Patent ID: 7432496

Claim:
A method for writing or calibrating the scale of a scale-based position encoder mounted on an end-use host system, using an image correlation displacement sensor, the method comprising: providing a scale-based position encoder that comprises at least a scale and an encoder readhead that provides displacement measurement signals that depend on the relative position between the encoder readhead and marks on the scale; installing the scale of the scale-based position encoder where it will be used to provide ongoing position measurements related to the relative displacement between two members of the end-use host system along a measuring axis direction; mounting an image correlation displacement sensor proximate to a mounting position where the encoder readhead of the scale-based position encoder will be used to provide the ongoing position measurements; moving the image correlation displacement sensor relative to the scale along the measuring axis direction by providing relative displacement between the two members of the host system; and using the image correlation displacement sensor to provide displacement measurement information corresponding to the relative displacement, using the displacement measurement information provided by the image correlation displacement sensor to govern at least one of a scale writing process and a scale calibration process for the scale-based position encoder, such that the displacement measurement information provided by the image correlation displacement sensor at least partially governs the values of respective ongoing position measurements that are determined based on the displacement measurement signals provided by the encoder readhead of the scale-based position encoder at respective positions along the measuring axis.