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# Measurement of Small Inaccessible Surface

IP.com Disclosure Number: IPCOM000076337D
Original Publication Date: 1972-Feb-01
Included in the Prior Art Database: 2005-Feb-24
Document File: 2 page(s) / 25K

IBM

## Related People

Olbert, M: AUTHOR

## Abstract

In many small objects it is difficult to position normal measuring apparatus proximate to hard-to-get-at surfaces. This problem can be overcome with an optical measuring system. As illustrated, a light source 10 illuminates the surface 12 of object 11 after passing through medium 13. The incident rays are denoted 14. The reflected rays from surface 12 are refracted at the boundary 15 between 13 and medium 16 which is generally air. Since the size of the image changes depending upon the observing angle phi, a correction factor must be considered in determining the length of surface 12. The correction factor is determined by the equation f(n,phi) = [n/2/-sin/2/phi] 1/2 over sin phi cos phi.

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Measurement of Small Inaccessible Surface

In many small objects it is difficult to position normal measuring apparatus proximate to hard-to-get-at surfaces. This problem can be overcome with an optical measuring system. As illustrated, a light source 10 illuminates the surface 12 of object 11 after passing through medium 13. The incident rays are denoted
14. The reflected rays from surface 12 are refracted at the boundary 15 between 13 and medium 16 which is generally air. Since the size of the image changes depending upon the observing angle phi, a correction factor must be considered in determining the length of surface 12. The correction factor is determined by the equation f(n,phi) = [n/2/-sin/2/phi] 1/2 over sin phi cos phi.

Where n is the index of refraction between medium 13 and medium 16, and phi is the observing angle between the vertical and the lowest beam refracted from surface 12.

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