Method and device for noncontacting self-referencing measurement

Details Method and device for noncontacting self-referencing measurement Method and device for noncontacting self-referencing measurement

1990-02-08

1991-11-26

Evans, F. L.

Optics: measuring and testing

By polarized light examination

With light attenuation

G01B 1124

Patent

active

050678175

ABSTRACT:
Measurement of curvature and profile of a reflective test surface by simultaneous measurement of slope at two closely spaced points on the test surface. A pair of parallel, nearly collimated light beams, which are slightly displaced relative to each other and of opposite linear polarization, and which intersect the test surface are reflected by the test surface, separated by a polarizing beam splitter and focused onto individual position sensitive detectors, which sense the slopes of the test surface at the points where it is intersected by the beams. The difference between the measured slopes is proportional to the local curvature. The device can be scanned along the surface to give a profile of measured curvature values, which are twice integrated to give the surface profile, although measurement at a single point without any such processing yields the test piece curvature. The device is reconfigured to test surfaces with different curvatures by virtue of one of the detectors being movable during initial alignment, and by virtue of a steering mirror and associated servo control system which maintain an essentially constant angle of incidence on the test surface.

REFERENCES:
patent: 2446628 (1987-09-01), Brown
patent: 4929846 (1988-10-01), Mansour
Takacs et al., "Surface Topography Measurements Over One Meter to Ten Micrometer Spacial Period Bandwidth", SPIE, vol. 1164, Surface Characterization and Testing 11, 1989, pp. 203-211.
Von Bieren, "Pencil Beam Interferometer for Aspherical Optical Surfaces", SPIE, vol. 343, Laser Diagnostics, 1982, pp. 101-108.

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