Method of controlling a segmented flash system
Systems, methods and devices are descried. A method of controlling a segmented flash having a plurality of flash segments each arranged to illuminate a portion of the scene includes determining an amount of light for illuminating each portion of the scene, measuring forward voltages of each of the flash segments, and adjusting a brightness of each of the flash segments to the determined amount of light for illuminating each portion of the scene. The adjusting is performed by at least one of adjusting a magnitude of a drive current to each of the flash segments, adjusting a duty cycle of the drive current to each of the flash segments, or scheduling a dummy flash, based at least in part on the measured forward voltages.
1. A method of controlling a segmented flash having a plurality of flash segments each arranged to illuminate a portion of a scene, the method comprising:
determining an amount of light for illuminating each portion of the scene;
measuring forward voltages of each of the plurality of flash segments; and
adjusting a brightness of each of the plurality of flash segments to the determined amount of light for illuminating each portion of the scene by at least one of adjusting a magnitude of a drive current to each one of the plurality of flash segments, adjusting a duty cycle of the drive current to each of the plurality of flash segments, or scheduling a dummy flash, based at least in part on the measured forward voltages.
2. The method according to claim 1 , wherein the measuring the forward voltages of each of the plurality of flash segments is performed under identical low constant current conditions.
3. The method according to claim 1 , wherein the adjusting the brightness of each of the plurality of flash segments comprises computing an adjusted drive current for each of the plurality of flash segments based at least in part on the measured forward voltages of each of the plurality of flash segments.
4. The method according to claim 1 , wherein the adjusting the brightness of each of the plurality of flash segments comprises adjusting the duty cycle of the drive current to each individual one of the plurality of flash segments.
5. The method according to claim 1 , wherein the adjusting the brightness of each of the plurality of flash segments comprises scheduling a dummy flash event.
6. The method according to claim 5 , further comprising:
determining a drive current distribution for the plurality of flash segments in a preceding flash event; and
applying a complement of the drive current distribution for the dummy flash event.
7. The method according to claim 1 , further comprising:
detecting a faulty flash segment of the plurality of flash segments based on the measured forward voltages; and
adjusting the brightness of remaining flash segments of the plurality of flash segment to achieve an illumination profile for the segmented flash ( 10 ).
8. The method according to claim 1 , wherein the measuring the forward voltages of each of the plurality of flash segments comprises measuring analog voltages of each of the plurality of flash segments, and the method further comprises converting the measured analog voltages to digital values.
9. The method according to claim 1 , wherein the determining the amount of light for illuminating each portion of the scene comprises providing one of a depth map or a three-dimensional (3D) profile of the scene.
10. A segmented flash system comprising:
a segmented flash comprising a plurality of flash segments, each of the plurality of flash segments having a location corresponding to a portion of a scene; and
a flash driver comprising:
an analog-to-digital converter,
a multiplexer that connects each of the plurality of flash segments to the analog-to-digital converter to provide analog measurements of a forward voltage of each of the plurality of flash segments to the analog-to-digital converter,
a number of registers, coupled to the analog-to-digital converter, that store digital values, corresponding to the analog measurements of the forward voltage of each of the plurality of flash segments,
a processor configured to determine at least one of an amplitude and a timing of a flash segment drive current based at least on the digital values stored in the registers, and
a state machine configured to control at least the multiplexer and the analog-to-digital converter to measure the forward voltage of each of the plurality of flash segments and store the digital values in the registers after a flash event.
11. The segmented flash system according to claim 10 , further comprising a depth map module configured to determine a relative amount of light to illuminate each portion of the scene.
12. The segmented flash system according to claim 10 , wherein each of the plurality of flash segments comprises a plurality of light sources.
13. The segmented flash system according to claim 12 , wherein each of the plurality of light sources of each of the plurality of flash segments have different spectra.
14. A device comprising:
an image sensor; and
a segmented flash system comprising:
a plurality of flash segments, each of the plurality of flash segments having a location corresponding to a portion of a scene, and
a flash driver comprising:
an analog-to-digital converter,
a multiplexer that connects each of the plurality of flash segments to the analog-to-digital converter to provides analog measurements of a forward voltage of each of the plurality of flash segments to the analog-to-digital converter,
a number of registers, coupled to the analog-to-digital converter, that store digital values, corresponding to the analog measurements of the forward voltage of each of the plurality of flash segments,
a processor configured to determine at least one of an amplitude and a timing of a flash segment drive current at least on the digital values stored in the registers, and
a state machine configured to control at least the multiplexer and the analog-to-digital converter to measure the forward voltage of each of the plurality of flash segments and store the digital values in the registers after a flash event.
15. The device according to claim 14 , wherein the device is one of a mobile phone, a tablet computer, or a camera.
16. The device according to claim 14 , wherein the segmented flash system further comprises a depth map module configured to determine a relative amount of light to illuminate each portion of the scene.
17. The device according to claim 14 , wherein each of the plurality of flash segments comprises a plurality of light sources.
18. The device according to claim 17 , wherein each of the plurality of light sources of each of the plurality of flash segments have different spectra.
19. The device according to claim 14 , wherein each of the plurality of flash segments comprises a single light source.
20. The segmented flash system according to claim 10 , wherein each of the plurality of flash segments comprises a single light source.