Dynamic information storage or retrieval – Control of storage or retrieval operation by a control... – Mechanism control by the control signal
Reexamination Certificate
2000-04-27
2003-02-25
Edun, Muhammad (Department: 2655)
Dynamic information storage or retrieval
Control of storage or retrieval operation by a control...
Mechanism control by the control signal
C369S053100, C369S059100
Reexamination Certificate
active
06526013
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to an optical information recording medium, such as, for example, an optical disk, used for recording and reproducing information optically, an information recording method in which test signals are recorded before the recording of information signals to optimize recording conditions, and an information recording/reproducing apparatus.
BACKGROUND OF THE INVENTION
Recently, as media used for recording information optically, an optical disk, an optical card, an optical tape, and the like have been proposed and developed. Among them, the optical disk has been receiving attention as a medium on which mass information can be recorded with high density and from which the mass information can be reproduced.
One system of rewritable optical disks is a phase-change type optical disk. A recording film used in the phase-change type optical disk is changed to either an amorphous state or a crystalline state depending on a heating condition by a laser beam and a cooling condition. There is reversibility between the amorphous state and the crystalline state. The above-mentioned amorphous state and the crystalline state are different in optical constants (a refractive index and an extinction coefficient) of the recording film. In the phase-change type optical disk, the two states are produced in the recording film selectively according to information signals. By using the optical change (the change in transmittance or reflectance) thus caused, the information signals are recorded and reproduced.
In order to obtain the above-mentioned two states, the following method is used in recording information signals. When a laser beam (with a power level P
p
) focused by an optical head is irradiated onto a recording film of an optical disk in the form of pulse (which is called “a recording pulse”) to increase the temperature of the recording film above its melting point, a molten portion is cooled quickly after the passage of the laser beam to form a recording mark in an amorphous state. On the other hand, when a laser beam (with a power level P
b
, wherein P
b
<P
p
) is focused and irradiated with a power at a level that allows the temperature of the recording film to increase to the temperature above that causing the recording film to change to a crystalline state but below its melting point, the irradiation part in the recording film is changed to a crystalline state. This power level P
b
is called “an erase power”.
Thus, corresponding to a recording data signal, a recording pattern including recording marks formed of amorphous areas and portions with no mark (called “spaces”) formed of crystalline areas is formed on tracks on the optical disk. By utilizing the differences in optical characteristics between the crystalline areas and the amorphous areas, information signals can be reproduced.
Recently, instead of a mark position recording (that also is called “PPM recording”) system, a mark edge recording (that also is called “PWM recording”) system has been increasingly used. In the mark position recording, information is given only to positions of recording marks themselves. On the other hand, in the mark edge recording, information is given to both edge positions at a leading edge and a rear edge of each recording mark, resulting in the advantage of improving recording linear density.
Further, as a method of facilitating rotation control of a spindle motor in a recording/reproducing apparatus while increasing recording capacity in an optical disk, a Z-CLV (Zoned Constant Linear Velocity) format has been proposed. In an optical disk with the Z-CLV format, a recording area is divided into zones including a predetermined number of tracks, and the number of sectors around the disk is increased gradually from a zone in the inner circumference toward that in the outer circumference.
In an apparatus used for recording information on and reproducing information from such a Z-CLV disk, information is recorded or reproduced by reducing the rotation speed of the disk gradually from the inner circumference toward the outer circumference (wherein the rotation speed in each zone is constant) and allowing the linear velocity to be substantially constant throughout all rounds on the disk.
The Z-CLV format is described, for example, as “an M-CLV (modified Constant Linear Velocity) format” in “Optical Disk Technology”, page 223, Radio Technique Co. Ltd., (1988).
Optical disks are exchangeable recording media and therefore recording/reproducing apparatuses for optical disks are required to record information on and reproduce information from a plurality of different optical disks stably. However, even in optical disks manufactured under the same conditions, the optimum power level of a laser beam for recording and reproducing information may be different due to irregularity during the manufacture or aging. Further, because of dirt on the substrate surface of an optical disk, the decrease in transmission efficiency in an optical system or the variation in operation condition in a recording/reproducing apparatus, the power of a laser beam reaching a recording film of the optical disk may vary.
In addition, particularly in the mark edge recording system, the variation in thermal characteristics of an optical disk affects the formation state of recording marks themselves and the degree of the thermal interference between the recording marks. Therefore, the optimum edge positions of recording pulses may be different in each optical disk.
An example of methods of recording and reproducing information signals stably without being affected by such variation in optimum power level of a laser beam or in optimum edge positions of recording pulses as described above has been disclosed in JP 4-137224 A. In the example disclosed therein, after carrying out test recording with a specific data pattern (which is called “a test signal”) prior to the recording of information signals, the test signal recorded is reproduced and edge positions of recording marks are determined by measuring the signal reproduced, thus controlling the edge positions of recording pulses to be optimum.
As another example, JP 6-195713 A discloses a technique in which edge positions of recording marks are determined and then at least one selected from edge positions of recording pulses and recording power is controlled. In JP 9-63056 A, a method for determining an optimum recording power based on the power dependency of a bit error rate has been disclosed. Further, JP 7-129959 A discloses a method of controlling edge positions of recording pulses according to the length of the recording marks and the length of the spaces directly before and after the respective recording marks.
On the other hand, a method of increasing the number of times an optical disk can be rewritten has been proposed in JP 9-219022 A. In this method, by inverting the polarity (1 or 0) of a recording data signal at random, the concentration of damage at specific positions on a recording film is avoided, thus suppressing the deterioration of the recording film.
However, in the aforementioned conventional methods, since measured values of edge positions of recording marks vary, errors in determining edge positions of recording pulses may occur, which has been a problem. This problem will be explained with reference to
FIGS. 11
to 14 as follows.
FIGS. 11
to
14
show examples of mark distortion caused by the position relationship between recording marks that had been recorded previously and recording marks that have been overwritten. Each figure of
FIGS. 11
to
14
shows the state of a track on an optical disk before the overwriting of recording marks in the upper section, a pattern of a test signal (as a recording data signal) to be overwritten in the middle section, and the state of the track after the overwriting of the recording marks in the lower section.
Conventionally, in many cases, a predetermined track is assigned as the track on which recording marks for test recording are to be recorded. In this case, recording marks
Miyagawa Naoyasu
Narumi Kenji
Edun Muhammad
Matsushita Electric - Industrial Co., Ltd.
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