JP3800534B2 - Information recording device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an information recording apparatus that records information by irradiating light onto an information recording medium, and more particularly to an information recording apparatus that can appropriately control the intensity of light.
[0002]
[Prior art]
Conventionally, when recording is performed by irradiating an information recording medium (for example, DVD-RW) capable of recording / erasing information with laser light, two methods have been adopted in order to keep the intensity of the laser light constant. Yes. One of them is a method of detecting a temperature change of a laser diode that emits laser light and supplying a current corresponding to the temperature change. The other is a method in which a front monitor for detecting the intensity of the laser beam is provided, the detection signal from the front monitor is peak-held, and the peak value is controlled to be constant.
[0003]
[Problems to be solved by the invention]
However, in the former method, a representative value is used as the luminous efficiency that changes according to the temperature of the laser diode, and open control based on the representative value is executed. Therefore, the variation in the characteristics of the laser diode is directly reflected as the variation in the light intensity control. It is reflected, and the accuracy of light intensity decreases. Particularly at high speed recording, the light intensity greatly affects recording characteristics, which is a serious problem.
[0004]
In the latter method, there is no problem in accuracy because feedback control can be performed using the peak hold function. However, the circuit scale for peak hold becomes large, which is disadvantageous in terms of cost.
[0005]
An object of the present invention is to provide an information recording apparatus that can accurately control the intensity of light applied to an information recording medium and is excellent in cost.
[0006]
[Means for Solving the Problems]
An information recording apparatus according to the present invention includes a light irradiating unit that irradiates an information recording medium with light to form a recording mark corresponding to the information on the information recording medium and records the information, and an irradiation from the light irradiating unit. Detecting means for detecting the intensity of the emitted light, a low-pass filter to which the output signal of the detecting means is input , and at least one of the recording mark of 11T or the recording mark of 14T is formed on the information recording medium Only when the low-pass filter is operated, sampling means for sampling the output signal of the low-pass filter, and the light irradiation means based on the output signal of the low-pass filter sampled by the sampling means. And control means for controlling the intensity of light to be irradiated.
[0021]
DETAILED DESCRIPTION OF THE INVENTION
-First embodiment-
Hereinafter, a first embodiment of the information recording apparatus of the present invention will be described with reference to FIGS. 1 is a block diagram showing a configuration of a light irradiation control unit in the information recording apparatus of the first embodiment, FIG. 2 is a block diagram showing a configuration of a laser diode control unit, and FIG. 3 is a waveform of a current supplied to the laser diode. FIG. 4 is a timing chart showing waveforms at various parts of the apparatus.
[0022]
As shown in FIG. 1, the information recording apparatus of the first embodiment detects a laser diode LD that irradiates an optical disc (not shown) with laser light, and the intensity of light emitted from the front emission surface of the laser diode LD. The front monitor diode FMD that performs detection, the head amplifier 1 that amplifies the detection signal of the front monitor diode FMD, the low-pass filter 2 that includes the primary passive circuit that receives the output signal of the head amplifier 1, and the output signal of the low-pass filter 2 A sample / hold unit 3 to hold, a voltage control unit 5 in which an output voltage is set based on a sampling value output from the sample / hold unit 3, and a laser diode LD supplied to the laser diode LD based on the output voltage of the voltage control unit 5 And a laser diode control unit 6 for controlling a current value to be performed. The output of the low-pass filter 2 is connected to a semiconductor switch 7 for switching the operation / non-operation of the low-pass filter 2, and the sample / hold unit 3 receives a signal from a timing generation unit 8 that generates a sampling timing. The For details of the optical system necessary for irradiating the optical disk with the laser light emitted from the laser diode LD, refer to the description of JP-A-2000-21001.
[0023]
FIG. 2A and FIG. 2B show cases where the laser diode control unit 6 is configured by an analog method and a digital method, respectively. In the example of FIG. 2A, the laser diode control unit 6 supplies a current to the laser diode LD based on the voltage of the output signal of the switch unit 61a that performs switching according to the write signal and the voltage control unit 5. A laser diode driver IC 61 including a voltage / current conversion unit 61b is provided. The write signal is generated based on the NRZI signal and is given to the switch unit 61a. In the configuration of FIG. 2A, the current from the constant current source given through the switch unit 61a and the current output from the voltage / current conversion unit 61b are added and supplied to the laser diode LD.
[0024]
On the other hand, in the example of FIG. 2B, the laser diode controller 6A includes a laser diode driver IC 62 and a microcomputer 63 that receives an output signal of the voltage controller 5. The driver IC 62 includes a switch unit 62a that performs switching according to a write signal, a modulation unit 62b that generates a write signal based on the NRZI signal, and a D / A that converts a serial signal from the microcomputer 63 into an analog signal voltage. A converter 62c and a voltage / current converter 62d for supplying a predetermined current to the laser diode LD based on the analog signal voltage from the D / A converter 62c are provided.
[0025]
Here, the microcomputer 63 performs analog / digital conversion on the output signal of the voltage control unit 5 and outputs it to the D / A conversion unit 62 c of the driver IC 62. The output voltage value of the D / A converter 62c is converted into a current value by the voltage / current converter 62d. In the configuration of FIG. 2B, the current from the constant current source provided via the switch unit 62a and the current output from the voltage / current conversion unit 62d are added and supplied to the laser diode LD.
[0026]
FIG. 3A illustrates the waveform of the write signal in FIGS. 2A and 2B. FIG. 3A shows a write signal for writing new data to the DVD-RW while erasing recorded data. A laser beam with an erasing level EL is applied to a portion where a recording mark is not formed. The recorded data is erased by irradiation. In the example of FIG. 3A, a new data write portion includes a top pulse P1 having a wide recording level WL, and between the recording level WL and the reproduction level RL following the top pulse P1. The changing pulse train P2 is arranged side by side, but the length (3T to 14T) of the recording mark formed on the disk is controlled by changing the number of pulses (0 to 11) of the pulse train P2. .
[0027]
Next, the operation of the information recording apparatus of the first embodiment will be described.
[0028]
When the laser diode LD emits light and the light is irradiated onto the disk, a recording mark corresponding to the irradiated light is formed on the disk. As shown as “FMD signal” in FIG. 4A, the emission intensity of the laser diode LD is always detected by the front monitor diode FMD. The output signal of the front monitor diode FMD is amplified by the head amplifier 1 and input to the low-pass filter 2, and the operation / non-operation of the low-pass filter 2 is switched by the switch 7.
[0029]
As shown in FIG. 1, a 14T mark whose state changes at the timing of recording a signal having a predetermined length (according to this embodiment, a recording mark having a length of 14T, that is, a synchronization signal) is input to the switch 7. Is done. Therefore, the switch 7 is turned off while the synchronization signal is written, and the low-pass filter 2 is set to the operating state. The synchronization signal is selected as a signal having a predetermined length because it has the longest length in the write signal, the output signal of the low-pass filter 2 converges, and the synchronization signal is always at a predetermined interval. This is because the emission control of the laser diode LD can be stably performed as described later. Then, during the time other than the time when the sync signal is written, that is, while the recorded data is erased and the record mark having a length other than 14T is written, the switch 7 is always turned on, and the output of the low-pass filter 2 is set to the reproduction level. The low-pass filter 2 is set to a non-operating state in accordance with the signal level (−V ₁ ) obtained when the RL laser beam is irradiated.
[0030]
While the low-pass filter 2 is operating, as shown as “post-LPF signal” in FIG. 4A, the output signal of the low-pass filter 2 converges from the −V ₁ level toward a constant value in the minus direction. . The output signal changes in the negative direction because the head amplifier 1 is constituted by an inverting circuit. On the other hand, after a predetermined time has elapsed from the rise of the 14T mark, a timing signal indicated as “S / H” in FIG. 4A is output from the timing generation unit 8 to the sample / hold unit 3, and the “H” period of this signal is output. Accordingly, the output signal of the low-pass filter 2 is sampled by the sample / hold unit 3, and this sampled value is held during the “L” period of the S / H signal.
[0031]
Next, the voltage control unit 5 generates a predetermined voltage based on the sampling value sampled in the sample / hold unit 3, and this voltage is input to the laser diode control unit 6. The laser diode control unit 6 feedback-controls the current supplied to the laser diode LD based on the voltage from the voltage control unit 5, thereby controlling the emission intensity of the laser diode LD to be constant.
[0032]
As described above, in the first embodiment, only the detection signal of the front monitor diode FMD is extracted by operating the low-pass filter 2 only during writing of the recording mark having a length of 14T. It is possible to accurately detect and control the intensity of the irradiated light.
[0033]
This point will be further described with reference to FIGS. 4B and 4C. FIG. 4B shows the waveforms shown in FIG. 4A in the same order when the low-pass filter 2 is always operated. As shown in FIG. 4B, when the low-pass filter 2 is always operated, the emission intensity of the laser diode LD maintained at the erase level and the laser diode LD in the writing state There is no significant difference between the light emission intensities with respect to the output signal of the low-pass filter 2. That is, as shown in the waveform of the output signal of the low-pass filter 2 in FIG. 4B, the level of the output signal of the low-pass filter 2 at the time of writing a recording mark having a length of 14T is before or after that. There is no big difference with the signal level. For this reason, it becomes difficult to detect and control the light emission intensity of the laser diode LD based on the output signal level of the low-pass filter 2.
[0034]
As shown in FIG. 4C, if it is not necessary to irradiate a laser beam for erasing as in writing to DVD-R instead of DVD-RW, the length is 14T. Since the output signal level of the low-pass filter 2 changes in accordance with the write timing of the recording mark, the emission intensity of the laser diode LD can be detected based on the output signal of the low-pass filter 2 as in this embodiment. It can be seen that the emission intensity of the laser diode LD can be detected without applying the configuration of the present embodiment. In FIG. 4C, the waveforms shown in FIG. 4A are shown in the same order.
[0035]
As described above, in this embodiment, the low-pass filter 2 is operated only when a recording mark having a length of 14T is written, so that the emission intensity of the laser diode LD is correctly reflected in the output signal of the low-pass filter 2. Can do. For this reason, the light emission intensity of the laser diode LD can be accurately controlled. In addition, according to the present embodiment, a circuit for peak hold or the like is not necessary, so that the circuit scale can be suppressed and the cost of the apparatus can be reduced.
[0036]
According to the first embodiment described above, the low-pass filter 2 is in an operating state while writing the synchronization signal, but while writing a signal of another length in the write signal, such as an 11T recording mark, Of course, the low-pass filter 2 may be in an operating state. Further, the present invention is not limited to the time of writing a record mark of one length. For example, the low-pass filter 2 operates while writing a record mark of a different length such as an 11T record mark and a 14T record mark. It is good also as a state. Further, as a detecting means for detecting the light intensity of the laser diode LD, the front monitor diode FMD is used. However, as described in Japanese Patent Laid-Open No. 05-21883, the light emitted from the rear emission surface of the laser diode LD is used. A back monitor diode BMD that detects the intensity can also be used.
[0037]
-Second Embodiment-
Next, a second embodiment of the information recording apparatus of the present invention will be described with reference to FIGS. The information recording apparatus according to the second embodiment is an apparatus applied to writing data to a DVD-R that is an information recording medium capable of only adding information.
[0038]
FIG. 5 is a block diagram showing a configuration of a light irradiation control unit in the information recording apparatus of the second embodiment, FIG. 6 is a timing chart showing waveforms of each part of the apparatus, and FIG. 7 is a timing chart showing another operation example. In addition, the same code | symbol is attached | subjected to the component same as 1st Embodiment, and the description is abbreviate | omitted.
[0039]
As shown in FIG. 5, the information recording apparatus of the second embodiment includes a band switching unit 9 that switches the filter band of the low-pass filter 2. The sample / hold unit 3 receives a signal from the timing generation unit 8A.
[0040]
As shown in FIG. 5, the information recording speed (recording transfer speed) is input to the band switching section 9 and the timing generation section 8A. Further, the 14T mark is input to the timing generation unit 8A during a period in which a recording mark having a length of 14T is written.
[0041]
In the information recording apparatus of the second embodiment, the recording speed (for example, 1 × and 2 ×) can be switched, and the filter band of the low-pass filter 2 is switched corresponding to the switching of the recording speed. ing. Further, the sampling timing in the sample / hold unit 3 is switched so that the output signal of the low-pass filter 2 can be appropriately sampled in accordance with the switching of the filter band of the low-pass filter 2.
[0042]
As described above, by simultaneously switching the filter band of the low-pass filter 2 and the sampling timing in the sample / hold unit 3 according to the recording speed, the operation for detecting the light emission intensity of the laser diode LD is always appropriate even if the recording speed is different. Can be maintained. For this reason, the light emission intensity of the laser diode LD can be accurately controlled regardless of the recording speed.
[0043]
Instead of simultaneously switching the filter band of the low-pass filter 2 and the sampling timing in the sample / hold unit 3, only one of them may be switched.
[0044]
Note that when the low-pass filter 2 is set to a high-speed filter band, the output signal of the low-pass filter 2 includes undulations derived from the output signal of the original laser diode LD. For this reason, it is possible to detect and control the emission intensity of the laser diode LD more accurately by switching the filter band and setting the sampling timing to a timing at which such undulation is reduced.
[0045]
FIG. 6 (a) shows the waveform of each part of the apparatus when the recording band is set to 1 × when the recording speed is 1 ×, and FIG. 6 (b) is the recording speed is 2 × when the recording speed is 1 ×. The waveform of each part of the apparatus when set to the filter band for use is shown.
[0046]
Here, the output waveform of the low-pass filter 2 shown in FIG. 6 (b) has a larger amplitude swell than in the case of FIG. 6 (a), and the sampling timing is set in the same manner as in FIG. 6 (a). If set, the light emission intensity of the laser diode LD cannot be accurately detected due to the influence of the undulation.
[0047]
Therefore, as shown in FIG. 7, by shifting the sampling timing before the case of FIG. 6A, the output signal of the low-pass filter 2 can be sampled with less undulation timing, and therefore the laser It becomes possible to detect and control the light emission intensity of the diode LD more accurately. In FIG. 7, the timing signal (S / H) in the case of FIG. 6A is indicated by a dotted line, and the timing signal (S / H) after the timing is shifted forward is indicated by a solid line.
[0048]
Further, as shown in FIG. 7, the amplitude of the swell included in the output signal of the low-pass filter 2 is small before the output signal of the low-pass filter 2 converges to a certain value. As described above, not only in the second embodiment, but also in that the output signal of the low-pass filter 2 is sampled when the undulation of the low-pass filter 2 is small and the filter band of the low-pass filter is switched according to the recording speed. This embodiment and other cases can be similarly adopted.
[0049]
The present invention is not limited to the above-described embodiments. For example, according to the first embodiment, the DVD-RW is used as the information recording medium, but other recording media such as a DVD-RAM and a CD-RW may be used.
[0050]
As described on the following, according to the information recording apparatus of the present invention, only during the formation of at least one of the recording marks of 11T recording mark or 14T of. Thus the low-pass filter 2 to the operating state, The intensity of light emitted from the laser diode LD can be accurately controlled. Further, according to this information recording apparatus, since a circuit for peak hold and the like are not required, the circuit scale can be suppressed and the cost of the apparatus can be reduced.
Also, according to the information recording apparatus of the present invention, the filter band of the low-pass filter 2 is switched in accordance with the recording speed of information on the information recording medium, so that an appropriate output signal of the low-pass filter 2 is always output even if the recording speed changes. The intensity of light emitted from the laser diode LD can be controlled with high accuracy .
Et al is, according to the information recording apparatus of the present invention, the information recording since switching the sampling timing of the sample / hold unit 3 in accordance with the recording speed information to the medium, always appropriate low-pass filter recording speed also vary 2 Sampling output signal can be obtained, and the intensity of light emitted from the laser diode LD can be controlled with high accuracy .
[Brief description of the drawings]
FIG. 1 is a block diagram illustrating a configuration of a light irradiation control unit in an information recording apparatus according to a first embodiment.
FIG. 2 is a block diagram showing a configuration of a laser diode control unit.
FIG. 3 is a diagram showing a waveform of a current supplied to a laser diode.
FIG. 4 is a timing chart showing waveforms at various parts of the apparatus.
FIG. 5 is a block diagram showing a configuration of a light irradiation control unit in the information recording apparatus of the second embodiment.
FIG. 6 is a timing chart showing waveforms at various parts of the apparatus.
FIG. 7 is a timing chart showing another operation example.
[Explanation of symbols]
LD Laser diode (light irradiation means)
FMD front monitor diode (detection means)
2 Low-pass filter 3 Sample / hold section (sampling means)
5 Voltage controller (control means)
6 Laser diode controller (control means)
7 Switch (Switch means)
8 Timing generator (sampling timing switching means)
9 Band switching part (band switching means)

Claims (5)

A light irradiation means for forming a recording mark corresponding to information on the information recording medium by irradiating the information recording medium with light, and recording the information;
Detection means for detecting the intensity of light emitted from the light irradiation means;
A low-pass filter to which an output signal of the detection means is input ;
Switch means for operating the low-pass filter only while at least one of the 11T recording mark or the 14T recording mark is formed on the information recording medium;
Sampling means for sampling the output signal of the low-pass filter;
Control means for controlling the intensity of light emitted from the light irradiation means based on the output signal of the low-pass filter sampled by the sampling means;
An information recording apparatus comprising: The information recording medium is a rewritable recording medium in which recorded information is erased by light irradiated from the light irradiation means,
The information recording apparatus according to claim 1, wherein the light irradiating unit records new information while erasing information recorded on the information recording medium.   The light emitted when erasing information recorded on the information recording medium is weaker than the light emitted when recording the new information on the information recording medium. The information recording device described.   The information recording apparatus according to claim 1, further comprising a band switching unit that switches a filter band of the low-pass filter in accordance with a recording speed of information with respect to the information recording medium. 5. The information recording apparatus according to claim 1, further comprising a sampling timing switching unit that switches a sampling timing of the sampling unit according to a recording speed of information on the information recording medium.

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