Title: Scanning differential photoelectric autocollimator

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Claims: What is claimed is:

1. A device for measuring the light beam deviating properties of a test object which comprises 1) a source of light energy, which produces a narrow light beam 2) means for rotationally scanning said beam 3) means for collimating said rotationally scanned beam to produce a collimated, scanning beam 4) means for passing said collimated, scanning beam over a partially reflective, partially transmissive reference object with a reference surface having light beam deviating properties essentially similar to those of said test object, to produce a reflected reference beam, and a transmitted measurement beam which probes said test object, 5) means for collecting said transmitted measurement beam after it has probed said test object to provide an autoreflected, collected measurement beam 6) means for focusing said reflected reference beam and said autoreflected, collected measurement beam onto separate photoelectric position sensors and 7) means for comparing the outputs of said position sensors to obtain information with respect to the differences in the light beam deviating properties of the test object and the reference surface.

2. The device of claim 1, in which the source of light energy is a gas laser.

3. The device of claim 1, in which the collimated, scanning beam moves in a raster pattern.

4. The device of claim 1, in which the test article is reflective and the means 7) for comparing the outputs of said two position sensors includes 8) means for producing outputs indicative of the two first spatial derivatives of the surface profile of the test article relative to the reference surface 9) means for processing said outputs to yield the surface profiles of said test article and 10) means for processing said outputs to yield said surface profiles independent of the tilt of either said test article or said reference surface.

5. The device of claim 1, in which the test article is transparent, and the device includes a master reflecting surface which is so placed and whose surface contour is so related to the light beam deviating properties of the test object, that said transmitted measurement beam, after it has probed the test object, is autoreflected for double-pass transmission through said test object.

6. The device of claim 1, in which said reference article is slightly tilted with respect to said collimated, scanning light beam.

Other info:

Inventors: Hunter, George C. (Middletown, CT, US)
Zanoni, Carl A. (Middletown, CT, US)

Application Number: 565525
Filing Date: 1975-04-07
Publication_date: 1976-08-31
Assignee: Zygo Corporation (Middlefield, CT)
Primary Class(es): 356/394 356/124, 356/243.1, 356/369, 356/448, 356/613
Other Classes:
US Patent Ref:

3761179	Sep, 1973	Plummer et al.	356/120.
3885875	May, 1975	Rosenfeld et al.	356/167.

Other Refs:
Primary Examiner: McGraw, Vincent P.
Assistant Examiner:
Attorney: Zucker; Milton