Radiant energy – Photocells; circuits and apparatus – Optical or pre-photocell system
Patent
1991-11-21
1994-05-03
Nelms, David C.
Radiant energy
Photocells; circuits and apparatus
Optical or pre-photocell system
25022719, 73800, H01J 516
Patent
active
053089731
ABSTRACT:
A method and the device for fiber-optic measurement of the absolute value of the pretensioning in a highly loaded mechanical structural component part are based on the measurement of the phase displacement of a light wave caused by the strain-induced birefringence in a single-mode light waveguide 4 which is embedded between two metallic disks or washers 3a, 3b. Since the measurement results are ambiguous modulo-2.pi., serial or simultaneous measurement with two light wavelengths .lambda..sub.1, .lambda..sub.2 is used according to a first method variant of the invention. The quantity of 2.pi. periods can be unequivocally determined within a predetermined measuring range by means of comparing the two measurement results. The evaluation is preferably effected according to a quadrature or phase step method, known per se. According to second method variant, the light waveguide 4 is irradiated with polarized white light. The phase difference of the two linear modes due to the influence of force on the structural component part is compensated for in a compensation device 20. The control signal required for the compensation of the path difference is evaluated as a measurement for the force. The compensation method has the advantage that no monochromatic light sources are required.
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Dandliker Rene
Odoni Walter
Schad Hanspeter
Schweizer Edwin
Allen Stephone B.
Hilti Aktiengesellschaft
Nelms David C.
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