Grazing incidence holograms and system and method for producing the same

• US 5,822,089 A
• Filed: 01/31/1996
• Issued: 10/13/1998
• Est. Priority Date: 01/29/1993
• Status: Expired due to Fees

• Current Assignee: Stanley H. Kremen
• Original Assignee: Imedge Technology Incorporated
• Inventors: Coleman, Zane, Phillips, Nicholas J.
• Primary Examiner(s): Spyrou, Cassandra
• Assistant Examiner(s): Juba, Jr., John
• Application Number:
  US08/594,715
• Time in Patent Office: 986 Days
• Field of Search: 359/1, 359/3, 359/4, 359/7, 359/13, 359/15, 359/27, 359/30, 359/32, 359/34, 359/35, 359/900, 430/1, 430/2
• US Class Current: 359/3
• CPC Class Codes: G03H 1/0408 Total internal reflection [TIR] holograms, e.g. edge lit or substrate mode holograms
• CPC Class Codes: G03H 2001/0473 Particular illumination angle between object or reference beams and hologram
• CPC Class Codes: G03H 2222/47 Evanescent wave
• CPC Class Codes: Y10S 359/90 Methods

Abstract

A method and system for recording and displaying grazing-incidence (i.e., steep reference beam angle) holograms supported on a substrate having thin edge-illuminatable geometry. The system and process of the present invention uses thin edge-illuminated substrates that facilitate optimal coupling of the reference light beam at steep angles approaching grazing incidence, while maximizing the contrast of the slanted fringe structures thereof. A recording medium is in direct contact with a thin substrate whose refractive index is greater than the bulk refractive index of the recording medium. At the substrate interface, the recording medium has a gradient-type index matching region, created by exposure of the recording medium to reference beam illumination, prior to the further application of an object beam to create a fringe pattern.

Claims

1. A grazing incidence holographic recording having slanted fringes recorded therein, comprising:

a substrate of thin construction, having an index of refraction of n_s, front and rear surfaces disposed substantially parallel to each other, and an edge surface disposed between said front and rear surfaces; and

a hologram made from an optically transparent material having a bulk index of refraction n_M less than n_S, front and rear surfaces and fringes prerecorded therein, and said rear surface of said hologram being disposed in contact with the front surface of said substrate along an interface of substantially planar geometry having a gradient-type index matching region.

2. A holographic recording process comprising:

(a) supporting a recording medium upon a recording substrate so that an interface is established therebetween, said recording medium containing photopolymerizable monomers that are free to migrate within said recording medium in response to light exposure and the index of refraction of said recording medium n_m being less than the refractive index of said recording substrate n_s,

(b) exposing said recording medium to a reference beam passing directly through said recording substrate at grazing incidence to the interface defined between said recording medium and said recording substrate, whereupon an evanescent wave is produced at said interface, causing said monomers in said polymerizable recording medium to migrate towards said interface, locally increasing the index of refraction adjacent said interface, and creating a gradient-type index matching region between said recording medium and said recording substrate; and

(c) exposing said recording medium to an object beam from one side thereof, and simultaneously to a reference beam passing directly through said recording substrate at grazing incidence to the interface defined between said recording medium and said recording substrate, and allowing said reference beam to enter said recording medium and interact with said object beam to create a fringe pattern fixable within said recording medium.

3. The holographic recording process of claim 2, which further comprises

(c) fixing said fringe pattern, thereby forming a hologram.

4. A holographic recording system comprising:

means for supporting a recording medium upon a recording substrate so that an interface is established therebetween, said recording medium containing photopolymerizable monomers that are free to migrate within said recording medium in response to light exposure and the index of refraction of said recording medium being less than the refractive index of said recording substrate,

means for exposing said recording medium to a reference beam passing directly through said recording substrate at grazing incidence to the interface defined between said recording medium and said recording substrate, whereby an evanescent wave is produced at said interface, causing said monomers in said polymerizable recording medium to migrate towards said interface, thereby locally increasing the index of refraction adjacent said interface, and creating a gradient-type index matching region between said recording medium and said recording substrate; and

means for exposing said recording medium to an object beam from one side thereof and simultaneously to a reference beam passing directly through said recording substrate at grazing incidence to the interface between said recording medium and said recording substrate, and allowing said reference beam to create a fringe pattern fixable within said recording medium.

5. The holographic recording system of claim 4, which further comprises

means for fixing said fringe pattern, thereby forming a hologram.