JPS6028051A - Automatic recording tape speed deciding device of magnetic recording and reproducing device - Google Patents

Abstract

PURPOSE:To always decide the recording tape speed with high stability with no use of a control signal by deciding the recording speed from the information on the reproduced pilot signal. CONSTITUTION:The fS component of a pilot signal is always detected with LP heads A and B of narrow width regardless of the state of a head which is reproducing a video signal. Based on this detecting information, the speed of the recording tape is discriminated. In other words, both outputs CFG and P of a frequency generator 7 and a zero-cross detector 17 are supplied to a discriminating circuit 18. An SP is decided if the ratio R between the frequency fCFG of the generator 7 and the frequency fP of the detector 17 is larger than 12. While an LP is decided when the ratio R is smaller than 12. Then the reproduction mode is automatically switched for a switch 19 and a servo circuit 5. Thus, the discrimination of recording tape speed with high stability with no use of a control signal is always made possible.

Description

[Detailed Description of the Invention] [Field of Application of the Invention] The present invention relates to a magnetic recording and reproducing apparatus (hereinafter abbreviated as VTR) that automatically determines the recording tape speed during reproduction and automatically switches to a predetermined mode. The present invention relates to an automatic recording tape speed determination device for a playback device.

[Background of the invention]

Rotating head helical scan type V such as home VTR
In TR, some kind of synchronization signal is recorded on the magnetic tape during recording, and during playback, the synchronization signal is reproduced to control the rotational phase of the cab's tongue or rotary head cylinder, thereby controlling the video signal recording track of the magnetic tape. Tracking control is performed using a servo circuit to ensure that the rotating head traces correctly.

As the synchronization signal, a method (C'I'L method) is used in which a pulse signal of 1/2 period of a vertical synchronization signal, usually called a control signal (hereinafter abbreviated as CTL signal), is written at the end of the tape.

In the servo tracking control method using this control signal, the gap between the CTL signals recorded on the tape varies depending on the recording tape speed (if the recording tape speed is halved for long-term recording, the gap between the CTL signals will also be 1/2). /2).

Therefore, the ratio between the frequency of the CTL signal during playback and the frequency of the signal obtained from the frequency generator attached to the cab's tongue shaft or capstan motor shaft, which represents the playback tape speed, is equal to the gap between the CTL signals, that is, the recording tape speed. Respond one to one. Furthermore, since this ratio is constant regardless of the playback tape speed, by measuring this ratio, the recording tape speed can be automatically determined during playback, and the mode can be automatically switched to a predetermined mode (corresponding to the speed during recording). I can do it. An example of such a method for measuring tape recording speed is disclosed in Japanese Patent Application Laid-Open No. 52-115.
705 etc.

The method described above was a method using CTL signals, but this method uses synchronization signals (for example, four types of pilot signals f, f, 1f, f,), which is another servo tracking control method. Even with the method of recording weight on a video track (abbreviated as the Bayrotsu method, an example of which is JP-A-53-116120), it is possible in principle if the repetition frequency of the amplitude change of the reproduced pilot signal, which corresponds to the CTL signal, is used. It is.

However, as is normally done, VTRs perform recording and playback using a pair of heads optimal for each recording tape speed.
system, e.g. a pair of heads A at standard recording tape speed.
', B', and when using a pair of heads A and B with wider and narrower head widths than A' and B' at a recording tape speed of 1/2 of the standard, 1/2 during standard playback. After changing to a pattern recorded at a recording tape speed of will be detected at the same time.

Therefore, in such a state, the amplitude change of the detected pilot signal becomes extremely small, and the S/N ratio deteriorates significantly, making it impossible to stably determine the recording tape speed.

[Purpose of the invention]

The purpose of the present invention is to overcome the drawbacks of the prior art described above (1, C
A recording tape for a magnetic recording and reproducing device that does not require a TL signal, and that can always stably determine the recording tape speed regardless of the number of video heads for recording and reproduction, head width, etc., and automatically switch to a predetermined mode. To provide an automatic speed discrimination device.

[Summary of the invention]

In order to achieve the above object, the present invention provides a system that appropriately selects several types of heads with different head widths depending on recording tape speed and playback tape speed. It is characterized by constantly detecting pilot signals from a pair of narrow heads, and stably determining the delivery tape speed from that information.

[Embodiments of the invention]

Hereinafter, the present invention will be described as a VT having a recording tape speed of 2's in SP (Standard Play) mode and LP (Long Play) mode (LP is 1/2 the tape speed of SP).
The case where the present invention is applied to R will be described in detail with reference to embodiments and drawings.

FIG. 1 is a diagram showing the configuration of a rotating head drum 1 and a video head in this embodiment.
The pair of wide heads A' and B' are for recording and reproducing in SP (standard) mode (including variable speed reproduction), and are set to a pair of narrow heads with the same <180° gap and different azimuths. The heads A and B are for recording and reproducing in the LP mode, and the set A', B' and the set A, B have an angle α (90° in this embodiment). In addition, in the example
The recording track pitch P8 in P mode is 20.5 μm.

In LP mode, track pitch PL = 10.25μ
m, and the head widths A' and B' are 28ttm, and A
, B is set to 15, utn.

Figure 2 shows the rotary head drum of Figure 1 recording on magnetic tape 2 in LP mode first with heads A and B, and from the middle with A'.
, Recording pattern A recorded in SP mode with B' head, ~
A: and the signal waveform diagram at that time are shown. This magnetic tape 2 runs at the reproduction speed of the KLP mode in the direction of the arrow.
The P head A or B scans in the scanning direction of the arrow to reproduce the video signal and pilot signals f, to f4 on the magnetic tape 2. Here, the patterns recorded by the A or B heads are represented by A1-A4, and the patterns recorded by the A' or B' heads are represented by S-A2, respectively.

In this example, special cocoon 53-11 is used as a pie-it method.
6120 etc. are already known four types of pilot frequencies f,
(6,5fn), ft (7,5fH), L (
A 4-frequency pilot method will be described in which 10, 5fH) and fi (9, 5fH) are written field by field on the video track in this order. Here, fH is the horizontal synchronization frequency.

This method is A or A') The rack has a pilot signal f
1 or f 凘, B or B') so that the rack corresponds to a pilot signal f or f, and as shown in FIG. 2, fl, f! , , , f4 are recorded cyclically and sequentially for each track. During playback, the pilot signals of both adjacent tracks of the main track being scanned by the playback head are detected, and the tape running speed is controlled by the capstan motor so that the playback levels are equal, so that the recording track is scanned by the head. Perform tracking servo control to track correctly.

8Wx LP head switching signal that switches between head A and head B every time the head scans one recording track.
o (its period is 2 fields or 1 frame and N
Approximately 1/30 (s) in the TSC method.

The magnetic tape 2 is running at a tape speed in Ll) mode, and head A or B moves by track pitch PL in the tape running direction during one field.
Or pilot signal f at B.

Assuming that only the fi acid component is detected, as shown in Figure 2 ■, the 8W30
If the recording pattern changes to the SP recording pattern midway as shown in (2), the waveform will have a maximum value in an 8-field period.

Therefore, when the LP recording pattern changes to the SP recording pattern during LP playback, if you focus on one frequency (here f, ) of the pilot signal and measure the repetition period or frequency of the amplitude change, you can Speed can be determined.

On the other hand, based on the recording pattern diagram and signal waveform diagram in Figure 6, it is clear that a problem will occur if the SP recording pattern changes to the LP recording pattern during SP playback with SP head A' or B'. explain. The magnetic tape 2 is being played back at a speed SP in the direction of the arrow. The symbols for each part are the same as in Fig. 2, and the head A' or B' during playback is
5W5o head switching signal for SP to switch
' , (8Ws.

and has a phase difference of α-90°).

Since head A' or B' moves by track pitch P8 in the tape running direction during one field, head A' or B' moves by track pitch P8 in the tape running direction during one field.
If the f-component of the pilot signal is detected at ' or B', as shown in Figure 3 (■) of the fa-acid component, when reproducing the SP recording pattern, a waveform having a maximum value in a 4-field cycle is synchronized with 5W30. (Since the recording track width is twice that of LP, the f and component are also multiplied by so).

However, as shown in ■, when the pattern changes to the LP recording pattern in the middle, the f component becomes a waveform with a maximum value in two field periods, but the minimum value does not become low enough, so f
The S/N of the - component is extremely poor, and it is almost impossible to determine the recording tape speed from this information. In other words, the minimum value is shown when the wide A' or B' head is scanning the A track on which fl is recorded, but since the pilot frequency is relatively low, the track A on both sides of the A' or B' head
This is because f is picked up from 1 and A1.

In order to eliminate the above-mentioned disadvantages, in the present invention, as shown in the block diagram of an embodiment of the present invention in FIG. The f-component of the pilot signal is detected at B, and the recording tape speed is determined based on that information. The fourth below
The specific operation will be explained based on the block diagram in the figure and the signal waveform diagram of each part in FIG.

In Fig. 4, 1 is the rotary head drum, which is the same as in Fig. 1, 2 is a magnetic tape, and A, B, A', B' are the aforementioned 4
The drum motor 4 detects the rotational phase of the drum, and the servo circuit 5 sends an LP head switching signal SW, 3.
0 is a tack head, 6 is a capstan motor, 7 is a frequency generator (hereinafter abbreviated as FG, its output is CFG, and its frequency is fCFG); in this example, the capstan shaft is the capstan motor. 6 is directly driven, but in the case of belt drive etc., it may be installed on either the cab's tongue shaft or the motor shaft. 8.9 is a preamplifier for amplifying the video head output for LP and SP, respectively; 10.11 is a switch that is switched by the head switching signal for LP and SP, respectively; 12 is SW 3
Delay circuit that creates 5W30' by delaying from 0, 13 is f, m j) return frequency detection circuit, 14 is switch 1
The first output pass filter selects and passes the fl component from the output of 0, and its output is sent to the rectifier 15.
The fs acid component, which is the amplitude change component of f-, is created through

16 is a second filter having a predetermined bandwidth, and 17 is a zero cross detector whose output P has a frequency fP.
represents the repetition frequency of the amplitude change of f, 18 is f
19 is a discrimination circuit that discriminates the recording tape speed based on the ratio of cFG and fP and creates outputs SP and LP (SP# becomes "H"); 19 is switched by the SP and LP signals; When SP and LP are "L" (with the switch positions as shown in the figure), the outputs from LP heads A and B are used as video outputs, and when SP and LP are "H", SP heads A',
This is a switch that outputs the output from B' as a video output.

Due to the above configuration, pilots can always be obtained from the LP heads A and B. There is no problem with determining when an LP is being played as explained in Figure 2, so S
The P replay determining operation will be explained with reference to FIG. The symbols for each part are the same as in FIGS. 2 and 3.

Because heads A, B, A', and B' have a position difference of 90 degrees, they move by track pitch ps in the tape running direction during one field, so head person or B is 8W3.
The output pilot of the switch 10 is input to the fl repetition frequency detection circuit 13.

At this time, since SP and LP are "H" (SP mode), the video output is set to SP heads A' and B' by switch 19.
You can now get the output from . The point to note here is that heads A' and B' are delayed by 180°+α-270° from heads A and B with respect to the rotational direction as shown in FIG. Delay 7' (
By switching the A' and B' heads with the switch 11 in 8W30', not only the pilot but also the video signal can be made continuous in time.

The fl component is extracted from the output pilot of the switch 10 by the BPF 14 and rectified by the rectifier 15.
The amplitude change component f can be detected as shown in FIG.

That is, the f component is as shown by V in waveform (4) in FIG.
When reproducing the SP recording pattern, the waveform becomes synchronized with 5Wso and has a maximum value at a period of 4 fields, and when reproducing the problematic LP recording pattern, as shown in ■, the waveform for J LP is different from that shown in Figure 6 ■. Since reproduction is performed using the narrow heads A and B, a good waveform is obtained in which the fs acid component has a maximum value in two field periods and a minimum value of 87N, which is so zero.

Therefore, by changing the f1 configuration to the BPF 16 and the zero-cross detector 17, it is possible to obtain an output P having a frequency of fP.

On the other hand, the playback tape speed is the frequency fc of the frequency generator CFG.
Corresponds to FG on a one-to-one basis. In the example, tc during SP playback
va is 240 Hz s fcPG when playing LP is 12
It is 0Hz. Also, the repetition frequency f of the amplitude change of fl
p is 15H2 (4 field period) when the SP pattern is reproduced at the SP tape speed, as shown by waveform P in Figure 5.
When the LP pattern is reproduced, it is 3011Z (2 field period). Therefore, the ratio of fcFG and fP is R=fcFG/
fP is R=16 for sp pattern, R=a for LP pattern
becomes.

In general, the tape speed is twice that of LP (fcpG=120rL)
fp when playing an LP pattern at (Hz) ) =
154L (H2), 'p when playing SP pattern
= '2 rL (Hz), so the ratio R is 几 = 16 for the SP pattern and R = s for the LP pattern, regardless of the playback speed.
It becomes constant.

Therefore, during playback, CFG and P are input to the discrimination circuit 18,
When the ratio R of fcFG and fP is larger than 12, it is determined as S) and SP and LP are set to "H", and when the ratio R is smaller than 12, it is determined to be LP and SP and LP are set to "L", and the switch 19 And the reproduction mode of the servo circuit 5 is automatically switched.

Next, in order to improve the detection 8/N of the pilot signal f-, a frequency conversion method can be used as the repetition frequency detection circuit 16. This will be explained using the block diagram of FIG. In FIG. 6, 21 is a local pilot f4 generator, 20 is a mixer, and 22 is a bandpass filter for extracting the fH acid component.

The regenerated pilot signal is mixed with the local pilot f4 in the mixer 20 and frequency-converted, and only the component whose difference frequency component between the pilot and f4 is fH, that is, the component f, is detected (fa f4=10.5 fH- 9,
5fH=fH). After fl is converted into low-frequency fH in this way, the BPF'22 removes the fH component, and the rectified fH and therefore the amplitude change component of fs is shaped by the BPF 16 and zero-cross detector 17, and the fH is converted into fH. An output P having a frequency of .

The above has been explained using an example in which the LP head and the SP head are α=90', but as shown in Fig. 7, LP heads A and B
It is clear that the present invention can be applied in exactly the same way even when SP heads A' and B' are extremely close together (α is extremely small, for example, α = 1.03° (equivalent to 1.5H)). be. In this example, head A and head B' or head A'
It is configured with a so-called double azimuth head in which the head and head B are mounted on one helad base (the head chips may be separate or the same), and the head width is 15 μm for heads A and B, and 21 μm for heads A' and B'. By appropriately selecting the video signal reproduction head during reproduction (especially at variable speed), the head for reproducing video signals is not limited to LP or SP, and the optimum head can be freely combined according to the reproduction mode. Furthermore, guard panless recording is possible in both modes. Even in this case, the feature of the present invention is that the narrow A and B heads are always used to detect the pilot signal for determining the recording tape speed.

Although the above is a case where there are two types of recording tape speeds, the same can be considered for three or more types of recording tape speeds.

Next, a specific example of the discrimination circuit 18 will be explained based on the block diagram in FIG. 8 and the signal waveform diagram of each part in FIG. 9.

In FIG. 8, 31 is a four-stage counter, 62 is a delay circuit, 53 and 34 are rise detection circuits, 35 is an AND gate, 66 is an SR flip-flop, and 37 is a D flip-flop.

M8 diagram is 几 = 5P when fcpa/fp is larger than 12
LP is set to H''. First, the output signal P of the zero cross detector is delayed a little by the delay circuit 32, and then the counter 31 and the SR flip-flop 66 are reset by the rise of the output signal P. Count the period CFQ.When focusing on one frequency fs, when it is an LP pattern, the count value of the counter 61 (matching R) is 8, and SET
is not “H”, QOUT is also “L”, SP, LP
The output is also "L" (LP mode) (the case on the left side of Figure 9).

Next, when the playback changes to the SP pattern (case on the right), the count value becomes 16! When 0, Q, ,Q are both "H" (count value = 12), IT becomes "H"#)QOU
T becomes H”.

Then, this Q OUT is latched by the D flip-flop 37 at the rising edge (φ+) of the signal P generated by the detection circuit 34, and 5PLP is set to H' to determine the SP mode, and the switch 19 and the servo circuit 5 are regenerated. The mode is automatically switched.

〔Effect of the invention〕

As explained above, according to the present invention, even if the system does not require a CTL signal and performs tracking using a pilot signal, and in which several types of heads are appropriately selected depending on the recording/reproducing mode, the system is always stable. It becomes possible to determine the recording tape speed and automatically switch to a predetermined mode.

[Brief explanation of drawings]

FIG. 1 is a plan view of a rotating head drum used in an embodiment of the present invention, and FIGS. 2 and 6 are a plan view of an LP head and an S
FIG. 4 is a block diagram of an automatic recording tape speed determination device for a VTR according to an embodiment of the present invention, and FIG. 5 is a diagram for explaining FIG. 4. Tenip pattern and signal waveform diagram of each part, 6th
This figure is a block diagram of another embodiment, FIG. 7 is a plan view illustrating another head configuration, and FIGS. 8 and 9 are block diagrams of a discrimination circuit and signal waveform diagrams of various parts, respectively. A, B, A', B electric head, 8.9... preamplifier,
10.11.19...Switch, 12...Delay circuit,
13...f, repetition frequency detection circuit, 14.16.
22 ・Band pass filter, 15 ・ Rectifier, 17 ・
-Zero cross detector, 18.Discrimination circuit, 31...Counter, 62.Delay circuit, 36.54...Start-up detector, 66...SR+7 lip-flop, 37...D flip 70 tube. Figure 3 JiLff Figure 4 / $S Closed m - "(S Bi'"]] - Figure 2 Figure 7

Claims (1)

[Claims] 1. Means for recording at several types of recording tape speeds, means for performing servo tracking of pilot signals of several types of frequencies whose weights are recorded in advance on a video track, and a means for performing servo tracking on a rotating head drum at 180° intervals. In a rotary head helical scan type magnetic recording and reproducing device having a first pair of heads with different azimuths, the rotary head drum has a first pair of heads at a position shifted by a predetermined angle from the first pair of heads.
A second pair of heads with different azimuths are installed at 800° intervals, and the head width of the second pair of heads is set to be narrower than that of the first pair of heads.
1. An automatic recording tape speed determination device for a magnetic recording/reproducing apparatus, comprising means for always detecting a reproduction pilot signal obtained from a pair of heads, and means for determining a recording tape speed from information of the reproduction pilot signal. 2. A patent characterized in that the apparatus includes a delay means for delaying a head switching signal for switching the second pair of heads by a predetermined amount, and a means for switching the first pair of heads using the delayed head switching signal. An automatic recording tape speed determination device for a magnetic recording/reproducing device according to claim 1. 3. During regeneration, determine the ratio of the frequency of the signal obtained from the frequency generator attached to the cab's tongue shaft or the capstan motor shaft to the repetition frequency of the amplitude change of the regenerated pilot signal obtained from the second pair of heads. 3. An automatic recording tape speed determination device for a magnetic recording/reproducing apparatus according to claim 1 or 2, further comprising means for determining the recording tape speed based on the recording tape speed.