Laser Autocollimator for Measurement of Multi-axis Tilt Motion

Abstract

Precision stages used in nanomanufacturing, including linear stages and rotary stages, have multi-axis tilt error motions. For a linear stage, the tilt error motions are referred to as the pitch, yaw and roll error motions, which cause unexpected Abbe errors [1, 2]. It is necessary to measure the tilt error motions by using angle sensors for evaluation and compensation of Abbe errors. Conventionally, the measurement of pitch and yaw angles is carried out by an autocollimator using a filament lamp as the light source and a CCD image sensor as the light position detector. As described in Chapter 1, conventional autocollimators, which are large in size and slow in measurement speed, are not suited for dynamic measurement of stage tilt error motions. In addition, the conventional autocollimator cannot detect the roll error motion, which is defined as the angular displacement about the normal axis of the target plane reflector, because no light spot displacement can be generated on the light position detector with respect to the roll error motion.