JPS60119655A - Magnetic video recording and reproducing device - Google Patents

Abstract

PURPOSE:To attain beautiful insertion recording by detecting immediately a pilot signal written by a recording video head by means of a tracking video head so as to feed back it immediately to the tracking. CONSTITUTION:Only a video signal is written superimposingly to video heads 3, 4 at insert recording. A signal from video heads 18, 19 is inputted to a pilot signal detecting circuit 15. In corresponding two pilot signals f', f'' to the two video heads 18, 19 respectively, when the video head 18 traces a video track recorded by the video head 3 and tracking is conducted by applying a control signal to a servo circuit 16 so as to maximize the pilot signal f' in other words so as to minimize the pilot signal f'', the superimposing write with less crosstalk is attained. This is applied also to the case with the video head 19.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention 1] The present invention relates to a magnetic recording and reproducing apparatus capable of performing IIa recording by recording a new signal on a portion of a recorded magnetic tape.

[Prior Art] The magnetic recording and reproducing apparatus according to the present invention employs the well-known rotary head method and helical scan method. These methods will be briefly explained based on the drawings.

FIG. 1 is a schematic diagram showing a rotating head system.

- As an example, a two-head system is shown. Two video heads 3 and 4 are attached 1806 adjacent to each other on the circumference of the rotating drum 5. Since the rotating drum 5 rotates at high speed in the direction of arrow B in the figure, the two video heads 3 and 4 also rotate at high speed. An Ω-shaped magnetic data 72 is attached to more than half of the circumference of the rotating drum 5. The magnetic tape 2 is held between a capstan 7 and a pinch roller 8, and is caused to run in the direction of the arrow by the capstan 7.

FIG. 2 is a schematic diagram showing a tape format on a magnetic tape actually recorded by a helical scan type video tape recorder equipped with a rotating drum 5. This diagram is
This is a view of the magnetic tape 2 from the magnetic surface. During recording, the magnetic tape 2 runs in the direction of arrow A at a constant speed. At this time, the signals previously recorded on the magnetic tape 2 are erased by the fixed erasing head 1, so that unrecorded molecules are formed on the magnetic tape 2. The unrecorded molecule contains the next N#1! , a video signal is recorded by the video head 3 or 4. At the time of this recording, at the same time,
Video heads 3 and 4 during playback are on video track 10
and 11 (hereinafter referred to as "tracking"), signal 9 (hereinafter referred to as "control signal"), which serves as a reference for the positioning of video heads 3 and 4, is transmitted. The control head 6 writes on the bottom edge of the tape 2.

Next, during playback, video tracks 1° and 1
The control signal 9 is used to apply a servo to the capstan motor for driving the capstan 7 so that the signal recorded in the video head 1 is reproduced by the video heads 3 and 7Ir, respectively. video head 3 (for example, video head 3)
) is the adjacent video track 1 rack (for example, video track 1).
Even if you trace 1), in the azimuth method, the azimuth angle of the video head is different when recording adjacent video tracks, so it is almost impossible to reproduce the video signal (the loss at this time is (called azimuth loss), so crosstalk is small.

by the way. lI East Record (hereinafter referred to as "insert record") will be explained. Insert recording is recording a new signal on a portion of a recorded magnetic tape. This is shown in Figure 3.

For insert recording, recorded video track 1
Instead of 0 and 11, video tracks 12 and 13 are formed with new signals written, respectively. Video tracks 1o and 11 and new video track 12
Tracking is performed using the control signal 9 in order to match the numbers 1 and 13, respectively. Furthermore, when recording a new video signal, the fixed erase head 1 cannot be used, so the new video signal is directly added to the video heads 3 and 4. That is, overwriting is performed. During this overlapping, the signal currents applied to the video heads 3 and 4 are increased in order to prevent the original video signal from being reproduced during reproduction.

By the way, a video signal consists of a luminance signal and a color signal.
It is. During shielding, the original tone signal is easily damped due to its high frequency, but the original color signal, especially the burst signal, has a low frequency and large amplitude, so it is difficult to erase and is easily reproduced during playback. (The underlying video signal is called "crosstalk.") Furthermore, when insert recording is performed on a magnetic tape recorded with another video tape recorder, noise due to crosstalk of burst signals may appear in the center of the screen, which is very unsightly. To eliminate this, it is necessary to adjust tracking during insert recording by some means. This is because if this is done, noise due to crosstalk will be emitted from the screen.

[Summary of the Invention] The present invention has been made for the purpose of improving such drawbacks, and provides a method for immediately detecting a pilot signal written by a recording video head by a tracking video head and immediately feeding it back to tracking. By this,
The present invention proposes a magnetic recording/playback AM that can automatically track and thereby make beautiful insert recording.

[Embodiment of the Invention] FIG. 4 is a block diagram showing an embodiment of the invention. The differences from FIG. 1 will be mainly explained. Tracking video heads 18 and 19 are provided on the rotating drum 5 at positions that are later than the recording video heads 3 and 4 by θ in circumferential angle with respect to the rotational direction B of the rotating drum 5. . It is preferable that this circumferential angle θ is as small as possible. The video heads 18 and 19 of tracking 1 are also used for reproducing video signals in this embodiment. A recording circuit 41 for recording video signals is connected to the video heads 3 and 4.

The recording circuit 41 receives a signal unrelated to the video signal (hereinafter referred to as "
"Pilot signal". ) is connected to a pilot signal generation circuit 40 that generates a pilot signal f.
' and f'' are superimposed on the video signal and written onto the magnetic tape 2. These pilot signals f' and t'' are signals that can still be detected even after insert recording, such as low frequency signals. Video head 18 and 19 are connected to a reproducing circuit 42 for reproducing the video signal and a tracking means for performing tracking using the pilot signals f' and t''. This tracking means includes a pilot signal detection circuit 15 and a servo circuit 16, which will be explained in detail later.

To explain the general operation of the embodiment shown in FIG. 4, video heads 3 and 4 perform recording, video heads 18 and 1
9 to play. When recording, video heads 3 and 4
Pilot signals f' and fn corresponding to each of the above are written superimposed on the video signal. Also, no pilot signal is written during insert recording.

During insert recording, the signals extracted by the video heads 18 and 19 are simultaneously sent to the pilot signal detection circuit 15.
added to. Here, the magnitudes of the pilot signals t' and f'' are compared, and the signal from the pilot signal detection circuit 15 is added to the servo circuit 16 to perform tracking.

Next, details of the operation of the circuit shown in FIG. 4 will be explained. During normal recording, the video signal and two pilot signals t' and tLJ applied to video heads 3 and 4 are as follows:
written on magnetic tape.

Next, during insert recording, only the video signal is overwritten on the video heads 3 and 4. Video heads 18 and 19 running from behind video heads 3 and 4
If you play it back, you can play back the overwritten parts.

Signals from the video heads 18 and 19 are input to a pilot signal detection circuit 15. If two pilot signals f' and f'' are associated with each of the two video heads 18 and 19, when the video head 18 is tracing the video track recorded by the video head 3, the pilot signal f' so that the maximum
Conversely, if tracking is performed so that the pilot signal f" is minimized, overwriting with less crosstalk can be achieved. The same is true for the video head 19.
Video head 18 corresponding to signal t'
and video head 1 that supports the pilot signal fn.
This is because the azimuth angles of the video heads 9 and 9 are different from each other, and if tracking is normal, the signals output from those video heads will be maximum.

On the other hand, during normal reproduction, the capstan motor 17 is servoed and tracking is performed by applying a control signal from the control head 6 to the servo circuit 16. Therefore, if tracking is performed using the signal from the pilot signal detection circuit 15 during insert recording, insert recording with less crosstalk can be realized.

Next, the pilot signal detection circuit 15 will be explained. Fifth
The figure is a configuration diagram of a pilot signal detection circuit. Input terminal 20 is connected to video heads 18 and 19. The video signal and pilot signals f' and t'' from the input terminal 20 are applied to a band-pass filter 23 for pilot signal t' and a band-pass filter 24 for pilot signal f/1 through a changeover switch 22, respectively. Only the pilot signals f' and f II are selected.The changeover switch 22 is switched by the video head switching signal HC from the reproduction circuit 42 to select the respective filters.The pilot signals passed through the bandpass filters 23 and 24 is amplified by an amplifier 25 and applied to an integrating circuit 26 composed of a capacitor and a resistor, and a DC component is output from an output terminal 27.This DC component is output when the selector switch 22 is on the band-pass filter 23 side. When it is on the bandpass filter 24 side, the pilot signal f is proportional to the magnitude of the pilot signal t'.
It is proportional to the size of n.

Generally, the 1~racking of a servo circuit is achieved by changing the time constant of a mono-multivibrator. FIG. 6 is a configuration diagram of a tracking control circuit in the servo circuit 16. Control No. 1 terminal 35 is connected to output terminal 27 in FIG. The output terminal 37 is connected to the capstan motor 17 via a circuit such as an amplifier. During normal playback, variable resistor 3 for tracking control
0 and a capacitor 34 controls the charging time of the monomulti ti control terminal 28.

Here, 29 is a power supply terminal. When recording inserts, change the selector switch 33 to the electronic variable resistor 3 using an appropriate method.
Switch to 1. The resistance value of this electronic variable resistor 31 can be varied by the DC voltage from the control signal terminal 35, so if the DC voltage from the output terminal 27 of the pilot signal detection circuit 15 is applied to this control signal terminal 35, tracking can be controlled. be able to. That is, if the running phase of the magnetic tape lags behind an appropriate value, the reproduced pilot signal f
' (or f'') becomes smaller, the DC voltage at the output terminal 27 also becomes smaller, and as a result, the voltage applied from the servo circuit 16 to the capstan motor 17 increases, and as a result, the running phase of the magnetic tape advances. Conversely, if the running phase of the magnetic tape advances, the voltage applied from the servo circuit 16 to the capstan motor 17 decreases, which delays the running phase of the magnetic tape. The traveling phase is always controlled to be constant, which enables tracking.

[Effects of the Invention] As explained above, in this invention, the pilot signal written by the recording video head is immediately detected by the tracking video head and immediately fed back to the tracking, so that it is different from other video tape recorders. Even if insert recording is performed on a magnetic tape whose ranking has slightly shifted to 1 after recording, tracking can be automatically performed, which has the effect of making it possible to perform accurate insert recording.

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram showing a rotating head system. FIG. 2 is a diagram showing a tape format on a magnetic tape. FIG. 3 is a diagram showing a tape format on a magnetic tape during insert recording. FIG. 4 is a block diagram showing an embodiment of the present invention. FIG. 5 is a configuration diagram of the pilot signal detection circuit. FIG. 6 is a configuration diagram of a tracking control circuit in the servo circuit. In the figure, 2 is a magnetic tape, 3 and 4 are recording video heads, 5 is a rotating drum, 15 is a pilot signal detection circuit, 16- is a servo circuit, 18 and 19 are 1 to racking video heads, 40 is a pilot signal Generating circuit f / and f'' [This is the pilot signal. Agent Masuo Oiwa Figure 1 Figure 4

Claims (2)

[Claims] (1) Recording a new signal on a portion of the magnetic tape of the recording stream (in a magnetic recording/playback device capable of performing editing and recording, the recording video head provided on a rotating drum, and the rotating drum a tracking video head disposed above the recording video head at a position later than the recording video head with respect to the rotational direction of the rotating drum; and a tracking video head disposed at a position behind the recording video head with respect to the rotational direction of the rotating drum; and a pilot signal unrelated to the video signal to the recording video head. What is claimed is: 1. A magnetic recording and reproducing apparatus comprising: a pilot signal generation circuit for generating a pilot signal; and a tracking means for performing tracking using the pilot signal detected by the tracking video head. (2) The recording video head is provided 1800 degrees adjacent to each other on the circumference of the rotating tram, and includes first and second video heads having different azimuth angles, and the tracking video head is , a third video head that is disposed 180' adjacent to each other on the circumference of the rotating drum and has the same azimuth angle as the azimuth angle of the first video head; a fourth video head having the same azimuth angle as the azimuth angle, the pilot signal generating circuit generates first and second pilot signals, and the first pilot signal is the first pilot signal of the first video head. the second pilot signal is applied to the second video head, and the racking means causes the third video head to trace a video track recorded by the first video head. detecting the magnitude of only the first pilot signal when the fourth video head is tracing a video track recorded by the second video head; A pilot signal detection circuit that detects the magnitude of the magnetic tape, and a servo circuit that controls the running phase of the magnetic tape so that the output from the pilot signal detection port is maximized. Magnetic recording review cap L described in paragraph 1