Addressable optical computer and filter

• US 4,187,000 A
• Filed: 12/15/1977
• Issued: 02/05/1980
• Est. Priority Date: 06/16/1975
• Status: Expired due to Term

• Current Assignee: Advanced Micro Devices, Inc.
• Original Assignee: James N. Constant
• Inventors: Constant, James N.
• Primary Examiner(s): Corbin, John K.
• Assistant Examiner(s): Lee, John D.
• Application Number:
  US05/860,725
• Time in Patent Office: 782 Days
• Field of Search: 350/3.62, 350/3.70, 350/162 SF, 350/DIG. 1, 364/819, 364/820, 364/822, 365/215, 365/216
• US Class Current: 359/107
• CPC Class Codes: G06E 3/001 Analogue devices in which mathematical operations are carried out with the aid of optical or electro-optical elements optical elements per se G02B; devices consisting of a plurality of solid state components, including light sensitive semiconductor components, formed in or on a common substrate H01L27/14; electro-, magneto- or acousto-optics, non-linear optics G02F1/00; graph reading G06K11/00

Abstract

The disclosure describes method and apparatus for optically computing the impulse response h, transfer function H, coherence function γ, impulse coherence Γ, product S_y H_r, division 1/S_x, cross-correlation R_yx, cross-power spectrum G_yx, complex conjugate S_x^*, and convolution y*x of signals y and x in real time. The method comprises the steps of computing the mathematical function of a given parameter. The apparatus of the invention comprises the realization of optical elements for performing the tasks of the method.

Claims

1. A system for optical real time analog computation by manipulating optical signals in two spatial dimensions simultaneously, including in combination:

first and second terminal means for coupling beam signals, respectively, as inputs;

optical computation means;

first means for coupling said first terminal means to said computation means as an input;

second means for coupling said second terminal means to said computation means as an input;

said computation means having the outputs of said first and second coupling means as inputs and providing a mathematical relationship of its inputs, as an output,

said computation means including at least one spatial light modulator (SLM) for recording first input images and for reproducing output images when illuminated by second input images,

said SLM including a free carrier source for recording and reproducing optical images by forming charges in potential wells created by applying voltages to electrodes in said free carrier source.

2. A system as defined in claim 1 wherein said free carrier source is a charge coupled device (CCD).

3. A system as defined in claim 1 wherein said first and second images are from said second and first coupling means, respectively.

4. A system as defined in claim 1 wherein said recording of said first images is made with the assistance of a reference beam.

5. A system as defined in claim 1 wherein said recordings of said first images is one of amplitude, phase, amplitude and phase, and intensity recordings.

6. A system as defined in claim 1 wherein the reproducing of images is at wavelengths and times different from the recording wavelengths and times.

7. A system as defined in claim 1 wherein said SLM is one of a divider, multiplier, convolver, conjugate transformer, non-linear element, inverter, spatial shifter, and integrator.

8. A system as defined in claim 7 wherein said divider comprises:

a multiplier unit;

at least one inverter unit having input from said second means and providing output to said multiplier unit; and

means for coupling the output of said inverter units as input to said multiplier unit,

said multiplier unit having as input the signals from said first coupling means and inverter units and providing as output the signal from said first coupling means divided by the signals from said second coupling means.

9. A system as defined in claim 7 wherein said divider comprises:

a first SLM having as input the signals S_y and S_x from said first and second coupling means, said first SLM having transmittance 1/|S_x | and providing as output the signal S_y /|S_x |;

a second SLM having as input the signals S_x and S_x from said second coupling means, said second SLM having transmittance 1/|S_x | and providing as output the signal |S_x |/S_x =e^-jφ

; and

a third SLM having as input the outputs of said first and second SLMs, said third SLM having transmittance e^-jφ

and providing as output the signal S_y /S_x.

10. A system as defined in claim 7 wherein said convolver includes a multiplier unit having said first and second terminal means coupled thereto as inputs,

said multiplier unit having as input signals S_y and H_r from said first and second means and providing as output the product S_y H_r.

11. A system as defined in claim 7 wherein said convolver comprises:

a multiplier unit,

said first and second coupling means for coupling said first and second terminal means to said multiplier as input;

means included in said second coupling means for spatially shifting said input signals relative to each other; and

an integrator having the output of said multiplier unit as input and providing as output the convolution of signals from said first and second coupling means.

12. A system as defined in claim 11 wherein said integrator is a WRITE-READ-ERASE optical memory.

13. A system as defined in claim 11 wherein said shifting means is one of a mechanical, electrical and optical means for spatially shifting said input signals to said multiplier unit.

14. A system as defined in claim 11 wherein said shifting means is a charge coupled device (CCD) for spatially shifting said input signals.

15. A system as defined in claim 7 wherein said multiplier comprises:

a SLM having as input the signals S_y and H_r from said first and second coupling means and providing as output the signal S_y H_r.

16. A system as defined in claim 7 wherein said multiplier comprises:

a first SLM having as input the signals S_y and H_r from said first and second coupling means and inverter units, said first SLM having transmittance |H_r | and providing as output the signal S_y |H_r |;

a second SLM having as input the signals H_r and H_r from said second coupling means, said second SLM having transmittance 1/|H_r | and providing as output the signal H_r /|H_r |=e^jφ

; and

a third SLM having as input the outputs of said first and second SLMs, said third SLM having transmittance e^jφ and

providing as output the signal S_y H_r.

17. A system as defined in claim 7 including a conjugate transformer SLM coupled between said second coupling means and said multiplier,

said conjugate transformer having as input the signal S_x from said second coupling means and providing as output the signal S_x *,

said multiplier having as input the signals S_y and S_x * from said first coupling means and conjugate transformer, respectively, and providing as output the signal S_y S_x *.

18. A system as defined in claim 7 wherein said optical conjugate transformer comprises:

a first SLM having as input signals S_x and S_x from said first and second coupling means, said first SLM having transmittance 1/|S_x | and providing as output the signal |S_x |/S_x =e^-jφ

; and

a second SLM having as input signal S_x from said second coupling means and the output from said first SLM, said second SLM having transmittance |S_x | and providing as output the signal S_x *=|S_x |e^-jφ

.

19. A system as defined in claim 7 wherein said non-linear element comprises:

a SLM having as input signal S_x * and S_x * from said first and second coupling means, said SLM having transmittance 1/|S_x |² and providing as output the signal 1/S_x, said non-linear element being therefore a negative non-linear element.

20. A system as defined in claim 7 wherein said inverter comprises an optical conjugate transformer and negative non-linear element SLMs coupled in sequence.

21. A system as defined in claim 7 wherein the spatial shifter includes shifting means for spatially shifting recorded first images prior to reproducing output images.

22. A system as defined in claim 7 wherein the integrator includes integrating means for integrating recorded first images prior to reproducing output images.

23. A system as defined in claim 1 wherein said first coupling means and said second coupling means include Fourier analyzers.

24. A system as defined in claim 1 wherein said first coupling means includes a power spectrum analyzer and means for coupling said second terminal means to said power spectrum analyzer as input, and wherein said second coupling means includes a power spectrum analyzer.

25. A system as defined in claim 1

wherein said first coupling means includes a first power spectrum analyzer and squarer coupled in sequence, and

wherein said second coupling means includes:

second and third power spectrum analyzers;

means for coupling said second terminal means to said first and third power spectrum analyzers; and

means for coupling the outputs of said second and third power spectrum analyzers to a common output; and

wherein said first coupling means further includes means for coupling said first terminal means to said second power spectrum analyzer as input.

26. A system as defined in claim 1 including an inverse Fourier analyzer, and

means for coupling the output of said computation means to said inverse Fourier analyzer.

27. A system as defined in claim 1 wherein said first coupling means is a beam of light and wherein said second coupling means is a Fourier analyzer, inverter and inverse Fourier analyzer coupled in sequence.

28. A system as defined in claim 1 wherein said first coupling means includes a correlator and means for coupling said second terminal means to said correlator as input, and wherein said second coupling means is a power spectrum analyzer, inverter and inverse Fourier analyzer coupled in sequence.

29. A system as defined in claim 1 wherein said first coupling means includes a power spectrum analyzer, squarer and inverse Fourier analyzer coupled in sequence and means for coupling said second terminal means to said power spectrum analyzer as input, and wherein said second coupling means includes:

first and second power spectrum analyzer and inverter units coupled in sequence, and means for coupling said first terminal means to said first power spectrum analyzer and inverter; and

a second multiplier having as input the outputs from said first and second inverter units, with the output thereof coupled as input to an inverse Fourier analyzer whose output in turn is coupled as input to said computation means.

30. A system as defined in claim 1 including a Fourier analyzer, and means for coupling the output of said computation means as input to said Fourier analyzer.

31. A method of optical real time analog computation by manipulating optical signals in two spatial dimensions simultaneously including the steps of;

coupling beam signals from first and second sources as inputs to an optical computation unit having a spatial light modulator (SLM);

recording first optical images in the SLM and reproducing output optical images from the SLM by illuminating the SLM with second optical images;

said recording and reproducing steps including applying voltages to a free carrier source in the SLM, and

forming charges in potential wells in the free carrier source, whereby two dimensional optical images are recorded and reproduced from the free carrier source; and

providing a mathematical relationship of inputs as outputs from said computation unit.

32. The method of claim 31 including the step of including as SLM a charge coupled device (CCD) free carrier source

33. The method of claim 31 including the step of coupling said first and second images from said second and first sources, respectively.

34. The method of claim 31 including the step of recording said first images with the assistance of a recording beam.

35. The method of claim 31 including the step of recording one of amplitude, phase, amplitude and phase, and intensity recordings.

36. The method of claim 31 including the step of reproducing images at wavelengths and times different from the recording wavelengths and times.

37. The method of claim 31 including the step of including in said SLM one of a multiplier, convolver, conjugate transformer, non-linear element, inverter, spatial shifter, and integrator.

38. The method of claim 37 including the steps of:

including in said convolver a multiplier;

coupling said first and second coupling means to said multiplier as input; and

multiplying signals S_y and H_r from said first and second coupling means to obtain the product S_y H_r.

39. The method of claim 37 including the steps of;

including in said convolver a multiplier, shifter and integrator units;

coupling said first and second coupling means to said multiplier as input;

spatially shifting said input signals to said multiplier relative to each other;

multiplying said input signals in said multiplier; and

integrating the output of said multiplier unit to obtain the convolution of signals from said first and second coupling means.

40. The method of claim 39 including the step of integrating in a WRITE-READ-ERASE memory integrator unit.

41. The method of claim 39 including the step of shifting in a charge coupled device (CCD).

42. The method of claim 41 including the steps of:

recording one input signal at first coordinates in said CCD;

shifting said CCD record from said first to second coordinates; and

reproducing said CCD record at second coordinates.

43. The method of claim 37 including the step of including in said multiplier a single SLM having as input the signals S_y and H_r from said first and second coupling means and providing as output the signal S_y H_r.

44. The method of claim 37 including the step of including in said multiplier

a first SLM having as input signals S_y and H_r from said first and second coupling means, said first SLM having transmittance |H_r | and providing as output the signal S_y |H_r |;

a second SLM having as input the signal H_r and H_r from said second coupling means, said second SLM having transmittance 1/|H₄ | and providing as output the signal |H_r |/H_r =e^-jφ

; and

a third SLM having as input the outputs of said first and second SLMs, said third SLM having transmittance e^-jφ and

providing as output the signal S_y H_r.

45. The method of claim 37 including the steps of:

coupling a conjugate transformer SLM between said second coupling means and said multiplier;

providing as output the signal S_x * from said conjugate transformer having as input the signal S_x from said second coupling means; and

providing as output the signal S_y S_x * from said multiplier having as input the signals S_y and S_x * from said first coupling means and conjugate transformer.

46. The method of claim 37 including the step of including in said conjugate transformer:

a first SLM having as input signals S_x and S_x from said first and second coupling means, said first SLM having transmittance 1/|S_x | and providing as output the signal |S_x |/S_x =e^-jφ

; and

a second SLM having as input signal S_x from said second coupling means and the output from said first SLM, said second SLM having transmittance |S_x | and providing as output the signal S_x *=|S_x |e^-jφ

.

47. The method of claim 37 including the step of including in said non-linear element a SLM having as input signals S_x * and S_x * from said first and second sources, said SLM having transmittance 1/|S_x |² and providing as output the signal 1/S_x.

48. The method of claim 37 including the step of including in said inverter an optical conjugate transformer and negative non-linear element SLMs coupled in sequence.

49. The method of claim 37 including the step of spatially shifting recorded first images prior to reproducing output images.

50. The method of claim 37 including the step of integrating recorded first images prior to reproducing output images.

51. The method of claim 31 including the step of reproducing a division by inverting the signal from the second source and multiplying the inverted signal with the signal from the first source.

52. The method of claim 31 including the step of reproducing a division by

forming the signal S_y /|S_x | using a first SLM having transmittance 1/|S_x |;

forming the signal |S_x |/S_x =e^-jφ

using a second SLM having transmittance 1/|S_x |; and

forming the signal S_y /S_x using a third SLM having transmittance e^-jφ

.

53. The method of claim 31 including the step of coupling the output of said computation unit to an inverse Fourier analyzer.

54. The method of claim 31 including the step of coupling the output of said computation unit to a Fourier analyzer.