Focal position detection apparatus having a light reflecting member with plural reflecting films
US5880455A · kind A · utility
Assignee
Inventors
Key dates
| Filing date | Aug 6, 1997 |
| Grant date | Mar 9, 1999 |
| Priority date | — |
| Expiry date | Aug 6, 2017 |
Classification
- Technology area (CPC G)Physics
- CPC primaryG01J3/2803
- WIPO fieldMeasurement
- WIPO sectorInstruments
Abstract
This invention relates to a focal position detection apparatus for detecting a positional shift between the imaging position of an object image formed by a predetermined objective optical system and the detection surface of the object image. This apparatus includes a beam splitter for extracting part of a light beam from the objective optical system, splitting the light beam into at least three light beams, and guiding the split light beams to the light-receiving surface of a photo-sensing device arranged at a predetermined position. This beam splitter guides at least the three split light beams to a standard optical path and a pair of reference optical path and forms a standard image at a predetermined position in the standard optical path and a pair of reference images at predetermined positions in the pair of optical paths, respectively. The imaging positions of the pair of reference images are shifted from each other in opposite direction with respect to the imaging surface on which the standard image is formed. The apparatus detects a positional shift by using the optically symmetry of at least one pair of reference images in a focusing state with respect to the standard image…
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.