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Proceedings Paper

Virtual image superposing comparator
Author(s): Michael E. Buchtel
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Paper Abstract

A virtual image superposing comparator is described which can be used to classify scratch widths, dig diameters and dig densities when verifying the surface quality of optical components. The magnified virtual image of an apparent defect is visually superposed anywhere on the viewing plane of a complete set of large scale standards in a common visual field. By positioning the virtual image of a defect next to or between any corresponding standard, it is possible to make direct, comparative measurements. The density of digs is verified by visually superposing the circular array of the standards over separated digs or groups of digs and summing the classes of digs appearing within the array. Unlike the current, full scale, scratch and dig surface quality standards, the large scale scratch and dig standards can be objectively calibrated by conventional methods and can be accurately and inexpensively reproduced. A derivation of infinity for the 'standard' eye; a coefficient for system scale factor and system magnifying power; an analysis of the effect of relative object spacing, tilt and contrast on comparative measurement; and two surface defect slide charts for expediting the scratch and dig area density computations specified in Military standard specifications are described.

Paper Details

Date Published: 28 May 1993
PDF: 22 pages
Proc. SPIE 1821, Industrial Applications of Optical Inspection, Metrology, and Sensing, (28 May 1993); doi: 10.1117/12.145572
Show Author Affiliations
Michael E. Buchtel, Techtel Corp. (United States)


Published in SPIE Proceedings Vol. 1821:
Industrial Applications of Optical Inspection, Metrology, and Sensing
Gordon M. Brown; Kevin G. Harding; H. Philip Stahl, Editor(s)

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