Dynamic information storage or retrieval – Specific detail of information handling portion of system – Radiation beam modification of or by storage medium
Reexamination Certificate
2001-02-26
2004-06-08
Tran, Thang V. (Department: 2653)
Dynamic information storage or retrieval
Specific detail of information handling portion of system
Radiation beam modification of or by storage medium
C369S112280, C369S044120
Reexamination Certificate
active
06747939
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates generally to a semiconductor laser device used for reproducing information from optical disks with different formats, such as a compact disk (CD) and a digital video disk (DVD), in a single optical pickup device.
2. Related Background Art
Currently, the CD market is the largest market among the optical disk markets. In the device for reproducing information from CDs, a near infrared semiconductor laser element with a wavelength in a 780 nm to 800 nm band has been used. On the other hand, for recording and reproduction with respect to DVDs, which are optical media with higher recording density and are expected to come into wide use rapidly in the future, a red-color semiconductor laser element with a shorter wavelength in a 635 nm to 680 nm band has been used, since a light spot is required to have a small diameter. It has been requested to enable information to be recorded and reproduced with respect to two such kinds of optical disks with different standards in one device. An optical pickup device for such a purpose is described, for example, in JP 10(1998)-320815.
FIG. 9
shows a configuration of a conventional optical pickup device.
An operational principle of the conventional optical pickup device is described with reference to
FIG. 9
as follows.
For recording and reproduction with respect to a CD, a semiconductor laser element
101
with a wavelength of 780 nm is used. A beam
116
emitted from the semiconductor laser element
101
in the direction perpendicular to the surface of an optical disk
106
is diverged into three beams by a diffraction grating
115
. A collimator lens
103
disposed on an optical axis converts the divergent beam into a parallel beam. The parallel beam goes through a wavelength deflection filter
109
and is focused on the optical disk
106
by an objective lens
105
.
The beam reflected by the optical disk
106
is converted from a divergent beam into a parallel beam by the objective lens
105
and goes through the wavelength deflection filter
109
again. Subsequently, the beam is converted into a converged beam by the collimator lens
103
and then enters a hologram element
111
. The beams divided by the hologram element
111
are detected as electric signals in receiving optics
113
. Based on the detected signals, the reproduction and focusing/tracking servo are carried out with respect to the CD.
On the other hand, for recording and reproduction with respect to a DVD, a semiconductor laser element
102
with a wavelength of 635 nm (or 650 nm) is used. A beam
117
emitted from the semiconductor laser element
102
in a direction parallel to the surface of an optical disk
106
is converted from a divergent beam into a parallel beam by a collimator lens
104
disposed on an optical axis and goes through a polarization beam splitter
107
and a ¼ wavelength plate
108
. Subsequently, the beam is reflected by the wavelength deflection filter
109
so that its path is deflected by 90°, and then is focused on the optical disk
106
by the objective lens
105
.
The beam reflected by the optical disk
106
is converted from a divergent beam into a parallel beam by the objective lens
105
and is reflected by the wavelength deflection filter
109
again so that its path is deflected by 90°. Subsequently, its polarization direction is changed by the ¼ wavelength plate
108
. Therefore, the beam entering the polarization beam splitter
107
is reflected so that its path is deflected by 90°, and then is converged by a detection lens
110
. The converged beam goes through a cylindrical lens
112
and is detected as an electric signal in receiving optics
114
. Based on this detection signal, reproduction and focusing/tracking servo are carried out with respect to the DVD.
In the above-mentioned configuration, the semiconductor laser with a wavelength of 780 nm is mounted and therefore recording and reproduction also can be carried out with respect to CD-Rs.
However, such a conventional optical pickup device as shown in
FIG. 9
is configured with many optical components such as two semiconductor laser elements
101
and
102
with different emission wavelengths and a plurality of receiving optics
113
and
114
for respective beams emitted from the semiconductor laser elements
101
and
102
, as well as the hologram element
111
, the cylindrical lens
112
, the wavelength deflection filter
109
, and the like. Therefore, it is difficult to reduce the size of the device.
Moreover, since the respective optical components are disposed discretely, a lot of positional adjustments and fixation are required, and thus great amounts of time and cost are required for the assembly, which have been problems.
SUMMARY OF THE INVENTION
Therefore, the present invention was made to solve the aforementioned conventional problems. The present invention is intended to provide a small and inexpensive semiconductor laser device capable of carrying out recording and reproduction with respect to various optical disks with different formats and to provide an optical pickup device having the same.
In order to achieve the above-mentioned object, a semiconductor laser device according to the present invention includes a receiving/emitting optics integrated substrate and an optical element. In the receiving/emitting optics integrated substrate, a first semiconductor laser element, a second semiconductor laser element, and a plurality of receiving optics are integrated on a substrate. The first and second semiconductor laser elements have different emission wavelengths. A distance L
1
, when measured in air, from the first semiconductor laser element to a focusing member is substantially equal to a distance L
2
, when measured in air, from the second semiconductor laser element to the focusing member.
According to this configuration, the two semiconductor laser elements and the plurality of receiving optics are integrated in the receiving/emitting optics integrated substrate, so that a small and inexpensive semiconductor laser device can be provided. In addition, since the distances, when measured in air, from the two semiconductor laser elements to the focusing member are substantially equal, one single focusing member (for instance, a collimator lens) can be employed. Thus, the optical configuration is simplified.
In the semiconductor laser device according to the present invention, preferably, a difference between the distance L
1
and the distance L
2
, when measured in air, is within ±50 &mgr;m.
According to this configuration, particularly the influence of aberration can be suppressed to a low level and it becomes easy to configure the optical pickup device employing a single focusing member.
In the semiconductor laser device according to the present invention, preferably, the optical element is disposed in an optical path at least between the first or second semiconductor laser element and the focusing member.
This configuration enables return light from the optical disk to diverge efficiently to be lead to the receiving optics.
In addition, it is preferable that the optical element includes a member allowing a distance for which a beam emitted from the first semiconductor laser element travels to go through the optical element to be different from a distance for which a beam emitted from the second semiconductor laser element travels to go through the optical element.
According to this configuration, the distances for which the two emitted beams travel to go through the optical element are made different, so that the distances, when measured in air, for which the two emitted beams travel after leaving the optical element can be made substantially the same.
It also is preferable that a light diverging member is formed in the optical element and a diffraction grating, a reflector, or the like is used as the light diverging member.
In the semiconductor laser device according to the present invention, preferably, the first semiconductor laser element has an emission
Nakanishi Hideyuki
Nakanishi Naoki
Saitoh Yukio
Takasuka Shoichi
Merchant & Gould P.C.
Tran Thang V.
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