Reflective optical correlator with a folded asymmetrical optical axis

• US 5,311,359 A
• Filed: 12/24/1992
• Issued: 05/10/1994
• Est. Priority Date: 12/24/1992
• Status: Expired due to Term

• Current Assignee: Northrop Grumman Systems Corporation (Northrop Grumman Corporation)
• Original Assignee: Litton Systems Incorporated
• Inventors: Pollack, Andrew M., Mills, Stuart A., Lucas, John R.
• Primary Examiner(s): Arnold, Bruce Y.
• Assistant Examiner(s): ROBBINS, THOMAS
• Application Number:
  US07/996,584
• Time in Patent Office: 502 Days
• Field of Search: 359/561, 359/559, 382/42, 382/31
• US Class Current: 359/561
• CPC Class Codes: G02B 27/46 Systems using spatial filters
• CPC Class Codes: G06E 3/003 forming integrals of products, e.g. Fourier integrals, Laplace integrals, correlation integrals; for analysis or synthesis of functions using orthogonal functions
• CPC Class Codes: G06V 10/89 using frequency domain filters, e.g. Fourier masks implemented on spatial light modulators

Abstract

An optical correlator system having a plurality of reflective optical components, both active and passive, positioned (1) between a source of electromagnetic radiation, such as a visible beam of coherent light, and an output detector array, and (2) around an asymmetrical perimeter of a planar support body to develop an asymmetrically folded optical axis or path wholly within the body where the path is traversed by the beam SO THAT information processed by the active optical components along the optical path and imparted to the optical beam enable the optical detection of an unknown object at the detector array which is then subject to an identification process.

Claims

1. An optical correlator system for the detection and identification of an unknown object where the object is represented at an input station of the system, imaged at a subsequent filter station in a Fourier transform plane, then detected and identified at a subsequent detector station CHARACTERIZED IN THAT the optical correlator system comprises:

a) system support means having an asymmetrical perimeter region that defines a number (n) of system stations non-uniformally spaced apart along said asymmetrical perimeter,

b) respective ones of a plurality of reflective optical component means positioned at selected and associated ones of a number (n-2) of said system stations, and a plurality of transmissive optical component means positioned between selected ones of said (n) system stations, all to affect a beam of electromagnetic radiation impinging thereon and passing therethrough respectively,

c) said reflective optical component means include an input means positioned at the input station of the system and a filter means positioned at the filter station of the system where said input means is responsive to an input signal representing an unknown object, and said filter means is responsive to the Fourier transform output of said input means, and both said input means and said filter means impart selected information to said beam of electromagnetic radiation,

d) electromagnetic radiation source means positioned at a first or alpha one of said non-selected system stations generating said beam of electromagnetic radiation, and

e) electromagnetic radiation detector means positioned at a last or omega remaining one of said non-selected system stations and being responsive to said resulting beam of electromagnetic radiation subsequent to all of said reflective and transmissive optical component means effect on said beam of electromagnetic radiation,

f) said source means, reflective optical component means, and said detector means define the boundaries of a folded optical path developed wholly within said support means and traversed by said beam of electromagnetic radiation SO THAT the unknown object is optically detected and identified.

2. The optical correlator system of claim 1 in which said input means and said filter means are active components.

3. The optical correlator system of claim 2 in which said input means is an input spatial light modulator (SLM) and said filter means is a filter SLM.

4. The optical correlator system of claim 1 in which said detector means is a charge coupled device having a detector face.

5. The optical correlator system of claim 1 in which said support means is a solid body having at least one tunnel bored between sequentially adjacent ones of said stations.

6. The optical correlator system of claim 5 in which said optical path is coextensive with each port between and interconnecting said sequentially adjacent ones of said stations SO THAT said optical path thereby developed is folded and generally zigzag in geometric configuration.

7. The optical correlator of claim 6 in which said optical path includes a plurality of linear path segments sequentially aligned in said folded zigzag optical path wherein selected ones of said linear path segments have a finite length greater than nonselected ones of said linar path segments SO THAT said folded optical path is asymmetrical.

8. An optical correlator system for the detection of an unknown object where the object is represented at an input station of the system, imaged at a subsequent filter station in a Fourier transform plane, then detected and subject to identification at a terminus detector station CHARACTERIZED IN THAT the optical correlator system comprises:

a) system support means having an asymmetrical perimeter region that defines a number (n) of system stations which are non-uniformally spaced apart along said perimeter,

b) a coherent light source positioned at an initial one of said stations,

c) a second station in linear opposition to and spaced apart from said light source,

d) a first light path segment formed in said system support means between said light source and said second station,

e) a reflective input spatial light modulator positioned at said second station,

f) a first toric reflective surface positioned at a third station in linear opposition to and spaced apart form said input spatial light modulator,

g) a second light path segment formed in said system support means between said input spatial light modulator and said first toric reflective surface,

h) a fourth station in linear opposition to and spaced apart from said a toric reflective surface,

i) a reflective filter spatial light modulator positioned at said fourth station,

j) a third light path segment formed in said support means between said toric reflective surface and said filter spatial light modulator,

k) a second toric reflective surface positioned at a fifth station in linear opposition to and spaced apart from said filter spatial light modulator,

l) a fourth light path segment formed in said support means between said filter spatial light modulator and said second toric reflective surface,

m) a charge coupled detector positioned at a sixth station in linear opposition to and spaced apart from said second toric reflective surface,

n) a fifth light path segment formed in said system support means between said second toric reflective surface and said detector,

o) said first through said fifth light path segments forming a folded asymmetrical optical axis or path which is zigzag in configuration and wholly contained within said system support means where each of said first and fifth light path segments are in linear dimension less than at least one of said second through fourth light path segments,

p) a first polarizer positioned between said coherent light source and said reflective input spatial light modulator to intercept and selectively rotate said first light path segment in the transmissive mode,

q) a second polarizer positioned adjacent said first toric reflective surface to intercept and selectively rotate both of said second and third light path segments in the transmissive mode, and

r) a third polarizer positioned between said second toric reflective surface and said detector to intercept and selectively rotate said fifth light path segment in the transmissive mode SO THAT the unknown object is optically detected and thereby subject to a process for identification.

9. The optical correlator system of claim 8 in which said second station is the input plane and said fourth station is the filter plane for the identification of at least one unknown input through optical correlation of the input plane with a plurality of known filters at the filter plane in a Fourier transform.

10. The optical correlator system of claim 8 in which said second polarizer is positioned at said third station between said first toric reflective surface and each of said input spatial light modulator and said filter spatial light modulator to intercept said second and third light path segments both in the transmissive mode.