JPS62204676A - 8mm video tape recorder - Google Patents

Abstract

PURPOSE:To execute slow motion reproduction or frame feeding reproduction without noise by providing the 1st-3rd delay pulse generating circuits. CONSTITUTION:The 1st delay pulse is generated from the 1st delay pulse generating circuit 15 in response to a trigger signal and given to a sample-and-holding circuit 9. The circuit 9 samples and holds the output of a comparator circuit 7 in the timing of the trailing of the pulse and gives its output to the 2nd delay pulse generating circuit 16, which generates the 2nd delay pulse corresponding to the output of the circuit 9 and gives it to the 3rd delay pulse generating circuit 17. The circuit 17 generates the 3rd delay pulse in response to the 2nd delay pulse excluding the effect of the deviation of the tracking state and gives the result to an FF 18. The FF 18 is set by the trailing of the pulse, then the drive of a capstan motor 12 is stopped to stop a magnetic tape 1.

Description

DETAILED DESCRIPTION OF THE INVENTION Technical Field The present invention relates to an 8 mm video tape recorder that performs tracking control using four types of pilot signals of sequentially different frequencies.

<Prior Art> Conventionally, in VHS or β-type video tape recorders, control signals are recorded on the magnetic tape to control the tracking of the rotating magnetic head. This is done using control signals. That is, the magnetic tape is run to perform running playback, a control signal is detected during this running playback state, and after a predetermined time has elapsed since the detection of this control signal, the running of the magnetic tape is stopped and still playback is performed, and then still playback is performed by stopping the running of the magnetic tape. The magnetic tape is configured to run and stop intermittently based on a control signal, such as running and playing again after a predetermined period of time has elapsed, thereby performing noise-free slow-motion playback or frame-by-frame playback.

However, in an 8 mm video tape recorder, since the tracking control of the rotating magnetic head is performed using four types of pilot signals, no control signals are recorded on the magnetic tape.
Furthermore, it is not possible to perform slow-motion playback or frame-by-frame playback in the same manner as a β-format video tape recorder.

<Object of the Invention> The present invention has been made in view of the above-mentioned points, and is capable of noise-free slow-motion playback or frame-by-frame playback in an 8mm video tape recorder in which control signals are not recorded on magnetic tape. The purpose is to carry out.

<Configuration of the Invention> In order to achieve the above-mentioned object, the present invention provides an 8mm video tape recorder that performs tracking control using a reproduced pilot signal. A base wall signal generation circuit that generates a reference signal, a trigger circuit that forms and outputs a trigger signal for driving a capstan motor in synchronization with the head switching pulse based on the reference signal and the head switching pulse, and this trigger signal. a first delay pulse generation circuit that generates a first delay pulse of a constant pulse width in response to the first delay pulse, and a sampling hold circuit that samples and holds the output of the comparison circuit for drugging control in response to the first delay pulse; a second delay pulse generation circuit that generates a second delay pulse with a pulse width corresponding to the output of the sampling and hold circuit; and a third delay pulse generator with a constant pulse width for stopping the capstan motor in response to the second delay pulse. a third delay pulse generation circuit that generates a delay pulse; and a third delay pulse generation circuit that generates a delay pulse;
An output circuit is provided that outputs a drive signal for intermittently driving the capstan motor based on the delayed pulse.

With the above configuration, driving of the capstan motor is started in synchronization with the head switching pulse, and after a certain period of time, the output of the comparator circuit corresponding to the tracking state is sampled and held using the first delay pulse, and the output that has been sampled and held is handled. A series of operations is repeated in which a second delay pulse with a pulse width of The drive is performed to perform frame-by-frame playback or slow-motion playback.

<Example> Hereinafter, an example of the present invention will be described in detail with reference to the drawings. FIG. 1 is a block diagram of one embodiment of the present invention.

On the magnetic tape 1, four types of pilot signals T, -f, an FM luminance signal, etc. having sequentially specific frequencies are recorded. These pilot signals r, to r4 are recorded superimposed on the FM luminance signal and the like while circulating for each track of the magnetic tape 1. Each of these pilot signals f
, -f2 frequencies are 6.5 L, 7.5 ro, 1
They are respectively set to 0.5 ro and 9.5 fo (fo is the horizontal synchronization frequency), and the difference of one frequency between the pilot signal recorded on the track consisting of the track and the adjacent pilot signals on both sides is f, (16kHz), 3r,
(46 ktl z).

2.3, there are two first... The second rotating magnetic head 4 responds to the head switching pulse by rotating the first rotating magnetic head 4. This is a head amplifier that alternately amplifies and outputs the output of the second rotating magnetic head 2.3.

The 8 mm video tape recorder of this embodiment is a beat signal generator that generates two types of beat signals based on pilot signals f1 to r4 reproduced from a magnetic tape l and four types of reference pilot signals (local pilot signals). means 5; a switching circuit 6 for outputting two types of error signals by alternately switching the two beat signals every l field in response to a head switching pulse; and a comparison circuit 7 for comparing the levels of the two error signals. and an adder circuit 8 that adds the output of the comparator circuit 7 and the speed control voltage.

The beat signal generating means 5 includes a low-pass filter 9', a mixer lO, and band-pass filters 11 and 12 whose band frequencies are r, , 3''. Four types of regenerated pilot signals r1 to f4 and these regenerated pilot signals r, to r4
Four types of reference pilot signals r, to r4 of the same frequency are sequentially given correspondingly. In the mixer lO,
These reproduced and reference pilot signals are mixed to output a signal with a frequency difference between the two signals. Among these difference frequency signals, signals with frequencies f, , 3f are filtered by the bandpass filter 1.
1.12 to 1st. It is output as a second beat signal.

Two types of first . Since the second beat signal has an opposite polarity of phase lead and lag for each field, the polarity is switched for each field by the switching circuit 6 in response to the head switching pulse, and the two types of first beat signals are generated.
．． It is output as a second error signal.

Both error signals from the switching circuit 6 are applied to a comparison circuit 7, where they are detected and their levels are compared. If the levels of both error signals are equal, it means that the rotary magnetic head 2 or 3 is tracing the video track correctly; if they are not equal, it means that it is not tracing the video track correctly. That is, the output of this comparison circuit 7 corresponds to the tracking state. The output of this comparator circuit 7 is applied to an adder circuit 8 and also to a sampling hold circuit 9, which will be described later.

During normal reproduction, the output of the adder circuit 8 is applied to the motor drive circuit II via the changeover switch 10, and the capstan motor 12 is driven to perform tracking control.

Tracking control during such normal playback is the same as conventional. Note that the reproduction signal from the head amplifier 4 is also given to a reproduction circuit (not shown), and is demodulated into a video signal.

1 The present invention is configured as follows in order to enable noise-free frame-by-frame playback or slow-motion playback.

In other words, there is a reference signal generation circuit 13 that generates a reference signal with a predetermined pulse width in response to frame-by-frame playback or slow-motion playback, and a reference signal generation circuit 13 that generates a reference signal with a predetermined pulse width in response to frame-by-frame playback or slow-motion playback, and a reference signal generation circuit 13 that generates a reference signal with a predetermined pulse width in response to frame-by-frame playback or slow motion playback, and a reference signal generation circuit 13 that generates a reference signal with a predetermined pulse width in response to frame-by-frame playback or slow-motion playback, and a reference signal generation circuit 13 that generates a reference signal with a predetermined pulse width in response to frame-by-frame playback or slow motion playback, and a reference signal generation circuit 13 that generates a reference signal with a predetermined pulse width in response to frame-by-frame playback or slow motion playback, and a reference signal generation circuit 13 that generates a reference signal with a predetermined pulse width in response to frame-by-frame playback or slow-motion playback, and a a trigger circuit 14 that forms and outputs a trigger signal for driving the capstan motor 12; and a first delay pulse that generates a first delay pulse having a constant pulse width in response to the trigger signal.
a delayed pulse generation circuit; a sampling hold circuit 9 that samples and holds the output of the comparator circuit 7 in response to the first delayed pulse; and a second delayed pulse having a pulse width corresponding to the output of the sampling hold circuit 9. a third delay pulse generation circuit 17 that generates a third delay pulse of a constant pulse width for stopping the capstan motor 12 in response to the supplementary second delay pulse; A flip-flop 18 is provided as an output circuit that outputs a drive signal for intermittently driving the capstan motor 12 based on the trigger signal and the third delay pulse.

A mode designation signal for designating a mode such as normal playback or slow motion playback is given to the reference signal generation circuit 13 and the changeover switch IO. Changeover switch 1
0 switches the movable contact IOC to the first individual contact 10a side during normal playback based on this mode designation signal, and switches it to the second individual contact 10b side during frame-by-frame playback or slow motion playback. Moving.

In the present invention, the beat signal generating means 5, the switching circuit 6, and the comparison circuit 7 operate in the same manner as in normal playback even during frame-by-frame playback or slow motion playback. The reference pilot signal of the beat signal generating means 5 is also given to the mixer 10' in the same order as in normal reproduction. therefore,
The output of the comparator circuit 7 corresponds to the tracking state of the rotating magnetic head 2.3 as in normal reproduction.

Next, operations in frame-by-frame playback or slow-motion playback will be explained based on the waveform diagram in FIG. FIG. 2(A) is a mode designation signal, FIG. 2(B) is a standard signal output from the 1 & pear signal generation circuit 13, FIG. 2(C) is a head switching pulse, and FIG. 2(D) is a trigger signal,
FIG. 2(E) shows the output of the flip-flop 18;
F) is the first delayed pulse, FIG. 2 (G) is the second delayed pulse, and FIG. 2 (G) is the third delayed pulse.

When the mode designation signal becomes high level and shifts to frame-by-frame playback or slow-motion playback, in response, the movable contact 10C of the changeover switch IO changes to the second individual contact 1.
Switched to the 0b side. At the same time, reference signal generation circuit 1
3, a reference signal shown in FIG. 2(B) having a predetermined pulse width corresponding to frame-by-frame or slow-motion playback is generated and applied to the trigger circuit 14.

The trigger circuit 14 forms the trigger signal shown in FIG. 2(D) synchronized with the head switching pulse based on this reference signal and the head switching pulse, and sends it to the first delayed pulse generation circuit 15 and the flip-flop I8. Output. This trigger signal is generated when the reference signal is high level.
Moreover, it is output when the head switching pulse first rises.

This trigger signal sets the flip-flop 18 in a set state, and a drive signal is applied from the flip-flop 18 to the motor drive circuit 1 via the changeover switch IO, the capstan motor 12 starts rotating, and the magnetic tape l starts running. Start.

The first delayed pulse generation circuit I5 generates a first delayed pulse shown in FIG. 2 (F') in response to the trigger signal and supplies it to the sampling hold circuit 9. The sampling and holding circuit 9 samples and holds the output of the comparator circuit 7 at the falling timing of the first delayed pulse, and supplies the output to the second delayed pulse generating circuit 16.

In this way, by sampling and holding the trigger signal, that is, the output of the comparator circuit 7 at a timing delayed by a certain period of time from the start of running of the magnetic tape l, the tracking state at a specific position is detected.

The second delayed pulse generation circuit 16 generates a second delayed pulse shown in FIG. The rise of this second delayed pulse is
This is the falling timing of the first delayed pulse.

The reason why the second delayed pulse having a pulse width corresponding to the sampling hold output indicating the tracking state is generated in this way is to correct the influence of a shift in the tracking state.

The third delay pulse generation circuit 17 generates a third delay pulse having a constant pulse width as shown in FIG. Give to 18. The flip-flop 18 is reset at the fall of this third delay pulse, thereby stopping the rotation of the capstan motor I2 and stopping the magnetic tape.

In this way, the output of the comparator circuit 7 indicating the tracking state is sampled and held, and the driving of the capstan motor 12 is stopped after a certain period of time with reference to the second delay pulse having a pulse width corresponding to this sampling and hold output.

By repeating this series of operations, noise-free frame-by-frame playback or slow-motion playback becomes possible.

<Effects of the Invention> As described above, according to the present invention, the output of the comparator circuit corresponding to the tracking state is adjusted by the first delay pulse after a certain period of time after the driving of the capstan motor is started in synchronization with the head switching pulse. sample and hold,
A second delay pulse with a pulse width corresponding to this sampled and held output is generated, and the drive of the capstan motor is stopped by a third delay pulse delayed for a certain period of time based on this second delay pulse. , Noise-free frame-by-frame playback or slow-motion playback is possible even in an 8mm video tape recorder in which control signals are not recorded on magnetic tape.

[Brief explanation of drawings]

FIG. 1 is a block diagram of one embodiment of the present invention, and FIG. 2 is a block diagram of an embodiment of the present invention.
3 is a flowchart for explaining the operation of the embodiment shown in the figure. 5... Beat signal generation means, 6... Switching circuit, 7.
...Comparison circuit, 9...Sampling hold circuit, 1
2... Capstan motor, I3... Reference signal generation circuit, 14... Trigger circuit, I5... First delay pulse generation circuit, 16... Second delay pulse generation circuit, 17.
...Third delay pulse generation circuit, 18...Flip-flop.

Claims (1)

[Claims] (1) In an 8mm video tape recorder that sequentially switches four types of pilot signals having different frequencies for each field and records them on a magnetic tape, and performs tracking control using the pilot signals during playback, playback from the magnetic tape. beat signal generating means for generating two types of beat signals based on the reproduced pilot signal and the reference pilot signal;
A switching circuit that outputs two types of error signals by switching alternately for each field, a comparison circuit that compares the levels of both error signals, and a reference signal of a predetermined pulse width in response to frame-by-frame playback or slow-motion playback. a trigger circuit for forming and outputting a trigger signal for driving a capstan motor in synchronization with the head switching pulse based on the reference signal and the head switching pulse; a first delayed pulse generation circuit that generates a first delayed pulse with a constant pulse width; a sampling hold circuit that samples and holds the output of the comparison circuit in response to the first delayed pulse; a second delay pulse generation circuit that generates a second delay pulse with a constant pulse width; and a third delay pulse that generates a third delay pulse with a constant pulse width for stopping the capstan motor in response to the second delay pulse. An 8 mm video tape recorder comprising: a pulse generation circuit; and an output circuit that outputs a drive signal for intermittently driving a capstan motor based on the trigger signal and the third delayed pulse.