Measuring and testing – Gas analysis – By vibration
Reexamination Certificate
2005-12-29
2010-10-19
Williams, Hezron (Department: 2856)
Measuring and testing
Gas analysis
By vibration
Reexamination Certificate
active
07814777
ABSTRACT:
The present invention relates to a photo-acoustic device (100) for photo-acoustic analysis of a sample such as exhaled human breath. The device includes a sample cell cavity (102) for containing the sample (116), a first light source (130) outside the sample cell cavity for emitting a first modulated light beam (114) at a wavelength in an absorbing range of the searched component. The first light beam is led into the cavity through a transparent cavity wall (106). The searched gas component absorbs the first light beam and first acoustic waves are thus generated which are picked up by the microphone (110). The microphone also picks up background acoustic waves caused by the laser light beam going trough the cavity wall. The device is further equipped with a noise cancellation system (120, 122) that generates a second set of acoustic waves in anti-phase with the background acoustic waves.
REFERENCES:
patent: 4412445 (1983-11-01), Spellicy
patent: 5780724 (1998-07-01), Olender et al.
patent: 6834548 (2004-12-01), Hibbs
patent: 2005/0279170 (2005-12-01), Okumura et al.
Devito Alex
Koninklijke Philips Electronics , N.V.
Williams Hezron
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