Objective lens design method, lens, and optical system, optical head, and optical disc apparatus using the same
US7414796B2 · kind B2 · utility
Assignee
Inventors
Key dates
| Filing date | Nov 12, 2004 |
| Grant date | Aug 19, 2008 |
| Priority date | — |
| Expiry date | Mar 2, 2027 |
Classification
- Technology area (CPC G)Physics
- CPC primaryG11B2007/0006
- WIPO fieldAudio-visual technology
- WIPO sectorElectrical engineering
Abstract
When the DVD provided with the DVD substrate 2 having thickness t2 of 0.6 mm is installed in the optical disc apparatus, the light beam 4 having wavelength λ1=655 nm is used as luminous flux of numerical aperture NA=0.63 to be condensed on the information surface 2a on the DVD substrate 2. When the CD provided with the CD substrate 3 having thickness t2 of 1.2 mm is installed in the optical disc apparatus, the light beam 5 having wavelength λ2=790 nm is effectively used as luminous flux of approximate numerical aperture NA=0.45 to be condensed on the information surface 3a on the DVD substrate 3. The wavefront aberration caused by a thickness difference between the DVD substrate 2 and CD substrate 3 is canceled out by the chromatic aberration caused by a wavelength difference between the light beams 4 and 5. Therefore, in spite of the difference in the transparent substrates, the light beams are suitably condensed respectively on the information surface 2a and 3a.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.