Position detector and method of measuring position
US5104225A · kind A · utility
Assignee
Inventor
Key dates
| Filing date | Jan 25, 1991 |
| Grant date | Apr 14, 1992 |
| Priority date | — |
| Expiry date | Jan 25, 2011 |
Classification
- Technology area (CPC G)Physics
- CPC primaryG01D5/38
- WIPO fieldMeasurement
- WIPO sectorInstruments
Abstract
According to the principles of the invention, an improved system and method of accurately measuring the position of an object to high resolution are provided. A read head is positioned adjacent a grating. The read head emits light onto the grating. The light is diffracted into two light beams by the grating. The light beams are reflected back towards the grating, to be diffracted a second time and combined into a single beam. The polarization of the respective light beams is modified before being diffracted the second time. The polarization component of the beam parallel to the diffraction grating grooves is rotated perpendicular to the diffraction grating grooves and the component of the beam perpendicular to the diffraction grating grooves to be rotated parallel to the diffraction grating grooves. The effects of the diffraction on perpendicular or parallel polarized light are canceled because the same light impinges at two different polarizations, each the opposite of the other, prior to being combined into a single beam.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.