JPS6142704A - Magnetic video recording and reproducing device - Google Patents

Abstract

PURPOSE:To decide on the kind of a video tape automatically without increasing the number of components on a deck of VTR by detecting whether a sense signal is present or not by utilizing the difference in coercive force between different kinds of video tapes. CONSTITUTION:The FEON/OFF signal outputted by a system controller 16 is FEOFF and an audio signal erasing head 10 is off in reproducing operation. An R/P signal, on the other hand, is in reproducing mode and a sense signal is reproduced by a reproducing head 12. The signal is inputted to a detecting circuit 25 through a reproducing amplifier 24 unless the sense signal is erased. When an audio reproducing head 12 turns on an S/H signal at the timing of the reproduction of a sense signal area 15, a reproducing signal level is detected through the BPF and rectifying circuit of the sense signal detecting circuit 25. When this level exceeds some level, DET.SIG as the output of the sense signal detecting circuit 25, for example, goes down to L and a controller 16 judges that the sense signal is not erased, thereby deciding on a tape with high coercive force.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to a magnetic recording/reproducing device (hereinafter abbreviated as VTR), and particularly to a VTR that can automatically determine the type of videotape.

[Prior art] Conventionally, VTRs have the characteristics of video tape (coercive force, etc.)
Manufactured to specifications based on the type of product. Conversely, videotape improvements have been made under the condition of using existing VTRs. Therefore, conventional VTRs were not equipped with a device for determining the type of tape, and there was no need for one.

However, the use of video tapes with high coercive force has begun to be considered in order to improve the image quality, especially the resolution. Therefore, when a conventional videotape and a high-resolution videotape are used in the same VTR, a new need has arisen to automatically distinguish between the tapes and to optimize recording and playback characteristics.

Generally, the type of videotape was determined by drilling a hole in the videotape cassette case and detecting it with a switch, etc., but this conventional method was also sufficient if it was the first time the standard was created. However, if it is added after the standard has been established, there are drawbacks such as not only the addition of parts but also interference with conventional VTR decks.

[Summary of the Invention] This invention has been made to solve the above-mentioned conventional drawbacks, and detects the presence or absence of a sense signal by using the difference in coercive force between different types of video tapes. It is an object of the present invention to provide a magnetic recording and reproducing device that can automatically determine the type of videotape without increasing the number of parts.

[Embodiments of the invention] Embodiments of the present invention will be described below with reference to the drawings.

Figure 1 is a block diagram of a helical scanning VTR. In Figure 0, which shows the recording operation, (1) is the video tape, (2) is the capstan shaft, (3) is the capstan motor, and (4) is the video tape. is a pinch roller, (5) is an unnecessary signal already recorded on the videotape (1), and (8) is a pinch roller.
) is a full-width erase head, (7) is a rotating head drum, (8
) is the video head, (9) is the video track recorded on the videotape (1) by the video head (8), (
10) are audio signal cancellation heads, (ILa), (H
b) is an audio signal before being erased and a newly recorded audio signal, (12) is an audio signal recording/reproducing head, (13) is a control signal recording/reproducing head, and (14) is a control signal.

In normal recording, the videotape (1) is fed at a constant speed in the direction of the arrow in the figure (referred to as the forward direction) by the rotation of the capstan shaft (2).
) has already been recorded on the full-width erase head (6).
) and the video signal to be newly recorded is recorded as a video track (8) on the video tape (1) by a video head (8). Further, the already recorded unnecessary signal (lla) is erased by the audio signal erasing head (lO), and a new audio signal (llb) is erased by the audio signal recording/reproducing head (12).
is recorded. Further, a control signal (14) is recorded by a control signal recording/reproducing head (13).

Now, the coercive force of the conventional videotape is Hct=600 (
Oe), and this is tape I.

On the other hand, the coercive force of high resolution video tape is Hc2w12
00 (Oe), and this is called tape ■. An example of the magnetization curves of these tapes I and II is shown in FIG. As can be seen from Fig. 2, when tape 1 is saturated and recorded, in order to erase the recorded signal, it is only necessary to generate an alternating current magnetic field greater than Hat. I can say that.

Now, consider an alternating current magnetic field Hc3 (±Hc3) with a magnitude such that Hcl<Hc3<Hc2. This Hc3 is set to a size sufficient to erase the signal recorded on the tape I, but insufficient to erase the signal recorded on the tape ■. Under these conditions, a 1KHz signal was recorded on tape E and tape II.

Next, assuming that tape 1 is erased by an alternating magnetic field called Hc3 and then reproduced, no reproduction output will be obtained from tape 1, and a 1 kHz signal will be reproduced from tape ■. It becomes possible to identify the tape.

Usually, an audio signal erasing head (10), an audio signal recording/reproducing head (12), a control signal! The recording/reproducing head (13) is arranged as shown in Figure 3, and assuming the distance between the audio signal erasing head (10) and the audio signal recording/reproducing head (12) is 1, the tape feeding speed is the same as that of the VH3 system. 33.35mm in standard mode
/sec, so if we assume that 1 = 8 mm, the distance will be approximately 0.24 sec.

FIG. 4 shows an example of a tape discrimination operation according to the present invention, and FIG. 5 shows an example of a circuit for discriminating the type of tape.

In FIG. 4, (1) is a video tape, (10) is an audio signal erasing head, (12) is an audio signal recording/reproducing head, and (15) is a sense signal area where a sense signal is recorded. Also, in Figure 5, (1G)
is the system controller, (1?) is the audio signal cancellation signal generation oscillator (hereinafter referred to as 05CI),
(1B) is an amplifier that amplifies the signal of OS CI (17)
Variable rate amplifier, (19) is audio circuit, (20)
is a sense signal generation oscillator (hereinafter referred to as OSCN)
, (21) is the output (REC
AUD I O) and OS CII (2(1) output (
SENS 5IG) switch, (22)
(23) is an audio signal recording amplifier that amplifies an audio signal (RECAUDIO) or a sense signal (SENS 5IG), and (23) is an audio signal recording amplifier.

A switch for switching reproduction, (24) an audio signal reproduction amplifier, and (25) a sense signal detection circuit.

Next, the tape discrimination operation will be explained with reference to FIGS. 4 and 5. In FIG. 4, the video tape (1) is first set at the initial set position as shown in (A). next.

The recording operation of the sense signal shown in CB) begins, and the videotape (1) is fed at a constant speed in the direction of the arrow (forward direction).

At this time, in FIG. 5, the system controller (1
The TAPEI/n selection signal output from B) becomes a signal for selecting tape ■, and the switch SWI of the amplifier (18)
turns OFF. Also, FE 0N10FF! The number is F
E becomes ON. Therefore, the gain of the amplifier (18) is R2/R1, and the audio signal cancellation head (10
) becomes the level Hc4, and the previously recorded unnecessary signal is erased. On the other hand, the 5ENS 0N10FF signal output from the system controller (1B) becomes 5ENS ON, and the R/P signal becomes R (record).

5ENS SI (,@) is amplified by the audio signal recording amplifier (22) via the switch (21), and is saturated recorded by the audio signal recording/reproducing head (12) via the switch (23).

Next, the erasing operation shown in FIG. 4(C) begins, and the video tape (1) is fed at a constant speed in the direction of the arrow (reverse direction). At this time, in Fig. 5, the system controller (
The TAPE I/■ selection signal output from the amplifier (1B) becomes the TAPE I/■ selection signal, and the switch SWI of the amplifier (18) is turned ON. Therefore, the gain of the amplifier (1B) is (R2It
R3) /R1, and the audio signal cancellation head (1
0) is at the level of Hc3. Further, at this time, the R/P signal output from the system controller (16) is at P (playback), and no recording is performed by the audio signal recording/playback head (12).

Next, the reproduction (discrimination) operation shown in FIG. 4(D) begins,
The videotape (1) is fed at a constant speed in the direction of the arrow (forward direction). At this time, in FIG. 5, the FEON10FF signal, which is the output of the system controller (16), becomes FE OFF, and the audio signal erasing head (
10) is in the OFF state.

On the other hand, the R/P signal is P (reproduction), and the sense signal is reproduced by the audio signal recording/reproducing head (12). If the sense signal is not erased, it is input to the sense signal detection circuit (25) via the switch (23) and the audio signal reproduction amplifier (24). The audio signal recording/reproducing head (12) is connected to the sense signal area (15).
) When the S/H signal is turned ON in accordance with the timing of reproducing the signal, the level of the reproduced signal is detected by the BPF (band pass filter) and rectifier circuit of the sense signal detection circuit (25). If this reproduction signal level is higher than a certain im (for example, E2), for example, the sense signal detection circuit (
25) outputs of 5ENS, DET, and SIG signals are r
I, J, and the system controller (1B) determines that the sense signal has not been erased. That is, it is determined that the tape is tape ■.

The distance that videotape [1] travels during the above tape type discrimination operation is 3X (11+12).

Here, if JL1=12=8mm, the traveling distance is 48mm. Assuming the standard mode of the VH5 standard, the tape running speed is 33.35 mm/sec, which corresponds to about 1.5 sec. In addition.

During this discrimination operation, the capstan shaft (2) or the capstan motor (3) starts and stops, so a total time of about 2 seconds is required. That is, about 2
The type of tape can be determined by sec. Also, the area in which sense signals are recorded for discrimination is approximately 0.5 seconds.
ec (about 1.5 seconds in 3x mode), and there is a recording start portion, so there is no problem when using a VTR.

In the above embodiment, the lKH2 signal was used as the sense signal, but signals of other frequencies may also be used.Also, although an example was shown in which the sense signal was erased using the audio signal erasing head (10) before recording, If we simply focus on whether or not the recorded signal has been erased, erasing is not necessarily necessary.

Therefore, recording, erasing, and reproducing sense signals may be performed only by the audio signal recording/reproducing head (12).
In this case, the time required for determination can be reduced compared to the above case. Furthermore, although two types of video tapes are shown, three or more types may be used, and the distance between the audio signal erasing head (10) and the audio signal recording/reproducing head (12).

Although the length of the sense signal region has been described as 8I1, it goes without saying that other values may be used.

C. Effects of the Invention As described above, according to the magnetic recording and reproducing apparatus according to the present invention, the type of video tape can be determined by detecting the presence or absence of a sense signal using the difference in coercive force between different types of video tapes. Since the discrimination is made automatically, the conventional audio signal erasing head and audio signal recording/playback head can be used as is, and the level of the erasing signal can be simply lowered without changing the VTR deck, especially the tape running system. It has the advantage that the type of videotape can be easily determined by simply adding a sense signal detection circuit and a sense signal generator by making it possible to switch between tapes with high coercive force and tapes with high coercive force.

[Brief explanation of drawings]

Figure 1 is a configuration diagram of a helical scanning VTR, Figure 2 is a diagram showing an example of a magnetization curve of a video tape, and Figure 3 is the arrangement of an audio signal erasing head, an audio signal recording/playback head, and a control signal recording/playback head. FIG. 4 is a diagram for explaining an example of tape discrimination operation in this yAIIJl, and FIG. 5 is a circuit diagram for discriminating the type of tape. (1)...Video tape, (B)...Full width erase head, (10)...Audio signal erase head, (12
)...Audio signal recording/playback head, (15)...
- Sense signal area, (1B)...System controller, (18)...Amplifier, (25)...Sense signal detection circuit. In addition, in FIG. 1, the same reference numerals indicate the same or corresponding parts.

Claims (1)

[Claims] (1) Video signals and audio signals can be recorded and played back separately, and only audio signals can be recorded and played back.
In a magnetic recording and reproducing device that can be erased and that can use two or more types of video tapes with different coercive forces,
A means for saturating and recording a frequency sense signal in the audio signal recording portion of a videotape, and one type of level that is erasable for some types of videotape and non-erasable for other types of videotape. Audio signal erasing means capable of generating erasing signals at a level erasable for all types of video tapes, and determining the type of video tape by detecting the presence or absence of the sense signal. 1. A magnetic recording and reproducing device characterized by comprising means for.