JPS63229650A - Magnetic picture recording and reproducing device - Google Patents

Abstract

PURPOSE:To raise the reproducing state more quickly by discriminating the change of a tracking error signal accompanied with each head scanning and switching the classification of a pilot signal for tracking control by the extent corresponding to +2 heads. CONSTITUTION:A means 4 which detects and stores the tracking error at the time of stopping a tape, a microcomputer 5 which discriminates whether the change of the tracking error signal accompanied with each head scanning is changed from the lagging state or not, and a switching means 6 which switches the pilot signal in accordance with the discrimination result are provided. The microcomputer 5 checks whether the tracking error signal at the time of stopping running the tape is changed from the lagging state to the leading state by the head operation or not, and the classification of the pilot signal is circularly shifted by +2 if it is changed. Thus, the track deviation of two tracks is changed to that of zero track, namely, the state equivalent to the on-track state, and tracking is quickly led in at the time of running the tape.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a rotary head type VTR 1, particularly a VTR in which a tracking error signal for tape feeding is obtained from a reproduction signal from a video head.

Conventional technology VTRs with the ``8 mm video'' standard record a 4-frequency pilot signal for tracking control along with the video signal as a tracking control method, and during playback, the track to be played receives signals from both adjacent tracks. The level difference between the crosstalk components of the pilot signals is used as a tracking error signal. A method of detecting a tracking error signal using a pilot signal will be explained below.

In FIG. 8, AI, B1. A2. B2... are each recording track recorded by the A head and the B head.

Arrow (a) indicates the scanning direction of the rotary head. In each recording track, each pilot signal indicated by f1 to f4 is sequentially recorded for each field together with the video signal. The recording order of pilot signals is f1, f2 . f3. f4
, and fl is recorded next to f4. Also,
Within each field period, the type of pilot signal is fixed and recorded. The frequency of the pilot signal is set to the values shown in Table 1, for example. Note that in Table 1, f+
+ indicates the frequency of the horizontal synchronization signal in the video signal, and 6
．． 5fo indicates a frequency that is 6.5 times the frequency of the horizontal synchronization signal.

Table 1 The frequency difference between the pilot signals between each recording track is fH or 3fo, as shown in FIG. When the head scans Ai (i=1.2...) tracks, the frequency difference between the pilot signal of the scanning track and the pilot signal recorded on the adjacent track on the right side on the paper is always fH, and It's always 3fo
It is. When the head scans a Bi (i=1.2...) track, the relationship is opposite to that described above, and the frequency difference between the pilot signals with the adjacent track on the right is always 3fo, and that on the left is always fH. .

Since the pilot signal is a relatively low frequency signal around 100 kHz, the pilot signal recorded on the adjacent track can be reproduced as a crosstalk signal even if the head does not scan the adjacent track. for example,
The pilot signal obtained when the head on-tracks the A2 track and performs reproduction scanning is f3. f2. It is a composite signal of fl, and its level is the thickest at f3 (, then f2
, f4 are played back by the same level. When the head slightly deviates from track A2 toward track 82 and performs reproduction scanning, the level of the pilot signal obtained is f3. f4.
It becomes smaller in the order of f2. Conversely, if the head shifts to the track 82 side and scans, the obtained pilot signal will be f.
3. f2. It becomes smaller in the order of f4. Therefore, by separating and extracting the difference signals fH and 3fH between the pilot signal on the main scanning track and each pilot signal recorded on both adjacent tracks, and comparing the reproduction levels of both signals, The amount and direction of head displacement can be known.

FIG. 9 is a block diagram of a reproducing circuit for obtaining a tracking error signal. In FIG. 9, a reproduced signal in which a video signal and a pilot signal are combined is inputted from a terminal 101. The circuit 102 is a low-pass filter and extracts only the pilot signal from the combined reproduced signal.

The pilot signal obtained at this time is a composite signal of the main scanning track and the pilot signals recorded on both adjacent tracks. Circuit 103 is a balanced modulator that multiplies the aforementioned composite pilot signal by the reference signal supplied from terminal 104. The reference signal provided at terminal 104 provides a signal at the same frequency as the pilot signal recorded on the main scan track. For example, in FIG. 8, when the head performs reproduction scanning on track A2, the input signal to balanced modulator 103 is f2. f3. At each signal of f4.

The signal input from terminal 104 is f3. Therefore, the output signal of the balanced modulator 103 is f2°f3. Signals having the sum and difference frequencies of each signal of f4 and the signal of f3 are output. The circuit 105 is a tuned amplifier tuned to the fH signal, and the circuit 107 is a tuned amplifier tuned to the 3fH signal. Circuits 106 and 108 are amplitude detectors and circuit 109 is a level comparator. Therefore, each pilot signal taken out as a crosstalk signal from both adjacent tracks is taken out as a difference signal with the pilot signal recorded on the main scanning track, and then the level comparator 109 determines the level. A signal corresponding to the difference is taken out to terminal 110.

The signal obtained at the terminal 110 has a playback level of fo of 3f.
When the level is higher than the H reproduction level, a (+) potential corresponding to the level difference is extracted, and in the opposite case, a (-) potential is extracted. Since the signal taken out to the terminal 110 includes information on the amount and direction of track deviation of the head, it can be used as a tracking error signal. However, a tracking error signal that is actually suitable for practical use requires further processing. This is because, as is clear from Figure 8,
This is because the relationship between the direction of head displacement and the multiplication output (fo or 3fH) obtained at that time is opposite to that of the Ai track and the Bi track. For this reason,
Using analog inverter 111 and switch 112,
The signal at the terminal 110 may be inverted in an analog manner when the head scans the Ai track and when the head scans the Bi) rack. That is, it is connected to the terminal 110 through the switch 112 when scanning the Ai track, and connected to the output of the analog inverter 111 when scanning the Bi track. This can be handled by switching the pilot signal name depending on whether it is an odd number or an even number. As a result, the output signal of the terminal 114 is always (+) when the head deviates to the right from the track to be scanned, and always (-) when the head deviates to the left, regardless of the Ai or Bi track. The potential of Therefore, by controlling the capstan motor using the signal obtained at the terminal 114, the head can always be scanned on-track on the main scanning track.

The above is an outline of the method for obtaining a tracking error signal using pilot signals of four frequencies.

FIG. 4 is a timing waveform diagram showing a method of intermittent slow motion playback in 8 mm video. Also the fifth
The figure shows the same operation on a tape recording pattern. First, assume that the tape is stopped. This state is A1. Continue until head scanning of Bl. At this time, since the track to be scanned does not change, the pilot signal of the track remains, for example, fl. In FIG. 5, the head scans from the lower right to the upper left. The tracking error signal at this time has a sawtooth waveform that repeatedly changes from a state in which the head is ahead by 0.5 track pitch to a state in which it is behind by 0.5 track pitch for each head scan. The tracking error at the center of the track is in an on-track state. The output of the head at this time is maximum at the center of the scan, and decreases slightly at the beginning and end of the scan.

However, if the width of the head is set wider than the track pitch, it is possible to prevent the output from decreasing, so there is no problem in practice.

Next, tape feeding is started in the A2 head scan.

That is, the motor is started near the center of the A2 scan.

The target speed of the motor is the same speed as the speed at the time of recording. That is, from the middle of scan A2, the tape feeding speed becomes 1x speed. In FIG. 3, the head scans from the lower right to the center in the same way as when stopped, and from the center it scans parallel to the track.

The tracking error signal at this time becomes flat from the middle of scan A2. Moreover, since the signal is sent at 1x speed from the on-track state, the tracking error signal is almost equal to the on-track value. Therefore, the output of the head can be maintained at the maximum output state after starting the motor.

Next, in scanning 82, if the tape feeding speed is 1× speed, the head scans the adjacent track, so the pilot signal used is f2.

In FIG. 5, scanning is performed parallel to the track.

The tracking error signal obtained at this time is flat as in the previous scan. The head output remains at maximum output.

Next, in head scan A3, since the tape has advanced one more track, f3 is used as the pilot signal. Now, in scanning A3, tape feeding is stopped approximately at the center of scanning. In other words, the brakes are applied approximately at the center of the scan.

This allows the motor to stop suddenly.

In FIG. 5, the head scans from the bottom center of the track parallel to the track to the center of the track, and from there it scans toward the top left. The tracking error signal changes from its flat state to a sawtooth waveform as in the scanning of At and B2. That is, the tracking error signal starts to lag from the center of A3, and at the end of scanning, there is a lag of 0.5 track pitch.

The next scan after 83 is in a stopped state, the pilot signal used is f3, and the tracking error signal is A1,
Like Bl, it has a sawtooth waveform, and the output of the head is maximum at the center of the scan, and slightly decreases at the beginning and end of the scan. In FIG. 5, the head corresponds to scanning from the lower right to the upper left. Note that since 8 mm video is recorded in an azimuth manner, it is necessary to select a playback head according to the azimuth of the track to be scanned, but this is well known and will not be described here.

Now, when actually playing back a tape, it does not always stop at the same place due to variations in the starting characteristics of the motor and variations in the mechanical accuracy of the device. For this reason, it is necessary to apply tracking control. That is, in scan B2, the tracking error signal is checked, and if the tape is in an advanced state, the brake is started earlier, and if it is delayed, the brake is started later. For example, if the tracking error signal is delayed by 0.1 track pitch, the brake start timing may be delayed by 0.1 head scanning period.

This allows the tape to always be stopped at the same position.

Problems to be Solved by the Invention Now, in the intermittent feed slow motion playback described in the conventional example, it is assumed that the tape and head positions are on-track at the start of intermittent playback. If you think about the first time you wrapped it,
The vehicle is not necessarily on track. Also,
Even if there is an unrecorded part in the middle of the tape, the on-track state is not guaranteed.

FIG. 10 is a diagram showing the relationship between tracking error and tracking error signal. In other words, when the track is within ±1 track, a normal tracking error signal is obtained, but if the track is off by more than that, the change in the tracking error signal is reversed, and when the track is off by ±2 tracks, the on-track error signal is obtained. will be the same value. However, since the polarity of the change in the tracking error signal is reversed, tracking control is not applied in this state. Even during the aforementioned slow-motion playback, control is first applied in the direction in which tracking deviates. Therefore, if there is a deviation of ±2 tracks, it will take time to get on-track.

Means for Solving the Problems In order to solve the conventional problems, the present invention provides a storage means for detecting and storing the tracking error when the tape is stopped, and a storage means for detecting and storing the tracking error when the tape is stopped, and a method for changing the tracking error signal due to each head scan from a delayed state. A determining means for determining whether the pilot signal has changed is provided, and a switching means for switching the pilot signal based on the result of the determination.

The operating microcomputer checks whether the tracking error signal at the time of tape running stop changes from a delayed state to an advanced state with respect to head operation. If the result of the investigation shows such a change, the type of pilot signal for tracking error signal detection is cyclically shifted by +2.

As a result, the 2-track deviation changes to a 0-track deviation, that is, a state equivalent to an on-track state, and tracking pull-in during tape running can be performed quickly.

Embodiments Prior to describing embodiments, the principle of the present invention will be explained first. FIG. 7 is a waveform diagram showing a head operation switching signal and a tracking error signal when the tape is stopped running. In the on-track state, as shown in the tracking error signal waveform (a), the tracking error signal changes from a lead state to a lag state with respect to the head operation. However, if there is a two-track deviation, the detection characteristics of the tracking error signal detection circuit will be reversed, so the tracking error signal waveform (b)
As shown in the figure, the head operation changes from a delayed state to an advanced state. Therefore, by checking the polarity of the change in the tracking error signal, it is possible to know whether the vehicle is on-track or deviated by two tracks.

FIG. 6 is a circuit block diagram showing the overall configuration of an embodiment of the present invention. That is, a reproduction signal obtained from the magnetic head 1 is sent to a video signal reproduction circuit 3 and a tracking error signal detection circuit 4 via an amplifier 2. The video signal reproducing circuit 3 processes the reproduced signal and outputs it as a video signal. On the other hand, the tracking error signal detection circuit 4 is a circuit for obtaining a tracking error signal from a reproduced signal, and its principle is as already explained. The tracking error signal obtained from the tracking error signal 4 is sent to the microcomputer 5. The microcomputer 5 reads the tracking error signal and the head scan switching signal and outputs various control commands for slow motion reproduction.

The commands include a reference pilot signal selection signal to the tracking error signal detection circuit 4, and a speed command/brake command to the speed control circuit 6 of the capstan motor 8. The speed control circuit 6 of the capstan motor 8 inputs the rotation detection signal obtained from the rotation detector 9 of the capstan, and sends a drive command to the motor drive circuit 7 to control the rotation speed of the capstan motor 8 at a constant level. is sent to the capstan motor 8 via.

1 and 2 are flowcharts showing the processing contents of the microcomputer 5 in FIG. 6, FIG. 1 is a schematic flowchart, and FIG. 2 is a flowchart showing the direction of change in the tracking error signal when tape running is stopped. FIG.

FIG. 1 is a flowchart showing an outline of the processing of the microcomputer 5. As shown in FIG. This process is assumed to be performed at regular intervals. For example, this process may be performed for each timer interrupt using a timer interrupt. First, in process 21, the number of timer interrupts is checked.

Then, depending on the check result, processes 22, 23, 24
．． It branches to 25. First, if the capstan motor is being accelerated, the process branches to process 22, and if the capstan motor is being fed at a constant speed, the process branches to process 23. If the brake is in operation, the process branches to process 24, and if the brake is stopped, the process branches to process 25. If it is accelerating, process 2
2, an acceleration command is output to the capstan motor. Then, the process ends and the process waits until the next timer interrupt. If constant speed feeding is in progress, the process proceeds to step 23 and outputs a command to rotate the capstan motor at a constant speed of 1x speed. The process then proceeds to step 26, where it is checked whether it is the timing to calculate the brake start timing. If it is not the timing to calculate, the process ends and the process waits until the next timer interrupt. If it is the timing to calculate, the process advances to step 27 and calculates the brake start timing from the tracking error signal. This calculation method will be explained in FIG. When processing 27 is completed, the process waits until the next timer interrupt. If the timing is such that the brake is being operated, a brake command for the capstan motor is output in step 24, and the process waits until the next timer interrupt. If the capstan motor is stopped, the process proceeds to step 25, where a command to stop the capstan motor is output, and the process proceeds to step 28, where the direction of change in the tracking error signal is checked and a process for two-track deviation is performed.

The method of processing is explained in FIG. When this process is finished, the process waits until the next timer interrupt. The above is the content of the processing shown in FIG.

FIG. 2 is a flowchart of a portion of the process shown in step 28 of FIG. 1, in which it is checked whether the track has stopped with a deviation of two tracks, and if the deviation is found, the deviation is equivalently canceled. In Fig. 3, processing for a two-track deviation is performed by examining the magnitude relationship of the tracking error signals (denoted as E1 and E2, respectively) when 1/3 cycle and 2/3 cycle have passed since the head operation. This is what we do. In the 1s2 diagram, first in process 40,
Check whether the current time is the time when 1/3 cycle has elapsed since the start of head operation. If the time has elapsed by 1/3 cycle, the process proceeds to process 45; otherwise, the process proceeds to process 41.

In process 45, the tracking error signal value at that time is written into the memory E1. After completing the process shown in FIG. 2, the system enters a waiting state for the next timer interrupt. On the other hand, in process 41, it is checked whether the current time is the time when 2/3 cycles have elapsed since the start of the head operation. If it is the time when 2/3 cycles have elapsed, the process proceeds to step 42; otherwise, the process shown in FIG. 2 is ended and the process waits for the next timer interrupt. Processing 42
Then, the tracking error signal value is written into the memory E2, and the process proceeds to process 43. In process 43, the values in the two memories E1 and E2 are compared in magnitude. As a result of comparison, E 1 >
If it is not E2, the process in FIG. 2 is completed and the state waits for the next timer interrupt. If E 1 > E2, process 4 is executed.
Proceed to step 4. In processing 44, the pilot signal currently used to obtain the tracking error signal is cyclically +
Do 2. For example 1. If f1, change to f3; if f2, change to f4; if f3, change to fl; if f4, change to f2. After this process 44 is completed, the process shown in FIG. 2 is completed and the process enters a waiting state for the next timer interrupt.

Now, in this embodiment, intermittent tape feeding slow motion playback has been explained, but when performing normal playback, after determining the pilot signal at the time of stop by performing the processing shown in Fig. 1, After accelerating the motor as shown in process 22, constant speed control of the motor as shown in process 23 may be performed continuously.

In the explanation of this embodiment, a tracking error signal at 1/3 period and a tracking error signal at 2/3 period from the start of head operation are used, but tracking error signals at other timings may be used. Needless to say, it's good.

As described in detail, the present invention is capable of immediately bringing the tracking control into the retracted state even when the head is not on track, such as when the tape is first wound around the rotating head. This provides a faster startup of the playback state and a better slow-motion playback method.

In this embodiment, a microcomputer was used to detect fluctuations in detection sensitivity of the tracking error signal, output an intermittent feed command for the capstan motor, and output a reference pilot signal switching command. As shown in Japanese Unexamined Patent Publication No. 178762/1984, there is a method of controlling the speed of the capstan motor and tracking control using a tracking error signal using an arithmetic circuit, and in reality, it is realized by the same microcomputer. Since no new arithmetic circuit is required, the effects of the present invention are great.

[Brief explanation of the drawing]

1 and 2 are flowcharts showing the process flow of the microcomputer in FIG. A timing waveform diagram showing a method of intermittent slow-motion playback in a video, FIG. 5 is a diagram of the same pattern, FIG. 6 is a circuit block diagram showing the configuration of an embodiment of the present invention, and FIG. Waveform diagrams of the tracking error signal in the on-track state and the state in which the track is off by two tracks; FIG. 8 is an explanatory diagram showing the recording pattern of the pilot signal in 8 mm video;
FIG. 9 is a block diagram showing the configuration of a tracking error signal detection circuit, and FIG. 10 is a diagram showing the relationship between track deviation and tracking error signal. DESCRIPTION OF SYMBOLS 1... Magnetic head, 4... Tracking error signal detection circuit, 5... Microcomputer, 6... Capstan motor speed control circuit. Name of agent Patent attorney Toshio Nakao and 1 other person Figure 2 Figure 3 Figure 5 Figure 6, 3 Foil 7 Figure Delay r Normal r J Moai) (?Truck Sumaki Tiro 11th → Figure 8 Figure 9

Claims (1)

[Claims] A rotating head generates tracking control pilot signals (f1, f2, f3, and f4) of four different frequencies as discontinuous magnetization trajectories on the magnetic tape for each discontinuous trajectory.
1→f2→f3→f4→f1→... are recorded and reproduced together with the video signal, and during reproduction, the level of the crosstalk pilot signal from both adjacent tracks to the track to be reproduced is changed. In a magnetic recording/reproducing device that obtains a tracking error based on the difference and realizes playback, a storage means detects and stores a tracking error signal when the magnetic tape stops running, and a storage means that detects and stores a tracking error signal when the magnetic tape stops running, and detects and stores the tracking error signal that accompanies each head scan. Judgment means for judging whether the change in the tracking error signal changes from a delayed state to an advanced state, and cyclically switches the type of the pilot signal for tracking control by an amount equivalent to +2 head scans based on the result of the judgment means. What is claimed is: 1. A magnetic recording and reproducing device comprising: switching means.