Radiant energy – Photocells; circuits and apparatus – Optical or pre-photocell system
Patent
1993-08-27
1995-08-29
Allen, Stephone B.
Radiant energy
Photocells; circuits and apparatus
Optical or pre-photocell system
25023119, 385 12, 73705, G02B 626, H01J 516
Patent
active
054462797
ABSTRACT:
A first surface of a diaphragm is exposed to high temperature gas in the combustion chamber of an internal combustion engine. The curvature of the diaphragm changes in response to the gas pressure. Three optical fibers are spaced along a radius of the diaphragm and have ends which face a second surface of the diaphragm. A light source injects light into a center fiber, which is displaced from the center of the diaphragm by a predetermined distance. Outer fibers receive light from the center fiber after reflection from the diaphragm. The relative intensities of light reflected from the diaphragm into the outer fibers correspond to the curvature of the diaphragm and thereby to the pressure. The outer fibers have a larger numerical aperture than the center fiber, and the light source fully populates all of the optical modes of the center fiber to reduce modal noise caused by physical perturbation of the fibers. The fibers preferably have a square cross-section to maximize linearity. Structure is provided to inhibit thermally induced curvature of the diaphragm. A computer computes the pressure in response to the relative reflected light intensities. A temperature sensor provides an input to the computer which enables compensation for variation of the sensitivity of the diaphragm with temperature.
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Allen Stephone B.
Denson-Low W. K.
Duraiswamy V. D.
Hughes Aircraft Company
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