Heterodyne interferometer system
US4688940A · kind A · utility
Assignee
Inventors
Key dates
| Filing date | Mar 12, 1985 |
| Grant date | Aug 25, 1987 |
| Priority date | — |
| Expiry date | Mar 12, 2005 |
Classification
- Technology area (CPC G)Physics
- CPC primaryG01B2290/70
- WIPO fieldMeasurement
- WIPO sectorInstruments
Abstract
A heterodyne interferometer system utilizes a single stabilized frequency linearly polarized laser input beam (18) from a light source (10) which is provided to an acousto-optic device (20) along with a frequency stabilized electrical reference signal (32) from an oscillator (30) for transforming the input beam (18) into a pair of orthogonally polarized beams (40,50) differing in frequency by the reference signal frequency prior to providing these beams (40,50) to a polarization type interferometer (70). A mixing polarizer (60) mixes the beams (46,56) after they traverse the interferometer (70) and provides the mixed beams (62,64) to a photoelectric detector (65) where they are utilized to produce an electrical measurement signal (66). This electrical measurement signal (66) is processed in a phase meter/accumulator (68) along with the reference signal (32) to produce an output signal (80) which is the sum of phase difference on a cycle-by-cycle basis between the measurement signal (66) and the reference signal (32). The phase meter/accumulator (68) includes an analog-to-digital converter (83) and a memory register (92) for the previous cycle, with the measurement resolution being …
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