Optics: measuring and testing – By polarized light examination – With polariscopes
Patent
1993-12-15
1995-12-19
Rosenberger, Richard A.
Optics: measuring and testing
By polarized light examination
With polariscopes
356368, 178633, 178664, G01J 400, A61B 500
Patent
active
054773270
ABSTRACT:
Two linearly polarized beams of monochromatic laser light are amplitude modulated with low frequency sinusoids. The first laser is modulated with a sinusoid 90.degree. out of phase from the second laser. The two beams of laser light have their polarization axis fixed and separated by 45.degree.. These two beams are then collimated and combined into one composite beam using simple optics. This composite beam is then allowed to pass through an optically active substance of a calibrated path length. The laser radiation exiting the sample is passed through a optical notch pass filter, reducing any signal that may be present from any polarized ambient light by passing only light of the laser's frequency. The composite beam then passes into a beam splitting polarizing cube. This cube has the function of separating the beam into two orthogonal polarization components. The two beams of light exiting the cube are focused onto silicon photoelectric detectors. The cube is oriented such that one of the cube's transmission axis is aligned to coincide with the polarization axis of one of the lasers. The current from the detectors is converted into a voltage. The resulting detector voltages are then AC coupled to remove any DC component of the voltage, leaving only signal. These voltages are then subtracted using an instrumentation grade operational amplifier. The subtracted signal is phase shifted in direct proportion to solution concentration. Setting the ratio of laser signal amplitudes greater than unity can further amplify this phase shift to produce high instrument sensitivity.
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Bergman Research Group, Inc.
Eisenberg Jason D.
Rosenberger Richard A.
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