Method and apparatus for reducing fringe interference in laser spectroscopy
US5267019A · kind A · utility
Assignee
Inventors
Key dates
| Filing date | Sep 30, 1991 |
| Grant date | Nov 30, 1993 |
| Priority date | — |
| Expiry date | Sep 30, 2011 |
Classification
- Technology area (CPC G)Physics
- CPC primaryG01N2021/399
- WIPO fieldMeasurement
- WIPO sectorInstruments
Abstract
A method and apparatus using a frequency tunable laser to generate a beam which passes through a sample cell and onto an optical detector wherein the tunable laser is modulated at a predetermined frequency which has the undesired effect of producing a periodic interference fringe near an absorption induced signal. An additional level of modulation is applied to the laser beam by a triangular waveform having a predetermined peak-to-peak amplitude and frequency. The triangular waveform peak-to-peak amplitude produces a frequency swing of the laser beam so as to generate from the periodic interference fringe, a signal having reduced components near the absorption induced signal. The signal at the optical detector is demodulated by a lock-in amplifier tuned to a predetermined harmonic of the frequency of the triangular waveform.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.