Optical encoder for optically measuring displacement of moving body
US6154278A · kind A · utility
Assignee
Inventors
Key dates
| Filing date | Jun 10, 1994 |
| Grant date | Nov 28, 2000 |
| Priority date | — |
| Expiry date | Jun 10, 2014 |
Classification
- Technology area (CPC G)Physics
- CPC primaryG01D5/38
- WIPO fieldMeasurement
- WIPO sectorInstruments
Abstract
In order to improve signal modulation characteristics and detect a position at a higher precision, collimated light of wavelength .lambda. and beam radius D enters a fixed diffraction plate and a movable diffraction plate comprising a grating of pitch "p". The grating has main diffraction components of orders .+-.1. The plates are arranged in parallel with a distance "g" between them and generally perpendicular to an optical axis of the beam. The beam diffracted by the diffraction plates and in parallel to the optical axis of the beam is condensed with a condenser lens for limiting an incident pupil size to be within D-2 g.lambda./p. The amount of the light condensed by the condenser lens is detected by a photosensor. In a different example, a collimated light beam enters a first fixed plate and a rotary diffraction plate successively to transmit diffracted light of orders .+-.1. Then, the transmitting light is guided to a symmetrical point with respect to a rotation center of the rotary plate. Then, the beam is transmitted through the rotary plate and a second fixed plate which transmits only diffracted light of orders .+-.1. Then the beam is detected by a sensor. Then, even if th…
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.