Dynamic information storage or retrieval – Control of storage or retrieval operation by a control... – Mechanism control by the control signal
Reexamination Certificate
2001-05-21
2003-01-07
Edun, Muhammad (Department: 2653)
Dynamic information storage or retrieval
Control of storage or retrieval operation by a control...
Mechanism control by the control signal
C369S059110, C369S116000
Reexamination Certificate
active
06504803
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an optical disk apparatus for recording and reproducing information on an optical disk.
2. Related Background Art
In recent years, optical disks have become the mainstream for information recording media with large storage capacity, as used for example for data of multi-media applications. In order to increase their capacity even further, optical disks with high density storage capability (referred to in short as “high-density disks” in the following) are being proposed continuously.
The main strategies in achieving higher densities are making the recording marks shorter and making the track pitch narrower. However, as the densities increase, changes in the focusing condition of the light beam due to defocusing or tilting of the disk during recording or reproduction exert a greater influence on the signal quality, such as the S/N ratio for example. Therefore, it is preferable to record at a laser power in which the decrease of the equivalent laser power due to the change in the focusing condition is compensated.
With regard to this problem, a method has been proposed, that detects the minimum recording power for forming reproducible recording marks (that is, at the reproducible limit) on the optical disk (referred to as “minimum recording power” or “Pmin” in the following), and that sets the laser power used for recording data to an optimum recording power obtained by multiplying this Pmin by a certain factor (see for example, JP H03-232141A).
The following is an explanation of an example of such a conventional optical disk apparatus, with reference to the accompanying drawings.
FIG. 18
is a block diagram illustrating the configuration of a conventional optical disk apparatus. In
FIG. 18
, numeral
1
denotes an optical disk, numeral
2
denotes a spindle motor for rotating the optical disk
1
, and numeral
3
denotes an optical head focusing laser light on the optical disk
1
and detecting recorded information from the light reflected by the optical disk
1
. Numeral
4
denotes a laser power control portion, which sets the laser power depending on information input from a control portion
9
explained below, and numeral
5
denotes a magnetic head for the recording of signals. Numeral
6
denotes a band-pass filter (BPF), and numeral
7
denotes a detector for detecting the strength of the reproduction signal. Numeral
8
denotes a minimum recording power detection portion for detecting Pmin. Numeral
9
is a control portion, which controls the spindle motor
2
, the optical head.
3
, the laser power control portion
4
, and the magnetic head
5
and sets the optimum recording power.
The following is an explanation of the operation of an optical disk apparatus with the above configuration.
To set the laser power used for the recording of data, first, the laser power control portion
4
sets the power based on information from the control portion
9
. The control portion
9
controls the optical head
3
and the magnetic head
5
, and lets them record a single-frequency signal on the optical disk
1
. Then, this signal is reproduced with the optical head
3
, and after band limiting with the band-pass filter
6
, which has a pass band including the recorded frequency, the signal strength of the output signal is detected with the detector
7
and input into the minimum recording power detection portion
8
.
Repeating this operation while changing the value to which the recording power is set leads to a dependency of the reproduction signal intensity on the recording power as shown in FIG.
19
. The minimum recording power detection portion
8
detects Pmin by approximate calculation from the recording power dependency shown in FIG.
19
. The detected Pmin is input into the control portion
9
. Multiplying Pmin by a factor and taking the resulting value as the optimum recording power, the control portion
9
sets the laser power used for the recording of data, thus making it possible to preserve constant recording conditions, even when the focusing of the light beam or the temperature of the optical disk change.
However, in this configuration, Pmin is detected using the signal strength of the reproduction signal, so that Pmin has to be detected in regions in which no data has yet been recorded. Therefore, the detection of Pmin has to be performed in a predetermined region provided on the optical disk as a power setting region for example, or, if the detection of Pmin is performed in the data recording region, then the data recorded in that region have to be deleted beforehand. In the former case, the space on the optical disk that cannot be used for the recording of data increases, so that the data recording capacity decreases, whereas the latter case causes a rotational delay for deleting the data and the detection of Pmin takes extra time, and furthermore, there is the risk that during the deletion, the data on neighboring tracks are deleted as well (cross-erasing).
SUMMARY OF THE INVENTION
It is an object of the present invention to provide an optical disk apparatus, wherein, when taking a data recording region as the region for detecting the minimum recording power, it is not necessary to delete beforehand data that are recorded in that region, and in which Pmin can be detected with high precision and in a short time.
In order to attain this object, in accordance with the present invention, a first optical disk apparatus for recording and reproducing data by irradiating a light beam onto an optical disk includes a recording portion for recording information on the optical disk; a laser power control portion for controlling a laser power of the recording portion; a reproduction portion for reproducing information recorded on the optical disk; a correlation detection portion for detecting a correlation between a recording pattern to be recorded on the optical disk by the recording portion and a reproduction signal obtained when the recording pattern is reproduced by the reproduction portion; and an optimum recording power setting portion which detects a minimum recording power at which reproducible recording marks are formed on the optical disk, and sets an optimum recording power to a power obtained by multiplying this minimum recording power by a recording compensating factor; wherein the optimum recording power setting portion compares a predetermined level with an output by the correlation detection portion that is obtained when the laser power is changed stepwise by the laser power control portion, detects as the minimum recording power the recording power when the originally smaller of the predetermined level and that output by the correlation detection portion becomes larger than the other, and sets the optimum recording power.
In this first optical disk apparatus, it is preferable that the optimum recording power setting portion detects the minimum recording power in a plurality of regions on the optical disk, and sets a common optimum recording power for this plurality of regions.
In this first optical disk apparatus, it is also preferable that the recording of data is interrupted if the optimum recording power setting portion determines, based on the detected minimum recording power, that no suitable optimum recording power exists.
In this first optical disk apparatus, it is also preferable that the recording portion records a recording pattern in which the frequency of “0”s and “1”s when detecting the minimum recording power is substantially equal.
In this first optical disk apparatus, it is also preferable that the recording portion records a different recording pattern each time the minimum recording power is detected.
In order to attain the above-mentioned object, in accordance with the present invention, a second optical disk apparatus for recording and reproducing data by irradiating a light beam onto an optical disk includes a recording portion for recording information on the optical disk; a laser power control portion for controlling a laser power of the recording p
Hino Yasumori
Inoue Takashi
Matsumoto Toshio
Edun Muhammad
Merchant & Gould P.C.
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