Optical mouse that automatically adapts to glass surfaces and method of using the same

1. A pointing device comprising:

an illumination system that illuminates a portion of a surface over which said pointing device travels with coherent light;

an imaging system comprising a first window for receiving light from said illuminated portion of said surface and transmitting that light to a first imaging array such that a speckle pattern is generated on said first imaging array and a second window comprising an imaging optical system for forming an image of part of said illuminated portion of said surface on a second imaging array; and

a controller that selects either the first imaging array without any imaging lens, or said second imaging array with an imaging lens, and compares the output of said selected imaging array at first and second times to determine a displacement indicative of the direction and distance said positioning device moved between said first and second times,

wherein said first window of said imaging system is situated on a path for said light between said illuminated portion of said surface and said first imaging array, said imaging system not including any imaging lens on said path to provide said path that lacks said imaging lens so that said speckle pattern is not destroyed.

2. The pointing device of claim 1 wherein said illumination system comprises a laser diode.

3. The pointing device of claim 2 wherein said laser diode is a VCSEL.

4. The pointing device of claim 1 wherein said controller determines the level of detail in said image formed on said second imaging array.

5. The pointing device of claim 4 wherein said controller selects said first imaging array if said determined level of detail is less than a predetermined value.

6. The pointing device of claim 4 wherein said level of detail is determined by counting objects in said image formed on said second imaging array.

7. The pointing device of claim 4 wherein said level of detail is determined by measuring spatial frequencies in said image formed on said second image sensor.

8. A method for determining a distance and direction through which a device moved between first and second times, said method comprising:

illuminating a portion of a surface over which said device travels with coherent light;

forming an image of a portion of said illuminated surface at said first and second times at a second imaging array using a lens;

forming a speckle pattern from light reflected by said illuminated portion of said surface at said first and second times at a first imaging array, including transmitting said light on a path without any imaging lens between said illuminated portion and said first imaging array so that said speckle pattern is not destroyed; and

comparing either said speckle pattern at said first and second times or said images at said first and second times to determine said distance and direction.

9. The method of claim 8 further comprising determining a level of detail in said image formed at one of said first and second times and selecting said speckle pattern or said image at said first and second times for said determination of said distance and direction depending on said determined level of detail.

10. The method of claim 9 wherein said level of detail is determined by counting objects in said image formed on said second imaging array.

11. The method of claim 9 wherein said level of detail is determined by measuring spatial frequencies in said image at said first or second times.