Patent ID: 7710553
Filing Date: 2010-05-04
Classification: G01D

Abstract:
1. An apparatus comprising: a sensor head wherein the detector consists of a linear imaging array and including an illumination source that illuminates a reference surface including a coded sequence of reference markings, and a detector that generates an output indicative of the coded sequence of reference markings from light reflected from the reference surface, wherein the reference surface comprises a cylindrical edge surface or a linear strip surface, wherein the cylindrical edge surface is located on a code wheel or rotor of an object whose shaft angle position or motion is to be measured, or wherein the linear strip surface is located on a planar surface of an object wherein linear position or relative motion with respect to said object is to be measured; and wherein the electronics module processes the received signal to determine a width and a centroid location of individual reference markings in the coded sequence of reference markings, and derives angle or position information based on the widths and centroid locations of the individual reference markings, and corrects for misalignment, lens distortion, and other errors, using the linear imaging array's known or measured properties combined with readings of an external calibrated reference standard, and calibrates the position of individual code markings reproduced on the coded reference to compensate for errors in code production.