Patent ID: 7622707

Claim:
A polaroid encoder system for detecting movement, said system comprising: a movable polarizing code element comprising a first concentric code, a second concentric code and a set of quadrants, the first and second concentric codes in contact with one another over one of the four quadrants of said movable polarizing code element; a detector module to detect an amplitude based on how much illumination passes through a first portion of said movable polarizing code element, said detector module comprising: a first illumination detector covered with a first static polarizing filter that is oriented in a first direction; a second illumination detector covered with a second static polarizing filter that is oriented in a second direction; a first determination module to identify a quadrant of said movable polarizing code element based on how much illumination passes through a second portion of said movable polarizing code element, the first determination module responsive to a single illumination source that emits light that is directed at and unaltered before encountering the movable polarizing code element and thereafter unaltered before encountering a third illumination detector; and a second determination module coupled to receive said amplitude and said quadrant and configured to determine an angular position of said movable polarizing code element using said amplitude and said quadrant.