Coherent optical feature identifier apparatus

• US 4,387,989 A
• Filed: 07/23/1980
• Issued: 06/14/1983
• Est. Priority Date: 07/23/1980
• Status: Expired due to Term

• Current Assignee: United States Of America As Represented By The Secretary Of The Air Force
• Original Assignee: United States Of America As Represented By The Secretary Of The Air Force
• Inventors: Pirich, Andrew R.
• Primary Examiner(s): McGraw, Vincent P.
• Application Number:
  US06/171,614
• Time in Patent Office: 1,056 Days
• Field of Search: 356/71, 350/162 SF, 350/162.12, 350/162.13
• US Class Current: 356/71
• CPC Class Codes: G06F 18/00 Pattern recognition
• CPC Class Codes: G06V 10/36 Applying a local operator, i.e. means to operate on image points situated in the vicinity of a given point; Non-linear local filtering operations, e.g. median filtering
• 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

A coherent optical feature identifier apparatus utilizing an optical data gathering system in conjunction with a digital data correlator unit to recognize uninterpretable features on photographs. A dual visual display is utilized to compare a desired feature with the Fourier transform correlation from the comparator storage unit.

Claims

1. An optical correlator for identifying features on a photographic film comprising in combination:

means for generating a source of coherent light, said coherent light being non-divergent,

means for focusing said coherent light through said photographic film, said photographic film including an index of refraction matching means attached to said photographic film,

a spatial filter disk in alignment with and interacting with said focusing means, said spatial filter disk comprises a glass disk with a plurality of wedge sections inscribed thereon, each wedge section of said plurality of wedge sections being divided into a plurality of linearly decreasing sub-regions, each sub-region having a discrete emulsion deposition that is characteristic of a particular feature,

a Fourier Transform lens between said means for focusing coherent light and said spatial filter disk, said spatial filter disk having a Fourier Transform power spectra emulsion deposited thereon, said spatial filter disk providing an optical correlation signal in response to the coincidence of a photographic film feature and a corresponding filter disk Fourier Transform power spectra feature, and,

means for detecting said optical correlation signal positioned in alignment with said spatial filter disk, said detecting means providing an analog signal in response to said optical correlation signal.

2. Apparatus as described in claim 1 wherein said index of refraction matching means is a liquid gate which comprises a first and second glass plate members with an index matching oil sandwiched therebetween, the index of refraction of the combination being varied as the distance between the first and second glass plate members vary.

3. Apparatus as described in claim 1 wherein said emulsion deposition is a photographic film emulsion that is deposited on said glass disk.

4. Apparatus as described in claim 2 wherein said index matching oil is a light mineral oil.

5. Apparatus as described in claim 2 wherein said emulsion deposition is a photographic film emulsion that is deposited on said glass disk.

6. Apparatus as described in claim 5 further including means for rotating one of a plurality of said spatial filter disk into alignment with said focusing means, to achieve a peak correlation signal of the Fourier Transform power spectra.

7. Apparatus as described in claim 5 wherein said generating means comprises an Argon laser.

8. Apparatus as described in claim 5 wherein said detecting means comprises a charge-coupled device camera.