Lens aberration correction in a doubly telecentric displacement sensor
US8492703B2 · kind B2 · utility
Assignee
Inventors
Key dates
| Filing date | Aug 4, 2009 |
| Grant date | Jul 23, 2013 |
| Priority date | — |
| Expiry date | Jan 8, 2032 |
Classification
- Technology area (CPC G)Physics
- CPC primaryG01D5/34
- WIPO fieldMeasurement
- WIPO sectorInstruments
Abstract
A method and apparatus for suppressing loss of scale image contrast due to interference effects from optical path length differences, including lens profile aberrations, are provided in a displacement sensing optical encoder that uses a telecentric imaging configuration. According to the invention, the encoder is configured such that the image light that reaches the detector comprises symmetric ray bundles concentrated symmetrically on opposite sides of the optical axis center at the limiting aperture of the telecentric imaging configuration. Central ray bundles, and/or other ray bundles that have an optical path lengths significantly different than the operational symmetric ray bundles are prevented or blocked. As a result destructive interference is prevented and image contrast is improved.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.