Method for calibrating a tilt inspection system and reference disk assembly for use therein

摘要

A method is provided for calibrating a tilt inspection system and a reference disk assembly for use therein wherein a mirror disk of the assembly is attached to a rotatable member of the system by a beveled washer so that the mirror disk rotates at a predetermined tilt angle with respect to an axis of rotation of the rotatable member. As the reference disk assembly is rotated by the tilt inspection system at a relatively slow and constant angular velocity, a beam of light is reflected off the mirror disk to a position sensitive detector (i.e., PSD) and subscribes a circle on the face of the PSD. The tilt inspection system samples the channels from the PSD throughout one revolution of the mirror disk. Calibration or reference data is calculated in the form of tilt transformations. Four basic steps are involved: 1) acquisition of PSD voltage data when the reference disk assembly is rotated within the tilt inspection system; 2) analysis of the data to determine location of a reference marker formed on the mirror disk; 3) fitting of the data to sine functions; and 4) computing the tilt transformations. This approach provides a simple, highly accurate, calibration procedure that minimizes chances for operator error and the affects of system noise.