Relative movement detecting apparatus using a detector positioned in a region of natural interference
US5646730A · kind A · utility
Assignee
Inventors
Key dates
| Filing date | Jan 23, 1996 |
| Grant date | Jul 8, 1997 |
| Priority date | — |
| Expiry date | Jan 23, 2016 |
Classification
- Technology area (CPC G)Physics
- CPC primaryG01D5/38
- WIPO fieldMeasurement
- WIPO sectorInstruments
Abstract
The apparatus disclosed herein employs a grating (13) which concentrates light at a preselected wavelength into the positive (33) and negative (35) first orders while minimizing the zeroth order (31). The grating (13) is illuminated with monochromatic light of the selected wavelength and a poly-phase periodic detector (25) has its sensing plane spaced from the grating a distance less than ##EQU1## where W is the width of the illuminated region of the grating. The period of the poly-phase detector is equal to P/2 so that each detector element (51) or phase responds principally to the natural interference between the positive and negative first orders without requiring magnification or redirection of the diffracted light. Preferably, the distance of the sensing plane from the grating (13) is greater than ##EQU2## so that the detector response does not include substantial components from diffraction orders higher than the first. Various embodiments of the invention are described including a wavefront compensation approach which greatly increases design freedom in the selection of grating and detector characteristics in implementing the present invention in practical and manufacturable…
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.