公开(公告)号：US3572925A

公开(公告)日：1971-03-30

申请号：US3572925D

申请日：1967-10-18

Applicant: TEXAS INSTRUMENTS INC

Inventor： ABLES BILLY D ,  FORT CHARLES ,  JACKSON EDMUND D

IPC: G03B27/44 ,  G03F7/20 ,  G05B19/18

CPC classification number: G03F7/70275 ,  G03B27/44 ,  G03F7/70716 ,  G03F7/70775 ,  G03F7/70883 ,  G05B19/188

Abstract: A film support table is movable in the X and Y coordinate directions by X and Y drive systems. A laser interferometer and fringe counter detects movement of the table in the X and Y coordinate directions by fringe counts. A projection system simultaneously projects a plurality of images onto the film carried by the table after the table is moved to each of a plurality of predetermined exposure positions. A reference detector system detects when the table is at a zero reference position and resets the counters. A digital computer is programmed to compute the coordinate of each exposure position and then, based on the current barometric pressure, compute the number of fringe counts from the reference position to the first exposure position. The computer then operates the drive system in such a manner as to move the table to the exposure position by continuously computing the position and velocity of the table from the readings of the fringe counters. Then the table is maintained at the exposure position during the exposure period by continuously determining the position of the table from the fringe counters and operating the drive system to produce forces for correcting the positional error.