Method and apparatus for absolute interferometry using a measurement beam and a reference beam having parallel wave fronts and sharing a single beam path
US5502562A · kind A · utility
Assignee
Inventor
Key dates
| Filing date | Sep 27, 1994 |
| Grant date | Mar 26, 1996 |
| Priority date | — |
| Expiry date | Sep 27, 2014 |
Classification
- Technology area (CPC G)Physics
- CPC primaryG01B9/02007
- WIPO fieldMeasurement
- WIPO sectorInstruments
Abstract
A method and apparatus are disclosed for implementing absolute interferometry with radiation generated by diode laser whereby relative or absolute distance measurement can be performed without need of a reference interferometer, with only a single detector, and with high precision determination of the length of the measurement distance. The method comprises modulating the radiation generated by the diode laser in such a way that the diode laser is frequency-modulated at at least one discrete frequency, which then is detected with a known phase-sensitive detection method. Due to the modulation of the original radiation of the diode laser, a second laser beam is in effect produced, with the result that a single beam path includes a measurement beam and a reference beam. Each of these beams, i.e. the measurement beam and the reference beam, is at a different frequency, but the two have parallel wave fronts, pass along exactly the same optical path in the unitary beam, and interfere at the single detector. The length of the measurement distance is then found by a determination of phase shift or determination of the phase change of the modulation signal. Alternatively, the modulation fr…
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.