Apparatus and method for performing two-frequency interferometry
This patent describes an apparatus that includes a two-frequency, Zeeman-effect laser and matched, doubly refracting crystals in the construction of an accurate interferometer. Unlike other interferometric devices, the subject invention exhibits excellent phase stability owing to the use of single piece means for producing parallel interferometer arms, making the interferometer relatively insensitive to thermal and mechanical instabilities. Interferometers respond to differences in optical path length between their two arms. Unlike many interferometric techniques, which require the measurement of the location of interference fringes in a brightly illuminated background, the present invention permits the determination of the optical path length difference by measuring the phase of an electronic sine wave. The apparatus is demonstrated as a differential thermooptic spectrometer for measuring differential optical absorption simply and accurately which is but one of many applications therefor.
- Assignee:
- Dept. of Energy, Washington, DC (USA)
- Patent Number(s):
- US 4906095; A
- Application Number:
- PPN: US 7-147468A
- OSTI ID:
- 7065725
- Resource Relation:
- Patent File Date: 25 Jan 1988
- Country of Publication:
- United States
- Language:
- English
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