Scanned Beam Display Having High Uniformity and Diminished Coherent Artifacts

• US 20090161191A1
• Filed: 12/21/2007
• Published: 06/25/2009
• Est. Priority Date: 12/21/2007
• Status: Active Grant

• Current Assignee: Microvision, Inc.
• Original Assignee: Microvision, Inc.
• Inventors: Powell, Karlton D.
• Granted Patent: US 7,791,810 B2
• Time in Patent Office: Days
• US Class Current: 359/207.700
• CPC Class Codes: G02B 2027/0123 comprising devices increasing the field of view
• CPC Class Codes: G02B 26/10 Scanning systems
• CPC Class Codes: G02B 27/0025 for optical correction, e.g. distorsion, aberration
• CPC Class Codes: G02B 27/0081 with means for altering, e.g. enlarging, the entrance or exit pupil
• CPC Class Codes: G02B 27/0101 characterised by optical features G02B27/0172 takes precedence
• CPC Class Codes: G02B 27/48 Laser speckle optics

Abstract

Briefly, in accordance with one or more embodiments, time averaged Moiré patterns may be utilized in a scanned beam display having a Gaussian beam profile or the like in order to tailor uniformity of the image by controlling both the near field and far field regions of the display to result in a stable and uniform scanned beam display image. Consideration is made regarding the light source parameters of focus numerical aperture, profile, shape, and/or wavelength to achieve higher uniformity and stability without resulting in significant visible coherent artifacts such as tiled intensity patterns and/or Moiré.

Claims

1. A method, comprising:

emitting a beam having a non-top hat beam profile;

scanning the beam in a raster scan across an exit pupil expander to project an image to be displayed in an eyebox, the exit pupil expander comprising an array of cells, one or more of the cells having a transmission function; and

generating a diffraction envelope from two or more spot profiles resulting from a scan line of the raster scan in the cells of the array of cells;

wherein a time averaged diffraction envelope is generated in the eyebox from the diffraction envelope from the two or more spots to reduce Moiré

in the projected image.

2. A method as claimed in claim 1, wherein said scanning comprises scanning the raster scan with two or more scan lines per cell to result in an addressability greater than one.

3. A method as claimed in claim 1, wherein said emitting comprises emitting a beam having a spot size full width at half maximum of approximately equal to one-half a pitch of the array of cells of the exit pupil expander.

4. A method as claimed in claim 1, wherein said emitting comprises emitting a beam having a spot size full width at half maximum selected to allow for a slight amount of Moiré

in the projected image to provide a reduced amount of tiling in the projected image.

5. A method as claimed in claim 1, further said emitting further comprising generally matching a cross section of the laser beam to a shape of the cells.

6. A method as claimed in claim 1, said emitting comprising selecting a spot size full width at half maximum of the beam and a clipping aperture size to result in a sufficiently reduced Michelson contrast value to result in reduced tiling of the projected image.

7. A method as claimed in claim 1, said emitting comprising selecting a ratio of full width at half maximum NA profile of the beam to beamlet spacing to have a value of approximately F=1, and ratio of clipping aperture size to beamlet spacing to have a value of approximately F=2.

8. A method as claimed in claim 1, further comprising reducing Moiré

in the projected image due to raster ripple in the raster scan via increasing addressability of said scanning.

9. A method as claimed in claim 1, wherein said emitting comprises emitting a Gaussian beam profile or a rounded top hat beam profile or an apodized sinc function profile.

10. A method as claimed in claim 1, wherein said emitting comprises providing a selected beam profile and said scanning comprising scanning the beam in a raster scan having a selected line spacing relative to spacing of the cells in the exit pupil expander in a near field region to evenly, or nearly evenly, spread the beam energy across the eyebox in a far field region.

11. A scanned beam display, comprising:

a laser source capable of emitting a beam having a non-top hat beam profile;

an exit pupil expander comprising an array of cells, one or more of the cells having a transmission function; and

a scanning mirror capable of scanning the beam in a raster scan across the exit pupil expander to project an image to be displayed in an eyebox; and

wherein the laser source in conjunction with the scanning mirror are capable of generating a diffraction envelope from two or more spot profiles resulting from a scan line of the raster scan in the cells of the array of cells, wherein a time averaged diffraction envelope is generated in the eyebox from the diffraction envelope from the two or more spot profiles to reduce Moiré

in the projected image.

12. A scanned beam display as claimed in claim 11, wherein the scanning mirror is capable of scanning the raster scan with two or more scan lines per cell to result in an addressability greater than one.

13. An apparatus as claimed in claim 11, wherein the laser source emits a beam having a spot size full width at half maximum of approximately equal to one-half a pitch of the array of cells of the exit pupil expander.

14. A scanned beam display as claimed in claim 11, wherein the laser source emits a beam having a spot size full width at half maximum selected to allow for a slight amount of Moiré

in the projected image to provide a reduced amount of tiling in the projected image.

15. A scanned beam display as claimed in claim 11, wherein the laser source emits a beam having a cross section generally matched to a shape of the cells.

16. A scanned beam display as claimed in claim 11, wherein the laser source emits a beam having a full width at half maximum size of the beam and having a clipping aperture size to result an a sufficiently reduced Michelson contrast value to result in reduced tiling of the projected image.

17. A scanned beam display as claimed in claim 11, wherein the laser source emits a beam having a selected a ratio of full width at half maximum profile NA of the beam to beamlet spacing to have a value of approximately F=1, and a selected ratio of clipping aperture size to beamlet spacing to have a value of approximately F=2.

18. A scanned beam display as claimed in claim 11, wherein the scanning mirror is capable of further reducing Moiré

in the projected image due to raster ripple in the raster scan via increased addressability.

19. A scanned beam display as claimed in claim 11, wherein the laser source is configured to emit a beam having a Gaussian beam profile or a rounded top hat beam profile or an apodized sinc function profile.

20. A scanned beam display as claimed in claim 11, wherein the laser source emits a beam having a selected beam profile and the scanning mirror scans the beam in a raster scan having a selected line spacing relative to spacing of the cells in the exit pupil expander in a near field region to evenly, or nearly evenly, spread energy of the beam across the eyebox in a far field region.

21. A scanned beam display as claimed in claim 11, wherein the cells of the exit pupil expander are generally hexagonal in shape.

22. A scanned beam display as claimed in claim 11, wherein the scanning mirror comprises a MEMS based scanner.

23. An apparatus, comprising:

a light source capable of emitting a beam having a non-top hat beam profile; and

a scanner capable of scanning the beam in a raster scan across an exit pupil expander to project an image to be displayed, the exit pupil expander comprising an array of cells, one or more of the cells having a transmission function;

wherein the light source in conjunction with the scanner are capable of generating a diffraction envelope from two or more spot profiles resulting from scan lines of the raster scan in a cell of the exit pupil expander, wherein a time averaged diffraction envelope is generated from the diffraction envelope from the two or more spot profiles to reduce Moiré

in the projected image.

24. An apparatus as claimed in claim 23, wherein the scanner is capable of scanning the raster scan with two or more scan lines per cell to result in an addressability greater than one.

25. An apparatus as claimed in claim 23, wherein the light source is configured to emit a beam having a spot size full width at half maximum of approximately equal to one-half a pitch of the array of cells of the exit pupil expander.

26. An apparatus as claimed in claim 23, wherein the light source is configured to emit a beam having a spot size full width at half maximum selected to allow for a slight amount of Moiré

in the projected image to provide a reduced amount of tiling in the projected image.

27. An apparatus as claimed in claim 23, wherein the light source is configured to emit a beam having a cross section generally matched to a shape of the cells of the exit pupil expander.

28. An apparatus as claimed in claim 23, wherein the light source is configured to emit a beam having a full width at half maximum size of the beam and having a clipping aperture size to result in a sufficiently reduced Michelson contrast value to result in reduced tiling of the projected image.

29. An apparatus as claimed in claim 23, wherein the light source is configured to emit a beam having a selected a ratio of full width at half maximum profile NA of the beam to beamlet spacing to have a value of approximately F=1, and a selected ratio of clipping aperture size to beamlet spacing to have a value of approximately F=2.

30. An apparatus as claimed in claim 23, wherein the scanner is capable of further reducing Moiré

in the projected image due to raster ripple in the raster scan to via increased addressability.

31. An apparatus as claimed in claim 23, wherein the light source is configured to emit a beam having a Gaussian beam profile or a rounded top hat beam profile or an apodized sinc function profile.

32. An apparatus as claimed in claim 23, wherein the light source is configured to emit a beam having a selected beam profile and the scanner scans the beam in a raster scan having a selected line spacing relative to spacing of the cells in the exit pupil expander in a near field region to evenly, or nearly evenly, spread energy of the beam across projected image in a far field region.

33. An apparatus as claimed in claim 23, wherein the cells of the exit pupil expander are generally hexagonal in shape.

34. An apparatus as claimed in claim 23, wherein the scanner comprises a MEMS based scanner.