Focal position detecting optical apparatus
US4450547A · kind A · utility
Assignee
Inventors
Key dates
| Filing date | Oct 20, 1981 |
| Grant date | May 22, 1984 |
| Priority date | — |
| Expiry date | Oct 20, 2001 |
Classification
- Technology area (CPC G)Physics
- CPC primaryG11B7/22
- WIPO fieldAudio-visual technology
- WIPO sectorElectrical engineering
Abstract
A focal position detecting optical apparatus wherein a light beam focused by a first optical system is irradiated on an object to be illuminated, focal point images are formed at two foci spaced apart from each other by a cylindrical lens disposed in a path of light beam reflected from the object, and a shielding element having a tip edge making an angle of approximately 45.degree. with an operating axis of the cylindrical lens is inserted at a site between the two foci and at which the light beam has a circular cross section to extract a portion of the light beam travelling between the two foci. The extracted portion is detected by two photodetectors disposed symmetrically with an axis lying in substantially the same direction as the tip edge, and the difference between outputs of the two photodetectors is produced for detection of an actual focal position of the first optical system.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.