JPH103665A - Optical disk device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an optical disk device capable of obtaining an excellent recording/reproducing characteristic and reducing a load applied to a light source by reducing a change in a reproduction C/N depending on a linear velocity. SOLUTION: Recording power PW between the recording power PW and bias power PB is set so as to become high in proportion to the linear velocity as shown by a solid line 11 similar to a usual device in a recording section on an optical disk from the position of the lowest linear velocity V1 to the highest linear velocity V2 . On the other hand, the bias power PB is set so as to become high in proportion to the linear velocity as shown by the line 12 different from the usual device in this case. However, its change rate is set so that a recording modulation degree becomes a fixed value independently of the linear velocity. A reproduction C/N characteristic is improved than the usual device in an area where the linear velocity on the optical disk is late, and the load applied to the light source is reduced.

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, and more particularly to an optical disk device for recording and reproducing information on a recording medium using light.

[0002]

2. Description of the Related Art Heretofore, light emitted from a light source has been focused on an optical disk surface as a recording medium by a converging optical system as a minute spot, and the light intensity of the minute spot is modulated by an information signal to be recorded from a recording amplifier. 2. Description of the Related Art There is known an optical disc apparatus that performs recording, guides reflected light whose light intensity or the like changes according to information recorded on the optical disc to a photodetector, performs photoelectric conversion, and supplies the resulting signal to a reproduction amplifier to reproduce a recorded information signal. ing.

FIG. 4 is a block diagram showing an example of the conventional optical disk device. In the figure, light is emitted from the light source in the optical head device 42 onto the medium surface of the optical disk 41 rotating at a constant angular velocity ω (linear velocity V changes according to the disk radial position r of the spot) in the direction of the arrow. The converged light is condensed by the converging optical system to form a minute spot. At the time of recording, the recording information signal is transmitted to the optical head drive peripheral circuit 43.
After being modulated by the modulator 44 inside, it is input to the recording amplifier 45.

The recording amplifier 45 power-amplifies an input signal and converts it into a current, and analyzes a track address, which will be described later, input from the outside, and adjusts the gain of the amplifier according to a predetermined procedure. And a control unit for variably controlling. The recording information signal that has been power-amplified by the recording amplifier 45 and converted to a current drives a light source such as a laser diode in the optical head device 42 and modulates the light intensity of the emitted light with the recording information signal.

[0005] That is, at the time of recording, the minute spot formed on the medium surface of the optical disk 41 by the emitted light by the recording amplifier 45, the intensity of the light intensity, that is, the upper limit of the optical power at the time of recording (recording power). And the lower limit (bias power). FIG. 5 shows an example of a modulation state of a recording power and a bias power which are modulated and generated as optical power. In the figure, P _max is maximum allowable optical power, P _W is the recording power, P _B represents the bias power.

The light transmitted through the converging optical system in the optical head device 42 is converged as a minute spot on the medium surface of the optical disk 41 to form a recording mark. Here, the optical disk 41 is, for example, a magneto-optical disk, and is made of a magnetic film whose magnetization direction is aligned in a direction perpendicular to the surface of the medium and in the same direction, and a magnetic field is applied to the magnetic film in a certain direction by a magnetic field applying means (not shown). Has been applied.

In this state, when the above-mentioned minute spot is formed on the magnetic film, the spot forming medium portion is locally heated by the heat energy of light and rises to near the Curie temperature, and the magnetic field causes the magnetic film to be heated. Can be reversed, and even if the heating is stopped after that, the magnetization direction can be maintained. However, since the temperature does not rise to near the Curie temperature with the above bias power, no magnetization reversal occurs. In this way, an information signal is recorded depending on whether or not the magnetization direction is reversed.

On the other hand, at the time of reproduction, the optical head device 4
The optical disk 41 is irradiated with light at a constant light intensity that does not cause the above-described magnetization reversal from the optical disk 41, and the light intensity or polarization plane of the reflected light is modulated according to the recording mark. The reflected light is incident on a photodetector in the optical head device 42 and is converted into an electric signal corresponding to the change in the light intensity or the polarization plane. This electric signal is transmitted to the optical head drive peripheral circuit 43.
After being amplified by the reproduction amplifier 46 in the above, it is supplied to the demodulator 47 and converted into reproduction data.

Here, an address (for example, a track address) indicating a position on the medium surface is recorded in a specific recording area on the optical disk 41 in advance, and not only during reproduction but also during recording during this specific area scanning period. Is switched to a reproduction mode, and an address indicating a recording position is reproduced from the specific recording area.

Therefore, at the time of recording, the above address information is supplied to the track address counter 48. The track address counter 48 counts the input address information and supplies it to the recording amplifier 45. The control unit in the recording amplifier 45 determines the recording position of the minute spot based on the input address information, and sets the recording power and the bias power of the amplifying unit in the recording amplifier 45 in accordance with the recording position. Gain). The amplifier in the recording amplifier 45 converts the signal from the modulator 44 into a recording current and amplifies it so that the recording power and bias power based on the set values are output from the optical head device 42. Drive the light source.

FIG. 6 shows the linear velocity dependency of the optical power of the conventional optical disk device controlled as described above. In the drawing, of the recording power P _W and the bias power P _B , the recording power P _W is a solid line 6 in the recording section on the optical disk from the position of the lowest linear velocity V ₁ to the highest linear velocity V _2.
As shown by 1, it is set to increase in proportion to the linear velocity. This is because in a region where the linear velocity is low, the heating period required for forming the recording mark is long, so that the heating temperature required for the magnetization reversal can be obtained even with a relatively weak recording power,
In the region where the linear velocity is high, the heating period required to form the recording mark is short, so the recording temperature may not be enough to achieve the heating temperature required for the magnetization reversal. This is for obtaining a proper heating temperature.

On the other hand, the bias power P _B is 62
Is controlled to a constant value irrespective of the linear velocity.
In FIG. 6, P _m1 indicates an optical power margin of a difference between the allowable maximum optical power P _max and the maximum recording power P _W.

FIG. 7 shows the linear velocity dependence of the recording modulation degree of the conventional optical disk device controlled as described above. Recording modulation factor m is _{(P W -P B) / (} P W + P B) is represented by and the recording power P _W is because being higher in proportion to the linear velocity as described above, the linear velocity of the V ₁ In this case, the recording modulation degree m ₁ is smaller than the recording modulation degree m ₂ when the linear velocity is V ₂ (V ₁ <V ₂ ). Accordingly, as shown by the solid line in FIG. 7, the recording modulation degree changes in proportion to the linear velocity.

FIG. 8 shows a reproduction C / N of an example of an optical disk apparatus.
Fig. 4 shows a linear velocity characteristic diagram. In the figure, the reproduction C / N vs. linear velocity characteristics 81 and 82 fix the recording power and the bias power irrespective of the linear velocity of the optical disk, and adjust the recording modulation degree to m ₂ , m ₁ (m ₁ <m). The reproduced C / N vs. linear velocity characteristics when recording was performed in ₂ ) are shown below. This characteristic 81
As can be seen from FIGS. 82 and 82, under the same linear velocity condition, the larger the recording modulation degree, the better the reproduced carrier power to noise power ratio (C / N). Also, under the same recording modulation degree, the higher the linear velocity, the better the reproduction C / N.

[0015]

However, in the conventional optical disk device, as shown in FIG. 7, since the recording modulation degree is controlled to increase as the linear velocity increases, the reproduction C / N ratio is increased. The linear velocity characteristic changes as indicated by 83 in FIG. For this reason, when the linear velocity is relatively low, the reproduction C / N is relatively poor because the recording modulation degree is low, and when the linear velocity is relatively high, the reproduction C / N is relatively good because the recording modulation degree is high. As shown by 83 in FIG. 8, the reproduction C / N greatly changes depending on the linear velocity.

Further, in the conventional optical disk device, when the linear velocity is high, it is necessary to increase the recording power. Therefore, there is a problem that the maximum recording power is increased more than necessary and the load on the light source is increased.

The present invention has been made in view of the above points,
It is an object of the present invention to provide an optical disk device capable of obtaining a good recording / reproducing characteristic by reducing a change of a reproducing C / N depending on a linear velocity.

Another object of the present invention is to provide an optical disk device capable of reducing the load on a light source.

[0019]

In order to achieve the above object, the present invention takes out a recording current modulated according to an information signal from a recording amplifier, drives a light source, and converts the light emitted from the light source into a converging optical system. Irradiates the medium surface of the optical disk with a constant rotation speed through the
An optical disc device that performs recording by controlling the intensity of light power of a minute spot to be a recording power as an upper limit value and a bias power as a lower limit value of the optical power at the time of recording in a recording amplifier when recording an information signal. Wherein the position of a minute spot on the medium surface of the optical disk is detected, and the recording power and the bias power are variably controlled in proportion to the linear velocity of the optical disk at the detected position.

In the present invention, since the recording power and the bias power are variably controlled so as to be proportional to the linear velocity, when the recording power is P _W and the bias power is P _B , (P _W −P _B ) / The recording modulation degree represented by (P _W + P _B ) can be made not to change much compared to the conventional apparatus in which the bias power is always constant even when the linear velocity changes greatly.

Further, the present invention is characterized in that the recording power and the bias power are variably controlled so as to be set to be constant regardless of the linear velocity of the optical disk at the detection position.

[0022]

Next, embodiments of the present invention will be described with reference to the drawings.

FIG. 1 shows an optical power versus linear velocity characteristic diagram of an embodiment of the optical disk apparatus according to the present invention. As shown in the figure, in this embodiment, of the recording power P _W and the bias power P _B , the recording power P _W is changed from the position of the lowest linear velocity V ₁ to the maximum linear velocity V _{2 in} the recording section on the optical disk. In the same manner as in the conventional apparatus, the setting is made to increase in proportion to the linear velocity as shown by the solid line 11. On the other hand, the bias power P _B is different from the conventional device in this embodiment, and is set so as to increase in proportion to the linear velocity as shown by 12 in FIG.

However, as shown by the solid line 22 in FIG. 2, the rate of change is set so that the recording modulation degree becomes a constant value m ₀ irrespective of the linear velocity. In FIG. 1, _Pm2 indicates an optical power margin of a difference between the maximum allowable optical power _Pmax and the maximum recording power _PW . In FIG. 2, a broken line 21 indicates a conventional recording modulation degree vs. linear velocity characteristic (same as FIG. 7).

Thus, while the recording power P _W sufficient for the recording operation is secured at each linear velocity, the maximum value of the optical power which increases with the linear velocity is assisted by the increase of the bias power P _B. And the margin from the allowable maximum optical power P _max increases to P _m2 (P _m2 > P _m1 ) with respect to the conventional P _m1 . For this reason, the load on the light source can be reduced as compared with the related art.

FIG. 3 is an explanatory diagram of the linear velocity dependence of the reproduction C / N characteristic of an embodiment of the optical disk apparatus of the present invention. In the figure, the reproduction C / N vs. linear velocity characteristics 31, 33 are such that the recording power and the bias power are fixed irrespective of the linear velocity of the optical disk and the recording modulation degree is m ₂ , m
The reproduction C / N vs. linear velocity characteristics when recording at ₁ (m ₁ <m ₂ ) are the same as the characteristics 81 and 82 shown in FIG. As can be seen from these characteristics 31 and 33, under the same linear velocity condition, the larger the recording modulation degree, the better the reproduced carrier power to noise power ratio (C / N). Also, under the same recording modulation degree, the higher the linear velocity, the better the reproduction C / N.

On the other hand, in FIG. 3, the reproduction C / N vs. linear velocity characteristic 32 is a characteristic of one embodiment of the present invention, and the recording modulation degree is a constant value m ₀ (where m ₁ <m) irrespective of the linear velocity. ₀ <
m ₂ ), the above characteristic 3
It shows the same change characteristics as 1 and 33.

As a result, in this embodiment, in a linear velocity region lower than near the intermediate velocity between the linear velocities V ₁ and V ₂ , the reproduction C / N is improved as the linear velocity becomes slower than in the conventional apparatus. Also, in the linear velocity region higher than the vicinity of the intermediate velocity, the reproduction C / N deteriorates as the linear velocity increases as compared with the conventional apparatus.
A better reproduction C / N than N can be obtained.

The block configuration of the present embodiment is shown in FIG.
And the control program of the control unit for controlling the gain of the amplification unit in the recording amplifier 45 based on the reproduction track address information from the track address counter 48 is different from that of the conventional device.

The present invention is not limited to the above embodiment. For example, the present invention variably controls the recording power and the bias power in proportion to the linear velocity as shown in FIG. In addition, the present invention is not limited to the case where the recording modulation degree is constant irrespective of the linear velocity shown in FIG. 2, but may be substantially constant (the recording modulation degree may change very slowly).

[0031]

As described above, according to the present invention,
When the recording power and the bias power are variably controlled so as to be proportional to the linear velocity, and the recording power is P _W and the bias power is P _B , it is expressed by (P _W −P _B ) / (P _W + P _B ). Even if the linear velocity changes greatly,
Since the bias power does not change much as compared with the conventional device in which the bias power is always constant, the reproducing C / N characteristic can be made better in the region where the linear velocity on the optical disk is slower than in the conventional device, and the maximum value of the optical power can be increased. With the help of increased power, it can be reduced compared to before, and the margin from the maximum allowable optical power can be increased compared to before,
The load on the light source can be reduced.

In particular, when the recording power and the bias power are variably controlled so as to be set to be constant regardless of the linear velocity of the optical disk at the detection position, the above-mentioned features can be obtained even more. As a whole, better recording / reproducing characteristics can be obtained as compared with the related art, and the load on the light source can be reduced by suppressing the upper limit value (recording power) of the optical power.

[Brief description of the drawings]

FIG. 1 is an optical power versus linear velocity characteristic diagram of an embodiment of the device of the present invention.

FIG. 2 is a graph showing a relationship between a recording modulation degree and a linear velocity of an embodiment of the apparatus of the present invention and a conventional apparatus.

FIG. 3 is a diagram showing the linear velocity dependence of the reproduction C / N characteristic of an embodiment of the present invention.

FIG. 4 is a block diagram of an example of an optical disk device.

FIG. 5 is a diagram illustrating an example of a recording power and a bias power.

FIG. 6 is a graph showing an optical power versus linear velocity characteristic of an example of a conventional device.

FIG. 7 is a graph showing a relationship between a recording modulation degree and a linear velocity of an example of a conventional apparatus.

FIG. 8 is an explanatory diagram of linear velocity dependence of reproduction C / N of an example of a conventional apparatus.

[Explanation of symbols]

11 Optical Power vs. Linear Velocity Characteristics of Recording Power 12 Optical Power vs. Linear Velocity Characteristics of Bias Power 21 Conventional Recording Modulation Degree vs. Linear Velocity Characteristic 22 Recording Modulation Degree vs. Linear Velocity Characteristic of One Embodiment of the Present Invention 31, 32, 33 Reproduction C / N vs. linear velocity characteristics when recording modulation degree is m _2, m ₀ , m ₁ 41 Optical disk 42 Optical head device 43 Optical head drive peripheral circuit 44 Recording amplifier 45 Reproduction amplifier 46 Demodulator 47 Modulator 48 track address counter P _max allowable maximum optical power P _W recording power P _B bias power P _m1, P _m2 optical power margin

Claims (3)

[Claims] 1. A recording current modulated according to an information signal is taken out of a recording amplifier to drive a light source, and the light emitted from the light source is irradiated on a medium surface of an optical disk having a constant rotation speed through a converging optical system. When recording the information signal by forming a minute spot, the intensity of the light power of the minute spot is adjusted by the recording power, which is the upper limit of the optical power at the time of recording, and the bias power, which is the lower limit, in the recording amplifier. An optical disk device that performs recording by controlling so that the position of a minute spot on the medium surface of the optical disk is detected, and the recording power and the bias power are respectively proportional to the linear velocity of the optical disk at the detected position. An optical disc device characterized by variable control. 2. Assuming that the recording power is P _W and the bias power is P _B , the recording modulation degree represented by (P _W −P _B ) / (P _W + P _B ) is calculated at the detection position. 2. The optical disk apparatus according to claim 1, wherein the recording power and the bias power are variably controlled so as to be set constant regardless of the linear velocity of the optical disk. 3. The optical disk is a magneto-optical disk in which a track address is recorded in a specific area in advance, and a position of a minute spot on a medium surface of the optical disk is detected from the track address reproduction signal. The optical disk device according to claim 1.