Shape measuring method

Details Shape measuring method Shape measuring method

2009-10-02

2010-10-05

Toatley, Jr., Gregory J (Department: 2877)

Optics: measuring and testing

By light interference

Having light beams of different frequencies

Reexamination Certificate

active

07808647

ABSTRACT:
A method for detecting shapes based on interferometric observation of an object surface subjected to narrow-band lighting. Movement of the interferometer (1) relative to the object surface (2) generates a measuring signal on a photo receiver, e.g., camera circuit (5), from which two extremely closely positioned signal frequencies (fo) and (fo+Δf) are extracted. The phase difference between the two signal components is used for determining the distance and/or the change in distance. The method has a large unambiguousness range, making it possible to have a large depth measurement range, and can be used for workpieces having offset areas on the surface, wherein the measurement is not disturbed along the edges and the offset areas. The method also allows examining strongly inclined surfaces having a steep inclination such that that traditional methods based on evaluating interference lines cannot be used because of a high density of the interference lines.

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Kenichi Hibino et al., “Simultaneous Measurement of Surface Shape and Variation in Optical Thickness of a Transparent Parallel Plate in Wavelength-Scanning Fizeau Interferometer”, Feb. 20, 2004, vol. 43, No. 6, Applied Optics.

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