Substrate Guided Relay with Image Compensation

• US 20120281721A1
• Filed: 05/02/2011
• Published: 11/08/2012
• Est. Priority Date: 05/02/2011
• Status: Active Grant

• Current Assignee: Microvision, Inc.
• Original Assignee: Microvision, Inc.
• Inventors: DeJong, Christian Dean, Champion, Mark
• Granted Patent: US 8,760,745 B2
• Time in Patent Office: Days
• US Class Current: 372/9
• CPC Class Codes: G02B 2027/0118 comprising devices for improving the contrast of the display / brillance control visibility
• CPC Class Codes: G02B 26/10 Scanning systems
• CPC Class Codes: G02B 26/105 with one or more pivoting mirrors or galvano-mirrors G02B26/101 takes precedence
• CPC Class Codes: G02B 26/127 Adaptive control of the scanning light beam, e.g. using the feedback from one or more detectors G02B27/0031 takes precedence
• CPC Class Codes: G02B 27/0031 for scanning purposes
• CPC Class Codes: G02B 27/01 Head-up displays
• CPC Class Codes: H04N 9/3129 scanning a light beam on the display screen scanning a light beam on a screen in displays other than projection devices G09G3/02; scanning systems in general G02B26/10; projectors using laser light sources in general H04N9/3161
• CPC Class Codes: H04N 9/3155 for controlling the light source light source control per se H05B35/00 – H05B47/00; control of an illumination source for displays in general G09G3/3406
• CPC Class Codes: H04N 9/3182 Colour adjustment, e.g. white balance, shading or gamut white balance per se H04N9/73; control of amplitude of colour signals H04N9/68; colour control circuits for displays in general G09G5/02, G09G3/2003, G09G3/3607

Abstract

A display system includes a substrate guided relay and a scanning projector. The scanning projector exhibits a brightness variation on a resonant scanning axis, and the substrate guided relay exhibits a brightness variation along a length of an output coupler. The scanning projector includes a brightness compensation circuit to compensate for both the brightness variation caused by the resonant scanning and the brightness variation along the length of the output coupler.

Claims

1. An apparatus comprising:

a substrate guided relay that transmits light to an output coupler, where light emerging from the output coupler has a varying brightness as a function of position;

at least one laser light source;

a resonant scanning mirror that reflects a light beam from the at least one laser light source and sinusoidally scans the light beam in at least one dimension, wherein the light beam scans more slowly and results in greater perceived brightness at larger angular displacements of the scanning mirror; and

a brightness compensation circuit to alter drive values that drive the at least one laser light source, the brightness compensation circuit including compensation for both the varying brightness as a function of position as well as the greater perceived brightness at larger angular displacements of the scanning mirror.

2. The apparatus of claim 1 wherein the brightness compensation circuit applies a linear compensation for the varying brightness as a function of position.

3. The apparatus of claim 2 wherein the linear compensation contributes a gain greater than unity at at least one mirror angle.

4. The apparatus of claim 1 wherein the brightness compensation circuit applies a sinusoidal correction for the greater perceived brightness at larger angular displacements of the scanning mirror.

5. The apparatus of claim 4 wherein the sinusoidal compensation contributes a gain greater than unity at at least one mirror angle.

6. The apparatus of claim 1 wherein the brightness compensation circuit comprises a lookup table that alters drive values as a function of mirror phase.

7. The apparatus of claim 6 wherein contents of the look up table are scaled to a maximum scale factor of one.

8. An apparatus comprising:

a scanning mirror that produces an image by scanning a modulated light beam in two dimensions, wherein the scanning mirror scans sinusoidally in at least one of the two dimensions;

a substrate guided relay that accepts a scanned light beam reflected from the scanning mirror, a body to guide light to an output coupler having a length, the output coupler to receive the light from the body and output the light at a varying brightness along the length;

at least one laser light source to produce the modulated light beam in response to a drive signal; and

a brightness compensation circuit to receive desired pixel values and to produce compensated drive signals as a function of mirror phase by compensating for the varying brightness along the length as well as brightness variations resulting from the sinusoidal scanning.

9. The apparatus of claim 8 wherein the brightness compensation circuit includes a linear compensation component to compensate for the varying brightness along the length of the output coupler and a sinusoidal compensation component to compensate for the brightness variations resulting from the sinusoidal scanning.

10. The apparatus of claim 9 wherein the linear compensation component provides a gain greater than unity for at least one mirror phase.

11. The apparatus of claim 9 wherein the sinusoidal component provides a gain of less than unity for at least one mirror phase.

12. The apparatus of claim 9 wherein the linear compensation component provides a gain greater than unity for at least one mirror phase, and the brightness compensation circuit provides a gain of no more than unity for all mirror phases.

13. The apparatus of claim 8 wherein the brightness compensation component comprises a look up table.

14. The apparatus of claim 8 wherein contents of the lookup table are scaled to a maximum scale factor of one.

15. A method comprising:

determining a first brightness variation on a resonant axis of a scanning laser projector;

determining a second brightness variation along a length of a substrate guided relay output coupler; and

programming a brightness compensation circuit in the scanning laser projector to compensate for both the first and second brightness variations.

16. The method of claim 15 wherein determining a first brightness variation comprises measuring a light output of the scanning laser projector.

17. The method of claim 15 wherein determining a first brightness variation comprises calculating a brightness variation from a sinusoidal trajectory of the resonant axis.

18. The method of claim 15 wherein determining a second brightness variation comprises measuring light output from the output coupler.

19. The method of claim 15 wherein programming a brightness compensation circuit comprises populating a look up table.

20. The method of claim 15 wherein programming a brightness compensation circuit comprises combining compensation data for the first brightness variation with the compensation data for the second brightness variation and scaling the result for maximum laser output in the scanning laser projector.