Directional light filter and holographic projector system for its production

• US 5,642,209 A
• Filed: 01/31/1995
• Issued: 06/24/1997
• Est. Priority Date: 02/22/1993
• Status: Expired due to Fees

• Current Assignee: Kenneth M. Baker
• Original Assignee: Kenneth M. Baker
• Inventors: Baker, Kenneth M.
• Primary Examiner(s): Dzierzynski, Paul M.
• Assistant Examiner(s): Juba, Jr., John
• Application Number:
  US08/381,204
• Time in Patent Office: 875 Days
• Field of Search: 359/577, 359/10, 359/15, 359/20, 359/28, 359/35, 359/569, 359/599, 359/1, 430/5
• US Class Current: 359/10
• CPC Class Codes: G02B 5/1885 Arranged as a periodic array
• CPC Class Codes: G02B 5/32 Holograms used as optical elements
• CPC Class Codes: G03H 1/02 Details of features involved during the holographic process; Replication of holograms without interference recording
• CPC Class Codes: G03H 1/0248 Volume holograms
• CPC Class Codes: G03H 2001/026 Recording materials or recording processes G03H2226/11 takes precedence; corresponding details, see subgroups of G03H2260/00
• CPC Class Codes: G03H 2001/0264 Organic recording material
• CPC Class Codes: G03H 2240/21 Optical density variations
• CPC Class Codes: G03H 2240/24 Index variations only

Abstract

A photosensitive optical body is exposed by a diverging three-dimensional standing wave interference pattern generated by a holographic projector system. The projector system, using binary optics, creates a diverging lattice of hexagonal or square rod-like intensity maxima extending through the optical body. After the standing wave image is recorded and fixed, the optical body will contain a honeycomb-like grid or pattern that will cause either an absorption or a refractive index modulation effect on light that differs in incidence to the direction of normal propagation through the created channels to a focus or convergence point. This produces either a volume-absorption hologram or a volume-phase hologram (transmittance function modulated by the permittivity [index of refraction]) with such properties as depth of focus, high resolution, and a one-way (directional perspective) and anti-glare effect with reduced diffraction. Unique photosensitive aromatic diazo compounds which possess high thermal stability and soluble in non-polar solvents are provided. In the volume-absorption hologram, the compounds react with couplers within the optical body during development to form azo dye in the areas corresponding to destructive interference during exposure. While chiefly intended for use in eyeglass lenses, the optical body may also find use in telescopes, detectors, film and video cameras, and various other optical devices. The holographic projector system also affords a production method of writing highly-corrected peripheral as well as center-field mesh patterns on planar or non-planar surfaces.

Claims

1. A holographic projector system for exposing a photosensitive substrate, comprising:

a laser light source providing a relatively narrow beam of substantially collimated light;

means for expanding and distributing the intensity profile of said narrow beam to provide an expanded beam of substantially collimated light having a selected energy level distribution;

means for separating said expanded beam into a plurality of at least three substantially collimated beams which diverge with respect to each other, said beam separating means comprising a holographic diffraction grating; and

means for converging said plurality of beams toward each other thereby effecting their subsequent divergence from each other in order to result in crossing of their paths to produce a three-dimensional standing wave interference pattern for incidence upon the substrate, whereby said interference pattern produces a lattice of diverging intensity maxima in the photosensitive substrate, and whereby said converging means comprises a consecutive series of lens elements aligned along a common axis.

2. The holographic projector system of claim 1 further including correctional lens means disposed between said beam separating means and the substrate for providing a corrected three-dimensional standing wave interference pattern with substantially constant interferometric angles.

3. The holographic projector system of claim 1 wherein the photosensitive substrate comprises an eyeglass lens.

4. The holographic projector system of claim 1 wherein the photosensitive substrate includes a photosensitive material selected from the group consisting of photoresist, index of refraction modulation media, light occluding media, and light absorption media.

5. The holographic projector system of claim 4 wherein said index of refraction modulation media is selected from the group consisting of a dichromated gelatin and a photopolymer material.

6. The holographic projector system of claim 4 wherein said light absorption and occluding media is derived from a material selected from the group consisting of silver halide, leuco dye, and diazo material.

7. The holographic projector system of claim 1 wherein the photosensitive substrate includes a photosensitive material comprising vesicular diazo material.

8. The holographic projector system of claim 1 wherein the photosensitive substrate includes a photosensitive material comprising reverse vesicular diazo material.

9. The holographic projector system of claim 1 wherein the photosensitive substrate includes a photosensitive material comprising reverse vesicular diazo material in combination with azo dye imaging material.

10. The holographic projector system of claim 1 wherein said substrate has a photosensitive coating thereon.

11. The holographic projector system of claim 1 wherein said substrate has a photosensitive material distributed therein.

12. The holographic projector system of claim 11 wherein said photosensitive material comprises a diazo compound.

13. The holographic projector system of claim 11 wherein said photosensitive material comprises a diazo compound with a long chain aliphatic group.

14. The holographic projector system of claim 11 wherein said photosensitive material comprises a diazo compound soluble in a relatively nonpolar solvent.

15. The holographic projector system of claim 1 wherein said holographic diffraction grating divides the incident expanded beam principally into three mutually diverging spectral order beams of substantially the same intensity profile.

16. The holographic projector system of claim 1 wherein said holographic diffraction grating divides the incident expanded beam principally into four mutually diverging spectral order beams of substantially the same intensity profile.

17. The holographic projector system of claim 1 further including pinhole means for blocking undesired spectral order beams projected by said holographic diffraction means and scattered light.

18. The holographic projector system of claim 2 wherein the diverging lattice of intensity maxima is formed so that said maxima are generally of uniform dimension and diverge from a central point.

19. The holographic projector system of claim 2 wherein the diverging lattice of intensity maxima is formed so that said maxima are generally of uniform dimension and diverge from selected distribution points.

20. The holographic projector system of claim 1 wherein said means for expanding and distributing said narrow beam comprises beam expander means for reshaping said narrow beam to said expanded beam, and beam profile distributor means for distributing the intensity of the beam wavefront in a selected manner across the profile of said expanded beam.

21. The holographic projector system of claim 1 wherein said selected energy profile provides substantially the same intensity in each region of intensity maxima at various locations of incidence across the surface of the substrate.

22. The holographic projector system of claim 4 wherein the photosensitive substrate is exposed while immersed in a refractive index matching liquid.

23. The holographic projector system of claim 4 wherein the photosensitive substrate is exposed while in air.

24. The holographic projector system of claim 4 wherein the photosensitive substrate comprises a photoresist material developed after exposure and etched to produce a relief pattern.

25. The holographic projector system of claim 1 wherein said holographic diffraction grating is defined as:

a diffraction grating for use in a design wavelength, wherein the grating comprises a repetitive pattern of rhombic unit cells;

wherein each rhombic unit cell comprises four rhombic portions, a first pair of the rhombic portions being adjacent each other along a first side of the unit cell, and the remaining pair of the rhombic cell portions being adjacent each other along a second side of the unit cell, the remaining pair of the rhombic portions being contiguous with the first pair along one side thereof;

wherein each of the four rhombic portions is bisected into equilateral triangular regions of equal area, each of the triangular regions having an optical thickness corresponding to a phase level with respect to the design wavelength;

wherein the phase levels of the triangular regions in the first pair of rhombic portions are π

, 2π

/3, 0, and 2π

/3 radians, in order along a first direction; and

wherein the phase levels of the triangular regions in the second pair of rhombic portions are 0, 2π

/3, 0, and 5π

/3 radians, in order along a second similar parallel direction.

26. The holographic projector system of claim 1 wherein said holographic diffraction grating is defined as:

a diffraction grating for use at a design wavelength, wherein the grating comprises a repetitive pattern of rhombic unit cells;

wherein each rhombic cell unit comprises sixteen rhombic portions, a first four of the rhombic portions being in a row adjacent each other along a first side of the unit cell, the remaining rhombic portions forming rows of four, each adjacent and contiguous along a side of each previously formed row thereof;

wherein each of the sixteen rhombic portions is bisected into equilateral triangular regions of equal area, each of the triangular regions having an optical thickness corresponding to a phase level with respect to the design wavelength;

wherein the phase levels of the triangular regions in the first row of rhombic portions are 0.0, 0.0, 0.0, 0.0, 0.295167, 0.647584, 0.295167, and 0.0 radians, in order along a first direction;

wherein the phase levels of the triangular regions in the second row of rhombic portions are 0.0, 0.0, 0.647584, 0.647584, 0.647584, 0.647584, 0.647584, and 0.0 radians, along a second similar parallel direction;

wherein the phase levels of the triangular regions in the third row of rhombic portions are 0.295167, 0.647584, 0.647584, 0.647584, 0.647584, 0.647584, 0.295167, and 0.295167 radians, along a third similar parallel direction; and

wherein the phase levels of the triangular regions in the fourth row of rhombic portions are 0.295167, 0.0, 0.647584, 0.0, 0.295167, 0.295167, 0.295167 and 0.295167 radians, along a fourth similar parallel direction.

27. The holographic projector system of claim 1 wherein said holographic diffraction grating is defined as:

a diffraction grating for use at a design wavelength, wherein the grating comprises a repetitive pattern of square unit cells;

wherein each square unit cell comprises four square regions of equal area, each of the square regions having an optical thickness corresponding to a phase level with respect to the design wavelength; and

wherein the phase levels of the square regions are π

, 0, π

, and 0 radians, in order along a rotational direction.

28. The holographic projector system of claim 1 wherein said holographic diffraction grating is defined as:

a diffraction grating for use at a design wavelength, wherein the grating comprises a repetitive pattern of square unit cells;

wherein each square unit cell comprises four square regions of equal area, each of the square regions having an optical thickness corresponding to a phase level with respect to the design wavelength; and

wherein the phase levels of the square regions are 3π

/2, 0, π

/2, and π

radians, in order along a rotational direction.

29. A method of producing a lattice of diverging intensity maxima in a photosensitive substrate, said method comprising the steps of:

providing a substantially collimated beam of light having a selected energy profile;

separating the beam with a single optical element comprising a holographic diffraction grating into a plurality of at least three substantially collimated beams which diverge with respect to each other;

converging said plurality of beams toward each other through a consecutive series of lens elements aligned on a common axis, thereby to result in crossing of their paths and subsequent diverging of said beams from each other to produce a three-dimensional standing wave interference pattern to produce the lattice of diverging intensity maxima therein.

30. The method of claim 29 further including the step of correcting the interference pattern to provide substantially uniform interferometric angles.

31. The method of claim 29 wherein said step of providing the collimated beam comprises expanding a narrow light beam from a laser to form a collimated beam of expanded cross section, and distributing the beam wavefront to provide a selected intensity profile.

32. The method of claim 29 wherein said substrate comprises a lens.