JPH05225568A - Optical disk device - Google Patents

Abstract

PURPOSE:To perform the optimum recording control corresponding to the sensitivity of a medium and the temperature of a utilization environment on an optical disk device record-controlling in a rewritable recording medium. CONSTITUTION:A signal with a prescribed pattern is formed on a storage medium 12 previously by changing a laser strength variously. Then the prescribed component of the signal of the prescribed pattern is detected by a second harmonic wave component detecting part 14 at a recording time and the strength of a laser beam for recording is decided by control part 16. based on the prescribed component and set to a light source part 13.

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 recording on a rewritable storage medium.
2. Description of the Related Art In recent years, optical discs have a large capacity and can be exchanged for media, and are widely used from filing systems for storing image data to external storage devices of computers that handle code data. Further, as the optical disc device, a rewritable type optical disc device in which the number of times of rewriting is unlimited has been commercialized, from a write-once type that allows a user to record information only once. In addition, the 5-inch and 3.5-inch optical disk devices whose formats have been standardized by ISO (International Standard Organization) are expected to be widely used for personal use.

Regarding the storage capacity of a small rewritable optical disk, higher density is demanded in order to support future next-generation machines and expand the field of application.

[0003]

2. Description of the Related Art Among rewritable optical disks,
Storage capacity of 5 inch diameter and 3.5 inch diameter is 640 M each
B / both sides, 120 MB / one side. However, changes in the computer usage environment due to the graphical user interface represented by window systems in recent years, CPU
Not only power but also significant performance improvement including peripheral circuits such as common bus and IO, and further increase in capacity required for external storage device due to large scale and progress of software and personal database. Therefore, higher recording density is desired.

Conventionally, there are an inter-mark recording method (also referred to as pit position recording) and a mark length recording method (also referred to as pit edge recording) as an information recording method in an optical disk device. Can improve the recording density.

FIG. 12 shows a diagram for explaining a conventional recording method. FIG. 12 shows a recording data sequence "0100" encoded in a format suitable for recording on an optical disc medium.
100000001000 "(FIG. 12 (A)), the pit shape of the inter-mark recording method (FIG. 12 (B)) and the reproduction waveform (FIG. 12 (C)), and the pit shape of the mark length recording method (FIG. 12 (D)) And the reproduced waveform (FIG. 12 (E)).

As shown in FIGS. 12A to 12E, in the mark-to-mark recording, the recording bit "1" is one to one in the recording pit.
In contrast, in the mark length recording, the bit "1" corresponds to the edge of the recording pit. Therefore, in mark length recording, two bits "1" can be represented by one pit, and the recording density can be improved. When recording with the same pit length, the recording density is theoretically doubled. be able to.

By the way, the pits recorded on an optical disk are heated to a certain threshold by a semiconductor laser, and a certain threshold (a Curie temperature of 100 to 200 degrees in the case of a magneto-optical disk, a phase transition temperature in the case of a phase change optical disk). It is formed by exceeding several hundred degrees. Since the time required for the medium temperature to reach the saturation value (temperature time constant) is much longer than the response time to the applied magnetic field for recording data on the magnetic disk, which is a typical file device, The edge position of the recording pit, which should be originally at a predetermined position, fluctuates (edge shift) due to various factors including environmental temperature and medium sensitivity.

Here, FIGS. 13 and 14 are diagrams for explaining the edge shift of FIG. 13 and 1
4 shows changes in mark length when mark length recording is performed. FIG. 13 shows a pattern shift and a steady shift, and FIG. 14 shows a thermal shift.

In FIG. 13A, the pattern shift Δ
P _P is the trailing edge of the recording pit that moves according to the recording pattern, and the steady shift ΔP _C is the change from the predetermined length when the shortest pit is recorded, and varies with medium sensitivity and environmental temperature. The relationship between the recording pulse length and the edge shift in this case is shown in FIG.

Further, in FIG. 14A, the thermal shift ΔP _T is such that the leading edge of the recording pit of the next stage moves due to the influence of heat of the recording pit formed in the preceding stage.
The relationship between the recording pulse interval and the edge shift in this case is shown in FIG.
4 (B).

[0011]

However, the pattern shift ΔP _P and the thermal shift ΔP _T can be prevented by changing the pulse length for driving the semiconductor laser in advance according to the recording pattern to perform recording compensation. Since the steady shift ΔP _C is mixed with various factors, there is a problem that it is difficult to perform optimum recording control.

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to provide an optical disk device which performs optimum recording control in accordance with the medium sensitivity and the usage environment temperature.

[0013]

The above problem is to irradiate a laser beam for recording / reproduction, and is rewritable with a light source section capable of appropriately setting the laser intensity at the time of recording. Prior to normal information recording, a storage medium on which a signal of a predetermined pattern is recorded while variously changing the laser intensity from the light source unit, and a predetermined component of the signal of the predetermined pattern of the storage medium are detected at the time of recording. And a control means for determining and setting the intensity of the laser light emitted from the light source section during recording on the storage medium based on a predetermined component of a signal detected by the detection means. It is solved by configuring.

[0014]

As described above, the laser intensity is variously changed in advance on the storage medium to form a signal having a predetermined pattern. Then, at the time of recording, the predetermined component of the signal of the predetermined pattern is detected by the detection means, the intensity of the laser light for recording is determined by the control means based on the predetermined component, and is set in the light source section.

That is, the optimum laser intensity is re-determined when recording is performed on storage media having different sensitivities or when recording is performed at different environmental temperatures.

As a result, in the mark length recording method for increasing the recording density, the steady shift of the recording pit length is reduced,
It is possible to perform optimum recording control.

[0017]

FIG. 1 is a block diagram of the first embodiment of the present invention. In the optical disk device 11 _A of FIG. 1, reference numeral 12 denotes a storage medium such as an optical disk, which is rewritable and has a predetermined pattern while varying the intensity of laser light emitted from the light source unit 13 prior to normal information recording. Signal (for example, a repetitive signal with a duty ratio of 50%) is recorded.

The light source unit 13 is composed of, for example, a semiconductor laser that emits a laser beam for recording and reproduction, and a laser power setting unit that can appropriately set the intensity of the laser beam.

Reference numeral 14 denotes a second harmonic component detecting unit, which detects a signal of a predetermined pattern recorded in the storage medium 12 in advance.
Detect the second harmonic component. In addition, the detection unit 14 has A
A / D (analog / digital) converter (see FIG. 2) is provided, and the detected signal of the second harmonic component is A / D converted and stored in the storage unit 15. The detection unit 14 and the storage unit 15 constitute detection means (details will be described later).

Reference numeral 16 _A is a control unit which is a control means,
Based on the signal of the second harmonic component stored in the storage unit 15, the optimum value of the intensity of the laser light emitted from the light source unit 13 when recording in the storage medium 12 is determined, and the light source unit 13 is determined.
In the laser power setting section of.

Here, FIG. 2 shows a block diagram of the configuration of the detection unit 14 and the storage unit 15 of FIG. The detection unit 14 includes a bandpass filter 21, a rectification unit (half-wave rectification or full-wave rectification).
22 and an A / D conversion unit 23, and the storage unit 1
A register is used as 5.

The bandpass filter 21 is used for the storage medium 12
Of the signals of the predetermined pattern recorded in advance, only the signal (second harmonic signal) f _{1 having} twice the recording frequency is extracted, and the extracted component is taken in as a spectrum by the rectifying unit 22. This is stored in the register 15 as digital information by the A / D converter 23.

Next, FIGS. 3 to 5 show diagrams for explaining the duty ratio and the frequency spectrum, and FIGS.
The operating principle of will be described. Ideally, the signal pattern with a duty ratio of 50% recorded in advance in the storage medium 12 also has a duty ratio of 50% in the reproduced signal. However, if the laser light intensity is too strong or too weak during recording, the balance of the duty ratio is lost. Therefore, the amount of distortion of the reproduced signal is detected as a difference in duty ratio.

In this case, as is known from the theory of Fourier series, the most remarkable effect of the duty ratio on the frequency spectrum is the second harmonic component twice the fundamental frequency.

In FIGS. 3A and 3B, the reproduction signals are well balanced and the duty ratio is 50% (a / b).
= 0.5) (FIG. 3A), the secondary spectrum f ₁
Becomes zero (FIG. 3 (B)), and the frequency spectrum can be decomposed into a spectrum of an even multiple of the recording frequency as a basic spectrum (first-order spectrum).

In FIGS. 4A and 4B, when the duty ratio collapses to a / b> 0.5 due to medium sensitivity, environmental temperature, etc., a spectrum f _{1 that} is twice the basic spectrum appears. Similarly, when the duty ratio collapses to a / b <0.5 in FIGS. 5A and 5B, the double spectrum f _{1 is obtained.}
Appears.

This double spectrum f ₁ (second harmonic)
Is extracted by the bandpass filter 21 of the detection unit 14 and detected as a spectrum by the rectification unit 22. As a result, the frequency component twice the recording frequency is detected, and the control unit 16 _A
The optimum value of the laser light intensity is determined so that the frequency component of this double is minimized. Then, based on this determination, the intensity of the laser beam is set in the laser power setting section of the light source section 13, and the laser beam having the set value is emitted from the semiconductor laser to the storage medium to record information.

With this, it is possible to perform recording control for setting the optimum laser beam intensity at the time of recording of the exchangeable storage medium in accordance with the variation of the medium sensitivity, the usage environment temperature and the like. That is, in the mark length recording for improving the recording density, the steady shift of the recording pit length (see FIG. 13) can be reduced.

Next, FIG. 6 shows a block diagram of a second embodiment of the present invention. The optical disc device 11 _B of FIG. 6 includes the detection means 14 of FIG.
The pulse width detection unit 32 detects a time difference or a phase difference between the pulses of the binary signal from the binarization circuit 31. Although not shown, the pulse width detection unit 32 has an A / A unit for storing data in the storage unit (register) 15.
A D converter (or sample holder) is provided,
Other configurations are similar to those in FIG.

In this case, the control unit 16 _B controls the laser light emitted from the light source unit 13 so as to minimize the component of the time difference or the phase difference in the pulse width of one cycle of the binary signal from the pulse width detection unit 32. The intensity is determined and set in the laser power setting section.

Here, FIG. 7 shows a diagram for explaining the relationship between the pit length and the reproduction signal. In FIG. 7, a predetermined pattern (duty 50%) previously recorded in the storage medium 12 is used.
When the duty ratio of the reproduction signal of the recording pit) is 50% (a / b = 0.5), it is an ideal state in which the recording pit and the pit interval are equal (FIG. 7A). Further, FIG. 7B shows the case where the recording pits are longer than the pit interval (a / b>
0.5), FIG. 7C shows the case where the recording pits are shorter than the pit interval (a / b <0.5).

That is, the duty ratio is out of balance as shown in FIGS. 7 (B) and 7 (C) due to variations in medium sensitivity and use environment temperature. Therefore, the difference between the duty ratios is binarized by the binarization circuit 31 with the reproduction signal being binarized by the reference potential.
The pulse width detection unit 32 directly detects the time difference or phase difference between the “High” level and the “Low” level with the binarized signal.

Therefore, FIG. 8 is a block diagram showing the principle of the detector 32 shown in FIG. Generally, the data transfer rate of an optical disk is about 1 MB / S, and the maximum recording frequency is several M.
The synchronization of the Hz and binarized signals is around 200 ns. Therefore,
If the counter is used to perform the measurement, the measurement clock used when the frequency range is several MHz is several tens of MH.
From z to several hundred MHz, it is not effective if the measurement logic around the counter and the like is included. Therefore, as shown in FIG.
Use an analog circuit to measure the pulse time.

In FIG. 8, the detector 32 is a constant current source 4
1 and a capacitor C for charging current, and a switch SW1 is interposed therebetween. Further, the switch SW2 and the constant current source 42, and the switch SW3 are connected between the terminals of the capacitor C. In this case, the switches SW1 and SW2 are driven by the binarization signal from the binarization circuit 31, and set the charging time for the capacitor C. The switch SW3 is for discharging the electric charge of the capacitor C and is for ensuring the initial value state.

Although not shown, a mechanism for measuring the charging voltage V _C of the capacitor C is also added.

FIG. 9 shows a graph of the charging characteristics of the capacitor, and the operating principle of FIG. 8 will be described. First, the switch SW3 is turned on once to set the capacitor C to the initial value state. Therefore, the switch SW1 is turned on and the switch SW2 is turned off at the rise of "High" or "Low" of the binarized signal from the binarization circuit 31, and the capacitor from the current from the constant current source 41 is supplied. Charge C.

The charging voltage across the capacitor C in this case becomes V = (I / C) t from Q = CV = It, and is proportional to the charging time t. Then, at the time of the falling of the pulse, this voltage is changed to the sample holder or A
Measure with a / D converter. In this way, by measuring the times of “High” and “Low” of the pulse and obtaining the difference, the duty ratio of the reproduction signal can be accurately measured.

Further, FIG. 10 shows a block diagram constituting a part of the detection unit 32 of FIG. In FIG. 10, the D-flip-flops 43 and 44 are used, and the output of each output Q terminal is extracted by the exclusive OR circuit 45 for one cycle of the binarized pulse.

In this case, each flip-flop 43, 44
A binarized reproduction signal is input to the clock CLK terminal of the. Further, a logic signal such as a start signal is input to the D input terminal of the flip-flop 43, and the flip-flop 43 is input to the D input terminal of the flip-flop 44.
Q output of is input.

Here, FIG. 11 shows a part of the time chart of the detecting section in FIG. 10 for explanation. In FIG.
When the binarized reproduction signal is input after the start signal S is input, the Q output of the flip-flop 43 is set to the “High” level at the first rise. This signal C is input to one input terminal of the exclusive OR circuit 45. At this time, since the "Low" level is input to the other input terminal of the exclusive OR circuit 45, the output becomes the "High" level.

At the next rise of the binarized reproduction signal, the Q output of the flip-flop 44 becomes "High" level, and the output of the exclusive OR circuit 45 becomes "Low".
It becomes a level. As a result, only one cycle of the binarized pulse can be extracted.

By using only one cycle of this binarized pulse in FIG. 8, the measurement can be easily performed.

The difference between the “High” level time and the “Low” level time of the binarized pulse thus obtained by the pulse width detection unit 32 is stored in the data storage unit 15, and this is stored in the control unit 16. _B reads and determines the optimum value of the intensity of the laser light so as to minimize this difference.

Based on this determination, the intensity of the laser beam is set in the laser power setting section of the light source section 13, and the laser beam having the set value is emitted from the semiconductor laser to the storage medium to record information.

With this, it is possible to perform recording control of the exchangeable storage medium so as to set the optimum laser beam intensity at the time of recording, in response to variations in medium sensitivity, usage environment temperature and the like. That is, in the mark length recording for improving the recording density, the steady shift of the recording pit length (see FIG. 13) can be reduced.

In the second embodiment, the case where the duty ratio imbalance is detected by the time difference is shown. However, the same effect can be obtained by detecting the phase difference from the binarized pulse. ..

[0047]

As described above, according to the present invention, the laser intensity is varied in advance in the storage medium to form a signal of a predetermined pattern, and a predetermined component of the signal of the predetermined pattern is detected at the time of recording to detect the laser beam. The intensity of the laser beam can be set according to the medium sensitivity and the temperature of the environment in which the mark is used for high-density recording, and optimum recording control can be performed.

[Brief description of drawings]

FIG. 1 is a configuration diagram of a first embodiment of the present invention.

2 is a configuration block diagram of a detection unit and a storage unit in FIG.

FIG. 3 is a diagram for explaining a duty ratio and a frequency spectrum.

FIG. 4 is a diagram for explaining a duty ratio and a frequency spectrum.

FIG. 5 is a diagram for explaining a duty ratio and a frequency spectrum.

FIG. 6 is a configuration diagram of a second embodiment of the present invention.

FIG. 7 is a diagram for explaining a relationship between a pit length and a reproduction signal.

FIG. 8 is a principle configuration diagram of a detection unit in FIG.

9 is a graph of charging characteristics of the capacitor of FIG.

FIG. 10 is a block diagram of a part of the detection unit of FIG.

11 is a time chart of a part of the detection unit of FIG.

FIG. 12 is a diagram for explaining a conventional recording method.

FIG. 13 is a diagram for explaining the edge shift of FIG.

FIG. 14 is a diagram for explaining the edge shift of FIG.

[Explanation of symbols]

11 _A , 11 _B Optical Disk Device 12 Storage Medium 13 Light Source Section 14 Second Harmonic Component Detection Section 15 Storage Section 16 _A , 16 _B Control Section 21 Bandpass Filter 22 Rectification Section 23 A / D Converter

Claims (8)

[Claims] 1. A light source section (13) for irradiating a laser beam for recording / reproducing, which can appropriately set a laser intensity at the time of recording, and is rewritable, and is a regular information recording. Prior to the above, a storage medium (12) on which a signal of a predetermined pattern is recorded while variously changing the laser intensity from the light source unit (13) and a signal of the predetermined pattern of the storage medium (12) at the time of recording Detection means (14, 15, 31, 3) for detecting a predetermined component
2) and a laser emitted from the light source unit (13) at the time of recording on the storage medium (12) based on a predetermined component of a signal detected by the detection means (14, 15, 31, 32). An optical disk device comprising: a control unit (16 _A , 16 _B ) for determining and setting light intensity. 2. The optical disk device according to claim 1, wherein the signal of the predetermined pattern recorded on the storage medium (12) is a repetitive signal having a duty ratio of 50%. 3. The predetermined component of the signal of the predetermined pattern of the storage medium (12) detected by the detection means (14, 15) is a component of an even multiple of a recording frequency. Alternatively, the optical disk device described in 2. 4. A bandpass filter (21) for selectively extracting a component having twice the recording frequency, and a rectifying unit (42) for detecting the component having twice the recording frequency. 22) The optical disk device according to claim 3, wherein the optical disk device comprises: 5. The intensity of laser light emitted from the light source unit (13) for minimizing the component of twice the recording frequency from the detection unit (14, 15) by the control unit (16 _A ). 5. The optical disk device according to claim 4, wherein 6. The predetermined component of the signal of the predetermined pattern of the storage medium (12) detected by the detecting means (31, 32) is a time difference or a phase difference of the signal width in one cycle of the signal. The optical disk device according to claim 1 or 2, which is characterized in that. 7. A binarization circuit (31) for binarizing the signal of the predetermined pattern at a predetermined level by the detecting means, and detecting a time difference or a phase difference of the pulse width of one cycle of the binary signal. 7. The optical disk device according to claim 6, wherein the optical disk device comprises a pulse width detecting section (32). 8. The light source unit (13) for controlling the control means (16 _B ) so as to minimize a component of a time difference or a phase difference in a pulse width of one cycle of the binary signal from the detecting means.
8. The optical disc device according to claim 7, wherein the intensity of the laser light emitted from the optical disc device is determined.