JPH0762923B2 - Playback device - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a reproducing apparatus capable of reproducing an information signal from a plurality of tracks arranged in parallel while conveying a recording medium at any of at least two different traveling speeds. Examples of such a reproducing device include a magnetic recording / reproducing device and an optical reproducing device.
Although various reproducing apparatuses are conceivable, in the present specification, a video tape recorder (hereinafter referred to as VTR) for reproducing video information from a magnetic tape on which a television signal is recorded will be described as an example.

<Description of Prior Art> In recent years, VTRs have been developed and produced that have enabled high-density magnetic recording, slowed the running speed of magnetic tape, and narrowed the track pitch to enable long-term recording / reproducing.

In order to be compatible with conventional formats, these VTRs are configured with a single VTR that has different recording / playback times such as standard time and long time. When reproducing a magnetic tape recorded on such a VTR that can switch the time mode, the tape must be run at the same running speed as at the time of recording, that is, in the same time mode as at the time of recording. Since the tape format is different, the reproduced image is disturbed. It is very difficult for the user to manually switch the playback time mode while watching the playback image. Therefore, conventionally, the output of a frequency generator that records a control signal (hereinafter referred to as CTL signal) at one frame intervals at the end of the tape during recording and detects the number of revolutions of the capstan motor that is proportional to the running distance of the magnetic tape during playback.
By counting how many pulses are output during the CTL signal generation interval, it is detected whether the time mode is different between recording and reproduction, and the reproduction time mode is automatically switched. Here, a description will be given based on this conventional example and the drawings. FIG. 1 shows a conventional method for counting the FG of a capstan motor from a CTL signal. In FIG. 1, 1 is a magnetic tape, which is run in the direction of the arrow by a capstan 2 and a pinch roller 3.
A video signal recorded obliquely with respect to the longitudinal direction of the magnetic tape 1 is reproduced from the magnetic tape 1 by a rotary magnetic head (not shown) attached to a known rotary drum. The capstan 2 is rotationally driven at a predetermined speed by a capstan motor 4 via a belt 5. Reference numeral 6 is a frequency generator that detects the number of revolutions of the capstan motor 4, and the output pulse number and the traveling speed of the magnetic tape 1 are in a proportional relationship, and this signal is sent to the clock of the counter 8 via the amplifier 7. Input to input terminal CK. On the other hand, reference numeral 9 is a control head for reproducing the CTL signal recorded on the tape 1 in frame units, and is inputted to the reset terminal R of the counter 8 through the amplifier 10 and the waveform shaper 11. With the above input, the rotation speed of the capstan motor is counted in the CTL section from the CTL signal to the next CTL signal, and the output Q ₁
~ Q ₄ is output to the magnitude comparator 13. On the other hand, the output of the reference setting device 12 and the comparator 13
When compared with, and when it is larger or smaller than the reference set value, a high level is output to the output Q ₅ . That is, assuming that the number of pulses input to the counter 8 in the CTL section in the standard mode is 44 pulses, the tape feed speed is halved in the long time mode in which the recording time is doubled. It becomes 1/2. Therefore, if the magnetic tape recorded in this long-time mode is played back in standard mode, the original number of pulses between CTLs is not 44, but only half of that, 22 pulses will be input. Therefore, set 12 reference set values
It is set between 22 and 44 pulses, and when it is played back in standard mode and counts less than the set value, the recording mode is long mode, and when it counts more than the set value, the recording mode is standard mode. It will be. However, in the case where the CTL signal is lacking or the format 5 which does not record the control signal from the beginning at the time of recording is used, inconvenience occurs.

For example, when a recording format in which a tracking control pilot signal is superimposed on a video signal instead of the CTL signal is adopted, a new method for detecting the recording mode and determining the tape running speed during reproduction is required.

<Objects of the Invention> In view of the above points, the present invention relates to a recording medium at the time of recording even in a recording format in which a plurality of different pilot signals are recorded together with an information signal in a predetermined order for tracking control. An object of the present invention is to provide a reproducing device which can surely match the traveling speed and the traveling speed of a recording medium at the time of reproduction, and which is extremely unlikely to be set to an incorrect traveling speed.

<Description of Embodiment> FIGS. 2 and 3 are principle diagrams for explaining the present embodiment.

FIG. 2 (a) is a diagram showing a recording track on the magnetic tape.
a ₁ , a ₂ , ... are the tracks recorded in the plus azimuth recording head, b ₁ , b ₂ , ... are the minus azimuth recording tracks, and a ₁ -b ₁ -a _2- b ₂ −a ₃ −b ₃ ……
Is recorded.

Here, the pilot signal of frequency f ₁ is recorded in the tracks a ₁ , a ₃ , a ₅ ..., and f ₃ is recorded in the tracks b ₁ , b ₃ , b ₅ ... by being superimposed on the video signal. . The frequencies f ₁ , f ₂ , f ₃ , f ₄ are f ₁ <f ₂
If <f ₃ <f ₄ , then f ₂ −f ₁ = f ₄ −f ₃ = f ₅ , f ₄ −f ₂ = f ₃ −
There is a relationship of f ₁ = f ₆ and f ₅ ≠ f _6, and when reproducing a track in which the pilot signals of f ₁ , f ₂ , f ₃ and f ₄ are recorded respectively,
The pilot signals recorded in the adjacent tracks are reproduced as crosstalk, and the signals with the same frequency as the pilot signals recorded in the tracks at the reproduction output are F ₁ , F ₂ , F ₃ , F.
By multiplying by ₄ , signals of frequencies f ₅ and f ₆ are obtained as crosstalk. A tracking control signal (hereinafter referred to as an ATF signal) can be obtained by comparing the levels of these signals. The above is an example for obtaining the ATF signal, but various combinations of frequencies of frequency signals to be superimposed on the video signal are possible.

Now, consider a case where the track thus recorded is reproduced (standard mode) at a traveling speed higher than that at the time of recording (long-time mode). The broken line in FIG. 2 (a) shows the head locus in the case of reproducing in the standard mode, the arrow α indicates the tape running, and the arrow β indicates the skim direction of the head. The running speed (second running speed) of the tape in the long time mode is 1 / the running speed of the standard mode (first running speed).
It is also assumed that the head width to be used is 2 times the head width in the standard mode for reproducing the head for the long time mode. In this state, when the tape is traced at the tape speed in the standard mode, the track pattern on the tape and the track of the playback head do not match each other, and the pilot signal (f ₁ ~
f ₄ ) playback output and the frequency signal (F ₁ ~
F ₄ ) cannot be dealt with. For this reason, the ATF signal changes every two frame periods as shown in FIG. In the figure, then again, playback when head is that scanning the B ₂ field, B ₂ during the scanning of field, pilot signal F having the same frequency as F ₃ on the tape since the frequency signal to be multiplied is F _{3 Of the} tracks recorded with ₃ , the ATF signal output controls the phase of the capstan so that the track b ₄ closest to B ₂ is reproduced, but due to the above reason, the inclination of the track and the reproduction head is different. Therefore, to become B ₂ field in good tracking state is only the midpoint in B ₂ field. The pilot signal f ₄ of tracks a ₄ adjacent in the scanning start point, since f ₁ of track a ₅ adjacent to the opposite side instead to f ₄ are reproduced large in the scanning end point, respectively ATF output tape feeding at the start It goes high to speed up, and goes low at the end to slow down tape feed.

Here, assuming that the normal ATF output voltage is vcc / 2 in a good tracking state, the ATF output shows a vibration waveform of two frame cycles centering on Vcc / 2.

FIG. 3 is a diagram showing the mistraking state when the recording in the standard mode is reproduced in the long time mode. The difference from FIG. 2 is that the same mitrask state is repeated in exactly four frame periods. Therefore, the ATF output oscillates in a 4-frame cycle as shown in (b) in the figure. As described above, when the tape is reproduced at a tape feeding speed different from that at the time of recording, the ATF output signal causes periodic vibration.

FIG. 4 is a block diagram of a basic circuit embodying the idea described above. 11a and 11b are reproduction rotary heads, and 12 is a tracking pilot signal (f _{1 to} f ₄₎ reproduced by the reproduction heads 11a and 11b. ), A known demodulation circuit (signal processing circuit) for obtaining the ATF signal from 13), 13 is a speed control servo circuit of the capstan motor 14, 14 is a capstan motor, and 15 and 16 are only 2 and 4 frame periodic signals, respectively. Bandpass filter for extracting the rectifier detection circuit 17,18
Is a comparator with the output voltage E ₁ of the adjustable constant voltage source 25, 15, 17 and 19 are the first detecting means, and 16, 18 and 20 are the second detecting means.
Detection means is configured. Reference numerals 21, 22 are integrating circuits, 23, 24 are comparators with the voltage E ₂ of the adjustable constant voltage source 26, 21 and 23 constitute a first judging means, and 22 and 24 constitute a second judging means. It 27 is a switching circuit (switching means) for switching the tape running speed. In addition to the capstan servo circuit, the ATF signal from the ATF demodulation circuit 12 passes BPFs 15 and 16 (for NTSC signal reproduction) that pass only signals of 2 and 4 frame periods.
In case of VTR, it becomes 15Hz and 7.5Hz respectively)
Only the respective frequencies are extracted and detected at 17 and 18 to become a DC signal. Since this detection output signal also contains a simple noise component, the threshold voltage E ₁ and the comparator 19,2
Compared at 0, the high level signal (first and second detection signals) is output only when it is higher than the E ₁ level. These output signals are averaged by the integrator circuits 21 and 22, and when the frequency of these output signals becoming high level exceeds a predetermined level, the output of the integrator circuits 21 and 22 is set to a preset threshold voltage. E
₂ will be exceeded, and the outputs A and B of the comparators 23 and 24 will be exceeded.
Are high-level (hereinafter “H”) outputs (first and second determination outputs). When the output A is "H", the tape recorded in the long time mode is playing at the standard speed, and when the output B is "H", the tape recorded in the standard mode is played in the long time mode. The case is shown. Of course, if you play back in the same mode recorded in the standard mode, or if you record in the long time mode and play in the long time mode, output
It goes without saying that neither A nor B will be "H". output
A and B are input to the switching control circuit 27, and the tape running speed is determined according to the outputs A and B.

FIG. 5 is a diagram showing a part of the program of the switching control circuit 27.

First, the user's setting mode is read to determine whether it is the standard mode or the long time mode. In the standard mode, the tape is run at the (first) running speed in the standard mode and output A
Detects whether or not is at a high level. When the output A is low level, the reproduced video signal is output as it is on the TV monitor. In case of high level, long time mode (second)
Run at a running speed. When the long time mode is set, the tape is run at the (second) running speed corresponding to the long time mode, and it is detected whether or not the output B is at the high level. When the output B is low level, the reproduced video signal is output as it is on the TV monitor. At the high level, the tape is run at the (first) running speed in the standard time mode. By doing this, a beautiful image without noise bars can be obtained on the TV monitor only when the same reproduction mode as that during recording is reached. In the description of this embodiment, the tape speed ratio between the standard mode and the long time mode is 2:
However, when the ratio is N: 1 (N: integer),
When played at N times the tape speed that should be played originally, N
It can be seen that the ATF output signal fluctuates in a cycle of 2 × N frames when reproduced at 1 / N for 2 frames regardless of the.
Therefore, the passing frequencies of BPFs 15 and 16 at that time are 15
Hz and 15 / N Hz. Therefore, the present invention can be applied to other speed ratios other than 2: 1, or even when there are three or more kinds of reproduction speeds.

Although pilot signals of four frequencies (f ₁ ~f ₄₎ In the present embodiment has been described if recorded, from tapes pilot signals having different frequencies in adjacent tracks are recorded, the pilot signal Is applicable to any reproducing apparatus of the type that reproduces a track signal to obtain a tracking signal.

<Explanation of Effects> As described above, according to the present invention, when reproducing a recording medium in which a plurality of different kinds of tracking control pilot signals are recorded together with the information signal in a predetermined order, the recording medium at the time of recording is reproduced. It is possible to reliably match the running speed of (1) and the running speed of the recording medium at the time of reproduction without any error, and always obtain a good reproduction information signal.

[Brief description of drawings]

FIG. 1 is an explanatory view of a conventional technique, FIGS. 2 (a) and 2 (b) are explanatory views when a tape recorded in a long time mode is reproduced in a standard mode, and FIGS. 3 (a) and 3 (b). Is an explanatory diagram for reproducing a tape recorded in a standard mode in a long time mode, FIG. 4 is a detection circuit diagram for detecting a difference in running speed according to the present embodiment, and FIG. 5 is a switching control circuit in FIG. It is a figure which shows the program of. In the figure, 11a and 11b are reproduction rotary heads, 12 is an ATF demodulation circuit (signal processing circuit), 15 and 16 are bandpass filters, 17 and 18 are detection circuits, and 19 and 20 are comparators. It constitutes first and second detection means. Reference numerals 21 and 22 are integrating circuits, and 23 and 24 are comparators, respectively, which form first and second determining means. 27 is a switching control circuit (switching means).

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Susumu Kouzuki 770 Shimonoge, Takatsu-ku, Kawasaki, Kanagawa Canon Inc. Tamagawa Plant (56) References JP-A-59-31456 (JP, A) JP-A-SHO 59-19260 (JP, A)

Claims (1)

[Claims] 1. A plurality of parallel pilot tracks are formed at a first traveling speed or at a second traveling speed slower than the first traveling speed, and a plurality of different pilot signals for tracking control together with an information signal. Is a reproducing device for reproducing the information signal from a recording medium in which the information is recorded in a predetermined order, and a reproducing rotary head for reproducing the information signal from the recording medium, A signal processing circuit for forming a tracking control signal by using a pilot signal; and a first processing circuit for detecting that the output signal of the signal processing circuit fluctuates in a first cycle and outputting a first detection signal. No. 1 detection means and second detection for detecting that the output signal of the signal processing circuit fluctuates in a second cycle longer than the first cycle, and outputting a second detection signal. Means and a first determination indicating that the track formed at the second traveling speed is being reproduced at the first traveling speed by the occurrence of the first detection signal at a predetermined frequency or more. The first determination means for outputting an output, and the second detection signal generated at a frequency of a predetermined frequency or more, thereby reproducing the track formed at the first traveling speed at the second traveling speed. Second determination means that outputs a second determination output indicating that the recording medium is traveling at a first traveling speed, and when the recording medium is traveling at a first traveling speed, the first determination output outputs the second traveling speed to the recording medium. And a switching means for causing the recording medium to travel at the first traveling speed according to the second determination output when the recording medium is traveling at the second traveling speed.