Patent ID: 8218134
Filing Date: 2012-07-10
Classification: G01D,G01L

Abstract:
1. A sensor for simultaneously sensing the angular position of a first rotatable member relative to a frame of reference and the angular position of a second rotatable member relative to the first rotatable member, the sensor comprising: a first disk having a first annular pattern which alternates between two different levels of optical transparency; a first coupling configured to couple the first disk to the first rotatable member; a second disk having a second annular pattern which alternates between two different levels of optical transparency and which has substantially the same radius as the first annular pattern, the first and second disk being configured such that the first and the second annular patterns may independently rotate about substantially the same axis while remaining substantially adjacent to one another; a second coupling configured to couple the second disk to the second rotatable member; an optical sensing array configured to provide signals indicative of an illumination pattern which is cast upon the optical sensing array; a lighting system configured to direct light toward the first and the second disks with an orientation that causes an illumination pattern to be cast upon the optical sensing array which corresponds to a composite of a portion of the first and the second annular patterns; and a signal processing system configured to: