Patent Number: 6,297,513

Title: Exposure servo for optical navigation over micro-textured surfaces

Abstract: Independent of any of several ways used to control exposure for the opticalsensor in an optical navigation device, changes in average level ofillumination are taken as indicative of changes in exposure. An acceptableexposure level for an optical navigation system is maintained by firstestablishing an initial operating level of exposure and subsequentlyadjusting it in proportion to changes in average illumination so long asimage contrast remains acceptable. Associated with the initial operatinglevel of exposure is an average level of illumination, which is thennoted, and about which is presumed to exist a range of satisfactoryoperating levels for exposure. The system proceeds to navigate from thecurrent reference frame using this level of exposure. When a new referenceframe is established the average level of illumination and the imagecontrast are checked. If the illumination is within the range of presumedsatisfactory operating levels for exposure and the image contrast iswithin acceptable limits, then no change is made to the parameter thatadjusts exposure and navigation proceeds from the new reference frame. Ifaverage level of illumination is outside the presumed satisfactory range,but the image contrast is still acceptable, a proportional correction ismade to the parameter controlling exposure, and navigation proceeds. Inall other cases the contrast is unacceptable, and the remedies are tovariously re-enter the process that establishes an initial operating levelfor exposure.

Inventors: Oliver; Thomas C (Windsor, CO), Hastings; Brian L. (Fort Collins, CO)

Assignee:

International Classification:

Expiration Date: 10/02/2013