JPS6213746B2 - - Google Patents

Description

TECHNICAL FIELD The present invention relates to a servo device in a recorded information reading device, and more particularly to a servo device that functions as a time base collector for controlling movement of a recorded information detection point in the tangential direction of a video track.

BACKGROUND ART Optical video disks record video signals by forming minute dents (bits) in the form of spiral tracks on their surfaces in accordance with video signals. When reproducing such a video disc, the disc is rotated at a predetermined rotation speed, and a spot hole focused on the video track is irradiated, and changes in the intensity of the reflected light or transmitted light are converted into electrical signals. The video signal is read, the video signal and various control signals such as horizontal and vertical synchronizing signals are detected separately and the video signal is reproduced.

Such playback devices include a so-called spindle servo for controlling the video disk to a predetermined rotational speed, and a device that adjusts the position of spot light irradiated onto the video disk surface in the tangential direction of the video track to correct the time base of the playback signal. It is equipped with a tangential servo and the like for control, and these are essential for obtaining good playback video signals.

FIG. 1 is a schematic block diagram of a conventional spindle servo and tangential servo system, and includes a reference signal generator 1 that generates reference signals of 400 kHz and 3.58 MHz, which are color subcarrier signals, which are synchronized with each other. The 400kHz signal, which is one output, is converted to 4k by the 1/100 frequency divider circuit 2.
The frequency is divided into Hz and input to the phase comparator 3. on the other hand,
The recorded information on the disk 4 is reproduced by a reproduction device 5, and from this reproduction signal, a 400kHz signal component as a pre-recorded control signal is separated by a separation circuit 6 and divided into 4kHz by a 1/100 frequency division circuit 7. After that, the signal is input to the phase comparator 3. The frequency divider circuit 7 can be reset by the output of the vertical synchronization separation circuit 16.

The color subcarrier signal from the reference signal generator 1 is input to the phase comparator 8, and the other input is a signal obtained by separating the color burst signal (3.58MHz) from the reproduction signal reproduced by the reproduction device 5 by the separation circuit 9. is used. An error signal is output from the comparator 8 according to the phase difference between these two signals. This error signal is converted into a drive signal by the drive circuit 10 and drives the tangential mirror 11 to rotate. By this rotation of the tangential mirror 11, the spot light is shifted in the tangential direction of the video track, thereby performing a time base correction.

Further, the error signal of the comparator 8 is integrated by the integrating circuit 12, and then added to the output signal of the previous phase comparator 3 in the adder 13, and the added output is converted into a drive signal for the motor 15 by the drive circuit 14. This system controls the motor to precisely control the rotation of the disk.

In this configuration, the reference 4kHz and the reproduced 4kHz phase difference signal A (output of phase comparator 3)
When comparing the magnitude of signal B (output of integrator 12) based on the reference 3.58MHz and the reproduced 3.58MHz phase difference signal, 3.58M
When comparing Hz, the gain of the comparator itself is higher and the accuracy and response characteristics are better, and furthermore, it is easier to synchronize the rotation of the motor than with the mirror, so signal B is larger than signal A. becomes. In addition, in order to stabilize the average operating point of the dangential servo, by resetting the frequency divider circuit 7 with the regenerated vertical synchronization signal from the vertical synchronization separation circuit 16, the loop gain of the control signal B is set higher than that of the control signal A. It's getting bigger. Therefore, the motor is synchronously controlled by the control signal B according to the phase difference of the color burst signals.
This takes priority over the control using the phase difference signal A of the 4kHz signal.

When operating two or more players at the same time to monitor the same playback image and view the video disc screen, each player is given priority because the motor spindle servo is given priority by the large control signal B mentioned above. The rotations of the two motors may become out of synchronization, resulting in incomplete synchronization, and as a result, a time lag occurs between the reproduced images, which is undesirable.

SUMMARY OF THE INVENTION An object of the present invention is to eliminate the above-mentioned drawbacks when two or more devices are operated simultaneously, and to provide a servo device for a recorded information reading device that has better servo characteristics.

In the servo device of the recorded information reading device according to the present invention, after the reproduction frame synchronization is established by the coarse adjustment means using the spindle servo system and the reproduction horizontal synchronization is established, the reproduction signal is adjusted by the fine adjustment means such as the dangential servo system. It is characterized by making fine adjustments to the time base.

Example The present invention will be explained below with reference to the drawings.

FIG. 2 is a block diagram of an embodiment of the present invention,
The horizontal and vertical composite synchronization signals from the reference decoded synchronization signal generator 21 including the subcarrier signal are input to the synchronization separation circuit 22 via switch _S1 , where they are separated into a frame synchronization signal F and a horizontal synchronization signal H, each of which has a frame phase. Comparator 23 and horizontal phase comparator 24
This is one input. Other inputs to these comparators 23 and 24 are a reproducing device 2 for reproducing information on the disk 25.
These are the reproduction frame and horizontal synchronization signal obtained by separating the reproduction signal according to No. 6 in the synchronization separation circuit 27.

Further, a frame lock detector 28 is provided which detects whether the phases of the reference frame signal and the reproduced frame signal match, and similarly detects the phase lock between the reference horizontal synchronizing signal and the reproduced horizontal synchronizing signal. A horizontal lock detector 29 is provided. The frame lock detector 28 is configured to generate a first control signal when the phases of both frame signals match, and generate a second control signal when they do not match, so that the frame lock is completely locked. When not, the switch S ₃ is connected to the upper side and inputs the output of the frame comparator 23 to the drive circuit 30 as a rotation control signal for the motor 31. On the other hand, when frame lock is achieved, a first control signal is generated from the detector 28 to switch the switch _S3 downward. Therefore, the input of the drive circuit 30 is the horizontal comparator 24.
The output is

Subcarrier signal from synchronization signal generator 21
SC is 3.58MHz phase comparator 32 via switch _S2
The other input is a color burst signal separated from the reproduced signal by a burst gate circuit 33. The output of the comparator 32 is sampled and held by a sample and hold circuit 34, converted into a control signal, and inputted to a gate circuit 35 as a switching means. A gate pulse generation circuit 36 is provided for generating a gate signal for the burst gate 33 and each control signal for the sample and hold circuit 34 from the reproduced composite synchronization signal.

The output signal of the gate circuit 35 is directly input to the tangential mirror drive circuit 37 to control the rotation of the tangential mirror 38 and correct the time base. Further, the output of the gate circuit 35 is passed through a reduction filter 39 to the motor drive circuit 30.
is being input to. The gate control signal of the gate circuit 35 includes a second control signal of the frame lock detection circuit, a third control signal generated from the horizontal lock detection circuit 29 when the phase of the horizontal signal is not locked, and furthermore, Blanking signal generator 40 that separates and detects the vertical blanking signal from the reproduced signal
An output signal of a gate drive circuit 41 that forms a gate signal from the output of the gate drive circuit 41 is used.

In addition, if external synchronization is required, switch S ₁ and
S ₂ and external composite synchronization signal (EXT
COMP SYNC) and an external subcarrier signal (EXT SC) can each be used as reference signals.

In this configuration, spindle servo is first performed by a phase comparison loop between the reference frame signal and the reproduced frame signal, and when frame lock is achieved, a switch is activated by the frame lock detector 28.
_S3 is switched to form a horizontal synchronization signal phase comparison loop. Therefore, if the reference frame and the reproduced frame signal are out of phase for some reason, a frame phase comparison loop is formed again to achieve frame synchronization and then shift to horizontal synchronization. This will be done definitely and quickly. In addition, after frame synchronization, a horizontal signal (15.75kHz) phase comparison loop is formed, so frame phase comparison and even conventional 4kHz
Compared to phase comparison, this method has advantages such as the gain of the comparator itself being higher and accuracy and response being better, so that one control input signal of the motor drive circuit 30 can be made accurate.

Tangential servo 50 surrounded by dotted lines
Partly, since no color burst exists during the V (vertical) blanking period, burst phase comparison is impossible and the gate circuit 35 is turned off during the V blanking period. Furthermore, if time base correction is performed after frame synchronization and horizontal synchronization, accurate correction operations can be performed. While the second and third control signals are being generated, the gate circuit 35 is turned off to accurately correct the time base. Furthermore, when phase comparison of color bursts is performed during this period, the phase difference between the reference subcarrier signal and the reproduced color burst signal is often large, and therefore, unless the difference signal is cut off by the gate circuit 35, the motor Although the control signal B' to the drive circuit 30 increases, the gate circuit 35 cuts off the input signal B' to the motor drive circuit 30 during this period. Therefore, a large component of the control input signal B' from the reduction filter 39 corresponding to the time base error signal to the drive circuit 30 is cut off.

The reason why the phase difference signal of the color burst of the tangential servo system is input to the drive circuit 30 of the spindle servo system via the reduction filter 39 is that the tangential servo loop only removes the variation. Therefore, since the DC gain is zero, and it is necessary to stabilize the average operating point of the loop, the high frequency component of the difference signal from the phase comparison is removed by a filter 39, and the DC error component is sent to the spindle servo system. It is added to.

Effects of the Invention As described above, according to the present invention, the configuration is such that a large difference signal component that causes malfunctions among the color burst phase difference signals is cut off, so that proper tangential servo operation can be performed. For one input A' of the spindle servo system motor drive signal, another input corresponding to the tangential servo signal
Since B′ does not become extremely large, it is easy to synchronize between the devices, especially when two or more devices are operated simultaneously, so that the reproduction frames of two or more devices are always the same without being out of sync. The reproduced image can be monitored.

In the above, an optical information reading device has been described, but it is also applicable to other electrostatic type information reading devices.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of a conventional spindle servo and tangential servo system, and FIG. 2 is a block diagram showing an embodiment of the present invention. Explanation of symbols of main parts, 23...Frame phase comparator, 24...Horizontal synchronization phase comparator, 28...
Frame lock detector, 29...Horizontal lock detector, 30...Motor drive circuit, 32...Color burst phase comparator, 35...Gate circuit, 37...
...Tangential mirror drive circuit.

Claims (1)

[Claims] 1 Means for performing spindle servo by outputting a phase comparison between a reproduced frame synchronization signal and a first reference signal, and a means for performing a spindle servo by outputting a phase comparison between a reproduced frame synchronization signal and a first reference signal, and a means for performing phase synchronization between a reproduced horizontal synchronization signal and a second reference signal after the reproduction frame synchronization signal is phase-synchronized with the first reference signal. means for performing the spindle servo based on the comparative output;
A servo device for a recorded information reading device, comprising means for finely adjusting time axis correction of a reproduced signal after phase synchronization with a reference signal.