Associative holographic memory apparatus employing phase conjugate mirrors and a two-wave mixing contra-directional coherent image amplifier

• US 4,750,153 A
• Filed: 01/22/1986
• Issued: 06/07/1988
• Est. Priority Date: 10/11/1985
• Status: Expired due to Term

• Current Assignee: Hughes Electronics Corporation (Rtx Corporation)
• Original Assignee: Hughes Aircraft Company (Rtx Corporation)
• Inventors: Owechko, Yuri, Dunning, Gilmore J., Marom, Emanuel, Soffer, Bernard H.
• Primary Examiner(s): NOT, DEFINED
• Assistant Examiner(s): Koval, Melissa J.
• Application Number:
  US06/821,237
• Time in Patent Office: 867 Days
• Field of Search: 365/120, 365/121, 365/124, 365/125, 350/3.6, 350/3.64, 350/354, 350/3.83, 356/347, 356/348, 356/354
• US Class Current: 365/125
• CPC Class Codes: G06N 3/067 using optical means
• CPC Class Codes: G11C 13/042 using information stored in the form of interference pattern
• CPC Class Codes: G11C 15/00 Digital stores in which information comprising one or more characteristic parts is written into the store and in which information is read-out by searching for one or more of these characteristic parts, i.e. associative or content-addressed stores

Abstract

Associative holography memory apparatus is disclosed which employs a hologram, two phase conjugate mirrors, and a two-wave mixing contra-directional coherent image amplifier. The mirrors and amplifier are arranged to form a conjugate resonator whereby the output image from the apparatus tends to converge to that stored image most closely associated with an input image. Alternate embodiments are described which employ a multiple storage and erasure hologram, and which employ only a single phase conjugate mirror.

Claims

1. Associative holographic memory apparatus for recalling a stored image using an input image which includes a portion of the stored image, comprising:

a hologram having the stored image written thereon using a stored-image-associated reference beam and where the hologram has the properties of providing a probe-reference beam in response to a probe image being incident thereon and, in a reciprocal manner, providing the probe image in response to the probe-reference beam being incident thereon;

a first phase conjugate mirror;

a coherent image amplifier having the properties of transferring energy from a component of a pump beam passing through the amplifier to an overlapping component of a counter-propagating signal beam passing through the amplifier, where the amount of energy transferred between overlapping components increases with an increase in the intensity of the pump beam component;

first light path means for conveying the probe reference beam provided by the hologram through the amplifier, where it acts as a signal beam, to the first phase conjugate mirror and for conveying back to the hologram through the amplifier, where it acts as a pump beam, a phase conjugated probe reference beam generated by the first phase conjugate mirror;

a second phase congugate mirror;

second light path means for conveying the probe image provided by the hologram to the second phase conjugate mirror and for conveying back to the hologram a phase congugated probe image generated by the second phase conjugate mirror;

third light path means for conveying the input image to the hologram as a probe image; and

fourth light path means for conveying the phase conjugated probe image generated by the second phase conjugate mirror to an output image viewing plane.

2. The apparatus of claim 1 in which the first phase conjugate mirror further includes threshold means for conveying back to the hologram a phase conjugate of only those components of the probe reference beam which exceed a predetermined threshold level of beam intensity.

3. The apparatus of claim 2 in which the first light path means includes means for focusing the probe reference beam provided by the hologram onto the amplifier.

4. The apparatus of claim 1 in which the first phase conjugate mirror is a phase conjugate mirror with amplification which provides a phase conjugate probe reference beam having a greater amplitude than the corresponding probe reference beam.

5. The apparatus of claim 4 in which the amount of amplification is sufficient to overcome losses in the hologram and the second phase conjugate mirror, whereby a phase conjugate resonator cavity is formed by the combination of the first and second phase conjugate mirrors and the amplifier so that the output image tends to converge to the stored image.

6. The apparatus of claim 1 in which the hologram is a fixed hologram.

7. The apparatus of claim 1 in which the hologram is a multiple storage and erasure hologram, and further including:

fifth light path means for conveying the stored image to the hologram;

sixth light path means for conveying the stored-image-associated reference beam to the hologram; and

light blocking means for preventing the stored-image-associated reference beam from being conveyed to the first phase conjugate mirror.

8. The apparatus of claim 1 in which the hologram is a Fourier hologram.

9. Associative holographic memory apparatus for recalling a stored image using an input image which includes a portion of the stored image, comprising:

a hologram having the stored image written thereon using a stored-image-associated reference beam and where the hologram has the properties of providing a probe reference beam in response to a probe image being incident thereon and, in a reciprocal manner, of providing the probe image in response to the probe reference beam being incident thereon;

a phase conjugate mirror;

a coherent image amplifier having the properties of transferring energy from a component of a pump beam passing through the amplifier to an overlapping component of a counter-propagating signal beam passing through the amplifier, where the amount of energy transferred between overlapping components increases with an increase in the intensity of the pump beam component;

first light path means for conveying the probe reference beam provided by the hologram through the amplifier, where it acts as a signal beam, to the phase conjugate mirror and for conveying back to the hologram through the amplifier, where it acts as a pump beam, a phase conjugated probe reference beam generated by the phase conjugate mirror;

second light path means for conveying the probe image provided by the hologram to the phase conjugate mirror and for conveying back to the hologram a phase congugated probe image generated by the phase conjugate mirror;

third light path means for conveying the input image to the hologram as a probe image; and

fourth light path means for conveying the phase conjugated probe image generated by the phase conjugate mirror to an output image viewing plane.

10. The apparatus of claim 9 in which the phase conjugate mirror further includes threshold means for conveying back to the hologram a phase conjugate of only those components of the probe reference beam which exceed a predetermined threshold level of beam intensity.

11. The apparatus of claim 10 in which the first light path means includes means for focusing the probe reference beam provided by the hologram onto the amplifier.

12. The apparatus of claim 9 in which the phase conjugate mirror is a phase conjugate mirror with amplification which provides a phase conjugated probe reference beam having a greater amplitude than the corresponding probe reference beam.

13. The apparatus of claim 12 in which the amount of amplification is sufficient to overcome losses in the hologram, whereby a phase conjugate resonator is formed so that the output image tends to converge to the stored image.

14. The apparatus of claim 9 in which the hologram is a Fourier hologram.

15. Associative holographic memory apparatus for recalling a stored image using an input image which includes a portion of the stored image, comprising:

a hologram having the stored image written thereon using a stored-image-associated reference beam and where the hologram has the properties of providing a probe-reference beam in response to a probe image being incident thereon and, in a reciprocal manner, providing the probe image in response to the probe-reference beam being incident thereon;

a first phase conjugate mirror;

a coherent image amplifier having the properties of transferring energy from a component of a pump beam passing through the amplifier to an overlapping component of a counter-propagating signal beam passing through the amplifier, where the amount of energy transferred between overlapping components increases with an increase in the intensity of the pump beam component;

first light path means for conveying the probe reference beam provided by the hologram to the first phase conjugate mirror and for conveying back to the hologram a phase conjugated probe reference beam generated by the first phase conjugate mirror;

a second phase congugate mirror;

second light path means for conveying the probe image provided by the hologram through the amplifier, where it acts as a pump beam, to the second phase conjugate mirror and for conveying back to the hologram through the amplifier, where it acts as a signal beam, a phase conjugated probe image generated by the second phase conjugate mirror;

third light path means for conveying the input image to the hologram as a probe image; and

fourth light path means for conveying the phase conjugated probe image generated by the second phase conjugate mirror to an output image viewing plane.

16. The apparatus of claim 15 in which the first phase conjugate mirror further includes threshold means for conveying back to the hologram a phase conjugate of only those components of the probe reference beam which exceed a predetermined threshold level of beam intensity.

17. The apparatus of claim 16 in which the first light path means includes means for focusing the probe reference beam provided by the hologram onto the amplifier.

18. The apparatus of claim 15 in which the first phase conjugate mirror is a phase conjugate mirror with amplification which provides a phase conjugate probe reference beam having a greater amplitude than the corresponding probe reference beam.

19. The apparatus of claim 18 in which the amount of amplification is sufficient to overcome losses in the hologram and the second phase conjugate mirror, whereby a phase conjugate resonator cavity is formed by the combination of the first and second phase conjugate mirrors and the amplifier so that the output image tends to converge to the stored image.

20. The apparatus of claim 15 in which the hologram is a fixed hologram.

21. The apparatus of claim 15 in which the hologram is a multiple storage and erasure hologram, and further including:

fifth light path means for conveying the stored image to the hologram;

sixth light path means for conveying the stored-image-associated reference beam to the hologram; and

light blocking means for preventing the stored-image-associated reference beam from being conveyed to the first phase conjugate mirror.

22. The apparatus of claim 15 in which the hologram is a Fourier hologram.

23. Associative holographic memory apparatus for recalling a stored image using an input image which includes a portion of the stored image, comprising:

a hologram having the stored image written thereon using a stored-image-associated reference beam and where the hologram has the properties of providing a probe reference beam in response to a probe image being incident thereon and, in a reciprocal manner, of providing the probe image in response to the probe reference beam being incident thereon;

a phase conjugate mirror;

a coherent image amplifier having the properties of transferring energy from a component of a pump beam passing through the amplifier to an overlapping component of a counter-propagating signal beam passing through the amplifier, where the amount of energy transferred between overlapping components increases with an increase in the intensity of the pump beam component;

first light path means for conveying the probe reference beam provided by the hologram to the phase conjugate mirror and for conveying back to the hologram a phase conjugated probe reference beam generated by the phase conjugate mirror;

second light path means for conveying the probe image provided by the hologram through the amplifier, where it acts as a pump beam, to the phase conjugate mirror and for conveying back to the hologram through the amplifier where it acts as a signal beam, a phase conjugated probe image generated by the phase conjugate mirror;

third light path means for conveying the input image to the hologram as a probe image; and

fourth light path means for conveying the phase conjugated probe image generated by the phase conjugate mirror to an output image viewing plane.

24. The apparatus of claim 23 in which the phase conjugate mirror further includes threshold means for conveying back to the hologram a phase conjugate of only those components of the probe reference beam which exceed a predetermined threshold level of beam intensity.

25. The apparatus of claim 24 in which the first light path means includes means for focusing the probe reference beam provided by the hologram onto the phase conjugate mirror.

26. The apparatus of claim 24 in which the phase conjugate mirror is a phase conjugate mirror with amplification which provides a phase conjugated probe reference beam having a greater amplitude than the corresponding probe reference beam.

27. The apparatus of claim 26 in which the amount of amplification is sufficient to overcome losses in the hologram, whereby a phase conjugate resonator is formed so that the output image tends to converge to the stored image.

28. The apparatus of claim 23 in which the hologram is a Fourier hologram.

29. Associative holographic memory apparatus for recalling a stored image using an input image which includes a portion of the stored image, comprising:

a hologram having the stored image written thereon using a stored-image-associated reference beam and where the hologram has the properties of providing a probe-reference beam in response to a probe image being incident thereon and, in a reciprocal manner, providing the probe image in response to the probe-reference beam being incident thereon;

a phase conjugate mirror;

a coherent image amplifier having the properties of transferring energy from a component of a pump beam passing through the amplifier to an overlapping component of a counter-propagating signal beam passing through the amplifier, where the amount of energy transferred between overlapping components increases with an increase in the intensity of the pump beam component;

first light path means for conveying the probe reference beam provided by the hologram through the amplifier, where it acts as a signal beam, to the phase conjugate mirror and for conveying back to the hologram through the amplifier, where it acts as a pump beam, a phase conjugated probe reference beam generated by the phase conjugate mirror;

second light path means for conveying the input image to the hologram as a probe image; and

third light path means for conveying the probe image generated by the hologram to an output image viewing plane.

30. The apparatus of claim 29 in which the phase conjugate mirror further includes threshold means for conveying back to the hologram a phase conjugate of only those components of the probe reference beam which exceed a predetermined threshold level of beam intensity.

31. The apparatus of claim 30 in which the first light path means includes means for focusing the probe reference beam provided by the hologram onto the amplifier.

32. The apparatus of claim 29 in which the phase conjugate mirror is a phase conjugate mirror with amplification which provides a phase conjugate probe reference beam having a greater amplitude than the corresponding probe reference beam.

33. The apparatus of claim 32 in which the amount of amplification is sufficient to overcome losses in the hologram.

34. The apparatus of claim 29 in which the hologram is a fixed hologram.

35. The apparatus of claim 29 in which the hologram is a multiple storage and erasure hologram, and further including:

fifth light path means for conveying the stored image to the hologram;

sixth light path means for conveying the stored-image-associated reference beam to the hologram; and

light blocking means for preventing the stored-image-associated reference beam from being conveyed to the phase conjugate mirror.

36. The apparatus of claim 29 in which the hologram is a Fourier hologram.