Patent ID: 7808481

Claim:
An optical pointing device adapted to be disposed on a working surface, comprising: a casing having a side, and a first light transmissible portion that is provided on said side of said casing and that faces the working surface; a light source mounted in said casing, and adapted to emit coherent light that is directed through said first light transmissible portion of said casing and that is subsequently reflected by the working surface back into said casing through said first light transmissible portion; a light sensor mounted in said casing, and adapted to detect the light reflected by the working surface, wherein said light sensor defines a geometric center; a processing unit coupled to said light sensor, and operable so as to determine displacement of said casing relative to the working surface based on the reflected light detected by said light sensor when said casing is moved along the working surface; and an obstructing member disposed in said casing, and capable of preventing said light sensor from detecting the light reflected by the working surface when said casing is moved beyond a predetermined distance away from the working surface, wherein said obstructing member is formed with a second light transmissible portion which has a center, and wherein an offset is provided between said center of said second light-transmissible portion and said geometric center of said light sensor, whereby when said casing is moved beyond a predetermined distance away from the working surface, said offset prevents the light emitted from the light source and reflected by the working surface from reaching said light sensor.