JPH0429123B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Application of the Invention] The present invention relates to a video tape recorder (hereinafter referred to as VTR) that can record while playing back.

[Background of the invention]

The need to record while playing back arises when inserting a title or the like into a recorded tape, especially when superimposing a title on a recorded video. The problem with realizing the above using conventional technology is that two VTRs are required.

The prior art and its problems will be explained below with reference to FIG. In FIG. 1, 1 is a first VTR for playing back a recorded tape, 2 is a device for generating a text video signal for a title, 3 is a mixer for superimposing a text video signal on a reproduced video signal, and 4 is a mixer for superimposing a text video signal on a reproduced video signal. This is a second VTR that records a video signal with superimposed titles. The character video signal generating device 2 may be composed of a title subject and a television camera, or may be composed of a keyboard and a character generator. In any case, care is taken to ensure that the signals from the first VTR 1 and the signals from the character video generator 2 are substantially synchronized. As is clear from FIG. 1, the disadvantage of the prior art is that it requires two expensive VTRs.

[Purpose of the invention]

SUMMARY OF THE INVENTION An object of the present invention is to eliminate the above-mentioned drawbacks of the prior art, and to provide a video tape recorder that can record while playing back and allows title insertion with a single VTR.

[Summary of the invention]

The present invention makes it possible to record while reproducing by providing a recording head and a reproducing head, and by arranging the mounting positions of the heads so that reproduction can occur prior to recording. moreover,
In order to enable so-called simultaneous monitoring, in which playback is performed while recording, the playback head is equipped with an electromechanical transducer (which can produce mechanical changes by applying electricity) such as a bimorph board.
The arrangement can be switched so that the playback head precedes the recording head during superimposition, and the recording head precedes the playback head during simultaneous monitoring.

[Embodiments of the invention]

FIG. 2 shows a block diagram of an embodiment of the present invention. The feature of Figure 2 is the first VTR in Figure 1.
The first and second VTRs 4 were replaced with a single VTR 13. The magnetic tape 5 is running in the direction shown at 12, and the recorded signal on the tape first arrives at the playback head 6, where the signal is read out, then is erased by the erase head 7, and finally by the recording head 8. Rewritten to a new video signal. 10 is an erase circuit. The signal read out by the playback head 6 is demodulated into a playback video signal by a playback circuit 9. The character video signal generator 2 outputs a character video signal that is almost synchronized with the reproduced video signal. Therefore, the mixer outputs a video signal in which the character video signal is superimposed on the reproduced video signal. This superimposed video signal is recorded on the magnetic tape 5 by the recording circuit 11 and the recording head 8. Therefore, with the apparatus shown in FIG. 2, it is possible to superimpose a title or the like onto a recorded tape.

Fig. 3 shows an example of the mounting position of the heads when the present invention is used in a two-head helical scan type VTR with different azimuths, and Fig. 4 shows a track pattern on the tape as seen from a recorded image. . 14 in FIG. 3 is a rotating cylinder, 17
is an erasing head, and 15 indicates the direction of rotation of the cylinder. The tape recording track patterns determined from the cylinder rotation direction 15 and tape running direction 12 are as shown in a, b, c, d, and e in FIG. Third
In the figure, the reproducing head 6 and the recording head 8 are selected to have the same azimuth, and the reproducing head 16 and the recording head 18 are selected to have the same azimuth.

The heads are all installed at the same height as shown in FIG. Under these conditions, the relative positions of each head on the tape are as shown in FIG. That is, since all the heads are mounted at the same height, the reproducing head 6, erasing head 7, and recording head 8 are arranged on the same track.
The tracks in Fig. 4 each correspond to one field of the television signal, and are temporally a, b, e, d, e.
are recorded in this order. Reference numeral 19 in FIG. 4 indicates the direction of movement of the head. Therefore, in order to re-record while reproducing, the reproducing head 6 must precede the recording head 8, and the positional relationship as shown in FIG. 4 must be established. In order to do this, in FIG. 3, if the mounting heights of the heads are the same, the reproducing head 6 is located counterclockwise than the recording head 8 (same azimuth as 6), and the recording head 18 (different azimuth than 6) is located counterclockwise. ) should be more clockwise.

However, if the head heights are not the same, this need disappears. That is, the reproducing head 6 only needs to precede the recording head 8, for example, the fourth head.
In the figure, when the recording head 8 is tracing track C, the reproducing head 6 may trace e (a track having the same azimuth as track C). This means that the mounting position of the reproducing head 6 in FIG. 3 is higher than that of the recording head 8.

Next, a case will be described in which the present invention is implemented in a VTR having a simultaneous monitoring function. Figure 5 shows the present invention using a two-head helical scan system with different azimuths.
An example of the head mounting position when applied to a VTR, FIG. 6 is a diagram showing a track pattern on a tape viewed from the recording surface. The difference between FIG. 5 and FIG. 3 is that the reproducing head 16 is mounted on a pymorph plate 20 and that the recording head 18 precedes the reproducing head 16. Suppose now that no voltage is applied to the pymorph board and all heads are installed at the same height. At this time, the positional relationship of each head on the tape is as shown in FIG. 6, in which the erasing head 17, the recording head 18, and the reproducing head 16 all trace on the track c. Therefore, the reproducing head traces the traces recorded by the recording head 18, resulting in a mode called simultaneous monitoring in which recording and reproducing are performed.

Next, when a voltage is applied to the pymorph plate 20 and the height of the playback head 16 is moved upward as shown by the arrow 21 in FIG. 5, the position of the playback head 16 on the tape changes from track c to track e shown in FIG. Move to track. Therefore, the reproducing head 16 is similar to the recording head 18.
It will now trace a more advanced location, and in this case it will be in superimpose mode, which records while playing. In order to add a superimpose mode to a VTR having such a simultaneous monitoring function, a simple modification can be made by attaching the reproduction heads 6 and 16 to the pymorph board and applying a voltage to the azimuth.

What should be noted in Fig. 5 is the playback head 16.
The objective is to make the angle θ between the recording head 18 and the recording head 18 as small as possible. Although this has no meaning for simultaneous monitor mode, it is an important element for superimpose mode. In a two-head helical scan VTR, one frame of signal is written in two heads, resulting in a seam in the reproduced signal. In order to make this joint less noticeable, it has been decided that the joint should be positioned before the vertical synchronization signal. Therefore, when reproducing by the reproducing head 16 and rerecording by the recording head 18, the above-mentioned joint position will be shifted by θ in FIG. Therefore, it is necessary to install it at a position where θ is sufficiently small, or to delay the recording signal accordingly.

Another embodiment in which the present invention is implemented in a VTR having a simultaneous monitoring function will be described with reference to FIGS. 7 and 8. The difference between FIG. 7 and FIG. 5 is that when all the heads are arranged at the same height, the reproducing head 6 is selected to be in a position ahead of the recording head 8. Assume now that no voltage is applied to the pymorph plate and the reproducing head 6 and recording head 8 are at the same height. At this time, the positional relationship of each head on the tape is as shown in FIG. 8, with each head 6, 7, and 8 tracing on the c track. Therefore, the reproducing head 6 precedes the recording head 8, and a superimpose mode is adopted in which recording is re-recorded while reproducing. Next, a voltage is applied to the pymorph plate, and arrow 2 in Figure 7
When the height of the reproducing head 6 is moved downward as shown in FIG. 2, the position of the reproducing head 6 on the tape moves from the c track to the a track shown in FIG. Therefore, the recording head 8 precedes the reproducing head 6 by about one frame, and becomes a simultaneous monitor mode in which recording and reproducing are performed.

In the present invention, by simply installing a playback head in a position preceding the recording head in one conventional VTR, it is possible to ``superimpose characters such as a title on a recorded tape,'' which conventionally required two VTRs. enable. Especially for helical scan VTRs that can be monitored simultaneously,
Effects include being able to switch between simultaneous monitor mode and superimpose mode simply by attaching the playback head to a rotating cylinder via an electromechanical transducer such as a pymorph board and applying voltage to this electromechanical transducer. It has the following.

[Brief explanation of drawings]

FIG. 1 is an explanatory diagram of a conventional superimpose device, FIG. 2 is a block diagram of a superimpose device for a video tape recorder that can record while playing back according to the present invention, and FIG. 3 is an illustration of the tape recorder of FIG. An explanatory diagram of the rotating cylinder used, Fig. 4 is the third
Figures 5 and 7 are explanatory diagrams showing the tape recorder and head positions; Figures 5 and 7 are explanatory diagrams of the rotary cylinder used in the tape recorder of Figure 2; Figures 6 and 8 are Figures 5 and 7, respectively. FIG. 2 is an explanatory diagram showing the tape recorder shown in the figure and the head position. 6...Reproducing head, 7...Erasing head, 8
...Recording head.

Claims (1)

[Claims] 1. In a helical scan video tape recorder in which a video head forms diagonal tracks on a videotape, a recording video head, a playback video head, and a playback video head are displaced in a direction substantially perpendicular to the tape scanning direction. and a circuit arrangement for converting at least a portion of the signal read out by the playback video head into another signal, and in a first mode, the playback video head reads the video tape in advance of the recording video head. scanning, supplying the output signal of the reproducing video head to the circuit device, supplying the output signal of the circuit device to the recording video head, and recording the output signal of the circuit device on the tape by the recording video head. death,
In the second mode, the recording video head scans the video tape in advance of the playback video head, and the playback video head plays back the video signal after the recording video head records the video signal. A video tape recorder that can record while playing.