The development of totally transparent position sensors

We describe an improved version of COPS, a CCD based Optical Position Sensor, which can measure or monitor positions of attached elements with accuracies better than 0.05 mm at distances of tens of meters. The main application of this device is in the precision alignment and monitoring of radiation detectors in experimental high-energy physics. The improved sensor, named NUCOPS, has a set of four linear CCD arrays attached to the inside walls of a rigid square tube, and can be illuminated by a cross-hair laser coming from either direction. Like the old device, a NUCOPS can measure changes in its position to the laser lines with reproducibility better than 2 mum. It has been designed specifically for use in the alignment system of the Endcap Muon detectors for the CMS experiment at LHC.