Illumination configuration for imaging-type optical encoders
US7227124B2 · kind B2 · utility
Assignee
Inventor
Key dates
| Filing date | Jun 20, 2005 |
| Grant date | Jun 5, 2007 |
| Priority date | — |
| Expiry date | Jun 20, 2025 |
Classification
- Technology area (CPC G)Physics
- CPC primaryG01D5/34715
- WIPO fieldMeasurement
- WIPO sectorInstruments
Abstract
An illumination configuration for imaging-type optical encoders is provided. The illumination configuration generates uniform brightness images of scales and two-dimensional structures when utilizing telecentric imaging optics in the encoder readhead. In one embodiment, a desirable uniform irradiance distribution is created across the field of view by illuminating with a collimated or quasi-collimated beam, but insuring that the illumination is sufficiently incoherent that potential self-images arising from periodic structures on the scale are suppressed. In one embodiment, the ratio of an effective emitter size to a focal length of the collimating lens falls within a selected range, so as to assure relatively uniform illumination across the field of view and still provide sufficiently incoherent illumination. In another embodiment, a diffuser is placed over the collimating lens, which assists in producing uniform illumination even when the direction of illumination varies relative to the scale due to misalignment between the readhead and the scale surface.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.