A New Machine for Planarity Measurement of CCDs and Mosaics of CCDs

High quality CCD detectors are now being produced with 2048× 4096 square pixels, each 15 m on a side. Evenlarger detector areas are built with several CCDs mounted into amosaic. To be useful in an instrument the light must be in focuson all CCDs, requiring that all CCDs in a mosaic must typicallybe aligned within 30 micron of a flat plane. To achieve thisaccuracy in many cases the measurement and correction of the CCDalignment is necessary. One way allowing a surface measurement,even when the CCD is protected by a window, is to usetriangulation sensor. The principle of a triangulation sensor,its application and its implementation in a measuring machineare presented here.