Laser distance measuring method and apparatus
US4856893A · kind A · utility
Assignee
Inventor
Key dates
| Filing date | Sep 30, 1987 |
| Grant date | Aug 15, 1989 |
| Priority date | — |
| Expiry date | Sep 30, 2007 |
Classification
- Technology area (CPC G)Physics
- CPC primaryG01S17/87
- WIPO fieldMeasurement
- WIPO sectorInstruments
Abstract
A laser distance measuring apparatus in which source beams from two lasers are combined and focused on a target. One beam is continuous wave and one has periodic narrow pulse envelopes. After reflection the composite reflected beam is redivided in a diffraction grating and compared with two respective reference beams by means of two photodetectors. Doppler data are provided, as well as separate high resolution and low resolution range output data. Integration of the Doppler data in a computer, and combination of the three data signals there, enable an unusually complete and accurate record of the shape of the target even if the shape has many severe discontinuities, as in the case of a turbine rotor. An alternative embodiment provides for switching the pulse time of flight portion of the system to utilize various harmonics of the pulse envelope waveform. Known phase delays are switchably interposed in one channel so that relative phase readings between the reference and target pulses are performed at near-zero phase differences. Phase readings can be made accurately when the signals possess near-zero phase differences. Fixed errors can be measured and calibrated out of measurement …
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.