OBJECT IDENTIFICATION BY EMISSION POLARIZATION

• US 3,748,484 A
• Filed: 06/07/1971
• Issued: 07/24/1973
• Est. Priority Date: 12/31/1969
• Status: Expired due to Term

• Current Assignee: Dennis O. Covault
• Original Assignee: Dennis O. Covault
• Inventors: Covault, Dennis O.
• Primary Examiner(s): Lawrence, James W.
• Assistant Examiner(s): Nelms, D. C.
• Application Number:
  US05/150,739
• Time in Patent Office: 778 Days
• Field of Search: 250/225 350/147 356/114,115,116,117,118,119
• US Class Current: 250/225
• CPC Class Codes: G01N 21/21 Polarisation-affecting properties G01N21/19 takes precedence
• CPC Class Codes: G01S 7/499 using polarisation effects

Abstract

Metallic objects are identifiable by the degree of polarization of infrared radiation emitted therefrom. To identify a metallic object from a nonmetallic object by radiation emitted therefrom, three linearly polarized detectors are positioned to be responsive to the emitted radiation. Each of these three detectors is responsive to radiation from the object along a different plane of polarization. Output signals from the three detectors are processed in a system to produce a signal equal to the square of the degree of polarization. Smooth objects are distinguishable from rough objects in the same field of view by determining the degree of polarization of a light beam directed to and reflected from the objects. By knowing the polarization axis of the light waves at the source, the output signals of two detectors may be combined to highlight in a display smooth objects in a field of view that contains both smooth and rough objects.

Claims

1. The method of identifying an object by determining the degree of polarization of energy reflected therefrom, comprising the steps of:

illuminating the object with radiant energy polarized along a known axis, measuring the radiation reflected from said object by polarized detectors orientated at different angles with respect to the known polarized axis, summing the reflected energy measurements as resulting from each of said detectors to obtain a total intensity measurement, generating a signal representing the difference between the total intensity measurements in excess of a threshold value, and summing the total intensity measurement and the signal representing the difference between the intensity measurements above the threshold to produce a display signal that identifies an object by the degree of polarization of the energy reflected therefrom.

2. The method of identifying an object by determining the degree of polarization of energy reflected therefrom as set forth in claim 1 including the step of scanning a field of view with the polarixed energy illuminating the object to generate background display signals used in the identification of an object.

3. The method of identifying an object by determining the degree of polarization of energy reflected therefrom as set forth in claim 1 including the step of splitting the energy reflected from the object to be identified into a beam for each detector measuring the reflected energy.

4. The method of identifying an object by determining the degree of polarization of energy reflected therefrom as set forth in claim 1 including the step of inputting said display signal that identifies an object to a cathode ray tube.

5. Apparatus for identifying an object by determining the degre of polarization of energy reflected therefrom, comprising:

means for illuminating a target with energy polarized along a known axis, means for scanning a field of view including the object to be identified with the energy polarized along the known axis, means for measuring the polarized reflected radiation from the scanned area by at least two detectors orientated at different angles with respect to the known axis of the polarized energy, means for summing the reflected energy measurements resulting from each of the detectors to obtain a total intensity measurement, means for generating a signal representing the difference between the intensity measurements from each of the several detectors in excess of a threshold, and means for adding the total intensity measurement signal and the signal in excess of the threshold to produce a display signal for identifying an object in the scanned field of view.

6. Appraratus for identifying an object by the degree of polarization of energy reflected therefrom as set forth in claim 5 wherein said illuminating means in a source of monochromatic polarized light.

7. Apparatus for identifying an object by the degrEe of polarization of energy reflected therefrom as set forth in claim 6 wherein said source is modymium laser.

8. Apparatus for identifying an object by the degree of polarization of energy reflected therefrom as set forth in claim 5 including means for splitting the reflected radiation into a beam for each detector.

9. Apparatus for identifying an object by the degree of polarization of energy reflected therefrom as set forth in claim 5 wherein said detectors are silicon photo diodes.

10. Apparatus for identifying an object by the degree of polarization of energy reflected therefrom as set forth in claim 5 including display means responsive to said display signals and including a cathode ray tube for displaying the area viewed.