JPS59112778A - Magnetic recording and reproducing device - Google Patents

Abstract

PURPOSE:To eliminate excellently a noise and a flicker in still reproduction at low cost by switching head pairs in a still picture and switching the amounts of delay for a pseudo vertical synchronizing signal on the basis of a large/small rate decision. CONSTITUTION:Signals from respective R, L, L', and R' heads 1-4 are selected through switches 10 and 11 by the output of a PG9 to obtain two head signals. Those signals are amplitude-detected and compared with each other to generate their large/small comparison signal, and an output changeover switch 15 is so operated by said comparison signal that a large head output is selected. This selected output is made into a video signal, which is mixed with the pseudo vertical synchronizing signal by a mixing circuit 17 to output a video signal. The amount of delay of the pseudo vertical synchronizing signal is controlled by the large/small comparison signal and head switching signal obtained by selecting a value matching with the heads 1 and 4, or 2 and 3.

Description

[Detailed description of the invention] Industrial applications The present invention relates to a magnetic recording/reproducing device.

Conventional configuration and its problems In both the 2-hour mode and the 6-hour open mode, a method that enables high-speed search and field still without blur is to use heads with different azimuth angles at approximately IH or 2H, as shown in Figure 1. A four-head system installed with a gap (870 μm to 740 μm) has been developed. In this head specification, in order to enable all mode playback, the L' head is approximately 4.
A head width of about 80 μm is used for the remaining heads. With this head specification, when performing field stills, when the tape position is shifted to the completely optimal position, in 6-hour mode, R+r<' head pair,
In the 2-hour mode, the pair of L and L' heads is optimal.

If automatic noise transmission is not used as a simple still system, the worst case scenario is full noise, especially in the 2-hour mode, resulting in a very unsightly appearance.

By the way, as mentioned above, since the head width is set to 80 μm or more, in relation to the track pitch of 58 μm in the 2-hour mode, there is always output to either the R or L head that contacts the magnetic tape. appears. Therefore, by comparing the head outputs of adjacent heads and selecting the head with the highest output for reproduction, the above-mentioned noise can be significantly improved.

However, another problem is that image shaking occurs. In still images, vertical synchronization tends to become unstable because noise is forced into the 8 vertical synchronization signals to eliminate noise on the screen. A vertical sync signal is added. In the head shown in Fig. 1, the difference between adjacent heads is about 1 to 2H, so the head switching signal can remain constant, and the head switching position can be adjusted depending on the head used. - will change within the lap. However, a shift in the position of adjacent heads results in a shift in the video signal being played back.
As shown in FIG. 2, the relationship between the head switching signal and the video signal is different between a still using R, R' heads and a still using L, L' heads. Note that the values shown in FIG. 2 are approximate numerical values when recording is performed with R' and L' heads using heads with a 2H gap. If you want to completely drive the noise part into the vertical sync signal and play stills using only the R, R' heads or the L' heads, switch the heads to the position where the vertical sync signal is present as shown in Figure 2. All you have to do is match the delay amount of the pseudo vertical synchronization signal created from the signal.

However, if the tape stops at a position on the screen where switching between the R, R' heads and the L, L' heads is determined, vertical wobbling will occur in one of the parts.

That is, if the phase of the pseudo vertical synchronization signal is adjusted to R, then L.

Vertical vibration occurs on the L' head side. For example, the second
In the case shown in the figure, vertical vibration of 4H width occurs. On the other hand, if it is adjusted to the L' head side, a similar vertical vibration will occur on the R and R' head sides. In order to completely eliminate this vertical fluctuation, it is necessary to use a 2H delay line to eliminate the time lag between the R, R' heads and the L, L' heads, which requires a large amount of cost. It is not suitable for realizing simple stills.

OBJECT OF THE INVENTION The present invention solves the above-mentioned conventional drawbacks, recognizes that partial image shake is unavoidable, and aims to realize a practical simple still by stopping vertical shake of a larger portion. The purpose of the present invention is to provide a magnetic recording/reproducing device that can perform the following functions.

Structure of the Invention In order to achieve the above object, the magnetic recording and reproducing apparatus of the present invention comprises:
Two R azimuth heads and two L azimuth heads were mounted so that the different azimuth heads were close to each other and the different azimuth heads were at 180 degrees from each other, and at least one pulse generator was also mounted. a cylinder, and a head switching signal generation circuit that generates a head switching signal using a pulse from a pulse generator at the cylinder;
a comparison means for comparing the magnitude of the outputs of two heads that contact the tape at the same time; a switching means for switching the outputs of the two heads that contact the tape at the same time; a pseudo vertical synchronizing signal generation circuit that generates a synchronizing signal m; a delay amount switching circuit that switches the insertion position of the pseudo vertical synchronizing signal according to field reproduction by the R azimuth head and field reproduction by the L azimuth head; a size ratio discrimination circuit for determining a ratio between an R azimuth image part and an L azimuth image part in an image, and when reproducing a still image, the head output is switched in the screen based on the switching means, and the size ratio discrimination circuit The delay amount switching circuit is controlled by the output of the delay amount switching circuit.

DESCRIPTION OF EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. In Fig. 3, the signals from each head (1) to (4) of R, L, L', and R' are received by an independent amplifier (
5) to (to) and selected via the switch OOQυ by the head switching signal generated by the head switching signal generation circuit (g) based on the output from PG (9), and the head that is in contact with the tape at the same time. There are two signals obtained from . This output is the amplitude detection circuit (2) C
1, the output is compared by a magnitude comparator α◆, and the output selector switch oe is switched to select the head with the larger output based on the magnitude comparison signal that is the output.

The thus selected output is subjected to FM demodulation and chroma processing by the demodulator Ql to become a video signal, mixed with a pseudo vertical synchronization signal by the mixing circuit aη, and output as a video signal. The pseudo vertical synchronization signal is generated by the pseudo vertical synchronization signal generation circuit according to the head switching signal.
The delay amount for this is determined by the delay amount switching circuit (R,
One of the values suitable for the R' heads (1) and (4) and the values suitable for the L and L' heads (2) and (3) is selected. This delay amount switching circuit (E) is configured to operate the R, R' heads (1) (4) using the head switching signal and the magnitude comparison signal.
) or the L' head (2>(3), the magnitude ratio determining circuit Q) which performs the ratio determination.

The fourth factor is a circuit diagram showing a specific example of the size ratio discrimination circuit Qυ, in which the R and L' heads (1) (3) are at high level, and the L and R' heads (2) and (4) are at low level. Head switching signal and R, L heads (1) (2
> using l high level, R', L' head (4) (
When using 3), the magnitude comparison signal that becomes low level is
Exclusive OR gate circuit 4 connects L and L' heads (2
) In case of (3), high level, R, R' head (1)
In the case of (4), by converting to a low level waveform, integrating this waveform using a resistor (R1) and a capacitor (C1), and comparing the average value with the reference voltage using a comparator (total), approximately the duty cycle can be determined. Obtain delay amount switching output with 50% as the threshold.

FIG. 5 is a circuit block diagram showing another specific example of the size ratio discriminating circuit QI). R, R' head on screen (1)
The way in which the image in (4) and the images in the L and L' heads (2) and (3) are switched is that the entire screen is only for one pair of tapes, and when the tape position shifts, the other one gradually changes from above or below. It becomes a herad pair image, and it becomes only this pair. When shifted further, the first pair of images appears from the top or bottom and spreads out. In other words, there is no case where a pair of heads differs only in the center of the face. It can be seen that by utilizing this property, it is possible to determine the size ratio simply by selecting a large number of pairs in the center of the screen. Therefore, the above method is realized by storing the level of the magnitude comparison signal in a D flip-flop (c) at the edge of the output of the delay circuit delayed by about 8.8 ms corresponding to the center of the screen. .

As described in detail, the present invention provides an inexpensive magnetic material that can effectively eliminate noise and vibration in still playback by switching between head pairs during a still screen and switching pseudo vertical synchronization signal delay amount by determining the size ratio. A recording and reproducing device can be realized.

[Brief explanation of the drawing]

Fig. 1 is an explanatory diagram of the head arrangement, Fig. 2 is an explanatory diagram of the relationship between the head switching signal and the video signal in still playback, and Fig. 8 is an explanatory diagram of the relationship between the head switching signal and the video signal in still playback.
The figure is a circuit block diagram of the main part of a magnetic recording and reproducing apparatus according to an embodiment of the present invention, FIG. 4 is a circuit diagram showing one specific example of a size ratio discriminating circuit, and FIG. 5 is a circuit diagram showing another specific example of a size ratio discriminating circuit. FIG. 2 is a circuit diagram showing an example. (1)...R head, (2)...L head, (3)...■
Head, (4)...R' head, (5)-(8)...
Amplifier, (9)...PG, 010υ...switch,
02 F+3・amplitude detection circuit, a<-・size comparator,
α9...Output selector switch, OQ...Demodulator, αη...
・Mixing circuit, 0 peak ・Head switching signal generation circuit, Ql ・
...Pseudo vertical synchronization signal generation circuit, (a)...Delay amount switching circuit, Qυ...Size comparison discrimination circuit Representative Yoshihiro Morimoto Figure 3 Figure 4

Claims (1)

[Scope of Claims] 1. Two R azimuth heads and two R azimuth heads are mounted so that the different azimuth heads are close to each other and the different azimuth heads are positioned at 180 degrees from each other, and furthermore, at least one a cylinder to which two pulse generators are attached, a head switching signal generation circuit that generates a head switching signal using pulses from the pulse generator, and a comparison means that compares the magnitude of the output of two heads that simultaneously contact the tape. , a switching means for switching the outputs of the two heads that are in contact with each other at the same time, a pseudo vertical synchronization signal generation circuit that generates a pseudo vertical synchronization signal approximately corresponding to the vertical synchronization signal position based on the head switching signal, and an R azimuth head. a delay amount switching circuit that switches the insertion position of the pseudo vertical synchronization signal according to field playback and field playback by the L azimuth head; and a delay amount switching circuit that determines the ratio of the R azimuth image part and the L azimuth image part in a still image. a ratio discriminating circuit, and when reproducing a still surface image, the head output is switched in the screen based on the comparing means, and the delay amount switching circuit is controlled by the output of the magnitude ratio discriminating circuit. Apparatus. 2. The magnitude ratio discrimination circuit has an R azimuth or L azimuth head selection waveform generation circuit, an integrating circuit, and a comparison circuit, and discriminates the ratio based on the magnitude of the average value of the selected waveform and the base Q-voltage. The magnetic recording and reproducing apparatus according to claim 1, which is configured to perform
Claims include a delay circuit having a delay amount of four cycles and a D-type flip-flop, storing a magnitude comparison signal at the output of the delay circuit, and using this memory output as a magnitude ratio discrimination output. 2. The magnetic recording and reproducing device according to item 1.