Patent ID: 8294672
Filing Date: 2012-10-23
Classification: G06F

Abstract:
1. An optical pointing device comprising: (a) a coherent light source for illuminating a surface portion with radiation; (b) a driver of the coherent light source for controlling a coherent light emission; (c) a photo-detector device responsive to radiation reflected from an illuminated surface portion; and (d) processing means for determining, based on the photo-detector device response, a measurement of relative motion between the optical pointing device and the illuminated surface portion; wherein the driver of the coherent light source is a fault-tolerant driver comprising redundant power control means of an output power of the coherent light emission, wherein the redundant power control means comprises two current units that are respectively defined by a current source and a current sink both limiting to a substantially constant current intensity through the coherent light source and both are respectively controlled by two separate current control paths, and wherein the current source and the current sink respectively have two independent current references in respective separate current control paths that respectively determine the substantially constant current intensity in the current source and the current sink, and wherein each of the two current units has a digital to analog converter in a respective current control path, and wherein the redundant power control means further comprises two different codes stored in a memory, wherein these two different codes are respectively provided to both separate current control paths, and wherein the redundant power control means also comprises a programming interface that determines, for each of the two different codes, an inverted code, wherein the programming interface provides two registers to each of both digital to analog converters that are respectively written with the code and inverted code associated with a corresponding current control path, wherein the two digital to analog converters each have an XOR circuitry to which the two registers are provided, and the XOR circuitry enables the corresponding digital to analog converter only when a perfect inversion occurs.