JP3456827B2 - Optical disk drive - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical disk device for controlling a laser power to an appropriate value when dust or the like is attached on an information recording medium (hereinafter referred to as a disk).

[0002]

2. Description of the Related Art Conventionally, in an optical disk device such as a compact disk using a laser beam, a disk is irradiated with the laser beam to form a mark and the like, and light reflected from the mark is received for recording. The information that is being read is being read.

However, if dust or scratches (hereinafter collectively referred to as dots) are present on the disk, the laser light is reflected or blocked by these dots, so that the mark cannot be normally formed. The problem was pointed out.

However, since there are various dots as described above, it is unclear how much laser power can be used to form a mark. For example, in the case of fingerprints, it is possible to form marks with a relatively small laser power, but in the case of dust, a large laser power is required.

Therefore, the control unit determines the laser power from the reflected light at the time of mark formation so as to obtain the appropriate reflected light by judging the mark formation state (that is, the mark is properly formed). Feedback control to raise a predetermined value is performed. Therefore, in the case of dust, the feedback control may be repeatedly performed.

FIG. 7 is a schematic diagram showing how the laser power is increased by such control. When a mark is formed in the dot area, proper reflected light cannot be obtained, so it is understood that the laser power is gradually increased by a predetermined value. The reason why the laser power becomes a constant value on the way is that either the normal mark formation can be performed with the laser power or the maximum power is reached.

[0007]

However, since the feedback control as described above is performed even when passing through the dots, there is a problem that the laser power does not fall directly to an appropriate value and a predetermined time is required.

That is, the control unit cannot recognize this fact even if it passes through the dots. Therefore, if it is judged from the state of the reflected light that the laser power is large, the laser power should be decreased. Perform feedback control.

At this time, since it is unclear how much laser power should be used to form the mark properly, the above-mentioned feedback control is performed to gradually reduce the laser power so that the laser power becomes appropriate. .

Therefore, a high power section in which a mark is formed with a power higher than an appropriate laser power occurs (see FIG. 7), and a section in which data is missing or abnormal (the section length is referred to as a burst length). There is a problem that the length is longer than the dot length.

In addition, if the dots are dusty, the power is increased to the maximum power, so that the life of the laser diode is shortened.

In this case, it is possible to set the maximum value of the laser power in advance, but it is difficult to set the maximum value because it is necessary to specify the dot type and the like.

Further, the output characteristics of the laser diode are
Since the maximum power of the laser diode fluctuates because it changes due to temperature etc., and the laser power optimum for mark formation changes due to disk warpage, sensitivity unevenness, etc.
It becomes more difficult to set the above-mentioned maximum value.

Therefore, it is an object of the present invention to provide an optical disk device in which the burst length is not longer than the dot length and the laser power is not increased to the maximum power.

[0015]

In order to solve the above problems, the invention according to claim 1 forms a spot of laser light on an information recording medium to write a mark, and detects the reflected light. In the optical disc device including the control unit that detects the writing state and controls the writing power at the time of writing the mark, the control unit forms the mark on the area including dots such as dust and scratches on the information recording medium. When I tried to go,
Detecting means for detecting a signal corresponding to the reflected light and comparing it with a preset threshold value, and a threshold value for presetting a signal corresponding to the reflected light based on the detection signal from the detecting means. The time measuring means is provided with a time measuring means for measuring the smaller time and a judging means for judging whether or not the time measured by the time measuring means is longer than a preset time. When the set time is longer than the preset time, the write power is set to the initial value which is the optimum value.

According to a second aspect of the present invention, the control unit calculates the target value of the writing power at the time of mark formation based on the signal corresponding to the reflected light from the information recording medium, and the upper limit of the target value. And limiting the write power during mark formation to the upper limit, the write power is set to an initial value after a fixed time from that time.

The invention according to claim 3 is characterized in that the control section sets the write power to the initial value by the limiting means, and sets it to the target value after a certain time has elapsed from that time.

According to a fourth aspect of the present invention, the controller controls the detector to detect a signal corresponding to the reflected light from the information recording medium in a case where the signal is smaller than a preset threshold value and in a case where the signal is large. It is characterized in that the upper limit of the target value is set to a different value.

[0019]

[0020]

[0021]

BEST MODE FOR CARRYING OUT THE INVENTION A first embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a block diagram showing a circuit configuration of an optical disk device according to the present embodiment, and FIG. 2 is a CP.
It is a block diagram which shows the circuit structure of U. The laser power at the time of forming the mark is called the writing power, and the laser power at the time of reading the formed mark is called the reading power.

The optical disk device is equipped with an EFM (Eight
The input unit 1 of the to Fourteen Modulation) data signal and the CPU 2 which is a control unit which receives various EFM data signals D1 from the input unit 1 and performs corresponding control.

The data signal which is the basis of the EFM data signal D1 is input to the input unit 1 from a host computer (not shown), and is converted into the EFM data signal D1 by the input unit 1. The EFM data signal D1 contains a fixed trial E
There is an FM data signal Dt and an EFM data signal Dv such as image data.

The CPU 2 sets a new target value LPn for the current laser power through the D / A conversion circuit 6 so as to form a mark while the EFM data signal D1 is at a high level. P
output to the power control circuit 7 and
In synchronization with this, the switch control signal S1 is output to the switch 9.

The switch 9 is based on the switching control signal S1
The movable contact 9a is connected to the fixed contact 9b connected to the APC circuit 7 when the mark is formed, and the movable contact 9a is connected to the APC circuit 10 when the formed mark or land is read and the EFM data signal D1 is at a low level. It operates to connect to the fixed contact 9c that is connected. A DC power supply 11 is connected to the reference input side of the APC circuit 10 on the reading side.
Is supplied with a constant DC voltage E1.

The laser diode circuit 8 includes a switch 9
A signal is input via the, and laser light having a power corresponding to the signal is emitted to the optical system 15.

The optical system 15 includes a front monitor 14 having a photodiode (not shown), a collimator lens (not shown), a beam splitter, an objective lens, a cylindrical lens,
Having a focus actuator and a tracking actuator, the laser light emitted from the laser diode circuit 8 is collimated by the collimator lens to be parallel light, which is condensed through the beam splitter and the objective lens and applied to the disk 5.

At this time, a part of the laser light applied to the disk 5 is output as a front monitor output by the front monitor 14. This front monitor output is proportional to the write power and the read power. The APC circuit 7 controls the write power based on the front monitor output proportional to the write power, and the APC circuit 10
Controls the read power based on the front monitor output proportional to the read power.

The front monitor output proportional to the read power is converted into a digital signal by the A / D conversion circuit 16 and input to the CPU 2 as the read power signal R1.

On the other hand, the reflected light from the disk 5 enters the photodetector circuit 17 having a four-divided photodiode or the like through the optical system 15. The output signal of the photodetection circuit 17 is input to the sample and hold circuit 18 for mark signal detection and the sample and hold circuit 19 for land signal detection, as well as to the reproduction circuit 20.

Well-known focus servo and tracking servo are performed based on the output signal of the photodetector circuit 17, and the output signal S ₀ of the reproducing circuit 20 is output from the output terminal 2.
1 to the waveform observation device.

The clock generation circuit 22 causes the sample and hold circuits 18, 19 to sample and hold pulses SP1, S.
It outputs P2 and outputs a predetermined clock signal to the input unit 1 and the CPU 2.

The mark signal and the land signal output from the sample and hold circuits 18 and 19 are input to the CPU 2 as the mark signal P1 and the land signal L1 via the A / D conversion circuits 23 and 24, respectively.

With the above structure, first, the trial writing area 5a of the disk 5 is used to obtain a constant asymmetry value and to set the writing power to the optimum power.
A fixed EFM data signal for trial Dt is output to.

Then, the CPU 2 outputs the write power target value LP1 predetermined according to the EFM data signal Dt to the D / A conversion circuit 6. The write power target value L
P1 is output to the laser diode circuit 8 through the D / A conversion circuit 6, the APC circuit 7, and the switch 9, and laser light having a laser power corresponding to the write power target value LP1 is emitted from the laser diode circuit 8 to the optical system 15. Is emitted to. As a result, the EFM data signal Dt is displayed in the trial writing area 5a.
A mark having a predetermined length is formed in accordance with the above. The land where the mark is not formed becomes the land.

In this case, the marks and lands formed on the basis of the fixed EFM data signal Dt for the trial document are 3T marks to 11T marks and 3T lands to 11T, respectively.
It is a land, and the number of marks and lands is the same.

Therefore, the asymmetry value of the reproduction signal S ₀ output from the reproduction circuit 20 through the photodetection circuit 17 becomes a constant value.

When the asymmetry value is zero, the center level in the amplitude of the reproduction signal S ₀ coincides with the DC zero level. In other words, when the amplitude of the reproduction signal S ₀ has the same amplitude above and below the zero level, the asymmetry value becomes zero. The state in which the asymmetry value becomes zero is the state in which the write power is optimum.

Therefore, when the asymmetry value is not zero or within the predetermined range, the CPU 2 determines the write power target value LP.
The trial writing process is performed so that 1 is changed and a predetermined asymmetry value is obtained.

As a constant asymmetry value, it is possible to minimize the data error by setting the value within the range of -4% to -7% from the zero value.

The target value LP1 of the write power when the optimum asymmetry value is obtained by the above method is stored in the CPU 2 as the write power initial value LPi (optimal value).

The read power corresponding to the write power initial value LPi, that is, the read power signal R1 output from the A / D conversion circuit 16 to the CPU 2 in response to the front monitor output is set as the read power initial value Ri. It is stored in the CPU 2.

While the mark is formed with the write power having the write power initial value LPi, the reflected light from the 4T mark is sampled and held by the sample and hold circuit 18 based on the sample and hold pulse SP1. The held value is stored in the CPU 2 as the mark initial value Pi of the mark signal via the A / D conversion circuit 23.

Further, when the read power initial value Ri is stored, the reflected light from the land is sampled and held by the sample and hold circuit 19 based on the sample and hold pulse SP2, and the sampled and held value is A / D converted. The initial value Li of the land signal is stored in the CPU 2 via the circuit 24.

Next, laser power control performed by the CPU 2 when dots are present will be described with reference to FIGS. 2 and 3. When a dot 303 such as dust or a scratch is present on a certain track 302 on the disk 5, the reflected light is reduced in the area of the dot 303.

Therefore, the CPU 2 obtains the dot size by the amplitude level detecting section 101 which is the detecting means provided inside and the amplitude decrease time measuring section 102 which is the time measuring means.

FIG. 3 is a diagram for explaining the detection of such an amplitude level detection signal. In FIG. 3, the mark signal P1 and the land signal L1 are represented by the reflected light level.

The mark signal P1 and the land signal L1 corresponding to the reflected light are input from the A / D conversion circuits 23 and 24 to the amplitude level detector 101, and the amplitude level detector 101 compares the amplitude level with a threshold value. To be done. As a result, the amplitude level detection signal is obtained.

Then, the amplitude decrease time measuring unit 102 measures the time during which the amplitude is lower than the threshold value by the amplitude level detection signal. The amplitude reduction time represents the size of the dot through which the light spot passes.

On the other hand, the mark signal P1, the land signal L1 and the read power signal R1 are inputted to the arithmetic unit 104 which is the arithmetic means provided in the CPU 2, and the initial value LPi and the present value of the write power are inputted based on these signals. And a new target value L
Pn is calculated and output to the D / A conversion circuit 6.

Then, the judging unit 103 serving as a judging unit judges whether or not the amplitude decrease time has exceeded the preset judgment time t, and if it exceeds the judgment time, the selecting unit 105 causes the writing power new The target value LPn is changed to the initial value LPi, and this is output as the write power target value LP1.

After that, when the light spot passes through the dots and the amplitude level returns to normal, the target value L of the writing power is immediately reached.
Change P1 to the new target value LPn.

That is, when passing through the dots, the laser power is gradually increased by a predetermined value by feedback control. At this time, the target value LP1 at the next power-up is the new target value LPn.

However, when the time during which the dots pass is longer than the predetermined judgment time t, the power up of the laser power is stopped and the target value LP1 of the write power is set to the initial value LP.
Set to i and output. In such control, since the next target value is not determined by sampling, the write power can be changed immediately.

Therefore, when the dots are larger than a certain size, the laser power is not excessively increased,
Marks can be formed with an appropriate laser power immediately after passing the dots, and it is possible to prevent the burst length such as data loss from becoming longer than the dot length.

A second embodiment of the present invention will be described with reference to the drawings. The same components as those in the first embodiment are designated by the same reference numerals and the description thereof will be omitted. FIG. 4 is a block diagram of the CPU according to the present embodiment, and FIG. 5 is a schematic diagram for explaining the operation thereof.

The CPU 2 according to this embodiment is an A / D
Based on the mark signal P1, the land signal L1 and the read power signal R1 from the conversion circuits 23 and 24, the arithmetic unit 104 calculates the initial value LPi of the write power, the current value and the new target value L.
Pn is calculated and the result is output to the D / A conversion circuit 6.

The maximum value of the new target value LPn of the writing power is the maximum value LPm of the writing power set in the maximum value setting unit 202 (the limiting unit) by the maximum value limiting unit 201 (the limiting unit). Limited to (upper limit).

When maximum value limiting unit 201 detects that new target value LPn of write power has reached maximum value LPm, it starts timer 203.

Then, the new target value LPn of the write power is
When a certain time t1 has elapsed after reaching the maximum value LPm,
The write power target value LPn ′ whose maximum value is limited by the selection unit 204 is changed to the initial value LPi.

After that, when the fixed time t2 elapses, the write power target value LP1 is changed again to the maximum-limited write power target value LPn '.

The length of the fixed times t1 and t2 is determined by the size of dots that can exist on the disk 5.

As described above, when the dots are larger than a certain size, the laser power is not excessively increased,
It is possible to form a mark with an appropriate laser power immediately after passing a dot and prevent a burst length such as data loss from being longer than a dot length.

Further, the CPU does not judge the amplitude level but only manages the time, which simplifies the processing.

A third embodiment of the present invention will be described with reference to the drawings. The same components as those in the above-described embodiment are designated by the same reference numerals and the description thereof will be omitted. FIG. 6 is a block diagram of the CPU according to the present embodiment. In the second embodiment, the new write power target value LPn is set to the maximum value LPn.
Although the case of limiting to m has been described, in general, the maximum value L
Setting Pm is difficult for the following reasons.

That is, when there is no dot on the disk 5 and the laser power is normally forming a mark according to the new target value LPn of the writing power, the laser power changes with the temperature of the laser diode, the warp of the disk 5, and the sensitivity. Since it changes following variations such as unevenness, the new write power target value LPn changes greatly depending on the location and environment where the optical pickup device operates, the characteristics of the disk 5, and the like.

On the other hand, if the maximum value LPm is set too large, the maximum laser power will not reach the maximum value even if the light spot attempts to form a mark on a dot, depending on the place and environment where the optical pickup device operates, the characteristics of the disk 5, and the like. In some cases, dots cannot be detected because LPm is not achieved.

Further, when the dots are dusty, the power is continuously increased, and there is a possibility that the life of the laser may be shortened.

Therefore, in the present embodiment, the amplitude levels of the mark signal P1 and the land signal L1 from the A / D conversion circuits 23 and 24 are compared with a certain threshold value to detect an amplitude level signal (see FIG. 4). Amplitude level detector 1 for outputting
01 is provided, and the maximum value L is detected by this amplitude level detection signal.
Pm was set.

That is, the maximum value LPm is set to a relatively high value in a section where the amplitude level is normal (other than dots), and is set to a relatively low value in a section where the amplitude level is abnormal (dot area). To do.

As a result, when there are no dots on the disk 5 and the laser power normally forms a mark according to the new write power target value LPn, the laser power changes with temperature of the laser diode and the warp of the disk 5. , It is possible to easily follow changes such as variations in sensitivity.

Further, when the light spot tries to form a mark on a dot, if the dot has a certain size or more, the new write power target value LPn reaches the maximum value LPm, and the same effect as the second embodiment is obtained. It will be possible to obtain.

[0073]

According to the first aspect of the invention, when the control section attempts to form a mark in an area including dots such as dust and scratches on the information recording medium, a signal corresponding to reflected light is generated. Detecting means for detecting and comparing with a preset threshold value, and the time when the signal corresponding to the reflected light is smaller than the preset threshold value based on the detection signal from the detecting means. The time measured by the time measuring means and the judging means for judging whether or not the time measured by the time measuring means is longer than the preset time, the time measured by the time measuring means is preset. If the time is longer than the specified time, the initial value, which is the optimum value of the write power, is set, so that it becomes possible to form the mark with the appropriate write power immediately after passing through the dot, resulting in the loss of data. Burst length of etc. It is not necessary to be longer than the length of the dot. In addition, the writing power is set to the initial value when the time during which the signal corresponding to the reflected light is smaller than the threshold value exceeds the preset time. If it does not reach the value, the write power is not set to the initial value, and the write power can be controlled stably.

According to the second aspect of the present invention, the control unit calculates the target value of the write power at the time of mark formation based on the signal corresponding to the reflected light from the information recording medium, and the target value. In addition to limiting the upper limit of the writing power, when it is detected that the writing power reaches the upper limit during the mark formation, a limiting means for setting the writing power to the initial value is provided after a certain time from that time. The writing power will not be excessively increased, and it will be possible to form marks with proper writing power immediately after passing through a dot, and the burst length such as data loss will be longer than the dot length. Disappears. In addition, since the control unit performs only time management, the processing of the control unit is simplified.

According to the third aspect of the invention, the control unit sets the write power to the initial value by the limiting means, and sets it to the target value after a certain time has elapsed from that time. It is possible to form a mark with an appropriate writing power immediately after passing through, and it is possible to prevent the burst length such as data loss from becoming longer than the dot length.

According to the fourth aspect of the present invention, the control section determines whether the signal corresponding to the reflected light from the information recording medium by the detecting means is smaller or larger than a preset threshold value. Since the upper limit of the target value is set to a different value with and, the upper limit of the writing power is selected according to the state of the reflected light, and the mark is formed with the appropriate writing power immediately after passing the dot. Therefore, the burst length due to data loss can be prevented from being longer than the dot length.

[0077]

[0078]

[Brief description of drawings]

FIG. 1 is a block diagram of an optical pickup device applied to the description of an embodiment of the present invention.

FIG. 2 is a block diagram of a CPU applied to the description of the first embodiment.

FIG. 3 is a diagram illustrating a method of detecting an amplitude level detection signal according to the first embodiment.

FIG. 4 is a block diagram of a CPU applied to the description of the second embodiment.

FIG. 5 is a diagram illustrating a change in laser power according to the second embodiment.

FIG. 6 is a block diagram of a CPU applied to the description of the third embodiment.

FIG. 7 is a diagram illustrating a change in laser power applied to the description of the conventional technique.

[Explanation of symbols]

2 CPU 7 APC 101 Amplitude level detector 102 Amplitude decrease time measurement unit 103 determination unit 104 arithmetic unit 105,204 Selector 201 Maximum value limiter 202,301 Maximum value setting section 203 timer 302 Maximum value switching unit

Claims (4)

(57) [Claims] 1. A mark is written by forming a laser beam spot on an information recording medium, and the reflected light is detected to detect the writing state to control the writing power at the time of writing the mark. In an optical disc device including a control unit, the control unit detects a signal corresponding to the reflected light when attempting to form a mark in an area including dots such as dust and scratches on the information recording medium. Detecting means for comparing with a preset threshold value, and measuring the time when the signal corresponding to the reflected light is smaller than the preset threshold value based on the detection signal from the detecting means. A time measuring means; and a judging means for judging whether or not the time measured by the time measuring means is longer than a preset time,
An optical disk device, wherein when the time measured by the time measuring means is longer than a preset time, the write power is set to an initial value which is an optimum value. 2. The control unit limits the upper limit of the target value and a calculation unit that calculates a target value of the write power at the time of forming a mark based on a signal corresponding to the reflected light from the information recording medium. In addition, when it is detected that the writing power during the mark formation reaches the upper limit value, the writing power further includes a limiting means for setting the writing power to the initial value after a fixed time. Optical disk device. 3. The control unit sets the write power to the initial value by the limiting unit, and sets the write power to the target value after a certain time has elapsed from that time. Optical disk device. 4. The target value according to whether the signal corresponding to the reflected light from the information recording medium by the detecting means is smaller than a preset threshold value or is larger than the preset threshold value. 4. The optical disk device according to claim 2, wherein the upper limits of the values are set to different values.