APPARATUS AND METHOD FOR HOLOGRAM COPYING WITH REFERENCE BEAM INTENSITY CONTROL

• US 3,647,289 A
• Filed: 03/28/1969
• Issued: 03/07/1972
• Est. Priority Date: 03/28/1969
• Status: Expired due to Term

• Current Assignee: Mellon Bank National Association A National Banking Association
• Original Assignee: Bob L. Weber
• Inventors: Weber, Bob L.
• Primary Examiner(s): Matthews, Samuel S.
• Assistant Examiner(s): Greiner, Robert P.
• Application Number:
  US04/811,384
• Time in Patent Office: 1,075 Days
• Field of Search: 355/2 350/3.5
• US Class Current: 359/12
• CPC Class Codes: G03H 1/20 Copying holograms by holographic , i.e. optical means
• CPC Class Codes: Y10S 359/90 Methods

Abstract

A technique for making a copy of an off-axis hologram wherein the hologram and a photosensitive copy detector are placed very close together with a means therebetween, for significantly attenuating that portion of a reconstructing light beam which is undiffracted by the hologram without significantly altering the intensity of an image carrying first order diffracted beam.

Claims

2. The improved method according to claim 1 wherein the step of attenuating said undiffracted beam includes placing a filter between the hologram and the copy detector which attenuates said undiffracted beam while allowing said at least one image carrying beam to pass substantially unattenuated.

3. The improved method according to claim 1 wherein the step of attenuating said undiffracted beam includes the step of locating a filter between the hologram and copy detector, said filter characterized by attenuation of light an amount dependent upon its angle of incidence thereon.

4. The improved method according to claim 1 wherein the step of attenuating said undiffracted beam includes placing a multifilm dielectric optical filter between the hologram and the copy detector.

5. The improved method of making a hologram copy according to claim 1 wherein the step of attenuating said unidiffracted beam includes the step of partially reflecting said undiffracted beam without significantly attenuating said at least one image carrying beam.

6. The improved method of claim 1 wherein the step of attenuating includes attenuating said undiffracted beam to an intensity substantially equal to the intensity of said image carrying beam at the copy detector.

7. In a method of making a copy of an off-axis hologram, including the steps of:

directing a coherent light beam to the hologram in a manner to produce at least one image carrying beam angularly displaced from an undiffracted beam, and locating a photosensitive copy detector in a position relative to the hologram to ordinarily intercept both said at least one image carrying beam and said undiffracted beam in interference with each other;

the improvement comprising the combined steps of;

substantially blocking said undiffracted beam after leaving the off-axis hologram; and

directing an independent reference beam coherent with said coherent light beam onto said hologram detector for interference with said at least one image carrying beam.

8. The image carrying method according to claim 7 wherein the step of substantially blocking said undiffracted beam includes placing a filter between the hologram and the copy detector which attenuates said undiffracted beam while allowing said at least one image-carrying beam to pass substantially unattenuated.

9. The improved method according to claim 7 wherein the step of substantially blocking said undiffracted beam includes placing a multifilm dielectric optical filter between the hologram and the copy detector.

10. The improved method of making a hologram copy according to claim 7 wherein the step of substantially blocking said undiffracted beam includes the step of reflecting said undiffracted beam without significantly attenuating said at least one image carrying beam.

11. The improved method of making a hologram copy according to claim 7 wherein the step of substantially blocking said beam includes the step of placing a plurality of thin opaque sheets between the hologram and copy detector in a manner to present only their thickness in the path of said at least one image carrying beam.

12. The improved method of making a hologram copy according to claim 11 which includes the additional step of moving said sheets parallel to the copy detector during its exposure.

13. Apparatus for making a copy of an off-axis hologram, which includes, means for directing a coherent light beam to the hologram in a manner to produce at least one image carrying beam angularly displaced from an undiffracted beam, a photosensitive copy detector located in a position relative to the hologram to ordinarily intercept both said at least one image carrying beam and said undiffracted beam in interference with each other;

the improvement comprising, a multifilm dielectric optical filter located betwEen the hologram and the photosensitive copy detector.

14. Apparatus according to claim 13 wherein said multifilm dielectric optical filter significantly attenuates said undiffracted beam while allowing said at least one image carrying beam to pass substantially unattenuated.

15. Apparatus according to claim 13 wherein said multifilm dielectric optical filter substantially blocks said undiffracted beam while allowing said at least one image carrying beam to pass substantially unattenuated.

16. Apparatus according to claim 13 wherein said photosensitive copy detector includes photographic film and wherein said optical filter is characterized by significant attenuation of said undiffracted beam so that the intensity of said undiffracted beam is substantially equal to the intensity of said undiffracted beam at said photographic film.

17. Apparatus for making a copy of an off-axis hologram, which includes, means for directing a coherent light beam to the hologram in a manner to produce at least one image carrying beam angularly displaced from an undiffracted beam, a photosensitive copy detector located in a position relative to the hologram to ordinarily intercept both said at least one image carrying beam and said undiffracted beam in interference with each other;

the improvement comprising, substantially optically clear material with a refractive index greater than that of air and having an interface thereof with air positioned between said hologram and said photosensitive copy detector in a manner to internally reflect at least a portion of the intensity of said undiffracted beam upon passing out of said material into air without reflecting a significant portion of said at least one image carrying beam.

18. Apparatus for making a copy of an off-axis hologram, which includes, means for directing a coherent light beam to the hologram in a manner to produce at least one image carrying beam angularly displaced from an undiffracted beam, a photosensitive copy detector located in a position relative to the hologram to intercept both said at least one image carrying beam and said undiffracted beam in interference with each other;

an optical filter characterized by a degree of light transmission dependent upon the light'"'"''"'"'s angle of incidence upon said filter and placed between the hologram and the copy detector, said filter substantially attenuating said undiffracted beam for interference with said at least one image carrying beam at said photosensitive copy detector.