HOLOGRAPHIC NON-ISOTROPIC DIFFUSING SCREEN

• US 3,708,217 A
• Filed: 04/28/1971
• Issued: 01/02/1973
• Est. Priority Date: 04/28/1971
• Status: Expired due to Term

• Current Assignee: Donald H. Mcmahon
• Original Assignee: Donald H. Mcmahon
• Inventors: McMahon, Donald H.
• Primary Examiner(s): Schonberg, David
• Assistant Examiner(s): Sherman, Robert L.
• Application Number:
  US05/138,228
• Time in Patent Office: 615 Days
• Field of Search: 350/3.5 161/3.5
• US Class Current: 359/15
• CPC Class Codes: G02B 27/0944 Diffractive optical elements, e.g. gratings, holograms gratings per se G02B5/18; holograms used as optical elements per se G02B5/32
• CPC Class Codes: G02B 5/0252 using holographic or diffractive means
• CPC Class Codes: G02B 5/32 Holograms used as optical elements
• CPC Class Codes: G03H 1/0465 Particular recording light; Beam shape or geometry G03H1/06 takes precedence
• CPC Class Codes: G03H 1/26 Processes or apparatus specially adapted to produce multiple sub- holograms or to obtain images from them, e.g. multicolour technique
• CPC Class Codes: G03H 2001/0413 for recording transmission holograms
• CPC Class Codes: G03H 2210/20 2D object
• CPC Class Codes: Y10S 359/90 Methods

Abstract

A method and apparatus for constructing a holographic nonisotropic diffusing screen to produce a diffuse light beam of predetermined directionality having use in micro-holographic recording and reading apparatus.

Claims

1. A method for providing a directional diffuse light beam of predetermined convergence, comprising the steps of providing first and second coherently related light beams for incidence on a holographic recording plate in angularly separated and at least partially superposed relation, positioning an isotropic diffusing means in the path of the first beam for uniformly diffusing said first beam, disposing a holographic recording medium to receive the second beam and a diverging portion of the first beam emanating from the isotropic diffusing means to record an interference pattern representative of the size of said diverging portion at the location of the isotropic diffusing means, removing the isotropic diffusing means and the first and second beams, and propagating a light beam onto the holographic recording medium antidirectional to the second beam whereby a diffuse converging beam is produced conforming to the solid angle dimensions of said diverging portion of The first beam incident on the holographic recording medium during recording of the interference pattern.

2. The method of claim 1 wherein the second beam incident on the holographic recording medium is substantially larger than said diverging portion of the first beam at the location of the isotropic diffusing means.

3. The method of claim 1 wherein the first and second beams are derived from a comparatively small laser beam and further including the step of disposing beam expanding and collimating means in the path of the second beam for directing the second beam onto the holographic recording medium as a collimated beam substantially larger than the first beam impinging on the isotropic diffusing means.

4. A method of constructing a non-isotropic diffusing screen for providing a diffuse light beam of predetermined convergence comprising the steps of providing first and second coherently related light beams, positioning a holographic recording means in the path of the second beam, and positioning isotropic diffusing means in the path of the first beam, absent a recording object, for uniformly diffusing said first beam such that a diverging portion thereof is incident in angularly separated and at least partially superposed relation with the second beam on said holographic recording means to form an interference pattern therein representative of the size of the first beam striking the isotropic diffusing means whereby subsequent illumination of said holographic recording medium with a single light beam propagated opposite to the direction of the second beam reconstructs said diverging portion of the first beam incident on the holographic recording means to produce a diffuse converging beam.

5. The method of claim 1 wherein the second beam is a converging beam converging to a point in back of the holographic recording medium on the side opposite the side on which the first and second beams impinge.

6. Apparatus for constructing a non-isotropic diffusing screen for providing a diffuse converging light beam comprising means for providing first and second coherently related light beams, holographic recording means disposed in the path of the second beam, isotropic diffusing means positioned in the path of the first beam, in the absence of a recording object, for uniformly diffusing said first beam so that a portion thereof diverging from said isotropic diffusing means impinges on said holographic recording medium in angularly separated and at least partially superposed relation with the second beam to form an interference pattern in said holographic recording means representative of the size of the first beam striking said isotropic diffusing means whereby subsequent illumination of said holographic recording medium with a single light beam propagated opposite to the direction of the second beam reconstructs said diverging portion of the first beam incident on said holographic recording means to produce the diffuse converging beam.

7. The apparatus of claim 6 including beam expander means disposed in the path of the second beam for enlarging the size thereof so as to be substantially equivalent in size to said diverging diffuse beam at the location of the recording medium.

8. Holographic recording apparatus comprising holographic recording means, means including a light source for providing first and second spaced coherently related light beams directed in angularly separated and at least partially superposed relation onto said recording means for producing an interference pattern representative of an object disposed in the path of the first beam intermediate said light source and said recording means, and holographic non-isotropic diffusing means disposed proximate the object for directing light scattered from the object onto said recording means as a diffuse converging beam to impinge on a prescribed area of the recording means.