apparatus for determining the content of a substance in a predonnee.

摘要

1365121 Analyzing substances MAXPLANCK-GES ZUR FORDERUNG DER WISSENSCHAFTEN eV 9 Aug 1971 [7 Aug 1970 14 Sept 1970 25 Nov 1970] 37338/71 Heading G1A In an apparatus for determining the amount of a substance in a material (e.g. CO 2 in a biological substance or blood) light from a laser beam is split into a sample and a reference beam the sample beam being transmitted through the substance, and the beams are received by photo-electric means which produces at least one output signal representative of the attenuation or phase shift produced in the sample beam by its passage through the sample. In Fig. 1 light from a laser beam 10 is split up into a sample and reference beam and passed through a sample cuvette 14a and comparison cuvette 14b to be subsequently united by a semi-transparent mirror 32 and received by a detector 20. A mirror 28 displaceable by a Piezo-electric crystal in an adjusting device 30 varies path length of the reference beam by using the detector 20 output so that the two light beams are always in phase or always completely out of phase, the voltage proportional to the amount of the substance present in the sample cell required to achieve this being represented on a meter 22. In Fig. 2 the laser beam is split up into a sample and reference beam with a Piezoelectrically controlled mirror 15 in the reference beam path, and both beams are passed into a detecting device 17 wherein the reference and sample beams are both split up into two subbeams and directed on to two radiation detectors 20a 20b. A Piezo-electrically controlled mirror 25 is adjusted so that both parts of the reference beam are phase shifted by 90 degrees relative to each other. The overall phase position is adjusted by the mirror 15 so that the output signals of the radiation detectors 20a and 20b correspond to the attenuation and to the phase shift of the sample radiation due to the sample. The output signals of the detectors are amplified and displayed on a recorder, for example, a cathode ray oscilloscope. The embodiment may also include a beam attenuator 33 and/or a beam modulator 35. In Fig. 4 a laser 10 whose oscillation frequency varies with time (preferably linearly) is used. A Piezo-electrically controlled mirror 42 is in the reference beam path and is controlled by the output of a detector 20' (via amplifier 40 and control device 30) which receives the sample and reference beams passing through cuvettes 14'b and 14'a respectively. The position of the mirror 42 is altered until the reference beam and sample beam are in phase and the voltage driving the mirror is fed to one input of a double beam oscilloscope 44 to provide a trace representing the phase shift as the frequency varies. The attenuation of the sample beam is measured by a comparison circuit 48 connected to the output of the radiation detector 20' and the output of a radiation detector 46 receiving a further radiation beam. The output of the comparison circuit is connected to the other input of the double beam oscilloscope 44.