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File:Optical flat interference fringes.jpg

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Summary

Description
English: Photos of two glass optical flats testing the flatness of surfaces, showing the different patterns of interference fringes. The flats are resting with their bottom surfaces in contact with the surface to be tested (toolmaker's flats) and they are illuminated by a monochromatic light source. When there is a slight gap between the two surfaces, the light waves reflected from both surfaces interfere, resulting in a pattern of bright and dark bands called an interference pattern. The surface in the left photo is nearly flat, indicated by a pattern of almost straight parallel interference fringes at equal intervals. The surface in the right photo is uneven, resulting in a pattern of curved fringes. Each pair of adjacent fringes represents a difference in surface elevation of half a wavelength of the light used, so differences in elevation can be measured by counting the fringes. The flatness of surfaces can be measured to millionths of an inch by this method.
Date
Source Downloaded 2011-03-04 from Franklin D. Jones "How precision gage-blocks are made" in Machinery, Vol. 26, April, 1920, The Industrial Press, New York, p. 706, fig. 21 & 22 on Google Books
Author unknown, probably Franklin D. Jones
Permission
(Reusing this file)
Public domain in USA - published prior to 1923 in USA

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Public domain
Public domain
This media file is in the public domain in the United States. This applies to U.S. works where the copyright has expired, often because its first publication occurred prior to January 1, 1929, and if not then due to lack of notice or renewal. See this page for further explanation.

United States
United States
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current16:19, 6 March 2011Thumbnail for version as of 16:19, 6 March 2011846 × 354 (63 KB)Chetvorno{{Information |Description={{en|Photos of two glass optical flats testing the flatness of surfaces, showing the different patterns of interference fringes. The flats are resting with their bottom surfaces in contact with toolmaker's flats. When there is

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