Optical encoder for detecting changes in diffraction interference patterns
US6835924B2 · kind B2 · utility
Assignee
Inventors
Key dates
| Filing date | Aug 28, 2002 |
| Grant date | Dec 28, 2004 |
| Priority date | — |
| Expiry date | Nov 6, 2022 |
Classification
- Technology area (CPC G)Physics
- CPC primaryG01D5/38
- WIPO fieldMeasurement
- WIPO sectorInstruments
Abstract
Laser light emitted from a laser light source is irradiated onto a transmission-type scale, and is diffracted by a polarization hologram recorded on the transmission-type scale. Only polarization directions of ±1-order diffracted lights, among diffracted lights, are rotated by 90°. The ±1-order diffracted lights interfere with one another such that interference fringes are formed on a light-receiving surface of a photo-detector. Interference light of the ±1-order diffracted lights is transmitted through a polarizing plate. A portion of transmitted light is passed through respective slits of a slit plate and is irradiated onto the photo-detector, and intensity of irradiated light is detected. On the other hand, 0-order diffracted light, ±2-order diffracted lights, and the like, whose polarization directions are not rotated, cannot pass through the polarizing plate, and are blocked before being detected at the photo-detector.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.