DIRECT ELECTRONIC FOURIER TRANSFORMS OF OPTICAL IMAGES

• US 3,836,712 A
• Filed: 05/30/1973
• Issued: 09/17/1974
• Est. Priority Date: 12/29/1972
• Status: Expired due to Term

• Current Assignee: Philipp G. Kornreich, Stephen T. Kowel
• Original Assignee: Philipp G. Kornreich, Stephen T. Kowel
• Inventors: Kornreich, Philipp G., Kowel, Stephen T.
• Primary Examiner(s): Murray, Richard
• Application Number:
  US05/365,054
• Time in Patent Office: 475 Days
• Field of Search: 178/7.1,7.3,7.6,5.4R,5.4BD
• US Class Current: 348/207.99
• CPC Class Codes: G02F 1/11 based on acousto-optical elements, e.g. using variable diffraction by sound or like mechanical waves acousto-optical deflection G02F1/33
• CPC Class Codes: G06V 10/10 Image acquisition document image scanning and transmission H04N1/00; control of digital cameras H04N23/60
• CPC Class Codes: G06V 10/12 Details of acquisition arrangements; Constructional details thereof
• CPC Class Codes: G06V 10/20 Image preprocessing
• CPC Class Codes: G06V 10/42 Global feature extraction by analysis of the whole pattern, e.g. using frequency domain transformations or autocorrelation
• CPC Class Codes: G08B 13/18 Actuation by interference with heat, light, or radiation of shorter wavelength; Actuation by intruding sources of heat, light, or radiation of shorter wavelength
• CPC Class Codes: G08B 13/1961 Movement detection not involving frame subtraction, e.g. motion detection on the basis of luminance changes in the image
• CPC Class Codes: G08B 13/19634 Electrical details of the system, e.g. component blocks for carrying out specific functions
• CPC Class Codes: H04N 3/10 by means not exclusively optical-mechanical H04N3/36 takes precedence

Abstract

Method and apparatus for directly converting between optical images and the spatial Fourier transforms of optical images by interacting sound waves and light. Controlled sound waves couple with optical images, and electrical signals may be derived from this coupling which are functions of the spatial Fourier transforms of the entire optical images. In a reverse process, optical images are obtained directly by coupling controlled sound waves with electrical signals which are a function of the spatial Fourier transforms of the optical images and with light.

Claims

1. A device for generating an electrical signal representation of a one-dimensional optical image comprising:

a substrate of a material capable of vibrating and means for vibrating the substrate at a plurality of different frequencies;

a film of a material whose electrical conductance varies as a function of an optical image incident thereon and as a function of time and space varying strain waves therein, said film secured to a surface of the substrate to vibrate therewith;

a pair of electrically conductive contacts disposed over a portion of the film in electrical contact therewith and spaced from each other to expose a narrow strip of film;

means for projecting an optical image on the exposed film strip;

a constant voltage source connected to the two contacts to establish a potential difference therebetween across the exposed film strip; and

means for detecting the current between the two contacts across the film strip at a plurality of different frequencies of vibration of the substrate to derive a plurality of electrical signals each being a representation of at least one dimension of the entire optical image at a defined frequency of vibration of the substrate.

2. A device as in claim 1 wherein each of said electrical signals is a component of a Fourier Transform representation of the optical image at the frequency of vibration of the substrate at which the signal is derived.

3. A device as in claim 2 wherein each of said electrical signals represents a selected component of a Fourier Transform representation of the light intensity distribution along at least one dimension of the entire optical image incident on a defined portion of the film for the frequency of vibration of the substrate at which the electrical signal is derived.

4. A device as in claim 2 wherein each of said electrical signals is a selected component of a Fourier Transform representation of the light intensity distribution along a single dimension of the entire optical image incident on a defined portion of the film for the frequency of vibration of the substrate at which the electrical signal is derived.

5. A device as in claim 1 wherein the means for vibrating the substrate causes the propagation of surface waves in the substrate.

6. A device as in claim 1 wherein the film comprises substantially a photoconductive intrinsic semiconductor.

7. A device as in claim 1 wherein the substrate comprises substantially fused quartz and the film comprises substantially polycrystalline cadmium sulfide.

8. A device for generating an electrical signal representation of an optical image comprising:

a medium comprising a film capable of undergoing time and space varying strain disturbances and having an electrical property wHich varies as a function of an optical image incident on the film and as a function of time and space varying strain disturbances in the film;

means for causing the incidence of an optical image on the film;

means for causing a plurality of different time and space varying strain disturbances in the film; and

means for measuring said electrical property of the film at a plurality of said different strain disturbances therein to derive a plurality of electrical signals representing said optical image.

9. A device as in claim 8 wherein the medium comprises a substrate acoustically coupled with the film and capable of undergoing time and space varying strain disturbances in acoustic coupling with the film.

10. A device as in claim 9 wherein each of said electrical signals is a function of the light intensity distribution along at least one dimension of the entire optical image incident on a defined portion of the film and on the strain disturbances in the film at which the signal is derived.

11. A device as in claim 9 wherein said optical image incident on the film is two-dimensional and wherein each of said electrical signals is a representation of the entire two-dimensional optical image incident on a selected portion of the film for the strain disturbances at which the signal is derived.

12. A device as in claima 9 wherein said electrical signals are selected components of a Fourier Transform representation of the optical image.

13. A device as in claim 9 wherein each of said electrical signals is a selected component of a Fourier Transform representation of the light distribution along at least one selected dimension of the optical image.

14. A device as in claim 9 wherein each of the electrical signals is a selected component of a Fourier Transform representation of the light distribution along a single dimension of the optical image.

15. A device as in claim 9 wherein each of the electrical signals is a selected component of a Fourier Transform representation of the light distribution along two noncongruent dimensions of the optical image incident on a selected portion of the film.

16. A device as in claim 8 wherein the means for causing a plurality of different strain disturbances in the film comprises means for causing the propagation of a surface strain wave in the film.

17. A device as in claim 16 wherein the means for causing strain disturbances comprises means for vibrating the film with a controlled strain wave wherein the wave vector of the strain wave is controlled in at least two noncongruent dimensions.

18. A device as in claim 17 wherein each of said electrical signals is a component of a Fourier Transform representation of the entire two-dimensional optical image incident on at least a portion of the film.

19. A device as in claim 16 wherein each of the electrical signals is a representation of at least a component of the electrical conductivity of the film.

20. Method of obtaining an electrical signal representation of an optical image comprising:

causing the incidence of an optical image on a medium having an electrical property which varies as a function of an optical image incident on it and as a function of time and space varying surface strain wave disturbances in the medium;

causing a plurality of different time and space varying surface strain wave disturances in the medium; and

measuring said electrical property of the medium at a plurality of said different surface strain wave disturbances in the medium to derive a plurality of electrical signals representing said optical image.

21. A method as in claim 20 wherein each of said electrical signals is a representation of the light distribution along at least one dimension of the optical image incident on at least a portion of the medium.

22. A method as in claim 20 wherein each of said electrical signals is a representation of the light distribution along two noncongruent dimensions of the optical image incidenT on at least a portion of the medium.

23. A method as in claim 20 wherein each of said electrical signals is a selected component of a Fourier Transform representation of said optical image incident on at least a portion of the medium.

24. A device as in claim 20 wherein each of said electrical signals is a selected component of a Fourier Transform representation of the light distribution along at least one dimension of the optical image incident on a selected portion of the medium.

25. A method as in claim 20 wherein each of said electrical signals is a selected component of a Fourier Transform representation of the two-dimensional light distribution of the optical image incident on a selected portion of the medium.

26. A method as in claim 20 including controlling the wave vector of the strain wave in the medium in at least the two dimensions of the image incident on the medium.

27. A method as in claim 26 wherein each of said electrical signals is a selected component of a Fourier Transform representation of the entire two-dimensional optical image incident on a selected portion of the medium.

28. A method as in claim 20 wherein said electrical property of the medium is at least a selected component of the electrical conductivity of the medium.

29. A device for generating an electrical signal representation of an optical image comprising:

a substrate of a material capable of undergoing time and space varying strain disturbances and a film secured to a surface of the substrate to undergo strain disturbances therewith, said film having an electrical property which varies as a function of an optical image incident on the film and as a function of time and space varying strain disturbances in the film;

means for causing the incidence of an optical image on at least a portion of the film;

means for causing a plurality of different time and space varying strain disturbances in the film; and

means for measuring said electrical property of the film at a plurality of said different strain disturbances in the film to derive a plurality of electrical signals representing said optical image, said measuring means comprising an interdigitated plurality of first and second electrically conductive contacts disposed over portions of the film in electrical contact therewith, with the first contacts electrically connected to each other and with the second contacts electrically connected to each other, but with the first and second contacts spaced from each other along the film.

30. A device as in claim 29 wherein the means for causing strain disturbances causes the propagation of a surface strain wave along the surface of the substrate facing the film.

31. A device as in claim 29 wherein each of said electrical signals is a selected component of a Fourier Transform representation of the optical image incident on at least a portion of the film.

32. A device as in claim 29 wherein the substance is substantially fused quartz and the film is substantially a photoconductive intrinsic semiconductor.

33. A device for obtaining an electrical signal representation of an optical image comprising:

a substrate of a material capable of undergoing time and space varying strain disturbances and a photocathode film secured to a surface of the substrate to undergo said strain disturbances therewith;

a photoelectron collector plate facing the photocathode film but spaced therefrom to collect electron current emitted from the photocathode film and means for establishing a potential difference between the photocathode film and the photoelectron collector plate;

means for causing the incidence of an optical image on the photocathode film;

means for causing a plurality of different time and space varying strain disturbances in the substrate and in the photocathode film; and

means for measuring an electrical parameter of the current between the photocathode film and the photoelectron collector plate at a plurality oF said different strain disturbances in the photocathode film to derive a plurality of electrical signals representing the optical image.

34. A device as in claim 33 wherein each of said electrical signals is a selected component of a Fourier Transform representation of the light distribution along at least one dimension of the optical image.

35. A device as in claim 33 wherein each of a selected plurality of said electrical signals is a selected component of a Fourier Transform representation of the entire two-dimensional optical image incident on a selected portion of the photocathode film.

36. A device for reconstructing pictorial information represented by electrical signals each of which is a selected component of a Fourier Transform representation of said pictorial information comprising:

a pair of substantially parallel polarizing plates disposed at an angle of approximately 90* between their respective planes of polarization;

a plate of elasto-optical material disposed intermediate the polarizing plates;

means for propagating through said intermediate plate strain patterns whose amplitudes and phases are governed by said electrical signals;

a light source for illuminating one side of the combination of the three plates; and

means for displaying the light pattern emerging from the side of the combination of the plate which is opposite the light source.