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Noncontact Interferometric Technique for Measuring Flatness and Parallelism of Parts

IP.com Disclosure Number: IPCOM000088302D
Original Publication Date: 1977-May-01
Included in the Prior Art Database: 2005-Mar-04
Document File: 2 page(s) / 23K

Publishing Venue

IBM

Related People

Styles, BW: AUTHOR

Abstract

At present, flatness and parallelism of machined parts are measured using mechanical means, such as a stylus, or by attaching optical flats to the part and observing the interferometric light fringes. With the contact, the finely finished surfaces under measurement can be damaged.

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Noncontact Interferometric Technique for Measuring Flatness and Parallelism of Parts

At present, flatness and parallelism of machined parts are measured using mechanical means, such as a stylus, or by attaching optical flats to the part and observing the interferometric light fringes. With the contact, the finely finished surfaces under measurement can be damaged.

The figure shows a noncontact interferometric technique for measuring flatness and parallelism of planar parts. The part 10 to be measured is held in a fixture (not shown) between two adjustable gimbeled optical flats. Both optical flats are held away from the part, eliminating any contact. The optical flat #1 is adjusted so that it is parallel to one face 11 of the part 10. This is done by minimizing fringe lines on the image of the part in the usual well-known manner. The surface 11 of the part can then be observed and measured for flatness, as desired. The optical flat #2 is adjusted so that it is parallel to the opposite face 12 of the part 10 using the same technique as above. The second face 12 of the part can likewise be observed and measured for flatness.

The part 10 is then removed from between the optical flats. The fringe lines between the optical flats #1 and #2 are then used to determine the degree of parallelism between the two faces 11 and 12 of the part 10. A grid can be substituted for the part 10 and the parallelism measured directly by counting the light bands within the grid.

The figure shows a highly exaggerated nonparallel part 10 and the position of the optical flats #1 and #2 after the flats have been adjusted. An alternate method of...