Diagnostic tests using near-infrared laser absorption spectroscopy
US5317156A · kind A · utility
Assignee
Inventors
Key dates
| Filing date | Jan 29, 1992 |
| Grant date | May 31, 1994 |
| Priority date | — |
| Expiry date | Jan 29, 2012 |
Classification
- Technology area (CPC G)Physics
- CPC primaryG01N2021/399
- WIPO fieldMeasurement
- WIPO sectorInstruments
Abstract
RF modulation spectroscopy of a near infrared laser diode source is used to determine the amount of a target substance in a breath sample. In this type of modulation the laser output is modulated to produce sidebands displaced from the laser carrier by the modulation frequency. The modulated beam is passed through a gas sample which differentially absorbs the sidebands, the result of which is the conversion of some of the laser frequency modulation into amplitude modulation which is subsequently detected using a broadband photodetector. In certain tests, the target substance is a particular isotope, whose concentration is measured as an isotope ratio. In order to measure the presence of first and second isotopic species, provision is made to provide laser illumination at characteristic wavelengths for absorption lines for the first and second isotopic species of the gas. This may sometimes be accomplished using a single laser diode and scanning at least one of its operating parameters in order to achieve one of the wavelength difference. Alternatively, first and second laser diodes operating at the first and second wavelengths are used.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.