CALIBRATION OF AN INTERFEROMETER FOR TESTING CYLINDRICAL SURFACES

A method of calibrating an interferometer for testing cylindrical surf aces is described. The calibration itself requires no cylindrical surf ace but only a plane mirror tested absolutely which is located at the focal line of the interferometer in several angular positions. From th e path differences measured at these positions, the interferometer err ors are calculated by solving a linear equation system. The reference surface for these errors can be fitted in the least-squares sense. The interferometer errors thus obtained are the result of the calibration ; they can then be subtracted from the path differences measured when testing cylindrical surfaces. The solution of the equation system also eliminates adjustment errors and compensates random measuring errors. The calibration is illustrated by computer simulations.