Radiant energy – Invisible radiant energy responsive electric signalling – Infrared responsive
Reexamination Certificate
2007-02-27
2007-02-27
Porta, David (Department: 2884)
Radiant energy
Invisible radiant energy responsive electric signalling
Infrared responsive
Reexamination Certificate
active
11227477
ABSTRACT:
The gas detector device comprises at least a VCSEL source and at least a light sensor for detecting a light beam having passed through a sample chamber containing a given gas to be detected. The detection signal of the sensor directly provided to or is time derivated by an electronic derivator and then provided to respective lock-in amplifiers in order to generate a two different 2f-detection, f being the frequency of a wavelength modulation of the source, and thus to provide two corresponding measuring signals the division of which gives a precise value of the gas concentration. The invention uses at least a first modulation reference signal at twice and a second modulation reference signal at twice of the modulation frequency of the laser source. Providing at least a first 2f modulation reference signal has advantages over the prior art, because by using such a reference modulation signal it is possible measure the absolute intensity and therefore to receive the same result at different temperatures or at mode hopping of the laser. A further advantage is that the measurement accuracy is independent from the gas concentration.
REFERENCES:
patent: 6064488 (2000-05-01), Brand et al.
patent: 6172759 (2001-01-01), Goldstein
patent: 6356350 (2002-03-01), Silver et al.
patent: 6995846 (2006-02-01), Kalayeh et al.
Kohli Markus
Seifert Andreas
Willing Bert
Bachman & LaPointe P.C.
IR Microsystems SA
Porta David
Taningco Marcus
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