JPH01277328A - Video signal reproducing device - Google Patents

Abstract

PURPOSE:To reduce a time base error caused by a focus control by giving a focus error to a time base correcting means after restricting its band. CONSTITUTION:Electric power is supplied to a driving coil 10 by a driving circuit 9 in accordance with a focus error signal detected by an error detecting circuit 7, and hence a pickup is moved in the focusing direction so as to perform the focus control. On the other hand, a synchronizing signal separated by a separation circuit 13 is detected in its phase difference from a reference signal by a phase comparator 14 to be a time base error. A time base error signal is inputted to a driving circuit 17 of a variable delay line, and the variable delay line 12 operates in order to eliminate the time base error. In this case, a focus error detecting signal is inputted through a band filter to an adder 21. By this method, the variable delay line 12 is driven by the essential time base error and this focus error, thus eliminating the time base error caused by the focus control operation.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a video signal reproducing device that reduces time axis error components in optical disc reproducing devices and video equipment such as VTRs.

BACKGROUND OF THE INVENTION Conventional video signal processing equipment increasingly reproduces signals from information recording media such as disks and tapes. A problem that arises in this case is that when the medium itself rotates, a time axis error may remain in the reproduced video signal due to the effects of various devices involved in the rotation.

In particular, even if there is a device that corrects time axis errors, it will be a big problem if errors that exceed the correctable band occur.

Hereinafter, with reference to the drawings, the above-mentioned conventional video signal reproducing device will be explained using a video disc as an example.

FIG. 3 shows a block diagram of a conventional video disc video signal reproducing apparatus. In Figure 3, 1 is a disk, 2 is a motor that rotates the disk, 3 is a motor control circuit that controls the motor to constant rotation, 4 is a pickup that reads signals from the disk surface using a laser, and 5 is light reflected from the disk. 6 is a focus control circuit that focuses the pickup so that it accurately traces the disk surface, and 7 is an error detection circuit that detects focus errors using signals from the head amplifier. The circuit includes a phase compensation circuit 8 for stabilizing the control loop, a drive circuit 9 for driving the pickup according to the error, and a coil 10 for electromagnetically moving the pickup.

Further, 11 is a time axis error correction device that takes time axis errors from the video signal, 12 is a variable delay line (v, n, L,) that is a means for correcting the time axis, and 13 is a time axis error correction device that extracts a synchronization signal from the video signal. A signal separation circuit, 16 a reference signal generation circuit that generates a reference signal (ref'H sink) with the same frequency as the horizontal synchronization signal, and 14 a separated synchronization signal and rer.
A phase comparator that compares the phase of the H sync, 16 a phase compensation circuit to stabilize the time axis correction loop, 17 a drive circuit that drives the variable delay line according to the error, and 18 a time axis corrected image. A signal processing circuit 19 outputs a video signal for outputting a signal to a television.

The operation of the video signal reproducing apparatus configured as described above will be described below.

The disk 1 is rotated by a motor 2, and its rotation speed is controlled to be constant by a motor control circuit 3. At this time, a signal portion called a bit on the disk is detected as a reflected signal by the pickup 4 using a laser beam, and the reflected signal is converted into an electrical signal by the head amplifier circuit 6 and output to each section.

In general, a disk has vertical shape distortion called surface runout, and its relative position with respect to the pickup 4 changes with time. This surface runout component occurs when the rotational speed of the disk is 180 Qrpm.

Sometimes, it is considered to have a frequency band ranging from a fundamental frequency component of 30 Hz to I KHz to 2 KHz, which is considered to be a fine component on the disk.

Therefore, in order to read the signal accurately, it is necessary for the pickup to accurately focus on the reflective surface on the disk, and the circuit for this purpose is the focus control circuit 6.
It is.

In the focus control circuit 6, the laser beam reflected from the head amplifier circuit 5 is first converted into an electric signal by a four-divided photoelectric conversion device as shown in FIG.

At this time, in the case of the astigmatism method, when the focus is out of focus, the spot shape on the photoelectric conversion device becomes an ellipse,
A difference occurs in the sum of the diagonal parts of the four divisions.

- Furthermore, when the focus is on, the spot shape on the photoelectric conversion device is a perfect circle, and equal output can be obtained in each of the four divided parts. Therefore, since the sum signal of each diagonal portion is outputted from the head amplifier 5, the focus error can be obtained by taking the difference between the sum signals in the error detection circuit 7.

The obtained focus error is converted into an appropriate signal band and amplitude by a phase compensation circuit 8 for stabilizing the loop, and is transmitted to a drive circuit 9. According to the signal, the drive circuit 9
Power is supplied to operate the drive coil 10 in the focus direction of the pickup 4.

In this way, a loop is constructed and focus control is performed.

On the other hand, Heradore/Zoro also outputs a composite signal of the photoelectric conversion device divided into four parts, and a video signal is obtained from the RF multiplied signal. However, if this continues, fluctuations in the time axis direction will remain due to jitter caused by eccentric components of the disk, resulting in a distorted image.

Therefore, the time axis correction device 11 corrects this fluctuation in the time axis direction.

In the time axis correction device, first, the variable delay line (VDL) 12
The signal separation circuit 13 separates the synchronization signal from the signal that has passed through the signal separation circuit 13 . In this case, a burst signal may be used instead of the synchronization signal, but for the sake of simplicity, the synchronization signal will be used in the explanation.

The separated synchronization signal is input to the phase comparator 14 together with a reference horizontal synchronization signal (hereinafter referred to as rafH) generated from the reference signal generation circuit 16. The phase comparator 14 outputs as a voltage how much the phase of the separated synchronization signal differs from the reference, and this becomes a time base error.

Further, the output of the phase comparator 14 is inputted to the drive circuit 16 through a phase compensation circuit that performs phase compensation so that the time axis control operates stably. The drive circuit 17 outputs a signal to control the variable delay line 12 according to the input signal, and the variable delay line 12 thereby works to reduce the time base error. The configuration of the drive circuit 17 differs depending on the variable delay line 12, but for example, if the variable delay line is a COD, it is a voltage controlled oscillator;
If the variable delay line has an MO8 configuration, it becomes a power supply control circuit.

In this way, the time axis correction device is configured, and the output of the variable delay line 12 is a video signal with no time axis error and no fluctuation. However, the band of time axis correction control is limited by its components, and correction may be difficult, especially at high frequencies. The signal is inputted to 18 and becomes a signal that can be output to a TV or the like, and is outputted to the TV from an output 19.

As described above, the video signal from the disc 2> is reproduced.

Problems to be Solved by the Invention However, the above configuration has a problem in that it is difficult to eliminate time axis errors caused by focus control.

For example, this may occur in principle depending on the pickup driving method as shown in FIG. Now, in FIG. 6, 30 is the optical section of the pickup, 31 is the optical section of the optical section, 32 is a support that connects the optical section 3o and the optical section 31, and the optical section 30 is connected to the optical section by the coils 33 and 34. Moved in the direction of focus. 36 is
This is a drive circuit that drives the coil.

At this time, the optical section 30 moves up and down by the support body 32 around the fulcrum of the national polity 31, but at that time, as shown in FIG. 6, during the up-and-down movement, a movement occurs in the left-right direction. If this coincides with the rotation direction, it is considered to be a time axis error.

Furthermore, regardless of the configuration, even if the pickup follows the surface runout, an optical path difference occurs instantaneously, which may result in an error on the time axis.

In either case, a time axis error occurs in the movement in the focus direction, and especially if the focus control band extends to a high point, the error will exceed the time axis error correction control band and appear on the TV screen. There are drawbacks.

In view of the above problems, the present invention provides a video signal reproducing device that can reduce time axis errors caused by focus control.

Means for Solving the Problems In order to solve the above problems, the video signal reproducing device of the present invention includes a time axis correction device, a focus control device, and an adder for adding a signal to the time axis correction means, This apparatus has a configuration in which a focus error signal is added to the time axis correction means by an adder.

According to the present invention, with the above-described configuration, the time axis error caused by focus control is also removed by the time axis correction means, so that it is possible to realize a video signal reproducing apparatus with less residual jitter.

EXAMPLE Hereinafter, an example of the present invention will be described with reference to the drawings.

FIG. 1 shows a block diagram of a video signal reproducing apparatus according to an embodiment of the present invention.

In FIG. 1, 2o is a bandpass filter that extracts the error detection signal of the focus control device, and 21 is an adder that adds the signal to the variable delay line drive circuit of the time axis correction means.

Note that 1 is a disk, 2 is a motor, 3 is a motor control circuit, 4 is a pickup, 5 is a head amplifier, 6 is a focus control circuit, 7 is a focus error detection circuit, 8 is a phase compensation circuit, and 9 is a drive circuit. , 1Q is a drive coil,
11 is a time axis correction control circuit, 12 is a variable delay line, 13
14 is a signal separation circuit that extracts a synchronization signal from a video signal.
is a phase comparator, 15 is a reference signal generation circuit, 16 is a phase compensation circuit for the time axis correction control circuit, 17 is a drive circuit for a variable delay line, and 18 is for outputting a signal whose time axis error has been corrected to a TV. The signal processing circuit 19 is an output terminal, and the operation of the video signal reproducing apparatus configured as shown in FIG. 2 will be explained below with reference to the drawings. Regarding focus control, it is similar to the conventional example, and the error detected by the error detection circuit 7 is output to the drive circuit 9 through the phase compensation circuit, and the drive circuit 9 applies power to the drive coil 1o in accordance with the signal. is supplied to move the pickup in the focus direction, and focus control is performed.

On the other hand, the time axis correction control circuit 11 is also similar to the conventional example, and the synchronization signal separated by the signal separation circuit 13 is sent to the phase comparator 1.
4, the phase difference from the reference retH is detected and becomes a time axis error. The time axis error signal is input to the variable delay line drive circuit 17 through the phase compensation circuit 16, and the variable delay line 12 operates so as to eliminate the time axis error. The signal from which the time axis error has been removed is processed by the signal processing circuit 18 so that it can be output to the TV, and is output to the pTV via the output terminal 19. At this time, the focus error detection signal is input to the adder 21 with its band limited by the bandpass filter. Therefore, the variable delay line is driven by the original time axis error and this focus error, and performs focus control operation. It also operates to remove the generated time axis error.

If the band of the bandpass filter includes a signal exceeding the band of the time axis correction control loop, it will correct the time axis error that cannot be detected by the time axis correction control loop.

However, in this addition, there are times when it is necessary to perform phase adjustment appropriate to the focus error.

In this way, by adding the time axis error generated in the focus control to the time axis correction means, it is possible to cover the part where the time axis correction control circuit cannot respond.

Further, the present invention can also be applied to a feedforward type time axis correction means as shown in FIG. 2 as a second embodiment of the present invention. In FIG. 2, 40 is a video signal input terminal, 41 is a burst separation circuit for extracting the burst signal from the video signal, and
42 is a phase comparator 2; 43 is a variable delay line; 44 is a focus error signal input terminal; 45 is a bandpass filter; and 46 is an adder.

12 variable delay lines, 13 synchronous separation circuits, 14 phase comparators, 15 reference signal generation circuits, 160 phase compensation circuits,
The drive circuit 17, the signal processing circuit 18, and the output terminal 19 operate in the same manner as in the first embodiment described above.

The operation will be explained below. In FIG. 2, the output of the burst separation circuit 41 is the reference subcarrier frequency signal (rafs/C) generated from the reference signal generation circuit 16.
After the phase difference is detected, the signal is input to the variable delay line 43 and the time axis error left behind by the variable delay line 12 is corrected.

Further, the adder 46 adds a signal whose focus error band is limited, so that the time axis error caused by the focus operation can be removed with high sensitivity.

As described above, according to this embodiment, residual jitter outside the band can be effectively removed by adding the focus error to the time axis correction means.

Effects of the Invention As described above, the present invention is capable of removing residual jitter outside the band of the time axis correction circuit by adding focus error to the time axis correction means in a band-limited manner, and its practical effects are great. There is something.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of a video signal reproducing device according to a first embodiment of the present invention, FIG. 2 is a partial block diagram of a video signal reproducing device according to a second embodiment of the present invention, and FIG. 3 is a conventional block diagram of a video signal reproducing device according to a second embodiment of the present invention. 4 is a block diagram of a video signal reproducing device, FIG. 4 is a block diagram of a 4-split photoelectric conversion device used to detect general focus errors, and FIG. 6 is a simple configuration diagram of the optical part of the pickup. FIG. 3 is a side view showing the operation of the optical section. 6...Focus control block, 11...
...Time base correction block, 12...Variable delay line, 17...Variable delay line drive circuit, 2Q...
... Bandpass filter, 21... Adder. Name of agent: Patent attorney Toshio Nakao and 1 other person/No. 4121 Figure 5 Figure 6+

Claims (2)

[Claims] (1) A time axis correction device that corrects time axis fluctuations included in a video signal by a time axis correction means, a focus control device that controls a focal position of an optical signal detection means, and a time axis correction of the time axis correction device. 1. A video signal reproducing apparatus, comprising: an adder for adding a signal to the means, and a focus error signal of the focus control device is added by the adder to the time axis correction means of the time axis correction apparatus. (2) The video signal reproducing device according to claim 1, wherein the focus error signal of the focus control device is band-limited and added.