Appeal No. 97-0345
Application 08/363,094
application. Claims 1 through 47 have been canceled.
The invention relates to an absorption spectroscopy
device for determining the concentration of a gas in a sample
cell containing the gas.
As illustrated in Appellants’ Figure 17, a laser
diode 170 generates laser radiation 171 which passes through
neutral density absorber 173 and then through sample cell 174
to radiation detector 175. Sample cell 174 contains a gas of
unknown concentration. Laser diode 170 is tuned to the
wavelength of an absorption line which is characteristic of
the gas whose concentration is being measured. When laser
radiation 171 emerges from sample cell 174, its reduced
intensity (absorbed by the gas) is detected by detector 175,
and this information is used to determine the gas
concentration.
Neutral density absorber 173 is used to reduce the
effects of unwanted reflections of the laser radiation such as
that caused by dust particle 176. Such unwanted reflections
tend to cause laser diode instabilities and mode-hops. In
another embodiment, the neutral density absorber is replaced
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