Directional diffuser

• US 20020141065A1
• Filed: 08/01/2001
• Published: 10/03/2002
• Est. Priority Date: 08/01/2000
• Status: Active Grant

• Current Assignee: Aztech Systems Limited
• Original Assignee: James Cowan, Kenneth A. Haines
• Inventors: Haines, Kenneth A., Cowan, James
• Granted Patent: US 6,608,722 B2
• Time in Patent Office: Days
• US Class Current: 359/599
• CPC Class Codes: G02B 5/021 the diffusion taking place at the element's surface, e.g. by means of surface roughening or microprismatic structures
• CPC Class Codes: G02B 5/0215 the surface having a regular structure
• CPC Class Codes: G02B 5/0221 the surface having an irregular structure G02B5/0226 takes precedence
• CPC Class Codes: G02B 5/0252 using holographic or diffractive means
• CPC Class Codes: G02B 5/0257 creating an anisotropic diffusion characteristic, i.e. distributing output differently in two perpendicular axes
• CPC Class Codes: G02B 5/0278 used in transmission
• CPC Class Codes: G02B 5/0284 used in reflection
• CPC Class Codes: G02B 5/045 Prism arrays
• CPC Class Codes: G02B 5/1814 structurally combined with one or more further optical elements, e.g. lenses, mirrors, prisms or other diffraction gratings G02B5/189 takes precedence
• CPC Class Codes: Y10S 359/90 Methods

Abstract

A diffuser is disclosed which transmits or reflects incident light into a specific range of angles. In a preferred embodiment, this light is uniformly scattered throughout a cone of angles. The diffuser consists of two parts. The first part diffracts or reflects light into a specific offset angle. The second part, in the preferred embodiment, uniformly scatters the light through a range of angles, which is centered on the offset angle. The diffusers have utility in applications such as screens for wrist watches, computers, calculators, and cell phones.

Claims

1. A directional reflector having a surface, the surface comprising:

a first periodic surface component having a periodic wedge-shape, the periodic wedge-shape having a first period, and

a second surface component.

2. The directional reflector of claim 1, wherein the surface is reflective.

3. The directional reflector of claim 1, wherein the surface is diffractive.

4. The directional reflector of claim 1, wherein the second surface component is periodic, the second surface component having a second period.

5. The directional reflector of claim 4, wherein the second period is equal to or less than the first period.

6. The directional reflector of claim 1, wherein the second surface component is superimposed over the first surface component.

7. The directional reflector of claim 1, wherein the second surface component modifies the first surface component.

8. The directional reflector of claim 1, wherein the second surface component is random.

9. The directional reflector of claim 1, wherein the combination of the first periodic surface component and the second surface component cause an oblique light ray, which is incident on the surface, to be reflected throughout a range of angles.

10. The directional reflector of claim 9, wherein the rang e of angles is a cone of rays.

11. The directional reflector of claim 9, wherein the range of angles has a central ray and wherein the central ray is normal to the surface.

12. The directional reflector of claim 1, wherein the second periodic surface component includes a plurality of periodic surface pieces, wherein each periodic surface piece is described by a parabolic function and reflects an incident ray throughout a specified uniform range of angles.

13. The directional reflector of claim 1, wherein the second surface component has a random roughness.

15. The apparatus of claim 14, wherein the parabolic function and the offset parabolic function are selected to create a surface free of discontinuities.

17. The method for making a directional reflector having a reflective surface of claim 16, further comprising the step of coating a second periodic surface with the layer of photoresist prior to recording the desired parabolic function.

18. The method for making a directional reflector having a reflective surface of claim 17, wherein the second periodic surface is wedge-shaped.

20. The method for making a directional reflector having a reflective surface of claim 19, wherein the volume control medium is photoresist.

14. An apparatus having a surface, the surface having periodic surface elements comprising:

a first surface component in a first surface direction comprising two contiguous pieces, wherein a first surface piece is described by a parabolic function, and the second surface piece is described by an identical but inverted parabolic function;

a second surface component in a second surface direction, the second surface direction being orthogonal to the first surface direction, comprising two contiguous pieces wherein a third surface piece is described by an offset parabolic function, and a fourth surface piece is described by an identical but inverted offset parabolic function thereby creating a surface which is capable of transmitting or reflecting oblique incident light into a bundle of rays which are uniformly distributed about a normal to its surface.

16. A method for making a directional reflector having a reflective surface, wherein the reflective surface includes at least one periodic surface comprising a plurality of periodic surface pieces and wherein the period surface pieces are each described by a parabolic function and reflect an incident ray throughout a specified uniform cone of angles, comprising the steps of:

creating a gray scale mask;

transmitting recording light through the gray scale mask such that a desired parabolic function is displayed; and

recording the desired parabolic function in a layer of photoresist.

19. A method for making a directional reflector for reflecting an amount of incident light, the directional reflector having a reflective surface, wherein the reflective surface includes at least one periodic surface and wherein the periodicity of the at least one periodic surface is on the order of a wavelength of the incident light, comprising the step of holographically creating an off-axis diffuser in a volume recording material, wherein the off axis diffuser is created using prism coupling and recording from the volume holographic diffuser into a surface relief diffuser.

21. A method for making a directional reflector for reflecting an amount of incident light, the directional reflector having a reflective surface, wherein the reflective surface has a periodicity on the order of a wavelength of the incident light and wherein the reflective surface further includes a coarse periodicity having an asymmetrical blazed profile and a fine periodicity, comprising the steps of:

creating the coarse periodicity having an asymmetrical blazed profile by prism coupling and recording into a layer of photoresist using more than one beam, wherein each beam is separated by a small angle and wherein each beam is incident at a large oblique angle; and

creating the fine periodicity by reflecting a single beam from the layer of photoresist using prism coupling.

22. The method for making a directional reflector having a reflective surface of claim 21 further comprising the step of adding a diffuse component by having one beam be incident through the photoresist layer onto a predetermined diffuse reflector by means of prism coupling.

25. The method for making a directional reflector having a reflective surface of claim 24, further comprising the steps of:

creating a metal replica from the sprayed plastic replica;

creating a second plastic replica from the metal replica; and

spraying the second plastic replica with a fine droplet spray containing a plastic solvent.

23. A method for obtaining white light using a directional reflector having a reflective surface, wherein the reflective surface has a periodicity on the order of a wavelength of incident light and wherein the reflective surface further includes a coarse periodicity having an asymmetrical blazed profile and a fine periodicity, comprising the steps of:

creating the coarse periodicity having an asymmetrical blazed profile by prism coupling and recording into a layer of photoresist using more than one beam, wherein each beam is separated by a small angle and wherein each beam is incident at a large oblique angle;

creating the fine periodicity by reflecting a single beam from the layer of photoresist using prism coupling; and

recording the fine periodicity in adjacent narrow parallel stripes, wherein each stripe reflects a different color.

24. A method for making a directional reflector having a reflective surface, the reflective surface comprising a first periodic surface component having a periodic wedge-shape, the periodic wedge-shape having a first period and a second periodic surface component, the second periodic surface component having a second period, wherein the combination of the first periodic surface component and the second periodic surface component cause an oblique light ray, which is incident on the reflective surface, to be reflected into a cone of rays, comprising the steps of:

mechanically ruling the wedge-shape;

creating a plastic replica from the mechanical ruling;

creating a random array of shallow parabolic depressions by spraying the plastic replica with a fine droplet spray containing a plastic solvent.

26. The method for making a directional reflector having a reflective surface of claim wherein the steps are repeated.