Dithered power matching of laser light sources in a display device
View Patent ↗A technique for managing image quality in a laser-based imaging system is provided. Laser light sources are organized into two or more groups, and optical output power of a light source group containing an under-performing laser is matched to that of the under-performing laser, while the optical output power of the light sources in the remaining groups is not. The output of the laser light sources in each group is interleaved with the output of the laser light sources in the other groups, so that perceptual uniformity of a displayed image is maintained when the display is viewed from an appropriate viewing distance.
1. A method for managing image quality in a laser-based imaging system, the method comprising:
organizing a plurality of lasers into two or more subsets of lasers;
within a first subset of lasers, identifying a first laser having an output level that is lower than any output level associated with any other laser in the first subset of lasers;
for each of the other lasers in the first subset of lasers, adjusting the output level associated with the other laser to be substantially equal to the output level associated with the first laser;
within a second subset of lasers, adjusting the output level associated with each laser in the second subset of lasers to be substantially equal to a second output level; and
causing the outputs of the lasers within the first subset of lasers to be interleaved with the outputs of the lasers within the second subset of lasers to display an image on a display surface.
2. The method of claim 1 , wherein the first subset of lasers is configured to illuminate a first plurality of regions on the display surface, and the second subset of lasers is configured to illuminate a second plurality of regions on the display surface.
3. The method of claim 2 , wherein regions in the first plurality of regions and regions in the second plurality of regions are disposed on the screen in an alternating fashion relative to one another.
4. The method of claim 2 , wherein regions in the first plurality of regions have a width of at least one pixel element.
5. The method of claim 2 , wherein regions in the first plurality of regions and regions in the second plurality of regions form a pattern of alternating stripes on the display surface.
6. The method of claim 1 , wherein the output level associated with the first laser is less than a reference output level, and the second output level is greater than the reference output level.
7. The method of claim 6 , wherein the second output level is selected such that the average of the output level associated with the first laser and the second output level is substantially equal to the reference output level.
8. The method of claim 1 , further comprising computing a number of subsets of lasers comprising the two or more subsets of lasers based on a viewing distance from the display surface, a width of a region on the display surface illuminated by a single laser in the plurality of lasers, a contrast threshold function of the human eye, and a difference between the output level associated with the first laser and the second output level.
9. The method of claim 8 , further comprising:
calculating a threshold contrast value for the computed number of subsets of lasers plus one additional subset of lasers;
calculating a threshold output difference between the output level associated with the first laser and the second output level; and
determining that the number of subsets of lasers comprising the two or more subsets of lasers can be increased without causing a substantial contrast between the regions on the display surface illuminated by the lasers in the plurality of laser; and
setting the number of subsets of lasers comprising the two or more subsets of lasers to the computed number of subsets of lasers plus one additional subset of lasers.
10. The method of claim 9 , wherein the threshold contrast value is calculated as a function of the viewing distance from the display surface, the computed number of subsets of lasers plus one additional subset of lasers, and the width of a region on the display surface illuminated by a single laser in the plurality of lasers.
11. A non-transitory computer-readable storage medium comprising instructions to be executed by a computing device to cause the computing device to carry out the steps of:
organizing a plurality of lasers into two or more subsets of lasers;
within a first subset of lasers, identifying a first output level associated with a first laser, wherein the first output level is lower than any output level associated with any other laser in the first subset of lasers;
for each of the other lasers in the first subset of lasers, matching the output level associated with the first laser to the first output level;
within a second subset of lasers, matching the output level associated with each laser to a second output level; and
causing the outputs of the lasers within the first subset of lasers to interleave with the output of the lasers within the second subset of lasers in order to display the image on a display surface.
12. The non-transitory computer-readable storage medium of claim 11 , wherein the first subset of lasers is configured to illuminate a first plurality of regions on the display surface, and the second subset of lasers is configured to illuminate a second plurality of regions on the display surface.
13. The non-transitory computer-readable storage medium of claim 12 , wherein regions in the first plurality of regions and regions in the second plurality of regions are disposed on the screen in an alternating fashion relative to one another.
14. The non-transitory computer-readable storage medium of claim 12 , wherein regions in the first plurality of regions have a width of at least one pixel element.
15. The non-transitory computer-readable storage medium of claim 12 , wherein regions in the first plurality of regions and regions in the second plurality of regions form a pattern of alternating stripes on the display surface.
16. The non-transitory computer-readable storage medium of claim 11 , wherein the output level associated with the first laser is less than a reference output level, and the second output level is greater than the reference output level.
17. The non-transitory computer-readable storage medium of claim 16 , wherein the second output level is selected such that the average of the output level associated with the first laser and the second output level is substantially equal to the reference output level.
18. The non-transitory computer-readable storage medium of claim 11 , further comprising computing a number of subsets of lasers comprising the two or more subsets of lasers based on a viewing distance from the display surface, a width of a region on the display surface illuminated by a single laser in the plurality of lasers, a contrast threshold function of the human eye, and a difference between the output level associated with the first laser and the second output level.
19. The non-transitory computer-readable storage medium of claim 18 , further comprising:
calculating a threshold contrast value for the computed number of subsets of lasers plus one additional subset of lasers;
calculating a threshold output difference between the output level associated with the first laser and the second output level; and
determining that the number of subsets of lasers comprising the two or more subsets of lasers can be increased without causing a substantial contrast between the regions on the display surface illuminated by the lasers in the plurality of laser; and
setting the number of subsets of lasers comprising the two or more subsets of lasers to the computed number of subsets of lasers plus one additional subset of lasers.
20. The non-transitory computer-readable storage medium of claim 19 , wherein the threshold contrast value is calculated as a function of the viewing distance from the display surface, the computed number of subsets of lasers plus one additional subset of lasers, and the width of a region on the display surface illuminated by a single laser in the plurality of lasers.
21. A laser-based display system, comprising:
a display surface;
a plurality of lasers for producing light to form an image on the display surface; and
a processing unit configured to perform the steps of:
organizing the plurality of lasers into two or more subsets of lasers;
within a first subset of lasers, identifying a first laser having an output level that is lower than any output level associated with any other laser in the first subset of lasers;
for each of the other lasers in the first subset of lasers, adjusting the output level associated with the other laser to be substantially equal to the output level associated with the first laser;
within a second subset of lasers, adjusting the output level associated with each laser in the second subset of lasers to be substantially equal to a second output level; and
causing the outputs of the lasers within the first subset of lasers to be interleaved with the outputs of the lasers within the second subset of lasers to display an image on a display surface.
22. The display device of claim 21 , further comprising a memory unit configured to store instructions that, when executed by the processing unit, cause the processing unit to perform the steps of organizing, identifying, adjusting, and causing.
23. The display device of claim 21 , wherein the processing unit comprises a special purpose graphics unit, a graphics processing unit, an application specific integrated circuit, or a field-programmable gate array.