JP2004127513A - Information recording / reproducing device - Google Patents

Abstract

【Task】
Provided is an information recording / reproducing apparatus capable of stably recording / reproducing information data on / from various recording media by using a laser driver capable of performing recording strategy control on various recording media.
[Solution]
A recording current signal corresponding to the NRZ signal can be generated by obtaining the NRZ signal from the modulation circuit 7 and the clock signal chCLK synchronized with the NRZ signal, and oscillating the recording frequency by the PLL circuit 115 disposed inside the laser driver 10. An unlock detection circuit 116 for detecting the oscillation state of the PLL circuit 115 is provided inside the laser driver, and the recording / reproducing operation is controlled by a detection signal from the unlock circuit 116.
[Selection] Fig. 2

Description

The present invention relates to an information recording / reproducing apparatus that records or reproduces information using light emitted from a laser, and in particular, obtains a binarized signal such as an NRZ modulation signal and a clock signal synchronized with the binarized signal and supports the binarized signal. The present invention relates to an information recording / reproducing apparatus having a laser driver capable of generating a recording current signal.

The recording film of the information recording medium is irradiated with a light beam, and recording marks such as drill pits, phase change pits, dye pits or magnetization domains are formed on the recording film to record information, and the reflected light from the recording medium is used. An optical information recording / reproducing apparatus for reproducing information has a feature that a plurality of information recording media (referred to as optical disks) can be used interchangeably, so that a large amount of information can be recorded / reproduced. It is used as a large-capacity external storage device for computers.

In recent years, as recording density has increased, it has been required to form marks (or pits) having a length of, for example, 0.5 μm or less on the surface of an information recording medium. There is a need for power control for dividing (multi-pulse) and further changing the level to multiple values (for example, ternary or quaternary). In addition, in order to optimize the time interval between the recording mark group and the space group between them, adaptively variably control the time position and pulse width of the recording pulse divided according to the adjacent space length and mark length during mark recording Adaptive control of the recording pulse to be performed (hereinafter, this control is referred to as recording strategy control) has become necessary.

行 う In order to perform such a recording strategy control, it is necessary to consider the rising characteristic (Tr) / falling characteristic (Tf) of each pulse of the multi-pulse. In this case, the Tr and Tf characteristics require about several ns. However, when the Tr and Tf characteristics are further increased in response to a higher disk rotation speed due to a demand for high-speed transfer recording, an optical head is required. It is very difficult to transmit the recording pulse waveform to the laser without deteriorating the Tr and Tf characteristics of the recording pulse waveform. In the conventional configuration, the circuit for executing the recording strategy control is arranged on the substrate on the modulation circuit side, and due to the configuration, the transmission distance of the recording pulse waveform from the substrate to the laser of the optical head must be long. Because there was not.

An object of the present invention is to solve the above problems and to provide an information recording / reproducing apparatus capable of high-density recording and high-speed transfer recording.

Another object of the present invention is to provide a laser driver having a circuit for executing recording strategy control that enables recording strategy control for various recording media, and use such a laser driver to record information on an information recording medium. An object of the present invention is to provide an information recording / reproducing apparatus capable of improving the reliability of data recording or reproduction.

要 The gist of the present invention that achieves the above objects is as follows.

(4) A laser driver capable of controlling the recording strategy is arranged close to the semiconductor laser to reduce the deterioration of the Tr and Tf characteristics of the drive current waveform.

This laser driver obtains a binarized signal such as an NRZ modulated signal from a modulation circuit and a clock signal synchronized with the binarized signal, and oscillates a recording frequency by a PLL circuit disposed therein, thereby performing recording corresponding to the binarized signal. A current signal can be generated. However, when the oscillation state of the PLL circuit becomes abnormal, the reference recording frequency becomes abnormal and normal recording cannot be performed. Therefore, a PLL unlock detection circuit that detects the oscillation state of the PLL circuit is installed inside the laser driver, and a detection signal from the unlock circuit is sent as a monitor signal to an arithmetic and control circuit that controls recording and reproduction operations, and the recording operation is controlled. To do.

Here, consider the case where information data is recorded on a CD-R disc. During CD-R recording, in order to detect a servo signal or the like, it is necessary to sample and hold a DC level corresponding to a reproduction power level among pulse-modulated reflected light. This is provided with a delay circuit for adjusting the timing of the NRZ modulation signal from the modulation circuit to the reflected light. In this case, a problem such as cost occurs because the delay circuit is added.

Therefore, based on the above-described present invention, which takes a form in which a binarized signal and a clock signal synchronized with the binarized signal are obtained, and a recording current signal corresponding to the binarized signal can be generated through a delay circuit arranged inside, Further, the output of the delay circuit is sent as a monitor signal to an arithmetic and control circuit that controls the recording operation, and the monitor signal is used to generate a timing signal for sampling / holding the reflected light from the recording medium.

As described above, according to the present invention, high-density recording and high-speed transfer recording become possible.

(4) The reliability of recording or reproducing information data on the information recording medium can be improved.

<First embodiment>
FIG. 1 shows an example of an information recording / reproducing apparatus according to an embodiment of the present invention. An information recording medium 1 on which information is recorded and reproduced is held and rotated by a spindle motor 2. Examples of the recording film forming the information recording medium 1 include a phase change recording film (GeSbTe), an organic dye film, and a magneto-optical recording film (TbFeCo). A semiconductor laser that emits laser light for recording and reproducing information (not shown in the figure), an optical system that forms light from the semiconductor laser as a light spot of about 1 micron on a disk surface, Recording of information on the information recording medium 1 by an optical head 3 having a photodetector 16 for performing reproduction of information using the reflected light from the information recording medium 1 and light point control such as automatic focus and track tracking. Perform playback. The optical head 3 constitutes a linear motor (not shown) that drives and positions the optical head 3 at high speed in the disk radial direction. In the present embodiment, the optical head 3 and the arithmetic / control circuit 6, modulation circuit 7, reproduction circuit 11, and servo control circuit 13 are connected by a signal line such as a flexible cable. Further, the interface control circuit 5, the operation / control circuit 6, the modulation circuit 7, the reproduction circuit 11, the demodulation circuit 12, and the servo control circuit 13 are formed on a circuit board separate from the optical head 3.

Normally, an optical disk device as an information recording / reproducing device conforms to a host computer 4 (hereinafter abbreviated as a host) such as a personal computer or a workstation, and conforms to, for example, SCSI (Small Computer System Interface) and ATAPI (AT Attached Packet Interface) standards. A command including commands and information data from the host 4 is decoded by an interface control circuit 5 in the optical disk device, and information is recorded and reproduced through an arithmetic and control circuit 6 including a microcomputer and the like. And a seek operation.

First, a recording operation in the optical disk device will be described. As for the recording data, a recording command is issued with the recording position information (address information) on the information recording medium 1 added from the host 4, and the recording data is stored in a buffer memory (not shown) in the arithmetic and control circuit 6. After that, the signals are sent to the modulation circuit 7 in time series. In the modulation circuit 7, the recording data is used in a run-length limited (RLL) code, for example, (1, 7) RLL code, (2, 7) RLL code, DVD (Digital Versatile Disk) (2, 10). ) It is converted into a code string corresponding to an RLL code or an EFM (eight-fourteen modulation) code corresponding to a CD format, and further converted to a pulse train (binary signal) corresponding to a mark shape formed on a recording film. These pulse trains (collectively referred to as NRZ signals) are guided to a laser driver 8 or 9 on the optical head 3, and the semiconductor laser is turned on and off in response to the NRZ signal to emit pulse light. A recording mark is formed on the information recording medium 1 by the spot converged in the step (1).

In Fig. 1, two lasers are mounted. The laser D8 is a laser having a wavelength of 650 nm used when recording DVD-related information data (DVD-RAM / -R / -RW + RW), and has an output of 30 mW or more. The laser C9 is a laser having a wavelength of 780 nm used for recording CD-related information data (CD-R / -RW), and has an output of 50 mW or more. In this embodiment, since the laser driver 10 has two output terminals, each of the two lasers can emit light.

Next, a reproducing operation in the optical disk device will be described. At the time of reproduction, a light spot from the optical head 3 is positioned on a track on the information recording medium 1 (for example, a DVD-RAM) specified by a reproduction command from the host 4, and a signal is reproduced from the track. First, when the laser D8 emits DC light via the laser driver 10 on the optical head 3 and irradiates the recording film on the recording medium 1, reflected light corresponding to the recording mark is obtained. Then, the data is reproduced after the light is received and photoelectrically converted and input to the reproduction circuit 11 as an electric signal. Normally, the reproducing circuit 11 includes an automatic gain control circuit (AGC) for keeping the signal amplitude constant, a waveform equalizing circuit (EQ) for correcting optical spatial frequency deterioration, a low-frequency limiting filter (LPF), and a binary signal. It comprises a digitizing circuit, a PLL (Phase Locked Loop) circuit, and a discrimination circuit. After binarizing the reproduced signal, it converts it into discriminated data. The discriminated binary data is input to the demodulation circuit 12 and demodulated in (1, 7) RLL code, (2, 7) RLL code, (2, 10) RLL code or EFM code, and the original data is obtained. Demodulate. The demodulated data is guided to the arithmetic and control circuit 6 and transferred from the interface control circuit 5 to the host 4 in response to a reproduction command from the host 4.

The photodetector 16 in the optical head 3 can detect, in addition to the data reproduction signal, an automatic focus signal for controlling the focus of the light spot on the recording film and a track tracking signal for performing the track tracking control for positioning the light spot on an arbitrary track. The automatic focus signal and the track tracking signal for controlling the light spot are guided to the servo control circuit 13. The servo control circuit 13 includes an error signal generation circuit, a phase compensation circuit, and a drive circuit (all not shown), and performs recording and reproduction of information by positioning the optical head 3 on an arbitrary track.

(2) The laser driver 10 mounted on the optical head 3 will be described in detail with reference to FIG. The serial interface control unit 100 takes in the set values of various registers serially transferred and supplied from the arithmetic and control circuit 6, converts the set values into parallel, and writes the set values to the corresponding registers. SEN is a signal for putting the serial interface control unit 100 into an operating state, SCLK is a clock signal of the serial interface control unit 100, and SDIO is a data signal of the serial interface control unit 100.

The Read-DAC 102 stores the reproduction power level Pread. An HFM (High Frequency Module) 103 superimposes a high-frequency current Ihf on the laser D8 at the time of reproduction, which includes a Pread register 101 and a digital-to-analog conversion circuit that outputs a drive current Iread corresponding to the value of Pread.

The recording current generating unit 105 includes a Pa register 106 for storing the recording power Pa, a Pb register 107 for storing the recording power Pb, a Pc register 108 for storing the recording power Pc, and Pd registers 109, 106 to 109 for storing the recording power Pd. And a Write Power DAC 111 composed of a digital-to-analog conversion circuit that outputs a recording drive current Iwrite corresponding to the recording power value of the selected register.

Also, a Full-Scale DAC 113 composed of a digital-to-analog conversion circuit that outputs a current corresponding to the Pmax value stored in the Pmax register 112 as a reference current Iref of the Write Power DAC 111 is provided. The write strategy control unit 104 determines the timing of the recording power waveform (Pa to Pd registers) based on the NRZ signal (binary signal), the clock signal chCLK, and the control signal WRG for setting the recording / reproducing state supplied from the modulation circuit 7. A control signal Px-select for selection can be generated.

The Write Strategy control unit 104 generates a recording pulse according to the input NRZ signal, and a delay circuit 114 for realizing a recording strategy control for adaptively variably controlling the temporal position and pulse width of the pulse, and an external circuit. And a PLL circuit 115 for supplying a stable recording frequency in synchronization with the clock signal chCLK.

By installing the PLL circuit inside the laser driver 10 instead of the substrate, transmitting the clock signal chCLK at a reduced frequency, and causing the PLL circuit 115 inside the laser driver 10 to oscillate in synchronization with the regular recording frequency, When transmitting a high-frequency signal from the arithmetic / control circuit 6 or the modulation circuit 7 disposed above to the optical head 3 that cannot be disposed on the substrate, an influence on an adjacent signal line (for example, a flexible cable) or a high-frequency signal is transmitted. The influence of unnecessary radiation or the like generated at the time of occurrence can be reduced.

However, the arithmetic and control circuit 6 for controlling the entire optical disc apparatus can determine the abnormality of the clock signal chCLK supplied to the PLL circuit 115 by controlling the modulation circuit 7, but the oscillation state of the PLL circuit 115 inside the laser driver can be determined. The abnormality cannot be determined. Therefore, when the oscillation state of the PLL circuit 115 becomes abnormal, although the clock signal chCLK is normally supplied to the PLL circuit 115, the optical disc apparatus itself determines that the recording is normally performed. However, there is a problem that the recording is not normally performed on the information recording medium 1 normally.

Therefore, an unlock detection circuit 116 for detecting the oscillation state of the PLL circuit 115 is installed inside the laser driver 10, and the monitor circuit 117 uses the detection signal from the unlock detection circuit 116 as a monitor signal to calculate and control the recording / reproducing operation. It can be realized by sending the signal to the circuit 6 and controlling the recording operation.

FIG. 3 illustrates a recording operation in the case where recording is performed using the above-described optical disk device as a DVD-RAM drive and the information recording medium 1 as a DVD-RAM disk. FIG. 3 (i) shows a reproduced signal in a reproducing circuit at the time of recording, where PID (Physical Identification Data) is an address addressed in sector units, DATA1 is recorded data, and DATA2 is a signal by reflected light at the time of recording. Data recording is performed only in the data area of the specified sector number from the top. FIG. 3 (ii) shows the NRZ signal supplied from the modulation circuit 7, which is supplied only to the data area. FIG. 3 (iii) shows a control signal WRG for setting a recordable state, where "L" indicates a recording state and "H" indicates a reproduction state. FIG. 3 (iv) shows the clock signal CLK supplied from the modulation circuit. When reading the PID in the reproducing state, the supply of the CLK is stopped in order to reduce the influence on the adjacent signal line during the reproducing. At this time, the internal PLL circuit 115 continues to oscillate while maintaining the recording frequency. FIG. 3 (v) shows an output signal of the PLL unlock circuit 116, which is also an output of the monitor circuit 117.

The normal output of the PLL unlock detection circuit 116 is “L”, but when an abnormal state of the PLL circuit 115 is detected, the output is set to “H”. This output is received by the arithmetic and control circuit 6, which outputs the WRG for setting the recording state to “H” from the modulation circuit 7 and temporarily outputs the NRZ signal from the modulation circuit 7. Stop and wait for the PLL oscillation state to recover. When the PLL oscillation state is recovered in the data area, the output of the unlock detection signal returns to "L", and recording is started again.

Note that even when the unlock state of the PLL circuit 115 is detected, only the clock CLK from the modulation circuit 7 continues to be sent to stabilize PLL synchronization. This makes it possible to stabilize the PLL oscillation state in a short period of time.
<Second embodiment>
FIG. 4 shows an information recording / reproducing apparatus according to a second embodiment of the present invention. In the present embodiment, as another usage of the laser driver, a case will be considered in which a rewritable optical disk such as CD-R recording or DVD-R recording is used. The CD-R / DVD-R recording medium is an organic dye film, and the recording medium 1 is rotated while being held by a spindle motor 2, and performs recording and reproduction of information similarly to the first embodiment. A semiconductor laser (not shown in the figure) that emits light, an optical system for forming light from the semiconductor laser as a light spot of about 1 micron on a disk surface, and information reflected by the recording medium 1. The recording and reproduction of information on the recording medium 1 are performed by the optical head 3 having the photodetector 16 for performing the reproduction and the light spot control such as the automatic focusing and the track tracking.

ＣＤ Hereinafter, the case of CD-R will be described in detail. Recording operation is important in CD-R recording. The data recorded on the CD-R recording medium is an EFM code (hereinafter, collectively referred to as an NRZ signal) corresponding to the CD format, and is usually used to continuously or one-shot CD-ROM data or CD-Audio data. Is recorded on a designated track on the recording medium 1 by application software in the host 4. In FIG. 4, two lasers are mounted as in FIG. 1, but a laser C9 having a wavelength of 780 nm is used to record CD-related information data.

サ ー ボ It is necessary to detect a servo signal and the like even during continuous recording of CD-R, and it is necessary to sample and hold a DC level corresponding to a reproduction power level among the pulse-modulated reflected light. Conventionally, a delay circuit is provided on a substrate for adjusting the timing of the NRZ modulation signal from the modulation circuit 7 to the reflected light. Since the laser driver 10 according to the present invention obtains the NRZ modulation signal and the clock signal CLK synchronized with the NRZ modulation signal, the laser driver 10 is configured to generate a recording current signal corresponding to the NRZ signal through the delay circuit 114 disposed therein. , This delay circuit 114 is used. The output of the delay circuit 114 is sent from the laser driver 10 as a monitor signal, and the pre-circuit 14 generates a timing signal for sampling / holding the reflected light from the recording medium 1 based on the monitor signal. This eliminates the need to provide a separate delay circuit on the substrate.

説明 This will be described in detail with reference to FIG. FIG. 5 (i) shows an NRZ signal, which is a signal sent from the modulation circuit 7 to the laser driver 10. In the laser driver 10, the recording circuit shown in FIG. A signal is issued. As the delay time ΔT, 8 Tw to 32 Tw can be set. Note that Tw is the period of the recording frequency. When the laser is driven at a high output by the recording pulse signal of FIG. 5 (ii), a reflected light signal as shown in FIG. 5 (iii) is obtained at the photodetector 16 during data recording.

As for the reflected light signal as shown in FIG. 5 (iii), a signal corresponding to the reflectivity of the optical disk is obtained at the start of light pulse irradiation, but after a certain time, recording starts due to a rise in the temperature of the recording film, and the reflected light Decrease. Since this signal component disturbs the servo signal being recorded, the reproduction power level of the reflected light is sampled using the gate signal obtained as one of the monitor signals in FIG. By outputting the gate signal (SH signal) to be held by the pulse section from the pre-circuit 14, the servo signal during recording can be stabilized.

(2) Further, as shown in FIG. 2, the emitted light of the laser C9 is received by the front monitor C32, converted into a voltage by the IV conversion circuit 34, and guided to the power control circuit 15. The output waveform during recording is obtained by placing a front monitor signal in (vi) of FIG. 5 and placing it in the power control circuit 15 by using a gate signal in FIG. 5 (iv) obtained as one of the monitor signals of the laser driver 10. The pulse level and the reproduction level are separately sampled and held, and the respective levels are sent to the arithmetic and control circuit 6. The arithmetic and control circuit 6 captures digital data by the AD converter and sends the result of calculating the target value to the laser driver 10 via the serial interface, thereby updating the Pread value in the case of reproduction power, and updating the Pread value in the case of recording power. By performing feedback control that updates the Pmax value, continuous stabilization of each power can be realized.

FIG. 2 is a configuration diagram of a first embodiment of the present invention. FIG. 3 is a detailed view of the laser driver according to the first embodiment. FIG. 4 is an operation timing chart of the first embodiment. Configuration diagram of a second embodiment of the present invention Operation timing chart of the second embodiment

Explanation of reference numerals

DESCRIPTION OF SYMBOLS 1 ... Recording medium, 2 ... Spindle motor, 3 ... Optical head, 4 ... Host, 5 ... Interface control circuit, 6 ... Operation / control circuit, 7 ... Modulation circuit, 8 ... DVD laser D, 9 ... CD laser C Reference numeral 10 laser driver, 11 reproduction circuit, 12 demodulation circuit, 13 servo control circuit, 14 front circuit, 15 power control circuit, 16 photodetector, 31 front monitor D, 32 front monitor C, 33, 34: IV conversion circuit, 100: Serial interface control unit, 101: Pread register, 102: Read DAC, 103: HFM, 104: Write Strategy control unit, 105: recording current generation unit, 106: Pa Register 107, Pb register, 108 Pc register, 109 Pd register, 110 selector, 111 Write Power DAC, 112 Pmax register, 113 Full Scale DAC, 1 4 ... monitor circuit, 115 ... built-in PLL circuit, 116 ... unlock detection circuit.

Claims (4)

A semiconductor laser, a laser driver for driving the semiconductor laser to emit light, an optical system for focusing light emitted from the semiconductor laser as a spot on an information recording medium, and light for receiving light reflected from the information recording medium An optical head having a detector;
A modulation circuit for modulating information according to a predetermined rule,
A demodulation circuit for returning the reproduced signal to the original information;
An information recording / reproducing device including an arithmetic / control circuit for controlling the modulation circuit and the demodulation circuit,
A binarized signal from the modulating circuit and a clock signal synchronized with the binarized signal are obtained, and a recording frequency is oscillated by a PLL circuit arranged inside, thereby obtaining a recording current signal corresponding to the binarized signal. Providing a laser driver that generates
The laser driver includes an unlock detection circuit that detects an oscillation state of the PLL circuit, sends a detection signal from the unlock detection circuit to the arithmetic and control circuit as a monitor signal, and records the signal based on the monitor signal. An information recording / reproducing device for controlling operation. A semiconductor laser, a laser driver for driving the semiconductor laser to emit light, an optical system for narrowing light emitted from the semiconductor laser as a spot on an information recording medium for optically recording and reproducing information, and An optical head having a photodetector that receives light reflected from the information recording medium,
A modulation circuit for modulating information according to a predetermined rule,
A demodulation circuit for returning the reproduced signal to the original information;
An information recording / reproducing device comprising an arithmetic / control circuit controlling the modulation circuit and the demodulation circuit,
A laser driver for obtaining a binarized signal from the modulation circuit and a clock signal synchronized with the binarized signal, and generating a recording current signal corresponding to the binarized signal through a delay circuit disposed therein;
An information recording / reproducing apparatus, wherein an output of the delay circuit is sent to the arithmetic / control circuit as a monitor signal, and a timing signal for sampling / holding reflected light from a recording medium is generated based on the monitor signal. An optical disc device configured to supply a signal to a laser drive circuit included in an optical pickup via a flexible cable,
A laser circuit configured to generate a second clock signal having a frequency different from the first clock signal based on the first clock signal supplied via the flexible cable; A detection circuit for detecting an abnormality, and generating a laser drive current based on the second clock signal and a binary signal supplied via the flexible cable,
An information recording / reproducing apparatus, wherein when the detection circuit detects an abnormality of the PLL circuit, the supply of the binarized signal to the laser drive circuit is stopped. 4. The information recording / reproducing apparatus according to claim 3, wherein the first clock signal is supplied to the laser drive circuit even when the detection circuit detects an abnormality in the PLL circuit.

Images