JPH0564514B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a rotary head type magnetic recording/reproducing device having a plurality of rotary heads. In particular, during reproduction, the one of the two rotary heads with the highest reproduction signal level The present invention is characterized by a selection means that sequentially selects the output of one rotary head and uses it as a reproduction signal.

Conventional configuration and its problems Recent rotating head type magnetic recording/reproducing devices (VTR)
In order to improve the recording density, the two rotating magnetic heads A and B are configured to have different azimuth angles, as shown in FIG.

In addition, in order to obtain a better reproduction signal during special reproduction in which the magnetic head scans across a plurality of tracks, such as during fast-forward reproduction or slow-motion reproduction, a magnetic head is placed oppositely in the vicinity of the rotating magnetic heads A and B, respectively. Azimuth auxiliary heads B' and A' are provided, and during reproduction, one of the heads A, B', B and A' having a high reproduction signal level is sequentially selected and extracted.

FIG. 2 shows an example of this selection circuit. The magnetic heads A, B, A', and B' are connected to terminals A ₁ , A ₂ , A ₃ , and A ₄ in FIG. 2, respectively.

1, 2, 3, and 4 are amplifiers, and the outputs of amplifiers 1 and 2 are connected to a first switching circuit 5, and the outputs of amplifiers 3 and 4 are connected to a second switching circuit 6. has been done.

The first and second switching circuits 5 and 6 have terminals
Driven by the switching signal input from _P3 .
This switching signal is generated in synchronization with the rotational phase of the rotary head, and the outputs of heads A and B' or A' and B, which are in contact with the magnetic tape and in the reproducing state, are respectively applied to the third switching circuit 11. The signal is also applied to a comparator circuit 9 via amplifiers 7 and 8. The comparator circuit 9 compares the envelope level with the reproduction signal of the heads A and B' or A' and B applied via the amplifiers 7 and 8, and outputs a binary signal corresponding to the magnitude relationship to the terminal P. Output to ₁ .

The signal output to the terminal P ₁ is applied to the third switching circuit 11 via the terminal P ₂ , and as the output of the third switching circuit 11, the signal is applied to the first and second switching circuits 5 and 6. The configuration is such that the signal with the higher output level among the outputs is output to terminal _B1 . FIG. 3 shows a specific example of the configuration of the comparison circuit 9.

In FIG. 3, S _A and S _B are the amplifiers 7 and 8.
12 and 13 are envelope detection circuits 14 are level comparison circuits;
5 is a Schmitt circuit having hysteresis characteristics. The problem here is that terminals A ₁ to _{A 4} ,
Terminals other than B ₁ , C ₁ and _{C 2} are inside the integrated circuit, and terminal A ₁
~The average signal level input to _A4 may vary depending on the model (for example, an NTSC VTR or a PAL VTR).
(VTR), there will be a problem as explained in FIG. 4, and multiple types of integrated circuits will be required.

In FIG. 4, A and B in a schematically show the output waveforms of amplifiers 7 and 8, respectively.
A and B in b indicate the envelope detection output.

In order to stabilize the switching operation near the switching point, the Schmitt circuit 15 has hysteresis characteristics so that switching occurs when a difference of more than a predetermined threshold level _T1 occurs between the signals A and B. It is configured to have.

Therefore, a switching signal is generated at point (a) in FIG. 4b, and the output of the third switching circuit 11 becomes as shown in c.

On the other hand, the average output level of amplifiers 7 and 8 is b
If the threshold level _T1 is small as shown in A' and B', a switching signal is generated at point (B), and the output of the third switching circuit 11 becomes as shown in d.

As is clear from the waveforms c and d, in the case of a low-level input, the actual switching point starts from the point where the levels of both signals A' and B' match ((b) in Figure 4).
Point) will be delayed compared to point (a), and a section with a lower reproduction signal level will actually be used.

OBJECTS OF THE INVENTION The present invention aims to solve the above-mentioned conventional problems, and is configured to allow the fixed hysteresis width to be varied outside the integrated circuit, thereby enabling optimal design.

Structure of the Invention The present invention performs envelope detection of reproduced signals from two magnetic heads, compares the detected outputs by a comparing means, and selectively switches and extracts the reproduced signals of both heads based on the output of the comparing means. In addition, by feeding back the output of the comparing means to the detecting means, the hysteresis characteristic of the comparing means is changed equivalently.

DESCRIPTION OF EMBODIMENTS The feature of the present invention is that in the configuration shown in FIG.
As shown in Figure A, the output terminal P1 of the comparator circuit ₉ and the _C2 terminal of the detection means are connected via a feedback resistor _RX .

According to this configuration, the input terminals S _A and S _B in FIG.
When the input signals are shown in Fig. 6 A and B, the output of terminal P ₁ (Fig. 6 C) is fed back to terminal C ₂ , so the detected voltage A' of terminal C ₁ is affected by this feedback. However, as shown by the dotted line, the detected voltage B' at terminal _C2 becomes a little higher when the C waveform is at a high level, and becomes a little lower when the C waveform is at a low level.

Therefore, the hysteresis width can be equivalently changed by selecting the value of the resistor _R.sub.X.

In addition, as shown in Fig. 5 B and C, the resistances R _X1 ,
Terminals P _{1 and C 2 may be connected in a circuit consisting of R X2 and capacitor} C _X1 or resistor R _X3 and capacitor C _X2 .

Further, although the case where the hysteresis width is reduced has been described above, it is also possible to increase the hysteresis width by providing a feedback circuit between the terminal _P1 and the terminal _C1 .

Effects of the Invention As described above, according to the present invention, it is possible to equivalently change the hysteresis width to a desired value using an external circuit with a simple configuration. There is no need to create a new integrated circuit.

[Brief explanation of the drawing]

Figure 1 is a plan view showing the arrangement of the magnetic head of a VTR, Figure 2 is a block diagram of a conventional switching circuit, and Figure 3 is a block diagram of a conventional switching circuit.
The figure is an electrical connection diagram of the main parts, Fig. 4 is a waveform diagram explaining the same operation, Fig. 5 A, B, and C are electric circuit diagrams showing the main parts of the embodiment of the present invention, and Fig. It is an operation explanatory diagram. 1, 2, 3, 4, 7, 8... amplifier, 5, 6,
11...Switching circuit, 9...Comparison circuit, 12, 13
... Envelope detection circuit, 14 ... Comparison circuit,
15... Schmitt circuit.

Claims (1)

[Claims] 1. First and second detection means for obtaining envelopes of reproduction signals of two magnetic heads;
a comparison means having a hysteresis characteristic that compares the outputs of the detection means and generates an output depending on the level of the two outputs, and selectively extracts the outputs of the two magnetic heads according to the output of the comparison means. switching means, the output of the comparison means is fed back to one of the detection capacitance terminals of the first or second detection means through a resistor, and the hysteresis width setting of the comparison means is variable by the value of the resistor. A rotating head type magnetic recording/reproducing device characterized by: