Light source control in optical pointing device

1. An optical pointing device, comprising:

a light source driver configured to provide a pulsed drive current;

a light source operably connected to the light source driver and configured to respond to the pulsed drive current by providing a sequence of light pulses to illuminate an imaging surface and thereby generate a corresponding sequence of images reflected from the imaging surface;

a photodetector array configured to sense the image sequence as a corresponding sequence of analog signal arrays;

an analog-to-digital (A/D) converter operably connected to the photodetector array and configured to convert the analog signal array sequence into a corresponding arrays of digital values;

a navigation processor operably connected to the A/D converter and the light source driver, the processor being configured to store, in a memory, individual frames corresponding to the digital values and the sequence of images corresponding thereto, each frame comprising an array of pixel values, the navigation processor further being configured to process each frame at a frame rate and determine an image quality value corresponding to each frame based on at least one of a measured average pixel value of the frame, a measured minimum pixel value of the frame, a measured pixel ratio value of the frame, and a measured maximum pixel value of the frame, the navigation processor further being configured to control a duty cycle of the light source driver and at least one of a pulse amplitude and a pulse width of the pulsed drive current thereof on the basis of the image quality value determined for each frame, the duty cycle being synchronized with the frame rate.

2. The optical pointing device of claim 1 , wherein the light source comprises a laser.

3. The optical pointing device of claim 1 , wherein the light source comprises a vertical cavity surface emitting laser (VCSEL).

4. The optical pointing device of claim 1 , wherein the light source comprises a broadband light source configured to provide broadband light, and a bandpass filter configured to filter the broadband light to provide the at least partially coherent light.

5. The optical pointing device of claim 1 , wherein the navigation processor is further configured to determine whether an individual frame stored in the memory thereof represent a good image or a bad image based on the image quality value corresponding to such frame.

6. The optical pointing device of claim 1 , wherein the navigation processor is configured to reduce the drive current when the photodetector array is saturated by reflected images.

7. The optical pointing device of claim 1 , wherein the navigation processor is configured to calibrate the drive current after a reset condition occurs.

8. The optical pointing device of claim 7 , wherein the navigation processor is configured to cycle through predetermined drive current values stored in the memory thereof until one of the drive current values results in a suitable quality image being produced.

9. The optical pointing device of claim 8 , wherein the light source is at least partially coherent.

10. The optical pointing device of claim 1 , wherein the navigation processor is configured to calibrate the drive current after a rest period of a predetermined period of time has elapsed.

11. The optical pointing device of claim 10 , wherein the rest period is selected to be sufficiently long to avoid disrupting operation of the optical pointing device when the device is being employed by a user.

12. The optical pointing device of claim 10 , wherein the navigation processor is configured to cycle through a plurality of predetermined drive current values stored in the memory thereof until one of the drive current values produces a suitable quality image.

13. The optical pointing device of claim 12 wherein the navigation processor is configured to set the drive current value to the drive current value corresponding to the end of the rest period and the beginning of the calibration if none of the predetermined drive current values produces a suitable quality image.

14. The optical pointing device of claim 10 , wherein the navigation processor is configured to cycle through a selected number of drive current values until one of the drive current values produces a suitable quality image, wherein the selected number is less than all the predetermined drive current values stored in the memory.

15. The optical pointing device of claim 14 , wherein the navigation processor is configured to set the drive current value to the drive current value corresponding to the end of the rest period and the beginning of the calibration if none of the drive current values produces a suitable quality image.

16. The optical pointing device of claim 1 , wherein the navigation processor includes at least one of the light source driver and a drive current controller.

17. The optical pointing device of claim 1 wherein at least one of the light source driver and a drive current controller is external to the navigation processor.

18. A method of operating an optical pointing device comprising a light source driver configured to provide a pulsed drive current, a light source operably connected to the light source driver and configured to respond to the pulsed drive current by providing a sequence of light pulses to illuminate an imaging surface and thereby generate a corresponding sequence of images reflected from the imaging surface, a photodetector array configured to sense the image sequence as a corresponding sequence of analog signal arrays, an analog-to-digital (A/D) converter operably connected to the photodetector array and configured to convert the sequence of analog signal arrays into a corresponding sequence of digital array values, a navigation processor operably connected to the A/D converter and the light source driver, the processor being configured to store, in a memory, individual frames corresponding to the digital array values and the sequence of images corresponding thereto, each frame comprising an array of pixel values, the navigation processor further being configured to process each frame at a frame rate and determine an image quality value corresponding to each frame based on at least one of a measured average pixel value of the frame, a measured minimum pixel value of the frame, a measured pixel ratio value of the frame, and a measured maximum pixel value of the frame, the navigation processor further being configured to control a duty cycle of the light source driver and at least one of a pulse amplitude and a pulse width of the pulsed drive current thereof on the basis of the image quality value determined for each frame, the duty cycle being synchronized with the frame rate, the method comprising:

providing the pulsed drive current to the light source;

illuminating the imaging surface with the sequence of light pulses;

sensing the sequence of images reflected from the imaging surface with the photodetector array and generating the corresponding sequence of arrays of analog signals;

converting the sequence of arrays of analog signals into the corresponding sequence of digital value arrays;

storing, in the memory of the navigation processor, the individual frames corresponding to the digital array values;

processing the pixel values of the individual frames to determine an image quality value for each frame;

controlling the duty cycle of the light source driver on the basis of the image quality values determined for each frame; and

synchronizing the duty cycle with the frame rate.

19. The method of claim 18 , further comprising calibrating the pulsed drive current on the basis of the image quality values.

20. The method of claim 18 , further comprising the light source providing at least partially coherent light.

21. The method of claim 18 , further comprising providing a laser as the pulsed light source.

22. The method of claim 18 , further comprising providing a vertical cavity surface emitting laser (VCSEL) as the pulsed light source.

23. The method of claim 18 , further comprising bandpass filtering the pulsed light source.