Focus detecting optical head
US5195071A · kind A · utility
Assignee
Inventors
Key dates
| Filing date | Feb 13, 1990 |
| Grant date | Mar 16, 1993 |
| Priority date | — |
| Expiry date | Feb 13, 2010 |
Classification
- Technology area (CPC G)Physics
- CPC primaryG11B7/1372
- WIPO fieldAudio-visual technology
- WIPO sectorElectrical engineering
Abstract
An optical head for detecting defocuses of a target comprises a waveguide element having a substrate and an optical waveguide layer formed thereon. An optical coupler and one or more pairs of photodetectors are integrated with the waveguide layer. Light reflected back from the target is coupled with the waveguide layer through the coupler and then waveguided toward the photodetectors while being collected. Each of the photodetectors can detect the waveguided light so that a focus error signal can be obtained from the difference of the outputs of the photodetectors. The photodetectors of each pair are spaced from each other in a propagation direction of the waveguide layer so that one of the photodetectors can block off a fraction of the waveguided light from the other photodetector when the target surface is in focus. In another form, two pairs of photodetectors are spaced forward and rearward from the focused position of the waveguided light, respectively, with respect to a propagation direction of the waveguide layer so as to receive different portions of the waveguided light.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.