Apparatus for generating tracking error signals in a differential phase detection system
US4924455A · kind A · utility
Assignee
Inventors
Key dates
| Filing date | Apr 12, 1984 |
| Grant date | May 8, 1990 |
| Priority date | — |
| Expiry date | Apr 12, 2004 |
Classification
- Technology area (CPC G)Physics
- CPC primaryG11B7/0943
- WIPO fieldAudio-visual technology
- WIPO sectorElectrical engineering
Abstract
A tracking servo signal is generated for use in an optical disc pick-up system, being particularly advantageous for use when the depth of the pits is greater or less than one-fourth the wavelength of the light beam used to read the disc, in which case diffraction patterns formed by reflected light beams are not symmetric on a photo-detector and typically result in DC-shifted tracking error signals. A first tracking error signal is generated from selected output signals of a number of light-receiving areas of the photo-detector and a second tracking error signal is generated by combining output signals from these light-receiving areas in a pattern different than that used in generating the first tracking error signal. These two tracking error signals are combined so that the resultant signal forms a tracking servo signal that has substantially no DC component.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.