Dynamic information storage or retrieval – With servo positioning of transducer assembly over track... – Optical servo system
Reexamination Certificate
2001-06-29
2004-12-14
Edun, Muhammad (Department: 2655)
Dynamic information storage or retrieval
With servo positioning of transducer assembly over track...
Optical servo system
C369S124010
Reexamination Certificate
active
06831882
ABSTRACT:
TECHNICAL FIELD
The present invention relates to an optical head of an optical disk memory, which is an apparatus for optically recording and reproducing information, and an optical head feed apparatus thereof.
BACKGROUND ART
In this so-called information age, many attempts are being actively made to develop new techniques for high-density large-capacity memories, which constitute the core of information technology. In addition to high density and large capacity, high reliability, rewritability and the like are required of memories, and among memories satisfying these requirements, optical disk memories, such as photomagnetic disks, are attracting particular note.
Many reports can be found on techniques pertaining to optical heads for use with optical disks. Out of various optical heads for use with optical disks, an optical head for use in minidisk apparatuses and the like, which is an optical head for rewritable photomagnetic disks, will be described below with reference to accompanying drawings.
FIG. 7
schematically illustrates an external view of a conventional optical head for use with minidisks and the like. A description of its configuration and operation will follow.
In
FIG. 7
, reference numeral
1
denotes an optical disk (not shown in the plan), and
2
, a light receiving/emitting element configured as a single device mounted inside with a semiconductor laser chip, which is a light emitting section emitting a laser beam, as well as an optical signal detecting section for receiving reflected light resulting from the reflection of this laser beam by the optical disk
1
and detecting various signals.
Reference numeral
3
denotes a mirror for letting the laser beam from the light receiving/emitting element
2
reach the optical disk
1
;
4
, an objective lens (not shown in the plan) for focusing the laser beam reflected by the mirror
3
on the optical disk
1
and forming a minute light spot; and
5
, an objective lens actuator (not shown in the plan) for letting the objective lens
4
follow any eccentricity or surface oscillation of the optical disk
1
.
Reference numeral
6
denotes a magnetic head (not shown in the plan) for realizing, where the optical disk
1
is a recordable disk, so-called magnetic field-modulated recording by applying a modulated magnetic field;
6
a
, a fitting section for fixing the magnetic head
6
to a resin-made bench
7
;
7
, a resin-made bench on which these parts are mounted;
7
a
and
7
b
, reference sections into which shafts
8
a
and
8
b
are to be inserted, respectively;
7
c
, a light receiving/emitting element fixing section to which the light receiving/emitting element
2
is to be fixed; and
7
d
, a mirror fixing section to which the mirror
3
is to be fixed.
Reference numeral
9
denotes a flexible wiring board to be connected to an external circuit (not shown). To this board, the light receiving/emitting element
2
having a light emitting section and an optical signal detecting section for causing a semiconductor laser to emit light and detecting information signals from the optical disk
1
is electrically connected in a position
9
a
by soldering a wire or otherwise.
Further, the flexible wiring board
9
is mounted with a high-frequency superimposing circuit (not shown) for reducing noise due to returning light from the optical disk
1
.
As described above, in the optical head composed of parts mounted on the resin-made bench
7
, a laser beam is emitted by the light receiving/emitting element
2
as power is fed from the flexible wiring board
9
, and the objective lens
4
forms a minute light spot in a prescribed position on the optical disk
1
as the objective lens actuator
5
is driven, similarly receiving power feed from the flexible wiring board
9
(the section for power feed to the actuator is not shown).
When a read-only optical disk
1
is to be read back, the magnetic head
6
does not operate, and the light receiving/emitting element
2
detects the so-called reflected light quantity of the optical disk
1
. Where the optical disk
1
also permits recording, when it is recording, the light receiving/emitting element
2
emits optical power of a certain intensity, and performs so-called magnetic field-modulated recording with modulated signals from the, magnetic head
6
. During a reproducing process, the magnetic head
6
does not operate, and the light receiving/emitting element
2
detects rotation of the polarizing surface from the optical disk
1
to implement the reproducing function.
Incidentally, although the above-described configuration can help reduce the cost and weight of the bench compared with a conventional die-cast metal bench by using a resin as its material, the resin-made bench, which is inferior in thermal conductivity to a metallic bench which excels in heat radiation, reduces head radiation by the semiconductor laser.
FIG. 8
shows the variation in the junction temperature of the semiconductor laser over time. (3) in
FIG. 8
shows the temperature rise of the light receiving/emitting element by itself, and (2), its temperature rise when the light receiving/emitting element is mounted on a metallic bench. Comparison of the two curves reveals an approximately 1.9 times as great a rise when the light receiving/emitting element is by itself.
The condition of the light receiving/emitting element mounted on a resin-made bench can be regarded as substantially the same as that of the light receiving/emitting element by itself. However, where a resin-made bench is used, there is the problem that the temperature rise of the light emitting section shortens the service life of the semiconductor laser.
Moreover, when the temperature of the semiconductor laser rises, the amperage required to emit the same optical power also increases, entailing the problem of increased power consumption.
Furthermore, in a recording type optical head, the semiconductor laser is caused to emit light under high-frequency superimposition to reduce noise due to returning light.
However, a configuration of the optical head using a resin-made bench also involves the problem that the ground of the optical head consists only of a flexible wiring board connected to an external circuit, and can be provided with no firm grounding.
Another example of the disk recording/reproducing apparatus according to the prior art will be described below.
FIGS. 26
,
27
,
28
,
29
,
30
and
31
are schematic configurational diagrams of its optical head according to the prior art and diagrams for describing its operating principle.
FIG. 26
shows an exploded perspective view of the optical head. Reference numeral
109
denotes an integrated unit, part of which is illustrated in FIG.
30
. Reference numeral
134
denotes a flexible circuit shown in FIG.
27
.
FIG. 28
illustrates a state in which the flexible circuit
134
is fitted to the integrated unit
109
. FIG.
32
(
a
) shows an exploded perspective view, and (
b
), an overall perspective view of the optical head.
Herein, reference numeral
101
denotes a silicon substrate;
102
, a semiconductor laser fixed over the silicon substrate
101
;
3
, a multi-divided light detector formed by an IC process over the silicon substrate
101
;
104
, a radiator plate for holding the silicon substrate
101
in a thermally conductive state via silver paste;
105
, a terminal wire-connected from the multi-divided light detector by wire bonding or the like; and
106
, a resin package for holding the silicon substrate
101
, the radiator plate
104
and the terminal
105
.
FIG. 31
shows the optical configuration of the optical head. Reference numeral
107
denotes a hologram element (diffraction grating) formed of resin; and
108
, a composite element composed of a beam splitter
108
a
, a folded mirror
108
b
and a polarizing-separating element
108
c.
What is integrally configured of the elements denoted by
101
through
108
above is defined to be the integrated unit
109
.
Reference numeral
110
denotes a reflector mirror;
111
, an objective lens fixed to an objective lens h
Aikoh Hideki
Kuroda Tadashi
Nakata Hideki
Takashima Makoto
Tanaka Toru
Edun Muhammad
Matsushita Electric - Industrial Co., Ltd.
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