FOURIER TRANSFORM HOLOGRAPHIC STORAGE AND RETRIEVAL SYSTEM

• US 3,697,149 A
• Filed: 12/10/1969
• Issued: 10/10/1972
• Est. Priority Date: 12/10/1969
• Status: Expired due to Term

• Current Assignee: Bob V. Markevitch, David R. Rodal, Jacob Van Heeckeren
• Original Assignee: Bob V. Markevitch, David R. Rodal, Jacob Van Heeckeren
• Inventors: Van Heeckeren, Jacob, Rodal, David R., Markevitch, Bob V.
• Primary Examiner(s): Schonberg, David
• Assistant Examiner(s): Sherman, Robert L.
• Application Number:
  US04/883,738
• Time in Patent Office: 1,035 Days
• Field of Search: 350/3.5,162SF
• US Class Current: 369/103
• CPC Class Codes: G03H 1/16 using Fourier transform G03H1/10, G03H1/12, G03H1/14 take precedence; analogue computers G06G, e.g. G06G7/19
• CPC Class Codes: G11C 13/042 using information stored in the form of interference pattern

Abstract

A storage and retrieval system wherein information is represented as a Fourier transform, which in turn is recorded on film by a holographic process to thereby preserve the phase as well as the amplitude of the Fourier transform. Coherent light is introduced to a reflective or a transmissive light modulator, which includes a bit array which is selectively energized to represent the information. The Fourier transform is taken of the whole (optical) array of bits with a lens, and is recorded on film as a hologram utilizing both an object and a reference beam obtained from the coherent light source. All bit transforms cover the same area of the hologram since the Fourier transform of each bit covers the exact same area of the recording. A series of holograms may be recorded along a pre-selected length and width of film in the form of a microfiche or on a continuous tape. The reproduce portion of the system includes a beam of coherent light which impinges the hologram preferably at an angle equal to the angle with which the reference beam impinged the film during the record process. An image of the modulator array is produced which is visually manipulated, or which may be focused via a lens onto a vidicon picture tube, or other readout device, which provides a continuous electrical signal representative of the light pattern.

Claims

1. A Fourier transform hologram apparatus for handling selected continuous information containing phase and amplitude signals, including coherent light source means, a light sensitive recording medium disposed in a given transform plane, optical beam forming means including beam splitter means disposed to receive the light beam from the coherent light source means and adapted to provide coherent reference and object light beams, said coherent reference and object beams being superimposed on a selected region of the recording medium to define a hologram recording containing the information phase and amplitude signals, comprising the combination of:

light modulator means including a plurality of distinct nonsymmetrical light modulating elements defining a nonsymmetrically repetitive array of bits disposed to receive the object light beam and to selectively modulate the respective portion of the beam cross section which impinges each nonsymmetrical element;

energizing means operatively coupled to each non-symmetrical element to continuously and selectively control the light output from each element commensurate with the selected continuous information introduced thereto to define a selectively modulated object light beam cross section;

first lens means disposed to introduce the object light beam to the light modulator means and to receive the selectively modulated object light beam therefrom, said first lens means forming a Fourier transform of the modulated beam at said selected region of the recording medium; and

second lens means disposed to receive the reference and object beam from the beam splitter means to direct the object beam into said first lens means, and to direct the reference beam to said selected region of the recording medium at a selected angle thereto.

2. The apparatus of claim 1 wherein said light modulator means is a reflective object type of light modulator formed of a plurality of distinct non-symmetrical light reflective elements disposed along a common plane, said plane and thus said elements being disposed at a slight angle with respect to the axis of the incoming object beam, to selectively reflect light directed to the elements in response to said energizing means and the continuous information to be recorded, wherein the reflected selectively modulated object beam is directed back towards the first lens means slightly off-axis.

3. The apparatus of claim 2 wherein, said first lens means includes a single converging lens disposed to intercept the object beam initiated by the optical beam forming means, direct the beam to the reflective light modulator means, accept the reflected selectively modulated object beam from the slightly angled light modulator means in slightly off-axis relation, and redirect the modulated object beam towards said recording medium;

and said second lens means is disposed to receive the object beam from thE beam splitter means and direct same into said converging lens along the axis thereof, and includes optical reflective means disposed slightly off-axis for receiving the reflected selectively modulated object beam from the converging lens and directing same to the recording medium.

4. The apparatus of claim 3 including transform lenses disposed to receive the modulated object beam from the optical reflective means, and which in combination with the converging lens define a three-lens transforming means, said transform lenses including a pair of converging lens selectively disposed along a common optical axis extending to said single converging lens to provide a Fourier transform display of relatively small size while employing said single converging lens of relatively large f-number and large diameter equal to the array width, relative to the small size of the transform display.

5. The apparatus of claim 3 wherein said optical beam forming means includes second converging lens disposed to receive the light beam from the light source means, and a double beam splitter having a first splitter surface disposed to receive the light beam from said second converging lens;

wherein the plane of said light modulator means is disposed at a slight angle with respect to the axis of the incoming object beam which passes through the first splitter surface;

said double beam splitter includes a second splitter surface disposed to receive the reflected selectively modulated object beam slightly off-axis and to re-direct the modulated object beam to the recording medium.

6. The apparatus of claim 1 wherein the non-symmetrical array of light modulating elements are randomly located within regularly arranged permissible areas.

7. The apparatus of claim 1 wherein the spacing of the non-symmetrical array of light modulating elements changes evenly in selected direction in accordance with a logarithmic relationship.

8. The apparatus of claim 1 wherein said light modulator means is a transmissive object type of light modulator formed of a plurality of distinct non-symmetrical light transmissive elements disposed along a common plane to selectively transmit light directed to the elements in response to said energizing means and the continuous information to be recorded, and in the form of the selectively modulated object light beam cross section.

9. The apparatus of claim 8 wherein;

said first lens means includes, a collimating lens disposed to intercept the object beam initiated by the optical beam forming means and to introduce the object beam to the non-symmetrical light transmissive elements of the light modulator, and a transform generating lens disposed to receive the selectively modulated object beam and direct same to said recording medium; and

said second lens means is disposed to receive the object beam from the beam splitter and to direct same into said collimating lens along the axis thereof.

10. The apparatus of claim 1 wherein the non-symmetrical array of light modulating elements defines a spiral configuration of selected non-symmetrical spacings between elements.

11. The apparatus of claim 10 wherein the selected non-symmetrical spacings are defined by a logarithmic function.

12. The apparatus of claim 1 wherein the non-symmetrical array of light modulating elements are randomly located across the array surface.

13. The apparatus of claim 1 wherein the spacing of the non-symmetrical array of light modulating elements changes evenly in selected direction in accordance with a quadratic relationship.

14. The apparatus of claim 1 wherein the non-symmetrical array of light modulating elements is defined by a non-symmetrical sub-array of blocks of elements of regular spacing within blocks, wherein the center-to-center spacing between the non-symmetrical blocks is a selected non-integer multiple of the element spacing.

15. The apparatus of claim 14 wherein the array is further divided into non-symmetrical segments which Define said blocks of elements, wherein the center-to-center spacing between the segments is also a selected non-integer multiple of the element spacing.

16. The apparatus of claim 1 wherein said second lens means includes optical spatial filter means selectively disposed in the object and reference beams to filter out the noise carrying portion of the light beam from the light source means.