| 摘要 |
PURPOSE:To simplify operation for measurement, by minimizing deviation from interference fringes by allowing a beam of reference light to deviate successively from a beam of light of a specimen article by a phase phi and adjusting a posture, etc. of the specimen article basing upon moire-image interference fringes of imaginary and actual beams of interference light. CONSTITUTION:A laser beam irradiates a aspherical mirror 16 and reference mirror 12 through an interferometer 3 and each reflected light is irradiated onto an image sensor monitor 11 for making interference fringes. Next, an arithmetic operation circuit 21 calculates imaginary interference fringes at the time when the specimen article is in the ideal situation and the imaginary reference beam is shifted from the imaginary article light by N-stage phi and store them. These imaginary interference fringes are read out successively 23 and the reference beam 7, in synchronization with above, is allowed to shift from the article light 6 by N-stage phi(x, y) [position on the position coordinates (X, Y) plane at center of the image] and sum, difference, product and quotient of actual and imaginary interference fringes by each beams of light obtained by each displacement are put into arithmetic operations 15. Basing upon these data, position, posture of the mirror 16 are adjusted 18, 19. Finally, arithmetic operation is conducted on phi(X, Y) and by utilizing a linear relation between phi(X, Y) and shape error, the shape error of the mirror 16 is obtained.
|
