Optical system for the simultaneous measurement oftwo-dimensional straightness errors and the roll angle

摘要

A three-degree-of-freedom measurement system for the acquisition of the straightness and roll errors of a moving linearstage is described. The horizontal (Ax) and vertical (Ay) straightness errors are obtained by measuring the lateral dis-placement of a triple prism with a laser beam and position sensitive detectors. From two simultaneously performed verti-cal straightness measurements the roll angle (0z) can be calculated. The system consists of a cable-free reflector headand a detector head. The position sensitive detectors have been calibrated using a precision x,y-stage equipped with twoplane mirror interferometers. Different position sensitive detectors are compared with regard to position sensitivity, line-arity, null-shift stability and sensitivity to the intensity profile of the detected laser beam. In combination with an alreadyknown triple-beam plane mirror interferometer, additional information about the linear position (Az) and the pitch (0x)and yaw (0y) angle can be obtained from three parallel linear measurements. Thus all six-degree-of-freedom geometricerrors can be measured simultaneously.