Dynamic information storage or retrieval – Specific detail of information handling portion of system – Radiation beam modification of or by storage medium
Reexamination Certificate
1998-02-23
2001-04-03
Tran, Thang V. (Department: 2651)
Dynamic information storage or retrieval
Specific detail of information handling portion of system
Radiation beam modification of or by storage medium
C369S044230, C369S044370
Reexamination Certificate
active
06212150
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an optical pickup apparatus and an optical recording medium drive employing the same.
2. Description of the Background Art
In recent years, an optical pickup apparatus using a holographic optical element as light beam separating means has been studied and developed.
FIG. 11
is a diagram showing the construction of a conventional optical pickup apparatus. The optical pickup apparatus is an apparatus for performing focus servo using an astigmatism method and tracking servo using a three-beam method in addition to an information detecting operation, which is disclosed in Japanese Patent Laid-Open No.76035/1991, for example.
As shown in
FIG. 11
, the optical pickup apparatus comprises a semiconductor laser device
102
for emitting laser light vertically upward, a diffraction grating
103
for dividing the laser light into three light beams, a holographic optical element
104
for transmitting the three light beams obtained by the division and diffracting returned light beams from an optical disk
100
, an objective lens
105
for focusing the three light beams transmitted by the holographic optical element
104
on a recording surface of the optical disk
100
as three spots, and an optical detector
106
for detecting the returned light beams diffracted by the holographic optical element
104
.
In the above-mentioned optical pickup apparatus, the laser light emitted from the semiconductor laser device
102
is divided into zero order and ± 1st order diffracted light beams by the diffraction grating
103
, after which the light beams are incident on the holographic optical element
104
. The three diffracted light beams are transmitted by the holographic optical element
104
, and are focused as a main spot and two sub-spots on the recording surface of the optical disk
100
by a light-focusing function of the objective lens
105
.
The three laser light beams focused on the optical disk
100
are reflected as three returned light beams including an information signal having information recorded on the optical disk
100
. The returned light beams are incident on the holographic optical element
104
upon passing through the objective lens
105
. The holographic optical element
104
transmits the three returned light beams as + 1st order and − 1st order diffracted light beams. The + 1st order diffracted light beam is incident on a light receiving surface of the optical detector
106
. The optical detector
106
outputs a reproducing signal, a focus error signal obtained by an astigmatism method, and a tracking error signal obtained by a three-beam method on the basis of the returned light beam (+ 1st order diffracted light beam) received.
In the above-mentioned conventional optical pickup apparatus, only one of the returned light beams transmitted as the + 1st order diffracted light beam and the − 1st order diffracted light beam by the holographic optical element
104
, for example, the + 1st order diffracted light beam is introduced into the optical detector
106
, and the other returned light beam, for example, the − 1st order diffracted light beam is not utilized. Therefore, a detecting current from the optical detector
106
which corresponds to the power of the laser light emitted from the semiconductor laser device
102
is small. In order to increase output power of an information detecting signal from the optical disk
100
, therefore, an output of the semiconductor laser device
102
must be increased, or an output signal from the optical detector
106
must be amplified.
In a method of increasing the output of the semiconductor laser device
102
, however, a load on the semiconductor laser device
102
may, in some cases, be excessively large. On the other hand, in a method of amplifying the detecting signal from the optical detector
106
, the frequency band of the detecting signal is narrowed as the amplification factor is increased, thereby degrading the frequency characteristics.
SUMMARY OF THE INVENTION
An object of the present invention is to provide an optical pickup apparatus capable of increasing output power of a detecting signal from an optical recording medium without degrading frequency characteristics and an optical recording medium drive employing the same.
An optical pickup apparatus according to the present invention for irradiating an optical recording medium with a light beam and detecting a returned light beam from the optical recording medium comprises a light source for emitting the light beam, a first diffraction element for transmitting the light beam emitted from the light source and introducing the light beam into the optical recording medium as well as diffracting the returned light beams from the optical recording medium in at least first and second directions, a first light receiving element for receiving a detecting light beam for detecting the state of the light beam on the optical recording medium out of the returned light beam diffracted in the first direction by the first diffraction element, and a second light receiving element for receiving a reproducing light beam for reproducing information recorded on the optical recording medium out of the returned light beam diffracted in the second direction by the first diffraction element.
The optical pickup apparatus according to the present invention comprises the first and second light receiving elements. The first light receiving element is so arranged as to receive the returned light beam diffracted in the first direction by the first diffraction element, to receive the reproducing light beam out of the returned light beam and output a reproducing signal. The second light receiving element is so arranged as to receive the returned light beam diffracted in the second direction by the first diffraction element, to receive the detecting light beam out of the returned light beam and output a detecting signal. Consequently, it is possible to reproduce the information recorded on the optical recording medium and perform various control operations using the detecting signal at the time of the reproduction, so that the controllability of a reproducing operation with respect to the optical recording medium is improved.
The optical pickup apparatus may be so constructed as to further comprise a second diffraction element for dividing the light beam emitted from the light source into a main light beam and a sub-light beam, and that the state of the light beam is a tracking state on the optical recording medium, the reproducing light beam is the main light beam, the detecting light beam is the sub-light beam for detecting the tracking state, the first light receiving element has a light receiving portion for receiving the sub-light beam, and the second light receiving element has a light receiving portion for receiving the main light beam.
In this case, it is possible to reproduce the information from the optical recording medium by an output signal based on the main light beam received by the second light receiving element, and it is possible to detect a tracking error on the optical recording medium by a detecting signal based on the sub-light beam received by the first light receiving element. Further, in the second light receiving element for receiving the main light beam, the main light beam may be incident on a region of the light receiving portion, so that high precision is not required for alignment between the main light beam and the light receiving portion. Therefore, it becomes easy to adjust the position of the second light receiving element.
The optical pickup apparatus may be so constructed as to further comprise a second diffraction element for dividing the light beam emitted from the light source into a main light beam and a sub-light beam, and that the state of the light beam is a focused state on the optical recording medium, the reproducing light beam and the detecting light beam are the main light beam in common, the first light receiving elem
Goto Takenori
Ibaraki Akira
Inoue Yasuaki
Mori Kazushi
Sawada Minoru
Armstrong Westerman Hattori McLeland & Naughton LLP
Sanyo Electric Co,. Ltd.
Tran Thang V.
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