied to a target, comprising

(a) means responsive to first and second conditions of camouflage of a target for producing spectra signals of first and second limited Fourier transforms, respectively, each of said spectra signals having a plurality of amplitude and principal frequency components;

(b) base clipper circuit means for deleting from said spectra signals those amplitude components having amplitudes less than a given value;

(c) means connected with said clipper circuit means for producing amplitude and principal frequency digital signals corresponding with the clipped amplitude and principal frequency components of said first and second spectra signals, respectively; and

(d) comparison means connected with said digital signal producing means for comparing said first and second amplitude signals at each of said principal frequencies, thereby to indicate the difference between the extent of camouflage of the target in said first and second conditions.

2. Apparatus as defined in claim 1, wherein said digital signal producing means includes

(1) means including radio-frequency voltmeter means and first analog-to-digital converter means for converting the clipped amplitude signals to digital amplitude signals;

and

(2) means including radio-frequency frequency meter means and second analog-to-digital converter means for converting said principal frequency components to digital frequency signals.

3. Apparatus as defined in claim 2, wherein said comparison means includes calculator means having an arithmetic logic unit for calculating the extent of camouflage.

4. Apparatus as defined in claim 3, wherein said digital signal producing means further includes

(3) first memory means (14) for storing said spectra signals;

(4) gate means (16) for controlling the output of said second storage means to deliver successive ones of said spectra signals to said radio frequency voltmeter and said radio frequency frequency meter, respectively; and

(5) control means (22) for activating said gate means following digital amplitude and frequency processing of a previous one of said spectra signals to deliver a subsequent one of said spectra signals for digital amplitude and frequency processing.

5. Apparatus as defined in claim 4, wherein said digital signal producing means further includes

(6) second memory means (28) connected with said control means for storing said first and second digital amplitude and principal frequency signals, the output of said second memory means being connected with said comparison means.

6. Apparatus as defined in claim 5, wherein said spectra signal producing means comprises

(1) direct electronic Fourier transform generating means operable to scan the target;

(2) sweep oscillator means for providing a range of limited scanning frequencies to said direct electronic Fourier transform means; and

(3) synchronous detector means for detecting said spectra signals from said direct electronic Fourier transform means, thereby to produce a limited spectra output of the target.

7. Apparatus as defined in claim 2, and further comprising display means connected with said comparison means for visually displaying the extent of camouflage applied to a target.

8. A method for measuring the extent of camouflage applied to a target, comprising the steps of

(a) producing first and second spectra signals of Fourier transforms from first and second conditions of camouflage of a target, respectively, each of said spectra signals having a plurality of amplitude and principal frequency components;

(b) deleting said spectra signal amplitude components less than a given value;

(c) producing amplitude and principal frequency digital signals corresponding with the amplitude and principal frequency components of said first and second spectra signals, respectively;

(d) storing said first and second digital amplitude and principal frequency signals; and

(e) comparing said first and second amplitude signals at each of said principal frequencies, thereby to indicate the difference between the extent of camouflage of the target in said first and second conditions.