Dynamic Doppler optical gauge
US4861159A · kind A · utility
Assignee
Inventor
Key dates
| Filing date | Sep 30, 1987 |
| Grant date | Aug 29, 1989 |
| Priority date | — |
| Expiry date | Sep 30, 2007 |
Classification
- Technology area (CPC G)Physics
- CPC primaryG01S17/87
- WIPO fieldMeasurement
- WIPO sectorInstruments
Abstract
An optical gauge measures the shape of a target object by scanning a laser beam over it, (and/or measures the radial velocity of the target), by measuring the Doppler frequency shift of the reflected wave. The Doppler-shifted frequency is demodulated by a phase locked loop, which has a limited hold-in frequency range within which it is capable of staying locked on. With this invention, if the reflected wave's frequency gets close to exceeding the hold-in range of the phase locked loop, the gauge adjusts the drive frequency of an acoustooptical modulator that modulates the outbound target beam. This offsets the frequency of the target beam and keeps the return signal within the hold-in range of the phase locked loop.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.