JPH04123584A - Video reproducing device for magnetic disk - Google Patents

Abstract

PURPOSE:To generate a high speed consecutive shot video image in an excellent way at a fast speed by providing a synchronizing separator means and an adjacent track movement start control means starting the movement of a magnetic head by a magnetic head moving means synchronously with a vertical synchronizing signal separated by the synchronizing separator means to the reproducing device. CONSTITUTION:When a magnetic head 4 is at a position of a track A and a reproduced waveform of the track A is outputted, a track movement request command by a track moving key 9 is given to a system controller 3, then the system controller 3 receiving a vertical synchronizing signal separated from a reproduced video signal starts driving a stepping motor for driving the magnetic head 4 while awaiting the entry of the vertical synchronizing signal from a synchronizing separator circuit 8 after the arrival of the track moving request command. Thus, disturbance of synchronization due to input mistake of the vertical synchronizing signal is not caused at the reproduction side and moving picture in the vertical direction is not caused. Thus, the high speed consecutive shot video image is reproduced in an excellent way at a fast speed.

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial Application Field> The present invention relates to a magnetic disk video reproducing apparatus, and more particularly to an improvement in a technique for moving a magnetic head from a track being reproduced to an adjacent track.

<Prior art> In recent years, in place of conventional silver halide film cameras, optical image signals from a subject are converted into electrical image signals by an image sensor, and the electrical image signals (still image video signals) are transferred to conventional film cameras. A still video camera with a configuration that records magnetically on a corresponding magnetic disk has been put into practical use, and the electrical image signals recorded on the magnetic disk can be read with a magnetic head and played back for viewing on a monitor or printed as hard copies using a printer. (See Japanese Unexamined Patent Publication No. 183582/1982, etc.).

A recording system for recording video signals on a magnetic disk in such a still video camera has a configuration as shown in FIG. 5, for example.

That is, from the outer circumference to the inner circumference of the magnetic disk, there are 5 concentric circles.
There is a video signal recording area of 0 tracks, and 1 track is
Field recording takes place. Here, in the video signal recording area of the 50 tracks, the PC yoke is recorded so that the position of the PC yoke is 7H±2H (H is the horizontal scanning period) before the leading edge of the vertical synchronization signal added to the video signal. ,
The start and end of video recording, that is, the switching of the recording current, is made at the radial position of the magnetic disk passing through this PG yoke.

For example, when moving the magnetic head from a state in which track A is being played back to track B on the adjacent outer or inner track on a magnetic disk on which video signals are recorded in the configuration shown in Figure 5, a movement request is issued. If you move the magnetic head arbitrarily as it is, when the magnetic head is driven by a stepping motor, etc., and moves between tracks, the magnetic head will pass through the guard band area between the tracks, and the image will be distorted. The signal is interrupted, or this appears as momentary noise on the monitor.

Also, if the vertical synchronization signal is included in the part where the video signal is interrupted by passing through the guard band area as described above,
Even after the B track video is played back on the monitor, it takes time for the monitor to pull in the vertical synchronization, resulting in a phenomenon where the video flows up and down.

There is a reproducing apparatus having a configuration as shown in FIG. 6, which can solve the above-mentioned problems during tracking. 6th
In the configuration shown in the figure, a magnetic disk 51 is rotationally controlled by a spindle servo circuit 52, and a video signal read from the magnetic disk 51 by a magnetic head 53 is transmitted to an amplifier 54. Signal processing circuit 55 and switch SWI
It is designed to be output to the playback side via.

The magnetic head 53 is connected to a stepping motor drive circuit 5.
The stepping motor drive circuit 56 is controlled by a system controller 58 which receives a signal from a track movement key 57. . The system controller 58 also controls the spindle servo circuit 52, and a signal from the PG detection circuit 59 is input to the spindle servo circuit 52.

Here, when the magnetic head 53 is being moved by the stepping motor drive circuit 56, the system controller 58 switches the switch SWI from the A position to the B position, turns off (mutes) the video output, and
After the movement of step 3 is completed, the switch SWI is returned to the A position to output the reproduced video signal.

In this way, if the video signal is turned off during the movement period of the magnetic head 53, the monitor screen will be a pitch black screen without noise during the movement period of the magnetic head 53.
After the switch SWI is returned to position A, it takes time for the monitor to pull in the vertical synchronization, and the phenomenon in which the image flows vertically (image shaking) cannot be resolved.

An example of a configuration of a reproducing apparatus that can simultaneously solve the problem of noise generation and video shaking is shown in FIG.

That is, the playback device shown in FIG. 7 includes a synchronization signal generation circuit 60 in addition to the configuration shown in FIG. By inputting this into the spindle servo circuit 52, the magnetic disk 51 is rotated in phase synchronization with the synchronization signal. As a result, the video signal obtained by passing through the signal processing circuit 55 and the synchronization signal from the synchronization signal generation circuit 60 can be synchronized.
When switching from the position to the b position, the synchronization signal from the synchronization signal generation circuit 60 is output to the reproduction side, and the magnetic head 53 is unable to read the vertical synchronization signal due to tracking. In this case, the vertical synchronization signal can be output from the synchronization signal generation circuit 60 to the reproduction side instead. Therefore, in the reproducing apparatus shown in FIG. 7, since vertical synchronization is maintained on the reproducing side even during tracking, it is possible to prevent image fluctuation after the magnetic head 53 moves.

<Problems to be Solved by the Invention> By the way, in the case of continuously reproducing tracks in which high-speed continuous shooting images of up to 20 frames per sandstone are recorded, the above-mentioned Figs. 6 and 7 are used. It would be very strange if the screen was muted every time tracking was performed, as in the playback device shown in Figure 2. If the tracking speed of the magnetic head is slow and the mute time becomes long,
There were times when high-speed continuous playback of 20 frames per second became impossible.

As a device that can solve this problem, as shown by the dotted line in FIG. In addition, there is a system in which tracking of the magnetic head between adjacent tracks is performed at high speed in a time shorter than one cycle of the vertical synchronization signal.

This method is described in 1. This will be explained in detail with reference to the system diagram in FIG. 7 and the time chart in FIG. 8.

Here, since the spindle servo circuit 52 is controlled in synchronization with the synchronization signal generation circuit 60, the signal processing circuit 55
The reproduced video signal of the A track that has passed through the servo circuit 52 and the synchronization signal from the synchronization signal generation circuit 60 are synchronized within the jitter range of the servo circuit 52, as shown in FIG. When the A track is playing, the adjacent B
When moving the magnetic head 53 to a track, that is, when performing tracking, the system controller 58 monitors the synchronization signal from the synchronization signal generation circuit 6o, and starts the tracking of the magnetic head 53 immediately before the vertical synchronization signal (several meters before). Let it start.

Then, at the start of tracking, the system controller 58 switches the switch SWI from the video output side a to the b side, and outputs the synchronization signal from the synchronization signal generation circuit 6o to the reproduction side. At this time, as the magnetic head 53 moves from the A track to the B track, the reproduced RF signal output decreases as shown in FIG. 8, and then the reproduced RF signal output of the B track increases. Therefore, in FIG. 8, in reality, the A track reproduced video signal gradually disappears at the arrowed part, and conversely, the B track reproduced video signal gradually appears at the arrowed part, and the tracking period The video signal will be clearly reproduced only on both sides of the screen.

Through the above process, tracking is performed with the vertical synchronization part in between, and the unclear parts of the video signal are replaced with the synchronization signal from the synchronization signal generation circuit 60. A reproduced video signal as shown in FIG. 8 is output from the switch SWI. be done. In this case, by making the tracking time sufficiently short compared to one cycle of the vertical synchronization signal, the video signal may be interrupted during tracking, and the monitor screen may become completely black, or the monitor screen may be pushed up and down and become too much. It becomes less noticeable. However, even during tracking, the synchronization signal is output to the playback side without interruption, so there is no screen shake after the track is moved, and high-speed continuous playback with a good screen is possible. .

According to the above configuration, various problems in the above-mentioned playback device can be substantially overcome, but a new drawback arises in that the synchronization signal generation circuit 60 is required.

In a normal still video player, the synchronization signal generation circuit 6
0 may not be much of a problem, but when miniaturizing a still video that has a recording/playback function, the presence of the synchronization signal generation circuit 60 increases the number of parts and becomes a major problem. It ends up.

That is, a synchronization signal generation circuit must be provided only to perform the above-mentioned control during tracking, and the synchronization signal generation circuit requires a high-frequency oscillator, which causes noise in the reproduced image. There is also the problem that it becomes more likely to occur. In other words, providing a synchronization signal generation circuit places a large burden on image quality, cost, and size of the device.

The present invention has been made in view of the above-mentioned problems, and it is possible to eliminate or reduce screen shake and noise during tracking without the need for a synchronization signal generation circuit, and to reproduce images shot continuously at high speed in a good manner at high speed. The purpose of the present invention is to provide a magnetic disk video playback device that can perform the following functions.

<Means for Solving the Problems> Therefore, as shown in FIG. 1, the magnetic disk video reproducing device according to the present invention includes a magnetic head that reads video signals from the magnetic disk, and a magnetic head that moves the magnetic head to an adjacent track. a magnetic head moving means for moving the magnetic head in the radial direction of the magnetic disk in a time shorter than one period of the vertical synchronization signal added to the video signal; and a vertical synchronization signal from the video signal read by the magnetic head. and a synchronization signal separation means for separating the magnetic head, and when there is a request to move the magnetic head to an adjacent track, the movement of the magnetic head by the magnetic head movement means is started in synchronization with the vertical synchronization signal separated by the synchronization signal separation means. and an adjacent track movement start control means.

<Function> According to this configuration, the time required to move the magnetic head to an adjacent track is shorter than one cycle of the vertical synchronizing signal in the video signal, so synchronization is performed with the vertical synchronizing signal obtained separately from the video signal. By starting the movement of the magnetic head by moving the magnetic head, it is possible to avoid the loss of the vertical synchronization signal in the output of the reproduced video while the magnetic head is moving, and the reproduced video of the track after the movement will flow up and down due to the delay in pulling in the vertical synchronization signal. Never.

However, instead of having a separate configuration with a synchronization signal generation circuit, the vertical synchronization signal is separated from the video signal using a separation means that can be realized with a simpler configuration than the synchronization signal generation circuit, and the start of movement of the magnetic head is detected as a video signal. Since it is synchronized with the vertical synchronization signal of the signal, the circuit configuration can be simplified, and since a high frequency oscillation circuit is not required, noise can be reduced.

<Example> The present invention will be explained in detail below.

In FIG. 2 showing one embodiment, the rotation of a magnetic disk 1 is controlled by a spindle servo circuit 2, and the rotation of the magnetic disk 1 is started and stopped by commands from a system controller 3 to the spindle servo circuit 2.

The magnetic head 4 is supported so as to be movable in the radial direction of the magnetic disk 1, and is driven in the moving direction by a stepping motor (not shown) whose drive is controlled via a stepping motor drive circuit 5 serving as a magnetic head moving means. The reproduction track is changed by a command from the system controller 3 to the stepping motor drive circuit 5.

The movement (tracking) of the magnetic head 4 between adjacent tracks of the magnetic disk 4 is such that the time from the start to the end of the movement is shorter than one period of the vertical synchronizing signal.

The video signal (composite video signal) read from the magnetic disk l by the magnetic head 4 is amplified by an amplifier 6, further processed by a signal processing circuit 7, and output as a reproduced video signal to a reproduction device such as a monitor or printer. At the same time, the signal is input to a synchronization separation circuit 8 as a synchronization signal separation means. The synchronization signal separation circuit 8 separates a vertical synchronization signal from the reproduced video signal output from the signal processing circuit 7, and outputs this vertical synchronization signal to the system controller 3, which functions as an adjacent track movement start control means.

Further, a track movement request signal from the track movement key 9 is input to the system controller 3.

In this configuration, the signal waveforms at various parts during the process of moving the magnetic head 4 from the state in which the A track is being reproduced on the magnetic disk l to reproduce the B track adjacent to the A track are shown in the time chart of FIG. The content of control by the system controller 3 that determines the timing of movement of the magnetic head 4 is shown in the flowchart of FIG. 3, and with reference to FIGS. Explain the effect of

That is, at a certain point when the magnetic head 4 is at the position of the A track and the reproduced waveform of the A track is being output, a track movement request command is issued by the track movement key 9 to the system controller 3, as shown in the flowchart of FIG. When the vertical synchronizing signal separated from the reproduced video signal is input, the system controller 3 waits for the input of the vertical synchronizing signal from the synchronizing signal separation circuit 8 after receiving the track movement request command, and then inputs the vertical synchronizing signal separated from the reproduced video signal. The stepping motor for driving the head 4 is started.

When the movement of the magnetic head 4 is started, the reproduced RF signal output starts from the center of the track to the magnetic head 4 as shown in FIG.
As the magnetic head 4 shifts, it gradually begins to attenuate, and the reproduced video signal does not disappear immediately when the magnetic head 4 starts moving, but the S/N ratio gradually deteriorates until it becomes impossible to output the video signal.

At this time, almost no reproduced RF signal output is obtained, and the magnetic head 4 is located near the guard band between the A track and the B track. As the magnetic head 4 approaches the B track from the vicinity of the guard band, the reproduced RF signal output from the B track increases, and the reproduced video signal of the B track also becomes clearly output. When the movement of the magnetic head 4 is completed, it is determined whether the video signal recorded on the B track is to be reproduced.

Through the above process, the movement of the magnetic head 4 starts beyond the vertical synchronization signal of the video signal of the track being reproduced before movement, so the time required for the magnetic head 4 to move between adjacent tracks is By making the signal shorter than one cycle of the vertical synchronization signal, the vertical synchronization signal output to the reproduction side will not be lost while the magnetic head 4 is moving.

Therefore, the synchronization will not be disrupted due to an input error in the vertical synchronization signal on the playback side, and the screen will not flow in the vertical direction. In addition, the noise caused by the interruption of the video signal when the magnetic head 4 passes through the guard band occurs immediately after the vertical synchronization signal that synchronizes the start of movement of the magnetic head 4, so it is present at the top of the screen and is not very noticeable. There will be no.

In addition, the video signal output does not stop over the entire tracking period, but the video output is completely interrupted only when the magnetic head 4 passes through the guard band area, so high-speed continuous playback is possible, and high-speed snapshot recording is possible. When a still image is reproduced by moving the track at high speed based on a jog dial-like input, the reproduced image is extremely good with no vertical play on the screen.

In the example shown in the time chart of FIG. 4, after there is a request to move the magnetic head 4 to an adjacent track, the actual movement is started after waiting for the vertical synchronization signal to be output. As shown in FIG. 4, even if the magnetic head 4 starts moving, the video signal of the track being played does not disappear immediately; the video signal actually disappears after a certain delay time τd has elapsed. It is from.

Therefore, even if the movement of the magnetic head 4 is started before the maximum time .tau.d from the vertical synchronization signal, the vertical synchronization signal will not be output to the reproducing side with a loss. Therefore, for example 1
It is possible to start the movement of the magnetic head 4 before the maximum τd of the vertical synchronization signal by counting the time from the previous vertical synchronization signal, and in this case, the time when the movement of the magnetic head 4 ends may be set earlier than the start of movement. As a result, the vertical synchronization signal included in the movement period is moved closer to the vertical synchronization signal included in the movement period, and as a result, the noise that appears on the playback screen is pushed further to the top of the screen, and the noise becomes less noticeable.

The travel time of the magnetic head 4 may vary depending on the power of the stepping motor and the number of steps of the motor when moving one track, or it can be made sufficiently shorter than one cycle of the vertical synchronization signal by using a high-performance stepping motor. This makes it possible to further reduce the visibility of the noise part.

In addition, in order to detect the rotational phase of the magnetic disk 1, a PG
The detection circuit is essential in a magnetic disk reproducing circuit, and when the magnetic head 4 starts moving a maximum of time τd before the vertical synchronization signal, it starts 7H±2H before the vertical synchronization signal. It is also possible to use a certain PG detection signal as a trigger signal for starting the movement of the magnetic head 4. In this case, the synchronization separation circuit 8 shown in FIG. 2 is not necessary, and it becomes possible to further reduce the cost and size, or if it is not possible to use the PC detection signal as a trigger signal, the synchronous separation circuit 8 shown in the above embodiment can be used. Depending on the configuration, it is possible to reproduce images with a simple configuration and with a low noise level.

<Effects of the Invention> As explained above, according to the present invention, it is possible to avoid shaking of the playback screen during tracking, but this does not require an expensive and complicated synchronization signal generation circuit that requires a high frequency oscillation circuit. Since there is no interruption in the video signal over the entire tracking period, the circuit configuration of the playback device can be simplified, and there is no noise caused by the provision of a high-frequency oscillator. This has the effect of allowing high-speed playback.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing the configuration of the present invention, FIG. 2 is a system block diagram showing an embodiment of the present invention, FIG. FIG. 4 is a time chart showing the state of control and video signals during tracking in the same embodiment as above, FIG. 5 is a diagram for explaining the recording method of video signals on a magnetic disk, and FIGS. 6 and 7 are respectively FIG. 8 is a system block diagram showing a conventional example of a video reproducing device for a magnetic disk. FIG. 8 is a time chart showing the state of control and video signals during tracking in the conventional device. 1... Magnetic disk 2... Spindle servo circuit 3... System controller 4... Magnetic head 5... Stepping motor drive circuit 6...
・Amplifier 7...Signal processing circuit 8...Synchronization separation circuit 9...Track movement key

Claims (1)

[Scope of Claim] A video playback device for a magnetic disk that plays back video signals from each track on which video information is recorded concentrically on a magnetic disk, comprising: a magnetic head that reads video signals from the magnetic disk; a magnetic head moving means for moving the magnetic head in the radial direction of the magnetic disk so that the time it takes to move to an adjacent track is shorter than one cycle of a vertical synchronization signal added to the video signal; a synchronizing signal separating means for separating a vertical synchronizing signal from the output video signal; and a synchronizing signal separating means for separating a vertical synchronizing signal from the outputted video signal; 1. A video reproducing apparatus for a magnetic disk, comprising: adjacent track movement start control means for starting movement of the magnetic head by the magnetic head movement means;