Method and apparatus for measuring the displacement of a radiation-restrictive mark, as in a surveying instrument
US4463259A · kind A · utility
Inventors
Key dates
| Filing date | Mar 12, 1982 |
| Grant date | Jul 31, 1984 |
| Priority date | — |
| Expiry date | Mar 12, 2002 |
Classification
- Technology area (CPC G)Physics
- CPC primaryG01D5/34723
- WIPO fieldMeasurement
- WIPO sectorInstruments
Abstract
The invention provides a method of measuring comprising: directing sources of electro-magnetic radiation, having a predetermined displacement relative to each other in a direction of measurement, to radiate over the receiving areas of electromagnetic radiation sensors also having a predetermined displacement relative to each other in a direction of measurement; sequentially switching the sources; moving a mark between the sources and the sensors, the mark causing a restriction in a cross-section measurement of the radiation passing beyond it, and the mark moving in a direction of measurement from a reference position to a position determined by the measurement being taken; detecting any changes in the sensors as a result of movement of the radiation restriction caused by movement of the mark and the switching of the sources; noting between the switching of which sources each such change occurred; and ascertaining what distance the radiation restriction moved to cause the change to occur between the noted sources.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.