JPH09147364A - Device for evaluating function of cd-r recording/ reproducing device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To determined the quality of a product by evaluating a function for accurately reading a group signal from an optical disk in which a group is formed and the function of a photodetecting element for reading the group signal. SOLUTION: Signals A, B, C and D detected by a detecting element are collected into (A+D) and (B+C) and by obtaining a difference between these signals, RF signals as common-mode components (by information signals indicated by pits) are offset and a group signal (wobbling signal for tracking) composed of reverse phase components are take out. In order to measure the characteristics of all the signals including this group signal, drawer taps TP-1 to TP-9 are provided in the main points of the circuit. Jitters are counted by a jitter counter and thereby the quality of a product is detected by the photodetecting element.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a CD-R (writable compact disc) player, ATI
P (Abusolute Time In Pregroove) / CLV (constant linear velocity) servo control.

[0002]

2. Description of the Related Art In a magneto-optical disk conventionally known as an MD (mini disk), meandering grooves are provided over the entire surface of the disk from the manufacturing stage, and an address is recorded every 13.3 ms. The meandering groove is a tracking groove, and the meandering frequency of the groove is used as a standard for always stabilizing the rotation speed of the disk. In addition, this meander is PM (Phase Modalatiton) modulated,
The modulation contains absolute position information indicating where the recorded signal is from the start of recording on the disc.

The meandering groove is called a pre-groove. Since this groove is provided, the CLV servo can be applied even when newly recording on a disc on which nothing is recorded. Also in the CD-R player according to the present invention,
ATIP / CLV servo control is used as in the case of the MD player.

In general, a disk has a track length longer on the outer circumference than on the inner circumference. Therefore, when the number of revolutions of the disk is constant, the traveling speed of the head (pickup) increases on the outer periphery and the head travels on the inner periphery. There is an inconvenience that the speed becomes slow. As one of the ways to overcome this inconvenience,
There is a method of making the rotational speed of the disk slower on the outer circumference of the disk and faster on the inner circumference so that the traveling speed of the head on the track is always constant.

This method is known as CLV (constant linear velocity). In order to perform CLV servo control, it is necessary to control the disk rotation motor so as to change the disk rotation speed according to the position of the head on the disk. The disc used in the present invention has a concentric or spiral track groove formed in advance on the disc,
This track groove is a meandering groove for tracking servo that is meandered by being modulated by a wobbling signal of 22.05 KHz.

In controlling the disc rotation motor, the wobbling signal is decoded and detected by a dedicated decoder so that the demodulated wobbling signal becomes 22.05 KHz regardless of the position of the head on the disc. By controlling the rotational speed of the rotary spindle, the spindle rotational speed can be controlled so that the head traveling speed becomes constant.

[0007]

[Problems to be Solved by the Invention] This CLV (Constant
Line Velocity (constant linear velocity) control method is CAV (Co
nstant Angular Velocity (constant angular velocity) control method can increase the amount of information that can be recorded on one disc compared to the control method, so it is advantageous in information recording but difficult to control the rotation of the disc. is there.

Therefore, one object of the present invention is to provide an apparatus for effectively detecting the groove signal. Another object of the present invention is to provide an apparatus for evaluating a general signal level of an optical pickup (photodetector).

[0009]

According to the present invention, in order to solve the above-mentioned problems, according to the present invention, a state of a groove is formed from an optical disc provided with a meandering groove (groove) modulated in advance by a wobbling signal for tracking servo. Is a device for evaluating the function of a CD-R recording / reproducing device, in which only a groove signal indicating the above is taken out, and constant linear velocity servo control for controlling the number of revolutions of the optical disk is performed based on the groove signal. Means for dividing the plurality of signals including the RF signal and the groove signal detected by the plurality of detection plates into two signals in which the groove signals have mutually opposite phases, and the signal levels of the two signals are substantially the same. And the automatic gain control circuit means for adjusting so that the same level is obtained by taking the difference between the two signals. CD-R recording / reproducing, characterized in that a means for canceling out an RF signal component composed of a component and taking out only a groove signal is provided, and a tap terminal for measurement is provided at a main part of the input and output of each means. An apparatus for evaluating the function of the apparatus is provided. Further, using the above-mentioned function evaluation device, the above-mentioned photodetection element is the object to be evaluated, and the pulse jitter during one period of a pulse train consisting of a bit clock signal generated based on the above-mentioned groove signal in the above-mentioned function evaluation device is measured. As a result, it can be used as a pickup evaluation machine in a pickup production line for evaluating the quality of a photodetector. Further, using the above-mentioned device for functional evaluation, subjecting the above-mentioned photodetecting element to evaluation, subjecting the above-mentioned groove signal to FM demodulation, and viewing the ATIP eye pattern using a measuring instrument such as an oscilloscope for the waveform passed through a low-pass filter. Enables to judge whether the ATIP / CLV servo function is good or bad.

[0010]

BEST MODE FOR CARRYING OUT THE INVENTION First, a method of detecting a wobbling signal from a disk for applying an ATIP CLV servo will be described.

As shown in FIG. 5, the disk 501 is formed on the spindle 5 by means such as a turntable (not shown).
Mounted so as to be coupled with 02, the spindle 502 is coupled to the motor 503 and is rotated thereby. This motor is connected to the rotation control circuit 504 and is controlled in rotation speed as described later.

Tracks are formed on the disk, and information is written in the tracks in the form of pit strings. This is shown in FIG. The information on the track is read by the pickup 505 in FIG. This reading is performed by projecting a laser beam on the surface of the disk and receiving reflected light from the laser beam.

The position of the laser beam on the disk is as shown in FIG. It is important to note here that the CD pickup uses three beams on one track for tracking control.
In the -R pickup, the tracking main beam is applied to the tracks on both sides with respect to the central main beam for reading information.

According to this method, even if the tracking beam moves to the left or right for tracking, the information reading beam is not affected by it, so that the track can be traced properly.

The tracking beam is received by the light-receiving element composed of four light-receiving plates in the pickup 505, and an electric signal whose amplitude changes according to the deviation of the beam from the track is obtained. Are supplied to the signal processing circuit 506. The pickup 505 is moved by the motor control circuit 508 in the radial direction of the disc to access a plurality of tracks.
The position can be adjusted so that the beam is accurately moved and the beam is accurately placed on the track by the track shift signal given from the signal processing circuit to the pickup control circuit 507.

The above is a general description of a known CD reproducing apparatus, and the description is given here for the sake of facilitating the understanding of the present invention. However, since it is not directly related to the gist of the present invention, no further explanation is given. Description will be omitted, and an example of the CLV servo control function evaluation device of the present invention will be described next.

As shown in FIG. 1, in this evaluation device, the information signal and the tracking signal detected by the pickup 101 and converted into an electric signal are amplified by RF-AMP (radio frequency amplifier), and then the CLV control signal is obtained. The evaluation data is obtained by measuring the signal waveform of the tap that is supplied to the detection circuit 103 and is extracted from each part of the detection circuit 103.

The output from the CLV control signal detection circuit 103 is supplied to the CLV servo circuit 104, and the output of this CLV servo circuit is supplied to the spindle motor driver 105 to control the rotation of the disk by a known method. .

In this disk rotation motor control, the wobbling signal used as a control reference is mixed in the white noise signal (RF signal), so that the RF signal must be removed successfully in order to extract only the wobbling signal. .

Here, the noise signal is an in-phase signal,
The wobbling signal is composed of two signals (A +
By recognizing that it is composed of D) and (B + C), by passing these signals through a differential amplifier, the noise signal composed of the in-phase component is canceled and removed, but the wobbling signal is added and output. To do so.

This state is shown in FIG. In FIG. 1, the light receiving element 201 composed of the light detection plates A, B, C and D is
Corresponding to the pickup 101 of. Also, RF-AMP
202 corresponds to the RF-AMP 102 in FIG. 1. The detection output from the detection plate A and the detection output from the detection plate B are added by the operational amplifier A1 and the signal (A + D) is output to the output end T5. The output from the detection plate B and the output from the detection plate C are added by the operational amplifier A2, and a signal (B + C) is output to the output end T6.
Is output.

FIG. 3 shows the CLV control signal detection circuit 10 of FIG.
3 in detail, terminals (A + D), (B +) are respectively connected to terminals T5, T6 from the output terminal of RF-AMP in FIG.
C) is supplied and the auto gain control IC (IC
-1). Also, these signals are taps TP
-1, TP-2 can be taken out.

Auto gain control IC (IC-
One output (A + D) from 1) is inverted in the operational amplifier A3 and the other output (B + C) from (IC-1).
Together with one input of the operational amplifier A4, and the difference signal {(A + D)-(B +
C)} is output. This output signal can be taken out from the tap TP-5 and measured.

The output of the operational amplifier A4 is the operational amplifier A
After passing through a filter circuit composed of 5, A6 and CR (capacitance / resistance), it is supplied to an integrated circuit (IC-2) having a demodulation function. The input of (IC-2) can be taken out from the tap TP-6 and measured. Also, the same (IC-2)
The output of can be taken out from the taps TP-7 to TP-9 and measured.

The output of (IC-2) is supplied from the terminal T7 to the ATIP / CLV servo circuit of FIG. The ATIP CLV servo circuit 401 and the spindle motor driver 402 shown in FIG. 4 are the CLV servo circuit 1 shown in FIG.
04 and the spindle motor driver 105.

In the device for functional evaluation according to the present embodiment, in order to cancel the noise component mixed in the servo system, the signal levels of the two signals (A + D) and (B + C) may be almost the same. is important. However, in an actual device, the levels of these signals are not necessarily almost the same.

The cause of the difference in the levels of these two signals can be attributed to the detection element. That is,
When manufacturing the light beam detection element, the photodiode A,
The detection signal levels from (A + D) and (B + C) change depending on the arrangement situation of how B, C, and D are arranged.

When a level difference occurs between the two signals (A + D) and (B + C), the RF signal components cannot be canceled out after the signals pass through the differential amplifier, and only the groove signal is extracted. Will be difficult. Therefore, in this state, ATIP
CLV servo is less likely to be applied.

To prevent this, the four detection plates (four photodiodes) A, B, and
Even if the positions of C and D are slightly deviated, the detection outputs (A + D) and (B + C) from them must always be at a constant level. Therefore, in the present embodiment,
As shown in FIG. 3, the automatic gain control IC (IC
-1), the signal (A + D) supplied to the terminal T5
And the level of the signal (B + C) supplied to the terminal T6 is adjusted to be substantially equal. The circuit condition of this auto gain control IC is that the input signal level is 50 m.
If V ~ 100 mVpp, both outputs are always 0.
It is selected to be about 5Vpp.

The system configuration of the device for evaluating the function of the CD-R recording / reproducing device of the present invention has been described above. Next, the function evaluation of the ATIP / CLV servo control circuit using this device for evaluating the function will be described. For this evaluation, a disk containing a signal for evaluating the signal level called white noise is used, but since the disk of this kind that has been used conventionally does not have grooves, the ATIP
The function of CLV servo cannot be checked.

Therefore, in the present invention, a special glass disk in which the tracks of the pit train forming the white noise signal are undulated at a frequency of 22.05 KHz is formed, and this glass disk is used to evaluate a normal level signal. Added support for ATIP / CLV servo function evaluation.

First, the groove signal (22.05 KHz)
In the apparatus according to the present embodiment, as shown in FIG. 1, a device for taking out the pit information signal on the disc is taken out from the photodiode plate (A, B, C, D, etc.) on the device. In RF-AMP, (A + D) signal and (B + C) signal are created in advance. These signals are composed of a pit information signal having an in-phase component and a groove signal having an anti-phase component.

The above two signals produced in the RF-AMP are supplied to the auto gain control IC (IC-1) in the ATIP / CLV unit shown in FIG. It is one of the outputs of this auto gain control IC (A
After the + D) signal is inverted in the operational amplifier A3, two signals,-(A + D) and (B, are generated in the operational amplifier A4.
+ C) is added to the output of the operational amplifier A4, the RF signal (pit signal representing the information signal) having the same phase almost disappears, and only the groove signals having the opposite phases are taken out.

As described above, according to the evaluation apparatus of this embodiment, the position of the photodetection plate (the plate with the photodiodes A, B, C, D) of the photodetection element 201 (see FIG. 2) is changed. Even if it is slightly deviated, the level difference of the detection signal due to this is detected by the automatic gain control IC (IC-1).
(See FIG. 3) so that the groove signals are adjusted to be substantially the same so that only the groove signal can be accurately extracted without being affected by the position adjustment of the photodetector plate (PD).

The input signal of this automatic gain control IC can be taken out from the extraction taps PT-1 and PT-2 and measured. The output signal of this auto gain control IC is also drawn out and taps PT-3, PT-4
It is possible to take out and measure from. For the sake of explanation, if the signal appearing at TP-1 is compared with the signal appearing at TP-2 and there is a level difference of, for example, about 21 mV, the auto gain measured from taps PT-3 and PT-4 is measured. The level difference between the two signals at the output of the control IC is, for example, about 8 mV, and the effect of auto gain can be seen.

The output of the adding operational amplifier is tapped (T
The waveform can be observed by taking out from P-5). Furthermore, the signal after passing through the filter circuit composed of operational amplifiers A5 and A6 can be taken out from the tap (TP-6) and observed. The signals observed at these points are groove signals used for servo control, and it can be seen from the signal waveforms that the RF signal components have almost disappeared.

The reason why the groove signals in the signals (A + D) and (B + C) have opposite phases will be described below. However, the disc used is a CD-R with a pit train carrying information signals.
Same frequency as the swell of the upper groove (22.05KH
The wobbled signal component (groove signal) of the above frequency (22.05 KHz) is used because the pit train having a high frequency cannot be followed when the tracking servo is performed. Only have to think.

Referring again to FIG. 2, the four photodetector plates A are
~ D are divided such that A and D are one set and B and C are another set. Then, the detection plate (A +
It is detected by these two sets of detection plates that the laser beam spot to be detected fluctuates left and right (up and down in FIG. 2) with the line formed at the boundary between D) and the detection plate (B + C) as the center line.

The frequency of this beam deflection is the frequency of the wobbling signal, which is 22.05 KHz, and when the beam is deflected to the (A + D) side, the amount of light detected on the (A + D) side increases and (B + C) ) Side reduces the amount of light detected. When the beam is deflected to the (B + C) side, the amount of light detected on the (B + C) side increases, and (A +
The amount of light detected on the D) side decreases.

The amount of light detected by the detection plate (A + D) is inversely proportional to the amount of light detected by the detection plate (B + C). Therefore, considering the wobbling signal as a sine wave, the detection plate (A + D) The detected signal is the detection plate (B +
It has an opposite phase to the signal detected in C).

As described above, since the signal (A + D) detected by the detection plate (A + D) and the signal (B + C) detected by the detection plate (B + C) have opposite phases, one of these signals is used. After phase inversion, the output of the operational amplifier A4, which is the sum of the two, is a sine wave.

The noise contained in the sine wave, that is, the high frequency signal component representing the information signal can be observed by extracting the output of the operational amplifier A4 from the extraction tap TP-5. Moreover, the signal after passing this signal through the filter can be taken out from the tap TP-6 and observed.
The effect of the filter can be evaluated by comparing the signal from TP-5 with the signal from TP-6.

The groove signal extracted by the above method is an IC having an ATIP modulator function (IC-
2) is used to obtain the ATIP bit clock signal. This signal is waveform-shaped by the Schmitt trigger IC (IC-3), taken out from the tap TP-8, and the jitter for one period of the signal pulse train is measured. By using this pulse jitter value, it is possible to quantitatively evaluate the reading quality of the groove signal, which varies depending on the component accuracy and the assembly adjustment accuracy of the photodetector.

Next, the ATIP.C according to the present embodiment described above.
A method for evaluating the function of the manufactured photodetector using the LV function evaluation apparatus will be described. This evaluation is based on "ATI
This is a method in which an evaluation item called "P jitter" is provided and evaluation is performed using this. As described above, a groove (groove) modulated in advance by the wobbling signal is engraved on the disc, and the groove is detected by the newly manufactured light beam detecting element, and the groove signal is reproduced by the above method. .

The ATIP eye pattern can be confirmed by FM demodulating this groove signal, passing it through a low-pass filter, and viewing the output waveform with an oscilloscope. Since this ATIP eye pattern affects the pulse jitter value, the quality of the photodetection element can be determined only by looking at the ATIP eye pattern.

The input to the oscilloscope is taken from taps TP-7 and TP-9 of the circuit of FIG. Tap TP-7 is oscilloscope CH-1 (channel 1)
Is used as an input for forming an ATIP eye pattern, and tap TP-9 is connected to CH-2 of the oscilloscope for triggering. The output waveforms of taps TP-7 and TP-9 form an eye pattern.

The signal waveform-shaped by the Schmitt trigger IC (IC-3) is taken out from the tap TP-8 and supplied to the pulse jitter counter. This pulse jitter counter is TR-5835 (Advantest)
Can be used. The setting conditions for measuring pulse jitter with this measuring device are as follows. Measurement content: Period measurement (PERIOD) Calculation content: Standard deviation (σ) Number of measurements: 5000 (times) Polarity: (+)

As described above, regarding groove detection for CLV servo control, whether or not the photodetecting element can be correctly detected in terms of optical performance is evaluated by evaluating the item called ATIP jitter, thereby making a comprehensive evaluation of the optical section. You can

[Brief description of the drawings]

FIG. 1 is a system configuration diagram of an example of an evaluation device for CLV servo control according to the present invention.

FIG. 2 is a circuit diagram showing an example of a photodetector and an RF amplifier.

FIG. 3 is a circuit diagram showing an example of a groove signal extraction circuit.

FIG. 4 is a circuit diagram of an ATIP CLV servo circuit and a spindle motor driver.

FIG. 5 is a block diagram for each circuit function of the optical disk reproducing device.

FIG. 6 is an explanatory diagram showing tracks on a disc and a light beam.

[Explanation of symbols]

 101 Optical Pickup 102 RF Amplifier 103 CLV Servo Control Signal Detection Circuit 104 CLV Servo Circuit 105 Spindle Motor Driver

Claims (3)

[Claims] 1. A constant line for extracting only a groove signal meandering at a constant frequency from an optical disk having a groove provided in advance for tracking servo, and controlling the number of revolutions of the optical disk based on the groove signal. A device for evaluating the function of a CD-R recording / reproducing device for performing speed servo control, wherein a plurality of signals including an RF signal and a groove signal detected by a plurality of detection plates of a photodetector are used as the groove signal. Means for dividing the two signals into mutually opposite phases, an auto-gain control circuit means for adjusting the signal levels of the two signals to be substantially the same, and two signals having the same levels. Means for canceling out the RF signal component composed of the in-phase component to obtain only the groove signal by taking the difference between Function evaluation apparatus of the CD-R recording and reproducing apparatus characterized by the major portion of the force and outputs provided a tap terminal for measurement. 2. The function evaluation device according to claim 1, wherein the photodetection element is an object to be evaluated, and the pulse train is a bit clock signal generated based on the groove signal in the function evaluation device. A device for functional evaluation, which is a pickup evaluation machine in a pickup production line, which evaluates the quality of a photodetector by measuring the pulse jitter during one period. 3. The function evaluation device according to claim 1, wherein the photodetector is an object to be evaluated, the groove signal is FM-demodulated, and a waveform passed through a low-pass filter is measured by an oscilloscope or the like. A device for functional evaluation that allows you to judge whether the ATIP / CLV servo function is good or bad by observing the ATIP eye pattern.