JPS6282533A - Information signal recording device - Google Patents

Abstract

PURPOSE:To prevent the miserasion of the recorded information by recording the detecting signal for prevention of miserasion together with the information signal and detecting said detecting signal contained in the reproduction signal of a rotary erasion head FEH in a record mode. CONSTITUTION:The detection signal for prevention of miserasion is recorded at the position set immediately after a head rushes to a tape. The signal which is reproduced by a FEH34 via the side L of a switch 37 is amplified by an amplifier 39 and the detection signal for miserasion is separation for wave detection through a BPF and detected. This detection signal is compared with the prescribed voltage 44 by a comparator 41. Thus the detection signal for prevention of miserasion is detected by the FEH34. Then a signal of a high level is supplied to the D input of a flip-flop FF42. The Q output (h) of the FF42 is set at a high level and the output of an AND gate 50 is changed to a low level regardless of the output of an exclusive logic circuit 49. Thus the supply of the erasion signal is inhibited to the FEH34. While the Q output of an FF52 is set at a low level after the output of the gate 50 is changed to a low level. Then a switch 35 is connected to the L side to inhibit a recording action.

Description

[Detailed Description of the Invention] [Field of Industrial Application] This invention relates to a recording rotary head and a recording medium that is installed in advance of the recording rotary head for the main purpose of erasing already recorded information signals. Rotating erase head to trace (
The present invention relates to an information signal recording device equipped with an FEH (hereinafter referred to as FEH).

[Conventional technology]

Conventionally, as this type of recording device, there is a helical scan type video tape recorder (hereinafter referred to as VTR) that performs tracking control using a four-frequency method, for example.
This will be explained below using TR as an example.

In a VTR, the FEH traces the tape in advance of the rotating recording head, and during recording, an erasing current continues to flow through the FEH to erase signals that have already been recorded.

[The interlayer point that the invention attempts to solve]

With conventional devices such as those mentioned above, when you consciously want to leave a part of the signal that has already been recorded, you have to cancel the recording mode, pass the part you want to keep, and then set the recording mode again. must be done manually. Furthermore, there is a problem that so-called erroneous erasing may occur due to this operation.

The present invention has been made in order to solve such problems, and it is an object of the present invention to provide an information signal recording device equipped with an accidental erasure prevention function that automatically prohibits erasure and recording of information signals that are desired to be retained. purpose.

[Means for solving problems]

The information signal recording device according to the present invention includes means for recording a detection signal for preventing erroneous erasure together with the information signal, means for detecting the detection signal included in a reproduced signal of FEH at the time of recording, and The system is equipped with means for prohibiting recording based on the following.

[For production]

By configuring as described above, it is possible to add a function to prevent erroneous erasure without providing a special recording area or a special head for preventing erroneous erasure. A method of creating a tracking control signal using the four-frequency method will be briefly described. FIG. 5 is a diagram showing a recording magnetization locus of a VTR that performs tracking using a four-frequency system, and FIG. 6 is a block diagram showing a main part of a reproducing circuit for obtaining a tracking error signal.

In FIG. 3, reference numeral 1 indicates a magnetic tape, and arrow 2 indicates the direction in which the magnetic tape 1 is transported.

As-Bt*Ax, Bx, . . . are recording tracks recorded by the A head and the B head, each having a predetermined azimuth angle with respect to each other, and the arrow 3 indicates the scanning direction of the heads. Recording track 4 contains 4 along with video signals.
Different types of pilot signals with different frequencies (indicated by f1 to f4) are used for each field (fHJ, that is, for each track)
are recorded sequentially.

The recording order of pilot signals is the order shown in Figure 3,
For example, track A1 has fl, for example 102.5KHz.
medium 5.5 fus) Rack B1 has fl, for example 11
A pilot signal of f8 (for example, 10.5 fH at 165.2 KHz) is superimposed on the video signal in rack A2 (7.5 fH at 8.9 KHz), and a pilot signal at f4 (for example, 9.5 fH at 148.7 KHz) is recorded at rack B2. ing. (
Note that fH indicates the frequency of the horizontal synchronizing signal) The frequency difference of the pilot signals between adjacent recording tracks is <, fH or 3fn as shown in the figure. When the head scans track A i (i = 1.2.3...), the frequency difference with the pilot signal of the adjacent track on the right side of the figure is always fH, and the frequency difference with that on the left side is always 3fH. be. Also, the head is Bl (i=1.2
．． 3...) When scanning a track, the frequency difference with the adjacent track on the right side is always 3fH, and the frequency difference with the adjacent track on the left side is always fH.

Incidentally, since the pilot signals f1 to f4 are all comparatively low frequency signals, even in azimuth recording, the head can reproduce the pilot signals from adjacent tracks other than the main scanning track as crosstalk. In other words, the pilot signal detected when the head is main-scanning track A2 is a composite signal containing frequency components f4, fl, and f3, and the center of the head's trace locus is precisely aligned with the center line of the main-scanning track. If they match (on-track), the adjacent track's pilot signal f2. f4 is at the same level,
If the head slightly deviates from track A2 toward B2, f4 is larger than f, and the head is on track A! If the signal shifts slightly to the Bl side without being distorted, fl is reproduced to be larger than f4.

Therefore, the difference signal between the pilot signal on the main scanning track and each pilot signal on both adjacent tracks, that is, fH and 3fH
By separating and extracting the signals and comparing the levels of both difference signals, the direction and amount of deviation of the head from the main scanning trunk can be determined.

FIG. 4 is a circuit block diagram of such a four-frequency system. In the figure, a reproduced signal in which a video signal and a pilot signal are superimposed is input from terminal 5, and a low-pass filter (LPF) is input.
6, only the pilot signal component is separated. A multiplier 8 multiplies the pilot signal component by the local pilot signal generated by the generation circuit 7. The local pilot signal is a signal having the same frequency as the pilot signal recorded on the main scanning track, and as described in the explanation in FIG. 3, when track A2 is the main scanning track, the output of the LPF 6 is f,... f4. It includes an f3 configuration and the frequency of the local pilot signal is f3. Therefore, the output of multiplier 8 is f2. f4. f.

A signal having a frequency of the sum and difference of and f3 is output.

The band pass filter (BPF) 9 is a circuit that extracts only fHq and BPFIO signals from the sum and difference signals, and the output is sent to the next stage detection circuits 11 and 12.
The signals are detected and rectified by the following.

Next, the fH signal component and the 3fH signal component are supplied to a level comparison circuit 13, which outputs a signal corresponding to the level difference between them. That is, when the reproduction level of the fH signal is higher than the reproduction level of the 3fu signal, a positive potential corresponding to the level difference is extracted, and in the opposite case, a negative potential is extracted. As a result, a signal containing information on the amount and direction of the head's track deviation is output, so this can be used as a tracking error signal.

Next, as explained in FIG. 3, the relationship between track Ai and track Bi with respect to the head deviation direction tracking error signal will be opposite to each other, so the inverting amplifier 14 is further passed after the level comparator 13. It is necessary to provide a switching circuit 16 that selectively outputs those that pass and those that do not pass, using a head switching signal 15.

A VTR that employs such a tracking method and is equipped with an FEH will be described with reference to FIGS. 5, 6, and 7.

In FIG. 5, recording and reproducing heads A and B are arranged 180 degrees opposite each other on a rotating drum, and the FEH is arranged between these pair of recording and reproducing heads A and B in the direction of rotation from head A. It is provided 90° behind and 90° ahead of head B in the rotational direction. The head widths and relative mounting heights of these heads A, B, and FEH are shown in FIG. That is, heads A and B each have a width slightly wider than the track width Tw, that is, wA,
WB, and FEH has a width that is more than twice the track width Tw, that is, WFX. During recording, B0→Af-+B due to heads A and B having different azimuth angles.
! →A2→B2→A, →B, →A4, the tracks are formed in sequence, and the pilot signal fl as explained in FIG. 3 is generated.

f2. f,, f, are recorded together with the information signal.

FIG. 6 shows the timing when head A has completed the recording trace of track A4 and head B is about to record trace the next track, track B4. In this state, FEH is head A.
, B, and is given an erasing signal to erase the track that is about to be recorded by heads A and B in advance. For that reason, FE
The relative height of the FEH is such that the left end of the FEH is located to the right of the width WA of the track A4 so as not to affect the already recorded track A4.

FIG. 7 is a diagram showing the trace state of each head on the tape during reproduction. FIG. 7 shows a situation where the head A is accurately tracing the track A where the pilot signal f1 is recorded (just tracking).

FIG. 1 is a block diagram showing a schematic configuration of a VTR as an embodiment of the present invention, and FIG. 2 is a timing chart showing waveforms at the numbered part in the first drawing.

Figure 2 (a) shows the 3
0Hz head switching signal (hereinafter referred to as PG) - (b) is the output signal of the mono multi 27, (C) is the terminal 29 in Figure 1
(The mountain indicates the signal output from the AND gate 57.

In Figure 1, 21.22 is head 'A' in Figure 5,
The recording and reproducing heads 23, which have different azimuth amounts corresponding to B and are arranged 180 degrees opposite each other, are connected by 30PG (Fig. 2(a)) supplied from the terminal 28.
A changeover switch 27 for selecting the head 21 or 22 tracing the recording medium is a monomulti switch triggered by the rising edge of 30PG, and generates a timing signal as shown in FIG. 2(b).

25 is a circuit that generates a pilot signal for tracking control as described above; 26 is a detection signal generator for preventing erroneous erasure;
24 is a switch, and 29 is a terminal to which a high level signal is applied in response to a manual operation by the user when it is desired to prevent erroneous erasure.

In the circuit configured as described above, when a signal for preventing erroneous erasure is applied from the terminal 29, the 1-AND gate 27 outputs a pulse as shown in FIG. 2 (Φ).
Figure 2 1. The switch circuit 24 supplies the output of the detection signal generator 26 to the mixer 32 only when the pulse shown in FIG. A detection signal generated by 26 for preventing erroneous erasure is provided. The video signal input from the terminal 30 at this time is processed by the recording signal processing circuit 36, mixed with the tracking pilot signal generated by the pilot signal generation circuit 25 by the mixer 31, and further supplied to the mixer 32. ing. The above operation makes it possible to record a detection signal for preventing erroneous erasure at the position immediately after the head 1 enters the tape.

Next, a description will be given of the operation of detecting an already recorded signal for preventing erroneous erasure and preventing erroneous erasure.

The 90' phase shift circuit 43 shifts the phase of 30PG(a) by 90°,
A signal that is at a high level during the period when the FEH 34 rotating with the phase shown in Fig. 5 traces the tape (Fig. 2 (e)
) occurs. Output of 90° phase shift circuit 43 (e)
is supplied to the monomulti 47, and the second signal synchronized with the rising edge of the first signal [1U(f)] is obtained. At this time, the output of the exclusive OR circuit (EX-OR) 49 is FEH3
4 is at a high level during the period when the tape is traced, except during the period when the recording position of the detection signal for preventing erroneous erasure is traced.

The output of this EX-OR 49 controls the switch 37 via the AND gate 46. That is, when the output of the AND gate 46 is at a low level, the switch 37 is connected to the L side, and it is always determined by the FEH3 whether or not the detection signal for preventing erroneous erasure is recorded.
Detected using 4.

At this time, the frequency of the detection signal for preventing erroneous erasure is not affected by azimuth recording and is a sufficiently low frequency signal to be reproduced in the gap of FE'f(0). The signal regenerated through the amplifier 39 is amplified, and the BPF separates the false erasure detection signal and performs detection.This detection output is sent to the comparator 4.
1 and is compared with a predetermined voltage 44. This allows the FBI (
34 to prevent erroneous erasure 1 When the detection signal is detected, 7 lip 70 lip (FF) 11 42
A high level signal is input to the D input of.

The monomulti 48 receives the entire output (f) of the monomulti 47, and generates a pulse approximately at the center of the period during which the FEH 34 traces the recording position of the detection signal for preventing erroneous erasure. (Second [
ffl(g)) This pulse (ω is the CK of FF42)
The Q output of the FF 42 is, for example, as shown in FIG. 2()I).

Therefore, when the detection signal for preventing erroneous erasure is detected, the FF42
The Q output of the signal becomes high level, and the output of AND gate 50 changes to low level. Along with this, the output of AND gate 46 also becomes low level regardless of the output of EX-OR49, and an erase signal is supplied to FEH34. (timing shown at tl in Figure 2) Also, after the output of the AND gate 50 changes to low level, the next 30P
At the falling edge of C, the Q output of the FF 52 (shown as second m(j)) becomes low level, and the switch 35 is connected to the L side, inhibiting recording. (Timing shown at t2 in FIG. 2) The difference between the erasing operation prohibition timing and the recording operation prohibition timing is 0.5 based on the head arrangement shown in FIGS. 5 to 7.
It is considered as a field period.

Thereafter, the signals reproduced from the heads 21 and 22 are supplied to the reproduced signal processing circuit 45 and the tracking control circuit 51, and the VTR performs the same operation as during reproduction.

When the erroneous erasure prevention detection signal is no longer detected during the reproducing operation as described above, the Q output of the FF 42 changes to a low level. Along with this, the output of the AND gate 50 changes to a high level. , AND gate 46 is EX-O
The output of R49 is gated and the erase operation is restarted. (timing indicated by t in Figure 2) After a further 0.5 field period, the Q output (j) of the FF 52 changes to high level and recording is restarted. (Timing shown at t4 in Figure 2) Note that a high level signal is supplied to the terminal 53 from an operation unit (not shown) when a recording command is issued, and a low level signal when a playback command is issued. There is. Therefore, the Q output of the FF 52 is at a low level regardless of the Q output of the FF 42 while the reproduction command is issued, and the VTR performs the reproduction operation.

According to the above-described configuration, it is now possible to prevent erroneous erasure without providing a special head and without providing a special area for recording the erroneous erasure prevention signal. Furthermore, it is possible to prevent erroneous erasure on a recording track basis, making it extremely easy to use.

〔Effect of the invention〕

As explained above, the present invention has the effect of preventing erroneous erasure without providing a special head or a special recording area.

[Brief explanation of drawings]

Fig. 1 is a block diagram showing a schematic configuration of a VTR as an embodiment of the present invention, Fig. 2 is a timing chart of the part numbered in Fig. 1, and Fig. 3 is a VTR that performs tracking using a four-frequency system.
FIG. 4 is a block diagram showing the main parts of a reproducing circuit for obtaining a tracking error signal; FIG. 5 is a diagram showing an example of the arrangement of the FEH and recording/reproducing head; FIG. 6 is a diagram showing the trace locus of each head on the tape during recording, and FIG. 7 is a diagram showing the trace locus of each head on the tape during reproduction. In the figure, 21.22 is a recording/reproducing head, 23.2
4 is a switch, 26 is a detection signal generator, 27 is a mono multivibrator, and 34 is FEH. 35 is a switch, 36 is a recording signal processing circuit, 37 is a switch, 38 is an erasure signal generation circuit, 39 is an amplifier 1111,
40 Huband Pass Filter (BPF')! 5 and a detection circuit, 41 a comparator, 42 a flip 70 tube (FF),
43 is a 90° phase shift circuit, 44 is a reference level, 4
5 is a reproduction signal processing circuit.

Claims (1)

[Claims] In an information signal recording device that is provided with a rotary recording head and a rotary erasing head that traces a recording medium in advance of the recording rotary head with the main purpose of erasing already recorded information signals, errors may occur. means for recording a detection signal for erasure prevention together with an information signal; means for detecting the detection signal included in a reproduction signal of the rotary erasing head during recording; and means for prohibiting recording based on the detection means. An information signal recording device comprising: