Dynamic information storage or retrieval – Specific detail of information handling portion of system – Radiation beam modification of or by storage medium
Reexamination Certificate
2001-07-05
2003-11-25
Edun, Muhammad (Department: 2655)
Dynamic information storage or retrieval
Specific detail of information handling portion of system
Radiation beam modification of or by storage medium
C369S044370, C369S112100
Reexamination Certificate
active
06654336
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a semiconductor light source for emitting a light beam of two different wavelengths and an optical pickup head apparatus and a data record/playback apparatus for storage, playing back, and erasing data on an optical disk.
2. Description of the Related Art
Optical disks are known as high-density, mass-storage mediums on which data is stored in the form of a pattern of bits. The optical disks are classified into various types depending on the contents of data and the application. Characteristic examples of the optical disks are digital audio disks, video disks, text file disks, data file disks and so forth. Their applications are now increased as they are spread into in different fields. In particular, digital versatile disks (DVD) are popular and get focused as high-density optical disks for using 650 nm wavelength visible light emitted from a semiconductor laser. The DVD disks are available in different formats including read only DVD-ROM, once writable DVD-R, and rewritable DVD-RAM. Also, compact disks (CD) are widely known using a 780 nm wavelength infrared light emitted from a semiconductor laser. Similar to the DVD, the CD disks are available in different formats including read only CD-ROM, once rewritable CD-R, and multiply rewritable CD-RW.
As both DVD and CD are popular, it is desired for the convenience of any user to play back data from not only DVD-ROM and CD-ROM, but also DVD-R and CD-R with the use of a single data playback apparatus.
The CD-R and DVD-R technologies are similar to each other in storage and playing back data on the basis of different levels of the reflectivity of colors. However, the reflectivity and the absorptance are optimized in narrow wavelength ranges about 780 nm and 650 nm, respectively. This disallows CD-R data to be read and played back using the 650 nm wavelength light beam. Also, DVD-R data is hardly permitted to be read and played back using the 780 nm wavelength light beam. For compensation, each CD-R/DVD-R compatible type data record/playback apparatus has an optical pickup head equipped with a DVD-R accessible semiconductor laser and a CD-R accessible semiconductor laser.
For minimizing the overall size and the production cost of the data record/playback apparatus, the optical pickup head should be decreased in the size and the cost. One of such techniques is proposed for integrating the above described two different wavelength semiconductor lasers into a single package to simplify the optical system of the optical pickup head,
FIG. 16
illustrates an arrangement of a conventional optical pickup head apparatus
1600
such as disclosed in Japanese Patent Laid-open Publication (Heisei)10-289468. The optical pickup head apparatus
1600
has a light source
110
and a light source
120
both provided on a substrate
610
in a package
60
for emitting a beam of linearly polarized divergent light having a wavelength of 650 nm and a beam of linearly polarized divergent light having a wavelength of 780 nm, respectively.
The principle of a method of reading data from a storage medium
20
with the optical pickup head
1600
will now be explained. A light beam
100
emitted from the light source
110
or
120
is first directed to a beam composite means
30
which may be implemented by a polarizing prism (a birefringent plate) or a hologram. The beam composite means
30
aligns any light beam from either the light source
110
or the light source
120
with the optical axis. When the light beam
100
is received from the light source
120
, it is refracted or diffracted by the beam composite means
30
for deflection. The light beam
100
is then converted to a collimate light by a collimate lens
131
, circularly polarized by a ¼ wavelength plate
140
, passed through an aperture
15
, and converted to a beam of convergence light by an objective lens
132
. The light beam
100
is directed to the optical storage medium
20
and more specifically, passed through a transparent substrate
21
and focused on a data recording surface
22
. The light beam
100
is reflected on the data recording surface
22
, converted by the ¼ wavelength plate
140
to a polarized beam shifted 90 degrees from the onward beam, passed through the beam composite means
30
, and received by deflecting means
40
(a polarizing hologram) before guided to a photo detecting means
50
. A signal produced by the photo detecting means
50
is used as a data signal indicative of the data for generating a focusing error signal and a tracking error signal which are then supplied to an actuator
16
for focusing and tracking control.
It is common in the data record/playback apparatus for rewritable disks such as DVD-RAM that the tracking control signal is unstable because of shallow pits of the disks. For compensation, a diffraction grating (not shown) is provided for generating three different diffracted lights to determine the focusing error signal and the tracking error signal.
As the conventional optical pickup head apparatus
1600
includes the beam composite means
30
of a polarizing prism or hologram and the ¼ wavelength plate
140
for handling the polarized light, its optical system will significantly increase in the cost.
When the transparent substrate
21
of the optical storage medium
20
is birefringent, the light beam reflected on the optical storage medium
20
may be deflected by the beam composite means
30
and hardly received by the photo detecting means
50
which thus fails to read data from the optical storage medium
20
.
Also, while the two light sources
110
and
120
are provided on the single substrate
610
, there may be less a room for the diffraction grating which is arranged for generating three different diffracted lights and should be controlled properly. The overall dimensions of the optical pickup head apparatus itself will be increased.
SUMMARY OF THE INVENTION
It is, hence, an object of the present invention to provide a semiconductor light source package, an optical pickup head apparatus, and an optical data apparatus where a non-polarizing prism is used for minimizing the number of components and thus the overall cost. It is another object of the present invention to provide an optical pickup head apparatus and an optical data apparatus where desired data can be read out from an optical storage medium
20
while the tracking error signal is appropriately produced, even though the transparent substrate of the optical storage medium is birefringent.
A light source package according to the present invention comprises: a first light source which emits a first light beam; a second light source which emits a second light beam which is different from the first light beam; and a deflection arrangement which deflects the first and second light beams and releases the deflected light beam as a third light beam, wherein the deflection arrangement includes a first deflector which deflects the first light beam and a second deflector which deflects the second light beam such that the optical axis of the first deflected light beam from the first deflector and the optical axis of the second deflected light beam from the second deflector substantially coincide.
An optical pickup head apparatus according to one aspect of the present invention comprises: a first light source which emits a first light beam having a wavelength &lgr;
1
; a second light source which emits a second light beam having a wavelength &lgr;
2
which is different from the wavelength &lgr;
1
; a diffractor which generates a plurality of light beams from the light beam emitted from the light source; a light converging unit which converges the plurality of light beams received from the diffractor on an optical storage medium; a beam splitter which deflects the plurality of light beams converged and reflected on the optical storage medium; and a photodetector which receives deflected light beams from the beam splitter and outputs a signal relative to intensity of the deflected ligh
Kadowaki Shin-ichi
Komma Yoshiaki
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