Patent ID: 9606458
Date: 2017-03-28
CPC Classifications: G01D,G03F

Claim:
1. A method for calibrating an encoder scale having an array of marks in a first direction, comprising: moving the encoder scale in the first direction relative to a first encoder-type sensor, a second encoder-type sensor and a third encoder-type sensor, wherein the first encoder-type sensor and the second encoder-type sensor are fixedly spaced in the first direction at a first distance relative to each other, wherein the second encoder-type sensor and the third encoder-type sensor are fixedly spaced in the first direction at a second distance relative to each other, wherein the first distance is larger than the second distance; obtaining, while moving, a first signal from the first encoder-type sensor, a second signal from the second encoder-type sensor and a third signal from the third encoder-type sensor, wherein the first signal is based on the array of marks and is representative of a position quantity of the encoder scale relative to the first encoder-type, wherein the second signal is based on the array of marks and is representative of a position quantity of the encoder scale relative to the second encoder-type sensor, wherein the third signal is based on the array of marks and is representative of a position quantity of the encoder scale relative to the third encoder-type sensor, creating, while taking into account the first distance and the second distance, a first position signal based on the first signal, a second position signal based on the second signal, and a third position signal based on the third signal; creating a comparison by comparing the first position signal, the second position signal and the third position signal with each other, and determining on the basis of the comparison a calibration map for the encoder scale.