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Abstract

A lithographic system, having a stepper and exposure station built on a block of granite attached to the ground using isolation legs, includes a servo control system for providing signals a motor associated with the stepper to control the movement of the stepper. The control system includes means to calculate a filter formula used to generate the control signals, which formula is calculated in response to the initial velocity, the movement of the stepper and a certain time between discrete movements, so that a minimum amount of energy is utilized. The filter formula requires that the difference in the velocity of the base and the stepper be zero at the time the stepper reaches the final position. Where time is short, both the base and the stepper initially move with the same velocity and end with the same velocity, and an array processor calculates the time varying filter formula.

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First Claim