JP3028605B2 - Optical recording device - Google Patents

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical recording apparatus capable of performing high-density recording by removing the influence of residual heat of a recording medium due to a preceding laser light pulse.

BACKGROUND ART Conventionally, there has been known an optical recording apparatus that records data by heating a recording medium using the energy of a laser light beam and changing its magneto-optical properties.

First, a conventional optical recording apparatus will be described with reference to FIG. 1 and FIG.

FIG. 1 shows a configuration example of a conventional optical recording apparatus. For simplicity, description of various servo control circuits is omitted in the conventional example of FIG.

In FIG. 1, (1) is a magneto-optical disk as a data rewritable optical disk, and is rotated at a constant angular velocity or linear velocity by a spindle motor (2). An optical head (10) writes and reads data to and from a magneto-optical disk (1), and a laser diode (11) and a photodiode (12).
Contains. Also, with the magneto-optical disk (1) interposed,
On the side opposite to the optical head (10), a magnetic head (10a) as an external magnetic field supply device is arranged to face the magneto-optical disk (1).

With this configuration, the magnetization direction of the portion of the perpendicular magnetic recording film of the magneto-optical disk (1) irradiated with the laser beam from the optical head (10) is controlled by the external magnetic field supplied from the magnetic head (10a). Is changed depending on the direction.

(20) is a recording circuit system, and a magneto-optical disk (1)
Digital data as an information signal to be recorded on an input terminal IN is supplied from an input terminal IN to an encoder (21), and is converted into a predetermined format by the encoder (21). It is converted into a recording signal. The output of the encoder (21) is supplied to a light intensity modulation circuit (22). The output of the modulation circuit (22) is supplied to a laser diode (11) via a drive amplifier (23), and the emitted light is The intensity is controlled intermittently.

A part of the laser light beam emitted from the laser diode (11) is reflected by the prism mirror, detected by the photodiode (12), and detected by the photodiode (12).
Is supplied to a comparator (25) via an amplifier (24) and is compared with a reference value from a reference value setting circuit (26).
The output of the comparator (25) is fed back to the light intensity modulation circuit (22), the light intensity (power level) of the laser diode (11) is controlled to a constant value, and so-called APC is performed.

Next, formation of a recording area (mark) of the conventional optical recording apparatus will be described with reference to FIG.

The recording linear velocity of the magneto-optical disk (1) is, for example, 10 m / s
In the case of FIG. 2, as shown in FIG. 2A, for example, a laser beam having a pulse width of 50 nS and a power level of 10 mW is emitted from the diode (11), and as shown in FIG. The temperature of the recording layer rises and falls, for example, 180
Although not shown, a mark having a length twice as long as the irradiation pulse width, that is, a time length of 100 nS is formed on the recording layer at the Curie point Tc at ° C. The temperature of the recording layer corresponds to the irradiation center of the laser beam having the energy density of Gaussian distribution, and is also affected by the thermal diffusion of the recording layer.

And in the above example, as is apparent in FIG. 2B,
Since the temperature of the recording layer of the magneto-optical disk (1) has dropped to a value almost equal to that before the irradiation when the length of the mark length is twice as long as the mark length, i.e., 200 nS from the start of the first laser light beam irradiation, The formation of the succeeding mark is not affected by the residual heat at the time of forming the preceding mark, and a modulation method such as pulse position modulation can be adopted without any trouble.

By the way, for high-density recording, the irradiation interval of the laser light beam is set to, for example, 100 n at the same recording linear velocity as in the above-described example.
It is conceivable to form a mark having a length of 1/2 of this irradiation interval, that is, a time length of 50 nS, by setting S to 1/2 of the above example.

In this case, as known in Japanese Patent Application Laid-Open No. 58-212628 and the like by the present applicant, due to the effect of thermal diffusion of the recording layer,
It is necessary to shorten the irradiation pulse width of the laser light beam and increase the power level as compared with the above-described example.
As shown in FIG. A, for example, a laser beam having a pulse width of 15 nS and a power level of 20 mW is emitted from the diode (11), and as shown in FIG. 3B, the temperature of the recording layer of the magneto-optical disk (1) is increased. Rises and falls to the required length of time, ie 50 nS
Mark is formed.

However, in this case, as is apparent in FIG. 3B,
At the time when the length of the mark is twice the mark length from the start of the irradiation of the first laser light beam, that is, at the time when 100 nS has elapsed, the elapsed time after the end of the irradiation is shortened to approximately 1/2 of the above-described example. (1) The temperature of the recording layer only drops to a value about 40 ° C. higher than before the irradiation.

This residual rise temperature, that is, the residual heat at the time of forming the preceding mark is directly added to the temperature rise of the recording layer at the time of forming the subsequent mark as shown by the broken line in FIG. The time required to reach the Curie point Tc is shortened, and the time required to reach the Curie point Tc is prolonged on the temperature decreasing side. As a result, the leading edge and the trailing edge of the mark to be formed are displaced before and after a predetermined time, respectively, so that the required mark is not accurately formed. There was a problem that an error occurred.

DISCLOSURE OF THE INVENTION In view of the foregoing, it is an object of the present invention to cancel out the effect of residual heat of a recording medium due to a laser light pulse corresponding to a preceding signal pulse, and to accurately record a high-density pulse signal. An optical recording device is provided.

An optical recording apparatus according to the present invention provides an optical recording apparatus that supplies a modulation signal based on recording data to a light intensity modulation unit of a laser light source and irradiates a light beam from the laser light source onto an optical disc to perform recording. Light detection means for detecting a light beam reflected from the optical disk; an output from the light detection means is supplied, and a comparison output with a predetermined reference value provided by the reference value setting means is fed back to the light intensity modulation means Comparing means for controlling the intensity of the light beam from the laser light source so as to be constant, and detecting a pulse pattern of a modulation signal based on the recording data and an interval between a signal pulse preceding the succeeding signal pulse. A pattern detection means for generating a detection output when the value becomes equal to or less than a predetermined interval, and an amplitude correction value of the pulse pattern is stored in advance. And a speed setting means for setting a rotation speed of the optical disc, a correction value from the memory means corrected in accordance with a detection output from the pattern detection means and the speed setting means, The amplitude of the subsequent signal pulse is reduced by adding the reference value from the reference value setting means and supplying the result to the comparison means.

Further, the optical recording apparatus of the present invention supplies a modulation signal based on recording data to a light intensity modulation means of a laser light source, and irradiates a light beam from the laser light source to an optical disc to perform recording. A light detecting means for detecting a light beam reflected from the optical disk; an output from the light detecting means being supplied, and a comparison output with a predetermined reference value provided by a reference value setting means being converted to the light intensity modulating means. A comparison means for controlling the intensity of the light beam from the laser light source to be constant by feeding back the signal pulse, and detecting a pulse pattern of a modulation signal based on the recording data and a signal pulse preceding a subsequent signal pulse. A pattern detecting means for generating a detection output when the interval of the optical disk becomes equal to or less than a predetermined interval; and setting a rotation speed of the optical disk. Speed setting means; and pulse width control means for controlling the pulse width of the subsequent signal pulse to be shortened based on the detection output from the pattern detection means and the speed setting means. The pulse pattern corrected by the means is supplied to the light intensity modulating means, and the light intensity is modulated according to the output from the comparing means.

According to this invention, the influence of the residual heat of the recording medium due to the laser light pulse corresponding to the preceding signal pulse is offset,
High-density pulse signals are accurately recorded.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a block diagram showing a configuration example of a conventional optical recording apparatus, FIG. 2 is a time chart for explaining the operation of the conventional example, and FIG. 3 is a time chart for explaining the present invention. FIG. 4 is a block diagram showing the configuration of an embodiment of the optical recording apparatus according to the present invention, FIG. 5 is a time chart for explaining the operation of the embodiment of the present invention, and FIG. FIG. 7 is a block diagram showing a configuration of another embodiment of the present invention. FIG. 7 is a block diagram showing a configuration of a main part of another embodiment of the present invention. FIG. 9 is a graph for explaining the temperature change of the recording medium.

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, an embodiment of an optical recording apparatus according to the present invention will be described with reference to FIG. 4 and FIG.

FIG. 4 shows the configuration of an embodiment of the present invention. This fourth
In the figure, the same reference numerals are given to the portions corresponding to FIG. 1 described above, and redundant description will be omitted.

In the embodiment shown in FIG. 4, reference numeral (20A) denotes a recording circuit system, and a pattern detection circuit (31) for detecting a pulse pattern of a recording signal is provided. The output of the encoder (21) is supplied to a pattern detection circuit (31) and to a modulation circuit (22) via a delay circuit (32) for signal processing time compensation. Reference numeral (33) denotes an amplitude correction memory to which the output of the pattern detection circuit (31) and the output of the recording speed setting circuit (34) are supplied, and the correction value and the reference value setting circuit (26) from the memory (33) are provided. ) Are added by the adder (35) and supplied to the comparator (25). Other configurations are the same as those in FIG.

 The operation of the embodiment of FIG. 4 is as follows.

When the pattern detection circuit (31) detects that the pulse pattern of the recording signal is shorter than a predetermined interval, a correction value stored in advance in the amplitude correction memory (33) is read. Naturally, this correction value needs to be compensated for according to the rotation speed of the disk. Therefore, the correction value is compensated for by the recording speed setting circuit (34) according to the rotation speed of the disk, and then the memory (33) ) Is output.

Based on this correction value and the reference value from the setting circuit (26), the output of the light intensity modulation circuit (22), that is, the intensity level of the emitted light of the laser diode (11) is controlled, As shown in FIG. A, the power level of the subsequent laser light pulse is reduced by pmW.

 The following is a numerical example in the case of power level reduction.

For example, a linear velocity of 10 m / S and a recording frequency of 12.5
When recording at MHz, pulse interval of 80 ns, and pulse width of 15 ns, if the amplitude of the succeeding pulse signal is approximately 83% of the preceding pulse signal at room temperature level, after compensating for the thermal effect of the preceding pulse signal, Can be recorded. The pulse signal further following the subsequent pulse signal may be approximately 81% of the amplitude of the preceding pulse signal.

Note that how much the amplitude of the following pulse signal is corrected to be reduced with respect to the normal pulse signal depends on the recording linear velocity, that is, the rotation speed of the magneto-optical disk, and the temperature at which the recording is performed. It is necessary to change the correction value also depending on the pulse interval between the pulse signal and the subsequent pulse signal. Under the above conditions, the power of the recording beam
FIG. 9 shows a graph when the elapsed time is plotted on the horizontal axis and the temperature of the recording medium of the magneto-optical disk is plotted on the vertical axis when the power is 20 mW. As can be seen from FIG. 9, as the time elapses, the temperature of the recording medium decreases, so that the longer the pulse interval is, the less the thermal influence of the preceding pulse signal is. Therefore, the correction amount of the amplitude of the subsequent pulse signal may be small. As can be seen from FIG. 9, when the pulse interval becomes approximately 160 ns, it is almost unnecessary to correct the amplitude of the subsequent pulse signal.

The numerical values given here are merely examples, and the correction amount of the amplitude of the subsequent pulse signal changes depending on the above-described conditions.

As a result, the temperature rise of the recording layer of the magneto-optical disk (1) due to the subsequent laser light pulse becomes slightly moderate,
As shown in FIG. 5B, at the end of the irradiation of the subsequent laser light pulse, the temperature rise remains the same as the end of the irradiation of the preceding laser light pulse, and the effect of the residual heat of the recording medium due to the preceding laser light pulse is canceled. , A high-density pulse signal is accurately recorded.

Next, another embodiment of the optical recording apparatus according to the present invention will be described with reference to FIGS.

FIG. 6 shows a configuration of another embodiment of the present invention, and FIG. 7 shows a configuration of a main part thereof. In FIG. 6, portions corresponding to FIGS. 1 and 4 are given the same reference numerals, and redundant description will be omitted.

In the embodiment of FIG. 6, reference numeral (20W) denotes a recording circuit system, and a pulse width control circuit (36) for controlling the pulse width of a recording signal is provided. The output of the encoder (21) is supplied to a pattern detection circuit (31) and a delay circuit (3
It is supplied to the pulse width control circuit (36) via 2).
The output of the recording speed setting circuit (34) is also supplied to the control circuit (36), and the output of the pulse width control circuit (36) is directly supplied to the modulation circuit (22). Other configurations are the same as those in FIGS. 1 and 4 described above.

In FIG. 7, reference numeral (60) denotes a pulse width control circuit, which corresponds to the pulse width control circuit (36) in FIG.
Input pulse from the delay circuit (61) and AND gate (6
The output of the delay circuit (61) having a delay time of τ is supplied to the AND gate (62) while being supplied to both 2) and (63) in common. The detection signal from the terminal DT is supplied directly to the AND gate (62), and also via the NOT circuit (64).
It is supplied to the AND gate (63). The output of the AND gates (62) and (63) is connected to the terminal OU via the OR gate (65).
Derived into T.

 The operation of the embodiment of FIG. 6 is as follows.

In the pulse width control circuit (60) of FIG. 7, when the level of the detection signal at the terminal DT is "0", the AND gate (62) is closed, and the AND gate (63) is opened.
The input pulse from IN is led out to terminal OUT as it is.

When the level of the detection signal at the terminal DT is "1", the AND gate (63) is closed and the AND gate (62) is opened, so that the leading edge of the input pulse from the terminal IN is τ. The pulse retreats by time and the trailing edge is not displaced, the pulse width is reduced by τ time, and the pulse is led out to the terminal OUT.

When the pattern detection circuit (31) in FIG. 6 detects that the pulse pattern of the recording signal is shorter than a predetermined interval, the control circuit (36) performs
As described above, for example, as shown in FIG. 8A, pulse width control is performed such that the leading edge of the subsequent laser light pulse is retracted by τ time.

A numerical example in the case of performing the correction for reducing the pulse width is shown below. When recording on a magneto-optical disk with a linear velocity of 10 m / s, a recording frequency of 12.5 MHz, a pulse interval of 80 ns, and a pulse width of 15 ns, the pulse width of the subsequent pulse signal at room temperature level is 12 ns
Then, the recording can be performed after compensating for the thermal effect of the preceding pulse signal.

In this case, similarly to the case of performing the correction for reducing the amplitude of the previous pulse signal, the extent to which the correction for reducing the pulse width of the subsequent pulse signal is performed depends on the recording linear velocity and the temperature at which the recording is performed. Of course, it must also be corrected by the pulse interval. The relationship between the pulse interval and the temperature of the recording medium of the magneto-optical disk is the same as in the case where the correction for reducing the amplitude of the pulse signal is performed.

However, when performing the correction for changing the pulse width, if the width of the pulse signal is widened, the rising of the graph of FIG. 9 becomes non-linear.

As a result, the irradiation time of the recording layer of the magneto-optical disk (1) by the subsequent laser light pulse is shortened, the temperature rise of the recording layer is limited, and as shown by the solid line in FIG. At the end of the irradiation, the temperature rise is the same as that at the end of the irradiation of the preceding laser light pulse, and the effect of the residual heat of the recording medium due to the preceding laser light pulse is canceled, so that a high-density pulse signal is accurately recorded.

In the embodiment of FIG. 6, the leading edge of the succeeding laser light pulse is moved backward by τ time. However, the trailing edge of the succeeding laser light pulse may be moved forward by an appropriate time. The edges of the optical pulse may be displaced by a suitable amount of time to reduce the pulse width.

In each of the embodiments described above, a magneto-optical disk has been described as an example. However, the present invention can be applied to any recordable optical disk, for example, a phase change type rewriting using a chalcogenite thin film. The present invention can also be applied to a recording device that mounts a write-once optical disk using tellurium oxide or tellurium oxide.

As described above in detail, according to the present invention, the pulse pattern of a recording signal is detected, and when the pulse interval is equal to or less than a predetermined value, the amplitude of the subsequent signal pulse is reduced or the pulse width is reduced. An optical recording device that can accurately record high-density pulse signals by reducing the irradiation energy of laser light pulses, thereby canceling the effect of residual heat of the recording medium due to laser light pulses corresponding to the preceding signal pulses. Is obtained.

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-1-169735 (JP, A) JP-A-63-48617 (JP, A) JP-A-64-59633 (JP, A) JP-A-59-1983 24452 (JP, A) JP-A-1-185839 (JP, A) JP-A-59-117743 (JP, A) International publication 91/5341 (WO, A1) European publication 335486 (EP, A1) European patent 289260 ( (EP, B1) (58) Field surveyed (Int. Cl. ⁷ , DB name) G11B 7/00, 7/125 G11B 11/10

Claims (2)

(57) [Claims] An optical recording apparatus for supplying a modulation signal based on recording data to a light intensity modulating means of a laser light source and irradiating an optical disk with a light beam from the laser light source to perform recording. Light detection means for detecting the reflected light beam; and an output from the light detection means is supplied, and a comparison output with a predetermined reference value provided by the reference value setting means is fed back to the light intensity modulation means. Comparing means for controlling the intensity of the light beam from the laser light source to be constant, detecting a pulse pattern of a modulation signal based on the recording data, and setting a predetermined interval between a signal pulse preceding a succeeding signal pulse and a predetermined signal pulse. A pattern detection means for generating a detection output when the following condition is satisfied, and a memory in which an amplitude correction value of the pulse pattern is stored in advance. Means for setting a rotation speed of the optical disk, a correction value from the memory means corrected in accordance with a detection output from the pattern detection means and the speed setting means, and a reference value setting. An optical recording apparatus configured to reduce the amplitude of the subsequent signal pulse by adding a reference value from the means and supplying the result to the comparing means. 2. An optical recording apparatus which supplies a modulation signal based on recording data to a light intensity modulation means of a laser light source and irradiates an optical disk with a light beam from the laser light source to perform recording. Light detection means for detecting the reflected light beam; and an output from the light detection means is supplied, and a comparison output with a predetermined reference value provided by the reference value setting means is fed back to the light intensity modulation means. Comparing means for controlling the intensity of the light beam from the laser light source to be constant, and detecting a pulse pattern of a modulation signal based on the recording data, and setting a predetermined interval between a signal pulse preceding a succeeding signal pulse and a predetermined signal pulse. Pattern detecting means for generating a detection output when the following conditions are satisfied; and speed setting means for setting the rotation speed of the optical disk. And a pulse width control means for controlling the pulse width of the subsequent signal pulse to be reduced based on the detection outputs from the pattern detection means and the speed setting means, wherein the pulse width is corrected by the pulse width control means. An optical recording apparatus, wherein a pulse pattern is supplied to the light intensity modulation means, and the light intensity modulation is performed in accordance with an output from the comparison means.