LASER ILLUMINATION DEVICE

• US 20140037242A1
• Filed: 10/17/2013
• Published: 02/06/2014
• Est. Priority Date: 04/06/2006
• Status: Active Grant

• Current Assignee: DigiLens Inc
• Original Assignee: SBG Labs Inc.
• Inventors: Popovich, Milan Momcilo, Waldern, Jonathan David, Storey, John James
• Granted Patent: US 9,746,688 B2
• Time in Patent Office: Days
• US Class Current: 385/10
• CPC Class Codes: G02B 27/425 in illumination systems mask illumination systems in photolithographic systems G03F7/70158
• CPC Class Codes: G02B 27/48 Laser speckle optics
• CPC Class Codes: G02B 5/1828 having means for producing variable diffraction controlling the direction of light by means of one or more diffracting elements G02B26/0808; acousto-optical elements G02F1/11, G02F1/33; electro- or magneto-optical diffraction G02F1/292, G02F1/2955
• CPC Class Codes: G02B 6/0023 provided by one optical element, or plurality thereof, placed between the light guide and the light source, or around the light source
• CPC Class Codes: G02B 6/0035 provided on the surface of the light guide or in the bulk of it
• CPC Class Codes: G02B 6/005 provided by one optical element, or plurality thereof, placed on the light output side of the light guide
• CPC Class Codes: G02F 1/0136 for the control of polarisation, e.g. state of polarisation [SOP] control, polarisation scrambling, TE-TM mode conversion or separation G02F1/0353 takes precedence
• CPC Class Codes: G02F 1/13342 Holographic polymer dispersed liquid crystals
• CPC Class Codes: G02F 1/133553 Reflecting elements associated to illuminating devices G02F1/133605
• CPC Class Codes: G02F 1/133606 including a specially adapted diffusing, scattering or light controlling members
• CPC Class Codes: G02F 1/13731 based on a field-induced phase transition G02F1/13781 takes precedence
• CPC Class Codes: G02F 2203/62 Switchable arrangements whereby the element being usually not switchable
• CPC Class Codes: G03B 21/2033 LED or laser light sources
• CPC Class Codes: G03H 1/0248 Volume holograms
• CPC Class Codes: G03H 1/32 Systems for obtaining speckle elimination

Abstract

An Electrically Switchable Bragg Grating (ESBG) despeckler device comprising at least one ESBG element recorded in a hPDLC sandwiched between transparent substrates to which transparent conductive coatings have been applied. At least one of said coatings is patterned to provide a two-dimensional array of independently switchable ESBG pixels. Each ESBG pixel has a first unique speckle state under said first applied voltage and a second unique speckle state under said second applied voltage.

Claims

1. An ESBG despeckler device comprising:

at least one ESBG element sandwiched between transparent substrates, each said ESBG element comprising a multiplicity of ESBG pixels disposed in a layer;

transparent conductive coatings applied to each said substrate, at least one of said coatings being patterned into independently addressable elements overlapping said pixels;

an electrical control circuit operative to apply voltages across each said pixel; and

a light coupling element disposed adjacent to one of said substrates for diverting input light from an external light source into a total internal reflection illumination path within said substrates, wherein said at least one ESBG element is disposed along said illumination path,

wherein each said ESBG pixel is characterized by a first unique speckle state under said first applied voltage and a second unique speckle state under said second applied voltage.

2. The apparatus of claim 1 wherein said first and second speckle states occur during the integration time of the human eye.

3. The apparatus of claim 1 wherein said first unique speckles state corresponds to a first unique diffracting state of said ESBG pixel and said second unique speckle state corresponds to a second unique diffracting state of said ESBG pixel, wherein said first and second diffracting states are characterised by diffraction efficiencies having values in a range extending from zero to unity.

4. The illumination device of claim 1 wherein said first and second voltages are points on a time varying voltage characteristic.

5. The apparatus of claim 1 wherein at least one ESBG element contains ESBG pixels each characterized by a unique grating vector.

6. The apparatus of claim 1 wherein at least one ESBG element contains ESBG pixels operative to convert incident collimated light into divergent light.

7. The apparatus of claim 1 wherein at least one ESBG element contains ESBG pixels operative to convert incident light into diffuse light.

8. The apparatus of claim 1 wherein at least one ESBG element contains ESBG pixels with identical optical characteristics.

9. The illumination device of claim 1 wherein at least one ESBG element contains ESBG pixels with a first phase retarding characteristic under said first voltage and a second phase retarding characteristic under said second voltage.

10. The illumination device of claim 1 wherein at least one ESBG element contains ESBG pixels with a first light diffusing characteristic under said first voltage and a second light diffusing characteristic under said second voltage.

11. The illumination device of claim 1 wherein at least one ESBG element contains ESBG pixels with optical power.

12. The apparatus of claim 1 wherein at least one ESBG element contains ESBG pixels operative to diffract light out of said total internal reflection path through one of said substrates into one of a predefined set of output light paths when said pixel is in its diffracting state.

13. The apparatus of claim 1 wherein said ESBG despeckler device comprises identical first and second ESBG elements and the waveforms applied to overlapping pixels of said first and second ESBG elements operate in anti-phase.

14. The apparatus of claim 1 wherein said ESBG despeckler device comprises identical first and second ESBG elements and ESBG pixels from said first and second ESBG elements substantially overlap in the illumination beam cross section.

15. The apparatus of claim 1 wherein said ESBG despeckler device comprises identical first and second ESBG elements and ESBG pixels from said first and second ESBG elements are offset by a fraction of the ESBG element width in at least one of the vertical or horizontal array axes in the illumination beam cross section.

16. The apparatus of claim 1 wherein said ESBG despeckler device comprises identical first and second ESBG elements and said second ESBG element is rotated through 180 degrees with respect to said first ESBG element.

17. The apparatus of claim 1 wherein said two-dimensional array of independently switchable ESBG pixels provides a Hadamard diffuser.

18. The apparatus of claim 1 wherein said external light source provides red, green and blue light and said at least one ESBG element comprises ESBGs optimised to diffract red, green and blue light.

19. The apparatus of claim 1 wherein at least one ESBG element is a hologram of a CGH having a first surface and a second surface wherein said CGH is designed to convert a laser beam incident at said first surface into a multiplicity of beams from said second surface wherein each beam has a unique direction in space and a diffusion angle, wherein said beams have single point of origin.

20. The apparatus of claim 1 wherein at least one ESBG element is recorded using a CGH having a first surface and a second surface wherein said CGH is designed to convert a laser beam incident at said first surface into a multiplicity of beams from said second surface wherein each beam has a unique direction in space and a diffusion angle, wherein said beams have points of origin equally spaced around the periphery of said CGH.