Patent ID: 7557795

Claim:
An input device, comprising: a member configured to rotate about a first axis in response to user manipulation of a physical element of the input device; a first laser positioned to shine a first beam onto a surface of the member and to receive a reflection of at least a portion of the first beam from the surface, the first laser being positioned so that portions of the surface struck by the first beam have a velocity component parallel to the first beam as the member rotates; a first photosensitive element providing an output signal in response to illumination, the first photosensitive element positioned to measure intensity of the first beam; a divider configured to reduce a frequency of the first photosensitive element output signal; a modulator configured to modulate bias current of the first laser in response to a signal from the divider; a first controller receiving a signal based on the first photosensitive element output signal, wherein the first controller is configured to determine rotational movement of the member about the first axis in two directions based on fluctuations in the first beam intensity resulting from the received reflection, and wherein the first controller is configured to determine the direction in which the member is rotating based on fluctuations in the first beam intensity resulting from the received reflection; and a second controller configured to convert data from the determined rotational movement into data for transmission from the input device.