Optical head and information recording apparatus
US5361244A · kind A · utility
Assignee
Inventors
Key dates
| Filing date | Apr 8, 1992 |
| Grant date | Nov 1, 1994 |
| Priority date | — |
| Expiry date | Apr 8, 2012 |
Classification
- Technology area (CPC H)Electricity
- CPC primaryH01S5/0683
- WIPO fieldOptics
- WIPO sectorInstruments
Abstract
Disclosed herein is a compact, adjustment-free, unitary optical head wherein diffraction grating made of a birefrigence material and having convexities and concavities of grating grooves so set that the difference of their optical path lengths is some multiples and a half of the wavelength for an ordinary beam and an extraordinary beam, a diffraction grating providing astigmatisms to .+-.1 order beams, a quarter wavelength plate, and other optical components, are interposed between a semiconductor laser and a focussing lens and are stored inside an optical head body filled with a dry nitrogen gas. A focus error detection signal is obtained from the difference of the degrees of modulation of the .+-.1 order reflected beams by pre-wobbled pits, and adjustment of the optical beam can be carried out by driving the body by a two-directional head actuator.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.