| 摘要 |
A system for monitoring the optical figure of a surface utilizes an interferometer and a source of light to provide a measuring beam and a reference beam. Reflective spots are mounted respectively at a number of sample points on the surface and the measuring beam of light is focussed by optical means to provide an image field that includes the reflective spots which are oriented to reflect light from the measuring beam back to the optical means to form a conjugate image of the field of spots on light intensity detectors. The reference beam, whose path length is modulated, is combined with the light reflected from the spots to the detectors. There are separate detector elements for measuring the intensity of the combination of reference beam light and measuring beam light reflected from at least two different spots at one time. A shift in position of one sample point forward or back in relation to another sample point, which is a reference point, is thus monitored by comparing the phase relationship of the combination of the reference light with reflected light derived simultaneously from at least a pair of the sample points.
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