JPS6318212Y2 - - Google Patents

Description

[Detailed Description of the Invention] The present invention relates to a helical scan type magnetic recording and reproducing device (VTR), and has a simple configuration so that good still image reproduction is automatically performed when necessary based on the reproduction state. In addition, in the still image reproduction state, the tape is configured to be able to advance in minute sections, that is, frame advance, when necessary.

As is well known, in a helical scan VTR, if the magnetic tape is played back while stopped, a still image can be played back.

However, since the scanning locus of the rotating head on the magnetic tape when the tape is stopped is different from the recording locus, it is not possible to accurately scan one recording locus, resulting in a period in which no reproduction signal is obtained.

By locating this period in which no reproduced signal is obtained near the vertical synchronizing signal, an image with substantially less damage can be displayed on the television receiver.

The position on the playback screen during this period when no playback signal is obtained varies depending on the positional relationship between the rotation trajectory of the rotary head and the recording trajectory, that is, the stop position of the magnetic tape.
I looked at the playback screen and moved the magnetic tape slightly to get the best image.

The present invention is configured to automatically obtain an optimal image, and examples thereof will be described below with reference to the drawings.

Figure 1 shows a two-head helical scan type
The recording trajectory of the VTR and the trajectory of the video head during still image playback are shown. The head gap angles of the two video heads are slightly different, resulting in azimuth recording. Therefore, tracks a ₁ , a ₂ , a ₃ . . . recorded on the A head side are reproduced only on the A head, and tracks b ₁ , b ₂ , b _{3 .} . . recorded on the B head side are reproduced only on the B head. It is not possible. FIG. 2 shows the envelope of the head output during still image playback, and lines A and B in FIG. 2 correspond to playback trajectories 1 and 2 in FIG. 1, respectively. In the case of trajectory 1, the section where the envelope disappears becomes a head switching point and falls exactly within the vertical blanking section. Trajectory 2
In this case, it will be located within the screen. The envelope output becomes small and the area around O becomes a noise band in the reproduced image. Figure 2C shows the waveform when the head output is passed through a limiter. That waveform
The waveform when AM is detected is 2. In the present invention, the waveform D is detected to determine which track the head is currently playing. That is, the tape is run until the detection output pulse 2 comes near the head switching position.

FIG. 3 shows a basic configuration diagram of the present invention, and FIG. 4 shows waveforms of each part thereof.

When the VTR is in the normal playback mode, a motor control signal is passed from the input terminal 3 through the gate 4 to the motor drive circuit 5 to control and drive the capstan motor 6. When the normal playback/still image playback switching signal (PLAY/STILL) a is switched to the STILL mode, the gate 4 is cut off and the gate 7 is turned on. The output signal d of the gate 7 controls and drives the capstan motor 6 via the motor drive circuit 5. However, at the moment when the switching signal a switches to the STILL side, the differentiating circuit 8 operates, and its output signal C momentarily shuts off the gate 7, and also operates the motor brake circuit 9 to stop the capstan motor. Apply the electromagnetic brake to 6 to stop the tape from running. After that, the output control signal d of gate 7
The capstan 6 is controlled and driven. The head switching pulse (30Hz) g corresponding to the rotational phase of the rotary head is phase-shifted by Δt in MM (mono-multi) 10, and then converted into a thin pulse h in MM11.
becomes. Pulse h is FF (flip-flop) 1
It is used as a set signal for gate 2 and as a gate signal for gate 13. RF signal k of head output
becomes a pulse j corresponding to the section where the envelope output disappears in the detection circuit 14. Pulse j is used to determine what kind of track the head is currently playing. That is, pulse j is gated at gate 13 by gate pulse h. The signal i is output from the gate 13 only when the pulse j matches the phase of the gate pulse h. Signal i operates as a reset signal for FF12. In the FF 12, when there is a set signal h and no reset signal i, a high level signal f appears at the Q terminal. On the other hand, when there is a reset signal i, the Q terminal becomes Low level, and the terminal becomes
High level. The high level is gate 1
5 to the motor brake circuit 9.
The gate 15 is ON-OFF controlled by the switching signal a, and is in a conductive state only in the STILL mode. That is, when the switching signal a switches to the STILL side, the electromagnetic brake is applied momentarily to the capstan motor 6, and the motor stops. Thereafter, the motor is driven by the output of the gate circuit 18, which is controlled using the output signal f of the FF 12 as a gate pulse. The motor control signal input to this gate circuit 18 is created as follows.

The 30Hz head switching pulse g is divided by the 1/2 divider circuit 16 to become a 15Hz pulse, and the MM
17 becomes a motor control signal with a pulse width Z and a frequency of 15 Hz.

That is, after the switching signal a switches to the STILL side, during the period when the level of the signal f is High,
The motor is pulse driven by the signal d via the gate circuits 18 and 7.

The setting of the pulse width Z of the pulse d is determined based on the tape feeding speed and accuracy. Since the tape is driven by pulses in this manner, the tape can be accurately and minutely fed, making it ideal for this type of control.

The tape travels slowly due to the pulse d, the noise band detection signal j approaches the switching point of the head switching pulse, and the pulse h
When the phase coincides with that of the FF 12, the FF 12 enters a reset state, the signal f becomes O, and the control signal to the motor is stopped, and a motor brake signal is generated from the terminal, stopping tape running instantly. Therefore, the position of the noise band is maintained in the vertical blanking interval. From PLAY mode like this
When you switch to STILL mode, the tape always stops where the noise band becomes a vertical blanking interval, so you see a still image without the noise band. Here, the tape is stopped by controlling the electromagnetic brake of the motor, but a reel-based mechanical brake may also be used. At this time, the brake solenoid may be controlled in the same way.

In fact, in order to make the noise band width as narrow as possible, the track width of the head should be made slightly wider than the pitch of the recording pattern.

In this example, the noise band gate signal h is 30
Every Hz, that is, every frame, but 60Hz
It may be for every field, that is, for every field.

The above describes a configuration in which a still image without noise bands is automatically obtained when switching from PLAY mode to STILL mode. However, when playing still images, which is the purpose of this invention,
The structure for changing still images, that is, the frame feeding mechanism will be explained with reference to FIG.

FIG. 5 shows additions to the basic configuration shown in FIG. 3, and the parts indicated by dotted lines in FIG. 5 are added.

Now, in the state where a good still image has been obtained by the above-mentioned operation, the frame-advancing pulse generating means 19 is operated to generate a frame-advancing pulse (FIG. 6A) having a pulse width sufficiently wider than that of the pulse d.

This frame advance pulse is applied to the gate circuit 15, releases the motor brake 9, and is applied to the motor drive circuit 5 via the gate circuit 7, driving the capstan motor 6 for the duration of the pulse width and rotating the tape. Send a small amount.

Due to this movement of the tape, the phase relationship between signals h and j becomes inconsistent, and signal i disappears. When the signal i disappears, the flip-flop 12 operates, and the pulse d is supplied to the capstan motor 6.The automatic feed mode is entered, and the tape is fed until the next optimal still image is obtained, and the process continues as before. Stop automatically.

This state is shown in FIG. FIG. 6B shows the pulse d applied to the capstan motor 6. Furthermore, if the frame feed pulse generating means 19 is configured to continuously generate the output at a fixed period, the frame feed operation is performed at fixed intervals, and a kind of super slow reproduction image can be obtained.

As described above, according to the present invention, a good still image can be automatically obtained when necessary from the normal reproduction state, and frame advance can be performed in the still image reproduction state.

In addition, in this invention, when feeding the tape at low speed to determine the optimal still image position, a pulse-like driving force is applied to the capstan motor to make the tape run intermittently, so the inertia of the capstan at this time is This allows the magnetic tape to be stopped more accurately at the optimum position.Furthermore, the pulse-like driving force (Fig. 4 d) and the pulse for detecting the optimum still image position (Fig. 4 h) can be reduced. Since both are configured to be synchronized with the rotational phase of the rotary head, it is possible to detect whether or not the optimum position is reached at the same time of intermittent tape running, and a stable still image can be obtained.

In addition, when playing a still image, when moving a frame to the next field (frame), a pulse wider than the drive pulse during the intermittent running is applied to the capstan motor, greatly disrupting the optimal still image playback state and causing the next field (frame) to move. By driving the tape all at once to the vicinity of the optimum still image position, and then driving it in small increments using the drive pulses, the tape can be quickly moved to the next optimum still image position without sacrificing stopping accuracy at the optimum still image position. It is something that can be moved.

[Brief explanation of the drawing]

Figure 1 is a diagram showing the tape pattern and still image playback locus in the azimuth recording method, Figure 2 is a diagram showing the envelope waveform and noise band waveform in each playback locus in Figure 1, and Figure 3 is a diagram showing the tape pattern and still image playback trajectory in the azimuth recording method. A block diagram showing an embodiment of the basic configuration of the invention, FIG. 4 is a waveform diagram of the operation of each part of FIG. 3, FIG. 5 is a block diagram showing an embodiment of the invention, and FIG. 6 is an explanatory diagram of the same operation. It is. 4, 7, 13, 15, 18...gate circuit, 5
... Motor drive circuit, 6 ... Capstan motor, 8 ... Differential circuit, 9 ... Motor brake circuit, 12 ... Flip-flop circuit, 14 ... Detection circuit, 16 ... 1/2 frequency division circuit, 17 ... Monostable multi, 19... Piece feed pulse generation means.

Claims (1)

[Scope of utility model registration request] a first pulse generating means for generating a first pulse j corresponding to a period in which the envelope of a reproduced signal from the rotary head falls below a predetermined level; and a head switching pulse corresponding to a head switching point of the rotary head. a second pulse creating means for creating a second pulse h that is phase-synchronized with the first pulse; and a third pulse that creates a third pulse f for a period when the first pulse and the second pulse have a predetermined phase relationship. a fourth pulse generating means for generating a fourth pulse d whose phase is synchronized with the frequency-divided signal of the head switching pulse;
a gate means for applying the fourth pulse d to the capstan motor as a drive signal for a certain period of the third pulse f using the third pulse f as a gate pulse; a braking means for stopping the capstan motor during a period in which there is no pulse f; and a braking means for applying a signal having a pulse width larger than the fourth pulse as a drive signal to the capstan motor during frame feeding; A rotary head type magnetic recording and reproducing device comprising means for generating a frame advance pulse which is applied as a brake release signal to the frame.