NED POLARIZATION SYSTEM FOR WAVELENGTH PASS-THROUGH

• US 20140064655A1
• Filed: 08/31/2012
• Published: 03/06/2014
• Est. Priority Date: 08/31/2012
• Status: Active Grant

• Current Assignee: Microsoft Technology Licensing LLC (Microsoft Corporation)
• Original Assignee: Microsoft Technology Licensing LLC (Microsoft Corporation)
• Inventors: Levola, Tapani, Bohn, David D., Nguyen, Ian A.
• Granted Patent: US 8,885,997 B2
• Time in Patent Office: Days
• US Class Current: 385/11
• CPC Class Codes: G02B 2027/0112 comprising device for genereting colour display
• CPC Class Codes: G02B 27/0081 with means for altering, e.g. enlarging, the entrance or exit pupil
• CPC Class Codes: G02B 27/0172 characterised by optical features
• 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: G02B 6/0076 Stacked arrangements of multiple light guides of the same or different cross-sectional area

Abstract

A system and method are disclosed for providing uniform color distribution of light emitted from a light source to an eye box in a near eye display (NED). An example of the system and method uses an optical element including two or more waveguides optimized to different colors of the visible light spectrum. The optical element further includes one or more polarization state generators for controlling the polarization of light incident on the waveguides to facilitate coupling of light into a matched waveguide, and to impede coupling of light into unmatched waveguides.

Claims

1. A method for presenting an image, comprising:

(a) projecting light from a light source into an optical element, the light including at least first and second wavelength bands, and the optical element including at least first and second waveguides, the first and second waveguides each having at least one optical grating;

(b) controlling the polarization of the first wavelength band incident on the first waveguide to be different than the polarization of the other than first wavelength bands incident on the first waveguide so that the first wavelength band couples within the first waveguide to a greater extent than the other than first wavelength bands; and

(c) controlling the polarization of the second wavelength band incident on the second waveguide to be different than the polarization of the other than second wavelength bands incident on the second waveguide so that the second wavelength band couples within the second waveguide to a greater extent than the other than second wavelength bands.

2. The method of claim 1, wherein said step of controlling the polarization of the first wavelength band to be different than the polarization of the other than first wavelength bands comprises the step of modifying the polarization of the first wavelength band incident on the first waveguide while maintaining the polarization of the other than first wavelength bands incident on the first waveguide.

3. The method of claim 1, wherein said step of controlling the polarization of the first wavelength band to be different than the polarization of the other than first wavelength bands comprises the step of modifying the polarization of the first wavelength band incident on the first waveguide from a first state to a second state, the first wavelength band coupling within the first waveguide to a greater extent in the second state as compared to the first state.

4. The method of claim 1, wherein said step of controlling the polarization of the first wavelength band to be different than the polarization of the other than first wavelength bands comprises the step of modifying the polarization of other than first wavelength bands incident on the first waveguide from a first state to a second state.

5. The method of claim 4, wherein said step of controlling the polarization of the second wavelength band to be different than the polarization of the other than second wavelength band comprises the step of modifying the second wavelength band incident on the second waveguide from the second state to the first state.

6. The method of claim 1, wherein said step of controlling the polarization of the first wavelength band to be different than the polarization of the second and third wavelength bands comprises the step of modifying the polarization of the first wavelength band incident on the first waveguide from a polarization where a magnetic field component of the first wavelength band along a grating vector is zero to a polarization where an electric field component of the first wavelength band along the grating vector is zero, while the second and third wavelength bands have a polarization where a magnetic field component of the second and third wavelength bands along the grating vector is zero.

7. The method of claim 6, wherein said step of controlling the polarization of the second wavelength band to be different than the polarization of the third wavelength band comprises the step of modifying the polarization of the second wavelength band incident on the second waveguide from a polarization where a magnetic field component of the second wavelength band along the grating vector is zero to a polarization where an electric field component of the second wavelength band along the grating vector is zero, while the third wavelength band has a polarization where a magnetic field component of the third wavelength band along the grating vector is zero.

8. The method of claim 1, wherein said step of controlling the polarization of the first wavelength band to be different than the polarization of the second and third wavelength bands comprises the step of modifying the polarization of the second and third wavelength bands incident on the first waveguide from a polarization where an electric field component of the second and third wavelength bands along the grating vector are zero to a polarization where a magnetic field component of the second and third wavelength bands along the grating vector are zero, while the first wavelength band has a polarization where an electric field component of the first wavelength band along the grating vector is zero.

9. The method of claim 1, wherein said step of projecting light including a first wavelength band from a display into an optical element comprises the step of projecting light wherein the first and second wavelength bands are comprised of light from the visible spectrum.

10. The method of claim 1, wherein the at least first and second waveguides comprise four waveguides.

12. The method of claim 10, wherein, after passing through a first polarization state generator positioned between the light source and a first waveguide, a first wavelength band is in polarization state 1 where the electric vector is perpendicular to the grating vector and the wavelength bands 2 to n are in polarization state 2, where the electric vector is perpendicular to the electric vectors of the first band.

13. The method of claim 10, wherein the n^th wavelength band passes through m−

1 waveguides with its polarization set to a state where coupling of the n^th wavelength band within the m−

1 waveguides is impeded, and wherein the n^th wavelength band passes through the m^th waveguide with its polarization set to a state where coupling of the n^th wavelength band within the m^th waveguide is allowed.

14. The method of claim 13, wherein the n^th wavelength band passes through m−

1 waveguides with its polarization set to polarization state 2, and wherein nth wavelength band passes through the m^th waveguide with its polarization set to polarization state 2.

11. A method for presenting an image, comprising:

(a) projecting light from a light source into an optical element, the light including between 2 and n wavelength bands, and the optical element including between 2 and m waveguides, the i^th wavelength band being matched to the j^th waveguide, where i=1 to n and j=1 to m; and

(b) passing one or more wavelength bands of the 2 to n wavelength bands through a plurality of polarization state generators, each polarization state generator associated with a waveguide of the 2 to m waveguides, the plurality of polarization state generators controlling the polarization of the one or more wavelength bands passing therethrough to a state facilitating coupling of the i^th wavelength band within the j^th waveguide, while impeding coupling of remaining wavelength bands passing through the j^th waveguide.

15. An optical element for transmitting light from a light source to an eye box, comprising:

a first waveguide, the first waveguide including at least a first optical grating for receiving light from the light source and coupling a first portion of the light into the first waveguide;

a second waveguide, the second waveguide including at least a second optical grating for receiving light from the light source and coupling a second portion of the light into the second waveguide;

a first polarization state generator between the light source and first waveguide, the first polarization state generator modifying a polarization of the first portion of light to couple into the first waveguide; and

a second polarization state generator between the first diffraction grating and the second diffraction grating, the second polarization state generator modifying a polarization of the second portion of light to couple into the second waveguide.

16. The optical element recited in claim 15, the first polarization state generator controlling the polarization of the second portion of light to impede coupling of the second portion of light within the first waveguide.

17. The optical element recited in claim 16, the first polarization state generator controlling the polarization of the first and second portions of light so that the first portion of light is polarized to a state where the electric field component along a grating vector is diminished after passing through the first polarization state generator, and the second portion of light is polarized to a state where the magnetic field component along the grating vector is diminished after passing through the first polarization state generator.

18. The optical element recited in claim 17, the second polarization state generator controlling the polarization of the second portion of light so that the second portion of light is polarized to a state where the electric field component along the grating vector is diminished after passing through the second polarization state generator.

19. The optical element recited in claim 15, wherein the polarization state generator is a polarization retarder.

20. The optical element recited in claim 15, wherein the first and second waveguides and the polarization state generator are planar members formed in a near eye display for generating a mixed reality environment.