Dynamic information storage or retrieval – With servo positioning of transducer assembly over track... – Optical servo system
Reexamination Certificate
1998-11-10
2001-07-24
Psitos, Aristotelis M. (Department: 2753)
Dynamic information storage or retrieval
With servo positioning of transducer assembly over track...
Optical servo system
C369S112280
Reexamination Certificate
active
06266301
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates generally to an optical storage device for reading or reading/writing information from and to an optical storage medium by use of an optical head and, more particularly, to an optical storage device for controlling a movement of a light beam.
2. Description of the Related Art
In an optical storage device such as an optical disk device etc, an optical head irradiates an optical storage medium with a light beam, thereby reading and writing information. In this optical storage device, a laser spot for scanning an information track on an optical disk is located on the information track. An objective lens of the optical head is therefore precisely moved in a track direction as well as in a focusing direction. A decrease in weight of the optical head is required of this optical storage device.
FIG. 16
is an explanatory diagram showing the prior art.
An optical disk
90
is formed with an information track in a spiral configuration or in a concentric configuration. An optical head
91
comprises a movable member
91
-
1
and a fixed member
91
-
2
. The movable member
91
-
1
is provided with an objective lens
92
, a focus actuator
93
for moving the objective lens
92
in the focusing direction, a track actuator
94
for moving the objective lens in the track direction, a lens position sensor
95
, and a deflection mirror
96
.
The fixed member
91
-
2
includes a light emitting diode and a divided-by-4 light receiving unit. A light beam emitted from the light emitting diode of the fixed member
91
-
2
is incident upon the objective lens
92
via the deflection mirror
96
, and falls upon the optical disk
90
. The light beam reflected from the optical disk
90
is incident upon the fixed member
91
-
2
via the objective lens
92
and the deflection mirror
96
.
In the fixed member
91
-
2
, the reflected light beam is received by the divided-by-4 light receiving unit in which a light receiving element is divided by 4. A signal generating circuit
98
calculates an output of the divided-by-4 light receiving unit, and generates a focus error signal FES, a track error signal TES and an ID signal etc. The focus error signal FES indicates a focusing-directional deviation of the light beam from the track.
A DSP-based control circuit
99
focus-servo-controls the focus actuator
93
on the basis of the focus error signal FES, and thus adjusts a focusing position of the light beam. The track error signal TES indicates a track-directional deviation of the light beam. A control circuit
99
track-servo-controls the track actuator
94
on the basis of the track error signal TES, and thus locates the light beam on the track.
A motor
97
constructed of a linear motor etc moves the movable member
91
-
1
of the optical head
91
in a track traversing direction of the optical disk
90
. The optical head
91
is thereby subjected to a coarse seek process.
In this construction, the lens position sensor
95
generates a lens position signal LPOS indicating a position of the objective lens
92
. This lens position signal LPOS is, when the optical head
91
is moved by the motor
97
(when in the coarse seek process), used for locking the objective lens
92
. More specifically, when in the coarse seek process, a present position is detected based on the track error signal TES, thereby executing the seek control. Therefore, if the objective lens
92
is not fixed, the present position is unable to be accurately detected. Hence, the control circuit
99
controls the track actuator
94
on the basis of the lens position signal LPOS. The objective lens
92
is thereby locked.
Further, the lens position signal LPOS is used for, with the movement of the objective lens
92
, when implementing a track access process (a track jump process), detecting the position of the objective lens. Moreover, the lens position signal LPOS is used for, when performing eccentricity compensation control of the optical disk, detecting the position of the objective lens
92
.
Thus, the seek control is carried out so that the light beam is disposed in a central position of the objective lens
92
by use of the lens position signal LPOS. The generation of the thus-used lens position signal LPOS involves providing the movable member
91
-
1
of the optical head
91
with the lens position sensor
95
.
There arise, however, the following problems inherent in the prior art.
First, the optical head
91
is light in weight, which is better for the optical head effecting a high-speed seek to a target track. Therefore, the movable member
91
-
1
of the optical head
91
is mounted with only parts needed for making the movable member
91
-
1
movable. The movable member
91
-
1
is, however, required to be mounted with the lens position sensor
95
, and hence the weight of the movable member
91
-
1
can not be reduced. It is therefore difficult to speed up the seeking process.
Second, since the lens position sensor
95
consists essentially of the light emitting unit and the light receiving unit, the costs thereof are high. Consequently, the optical storage device has a difficulty to be constructed at low costs.
SUMMARY OF THE INVENTION
It is a primary object of the present invention to provide an optical storage device capable of speeding up a seeking process by reducing a weight of an optical head.
It is another object of the present invention to provide an optical storage device capable of making the optical head constructed at low costs.
It is still another object of the present invention to provide an optical storage device capable of generating a lens position signal without providing a lens position sensor.
According to one aspect of the present invention, an optical storage device for reading information from an optical storage medium by an optical head, comprises an optical head including an objective lens for irradiating the optical storage medium with a laser beam, a track actuator for scanning on the skew across tracks on the optical storage medium by the laser beam, and a divided-by-4 light receiving unit for receiving the laser beam from the optical storage medium, a moving mechanism for moving the objective lens and the track actuator of the optical head, a first signal processing circuit for calculating a track error signal on the basis of an output of the divided-by-4 light receiving unit, a second signal processing circuit for calculating a shift signal for indicating a shift quantity of the objective lens from the output of the divided-by-4 light receiving unit, and a control circuit for controlling the track actuator or the moving mechanism by the track error signal, and controlling the track actuator or the moving mechanism so that the laser beam passing through the objective lens is located at the center of the objective lens.
According to the present invention, a lens position signal is generated from the output of the divided-by-4 light receiving unit. Therefore, the tracks on the optical storage medium are scanned obliquely by the laser beam. With this contrivance, a distribution of reflected light incident upon the divided-by-4 light receiving unit corresponds to the shift quantity of the objective lens. The shift signal for indicating the objective lens shift quantity is calculated based on the output of the divided-by-4 light receiving unit, whereby the shift signal for indicating the objective lens shift quantity can be obtained.
Consequently, a position of the objective lens can be detected without providing the lens position sensor. It is therefore possible to reduce a weight of the optical head and speed up a seeking process. Further, since the lens position sensor may not be provided, costs for the optical head can be decreased.
Other features and advantages of the present invention will become readily apparent from the following description taken in conjunction with the accompanying drawings.
REFERENCES:
patent: 4841508 (1989-06-01), Kimura
patent: 4866688 (1989-09-01), Ohtake et al.
patent: 4924455 (1990-05-0
Fujitsu Limited
Greer Burns & Crain Ltd.
Psitos Aristotelis M.
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