JPS6145672Y2 - - Google Patents

Description

[Detailed description of the invention] The present invention provides that, when an image that is desired to be viewed as a still image appears while projecting a television signal on a monitor receiver, that image is immediately displayed as a still image on the monitor receiver. It is configured so that it can be done.

Traditionally, this type of device extracts one field of television signals through operations when necessary, and records the extracted one-field signal on a circular recording trajectory on a rotationally driven disk-shaped recording medium (rotating disk). An apparatus has been proposed in which the recorded trajectory is repeatedly reproduced immediately after recording to display it on a monitor receiver as a still image.

However, when recording one field (1/60 second) image signal of an interlaced television signal on a rotating disk, if the disk is rotated synchronously with the television's vertical synchronization signal period,
Signals for a field, that is, 262.5 horizontal scanning lines (H) are recorded. Normally, in the NTSC system, interlacing is performed in which two fields form one frame, so there is a time difference of 0.5H between the signals of the odd field image and the even field image.
Therefore, if you continuously play back a disc on which 262.5H worth of signals have been recorded as a circular recording trajectory,
For example, if only odd fields are repeated and there are no even fields, the last horizontal period of one field will be 0.5H as shown in Figure 1, so if the signal that is continuously reproduced is displayed on a TV monitor, it will be 1 A skew equivalent to /2H is generated, and the vertical direction of the reproduced image is distorted by 1/3 to 1/2.

One way to eliminate this problem is to use 263 times the horizontal scanning period of the television signal to be recorded.
The disk is rotated at a frequency of 261 times, 261 times, etc.
It is being considered to eliminate the 0.5H period on the annular recording locus so that a horizontal synchronization signal of continuous phase can be obtained.

However, according to this method, when switching from the television signal received by the monitor receiver to the playback signal (still image) of the disk, the vertical synchronization signals of both signals do not match in phase, so the image is distorted at the time of switching. The problem arises that it becomes disordered.

The present invention aims to solve this problem as well, and one embodiment thereof will be described below with reference to the drawings. Normally, the received video signal a applied to terminal 1 is sent to output terminal 1 via switching circuit 19.
0 and displayed on a monitor receiver (not shown). Further, a part of the received video signal a is
The reference signal generation circuit 8 is synchronously driven by the horizontal synchronization signal applied to the horizontal synchronization signal separation circuit 7 and separated, thereby creating a reference signal synchronized with the horizontal synchronization signal.

This reference signal is frequency-divided by the frequency dividing circuit 9 and then applied to the first phase comparator 11 . The first phase comparator 11 includes a frequency generator 5 that indicates the rotational phase of the motor 4 that rotationally drives the magnetic sheet 3.
The output of is applied. The output of this phase comparator circuit 11 is applied through an adder circuit 12 to a motor 4 to which the magnetic sheet 3 and its rotating shaft are directly connected, so that the rotational state of the magnetic sheet 3 is suppressed. Therefore, when no signal other than the phase comparison output signal from the phase comparison circuit 11 is applied to the adder circuit 12, the magnetic sheet 3 generates an integer multiple (for example, 262 rotates in synchronization with the signal of In this state, when an image that you want to observe as a still image appears, when you switch the changeover switch 6 to the REC side, the video signal a is frequency modulated by the video signal processing circuit 13 having a conventionally known configuration, and the video signal a is frequency-modulated for approximately one field period. (262H period) is extracted and recorded by the magnetic head 2 via the changeover switch 6 on the magnetic sheet 3 as an annular recording locus.

After the recording is completed, the changeover switch 6 is switched to the PLAY side. The reproduced signal from the magnetic head 2 is applied to the reproduced signal processing circuit 15 via the changeover switch 6, demodulated into a video signal, and applied to the switching circuit 19. Also, a part of the reproduced video signal is
The reproduced vertical synchronizing signal c is input to a vertical synchronizing separation circuit 16 to obtain a reproduced vertical synchronizing signal c. This reproduced vertical synchronizing signal c is input to a second phase comparison circuit 17 which compares the phase with that of an input vertical synchronizing signal b separated from the received video signal a by the vertical synchronizing separation circuit 14, and to a coincidence circuit 18 which detects whether the phases of both the vertical synchronizing signals match. The input vertical synchronizing signal b is also input to the second phase comparison circuit 17 and the coincidence circuit 18. When the phases of the reproduced vertical synchronizing signal c and the input vertical synchronizing signal b match, the coincidence circuit 18 outputs a signal as shown in d, which operates a changeover switch 19 to switch the input video signal to the reproduced video signal.
Also, the second phase comparator circuit 17 compares the phases of the input vertical synchronizing signal b and the reproduced vertical synchronizing signal c, and outputs a phase error voltage to the adder circuit 12. This phase error voltage causes the rotation speed of the motor 4 to fluctuate, the phase of the reproduced vertical synchronizing signal c to change, the phase shift with the input vertical synchronizing signal b to decrease, and the phase error voltage applied to the adder circuit 12 to decrease. When the phase difference between the input vertical synchronizing signal and the reproduced vertical synchronizing signal disappears, the phase error voltage from the second phase comparator circuit 17 becomes zero, and the rotation speed of the motor 4 returns to a controlled state. Due to the role of this second phase comparator circuit 17, the time when the phase of the input vertical synchronizing signal b and the phase of the reproduced vertical synchronizing signal c coincide is accelerated, and the input video signal and the reproduced video signal can be switched quickly.

Here, the input vertical synchronization signal b is 262.5H, but the reproduced vertical synchronization signal c is related to the rotation of the motor 4, and is 262H if the motor 4 is controlled to rotate at 262H. Therefore, even if the first phase of the input vertical synchronization signal b and the first phase of the reproduced vertical synchronization signal c match, the phase of the second input vertical synchronization signal
A deviation of 0.5H will appear. Therefore, the second phase comparator circuit 17 and the matching circuit 18 are designed so that once the input vertical synchronizing signal and the reproduced vertical synchronizing signal match in phase, the matching circuit does not detect and compare the phase of the next vertical synchronizing signal. By the output of 18, the stop circuit 2
0 is activated, and the comparison circuit 17 uses the output of the stop circuit 20 to stop the operation of the matching circuit 18.

As described above, according to the present invention, a received video signal can be displayed on a monitor receiver and quickly displayed as a still image when necessary.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing the structure of a television signal recorded on a magnetic sheet, FIG. 2 is a block diagram showing an embodiment of the present invention, and FIG. 3 is an explanatory diagram of the same operation. 2...Magnetic head, 3...Magnetic sheet, 4...
Motor, 7...Horizontal synchronous separation circuit, 14, 16...
...Vertical synchronization separation circuit, 8...Reference signal generation circuit,
9... Frequency divider circuit, 11, 17... Phase comparator, 1
2... Adder, 18... Match circuit, 19... Switching circuit, 20... Stop circuit.

Claims (1)

[Scope of utility model registration request] A first control means that rotationally drives the recording medium at a cycle that is an integral multiple of the cycle of the horizontal synchronization signal of the received video signal, and an operation switch that controls approximately 1 of the horizontal synchronization signal of the received video signal.
A recording/reproducing means for recording a field signal as a circular recording locus on the recording medium and repeatedly reproducing the same; and a switching means for selectively guiding the reproduced video signal from the recording/reproducing means and the received video signal to an output terminal. During playback, a phase difference between a vertical synchronization signal in the reproduced video signal and a vertical synchronization signal in the received video signal is detected, and the first
When the phase of the vertical synchronization signal coincides with the second control means for controlling the control means to change the rotational speed of the recording medium, the second control means thereafter stops the control of the second control means, and A video signal recording and reproducing device comprising means for driving a switching means to guide a reproduced video signal to the output terminal in place of the received video signal.