Focus error detecting apparatus
US5233444A · kind A · utility
Assignee
Inventors
Key dates
| Filing date | Jul 24, 1990 |
| Grant date | Aug 3, 1993 |
| Priority date | — |
| Expiry date | Jul 24, 2010 |
Classification
- Technology area (CPC G)Physics
- CPC primaryG11B7/123
- WIPO fieldAudio-visual technology
- WIPO sectorElectrical engineering
Abstract
A focus error detecting apparatus in which a light emitting and receiving element including a light emitting portion and light receiving portions all of which are formed in a common semiconductor substrate, a hologram element diffracts a light beam reflected by an object to generate plus and minus first-order diffraction light beams and to introduce an astigmatism into the plus and minus first-order diffraction light beams such that shapes of spots of the diffraction light beams formed on the light receiving portions of the light emitting and receiving element vary into substantially reverse directions to each other, and a focusing condition is detected in accordance with outputs of the light receiving portions. Therefore, in this apparatus, positioning adjustment of the light receiving portions with respect to the light emitting portion is not necessary, and thus a number of the adjusting process can be remarkably decreased and the cost for manufacturing the apparatus can be reduced. Furthermore, the focusing condition can be detected with high accuracy.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.