Optical encorder for detection having a moving reference point
US5981941A · kind A · utility
Assignee
Inventors
Key dates
| Filing date | May 20, 1997 |
| Grant date | Nov 9, 1999 |
| Priority date | — |
| Expiry date | May 20, 2017 |
Classification
- Technology area (CPC G)Physics
- CPC primaryG01D5/38
- WIPO fieldMeasurement
- WIPO sectorInstruments
Abstract
The present invention provides an optical encoder capable of using the recesses and convexes of a movable plate and a fixed plate to accurately generate a Z phase signal in synchronism with an A/B phase signal. Phase type diffraction gratings on the moving and fixed plates including a plurality of tracks with different grating pitches cause parallel coherent beams to interfere with one another, and a light receiving part detects the intensity of light to obtain a plurality of synchronous signals with different periods. On the other hand, the light receiving part detects light spots formed by condensing elements on the movable plate to generates a single pulse per rotation as a reference position. One of the plurality of synchronous signals that has the shortest period is selected as an A/B phase signal that depends on the movement of the movable plate. The conjunction of the reference position signal and the plurality of synchronous signals is determined as a Z phase signal indicating the origin of the movable plate, thereby obtaining a Z phase signal in synchronism with one pulse of the A/B phase signal.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.