Traceability in the calibration of low cost opto-electronic sensors for measuring 2D displacement

The utilization of 2D non-contact sensors for measuring displacements is a more and more used alternative for the development of several degrees of freedom precision systems. Inside this group of sensors, optoelectronic devices such as CCDs (Charge-Coupled Devices) or PSDs (Position Sensitive Detectors) are included. PSDs are an adequate option when the economical cost needs to be decreased. Nevertheless, characterizing and adequately correcting the error of those sensors is needed in order to achieve the expected accuracy. A possible technique to carry out this kind of calibration is based on the use of a 2D-Cross-Grid Encoder as a reference. However, the calibration of those Cross-Grid Encoders itself is being done by the manufacturers in a separate way in each of the two axes by comparing the displacement in each of them to a laser interferometer and only along their central lines. Therefore, there are a big number of errors that cannot be determined by that traditional calibration. In this paper a 2D calibration technique is proposed in order to keep the traceability in case of using these systems as reference for the calibration of others, like PSDs. © 2009 American Institute of Physics.