JPH0320916Y2 - - Google Patents

Description

[Detailed Description of the Invention] (Technical Field) The present invention involves sequentially switching four types of pilot signals having different frequencies for each field and cyclically recording them on a track of a recording medium, and then recording the pilot signals from the recording medium during playback. Two types of beat signals are generated based on the reproduced pilot signal to be reproduced and the four types of pilot signals that are cyclically and sequentially output from the pilot signal generating means for each field, and based on both beat signals, the capstan is It relates to a magnetic recording and reproducing device that controls tracking by forming a phase-based control signal, and more specifically, when transitioning from a stopped state to a reproducing state in which the recording medium starts running, particularly when capturing an image during continuous shooting. Related to technology to prevent disturbances.

(Prior art) In this type of magnetic recording and reproducing device, the magnetic tape T
Recording is performed on a recording medium such as by two heads 1 having an azimuth angle in an oblique direction.
It is designed to record with a magnetization pattern as shown in the figure. _The recorded signals at this time _, as _shown in _{FIG .} It consists of an FM modulated luminance signal _S2 for recording a video signal on a videotape, and the four pilot signals _f1 , _f2 , _f3 , _f4 are recorded while circulating for each field.
The shaded portion _S3 in the FM modulated luminance signal _S2 corresponds between the tip of the synchronization signal and the white peak.
This is the FM carrier frequency shift part. Further, the pilot signals f ₁ , f ₂ , f ₃ , f ₄ are set to 6.5f, 7.5f, 10.5f, 9.5f (f: horizontal scanning frequency), as shown in FIG. When reproducing the magnetization pattern of the recording medium T, for example, as shown in FIG. 9, the pilot signal f ₁ of the track to be reproduced and the pilot signals f ₂ and f ₄ of the adjacent tracks are output at the same time. By extracting both beat signals, the tracking state of the rotating magnetic head 1 can be detected. For example, head 1
When the track _f1 is being reproduced, the beat signals of the adjacent tracks _f2 and _f4 become f and 3f, respectively, as is clear from FIG. 8 mentioned above. That is, depending on the tracking state of the reproduction head 1, f,
The level of 3f will change.

Therefore, conventionally, a configuration as shown in FIG. 10 has been adopted to detect the tracking state.

That is, it has a beat signal generating means B that generates a beat signal based on the output of the head amplifier A, and in this beat signal generating means B, the beat signal is taken out from the recording medium T via the magnetic head 1 during reproduction, and is also transmitted to the head amplifier A. The signal amplified by is input to low pass filter (LPF) 2,
As a result, only pilot signals _f1 to _f4 are taken out. During reproduction, the beat signal generating means B, which has a pilot signal generating means consisting of a signal generator 3 and a select circuit 4, receives f ₁ from the signal generator 3 by the select circuit 4 in the same way as in the recording state. , f ₂ , f ₃ and f ₄ are selected and extracted in this order, and mixed with the pilot signal by the mixer circuit 5 to efficiently output beat signals f and 3f. The beat signals f and 3f are then passed through the first and second band pass filters (BPF).
6 and 7.

the first and second bandpass filters 6, 7;
The signals from the field are outputted via the switching circuit 8 by being switched for each field by a switching pulse. This is because the states of phase lead and phase lag are reversed for each field in the beat signals f and 3f.

The signals extracted in this way are rectified by the two rectifier circuits 9 and 10 in the output means C, and compared and amplified by the DC amplifier 11 to form and output a capstan phase system control signal. The signal is applied to a phase control circuit (not shown) to control the tracking state.

With the above configuration, if the pilot signal reproduced by the magnetic head 1 and the signal output from the select circuit 4 are different, the levels of both beat signals will naturally increase and become a tracking error signal, causing the phase control The circuit is activated to control the frequencies of the pilot signal and the output signal from the select circuit 4 to match.

However, in the case of the conventional example having such a configuration, as shown in FIG. When a track is being traced, the control signal is 0, and the change in the control signal is maximum for both adjacent tracks. However, even when tracing adjacent tracks, the control signal is 0. Appears as 0. In other words, even though the pilot signal and the output signal from the select circuit 4 are different, the control signals are the same and it cannot be determined whether a predetermined track is being traced or an adjacent track is being traced. It was hot.

This state occurs due to the inertial movement of the recording medium T when it is stopped, and when the operation becomes stable after the start of playback, the magnetic head 1 naturally
moves to a predetermined track side, the above-mentioned phase control circuit works, and a tracking error signal is generated.
Along with this, the normal tracking state will be restored, but it may take a relatively long time until the tracking error signal is generated, so stable operation of the phase control circuit is required at the beginning of playback. In the case of continuous shooting, there was a drawback that synchronization was poor and the image was distorted.

(Purpose of the invention) The present invention was devised in view of the above circumstances, and an object of the invention is to enable quick synchronization during continuous shooting.

(Structure of the invention) In order to achieve the above purpose, the invention has the following features:
A magnetic recording/reproducing device that performs tracking control using four types of pilot signals includes a sample hold circuit that samples and holds the above-mentioned capstan phase system control signal for each field in response to a gate pulse, and a recording medium that starts running. In the playback state, based on the output of the sample and hold circuit and the head switching pulse,
detection means for detecting a first field in which a particular type of pilot signal among the four types is reproduced and providing a corresponding output; and based on the output of the detection means, until the first field is detected. , the pilot signal outputted from the pilot signal generating means is fixed to one type, and after the first field, the pilot signal is outputted cyclically and sequentially from four types of pilot signals from the specific type of pilot signal for each field. and control means for controlling the signal generation means.

(Example) Hereinafter, the present invention will be described in detail based on an example shown in the drawings. FIG. 1 is a circuit diagram showing an embodiment of the magnetic recording/reproducing apparatus of the present invention. Note that the configuration for outputting the capstan phase system control signal from the magnetic head 1 via the head amplifier A, the beat signal generating means B, the switching circuit 8 and the output means C is the same as that described above, and the explanation will be omitted here. , only the effect will be mentioned using the waveform diagrams shown in FIGS. 2 and 3.

Figure 2a shows the first state when the recording medium is stopped.
and waveform diagrams of the outputs f and 3f from the second bandpass filters 6 and 7, respectively, and in both cases, the output from the select circuit 4 is f ₁ ,
The recording medium stop position is f ₁ , f ₂ , f ₃ , f ₄ from top to bottom
The case where each is traced is shown. Figure 2b
shows the pattern in which a pilot signal is recorded on a magnetic tape T as a recording medium and the trace state (between broken lines) of the magnetic head 1 when the magnetic tape T is stopped. In this figure, the frequency f ₃
Indicates that the machine is stopped at the position.

To explain the case where the head stops at _f3 , the head traces from the _f4 side and moves to the _f3 and _f2 sides in order, and an output waveform corresponding to the trace is obtained.

FIG. 3 shows the output after switching the signal output in FIG. Output as a phase system control signal.

In the present invention, when transitioning from the stop state to the playback state, this capstan phase system control signal is used to generate a specific type of pilot signal (in this embodiment,
f ₁ ) detects the first field to be reproduced, thereby making the pilot signal output from the select circuit 4 of the pilot signal generating means coincide with the reproduced pilot signal.

Here, detection based on the capstan phase system control signal will be explained with reference to FIG. 3.

When the stop positions are f ₁ and f ₃ , the switching outputs at the midpoints of each field are both at the same level, so the output of the capstan phase system control signal sampled and held for each field at these midpoints is: It remains almost constant. In addition, when the stop position is f ₂ or f ₄ , the switching output at the midpoint of each field,
The inversion difference in both is large, and the output obtained by sampling and holding the capstan phase control signal for each field at this intermediate point has a constant period waveform. Using these outputs, it is possible to detect whether the stop position is f ₁ or f ₃ or f ₂ or f ₄ .

Next, the main parts of the present invention will be explained in detail.

The magnetic recording/reproducing apparatus of this embodiment has an output means C
A sample-and-hold circuit 12 samples and holds the capstan phase system control signal for each field in response to a gate pulse signal at the midpoint of each field. detection means D for detecting the first field in which a particular type of pilot signal _f1 among the four types is reproduced, based on the output of the circuit 12 and the head switching pulse number D, and providing a corresponding output; Based on the output of the detection means D, the pilot signal output from the select circuit 4 of the pilot signal generation means is fixed at _f1 until the first field is detected, and after the first field, A control means E is provided for controlling the pilot signal generating means so as to cyclically and sequentially output four types of pilot signals for each field from the specific type of pilot signal _f1 .

Detection means D is a waveform shaping circuit composed of a first AND circuit 18 to which a capstan control signal corresponding to the stoppage of the recording medium and a continuous shooting start signal are applied, and a Schmitt circuit to which the output of the sample and hold circuit 12 is applied. 13, a first flip-flop 14 set by the output of the waveform shaping circuit 13, a second AND circuit 19 to which the output of the first flip-flop 14, the head switching pulse number, and the output of the first AND circuit 18 are applied. A second flip-flop 15 is set by the output of the second AND circuit 19.

The control means E includes a third flip-flop 16, which is set by the output of the first AND circuit 18, and a third flip-flop 16, which is set by the output of the first AND circuit 18.
a third AND circuit 20 to which the output of the 1AND circuit 18 and the output of the second flip-flop 15 are applied;
The output of the third AND circuit 20 is applied to the D flip-flop 17, the inverter 21 inverts the continuous shooting start signal C, and the detection means D outputs the continuous shooting start signal or the third
A switching circuit 22 is provided for switching and outputting the output of the flip-flop 16 to the select circuit 4.

The selection circuit 4 of the pilot signal generation means is
During a period when a high-level signal is applied from the control means E, only one type of pilot signal f ₁ is continuously output, and during a period when a low-level signal is applied, four types of pilot signals f ₁ are output. ~f ₄ is switched and output in sequence for each field.

In this embodiment, when starting again from a stopped state, the pilot signal output from the pilot signal generating means is fixed at _f1 , and the pilot is activated as described below based on the capstan phase system control signal. The field in which the signal f ₁ is first reproduced is detected, and from the first field onward, the pilot signal from the pilot signal generating means is reproduced from f ₁ to f _{4 .}
These four types are sequentially switched and output for each field.

Next, the operation of the magnetic recording/reproducing apparatus having the above configuration will be explained based on the time chart of FIG.

This FIG. 4 is a time chart when continuous shooting is started when the stop position is _f3 .

The figure shows the capstan phase control signal from the output means C, the output of the sample and hold circuit 12, the output of the waveform shaping circuit 13, the head switching pulse, and the sample and hold circuit 1.
2, B is the capstan control signal corresponding to stopping the recording medium, C is the continuous shooting start signal, E is the output of the first flip-flop 14, F is the output of the first AND circuit 18, and R is the output of the first AND circuit 18. The output of the second AND circuit 19, .nu. is the output of the second flip-flop 15, .tau. is the output of the D flip-flop 17, .chi. is the output of the third flip-flop 16, and .ru is the regenerated pilot signal.

First, as the recording medium runs and playback starts, the level of the capstan phase control signal from the output means C changes as shown in FIG.
By sample-holding in the sample-hold circuit 12 in response to the gate pulse shown in FIG. 4A,
As shown in FIG. 4, the output becomes high level in the field where the pilot signal f ₄ before the specific type of pilot signal f ₁ is being reproduced, and the waveform is shaped by the waveform shaping circuit 13. will be shown.

The output of the waveform shaping circuit 13 causes the output of the first flip-flop 14 to go high as shown in FIG. 4E. In the second AND circuit 19,
Based on the output of the first flip-flop 14, the head switching pulse, and the output of the first AND circuit 18, the pilot signal _f1 is first reproduced in the reproduction state in which the continuous shooting start signal is given and the recording medium starts running. A signal corresponding to the field is output as shown in FIG.
In the second flip-flop 15, the second AND circuit 1
As shown in FIG. 4, a signal which remains at a high level from the field in which the pilot signal _f1 is first reproduced until recording is started is outputted by the output of 9.

When the output of the second flip-flop 15 of the detection means D is at a low level, the switching circuit 22 of the control means E outputs a continuous shooting start signal on the contact a side to the selection circuit 4, and when the output is at a high level, The output of the third flip-flop 17 shown in FIG.

Therefore, the select circuit 4 of the pilot signal generating means is first given a high level signal H, and is given a low level signal from the field where the pilot signal _f1 is first reproduced. As a result, the select circuit 4 first outputs the pilot signal f ₁ continuously, and after the field where the pilot signal f ₁ was first reproduced, the pilot signals f ₁ to f ₂ , f ₃ , f It will be output cyclically for each field in the order of ₄ . As a result, as shown in FIG. 5, the pilot signal generating means continues to output the pilot signal f ₁ until the rotating magnetic head 1 traces the position of the pilot signal f ₁ .
However, when the signals arrive at the position of the pilot signal _f1 , they can be immediately synchronized and played back.

Although the above-mentioned embodiment describes continuous shooting, the present invention is not limited to continuous shooting, but can be effectively used when transitioning from a stop state to a playback state.

(Effects of the invention) As described above, according to the invention, when transitioning from a stop state to a regeneration state, the first field in which a specific type of pilot signal is regenerated is detected using the capstan phase system control signal, Based on this, the pilot signal output from the pilot signal generating means is made to match the reproduced pilot signal, so both pilot signals can be made to match quickly and well, and in particular, it is possible to prevent image disturbance from continuing during continuous shooting. can be avoided.

[Brief explanation of the drawing]

FIG. 1 is a circuit diagram showing an embodiment of the magnetic recording/reproducing apparatus of the present invention, FIGS. 2a and 3 are waveform diagrams, respectively, FIG. 2b is a diagram showing the positional relationship between the magnetic tape and the head, and FIG. Figure 4 is a time chart, Figure 5 is a time chart for explaining the respective functions, Figure 6 is a diagram showing the magnetization pattern, Figure 7 is a diagram showing the frequency distribution of the pilot signal combined with the FM luminance signal, etc. Fig. 8 shows the specific frequency distribution of the pilot signal, Fig. 9 shows the specific tracing state of the magnetic head, Fig. 10 shows the conventional example, and Fig. 11 shows the amount of tracking deviation. This is a graph showing. 1...Magnetic head, 3...Signal generator, 13...
... Waveform shaping circuit, A... Head amplifier, B... Beat signal generation means, C... Output means.

Claims (1)

[Claims for Utility Model Registration] Four types of pilot signals having different frequencies are sequentially switched for each field and cyclically outputted, combined into an FM luminance signal, etc., and recorded on a track of a recording medium by a rotating magnetic head. and generating two types of beat signals based on the reproduction pilot signal reproduced from the recording medium during reproduction and the four types of pilot signals cyclically and sequentially output for each field from the pilot signal generation means. a switching circuit that selectively switches and outputs the two beat signals in response to a head switching pulse; a switching circuit that rectifies both of the beat signals, and compares and amplifies the rectified outputs to perform capstan phase system control; A magnetic recording/reproducing apparatus comprising: an output means for outputting a signal; a sample hold circuit for sample-holding the capstan phase system control signal from the output means for each field in response to a gate pulse; Detection for detecting the first field in which a specific type of pilot signal among the four types is reproduced based on the output of the sample and hold circuit and the head switching pulse in a playback state in which the signal is started, and providing a corresponding output. and a pilot signal outputted from the pilot signal generating means is fixed to one type until the first field is detected based on the output of the detecting means, and after the first field, the specific type is fixed. 4 per field from different types of pilot signals
A magnetic recording and reproducing apparatus, comprising: control means for controlling the pilot signal generating means so as to output different kinds of pilot signals cyclically and sequentially.