JPH04114343A - Magnetic tape reproducing device - Google Patents

Abstract

PURPOSE:To execute stable tracking control by deciding a detected synchronizing signal normal only when the synchronizing signal is detected after the lapse of fixed time detecting a pilot signal (PL), and executing the tracking control according to the normal synchronizing signal. CONSTITUTION:When detecting a normal synchronizing signal 100, a magnetic head (MH) detects a PL 102 behind 4 blocks passing a recording position (B) of the signal 100 and further when detecting a normal synchronizing signal 101, a PL 103 is detected before 2 blocks for the MH to pass a recording position (A) of the signal 101. Therefore, it is discriminated based on MH switching signal information whether the reproducing pattern of the MH is an incoming side pattern or an outgoing side pattern, in the case of the incoming side pattern, the detected synchronizing signal is decided as error only when the PL is not detected even after the lapse of fixed time detecting the synchronizing signal. Then, a reference signal selecting command is outputted and according to the reference signal of tracking error, tracking control is executed. Thus, even when the quality of a recorded signal on a magnetic tape is adverse, stable tracking control is executed.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a magnetic tape playback device, and particularly to a magnetic tape playback device such as a digital audio tape recorder (referred to as DAT) or a video tape recorder (referred to as VTR). The present invention relates to a magnetic tape reproducing device suitable for use as a device for reproducing recorded information.

BACKGROUND OF THE INVENTION Information is recorded on diagonal tracks on magnetic tapes used in conventional VTRs and DATs. When reproducing such information, tracking control is adopted as a control in which the reproducing head traces the track along a desired trajectory. When performing tracking control, the DAT uses an ATF signal (Automa) to perform tracking on diagonal tracks formed on the magnetic tape.
tic Track Finding) are recorded at two locations apart from each other. Conventionally, in order to detect a synchronization signal in an ATF signal from a signal reproduced by a magnetic head, the synchronization signal is converted into a digital signal by a comparator, and the period or duty ratio of the signal is determined by the rise or fall of the signal. A configuration is adopted in which the synchronization signal is detected by measuring using a counter circuit that starts or ends counting at a falling edge and comparing the measurement result with predetermined setting conditions.

Problems to be Solved by the Invention However, in conventional methods, even if the S/N of the signal recorded on the magnetic tape deteriorates due to factors such as overwriting and the synchronization signal detection circuit malfunctions, this malfunction cannot be detected. I couldn't. Therefore, the synchronization signal detection circuit operates at a position where a signal other than the synchronization signal is recorded, and the tracking detection circuit, which originally outputs a signal according to the tracking state, outputs a signal different from the tracking state.
Tracking may be temporarily disrupted due to erroneous detection of the synchronization signal.

SUMMARY OF THE INVENTION An object of the present invention is to provide a magnetic tape reproducing apparatus that can detect accurate synchronization signals and perform stable tracking control even when the quality of signals written on the magnetic tape is poor.

Means for Solving the Problems In order to achieve the above object, the present invention provides a magnetic tape running system that makes contact with a magnetic tape attached to a pair of reels and runs the magnetic tape from one reel to the other by rotation. a magnetic head for reproducing information on the magnetic tape; a rotating cylinder that rotates with the magnetic head and moves the magnetic head along designated tracks on the magnetic tape; synchronous signal detection means for detecting a synchronous signal recorded on the magnetic tape from the output signal of the signal conversion means; and pilot signal extraction means for extracting a pilot signal from the signal reproduced by the magnetic head. , an amplitude detecting means for detecting the amplitude of the pilot signal extracted by the pilot signal extracting means; a tracking error detecting means for detecting a tracking error by receiving a sample and hold signal and sample-holding the detection output of the amplitude detecting means; a rotation speed detection means for detecting the rotation speed of the tape running means; a deviation signal generation means for outputting a rotation speed deviation signal for suppressing the deviation between the detection output of the rotation speed detection means and a reference rotation speed to zero; A pilot signal detection means detects the pilot signal recorded on the tape from the output signal of the signal conversion means, and a reproduction pattern of the magnetic head is set after the synchronization signal based on the phase information of the magnetic head switching signal.
a discriminating means for discriminating whether it is an incoming pattern where a pilot signal exists or an outgoing pattern where a pilot signal is present before a synchronization signal, and a determination result indicating when the outgoing pattern is being played back by the determining means is obtained; A determination signal is output only for a certain period of time on the condition that a pilot signal is detected by the pilot signal detection means, and a determination signal is constantly output when the determination means obtains a determination result indicating that the input side pattern is being reproduced. A signal generating means, a sample and hold signal generating means for outputting a sample and hold signal to the tracking error detecting means only when a detection signal is output from the synchronizing signal detecting signal means during a determination signal generation period, and a pilot signal detecting means. A synchronization system that monitors the outputs of the synchronization signal detection means and discrimination means and outputs a reference signal selection command only when a pilot signal is not detected even after a certain period of time has elapsed after a synchronization signal was detected during playback of the input side pattern. signal erroneous detection determination means; selection means for selecting a reference signal for a tracking error when a reference signal selection command is generated; and selecting and outputting an output signal of the tracking error detection means at other times; A magnetic tape reproducing device comprising a rotation control command signal generation means for outputting a rotation control command signal from a rotational speed deviation signal and a rotation control command signal, and a rotation drive means for rotationally driving a magnetic tape running means in accordance with the rotation control command signal. It is.

Function: As shown in FIG.
, pilot signals 102 and 103 are recorded. The synchronization signal 100 and the pilot signal 102 are on the input side A.
The TF pattern is recorded on the side where the magnetic head traces the track first, and the synchronization signal 101 and pilot signal 103 are recorded as the output side ATF pattern on the side where the magnetic head traces the track last. ing.

In the ATF pattern on the output side, two blocks before the position (A) where the magnetic head reproduces the synchronization signal 101,
There is a pilot signal 103 recorded on the main track.

On the other hand, in the ATF pattern on the input side, the pilot signal 10 recorded on the main track is recorded 4 blocks after the position (B) where the magnetic head reproduces the synchronization signal 100.
2 now exist. Therefore, when the synchronization signal 100 is detected normally, the pilot signal 102 will be detected after the fourth block when the magnetic head passes the position (B) where the synchronization signal 100 is recorded.

Further, when a normal synchronization signal 101 is detected, a pilot signal 103 is detected two blocks before the magnetic head passes the position (A) where the synchronization signal 101 is recorded.

Therefore, in the present invention, it is determined whether the reproduction pattern of the magnetic head is an input side pattern or an output side pattern based on the phase information of the magnetic head switching signal, and when a determination result indicating that the input side pattern is being reproduced is obtained, A reference signal selection command is output only when a pilot signal is not detected even after a certain period of time has passed after a synchronization signal is detected, and when this reference signal selection command is generated, tracking control is performed according to the tracking error reference signal. There is. Therefore, even if a synchronization signal is detected, if a pilot signal is not detected after a certain period of time, the detection of the synchronization signal can be determined as a false detection, and tracking control can be performed according to the tracking error reference signal. Even if the quality of the signal recorded on the tape is poor, stable tracking control can be performed.

On the other hand, when a determination result indicating that it is time to reproduce the output pattern is obtained, a determination signal is output for a certain period of time on the condition that a pilot signal is detected by the pilot signal detection means, and synchronization is performed during the generation period of this determination signal. Tracking control is performed by outputting a sample hold signal to the tracking error detection means only when a detection signal is output from the signal detection means. Therefore, if a synchronization signal is detected even though no pilot signal is detected, by disabling the detection of this synchronization signal,
Erroneous detection of synchronization signals can be prevented, and stable tracking can be performed even if the quality of the signals recorded on the magnetic tape is poor.

Example Hereinafter, one embodiment of the present invention will be described based on the drawings.

FIG. 1 shows the configuration of an embodiment of the present invention. In FIG. 1, the magnetic tape 1 is mounted on a pair of reels 6.7, and the running path of the magnetic tape 1 is set between the posts 4 and
, a rotating cylinder 3, and a capstan shaft 8. A head 2A having a positive azimuth and a head 2B having a negative azimuth are fixed to the rotating cylinder 3, and the rotation of the rotating cylinder 3 causes each magnetic head 2A, 2B to travel along a prescribed track on the magnetic tape 1. It is supposed to be done. Each magnetic head 2A, 2B
reproduces various information recorded on the magnetic tape 1, and outputs the reproduced signals to a low-pass filter 16 and a comparator 23. Comparator 23 is for each spatula)
It is configured as a signal conversion means for converting the signals reproduced by '2A and 2B into digital signals, and the output of the comparator 23 is input to the pilot signal detection circuit 24 and the synchronization signal detection circuit 22. The synchronization signal detection circuit 22 is configured as a synchronization signal detection means that measures the period of the signal converted into a digital signal by the comparator 23 and detects a synchronization signal from the measurement result. The pilot signal detection circuit 24 is configured as a pilot signal detection means for detecting a pilot signal from the digital signal output from the comparator 23, and the detected pilot signal is input to the logic circuit 25.

A signal from a discriminating circuit 29 constituting the discriminating means is input to the logic circuit 25.
9, when a determination result indicating that the output pattern is being reproduced is obtained, the determination circuit 29 outputs a high level determination signal for a certain period of time on the condition that a pilot signal is detected by the pilot signal detection circuit 24. When a determination result indicating that the entering side pattern is being reproduced is obtained, the determination signal generation means always outputs a high level determination signal to the AND circuit 14. The discrimination circuit 29 selects the magnetic head 2 based on the phase information of the magnetic head switching signal.
It is determined whether or not the reproduction patterns A and 2B are input-side deflection patterns in which a pilot signal exists after a synchronization signal, and output-side patterns in which a pilot signal exists before a synchronization signal. The AND circuit 14 transfers the first sample-and-hold signal to the first sample-and-hold circuit 18 and the delay circuit 21 on condition that the judgment signal is output from the logic circuit 25 and the synchronization signal is detected from the synchronization signal detection circuit 22. Output to. The delay circuit 21 is configured to output a second sample and hold signal to the second sample and hold circuit 20 after a certain period of time after inputting the first sample and hold signal. That is, the AND circuit 14 and the delay circuit 21 are configured as sample and hold signal generating means.

The logic circuit 27 monitors the outputs of the pilot signal detection circuit 24, the synchronization signal detection circuit 22, and the determination circuit 29, and even if a certain period of time has elapsed after the synchronization signal was detected during playback of the input side pattern, the pilot signal is not detected. The synchronizing signal erroneous detection determining means outputs a reference signal selection command to the changeover switch 28 only when the reference signal selection command is not detected. The changeover switch 28 selects the reference voltage 30 indicating the tracking error reference signal when the reference signal selection command is output from the logic circuit 27, and selects the output signal of the second sample and hold circuit 20 at other times. It is configured as a selection means that outputs the selected signal to the adder 13.

On the other hand, the low-pass filter 6 is constructed as a pilot signal extraction means for extracting the ATF pilot signal from the reproduced signals of the magnetic heads 2A and 2B, and outputs the extracted pilot signal to the rectifier circuit 17. The rectifier circuit 17 is configured as an amplitude detecting means for detecting the amplitude of the pilot signal, and outputs the detected signal to the first sample hold circuit 18 and the subtracter 19. When the first sample and hold circuit 18 receives the first sample and hold signal from the AND circuit 14, it samples and holds the output signal of the rectifier circuit 17, and outputs the held signal to the subtracter 19. ing. The subtracter 19 subtracts the output signal of the first sample hold circuit 18 and the output signal of the rectifier circuit 17, and outputs the resultant signal to the second sample hold circuit 20. When the second sample and hold circuit 20 receives the second sample and hold signal from the delay circuit 21, it samples and holds the output signal of the subtracter 19, and outputs the held signal to the changeover switch 14 as a tracking error signal. It is supposed to be done. That is, the first sample and hold circuit 1
8, the subtracter 19, and the second sample and hold circuit 20 are configured as tracking error detection means.

The capstan motor 9 rotates with the capstan shaft 8 in contact with the pinch roller 10 via the magnetic tape 1,
It is configured as a magnetic tape running means for running the magnetic tape 1 from one reel to the other reel by the rotation of the capstan motor 9. The capstan motor 9 is provided with an FG signal generator 26 as a rotation speed detection means for detecting the rotation speed of the capstan motor 9, and the output signal of the FG signal generator 26 is input to the FV converter 12. There is. The FV converter 12 is configured as a deviation signal generating means that outputs a rotation speed deviation signal to suppress the deviation between the signal from the FG signal generator 26 and the reference rotation speed to zero, and the rotation speed deviation signal is outputted to an adder. 13 is input. The adder 13 is configured as a rotation control command signal generating means that adds the tracking error signal or reference voltage 15 input from the changeover switch 14 and the rotation speed deviation signal input from the FV converter 12 to generate a rotation control command signal. has been done.

This rotation control command signal is input to the drive circuit 11. This drive circuit 11 is configured as a rotation drive means for rotationally driving the capstan motor 9 in accordance with a rotation control command signal.

In the above configuration, when the capstan motor 9 is rotationally driven and the rotary cylinder 3 is rotationally driven, the magnetic tape 1 attached to the reel 6 connects the post 4, the rotary cylinder 3, the post 4, and the capstan shaft 8. reel 7 through
Run to the side. At this time, the magnetic heads 2A and 2B trace designated tracks on the magnetic tape 1 as the rotary cylinder 3 rotates. In this case, as shown in FIG. 3, when the magnetic heads 2A, 2B trace the main track T1, the synchronization signal 104 and the pilot signal 105C are sequentially reproduced. At this time, the track T before the main track T1.

When the pilot signal 105A is recorded on the track T2 after the main track T1, and the pilot signal 105B is recorded on the track T2 after the main track T1, the low-pass filter 16 outputs a signal with a waveform as shown in (b) of FIG. be done. When this signal is rectified through the rectifier circuit 17, it is output as a signal as shown in FIG. 3(c).

On the other hand, when the signals reproduced by the magnetic heads 2A and 2B are input to the comparator 23, the reproduced signals are converted into digital signals. When this digital signal empty pilot signal is detected, the logic circuit 25 outputs a signal as shown in (d) of FIG. 3 for two blocks after this detection is completed. When a synchronization signal is detected from the digital signal, the synchronization signal detection circuit 22 outputs a signal as shown in (e) of FIG. After a certain period of time has elapsed, the delay circuit 21 outputs a signal as shown in FIG. Then, the output signal from the AND circuit 22 causes the first sample hold circuit 18 to perform sample bold, and the signal from the delay circuit 21 causes the second sample hold circuit 20 to perform sample hold. At this time, the voltage held by the second sample and hold circuit 20 is the magnetic head 2A,
This is the difference in the amplitude of the pilot signal indicating the amount of protrusion of 2B to adjacent tracks, and corresponds to the deviation of the front and rear centers with respect to the main track T1. That is, the held voltage will represent a tracking error signal.

On the other hand, when the magnetic heads 2A and 2B run on the incoming ATF pattern of the main track T, as shown in FIG. Figure 4 (
A signal as shown in (b) is outputted, and a signal as shown in (c) of FIG. 4 is outputted from the rectifier circuit 17. When the magnetic heads 2A, 2B detect the synchronization signal 104, the synchronization signal detection circuit 22 outputs the signal ((
A signal as shown in (d) is output, and after a certain period of time has elapsed, a signal as shown in (e) of FIG. 4 is output from the delay circuit 21, and each signal is sampled and held.

Next, as shown in FIG. 5, there is no pilot signal on the main track T two blocks before the detection position (A) of the synchronization signal 106, and an error occurs due to the deterioration of the S/N of the recording signal. When the synchronization signal 106 is recorded, the low-pass filter 16 outputs a signal as shown in FIG. 5(b) as the magnetic tape 1 runs and the rotary cylinder 3 rotates. Then, the rectifier circuit 17 outputs a signal as shown in (c).

Furthermore, the reproduced signals of the magnetic heads 2A and 2B are input to the comparator 23 and converted into a digital signal, and when the pilot signal 105C is detected from this digital signal, the logic circuit 25 outputs the signal shown in (E) of FIG. A high level signal like this is output for a certain period of time. When the synchronization signal 106 is detected from the digital signal, the synchronization signal detection circuit 22 outputs a signal as shown in (d) of FIG. At this time, since the output pulse of the logic circuit 25 is inverted to a low level, the AND circuit 14 does not output the first sample and hold signal, and the synchronization signal 10
6 is detected, this synchronization loss signal 106 is invalidated as an erroneous synchronization signal, and it is possible to prevent tracking control from being performed due to the detection of an erroneous synchronization signal 106.

Next, as shown in FIG. 6, the pilot signal does not exist in the main track T where the incoming ATF pattern is recorded four blocks after the detection position (A) of the synchronizing signal 106, and the S/ If an incorrect synchronization signal 106 is recorded due to deterioration of N, as the magnetic tape 1 runs and rotates, and the rotating cylinder 3 rotates, the low-pass filter 16 outputs the signal shown in (b) of FIG. A signal like this is output. When the output signal of the low-pass filter 16 is rectified by the rectifier circuit 17, it becomes a signal as shown in (c) of FIG.

On the other hand, when the reproduction signals of the magnetic heads 2A and 2B are input to the comparator 23 and converted into digital signals, and the synchronization signal 106 is detected from this digital signal, the synchronization signal detection circuit 22 outputs the signal (d) in FIG. The signal shown in is output.

Then, after a certain period of time has elapsed, the delay circuit 21 outputs (E)
The signal shown in is output. and sync signal 1
06 is detected, a certain period of time has elapsed, that is, the synchronization signal 10
When the pilot signal is not detected even at the position (C) that is four blocks after the detection position (A) in FIG. 6, the logic circuit 27 outputs a reference signal selection command as shown in FIG. A pulse is output. In this case, since the second sample and hold circuit 20 samples and holds the output signal of the subtracter 19 due to the incorrect synchronization signal 106, when the second sample and hold circuit 20 samples and holds the output signal of the subtracter 19 due to the signal from the delay circuit 21, Figure 6 (
A voltage as shown in (g) is held, and this held voltage is input to the adder 13 via the changeover switch 28. However, when the reference signal selection command is output from the logic circuit 27, the changeover switch 28 selects the reference voltage 30, so when an incorrect synchronization signal 106 is detected, the tracking control is immediately shifted to the reference voltage 30. This makes it possible to perform stable tracking control even if the quality of the signal recorded on the magnetic tape 1 is poor and an erroneous synchronization signal is detected.

Effects of the Invention As is clear from the embodiments described above, the present invention determines that the detected synchronization signal is a normal synchronization signal only when the synchronization signal is detected a certain period of time after the pilot signal is detected. Tracking control is executed according to the synchronization signal, and if a pilot signal is not detected even after a certain period of time has passed after the synchronization signal is detected, an erroneous synchronization signal is detected and tracking control is executed according to the tracking error reference signal. This makes it possible to perform stable tracking control even when the quality of signals written on the magnetic tape is poor.

[Brief explanation of the drawing]

FIG. 1 is a block configuration diagram showing a magnetic tape reproducing apparatus in an embodiment of the present invention, FIG. 2 is a diagram for explaining the positional relationship between a synchronization signal and a pilot signal recorded on a magnetic tape, and FIG. 3 Figure 4 is a diagram to explain the reproduction status of the output ATF pattern. Figure 5 is a diagram showing the reproduction status of the output ATF pattern. FIG. 6 is a diagram for explaining the reproduction state when an erroneous synchronization signal is recorded in the incoming ATF pattern. 1...Magnetic tape, 2A, 2B...Magnetic head, 3
...Rotating cylinder, 6,7...Reel, 9...Capstan motor, 11...Drive circuit, 12...F
V converter, 13... Adder, 14... AND circuit, 16... Low pass filter, 17... Rectifier circuit, 18... First sample hold circuit, 19...
Subtractor, 2°...Second sample and hold circuit, 21
...Delay circuit, 22...Synchronization signal detection circuit, 23.
... Comparator, 24 ... Pilot signal detection circuit, 25 ... Logic circuit, 26 ... FG signal generator, 2
7...Logic circuit, 2...Selector switch, 29...
Discrimination circuit, 3o...Reference voltage. Figure 4 Figure 6 (F) Figure 5 (A)

Claims (1)

[Claims] A magnetic tape running means that contacts the magnetic tape mounted on a pair of reels and rotates the magnetic tape to run the magnetic tape from one reel to the other reel, a magnetic head that reproduces information on the magnetic tape, and a magnetic head that is accompanied by a magnetic tape. a rotating cylinder that rotates to move the magnetic head along a specified track on the magnetic tape; a signal conversion means that converts the signal reproduced by the magnetic head into a digital signal; and a signal conversion means that converts the synchronization signal recorded on the magnetic tape. synchronization signal detection means for detecting from the output signal of the means; pilot signal extraction means for extracting a pilot signal from the signal reproduced by the magnetic head; and amplitude detection means for detecting the amplitude of the pilot signal extracted by the pilot signal extraction means. a tracking error detection means for detecting a tracking error by sample-holding the detection output of the amplitude detection means in response to a sample hold signal; a rotation speed detection means for detecting the rotation speed of the magnetic tape running means; and a rotation speed detection means. deviation signal generating means for outputting a rotational speed deviation signal for suppressing the deviation between the detection output of the and the reference rotational speed to zero, and a pilot signal for detecting a pilot signal recorded on the magnetic tape from the output signal of the signal conversion means. Based on the detection means and the phase information of the magnetic head switching signal, it is determined whether the reproduction pattern of the magnetic head is an incoming pattern in which a pilot signal exists after a synchronizing signal or an outgoing pattern in which a pilot signal exists before a synchronizing signal. a discriminating means for discriminating; and a discriminating means that outputs a discriminating signal only for a certain period of time on condition that a pilot signal is detected by a pilot signal detecting means when a discriminating result indicating when the output pattern is being reproduced is obtained by the discriminating means; a determination signal generating means that always outputs a determination signal when the means obtains a determination result indicating that the input side pattern is being reproduced; A sample-and-hold signal generating means outputs a sample-and-hold signal to the tracking error detecting means only, and the outputs of the pilot signal detecting means, the synchronizing signal detecting means, and the determining means are monitored, and a synchronizing signal is detected when the input side pattern is reproduced. A synchronization signal error detection determination means outputs a reference signal selection command only when a pilot signal is not detected even after a predetermined period of time has elapsed; A selection means for selecting and outputting an output signal of the tracking error detection means, a rotation control command signal generation means for outputting a rotation control command signal from the signal selected by the selection means and the rotation speed deviation signal, and a rotation control command signal. 1. A magnetic tape playback device comprising: rotational drive means for rotationally driving a magnetic tape running means according to the invention.