Photo-thermal sensor including an expansion lens in a light beam

Details Photo-thermal sensor including an expansion lens in a light beam Photo-thermal sensor including an expansion lens in a light beam

1995-01-26

1996-04-30

Gonzalez, Frank

Optics: measuring and testing

For light transmission or absorption

G01N 2100

Patent

active

055130062

ABSTRACT:
In a photo-thermal sensor for determining the concentration of a compound in a sample which includes an excitation light source generating a first light beam of a wave length which is well absorbed by the compound to be determined, a modulator and an optical lens system disposed in the first light beam such that the first light beam is constricted at the location of the sample through which it is directed, a probe light source generating a second light beam extending at a right angle to the first light beam, a beam divider arranged at the intersection of the first and second light beams whereby part of the first light beam is deflected at one side of the beam divider and the second light beam passes through the beam divider such that both beams incide on the sample anti a photo-sensitive detector arranged in the light beam path behind the sample, a diaphragm is arranged in the beam path directly after the sample and an expansion lens adapted to expand the second light beam at the location of the sample to a diameter at least 5 times the diameter of the first light beam is disposed in the path of the second beam ahead of the beam divider for determining the loss of strength of the second light beam reaching the detector after passage through the sample and the diaphragm as an indication of the concentration of the compound in the sample.

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