Optical system with nanoscale projection antireflection layer/embossing

• US 20060245062A1
• Filed: 04/28/2005
• Published: 11/02/2006
• Est. Priority Date: 04/28/2005
• Status: Active Grant

• Current Assignee: Hewlett-Packard Development Company, L.P. (HP Inc.)
• Original Assignee: Hewlett-Packard Development Company, L.P. (HP Inc.)
• Inventors: Gardner, Daniel C., Piehl, Arthur R.
• Granted Patent: US 7,529,026 B2
• Time in Patent Office: Days
• US Class Current: 359/619
• CPC Class Codes: G02B 1/11 Anti-reflection coatings
• CPC Class Codes: G02B 1/118 having sub-optical wavelength surface structures designed to provide an enhanced transmittance, e.g. moth-eye structures
• CPC Class Codes: G02B 26/001 based on interference in an adjustable optical cavity interference filters G02B5/28; devices or arrangements using multiple reflections in spectrometry or monochromators G01J3/26
• CPC Class Codes: G02F 2203/12 spatial light modulator

Abstract

An optical system having a radiation transparent member and an anti-reflective embossment embossed into at least one surface of the transparent member. The embossment has spaced structures configured to permit incident radiation to pass through the embossment and the radiation transparent member, and to, at least, attenuate reflection of the incident radiation off the embossment. The structures are maximally spaced from one another by a subwavelength of the incident radiation.

Claims

1. An optical system having a radiation transparent member, comprising:

an anti-reflective embossment embossed into at least one surface of the radiation transparent member, the embossment comprising spaced structures configured to permit incident radiation to pass through the embossment and the radiation transparent member, and to, at least, attenuate reflection of the incident radiation off the embossment, the structures being maximally spaced from one another by a subwavelength of the incident radiation.

2. An optical system as set forth in claim 1, wherein the incident beam of radiation is white light and wherein the optical system comprises a light source that produces white light and a device for selectively modifying the incident white light so that it is at least redirected toward a display.

3. An optical system as set forth in claim 2, wherein the device comprises a spatial light modulator device.

4. An optical system as set forth in claim 2, wherein the spatial light modulator device comprises at least one of a DMMD, a LCOS and an interferometer type reflection device.

5. An optical system as set forth in claim 2, wherein the device is enclosed in a package comprising at least one transparent member.

6. An optical system as set forth in claim 5, wherein the at least one transparent member comprises a sheet of glass.

7. An optical system as set forth in claim 5, wherein at least one side of the transparent member is embossed with the anti-reflective embossment.

8. An optical system as set forth in claim 2, wherein the device has a transparent member which is movable with respect to a reflective member, wherein the distance between the movable member and the reflective member is selectively controlled so that white light, which enters a gap between the transparent member and the reflective member, is reflected between the transparent member and the reflective member to induce constructive and/or destructive interference and to result in the modified beam of light.

9. An optical system as set forth in claim 8, wherein the transparent member has a surface, which is outboard with respect to the reflective member, embossed with the embossment.

10. An optical system as set forth in claim 8, wherein the selective control is implemented using electrostatic actuation.

11. An optical system as set forth in claim 2, wherein the optical system further comprises a beam splitting prism arranged to receive a beam of light from the light source and to reflect the beam in a first direction into the device and wherein the modified beam of light is directed out through the beam splitting prism.

12. An optical system as set forth in claim 10, further comprising a retarder optical component for rotating an angle of polarization of light which is polarized by reflection in the beam splitting prism.

13. An optical system as set forth in claim 12, wherein the retarder layer comprises the light transmitting member.

14. An optical system as set forth in claim 1, wherein the structures are spire-like projections having radiation subwavelength dimensions.

15. An optical system as set forth in claim 14, wherein the spire-like projections are about 3-4 times higher than their base width.

16. An optical system as set forth in claim 14, wherein the spire-like projections have bases which are located proximate and/or merge with those of adjacent projections in a manner which attenuates low angle surfaces which can reflect light back away from the light transmitting member.

17. An optical system as set forth in claim 14, wherein the spire-like projections are one of essentially conical or frusto-conical in configuration.

18. An optical system as set forth in claim 1, wherein the spire-like projections are formed so that a low angle surface between the projections and which can reflect incident radiation is essentially absent.

19. An embossed anti-reflection surface in an image projection arrangement comprising:

a plurality of spire-like projections formed in a surface of a radiation transparent member through which radiation, having a wavelength range, passes to an image formation device, peaks of the spires being separated by distances which are less than any wavelength in a wavelength range of the radiation.

20. An embossed anti-reflection surface as set forth in claim 19, wherein the radiation has a wavelength or wavelength range which falls within a range of white light and wherein the image formation device comprises a matrix of elements which modify the incident radiation.

21. An embossed anti-reflection surface as set forth in claim 20, wherein the matrix of elements each comprise a radiation transparent member and a radiation reflective member which are arranged to be movable with respect one another so that a gap therebetween can be selectively controlled to induce radiation passing through the radiation transparent member to be reflected in a manner which induces constructive or destructive interference and modify radiation which is emitted back through the transparent member.

22. An embossed anti reflection surface in an image projection arrangement comprising:

a plurality of spire-like nano-scale projections formed in a surface of a transparent member which forms part of each of a matrix of light modifying elements that form an image formation device.

23. A method of reflection attenuation comprising:

forming a plurality of projections in a surface of a transparent member so that the projections have an essentially spire-shape wherein bases of the projections are located proximate and/or merge with one another and wherein peaks of the spire-shaped projections are separated by a distance which is less than any wavelength in a wavelength range of white light.

24. A method as set forth in claim 23, wherein the step of forming comprises:

forming a discontinuous layer of a selected material over the surface of the transparent member; and

etching the selected material and the surface of the transparent member to the degree that the discontinuous layer is removed and the spire-shaped projections remain.

25. A method as set forth in claim 24, wherein the step of etching is such that the transparent member is etched more rapidly than the selected material from which the discontinuous layer is formed.

26. An image formation device, comprising:

means for transmitting light, the means for transmitting having a surface; and

means for attenuating reflection from the surface using essentially conical/frustoconical-shaped nanostructures which have peaks that are spaced by a distance less than any wavelength in a wavelength range of white light.

27. An image formation device, comprising:

a plurality of transparent members arranged in a predetermined spatial relationship; and

an anti-reflective embossment formed in a surface of at least two of the plurality of transparent members, the anti-reflective embossment comprising essentially conical/frustoconical-shaped nanostructures which have peaks that are spaced by a distance less than a wavelength in a wavelength range of visible white light.

28. A method of enhancing contrast ratio performance in an image forming device comprising:

forming an anti-reflective embossment in at least one surface a transparent member through which light passes and off the surface of which a fraction of the light otherwise tends to be reflected;

reducing, using the anti-reflection embossment, the reflection of light which is of a color different from light that is modified and redirected back through the transparent member.

29. A method as set forth in claim 28, wherein the step of forming the anti-reflective embossment comprises forming shaped nanostructures which have peaks that are spaced by a distance less than a wavelength of white light.

30. An image formation device comprising:

a beam splitter into which a beam of light is directed;

an anti-reflective embossment formed in at least one surface of the beam splitter, the anti-reflective embossment comprising essentially conical/frustoconical-shaped nanostructures which have peaks that are spaced by a distance less than a wavelength of white light.

31. An image formation device as set forth in claim 30, further comprising a LCOS (liquid crystal on silicon) device associated with the beam splitter.

32. An image formation device as set forth in claim 31, further comprising a second beam splitter which is associated with the first said beam splitter and second and third LCOS devices associated with the second beam splitter.

33. An image formation device as set forth in claim 32, wherein the at least one surface comprises an interface between the first said beam splitter and the second beam splitter.

34. An image formation device as set forth in claim 32, further comprising a second anti-reflective embossment formed in at least one surface of the first said LCOS device and the second and third LCOS devices, the anti-reflective embossment comprising essentially conical/frustoconical-shaped nanostructures which have peaks that are spaced by a distance less than a wavelength of white light.

35. An image formation device as set forth in claim 34, wherein the essentially conical/frustocon ical-shaped nanostructu res are stochastically distributed.