Optical_flat_interference_fringes.jpg
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Summary
Description Optical flat interference fringes.jpg |
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.
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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 |
Licensing
Public domain Public domain false false |
This media file is in the
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publication
occurred prior to January 1, 1929, and if not then due to lack of notice or renewal. See
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for further explanation.
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