Transform optical processing system

• US 5,159,474 A
• Filed: 01/18/1990
• Issued: 10/27/1992
• Est. Priority Date: 10/17/1986
• Status: Expired due to Fees

• Current Assignee: E. I. du Pont de Nemours and Company (Corteva, Inc.)
• Original Assignee: E. I. du Pont de Nemours and Company (Corteva, Inc.)
• Inventors: Mercurio, Gregory S., Franke, Marc A., Casasent, David P., Hekker, Roeland M. T., Livny, Izhak M.
• Primary Examiner(s): Arnold, Bruce Y.
• Assistant Examiner(s): Lerner, Martin
• Application Number:
  US07/465,576
• Time in Patent Office: 1,013 Days
• Field of Search: 350/162.12, 350/162.13, 350/162.14, 350/162.15, 350/3.7, 350/3.72, 350/331 T, 350/351, 382/31, 359/559, 359/560, 359/561, 359/564, 359/15, 359/19, 359/29, 359/86, 250/550, 250/206.2, 250/208.6
• US Class Current: 359/29
• CPC Class Codes: G01B 11/24 for measuring contours or curvatures
• CPC Class Codes: G02B 27/46 Systems using spatial filters
• CPC Class Codes: G06E 3/005 using electro-optical or opto-electronic means

Abstract

The Fourier transform optical processing system of the present invention includes generating an electrical signal in response to a first image and modulating a beam of coherent light with means that is responsive to the electrical signal. A Fourier transform image of the modulated coherent light beam is formed, an then detected. The detector provides a second electrical signal representative of the Fourier transformed image. Other aspects of the invention include comparing the second electrical signal to a reference electrical signal for producing an output signal representing any differences; optically preprocessing the image; detecting the Fourier transform image and generating signals representative of its Fourier transform characteristics; and modulating a coherent light beam using a liquid crystal or other spatial light modulating device.

Claims

1. A Fourier transform optical processing system comprising:

a. means for generating a first electrical signal representing an optical image;

b. means for generating a beam of coherent light and defining an optical path;

c. means disposed in the optical path downstream from said coherent light beam generating means for modulating the coherent light beam solely in response to said first electrical signal representing the optical image;

d. means disposed in the optical path downstream from said modulating means for forming a Fourier transform image of the coherent light beam modulated solely in response to said first electrical signal representing the optical image; and

e. means disposed in the optical path downstream from said Fourier transform image forming means for detecting a predetermined series of angular and radial components of the Fourier transform image of the coherent light beam modulated solely in response to said first electrical signal representing the optical image and for generating a second electrical signal in response to the thus detected series of predetermined angular and radial components of the Fourier transform image.

2. The optical processing system of claim 1 wherein the means for generating a first electrical signal comprises means for generating a composite video signal.

3. The optical processing system of claim 1 wherein the means for modulating the coherent light beam comprises a liquid crystal device.

4. The optical processing system of claim 3 wherein the liquid crystal device includes means for maintaining the liquid crystal device at a predetermined temperature.

5. The optical processing system of claim 4 wherein the means for holding the liquid crystal device at a predetermined temperature further includes means for monitoring the temperature of the liquid crystal device and for providing a feedback signal to the means for holding to maintain the liquid crystal device at the predetermined temperature.

6. The optical processing system of claim 3 wherein the means for modulating the coherent light beam comprises a liquid crystal device, the liquid crystal device comprising a liquid crystal cell disposed between polarizers.

7. The optical processing system of claim 3 wherein the liquid crystal device comprises a liquid crystal cell between polarizers, the polarizers disposed in the optical path and spaced from a liquid crystal cell.

8. The optical processing system of claim 1 wherein the means for modulating the coherent light beam further comprises means for correcting wavefront distortion arising from the means for modulating the coherent light beam.

9. The optical processing system of claim 8 wherein the means for correcting wavefront distortion comprises a hologram, disposed in the optical path of the coherent light beam, having optical properties that are the inverse of any wavefront distortions.

10. The optical processing system of claim 1 wherein the means for modulating the coherent light beam comprises a liquid crystal device including means for generating an entire image on a liquid crystal device.

11. The optical processing system of claim 10 wherein the liquid crystal device comprises a liquid crystal device having an array of individually addressable portions, and the means for generating an entire image on the liquid crystal device comprises means for refreshing selected ones of the individually addressable portions.

12. The optical processing system of claim 1 wherein the means for generating a beam of coherent light comprises means for generating a beam of coherent light having a polarization axis and wherein the means for modulating the coherent light beam comprises means for modulating the coherent light beam having a preferred polarization axis, the polarization axis of the means for generating a beam of coherent light being aligned with the preferred polarization axis of the means for modulating the coherent light beam.

13. The optical processing system of claim 1 wherein the means for generating a beam of coherent light comprises means for polarizing the beam of coherent light for alignment with any polarization axis of the means for modulating the coherent light beam.

14. The optical processing system of claim 1 wherein the means for modulating the coherent light beam comprises a magneto-optic device.

15. The optical processing system of claim 1 wherein the means for modulating the coherent light beam comprises means for generating an image that corresponds to the first image.

16. The optical processing system of claim 1 wherein the means for modulating the coherent light beam comprises a transmissive liquid crystal device.

17. The optical processing system of claim 1 wherein the means for modulating the coherent light beam comprises a reflective liquid crystal device.

18. The optical processing system of claim 1 wherein the means for forming a transform image comprises a holographic optical element that approximates a quadratic wave function for forming a Fourier transform image.

19. The optical processing system of claim 1 wherein the means for forming a transform comprises a holographic optical element comprising the complex conjugate of the phase variation of any elements disposed along the optical path to correct wavefront distortion multiplied by an approximate quadratic phase function, so that wavefront distortion is corrected and a Fourier transform of the image is formed.

20. The optical processing system of claim 1 wherein the means for detecting the transform image comprises means for sampling a Fourier transform image in a plurality of wedge and ring shaped domains.

21. The optical processing system of claim 1 wherein the means for detecting the Fourier transform image comprises a detector having a portion comprising a plurality of ring shaped domains concentrically disposed from the center of the Fourier transform image for detecting radial components of a Fourier transform image.

22. The optical processing system of claim 1 wherein the means for detecting the Fourier transform image comprises a detector having a portion comprising a plurality of wedge shaped domains radially disposed with their points in the center of the Fourier transform for detecting angular components of a Fourier transform image.

23. The optical processing system of claim 1 wherein the means for detecting the transform image and generating a second electrical signal comprises a device that generates an electrical signal in response to an incident light beam.

24. The optical processing system of claim 1 wherein the means for detecting the transform image and generating a second electrical signal comprises a camera that generates an electrical signal in response to an incident light beam.

25. The optical processing system of claim 1 wherein the means for detecting the transform image and generating a second electrical signal comprises a mask means disposed in the optical path for blocking or transmitting selected portions of the coherent light beam and means disposed in the optical path downstream from the mask means for generating the second electrical signal in response to the incident masked light beam.

26. The optical processing system of claim 25 wherein the mask means comprises a fixed mask.

27. The optical processing system of claim 25 wherein the mask means comprises a variable mask.

28. The optical processing system of claim 25 wherein the mask means comprises a liquid crystal device comprising an array of individually addressable portions.

29. The optical processing system of claim 25 wherein the mask comprises means for selectively disposing in the optical path a succession of masks having predetermined wedge and ring shapes.

30. The optical processing system of claim 25 wherein the mask comprises a rotatable disk having a plurality of predetermined wedge and ring shapes disposed at a predetermined radius for successive disposition into the optical path.

31. The optical processing system of claim 1 wherein the means for detecting the Fourier transform image and generating a second electrical signal comprises a mask means for sequentially disposing a series of predetermined wedge and ring shaped transparent mask segments in the optical path for isolating the angular and radial components of the Fourier transform image and transmitting said isolated Fourier transform image components one at a time for a predetermined period of time, and means disposed in the optical path down stream from the mask means for receiving each transmitted Fourier transform image component of the coherent light beam and for generating an electrical signal in response thereto.

32. The optical processing system of claim 1 wherein said means disposed in the optical path comprises means for:

generating a second, unique electrical signal that uniquely identifies the first image independent of signals generated in response to detection of the first image.

33. A method of optically processing using a Fourier transform, the method comprising:

a. generating a first electrical signal representing an optical image;

b. generating a beam of coherent light and defining an optical path;

c. modulating the coherent light beam solely in response to said first electrical signal representing the optical image;

d. forming a Fourier transform image of the coherent light beam modulated solely in response to said first electrical signal representing the optical image; and

e. detecting a predetermined series of angular and radial components of the Fourier transform image of the coherent light beam modulated solely in response to said first electrical signal representing the optical image and generating a second electrical signal in response to the thus detected series of predetermined angular and radial components of the Fourier transform image.

34. The method of claim 33 wherein the step of generating a first electrical signal comprises generating a composite video signal.

35. The method of claim 33 wherein the step of modulating the coherent light beam comprises modulating the coherent light beam by transmitting it through a liquid crystal device responsive to the electrical signal representing the first optical image.

36. The method of claim 33 wherein the step of modulating the coherent light beam comprises modulating the coherent light beam by reflecting it from a liquid crystal device responsive to the electrical signal representing the first optical image.

37. The method of claim 33 further comprising the step of correcting any wavefront distortion arising from the means for modulating the coherent light beam.

38. The method of claim 37 wherein the step of correcting wavefront distortion comprises disposing, in the optical path of the coherent light beam, a hologram having optical properties that are the inverse of any wavefront distortions.

39. The method of claim 33 wherein the step of modulating the coherent light beam comprises generating an entire image on a liquid device disposed in the optical path.

40. The method of claim 39 wherein the step of generating an entire image on the liquid crystal device comprises refreshing selected ones of the individually addressable pixel portions of the liquid crystal device.

41. The method of claim 33 wherein the step of detecting the transform image comprises using a series of wedge and ring shaped domains to sample a Fourier transform image.

42. The method of claim 33 wherein the step of detecting the transform and generating a second electrical signal comprises detecting a Fourier transform and digitizing at least a portion of the Fourier transform image.

43. The method of claim 33 wherein the step of detecting the transform image and generating a second electrical signal comprises selectively masking portions of the coherent light beam and generating the second electrical signal in response to the incident masked light beam.

44. The method of claim 43 wherein the step of selectively masking comprises varying the mask with respect to time.