Optical inspection device and method
US4822164A · kind A · utility
Assignee
Inventor
Key dates
| Filing date | Sep 30, 1987 |
| Grant date | Apr 18, 1989 |
| Priority date | — |
| Expiry date | Sep 30, 2007 |
Classification
- Technology area (CPC G)Physics
- CPC primaryG01S17/50
- WIPO fieldMeasurement
- WIPO sectorInstruments
Abstract
A closed loop optical gauge directs a laser beam toward an object whose radial velocity, instantaneous position, and/or shape are to be measured, and utilizes the Doppler frequency shift of the reflected beam to make measurements. A reference sample of the original direct beam has its frequency shifted by an acoustooptical modulator. A closed loop system is created by sensing the difference in frequency between the reflected beam and the shifted reference beam. The amount of frequency modulation is then controlled so that the frequency of the shifted reference beam continuouly tracks that of the reflected beam, preferably with a fixed offset of frequency. The output can be integrated with respect to time to obtain position or shape information. Absolute distance to the object is measured by transmitting a train of pulses of light toward the object and receiving reflected light pulses back. The round trip time of the light pulses is ascertained by measuring the phase displacement of the envelope of the reflected signals relative to the envelope of the transmitted light signals, with the aid of a phase locked loop. The oscillator of the phase locked loop is locked to the envelope of …
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.