Dynamic information storage or retrieval – With particular cabinet structure
Reexamination Certificate
1999-10-01
2002-04-30
Huber, Paul W. (Department: 2651)
Dynamic information storage or retrieval
With particular cabinet structure
C369S121000
Reexamination Certificate
active
06381207
ABSTRACT:
CROSS-REFERENCE TO RELATED APPLICATIONS
This application is based upon and claims priority of Korean Patent Application No. 98-41503 filed Oct. 2, 1998, the contents being incorporated herein by reference.
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an optical pickup of an optical disk drive for recording and/or reproducing information on/from an optical disk. More particularly, the present invention relates to an optical pickup for an optical disk drive, the optical pickup having a light path controlling device to control occurrence of beam shift and field angle.
2. Description of the Related Art
A conventional optical disk drive projects a laser beam to an information recording surface of an optical disk, detects a signal based on the reflectivity, the phase, the polarized light variation and the like of the laser beam reflected from the information recording surface, and processes the signal thereby obtaining required information recorded on the information recording surface.
As shown in
FIG. 1
, the conventional optical disk drive includes an optical pickup
1
for projecting the laser beam to an optical disk
40
and for detecting the signal from the reflected laser beam, a driving section
2
for moving the optical pickup
1
to a predetermined position with respect to the information recording surface of the optical disk
40
, a signal processing section
3
for processing the signal detected by the optical pickup
1
to convert the signal into the required information, and a controlling section
4
for controlling the above elements. The driving section
2
includes a spindle motor
5
for rotating the optical disk
40
, a thread motor
6
for moving the optical pickup
1
, and a servo section
7
for controlling the spindle motor
5
and thread motor
6
.
When an external signal is input to the conventional optical disk drive shown in FIG.
1
and described above, the optical pickup
1
is moved in a radial direction of the optical disk
40
by the operation of the driving section
2
, while recording information to the optical disk
40
and detecting the signals recorded in the information recording surface of the optical disk
40
by projecting the laser beam to the optical disk
40
. The detected signals are processed by the signal processing section
3
, converted into the required information, and then output to external devices.
In the above-described conventional optical disk drive, the optical pickup
1
is an essential element for recording information to and detecting information from the information recording surface of the optical disk
40
. The optical pickup
1
includes a laser beam source for generating the laser beam, an optical system for projecting the laser beam generated from the laser beam source to the information recording surface of the optical disk
40
, and a pickup base for fixedly supporting the laser beam source and the optical system. A laser diode is utilized as the laser beam source, and the optical system includes a collimating lens, a reflective mirror, and an objective lens.
However, an error with respect to a light emitting point and a light emitting angle may occur in the process of manufacturing the conventional optical pickup
1
. Further, an error may occur in parts of the optical system during the process of manufacturing or assembling. One type of error, referred to hereinafter as “beam shift”, occurs when the central line of an objective lens does not coincide with the central line of a collimating lens, resulting in the central line of the laser beam source not coinciding with the collimating lens. Another type of error, referred to hereinafter as “field angle”, occurs when the central line of the laser beam does not coincide with the center of the collimating lens, causing the central line of the laser beam to be received by the objective lens in a non-perpendicular relation thereto. The combination of errors bring an asymmetric distribution of the laser beam intensity. The beam shift and/or field angle should be controlled within a predetermined range, since these two errors cause malfunctions in recording and/or reproducing the information with respect to the information recording surface of the optical disk
40
. Accordingly, the optical pickup
1
usually includes light path controlling means for controlling the possible occurrence of the beam shift and field angle.
The optical pickup
1
of the conventional optical disk drive will be described in more detail hereinafter with respect to
FIG. 2
, which is a schematic diagram of the optical pickup
1
. As shown in
FIG. 2
, the optical pickup
1
includes an objective lens
11
disposed at an upper-side surface of a pickup base
10
, and a reflective mirror
12
disposed below the objective lens
11
to reflect the laser beam projected by the objective lens
11
through a light path. Further, a collimating lens
13
and a laser diode
14
are arranged in sequential order in the light path.
The laser beam generated from the laser diode
14
is transmitted through the collimating lens
13
and projected to the reflective mirror
12
, where the laser beam is reflected to the objective lens
11
to be projected to the information recording surface of the optical disk
40
which is positioned thereabove.
The collimating lens
13
is supported within a first light path adjusting plate
20
, while the laser diode
14
is supported within a second light path adjusting plate
30
. The first light path adjusting plate
20
is movably disposed at the end portion of the pickup base
10
so as to move upward/downward and leftward/rightward with respect to the pickup base
10
. Further, the second light path adjusting plate
30
is movably disposed at the end portion of the first light path adjusting plate
20
so as to be moved in vertical and lateral directions with respect to the collimating lens
13
. When the first light path adjusting plate
20
is moved, the second light path adjusting plate
30
is also moved together therewith. However, the movement of the second light path adjusting plate
30
does not affect the movement of the first light path adjusting plate
20
.
The beam shift and field angle can be adjusted by moving the first and second light path adjusting plates
20
and
30
. The adjustment of the beam shift and field angle with the conventional optical pickup
1
will be described hereinafter with reference to
FIGS. 3A through 3D
.
FIGS. 3A through 3D
are views illustrating the light path controlling operation of the conventional optical pickup
1
. For the purpose of convenience in description, the laser diode
14
, the collimating lens
13
, the objective lens
11
, and the optical disk
40
are arranged in a straight line in the figures while the reflective mirror
12
is omitted.
FIG. 3A
illustrates the situation in which a beam shift has occurred. As shown in
FIG. 3A
, in the situation in which a beam shift has occurred, the laser beam generated from the laser diode
14
coincides with a central line of the collimating lens
13
, while the objective lens
11
is not aligned with the collimating lens
13
so that the central line A of the laser beam is upwardly deviated toward the objective lens
11
. Accordingly, the laser beam has an unbalanced light intensity distribution on the optical disk
40
. The portions shown by the dotted lines in
FIG. 3A
are where the light intensity distribution is balanced.
The beam shift shown in
FIG. 3A
can be adjusted by moving the first light path adjusting plate
20
downward such that the central line A of the laser beam coincides with the center of the objective lens
11
, as shown in FIG.
3
B. Since the second light path adjusting plate
30
is moved along with the first light path adjusting plate
20
, the beam shift can be adjusted without affecting the field angle.
FIG. 3C
illustrates a situation in which the field angle has occurred, and
FIG. 3D
illustrates adjustment of the field angle.
As shown in
FIG. 3C
, the objective lens
11
and the collimating lens
1
Kim Seok-jung
Kim Tae-kyung
Lee Yong-jae
Ryoo Byung-ryul
Seong Pyong-yong
Huber Paul W.
Staas & Halsey , LLP
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