Clutch-height adjustment in an optical tracking device

Architecture for managing clutch height in an optical navigational device such as a computer mouse. In one embodiment for a mouse, a feature can be molded into the bottom case that limits the clutch height by occluding the reflected light to the image sensor when the device is lifted from the tracking surface. Tracking is disabled when the clutch height threshold is exceeded, and re-enabled when the device is brought under the distance clutch height threshold. The device includes firmware controlled algorithm adjustments to one or more correlation parameters. When employing a D-shaped aperture, a threshold can be placed on the z-axis height tracking distance using dimensional characteristics of the shaped aperture, such as a knife-edge (the straight portion of the "D" shaped aperture), to impose a shadow across the image sensor. The aperture can be custom designed to occlude a portion of the emitted light from an LED.