Displacement measuring apparatus and method
US4776701A · kind A · utility
Assignee
Inventor
Key dates
| Filing date | May 20, 1985 |
| Grant date | Oct 11, 1988 |
| Priority date | — |
| Expiry date | May 20, 2005 |
Classification
- Technology area (CPC G)Physics
- CPC primaryG01D5/38
- WIPO fieldMeasurement
- WIPO sectorInstruments
Abstract
Displacement measuring apparatus comprises a light source (10), a lens (12), and index grating (14), a reflective scale grating (16), and three photodetectors (18) at positions corresponding to the zero order and positive and negative first order images of the source (10). The index grating (14) has a castellated surface profile with a mark/space ratio (a/b, FIG. 3) and a castellation height (h, FIG. 3) chosen so that the three photodetectors (18) see wavefronts having a phase separation of 120. The electrical signals from the photodetectors (18) are used to sense the magnitude and direction of movement of a reading head carrying the components (10, 12, 14 and 18) with respect to the scale grating (16).
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.