Dynamic information storage or retrieval – Control of storage or retrieval operation by a control... – Mechanism control by the control signal
Patent
1984-01-30
1987-03-31
Cardillo, Raymond F.
Dynamic information storage or retrieval
Control of storage or retrieval operation by a control...
Mechanism control by the control signal
369 44, 369120, G11B 2100, G11B 713, G11B 2110
Patent
active
046548386
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an optical head control signal generator for generating a signal to control an optical head employed in an optical information reproducing apparatus for optically reproducing information recorded on a recording medium with a beam of light, and more particularly to an optical head control signal generator capable of generating an optical head control signal for causing a light beam to enter into information recording tracks on a recording medium in proper conditions with reduced adverse influences due to a condition of recorded medium regions forming the information recording tracks, a tilt of the recording medium, and other causes.
2. Description of the Prior Art
There is known a reproducing system for playing back a disc-shaped recording medium having information recording tracks in which information signals such as video signals and audio signals are recorded with a series of pits. In the reproducing system, the information recording tracks on the recording medium are scanned by a beam of light such as a laser beam, and variations which the light beam is subjected to are detected to reproduce the recorded information signals. Such a recorded information reproducing system is known as a video disc system, a digital audio disc system and so on. A reproducing apparatus for such a system requires automatic control modes respectively for enabling the light beam to reach the information recording tracks accurately at all times and for focusing the light beam properly on the information recording tracks while scanning the information recording tracks with the light beam. The automatic control modes for causing the light beam to arrive exactly at the information recording tracks and for focusing the light beam properly on the information recording tracks are called tracking control and focusing control, respectively, and are indispensable in the optical information reproducing apparatus of the type described.
These control modes are normally achieved by causing the light beam to enter through an optical head into the recording medium, receiving the light beam as modulated by the recording medium with the optical head, delivering the received light beam to a photosensitive element, generating control signals indicative of conditions in which the light beam reaches and is focused on the information recording tracks based on a detected output from the photosensitive element, and driving optical means such as a lens, a mirror and so on constituting the optical head with the control signals for positional control. FIG. 1 of the accompanying drawings illustrates, by way of example, an optical arrangement for an optical head control signal generator for supplying control signals to such a control device for an optical head in the optical recorded information reproducing apparatus. A disc-shaped recording medium 1 carries information recording tracks composed of a series of pits. A laser beam emitted from a laser source 2 enters a polarizing prism 4 through a collimator lens 3. The laser beam directed to the left as shown by the polarizing prism 4 reaches an objective lens 7 through a mirror 5 and a quarter wave plate 6. The laser beam is then focused by the objective lens 7 on the recording medium 1. The objective lens 7 is able to be driven for being positionally controlled, for example, in a direction to traverse the information recording tracks and in a direction toward or away from the recording medium. The laser beam falling on the recording medium 1 is modulated by the information recording tracks, reflected back into the objective lens 7, and then travels through the quarter wave plate 6, the mirror 5, the polarizing prism 4, and a prism 8 before reaching a photosensitive unit 9. The reflected light beam, or reading light beam, as modulated by the recording medium and delivered from the objective lens 7 constituting an optical head is detected by photosensitive elements which the photosensitive unit 9 is composed of. Variatio
REFERENCES:
patent: 4057833 (1977-11-01), Braat
patent: 4296316 (1981-10-01), Tsuji et al.
patent: 4445208 (1984-04-01), Yamamoto et al.
patent: 4458144 (1984-07-01), Reilly et al.
patent: 4467462 (1984-08-01), Shibata
patent: 4502134 (1985-02-01), Kondo et al.
Cardillo Raymond F.
Eslinger Lewis H.
Nguyen Hoa T.
Sinderbrand Alvin
Sony Corporation
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