Method and apparatus for double modulation spectroscopy
US4594511A · kind A · utility
Assignee
Inventors
Key dates
| Filing date | Mar 29, 1985 |
| Grant date | Jun 10, 1986 |
| Priority date | — |
| Expiry date | Mar 29, 2005 |
Classification
- Technology area (CPC G)Physics
- CPC primaryG01J3/4338
- WIPO fieldMeasurement
- WIPO sectorInstruments
Abstract
A spectroscopic technique in which the sample under investigation is probed with a generally monochromatic beam of light which has been modulated at two distinct modulation frequencies. The double modulation produces a plurality of sidebands, and the two modulation frequencies are related to one another such that a selection of sidebands falls into two groups of closely spaced component sidebands. A first group is disposed in frequency at the spectral feature of interest and serves to probe the spectral feature. The other group is disposed in frequency remote from the feature and serves as a reference group. Within each group the component sidebands are offset from one another by a characteristic offset frequency, which can be considerably less than the width of the spectral feature under investigation. After interaction with the sample the doubly modulated beam is passed on to a photodetector, which in combination with appropriate signal processing apparatus detects a signal at the characteristic offset frequency representative of the spectral feature.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.