Apparatus for controlling the position of a screen pointer with low sensitivity to particle contamination

1. An apparatus for controlling the position of a screen pointer, the apparatus comprising:

an at least partially coherent light source for illuminating an imaging surface, thereby generating reflected images; and

a navigation sensor for generating digital images based on the reflected images, performing a movement computation based on the digital images, and generating movement data based on the movement computation that is indicative of relative motion between the imaging surface and the apparatus, the navigation sensor being configured to sense the reflected images from the imaging surface and perform analog-to-digital conversion on the sensed reflected images to generate the digital images,

wherein the movement computation comprises summing only pixels values from a first one of the digital images, thereby generating a first plurality of sums, and summing only pixel values from a second one of the digital images, thereby generating a second plurality of sums.

2. The apparatus of claim 1 , wherein the movement computation further comprises correlating the first plurality of sums with the second plurality of sums.

3. The apparatus of claim 1 , wherein each of the digital images includes a plurality of rows of pixels and a plurality of columns of pixels, and wherein the movement computation comprises summing pixel values in each row of the digital images, thereby generating a plurality of row sums for each digital image, and summing pixel values in each column of the digital images, thereby generating a plurality of columns sums for each digital image.

4. The apparatus of claim 3 , wherein the movement computation further comprises correlating the plurality of rows sums from a first one of the digital images with the plurality of row sums from a second one of the digital images, and correlating the plurality of column sums from the first one of the digital images with the plurality of column sums from the second one of the digital images.

5. A method of generating movement data with an optical pointing device, the method comprising:

illuminating an imaging surface with an at least partially coherent light source, thereby generating reflected images;

sensing reflected images from the imaging surface;

performing analog-to-digital conversion on the sensed reflected images to generate digital images;

performing a movement computation based on the digital images; and

generating movement data based on the movement computation that is indicative of relative motion between the imaging surface and the optical pointing device,

wherein the movement computation comprises summing only pixels values from a first one of the digital images, thereby generating a first plurality of sums, and summing only pixel values from a second one of the digital images, thereby generating a second plurality of sums.

6. The method of claim 5 , wherein the movement computation further comprises correlating the first plurality of sums with the second plurality of sums.

7. The method of claim 5 , wherein each of the digital images includes a plurality of rows of pixels and a plurality of columns of pixels, and wherein the movement computation comprises summing pixel values in each row of the digital images, thereby generating a plurality of row sums for each digital image, and summing pixel values in each column of the digital images, thereby generating a plurality of columns sums for each digital image.

8. The method of claim 7 , wherein the movement computation further comprises correlating the plurality of rows sums from a first one of the digital images with the plurality of row sums from a second one of the digital images, and correlating the plurality of column sums from the first one of the digital images with the plurality of column sums from the second one of the digital images.

9. A navigation sensor comprising:

a sensor array configured to sense reflected images from an imaging surface produced by an at least partially coherent light source;

an analog to digital converter for generating digital images based on outputs of the sensor array; and

a processor for generating movement data based on the digital images, wherein the movement data is generated based on a movement computation,

wherein the movement computation comprises summing only pixels values from a first one of the digital images, thereby generating a first plurality of sums, and summing only pixel values from a second one of the digital images, thereby generating a second plurality of sums.

10. The navigation sensor of claim 9 , wherein the movement computation further comprises correlating the first plurality of sums with the second plurality of sums.

11. The navigation sensor of claim 9 , wherein each of the digital images includes a plurality of rows of pixels and a plurality of columns of pixels, and wherein the movement computation comprises summing pixel values in each row of the digital images, thereby generating a plurality of row sums for each digital image, and summing pixel values in each column of the digital images, thereby generating a plurality of columns sums for each digital image.

12. The navigation sensor of claim 11 , wherein the movement computation further comprises correlating the plurality of rows sums from a first one of the digital images with the plurality of row sums from a second one of the digital images, and correlating the plurality of column sums from the first one of the digital images with the plurality of column sums from the second one of the digital images.