JP2008091028A - Information recording/reproducing device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an information recording/reproducing device capable of recording/reproducing information data stably to various recording media by using a laser driver capable of performing recording strategy control to various recording media. <P>SOLUTION: The laser driver capable of generating a write current signal corresponding to an NRZ signal by obtaining the NRZ signal from a modulation circuit and a clock signal chCLK synchronized with it and oscillating a recording frequency by the PLL circuit 115 placed in the laser driver 10, is provided with an unlock detection circuit 116 for sensing an oscillation state of the PLL circuit, and recording/reproducing operation is controlled according to a detection signal from the unlock circuit 116. <P>COPYRIGHT: (C)2008,JPO&INPIT

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 therewith to deal with the binarized signal. The present invention relates to an information recording / reproducing apparatus having a laser driver capable of generating a recorded current signal.

A recording film of an information recording medium is irradiated with a light beam, and recording marks such as drilling pits, phase change pits, dye pits or magnetized domains are formed on the recording film to record information, and reflected light from the recording medium is used. In an optical information recording / reproducing apparatus for reproducing information, a plurality of information recording media (referred to as optical discs) can be used interchangeably, so that the information can be recorded / reproduced in large quantities. It is used as a mass storage device for computers.

In recent years, with high density recording, marks (or pits) recorded on the surface of information recording media are required to be formed with a length of 0.5 μm or less, for example, and recording power is pulsed to realize this mark formation. There is a need for power control in which division (multipulse) is performed and the level is changed to multiple values (for example, ternary or quaternary). Also, to optimize the time interval between the recording mark group and the space group between them, the time position and pulse width of the recording pulse divided according to the adjacent space length and mark length are adaptively variably controlled during mark recording. Therefore, adaptive control of recording pulses to be performed (hereinafter, this control is referred to as recording strategy control) has become necessary.

In order to perform such a recording strategy control, it is necessary to consider the rising characteristics (Tr) / falling characteristics (Tf) of each pulse of the multi-pulse. In this case, the Tr and Tf characteristics require about several ns. However, in order to increase the Tr and Tf characteristics at a higher speed in response to an increase in the disk rotation speed due to a request for high-speed transfer recording, an optical head is used. It is very difficult to transmit to the laser without deterioration of 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 the transmission distance of the recording pulse waveform from the substrate to the laser of the optical head must be long due to the configuration. It was because there was not.

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

Another object of the present invention is to provide a laser driver provided with a circuit for executing recording strategy control that enables recording strategy control for various recording media, and to use this laser driver to provide 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.

  The gist of the present invention for realizing the above problems is as follows.

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 modulation signal from a modulation circuit and a clock signal synchronized therewith, and oscillates a recording frequency by a PLL circuit disposed therein, thereby recording corresponding to the binarized signal. A current signal can be generated. However, if 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 the detection signal from the unlock circuit is sent as a monitor signal to the calculation / control circuit that controls the recording / reproducing operation to control the recording operation. To do.

Here, consider the case of recording information data 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 the DC level corresponding to the reproduction power level in the pulse-modulated reflected light. In this case, a delay circuit is provided to match the timing of the reflected light with respect to the NRZ modulation signal from the modulation circuit. In this case, a problem such as cost occurs due to the addition of the delay circuit.

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

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

Further, the reliability of recording or reproducing information data with respect to 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 / reproduced is held by a spindle motor 2 and rotates. 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 (not shown in the figure) for emitting laser light for recording and reproducing information, and an optical system for forming light from the semiconductor laser as a light spot of about 1 micron on the disk surface; Information is recorded on the information recording medium 1 by an optical head 3 having a light detector 16 for performing light spot control such as information reproduction, autofocus, track tracking, etc. using reflected light from the information recording medium 1, Perform playback. The optical head 3 constitutes a linear motor (not shown) for driving and positioning the optical head 3 at high speed in the disk radial direction. In this embodiment, the optical head 3 and the arithmetic / control circuit 6, the modulation circuit 7, the reproduction circuit 11, and the servo control circuit 13 are connected by a signal line such as a flexible cable. In addition, the interface control circuit 5, the arithmetic / 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.

In general, an optical disk apparatus as an information recording / reproducing apparatus includes a host computer 4 (hereinafter abbreviated as a host) such as a personal computer or a workstation, and a SCSI (Small), for example.
Computer system interface (ATAPI) and AT API (AT Attached Packet Interface) are connected with an interface cable. The command including the command and information data from the host 4 is decoded by the interface control circuit 5 in the optical disk device, and the microcomputer Information recording, reproduction, and seek operations are executed through an arithmetic / control circuit 6 composed of, and the like.

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

In FIG. 1, two lasers are mounted. Laser D8 is DVD related information data (DVD-RA
M / −R / −RW + RW), which is a laser having a wavelength of 650 nm band and used for recording at 30 m
Has an output greater than W. The laser C9 is a laser having a wavelength of 780 nm band used when 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, the reproducing operation in this optical disc apparatus will be described. During 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) designated 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, and the photodetector 16 in the optical head 3 is obtained. The light is received and photoelectrically converted, and is converted into an electric signal and input to the reproducing circuit 11, and then the data is reproduced. Usually, the reproduction circuit 11 has an automatic gain control circuit (AGC) for keeping the signal amplitude constant, a waveform equalization circuit (EQ) for correcting optical spatial frequency degradation, a low-frequency limiting filter (LPF), a binary value. It comprises a digitizing circuit, a PLL (Phase Locked Loop) circuit, and a discriminating circuit. After binarizing the reproduction signal, it is converted into discriminated data. The binarized data thus discriminated is input to the demodulation circuit 12, and (1,7) RLL code, (2,7) RLL code, (2,10) RLL code or EFM code is demodulated to obtain the original data. Demodulate. The demodulated data is guided to the arithmetic 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.

In addition to the data reproduction signal, the photodetector 16 in the optical head 3 can detect an automatic focus signal for performing focus control on the recording film and a track tracking signal for performing track tracking control for positioning an arbitrary track on the recording film. The auto focus signal and the track tracking signal for performing the light spot control 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 records and reproduces information by positioning the optical head 3 on an arbitrary track.

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 supplied by serial transfer from the arithmetic / control circuit 6, converts them into parallel, and writes the set values in the corresponding registers. Note that SEN is a signal for setting the serial interface control unit 100 in an operating state, SCLK is a clock signal for the serial interface control unit 100, and SDIO is Seri.
This is a data signal of the al interface control unit 100.

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

The recording current generator 105 includes a Pa register 106 that stores the recording power Pa, a Pb register 107 that stores the recording power Pb, a Pc register 108 that stores the recording power Pc, and Pd registers 109 and 106 to 109 that store the recording power Pd. The write power DAC 111 includes a selector 110 that selects any one of the outputs of the register and a digital-analog conversion circuit that outputs a recording drive current Iwrite corresponding to the recording power value of the selected register.

Further, the current corresponding to the Pmax value stored in the Pmax register 112 is set to Write Power DA.
Full-comprising digital-to-analog converter circuit that outputs as C111 reference current Iref
Scale DAC 113 is provided. The Write Strategy control unit 104 determines the recording power waveform timing (Pa to Pd registers based on the NRZ signal (binarized signal), the clock signal chCLK, and the control signal WRG for setting the recording / reproducing state supplied from the modulation circuit 7. Control signal Px-s to select
elect) can be generated.

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

The PLL circuit is installed inside the laser driver 10 instead of the substrate, and the clock signal chCL
Transmission is performed with the K frequency lowered, and the PLL circuit 115 in the laser driver 10 oscillates in synchronization with the normal recording frequency, so that the arithmetic / control circuit 6 and the modulation circuit 7 which are normally arranged on the substrate are transferred onto the substrate. When a high-frequency signal is transmitted to the optical head 3 that cannot be arranged, it is possible to reduce the influence of an adjacent signal line (for example, a flexible cable) or unnecessary radiation generated when a high-frequency signal is generated.

However, the arithmetic / control circuit 6 that controls the entire optical disk apparatus controls the modulation circuit 7 to
Although the abnormality of the clock signal chCLK supplied to the LL circuit 115 can be determined, the abnormality of the oscillation state of the PLL circuit 115 in the laser driver cannot be determined. Therefore, although the clock signal chCLK is normally supplied to the PLL circuit 115, the PLL circuit 11
When the oscillation state 5 becomes abnormal, there is a problem that even if it is determined that the optical disk apparatus itself is normally recorded, the information recording medium 1 is not normally recorded normally. .

Therefore, an unlock detection circuit 116 that detects the oscillation state of the PLL circuit 115 is installed in the laser driver 10, and the calculation / control that controls the recording / reproducing operation from the monitor circuit 117 using the detection signal from the unlock detection circuit 116 as a monitor signal. This can be realized by sending to the circuit 6 and controlling the recording operation.

In FIG. 3, the above optical disk apparatus is a DVD-RAM drive, and the information recording medium 1 is a DVD-RAM.
A recording operation in the case of recording as a RAM disk will be described in detail. FIG. 3 (i) is a reproduction signal in a reproduction circuit at the time of recording, PID (Physical Identification Data) is an address addressed in sector units, DATA1 is recorded data, DATA2 is a signal by reflected light at the time of recording, Data recording is performed only in the data area of the designated sector number from the upper level. FIG. 3 (ii) shows an NRZ signal supplied from the modulation circuit 7, which is supplied only to the data area. FIG. 3 (iii) is a control signal WRG for setting a recordable state. “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 which is in the reproduction state, the C signal is used to reduce the influence on the adjacent signal line during reproduction.
Stop LK supply. At this time, the internal PLL circuit 115 continues to oscillate while maintaining the recording frequency. FIG. 3 (v) is an output signal of the PLL unlock circuit 116 and also an output of the monitor circuit 117.

The PLL unlock detection circuit 116 normally outputs “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 / control circuit 6, and the arithmetic / control circuit 6 sets WRG for setting the recording state to “H” and outputs it from the modulation circuit 7, and temporarily sends out the NRZ signal from the modulation circuit 7. Stop and wait for recovery of PLL oscillation state. 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.

Even when the unlocked state of the PLL circuit 115 is detected, only the clock CLK from the modulation circuit 7 is continuously sent to stabilize the PLL synchronization. As a result, the PLL oscillation state can be stabilized in a short period.
<Second embodiment>
An information recording / reproducing apparatus according to the second embodiment of the present invention will be described with reference to FIG. In the present embodiment, as another method of using the laser driver, consider a case where it corresponds to a write-once type optical disc that cannot be rewritten like CD-R recording or DVD-R recording. The CD-R / DVD-R recording medium is an organic dye film, and this recording medium 1 is held and rotated by a spindle motor 2 and laser light for recording and reproducing information as in the first embodiment. Semiconductor laser (
(Not shown in the figure), an optical system for forming light from the semiconductor laser as a light spot of about 1 micron on the disk surface, information reproduction and autofocus using the reflected light from the recording medium 1, Information is recorded on and reproduced from the recording medium 1 by an optical head 3 having a photodetector 16 for performing light spot control such as track tracking.

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

It is necessary to detect a servo signal or the like even during continuous recording of CD-R, and it is necessary to sample and hold the DC level corresponding to the reproduction power level of the pulse-modulated reflected light. Conventionally, a delay circuit has been installed on the substrate in order to synchronize the reflected light with the NRZ modulation signal from the modulation circuit 7. The laser driver 10 according to the present invention has a configuration in which an NRZ modulation signal and a clock signal CLK synchronized therewith can be obtained and a recording current signal corresponding to the NRZ signal can be generated through a delay circuit 114 disposed therein. ,
This delay circuit 114 is used. The output of the delay circuit 114 is sent out from the laser driver 10 as a monitor signal, and a timing signal for sampling / holding the reflected light from the recording medium 1 is generated by the pre-circuit 14 based on the monitor signal. This eliminates the need for a separate delay circuit on the substrate.

This will be described in detail with reference to FIG. FIG. 5 (i) is an NRZ signal, which is a signal sent from the modulation circuit 7 to the laser driver 10. The delay pulse 114 in the laser driver 10 causes the recording pulse of FIG. 5 (ii) after a predetermined delay time ΔT. A signal is issued. As this delay time ΔT, 8Tw to 32Tw can be set. 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), the photodetector 1 during data recording
In FIG. 6, a reflected light signal as shown in FIG.

As for the reflected light signal as shown in FIG. 5 (iii), a signal corresponding to the reflectance of the optical disk is obtained at the start of light pulse irradiation, but after a certain time, recording starts due to the temperature rise of the recording film. Decrease. Since this signal component becomes a disturbance to the servo signal during recording, the reproduction power level of the reflected light is sampled by using a gate signal obtained as one of the monitor signals of FIG. 5 (iv) of the laser driver 10. The pulse portion can stabilize the servo signal during recording by outputting a gate signal (SH signal) to be held from the pre-circuit 14.

Further, as shown in FIG. 2, the light emitted from the laser C9 is received by the front monitor C32, and IV
The voltage is converted into a voltage by the conversion circuit 34 and led to the power control circuit 15. The output waveform during recording is shown in (v
i) A front monitor signal is obtained, and the recording pulse level and reproduction level are separately sampled in the power control circuit 15 using the gate signal shown in FIG. 5 (iv) obtained as one of the monitor signals of the laser driver 10. Each level is held and sent to the arithmetic / control circuit 6. The calculation / control circuit 6 takes in the 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 in the case of recording power. By performing feedback control that updates the Pmax value, continuous stabilization of each power can be realized.

It is a block diagram of the 1st Example of this invention. It is a detailed view of the laser driver of the first embodiment. It is an operation | movement timing diagram of a 1st Example. Configuration diagram of the second embodiment of the present invention Operation timing chart of the second embodiment

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Recording medium, 2 ... Spindle motor, 3 ... Optical head, 4 ... Host, 5 ... Interface control circuit, 6 ... Calculation / control circuit, 7 ... Modulation circuit, 8 ... Laser D for DVD, 9 ... Laser C for CD DESCRIPTION OF SYMBOLS 10 ... Laser driver, 11 ... Reproduction circuit, 12 ... Demodulation circuit, 13 ... Servo control circuit, 14 ... Pre-circuit, 15 ... Power control circuit, 16 ... Photo detector, 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 S
trategy control unit, 105 ... recording current generation unit, 106 ... Pa register, 107 ... Pb register,
108 ... Pc register, 109 ... Pd register, 110 ... selector, 111 ... Write Power DA
C, 112 ... Pmax register, 113 ... Full Scale DAC, 114 ... Monitor circuit, 115
... built-in PLL circuit, 116 ... unlock detection circuit.

Claims (4)

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

Images