Evaluation of the Linearity Error of PSDs Based on the Self-Calibration Method.

A self-calibration system of a pair of position sensing detectors (PSDs) has been developed. Without using any special standard, the linearity errors of a pair of PSDs can be calibrated intrinsically within their performance limitations. The changes of linearity errors of the PSDs according to spot sizes have been clarified by using the developed experimental setup. The difference between the linearity errors for different spot sizes is larger than the positioning error given in specifications by manufacturers.