Method of and apparatus for controlling the optical reading of recorded information
US4118736A · kind A · utility
Assignee
Inventors
Key dates
| Filing date | Sep 28, 1977 |
| Grant date | Oct 3, 1978 |
| Priority date | — |
| Expiry date | Sep 28, 1997 |
Classification
- Technology area (CPC G)Physics
- CPC primaryG11B7/095
- WIPO fieldAudio-visual technology
- WIPO sectorElectrical engineering
Abstract
Information which is recorded on a record medium is read therefrom by a main beam of radiant energy, such as a main light beam, which impinges and scans the record medium so as to be modulated with the recorded information. An additional beam of radiant energy also impinges upon the record medium, and both the main and additional beams pass through a common objective lens which focusses the beams. The main beam, after impinging upon the record medium and being modulated with the recorded information, is detected. The transmission path of the main beam, and particularly its impinging location on the record medium, is controlled in accordance with the detection thereof. Also, the additional beam is detected after it impinges upon the record medium. The effective focussing position of the objective lens is adjusted in accordance with the detected additional beam. Defocussing of the main beam which may occur in the event that its transmission path is adjusted is minimized by further adjusting the effective focussing position of the objective lens as a function of the adjustment of the transmission path of the main beam.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.