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Integrated Optical Force and Stress Sensor

IP.com Disclosure Number: IPCOM000052713D
Original Publication Date: 1981-Jul-01
Included in the Prior Art Database: 2005-Feb-11
Document File: 1 page(s) / 12K

Publishing Venue

IBM

Related People

Korth, H: AUTHOR

Abstract

Force sensors for measuring accelerations, stresses, etc., are the most important means of obtaining quantitative values. Their design generally permits the force applied to be compensated by an elastic component, so that the resultant displacement can be measured.

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Integrated Optical Force and Stress Sensor

Force sensors for measuring accelerations, stresses, etc., are the most important means of obtaining quantitative values. Their design generally permits the force applied to be compensated by an elastic component, so that the resultant displacement can be measured.

For more accurate measurements, an interferometric method is used. Interferometric measuring devices permit the direct conversion of analog length values into corresponding digital values by counting the orders of interference. By means of interpolation, a single order of interference can be evaluated down to as little as O.l%. For a distance corresponding to 10/4/ orders of interference, the measuring precision obtainable is about 1:10/7/.

The new method utilizes the stress-induced birefringence effect, whereby the symmetry of any solid-state medium is disturbed by stress. As a result, the propagation velocity of light and the refractive index, respectively, become a function of the direction of polarization. For typical solid-state media (such as glass), this effect is relatively small, e.g., delta n ~/~ 10/-4/. The advantages of interferometry become apparent when the length of the optical path in the birefringent medium can be varied by some 10/4/ orders of interference. This can be achieved by high stress and a relatively long optical path.

An embodiment of the measuring device used comprises a thin substrate of glass, silicon, etc., which is subjected to...