Registers – Coded record sensors – Particular sensor structure
Patent
1989-02-10
1991-10-01
Levy, Stuart S.
Registers
Coded record sensors
Particular sensor structure
235470, 369 4441, 2502086, G11B 700, H01L 2714
Patent
active
050536109
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
This invention relates to a reading apparatus and a photodetector which are usable for an optical recording medium having a clock track, data tracks and a tracking guide line.
BACKGROUND ART
An optical recording medium, such as a card type optical memory or a disc type optical memory, which has a high density data recording capability and is capable of being carriable, has recently attracted the attention of many people.
In the optical recording medium such as a card type optical memory, recording is done by forming optically (or magnetooptically) changed states according to data to be recorded at discrete spots on the surface thereof, and then a light beam, such as a laser beam, is projected thereonto to read the changed states.
Specifically, fine unevenness or light and dark patterns are provided on a surface of the optical memory card onto which a light beam is projected to recognize the recorded data according to the difference of reflectivity, refractive index, or transmissivity of the medium to the projected light beam. Alternatively, the recording medium may be photothermo-magnetically recorded and the recorded data may be read depending upon the change of polarization of the projected light due to the magnetooptical effect.
The optical memory card has a clock track for enabling synchronization with data reading/writing and a tracking guide line functioning as a reference for a light beam from a reading optical system to accurately trace a track. The track and line are provided for each of the data track in the conventional optical memory card and juxtaposed each other.
Heretofore, optical signals are detected by separate detectors for reading the data and clock bits, for effecting tracking and focussing in the reading of the data on the optical recording medium as described above. With this system, the optical system should inevitably be large and it is difficult to reduce the size and weight of a reading apparatus.
DISCLOSURE OF THE INVENTION
It is therefore an object of the present invention to provide a reading apparatus for an optical recording medium which is capable of being reduced in size and weight by making a photodetector for the optical recording medium compact in structure.
A first invention features a reading apparatus for an optical recording medium having a clock line, data tracks and a tracking guide line, which apparatus comprises:
a photodetector which receives light images of the clock track, data tracks and tracking guide line;
a clock detecting circuit which is responsive to a signal from the clock track generated by the photodetector to output a clock signal;
data detecting circuit which encodes data read from the data tracks by the photodetector into a binary code in response to the clock signal; and
a focus error detecting circuit for detecting a focus error and a tracking error detecting circuit for detecting a tracking error in response to a signal from the tracking guide line by the photodetector;
said photodetector being comprised of first to fourth light-sensitive elements which receive a light image of the tracking guide line, a fifth light-sensitive element which receives a light image of the clock track and a sixth light-sensitive element which receives a light image of the data track.
The first and the second light-sensitive element may be arranged in a line and said third and said fourth light-sensitive element are arranged in a line parallel with said line of the first and the second light-sensitive element in alignment with the first and the second element, respectively.
The fifth and the sixth light-sensitive element may be arranged in rows in a direction perpendicular to the parallel lines.
The clock track and the tracking guide line may be provided on the same line on the optical recording medium and said sixth light-sensitive element of the photodetector is disposed at a position which is surrounded by said first to fourth light-sensitive elements.
The first to the sixth light-sensitive element may be integrated on one substrate.
A sec
REFERENCES:
patent: 4550249 (1985-10-01), Damen et al.
patent: 4787075 (1988-11-01), Matsuoka et al.
patent: 4797868 (1984-01-01), Ando
patent: 4816665 (1989-03-01), Hsu
patent: 4831609 (1989-05-01), Suzuki
patent: 4837429 (1989-06-01), Umezawa et al.
duBois Steven M.
Kabushiki Kaisha CSK
Levy Stuart S.
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