JPH0487047A - Magnetic tape reproducing device - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

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 a desired trajectory on the track. 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 the synchronization signal in the ATF signal from the 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 rising edge of the signal. Alternatively, 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 a predetermined setting condition.

However, in the conventional method, 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 avoided. could not be detected. 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 corresponding 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 detected output of the rotation speed detection means and a reference rotation speed to zero; Rotation control command signal generation means for outputting a rotation control command signal from the rotation speed deviation signal and the detection output of the tracking error detection means; rotation drive means for rotationally driving the magnetic tape running means in accordance with the rotation control command signal; and signal conversion means. pilot signal detection means for detecting a pilot signal recorded on the magnetic tape from the output of the
Judgment signal generation means that outputs a judgment signal only for a certain period of time on condition that a pilot signal is detected by the pilot signal detection means, and only when a detection signal is output from the synchronization signal detection means during the generation period of the judgment signal. This magnetic tape reproducing apparatus includes sample-and-hold signal generating means for outputting a sample-and-hold signal to tracking error detecting means.

Function: As shown in FIG. 2, a synchronizing signal 100 and a pilot signal 101 are recorded on the magnetic tape used in the magnetic tape reproducing apparatus described above. Among these signals, the pilot signal 101 is recorded at a position before the position where the magnetic head reproduces the synchronizing signal 100, for example, two blocks earlier. Therefore, when the normal synchronization signal 100 is detected, the magnetic head detects the synchronization signal 100.
The pilot signal 101 will be detected two blocks before the block passes through the recorded position.

Therefore, in the present invention, 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 when a detection signal is output from the synchronization signal detection means during the generation period of this determination signal. Tracking control is performed by outputting a sample and hold signal to the tracking error detection means only when a pilot signal is not detected, so if a synchronization signal is detected even though no pilot signal is detected, the detection of this synchronization signal is invalidated. by doing,
Erroneous detection of synchronization signals can be prevented, and even if the quality of the signals recorded on the magnetic tape is poor, stable tracking can be performed.

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 2
B reproduces various information recorded on the magnetic tape 1 and outputs the reproduced signals to a low-pass filter 16 and a comparator 23. The comparator 23 is configured as a signal conversion means for converting the signals reproduced by each head 2A, 2B into a digital signal, 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. The logic circuit 25 is configured as a judgment signal generating means for outputting two blocks of pressure logic pulse signals as judgment signals to the AND circuit 14 from the time when the pilot signal detection circuit 24 finishes detecting the pilot signal. The AND circuit 14 combines the output signal of the synchronization signal detection circuit 22 and the logic circuit 2.
The first sample-and-hold signal is connected to the first sample-and-hold circuit 18 and the delay path 21 on the condition that it is ANDed with the output signal of No. 5.
The delay circuit 21 outputs to the second sample and hold circuit 20 a second sample and hold signal delayed by a certain period of time from 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 that outputs a sample-and-hold signal only when a synchronizing signal is detected during a period in which a pulse signal is generated from the logic circuit 25.

On the other hand, the low-pass filter 16 is configured as a pilot signal extracting 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 detection means for detecting the amplitude of the pilot signal, and outputs the detection signal to the first sample hold circuit 18 and the subtracter 19. The first sample and hold circuit 18 samples and holds the output signal of the rectifier circuit 17 when receiving the first sample and hold signal from the AND circuit 14, and outputs the held signal to the subtracter 19. It has become. The subtracter 19 subtracts the output signal of the first sample and hold circuit 18 and the output signal of the rectifier circuit 17, and outputs the resultant signal to the second sample and hold circuit 20. The second sample and hold circuit 20 samples the output signal of the subtracter 19 in accordance with the second sample and hold signal from the delay circuit 21, holds it, and outputs the held signal as a tracking error signal. That is, the first
The sample and hold circuit 18, the subtracter 19, and the second sample and hold circuit 29 are configured as tracking error detection means, and the second sample and hold circuit 2
The output signal of 0 is sent to adder 1 as a tracking error signal.
3 is entered.

The capstan motor 9 rotates while in contact with the pinch roller 10 via the capstan shaft 8 or 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. ing. FV converter 12 is FG
It is configured as a deviation signal generating means that outputs a rotation speed deviation signal for suppressing the deviation between the signal from the signal generator 26 and the reference rotation speed to zero, and the rotation speed deviation signal is sent to the adder 1.
3 is input. The adder 13 combines the tracking error signal input from the second sample hold circuit 20 and F
It is configured as a rotation control command signal generating means that adds the rotation speed deviation signal inputted from the V converter 12 to generate a rotation control command signal. This rotation control command signal is input to the drive circuit 11. This drive circuit 1
Reference numeral 1 is constituted 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 moves the post 4, the rotary cylinder 3, the post 5, and the capstan shaft 8. It travels to the reel 7 side through the reel. At this time, the magnetic heads 2A and 2B trace the designated trunk of the magnetic tape 1 as the rotary cylinder 3 rotates. In that case, as shown in FIG. 3, when the magnetic heads 2A and 2B trace the main track T, the pilot signal 102C and the synchronization signal 103 are sequentially reproduced. At this time, the track T before the main track T1. When the pilot signal 102A is recorded on the main track T2 and the pilot signal 102B 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. is output. 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 signal reproduced by the magnetic heads 2A and 2B is input to the comparator 23, it is converted into a reproduced signal or a digital signal, and when a pilot signal is detected from this digital signal, it is During the block, the logic circuit 25 outputs a positive pulse signal. If a synchronization signal is detected from the output signal of the comparator 23 during this period, the AND circuit 14 outputs a first sample and hold signal as shown in (e). Then, after a certain period of time, the delay circuit 21 outputs the second sample and hold signal as shown in (v). In other words, the pilot signal 102C is detected, and the synchronization signal 102C is detected within two blocks from the end of this detection.
3 is detected, it is assumed that the correct synchronization signal 103 has been detected, and the first sample-hold signal and the second sample-hold signal are output, and the first sample-hold circuit 18 and the second sample-hold circuit 18 are output according to each sample-hold signal. Sampling and holding of circuit 20 is performed. At this time, the voltage held by the second sample and hold circuit 20 is the difference in amplitude of the pilot signal indicating the amount of protrusion of the magnetic heads 2A and 2B to adjacent tracks, and is caused by the deviation of the head center with respect to the main track T1. It will be equivalent. That is, the held voltage will represent a tracking error signal.

Next, as shown in FIG. 4, if an incorrect synchronization signal is recorded on the main track T at a position 3 blocks or more away from the pilot signal 102C due to deterioration of the S/N of the recording signal, the magnetic As the tape 1 travels and the rotary cylinder 3 rotates, the low-pass filter 16 outputs a signal as shown in FIG. 4(b).

When the output signal of the low-pass filter 16 is rectified by the rectifier circuit 17, it becomes a signal as shown in FIG. 4(c).

On the other hand, when the reproduction signals of the magnetic heads 2A and 2B are input to the comparator 23, the logic circuit 25 outputs the signal shown in (E) for two blocks from the end point when the pilot signal 102C is detected by the pilot signal detection circuit 24. A positive pulse signal like this is output. Thereafter, when the synchronization signal detection circuit 22 detects the synchronization signal 104, the synchronization signal detection circuit 22 outputs a pulse signal as shown in FIG. 4(d). Since the synchronization signal 104 is more than three blocks away from the pilot signal 102C, when the synchronization signal 104 is detected, the level of the output signal of the logic circuit 25 is inverted to the low level, and the synchronization signal 1
Even if 04 is detected, the first sample and hold signal is not output from the AND circuit 14, and it is possible to prevent tracking control from being performed due to the detection of an erroneous synchronization signal 104.

Effects of the Invention As is clear from the above embodiments, the present invention determines a detected synchronization signal as a normal synchronization signal only when a synchronization signal is detected a certain time after a pilot signal is detected, and determines the detected synchronization signal as a normal synchronization signal. Since the tracking control is executed according to the magnetic tape, an accurate synchronization signal can be detected even when the quality of the signal written on the magnetic tape is poor, and stable tracking control can be performed.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing a magnetic tape reproducing apparatus according to 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 is a diagram for explaining the operation when a normal synchronization signal is detected by the device shown in FIG.
FIG. 4 is a diagram for explaining the operation when an erroneous synchronization signal is detected by the apparatus shown in FIG. 1. 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, 20...Second sample hold circuit, 2
DESCRIPTION OF SYMBOLS 1... Delay circuit, 22... Synchronization signal detection circuit, 23
... Comparator, 24 ... Pilot signal detection circuit, 25 ... Logic circuit, 26 ... FG signal generator. Name of agent: Patent attorney Shigetaka Awano and one other person Figure 1 Figure 2 Figure 4 (f)

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. a deviation signal generation means for outputting a rotation speed deviation signal for suppressing the deviation between the detected output of the and the reference rotation speed to zero, and a rotation control command signal outputted from the rotation speed deviation signal and the detection output of the tracking error detection means. a rotation control command signal generation means for rotating the magnetic tape traveling means in accordance with the rotation control command signal; a pilot signal detection means for detecting a pilot signal recorded on the magnetic tape from the output of the signal conversion means; Judgment signal generation means that outputs a judgment signal only for a certain period of time on condition that a pilot signal is detected by the pilot signal detection means, and only when a detection signal is output from the synchronization signal detection means during the generation period of the judgment signal. A magnetic tape playback device comprising sample-hold signal generating means for outputting a sample-hold signal to tracking error detecting means.