Dynamic information storage or retrieval – With servo positioning of transducer assembly over track... – Optical servo system
Reexamination Certificate
2000-11-10
2003-07-22
Hindi, Nabil (Department: 2651)
Dynamic information storage or retrieval
With servo positioning of transducer assembly over track...
Optical servo system
C369S044410, C369S120000, C369S109010
Reexamination Certificate
active
06597642
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an optical reproduction apparatus that is used to read information from optical recording media, an optical recording apparatus that is used to write information onto optical recording media, an optical pickup, and a photodetector unit.
2. Description of the Related Art
In recent years, various standards adopting different physical formats have been created for optical recording media. For instance, optical recording media based on different standards have different recording densities. This generates demand for a multi-standard optical reproduction apparatus that can reproduce various types of optical recording media having different physical formats.
A multi-standard optical reproduction apparatus, which reproduces optical recording media having different recording densities, is disclosed by Japanese Laid-Open Patent Application No. H9-180212.
In this conventional optical reproduction apparatus, a photodetector unit for receiving returning light reflected by an optical recording medium includes a plurality of photodetectors to obtain received light signals for a three-beam method and received light signals for a differential phase detection method. Here, each of these methods is used to detect a tracking error signal for driving a tracking servo. The three-beam method is used for low-density optical recording media (conventional CD-ROMs), while the differential phase detection method is used for high-density optical recording media (DVD-ROMs).
The optical reproduction apparatus first receives a user's specification showing whether an optical recording medium placed therein has a high recording density. If the optical recording medium has a high recording density, the optical reproduction apparatus detects a tracking error signal according to the differential phase detection method. If the optical recording medium has a low recording density, the optical reproduction apparatus detects a tracking error signal according to the three-beam method. The optical reproduction apparatus then drives its tracking servo using the detected tracking error signal.
By selectively using the three-beam method and the differential phase detection method to detect tracking error signals in this manner, the conventional optical reproduction apparatus reproduces both of low-density optical recording media, such as CD-ROMS, and high-density optical recording media, such as DVD-ROMs.
As described above, the conventional optical reproduction apparatus is capable of reproducing optical recording media (such as CD-ROMs and DVD-ROMs) having different recording densities. However, it is difficult for this reproduction apparatus to support other types of optical recording media that have recently become available.
More specifically, because recent optical recording media adopt various physical formats having different track pitches and different track shapes (pit sequences or continuous grooves), it is difficult to reproduce these optical recording media with a single optical reproduction apparatus. As a result, a plurality of optical reproduction apparatuses need to be used to reproduce the different types of optical recording media, which puts an enormous economic burden upon consumers. The same problem applies to optical recording apparatuses.
SUMMARY OF THE INVENTION
The first object of the present invention is to provide a photodetector unit that is suitable for the reproduction of or recording onto various types of optical recording media that have different track shapes and different track pitches. The second object of the present invention is to provide an optical pickup that is equipped with the photodetector unit and is capable of reproducing or recording onto various types of optical recording media. The third object of the present invention is to provide an optical reproduction apparatus that is suitable for the reproduction of various types of optical recording media. The fourth object of the present invention is to provide an optical recording apparatus that is suitable for the recording onto various types of optical recording media.
The first object is achieved by a photodetector unit for use with an optical pickup that irradiates an optical recording medium with a laser beam and receives returning light reflected by the optical recording medium, where the optical pickup is constructed to (1) divide the laser beam into a main beam, a preceding sub-beam, and a succeeding sub-beam, (2) direct the main beam, the preceding sub-beam, and the succeeding sub-beam toward the optical recording medium, and (3) divide returning lights of the main beam, the preceding sub-beam, and the succeeding sub-beam respectively into first-fourth main returning lights, first-fourth preceding returning lights, and first-fourth succeeding returning lights, and the photodetector unit includes: first-fourth main photodetectors that respectively receive the first-fourth main returning lights; first-fourth preceding photodetectors that respectively receive the first-fourth preceding returning lights; and first-fourth succeeding photodetectors that respectively receive the first-fourth succeeding returning lights.
This construction allows the photodetector unit to detect at least three types of tracking error signals by combining the received light signals from a plurality of photodetector groups. Therefore, the optical pickup equipped with this photodetector unit appropriately drives the focusing servo and tracking servo according to the tracking error signal corresponding to the type of the optical recording medium.
Here, the first-fourth main photodetectors may be arranged in a virtually straight line, and each of the first-fourth main photodetectors may include at least two photodetecting portions arranged perpendicular to an arrangement direction of the first-fourth main photodetectors. The photodetector unit may further include: a first wiring group that includes first signal lines and transmits a received light signal used to perform a push-pull method, the first signal lines being respectively connected to the photodetecting portions of the first-fourth main photodetectors, the first-fourth preceding photodetectors, and the first-fourth succeeding photodetectors; a second wiring group that includes second signal lines and transmits a received light signal used to perform a differential phase detection method, the second signal lines being respectively connected to the photodetecting portions of the first-fourth main photodetectors; and a third wiring group that includes third signal lines and transmits a received light signal used to perform a three-beam method, the third signal lines being respectively connected to the first-fourth preceding photodetectors and the first-fourth succeeding photodetectors.
With this construction, the first-third wiring groups output received light signals respectively appropriate to the push-pull method, differential phase detection method, and three-beam method that are tracking error signal detection methods.
Here, the photodetector unit may further include: a first circuit that generates a first tracking error signal from the received light signal, which is transmitted from the first wiring group, according to the push-pull method; a second circuit that generates a second tracking error signal from the received light signal, which is transmitted from the second wiring group, according to the differential phase detection method; and a third circuit that generates a third tracking error signal from the received light signal, which is transmitted from the third wiring group, according to the three-beam method.
With this construction, the first-third circuits independently generate the first-third tracking error signals according to the push-pull method, differential phase detection method, and three-beam method.
The first object is also achieved by a photodetector unit for use with an optical pickup that irradiates an optical recording medium with a laser beam and receives returning light r
Ijima Shin'ichi
Nakanishi Hideyuki
Takasuka Shoichi
Yoshikawa Akio
Hindi Nabil
Matsushita Electric Industrial Co. LTD
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