Prism-type objective lens for the pickup head of an optical disc drive capable of driving two types of optical discs
US6137637A · kind A · utility
Assignee
Inventors
Key dates
| Filing date | Dec 30, 1999 |
| Grant date | Oct 24, 2000 |
| Priority date | — |
| Expiry date | Dec 30, 2019 |
Classification
- Technology area (CPC G)Physics
- CPC primaryG11B2007/0006
- WIPO fieldAudio-visual technology
- WIPO sectorElectrical engineering
Abstract
A prism-type objective lens is provided for use in the pickup head of an optical disc drive capable of driving two types of optical discs such as a CD and a DVD. The prism-type objective lens allows the pickup head to be made more compact in size with reduced structural complexity, and also allows the pickup head to read data from two different types of optical discs. The prism-type objective lens includes a prism having a cross section substantially in the shape of a right triangle, a front aspherical plano-convex lens, and a rear aspherical plano-convex lens, where the planar surface of each lens is attached to one or the other of the leg sides of the prism. The hypotenuse side of the prism can be formed with two aperture areas where different reflective layers are coated. Alternatively, the hypotenuse side of the prism can be formed with a reflective HOE layer that allows the laser beam incident on it and reflected from it to be diffracted into two beams which are focused at different points. Either manner allows the pickup head to read data from two different types of optical discs.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.