JPS6145431A - Time axis control device - Google Patents

Abstract

PURPOSE:To prevent color reproduction from interruption even if a CLV disc is scanned during the reproduction by making the center of operation coincide with that of comparison on the basis of a DC coupling method and shifting an inclination signal by a phase corresponding to a half of its period. CONSTITUTION:A tangental servo system is constituted of a phase error detector (PD)1, a buffer amplifier 4, an equalizer amplifier 6, a tangental switch S5, a drive amplifier 7, an actuator 8, and a tangental mirror 9 and a spindle servo system is constituted of a PD2, a spindle loop S16, an adder 10, an aqualizer amplifer 13, a drive amplifier 14, and a spindle motor 15. When the spindle servo system is locked, a spindle lock signal is supplied to the S16 to open the S16 and also supplied to the S5 through an inverter 17 to close the S5. Thus, the operating point of the mirror 9 is held at the center of the operating range and converged upon the rotational phase, so that the color reproduction is scanning operation can be prevented from interruption.

Description

TECHNICAL FIELD The present invention relates to a time axis control device, and more particularly to a time axis control device in a disc-shaped record carrier reproducing device.

111'' A block diagram for explaining a conventional time axis control device in a disk-shaped record carrier reproducing device is shown in FIG. This time axis control device is composed of a spindle servo system that is a coarse adjustment control system and a tangential servo system that is a fine adjustment control system. Each of these servo systems has separate time axis error detectors, ie, phase error detectors (hereinafter simply abbreviated as PD) 1 and 2. PDl is a phase comparator for tangential error detection,
It is of a type in which a slope waveform formed from a reference signal from a reference oscillator 3 is sampled and held using sample pulses obtained from a read signal, such as a reproduced video signal. On the other hand, P
O2 is a phase velocity comparator for spindle servo error detection, and is used to perform time axis control l loading and phase cycle. The output of PDl is a buffer 7 amplifier 4, a DC blocking capacitor C1, a tangential lube switch 5, an equalizer amplifier (EQ) 6, a DC blocking capacitor C2, a drive amplifier 7, and an actuator coil 8 for driving the tangential mirror. The tangential mirror 9 is driven via the tangential mirror 9. This rotation of the tangential mirror 9 causes a light spot for information detection to be spread eight times in the tangential direction of the recording track.

The output of PO2 is fed to one input of the adder 10,
The output of the tangential servo system equalizer amplifier 6 is supplied to the other input of the adder 10 through a loop 12 including a low-pass filter (hereinafter abbreviated as LP) 11.The output of the adder 10 is supplied to the other input of the adder 10. It becomes a drive signal that drives the spindle motor 15 via the amplifier 13 and the drive amplifier 14.

In such a time axis control system, the response of the spindle motor 15 is not sufficient to absorb the jitter included in the reproduced video signal, so the jitter of high frequency components that cannot be absorbed by the spindle servo system is removed from the response frequency band. It is configured to be removed using a wide tangential servo system. The tangential servo system has a wide response frequency band, but can only correct the phase within the deflection angle range of the tangential mirror 9, whereas the spindle servo system has a narrow response frequency band, but because it is a rotating system, it can only correct the phase within the deflection angle range of the tangential mirror 9. There is no limit to the phase correction range. This time axis control device further includes:
By using these properties of the tangential servo system and the spindle servo system, the spindle servo can be configured so that the operating point of the tangential servo system is at the center of its correction range. ing.

Here, the center of the correction range means the mechanical and optical center of the deflection angle when a tangential mirror is used as a time axis control means, and the center of the deflection angle when a COD is used. Means the center of operation of the range. Both do not necessarily coincide with the operating center of the phase detector.

In the time axis control device configured as above,
First, the spindle servo system operates to pull the rotation of the spindle motor 15 to periodic rotation, and when the phase cycle is reached, this is detected and a spindle lock signal is supplied to the loop switch 5 of the tangential servo system to close it. Operate the tangential servo system. The tangential mibo group is a jitter of high frequency components that cannot be absorbed by the spindle servo system, for example, an eccentric component that occurs every rotation of the disk (in the case of an NTSC CAV disk, 30
Hz). When the Tangential Mibo system operates, the low frequency component of the output of the equalizer amplifier 6 is applied to the spindle servo system via the LPFI 1 of the loop 12. The phase sensitivity of this low frequency signal is PO2
Since it is sufficiently high compared to the phase sensitivity of the signal output from
After the tangential lube switch 5 is closed, the spindle motor 15 rotates so that the potential of the loop 12 becomes zero. The tangential mirror 9 has DC cut off by the DC blocking capacitor C2, and one end of the capacitor C2 is grounded by the resistor R. Therefore, in the operating state, the DC potential at both ends of the capacitor C2 becomes zero, and the tank No DC charging/discharging current flows through the tangential mirror 9 through the capacitor C2, and the tangential mirror 9 operates at its optical center.

Tangential servo system uses DC blocking capacitor C
1 also cuts the DC current, but as mentioned above, there is no problem because the low frequency jitter is absorbed by the spindle servo system, and the capacitor C1 is rather the time axis control device has two PDIs J5 and 2. Therefore, since the respective zero points do not exactly coincide with each other, this is provided to prevent the influence of offset that occurs in the circuit system.

As described above, the conventional time axis control device includes AC coupling in part in order to eliminate the influence of the tangential meap and the offset occurring within the spindle loop. However, in a transient state, such as when a tangential I-bo group locks in (■), the lock phase immediately after lock-in does not become zero, but gradually converges toward zero. . The reason for this is that in the part that is AC coupled, the terminal voltage of the capacitor before lock-in is not the same as the terminal voltage during steady state lock-in, and there is a DC-like initial condition at the time of lock-in.
Although it takes time to absorb this.

In addition to this, CLV (C
instant L 1near Velocity
) When performing a scanning operation on a disk, it was not possible to obtain a color image.

The reason is that, first, in the conventional system, the spindle servo system operates so that the tangential mirror or COD becomes the center of operation immediately after lock-in; or narrow,
This configuration is essential. However, the locked phase is not necessarily at the center of the phase comparator, and may fall outside the comparison range in some cases.

Second, the operating range of a tangential mirror or COD is normally limited to about 40μ5eCDt1;
The phase lock point is every 1H (H is 1 horizontal period), that is, NTS
In the case of the C method, since the signal exists every 63.5 μsec, lock-in may not be possible depending on the phase state immediately before lock-in. This is because on a CLV disk, the horizontal periodic signals are not lined up in a straight line, so when locking in after scanning, a time axis correction aperture of ○, '51-1 at the maximum may occur, and the field of view of the pickup is narrow. In this case, if you try to perform a maximum correction of 0.5H, tracking,
This is because the focus servo system may become disconnected.

Due to the above two reasons, conventionally, when scanning a CLV disk with J5, the lock-in operation is slow.
Color images could not be obtained because the lock-in period was absent or very short.

SUMMARY OF THE INVENTION An object of the present invention is to provide a time-based i11 device that can perform good color reproduction even when performing a scanning operation while reproducing a CLV disk.

The time axis control according to the present invention detects that the phase of the sample pulse periodic to the reproduced signal deviates from the slope section of the slope signal having the same period as that of a predetermined reference signal. is shifted by a phase ■ corresponding to 1/2 of its period, the level of this ramped signal is sampled and held by a sample pulse, and this hold output is used as a phase error signal, and based on this phase error signal, It is characterized in that it performs time axis correction of the reproduced signal and that the servo circuit that performs this correction is DC-coupled.

In other words, the first mountain range mentioned above can be solved by aligning the center of operation and the center of comparison using the DC direct coupling method, and the second reason can be solved by using a 1/2H shift. The upper lock point is 63.2 ("=32μs
By compressing the correction m for each (cc), it is possible to reproduce a good color image even if a scanning operation is performed while a CLV disk is being reproduced.

Embodiment FIG. 2 is a block diagram of an embodiment of the present invention. In the figure, the same elements as in FIG. 1 are denoted by the same numbers. 1st
The difference from the diagram is basically that the DC blocking capacitor of the tangential servo system is removed and a spindle loop switch 16 is provided between the PD 2 of the tangential servo system and the adder 10. And, the circuit shown in FIG. 5 was used as PDl. The reason for removing the DC blocking capacitor is to set the phase 4rA value as one point in the tangential Mibo base and quickly converge to the target phase by removing the time constant element at low frequency. The reason why the spindle loop switch 16 is provided is that when the spindle servo is turned, the spindle loop switch 16 is opened and the tangential lube switch 5 is closed. This is to operate the spindle servo system and the spindle servo system.

The tangential Mibo group is composed of PDl, buffer 1 amplifier 4, equalizer amplifier 6, tangential lube switch 5, drive amplifier 7, actuator coil 8 and tangential mirror 9 (1"4), while the spindle The servo system is composed of PO2, spindle loop switch 16, adder 101, equalizer amplifier 13, drive amplifier 14 J5, and spindle motor 15. Spindle lock signal is directly supplied to spindle loop switch 16, and tangential A spindle lock signal is supplied to the lube switch 5 via an inverter 17.The loop 12 having the LPFII is provided for the same purpose as the conventional time axis control device shown in FIG. Although a lower frequency component is detected than the input of the amplifier 7, the voltage application point A to the actuator coil 8 or the actuator coil 8
Detection may also be performed from detection point B of the current flowing through the current.

Next, the operation of this embodiment will be explained for the case where a CLV disc is played back. Generally, when the pickup is forcibly moved in the radial direction during playback of a CLV disc, that is, when it is scanned, the operating point of the tracking mirror in the tracking servo system that tracks the recording track is shifted to the periphery of the field of view. In order to detect this and relock the tracking mirror to the opposite side, the tracking operation is turned off for a predetermined period of time. Therefore, the third
As shown in the figure, a tracking-on period and a tracking-off time occur. During this OFF period, the tracking mirror returns toward the center of the field of view, but the ON period is sufficiently long compared to the OFF period, and visual disturbance of the image due to dropout of the reproduced signal due to tracking OFF is avoided. few.

In this embodiment, when the spindle servo system is locked during the tracking-on period, the spindle lock signal is sent to the spindle loop switch 1 in response to the operation normally performed during the scan operation during playback of a CLV disk.
6 to listen to the switch, while a spindle lock signal is supplied to the tangential lube switch 5 via the inverter 17 to operate the switch.

After the spindle servo system is locked, the tangential servo system and spindle servo system are
The operation is suspended due to the phase error signal output by Dl. As mentioned above, the tangential mirror 9 quickly converges to the target phase while keeping the operating point of the tangential mirror 9 at the center of its operating range. Can be locked.

Therefore, since the tangential servo system also operates during the tracking-on period, there is little jitter and a color image can be reproduced during the scan operation.

In the embodiments described above, the following problems arise due to variations in the load torque of the spindle motor 15.

Generally, the load torque of the spindle motor 15 varies depending on the diameter of the disc to be played. The diameter of the disk is 8 inches in addition to the standard 12 inches, and even if the disk is rotated at the same rotational speed, the load torque of the spindle motor will vary significantly depending on the viscous resistance of the air on the disk surface. Further, in a CLV disk having a diameter of 12 inches, the rotational speed differs by about three times between the inner circumference and the outer circumference during reproduction, which also causes variations in the load torque. When the load torque of the spindle motor fluctuates in this way, since the spindle motor 15 is driven by the input voltage of LPFll,
When the low frequency loop gain of the spindle servo system is very large, the phase fluctuation due to load torque fluctuation is sufficiently small, but when the low frequency loop gain of the spindle servo system is insufficient, the offset voltage proportional to the load torque This will occur at the input section of . Since the DC blocking capacitor is not staged, this offset voltage is input to the drive amplifier 7, and as a result, the operating point of the tangential mirror 9 deviates from the center point. In order to avoid this phenomenon, increasing the low frequency gain of the spindle servo system has the disadvantage that it takes a long time to lock in.

FIG. 4 shows a block diagram of another embodiment of the present invention that solves this problem. In this embodiment, a loop 19 including an LPF 18 is provided between the spindle motor 15 and the adder 10 in the embodiment shown in FIG. This makes it possible to prevent the operating point of the tangential mirror 9 of the tangential servo system from shifting due to load torque fluctuations.

In the embodiment described above based on FIGS. 2 and 4, the jitter with the largest amplitude among the jitters absorbed by the tangential servo system is the eccentric component that normally occurs every rotation of the disk, and this is For NTSG disks 3
Since the frequency exists below 0 Hz, the gain of the tangential servo system is generally configured to increase at low frequencies.

However, increasing the low frequency gain in this manner has the disadvantage that lock-in becomes slow, and when the CLV scan speed is increased, the television monitor tends to be unable to color lock. To prevent this phenomenon, PDl
FIG. 5 shows a phase comparator circuit used for this purpose.

In the figure, the sample pulse becomes a control signal for a sample switch 21 via an AND gate 20, and other inputs to this gate 20 include a monostable multi-by-break (M
The output of MV) 22 is supplied via an inverter 23. Further, the sample pulse and the MMV output are supplied to an AND gate 24, and a flip-flop (FF) 25 is set and reset by the gate output, and the output of this FF 25 controls a switch 26. This switch 26 selects the output of the reference oscillator 27 and the output passed through the inverter 28 and uses it as a trigger signal for the MMV 22 . This trigger signal triggers the sawtooth wave generation circuit 29 to generate a sawtooth wave signal (slope signal). The sawtooth signal is sampled by the sample switch 21, the sampled output is held by the bold capacitor 30, and this held output passes through the buffer 7 amplifier 31 and becomes a time axis error.

The circuit operation of such a configuration will be explained with reference to the waveform diagram of FIG. FIGS. 8(A) to 8(F) correspond to signals (A) to (F) of each part of the circuit of FIG. 5, respectively. When the frequency of the reproduced signal decreases with respect to the reference signal, the sample point rises on the slope of the sawtooth signal, but eventually the sample pulse (D ) will appear. This is detected by the AND gate 24 and F
F25 will be inverted, reversing the polarity of the reference signal that triggers MMV22. Therefore, the phase of the sawtooth signal is shifted by 172 periods and the sample pulse (D
) will be captured near the center of the slope of the sawtooth signal. Then, the sample point ascends the slope again, and this operation is repeated, and as shown in FIG. 9, when the frequency of the reproduced signal becomes small, the sample point exists on the positive side as shown in (A). It turns out. Further, when the frequency of the reproduced signal is large, when the sample point descends the slope and enters the discharge period of the capacitor, this is detected by the circuit consisting of the inverter 23 and the gate 20, and the sample pulse during that period is cut off. , sampling is no longer done. Therefore, since the phase of the sawtooth signal is shifted by 1/2 period, the sample points as a whole fall on the negative side as shown in (B).

By doing this, a unidirectional polarity error signal is generated even in response to a frequency shift, so it is advantageous to also have a frequency detection function. Therefore, when using this phase error detector, the maximum correction m is 1/2 ±0
．． 258 (±15 μsec), it is possible to realize a time axis side Vt+ device that is stable in an extremely short time. - FIG. 6 shows an embodiment of a time axis control device configured with one phase comparator circuit, and the same elements as the v5 elements in FIG. 4 are denoted by the same numbers. A loop 34 including an attenuation resistor 33 is provided between the phase comparison circuit 32 and the adder 10. This damping resistor 33 allows the tangential lube switch 5 to open when the tangential lube group is in the oven, and in the spindle servo system, the spindle error signal is no longer 1"J from the loop 12, so the error signal is directly output from the phase comparator circuit 32. This is to calculate 1q.When the tangential servo system locks,
Since the output of the phase comparison circuit S2 is zero, no signal is input from the loop 34 to the spindle servo system, and the rotation of the spindle motor 15 is controlled 2I by the signal from the loop 12.

In this practical hM example, when scanning the CLV disk is skipped, when the spindle servo system is locked during tracking on ryJ, a sample pulse signal is supplied to the tangential lube switch 5 and the switch is closed. As in the embodiment described above, the tangential servo system quickly converges to the target phase while maintaining the operating point of the tangential mirror 9 at the center of its operating range.
As a result of rapid phase locking of the Tangential Mibo, color images can be reproduced during scanning operations.

In the above embodiment, the case where fine adjustment of the time axis is performed using a tangential mirror was explained.
CL
Color images can be reproduced during the V-disc scanning operation. FIG. 7 is a block diagram showing an embodiment in this case. Elements that are the same as those in the embodiment of FIG. 4 are designated by the same numbers.

The RF multiplied signal is demodulated into a video signal by a demodulator 35 and outputted via a CCD 36. C0D36 is driven by a clock generated by a voltage controlled oscillator (VCO) 37. A periodic signal separation circuit 38 separates a periodic signal from the video signal output from the CCD 36, and supplies this periodic signal to a sample pulse generator 39 to form a sample pulse. The circuit configuration of the time axis control device is circuit I in Figure 4.
Since it is the same as the M configuration, the explanation will be omitted. VCO37 is
A clock is generated according to the output pressure of the tangential servo drive amplifier 7, and time axis correction of the video signal is performed in the C0D36.

Even in the actual side-down operation, the operation is similar to that of the embodiment shown in Fig. 4.
Color image when scanning CLV disk] Z! can be played back.

As described in detail, according to the time axis control device of the present invention, the operation center and the comparison center are made to coincide with each other by the direct current coupling method, and the upper lock point is apparently moved within about 32 μsec by the 1/2H shift. Since I changed it to gj, CLV
Even if a scanning operation is performed while a disc is being played back, there is no interruption in color playback, and a visually pleasing color image can be obtained.

[Brief explanation of drawings]

Fig. 1 is a diagram showing a conventional time axis control device, and Fig. 2 is a diagram showing a conventional time axis control device.
A diagram showing an embodiment of the present invention, FIG. 3 is a diagram for explaining on/off of tracking, FIG. 4 is a diagram showing another embodiment of the present invention, and FIG. 5 is a diagram for explaining tracking on/off. Figure 6 shows a comparison circuit, and Figure J and Figure 7 show other practical examples of the present invention.
The figure does not show yet another embodiment of the present invention, Figure 8 J3
and FIG. 9 are operational waveform diagrams of the circuit of FIG. 5. Explanation of symbols of main parts 1.2...Phase error detector 3...Reference oscillator 5...Tangential loop switch 9...
...Tangential mirror 10...Adder 11...LPF12.19...
・Loop 15...Spindle motor 16...Tangential lube switch 32
・・・・・・Phase comparison circuit

Claims (2)

[Claims] (1) a phase error detection means that generates an error signal according to the phase difference between the phase of the reproduced signal and the phase of a predetermined reference signal; and a servo circuit that corrects the time axis of the reproduced signal based on the error signal. A time axis control device for a recorded information reproducing apparatus having: the servo circuit is DC-coupled; and the phase error detecting means is configured to detect that the phase of the sample pulse periodic to the reproduction signal has the same period as the reference signal. means for detecting a deviation from the slope section of the slope signal having the slope signal and shifting the slope signal by a phase amount corresponding to 1/2 of the period of the slope signal; A time axis control device characterized in that the sample and hold is performed and the held output is used as the error signal. (2) A time axis control device, wherein the servo circuit includes a loop for detecting and feeding back a load current of a spindle motor.