Method and apparatus for feedback stabilized photometric detecti

Details Method and apparatus for feedback stabilized photometric detecti Method and apparatus for feedback stabilized photometric detecti

1981-10-19

1985-01-01

Howell, Janice A.

Radiant energy

Invisible radiant energy responsive electric signalling

Infrared responsive

250345, 356433, G01J 100

Patent

active

044917309

ABSTRACT:
A photometric detection method and apparatus employ a variable beam modulation device, such as a planar oscillating disk whose reflectance and transmittance with respect an incident beam of electromagnetic radiation vary with disk angular position, to form, from an incident beam of radiation, two amplitude modulated correlated component beams. Preferably the amplitudes of the component beams vary sinusoidally, 180.degree. out of phase. In one illustrative embodiment, one of the component beams passes through a sample fluid, which absorbs a portion of the radiation at a wavelength characteristic of a selected component. The second component beam passes through a reference path and provides a reference signal relative to which changes in the sample fluid are measured. A feedback mechanism is provided to automatically adjust for variations which can occur while the apparatus is operating. The component beams are combined and are directed onto a detector which produces an output proportional to the intensity of the combined beam. By properly selecting the parameters of the system, the AC component of the combined signal, if any, provides a sensitive measure of the presence generally and if calibrated the relative density, of the selected sample fluid.

REFERENCES:
patent: 3897154 (1975-07-01), Hawes
patent: 4057734 (1977-11-01), Barringer
patent: 4176963 (1979-12-01), Fabinski et al.

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