JP4178060B2 - Optical disc apparatus and optical disc recording method - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an optical disc apparatus, and more particularly to a configuration in which sample and hold is performed on a signal obtained by converting return light from an optical disc into an electric signal for adjustment of laser light intensity, tracking, and focus during recording.
[0002]
[Prior art]
In general, focusing, tracking servo, and adjustment of laser beam intensity on an optical disc are performed by comparing a signal obtained by converting the return beam of the laser beam into an electrical signal (hereinafter referred to as a “return beam detection signal”) with a target value. Is done.
[0003]
During recording operation, the intensity of the emitted laser light is changed according to the signal sequence to be recorded (repetition of recording of marks and spaces on the disk), so the intensity of the return light corresponds to the intensity of the emitted laser light. The level changes greatly. In order to perform the above-described focus control or the like based on the return light detection signal, the return light detection signal needs to take a constant value for a certain period. Therefore, using the sample hold circuit for the return light detection signal, the sample is performed only when the intensity level is large or small in synchronization with the timing of the intensity change of the laser light, and in other periods, By holding, a substantially constant return light detection signal can be obtained.
[0004]
In addition, since a predetermined period is required until the return light detection signal is stabilized after the laser light intensity level is changed, a predetermined period has elapsed with respect to the timing at which the laser light intensity level has changed, and the return light detection signal is in a stable state. Do the sample.
[0005]
In the conventional sample hold at the time of detecting return light, a recording signal corresponding to the mark and space written on the disk is used to generate and output a pulse at a timing synchronized with this, and this is output as a sample hold timing signal (hereinafter “ It is used as a “sample pulse signal”. As a result, the laser light output level is held during a period in which the amount of light is large, and is sampled in a period in which the amount of light is small (see, for example, Patent Document 1).
[0006]
[Patent Document 1]
Japanese Patent Laid-Open No. 5-120704 (page 2-5, FIG. 1)
[0007]
[Problems to be solved by the invention]
In recent years, this type of recordable optical disk has been demanded to have a larger capacity and higher speed recording, and correspondingly, it is necessary to reduce the pit size on the disk and to increase the recording laser light irradiation speed. .
[0008]
When recording data on the disc, the sampling laser pulse becomes faster as the recording laser beam irradiation speeds up, so the interval at which the intensity level of the return light detection signal changes becomes shorter and the stable period suitable for the sample becomes shorter. Higher accuracy is required for signal generation / output timing.
[0009]
In the optical disk apparatus, when the recording signal is generated and the return light detection signal is sampled and held by another device (specifically, by another LSI), the pattern of the substrate is used in the transmission path between both devices. Due to factors such as resistance, inductance, and stray capacitance, large distortion and delay occur in the transmission signal.
[0010]
Therefore, when a sample pulse signal is generated at the same time in the device that generates the recording signal, distortion and delay occur in the waveform of the sample pulse signal due to transmission to the sample hold device, and the accuracy corresponding to the high-speed recording operation is achieved. There is a problem that it is difficult to obtain.
[0011]
Further, the return light detection signal output from the photodetector also has a problem of waveform deterioration due to distortion and noise and generation of noise to the surroundings in the transmission path up to the input of the sample hold device.
[0012]
Further, the laser light intensity, focus and tracking control system has a problem that the characteristics of each element including the signal source laser change during operation due to factors such as temperature change.
[0013]
A first object of the present invention is to reduce a sample timing error caused by signal degradation in a transmission line between two devices, and to enable a sample operation at a more accurate timing.
[0014]
The second object of the present invention is to sample and hold a more accurate signal by reducing the deterioration of the return light detection signal and the influence of noise on the surroundings.
[0015]
A third object of the present invention is to reduce the influence of changes in characteristics of each element over time in a control system using sampled and held values.
[0016]
[Means for Solving the Problems]
The object of the present invention is achieved, for example, by the invention described in the claims.
[0020]
DETAILED DESCRIPTION OF THE INVENTION
An embodiment of the sample hold device (101) in the present invention will be described with reference to FIG.
[0021]
The sample hold device (101) configured by LSI includes a sample pulse generation means (102) and a sample hold circuit (106) that performs sample hold on the return light detection signal at the timing of the sample pulse signal.
[0022]
The sample pulse generation means (102) includes a clock frequency multiplication means (105) (so-called PLL), an edge detection means (103) for detecting the edge of the recording signal and generating a pulse signal synchronized with the edge, and edge detection A pulse width / delay adjustment means (104) for generating a sample pulse signal by giving an appropriate delay and pulse width to the pulse signal output from the means.
[0023]
Recording signals such as NRZI and NRZ and a synchronous clock synchronized therewith are input from the recording signal generating device (401) shown in FIG. 4 through a transmission path between the devices to the sample and hold device (101).
[0024]
The frequency of the synchronizing clock input to the sample pulse generating means (102) is multiplied by the multiplying means (105) to obtain a multiplied clock that is phase-synchronized with the recording signal. Both the multiplied clock and the recording signal are input to the edge detecting means (103) to generate a pulse signal synchronized with the rising edge or falling edge of the recording signal.
[0025]
As an effect of the sample hold device (101) shown in FIG. 1, in order to generate a sample pulse signal in a device that performs sample hold, compared to generating a sample pulse signal in a recording signal generation device which is a separate device. A sample pulse signal with little distortion and delay can be obtained.
[0026]
Here, the transmission path between devices is a signal line such as a pattern on a substrate or a flexible cable. Compared with transmission in a semiconductor device, signal delay, distortion, and radiation noise due to resistance, inductance, stray capacitance, etc. Greatly affects the transmitted signal. Therefore, it is desirable to transmit a low-frequency signal having high noise resistance on the transmission line.
[0027]
In the present embodiment, the frequency multiplying means (105) in the sample pulse generating means (102) can reduce the frequency of the clock signal passing through the inter-device transmission path, so that generation of radiation noise in the transmission path and It is possible to suppress the influence of waveform distortion and attenuation.
[0028]
A configuration example of the edge detection means (103) is shown in FIG. In addition, a timing chart of signals at each part at this time is shown in FIG. When two D flip-flops that operate in synchronization with the multiplied clock are connected in series and the appropriate logic circuit is passed to the output of each D flip-flop, the multiplied clock is synchronized with the edge of the input signal. A pulse signal having a width equal to the period is obtained. In the example of FIG. 2, a pulse signal (hereinafter referred to as “edge pulse signal”) synchronized with the rising edge of the recording signal is obtained. For the pulse signal generated by the edge detection means (103), the pulse width and delay amount setting means (104) change the pulse width and set the delay amount.
[0029]
The structure of the pulse width / delay amount setting means (104) is shown in FIG. The pulse width / delay amount setting means is a shift register composed of n (n is a natural number) D flip-flops that receive the pulse signal from the edge detection means (103) and the multiplication clock and operate in synchronization with the multiplication clock. Section (301), rising timing selection means (302), falling timing selection means (303), and RS flip-flop.
[0030]
A timing chart at each part is shown in FIG. The pulse signal propagates by delaying the output of each flip-flop of the shift register unit (301) by the period of the multiplied clock. The output of each D flip-flop is input to rising timing selection means (302) and falling timing selection means (303).
[0031]
The rising timing selection means (302) and the falling timing selection means (303) select one of the D flip-flop outputs connected to each other, and input the corresponding pulse signal to the S terminal and R terminal of the RS flip-flop. . Then, the output of the RS flip-flop rises simultaneously with the pulse signal selected by the rise timing selection means, and falls with the rise of the pulse signal selected by the fall timing selection means. Therefore, the pulse signal obtained by the edge detection means (106) is a pulse signal whose width and delay amount are adjusted.
[0032]
Here, the output pulse of the fourth flip-flop of the shift register unit is selected as the pulse rising timing, and the output pulse of the m-th (m ≦ n: m is a natural number) flip-flop is selected as the pulse falling timing. Assume that you have selected. As a result, a pulse signal having a width of m-3 clocks is generated from the RS flip-flop with a delay of 4 clocks with respect to the rising edge pulse signal. The output of the RS flip-flop obtained by the above means becomes a sample pulse signal input to the sample hold circuit. The sample hold circuit (108) performs a sample hold operation at the timing of the sample pulse signal with respect to the return light detection signal from the photodetector.
[0033]
Next, a configuration example of an optical disc apparatus using this sample hold device will be described with reference to FIG.
[0034]
(406) is an optical disk, (407) is an objective lens, (408) is a photodetector for monitoring the laser light intensity, (409) is a photodetector for detecting reflected light from the disk, and (405) is a laser beam. A beam splitter that separates the objective lens direction and the laser beam intensity monitor photodetector (408), (410) is a prism, (411) is a differential amplifier for detecting a focus shift, and (412) is a difference for detecting a tracking shift. It is a dynamic amplifier.
[0035]
The sample and hold device (101) in the apparatus in the figure includes a sample and hold circuit (106) for monitoring the laser light intensity and a sample and hold circuit (106) for detecting reflected light, and each of them is a light for monitoring the laser light intensity. The output signal of the detector (408) and the reflected light detection photodetector (409) is sampled and held. The photodetector (409) for detecting reflected light is divided into four, and there are four sample-hold circuits (106) for monitoring the laser light intensity corresponding to this.
[0036]
The recording signal output from the recording signal generation device (401) is input to the sample hold device (101) together with the synchronous clock, and is input to the laser control means (402), passes through the laser driving means (403), and passes through the laser (404). ) Emits laser light. The emitted laser light is separated by the beam splitter (405), and is incident on the laser light intensity monitor photodetector (408) on the one hand, and reflected by the prism (410) on the other hand and then transmitted through the objective lens (407). The light is reflected from the disk (406) and is incident on the photodetector (409) for reflected light. In the sample and hold device (101), the laser beam is synchronized with the edge of the recording signal by the multiplied pulse obtained by multiplying the synchronous clock and the sample pulse signal generated by the sample pulse generating means (102) from the recording signal. The output signals of the photodetector for intensity monitoring (408) and the photodetector for reflected light (409) are sampled and held. The outputs of the four sample-and-hold circuits (106) for detecting reflected light are respectively input to a focus error detection differential amplifier (411) and a tracking error detection differential amplifier (412) to obtain a focus error signal and a tracking error signal. Generate.
[0037]
The focus error signal and the tracking error signal are input to the focus control means (413) and the tracking control means (415), respectively, and the focus drive means (414) and the tracking drive means ( The control signal is given to 416) to adjust the position of the objective lens (407), thereby adjusting the focus position and tracking position of the laser light on the optical disk.
[0038]
The output signal of the laser light intensity monitoring sample and hold circuit (106) is input to the laser control means (402) and compared with the target value to adjust the irradiation intensity of the laser light.
[0039]
As an effect of the apparatus shown in FIG. 4, since the sample pulse generating means (102) exists in the device that performs the sample and hold, the return light detection signal can be sampled and held at a precise timing and the write operation can be performed at high speed. Laser light intensity, tracking, and focus can be controlled stably.
[0040]
Next, another embodiment of the present invention will be described. FIG. 5 shows a photodetection / sample hold device (501) in which the sample hold device (101) and the photodetector (503) in FIG. 1 are built in the same device. The sample hold unit (502) corresponds to the sample hold device (101) shown in FIG. The photodetector (502) corresponds to the photodetector (408) for monitoring laser light intensity or the photodetector (409) for reflected light in FIG. Description of members having the same function is omitted.
[0041]
In this device, sample pulse generation, return light detection, conversion to an electrical signal, and sample hold are performed by the same device. The light detection-sample hold device (501) is replaced with a light detector (408) for monitoring laser light intensity, a light detector (409) for reflected light, and a sample hold device (101) in the apparatus configuration of FIG. be able to.
[0042]
In addition to being able to generate a sample pulse signal with the same accuracy as the apparatus shown in FIG. 1 by incorporating the photodetector in the same device as the sample hold unit (502) as shown in FIG. 5, the photodetector (503) To the sample-and-hold circuit (108) in the transmission line can be reduced in distortion due to distortion and noise, and the sample value can be obtained with higher accuracy.
[0043]
Next, another embodiment of the present invention will be described. FIG. 6 shows an example in which the sample hold device (101), A / D conversion means (602), and sample hold value monitor means (603) in FIG. 1 are incorporated in the same device (601). The A / D conversion means (602) converts the analog signal sampled by the sample hold circuit (108) into a digital signal. The sample hold value monitor means (603) is, for example, a register connected to a microprocessor bus existing outside the device, and displays the digital signal value generated by the A / D conversion means (602). Description of members having the same function is omitted.
[0044]
In this embodiment, since the microprocessor can refer to the display value of the sample hold value monitoring means (603), if the sample hold value changes on average due to a change in characteristics of each element (for example, a change in laser characteristics due to heat) or the like. Since the microprocessor can adjust the characteristic setting means (register or the like) of each control means according to the sample hold value, stable control can be realized against changes.
[0045]
In the above embodiments, the sample hold devices (101, 501, 601) are described on the premise that they are composed of LSIs. However, the present invention is not limited to this and is contrary to the spirit of the invention. Variations are possible as long as they are not.
[0046]
【The invention's effect】
According to the present invention, the influence of the control signal transmission path can be reduced and the sample hold timing pulse can be generated accurately in the detection of the return light of the laser light irradiation during recording on the optical disk. It is effective for realizing high speed.
[Brief description of the drawings]
FIG. 1 shows an embodiment of a sample and hold device. FIG. 2 shows a structure and timing diagram of an edge detection unit. FIG. 3 shows a structure and timing diagram of a pulse width / delay amount setting unit. Example of configuration of optical disc apparatus used [FIG. 5] Photodetection-sample hold device [FIG. 6] Sample hold device having A / D conversion means and sample hold value monitor means
101: Sample hold device 102: Sample pulse generation means 105: Multiplication means 103: Edge detection means 104: Pulse width / delay amount setting means 106: Sample hold circuit 405: Beam splitter 408: For laser light intensity monitoring Photodetector 409: photodetector for reflected light, 411: differential amplifier circuit for detecting focus deviation 412: differential amplifier circuit for detecting tracking error

Claims (6)

An optical disk device for recording a signal on an optical disk,
A laser for irradiating the optical disk with laser light;
Photodetection means for converting return light from the optical disc into an electrical signal;
A multiplying PLL for generating a reference clock from the input clock signal;
Sample pulse generating means for generating a sample pulse signal based on the reference clock;
Sample hold means for holding an electrical signal obtained by the reflected light detection means based on the sample pulse signal;
It has
The sample pulse generation means and the sample hold means are provided in the same LSI ,
The sample pulse generating means includes
Edge detection means for generating a pulse signal by detecting an edge of a recording signal using the reference clock;
Pulse width / delay amount setting means for performing at least one of delay and pulse width adjustment based on the timing of the pulse signal;
An optical disc apparatus comprising: The optical disc apparatus according to claim 1,
A / D conversion means for converting the sampled and held analog value into a digital value;
Sample hold value monitoring means for holding the digital value converted by the A / D conversion means;
A microprocessor;
Laser control means for controlling the output or emission timing of the laser;
Laser control characteristic setting means for setting control parameters of the laser control means;
Focus control means for controlling the focal position of the emitted light of the laser;
Focus control characteristic setting means for setting control parameters of the focus control means;
Tracking control means for controlling the laser to irradiate a track on the optical disc;
Tracking control characteristic setting means for setting a control parameter of the tracking control means;
Have
The microprocessor is capable of acquiring a sample hold value using the sample hold value monitoring means, and at least one of the laser control characteristic setting means, the focus control characteristic setting means, and the tracking control characteristic setting means. An optical disc apparatus capable of setting one control parameter .   The optical disc apparatus according to claim 1 or 2,
  An optical disc apparatus characterized in that the light detection means is included in the LSI.   An optical disc recording method for recording a signal on an optical disc,
  When performing the sample hold by converting the return light of the laser light into an electrical signal,
  A reference clock generation process for generating a reference clock by inputting the input clock to the multiplication PLL;
  A pulse signal generation process for generating a pulse signal synchronized with an edge of a recording signal to be recorded on the optical disc based on the reference clock;
  A sampler that generates a sample pulse signal that determines the timing of sample and hold by adjusting the pulse width and timing with reference to the timing of the pulse signal. Pulse signal generation processing,
  Sample and hold processing for performing sample and hold using the sample pulse signal;
  Is executed in the same LSI.   An optical disk recording method according to claim 4, wherein
  Furthermore, the sample hold signal obtained by the sample hold process is A / D converted and displayed in a register in the same LSI,
  Read the register value by the microprocessor,
  The microprocessor controls, according to the register value, control parameters of laser control means for controlling the output or emission timing of a laser provided in the optical disc apparatus, and control of focus control means for controlling the focal position of the emitted light of the laser. An optical disc recording method comprising setting at least one of a parameter and a control parameter of a tracking control means for controlling the laser to irradiate a track on the optical disc. The optical disc recording method according to claim 4 or 5,
It further has a light detection means inside the LSI,
An optical disc recording method, wherein return light is converted into an electric signal by the light detection means .

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