Diffraction-type optical encoder with improved detection signal insensitivity to optical grating gap variations
US4943716A · kind A · utility
Assignee
Inventors
Key dates
| Filing date | Jan 18, 1989 |
| Grant date | Jul 24, 1990 |
| Priority date | — |
| Expiry date | Jan 18, 2009 |
Classification
- Technology area (CPC G)Physics
- CPC primaryG01D5/36
- WIPO fieldMeasurement
- WIPO sectorInstruments
Abstract
In a diffraction type optical displacement encoder using a diffractive light source and having a main scale grating and an index scale grating, a light-receiving element receives two rays satisfying a relationship concerning the lengths of light paths at the rays between the light source and the index scale grating, and the width of the light receiving element, wherein the difference between the path length of each ray is approximately equal to an integral multiple of the square of the pitch of the main scale grating divided by the wavelength of the light source, and the width of the light receiving element, measured as the distance between the impingement points of the two rays at the index scale, is integrally related to the difference in ray path lengths and the angle of the impinging rays due to an offsetting of the light-receiving element. In a second aspect of the invention, two light-receiving elements receive two rays satisfying a similar relationship, and a sum of outputs of the respective light-receiving elements is made to be a detection signal. Or, in an optical encoder using a collimated lighting system, an index scale is leaned (inclined) toward a main scale by a pred…
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.