Apparatus for controlling the position of a screen pointer that detects defective pixels

A method of identifying defective pixels in a pixel array of an optical pointing device, the method comprising:

• generating a plurality of digital images based on outputs of the pixel array;
• maintaining an adaptive history for each pixel location in the digital images;
• and
• identifying defective pixels in the pixel array by a digital logic and circuitry of the optical pointing device based on a comparison of the adaptive history and a threshold value,
• wherein the adaptive history comprises a smooth frame that is updated based on pixel values of each of the generated digital images, and that changes relatively slowly compared to changes between successive ones of the digital images, the smooth frame including pixel locations that correspond to pixel locations of each of the generated digital images, and
• wherein the smooth frame is calculated based on an equation, S=a*S+(1−a)*I, where “S” represents the smooth frame, “a” represents a constant value, and “I”represents a current one of the generated digital images.

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

• a light source for illuminating an imaging surface, thereby generating reflected images;
• and
• a navigation sensor for generating digital images based on the reflected images, detecting defective pixel locations in the digital images, and generating movement data based on the digital images that is indicative of relative motion between the imaging surface and the apparatus, the navigation sensor being configured to maintain an adaptive history for each pixel location in the digital images,
• wherein the adaptive history comprises a smooth frame that is updated based on pixel values of each of the generated digital images, and that changes relatively slowly compared to changes between successive ones of the digital images, the smooth frame including pixel locations that correspond to pixel locations of each of the generated digital images, and
• wherein the smooth frame is calculated based on an equation, S=a*S+(1−a)*I, where “S” represents the smooth frame, “a” represents a constant value, and “I”represents a current one of the generated digital images.

A method of identifying defective pixels in a pixel array of an optical pointing device, the method comprising:

• generating a plurality of digital images based on outputs of the pixel array;
• maintaining an adaptive history for each pixel location in the digital images;
• and
• identifying defective pixels in the pixel array by a digital logic and circuitry of the optical pointing device based on a comparison of the adaptive history and a threshold value,
• wherein the adaptive history comprises a smooth frame that is updated based on pixel values of each of the generated digital images, and that changes relatively slowly compared to changes between successive ones of the digital images, the smooth frame including pixel locations that correspond to pixel locations of each of the generated digital images, and
• wherein the identifying the defective pixels includes identifying a pixel location as being a defective pixel location if an absolute value of a difference between a value of a pixel at the location in the digital images and a value of a corresponding pixel in the smooth frame is less than a threshold value for N consecutive digital images, where N represents an integer greater than one.