Photoelastic sensor using a variable intensity light source as a

Details Photoelastic sensor using a variable intensity light source as a Photoelastic sensor using a variable intensity light source as a

1983-06-07

1985-12-03

Nelms, David C.

Radiant energy

Photocells; circuits and apparatus

Optical or pre-photocell system

250205, 73657, G02F 101

Patent

active

045567913

ABSTRACT:
Light from an external source is collimated, polarized, passed through a voltage dependent quarterwave plate and onto an elasto-optic sensor which serves to retard the light passing therethrough as a function of the external stress being measured. Light emanating from the sensor is divided into components at .+-.45.degree. to the applied stress axis. These components are coupled through optical fibers to photodetectors and the resulting electrical signals are applied to difference amplifier. The amplifier output is used to control a second light source whose output via an optical fiber is converted to a voltage suitable to drive the voltage dependent quarterwave plate in a negative feedback fashion such that the wave retardations resulting from the applied stress and nulled out. The power necessary to drive the voltage dependent quarterwave plate is used as a measure of the applied stress.

REFERENCES:
patent: 3902805 (1975-09-01), Redner
patent: 4171908 (1979-10-01), Robert
patent: 4180328 (1979-12-01), Drain
patent: 4368645 (1983-01-01), Glenn

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