JPS58212274A - Rotary head type magnetic video recorder and reproducer - Google Patents

Abstract

PURPOSE:To attain an excellent still picture, by generating an AND output to a tape only for a reproducing track for stopping the capstan drive driving the tape in a low speed with this output. CONSTITUTION:When a switching signal is changed over to a still mode, a gate 3 is interrupted and gates 6, 12 are conductive. A motor control signal passes through the gates 6, 7 to drive a capstan motor 5 in a low speed until the gate 7 is interrupted via a motor drive circuit 4 and a tape is moved little by little. A head switching pulse (d) passes through monostable multivibrators 8, 9 and becomes a detecting pulse (e). On the other hand, an output voltage (f) from a reproducing head is a signal (g) through a level discriminator 11 and a gate. A monostable multivibrator MM13 is triggered with the signal (g) to form a pulse (h). When the pulses (h) and (e) are coincident, the gate 7 is closed and the motor 5 is stopped.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a rotating head type magnetic recording and reproducing apparatus (hereinafter referred to as a VTR), and an object of the present invention is to reproduce still two-beam images in good quality.

As is well known, in a helical scan VTR,
If playback is performed with the magnetic tape stopped, a still image can be played back. However, since the scanning locus of the rotary head on the magnetic tape when the tape is stopped is different from the recording locus, it is not possible to accurately scan one recording locus, resulting in a period in which no reproduction signal is obtained.

By locating this period in which no reproduced signal is obtained near the vertical synchronizing signal, a reproduced image with substantially less damage can be displayed on a television receiver.

In fact, in the case of an azimuth recording method in which recording is performed using a recording head with a width equal to or wider than the recording track width (there is almost no guard band on the recording tape), Japanese Patent Application No. 53-76045 As can be seen, by determining the level of the playback output envelope and moving the tape until the nozzle period was located near the vertical sync signal, a good playback still image could be obtained.

However, even with the azimuth recording method, field still playback is performed using two playback heads of the same azimuth during playback, or recording is performed using a recording head that is narrower than the recording track width. (with guard band), the width of the noise in the still image is too wide, so the conventional method simply moves the tape to a position near the vertical sync signal to eliminate the noise period. However, it was not possible to obtain a stable reproduced still image.The present invention provides a rotating head type magnetic recording and reproducing device that can obtain stable and good still images even in such a case. be.

An embodiment of the present invention will be described below with reference to FIGS. 1 to 3.

Fig. 1 is an explanatory diagram for explaining the operating principle of a two-head helical scan type VTR which is an embodiment of the present invention, Fig. 2 is a block diagram of the main parts of the VTR, and Fig. 3 is a diagram of the same VT.
3 is a waveform diagram of input/output signals of each part of R. FIG.

Figure 1 (A) shows the recording trajectory recorded using the azimuth recording method and the trajectory of the video head when the same azimuth head is used for still image playback. Figure 1 (B) shows the head playback trajectory in each case. Output, (C) is the same bell discrimination signal, (D) is a pulse signal created from the falling part of the level discrimination signal, and (4) is a pulse signal delayed by a certain period of time from the head switching signal. , (F) of the same figure shows the AND output of the pulse signal shown in (D) of the same figure and the pulse signal shown in (A) of the same figure.

In the apparatus of this embodiment, the widths of the two video heads during recording are both 32μ, and the head gap angles are different.

The width of the recording track is 66μ, and there is a 24μ guard band on the tape. In order to obtain field still images without screen blur, two still image reproduction heads are used with the same spacing angle as one of the recording heads, and both head widths are 32μ. There is.

Therefore, in the still image layer, in raw form, track J + "2 recorded on the A head side, which has the same azimuth as the playback head, is played back, and track B, recorded on the B head side, which has a different azimuth from the playback head, is played back. Then you can't make it 6 pages.

Therefore, as shown in Fig. 1, the video output varies depending on the position of the video head during playback with respect to the recording trajectory, and by moving the tape, the head trajectory [A] → [Mouth] - [
C〕−〔Two〕→〔E〕−〔B〕→〔mouth〕→・・・・・・
changes in the order of

The TV screen when playing these 2 shows the trajectory [A]
In the case of [mouth], the entire screen becomes noise, and in the case of [c], the bottom half of the screen becomes noise. In case [2], there is noise in a part of the lower part of the screen, and in case [e], there is no noise or only noise appears in a part of the lower part. Therefore, if you stop in the [e] state, you can obtain a still image that is easy to view. In Japanese Patent Application No. 53-76045, which is a conventional example,
In all of the four cases (1), (c), and (2), the tape stopped, making it impossible to obtain stable still playback images. However, in this embodiment, the noise H/L/S (D in the same figure) is constant for 6 pages from the falling part of the level discrimination signal (C in the same figure) used to determine the level of the head reproduction output (B in the same figure). Create. A certain period of time after head switching (approximately 14.7 m in this case)
sec) Detection pulse created with a delay (E in the same figure)
By taking the AND output (F in the same figure) with the noise pulse (D in the same figure), as shown in Figure 1, the AND output ( An output is generated at F) in the same figure. By using this logical product output (F in the same figure) and stopping the cab scan drive that drives the tape at a low speed, it is possible to obtain a good still image in the state of the trajectory [e], that is, with noise sent to the lower part.

This embodiment will be explained in detail below with reference to FIGS. 2 and 3.

When the VTR is in the normal playback mode, a first motor control signal passes through the gate 3 and controls and drives the capstan motor 6 via the motor drive circuit 4.

Normal playback and static 1 image playback switching signal (PLAY/5
TILL)a is at rest (5TILL) When switching to mode 1', 7vege gate 3 is in a cutoff state, and gate 6 and gates 1-12 are both in a conductive state. The second motor control signal passes through the gates 6 and 7, and the capstan motor 5 is driven at low speed via the motor drive circuit 4 until the gate 7 is cut off, thereby moving the tape little by little. Head switching pulse (3
0H2) di mono stake) Ly multivibrator
Approximately 14.7m from the falling part of the head switching as shown in Figure 3 through 8 and MM9 (hereinafter referred to as MM).
860 slow about 04 m Create a detection pulse e of about 860. On the other hand, the output voltage f from the reproducing head is passed through a level discriminator 11 and a gate 12 to obtain a signal g.

MMla is triggered from the falling edge of the signal g to create a pulse h with a constant width of about 0.4 m 860.

When the pulse h and the pulse e match in time, an output signal 1 is generated in the computer game 110, and this signal...
, 1 By No. 1, the gate 7 is placed in a cut-off state, and the capstan motor 5 is completely stopped. By doing this, it is possible to bring the boundary between the noise band of the reproduced output and the signal section close to the head switching, making it possible to drive the noise to the lower part.

As described above, according to the present invention, stable, high-quality still reproduced images can be obtained.

[Brief explanation of drawings]

FIG. 1 is an explanatory diagram showing the operating principle of a VTR which is an embodiment of the present invention, FIG. 2 is a block diagram of the main parts of the VTR, and FIG. 3 is a waveform diagram of input and output signals of each part of the VTR. 3... Game 1-14... Motor drive circuit, 6... Capstan motor, 6... Gate, 7... River... Gate, 8... Mono multi, 9
・River...Monoma) Vf, 10...and gate,
11...Lehe/"t'fl separate vessel, 12...
...Gate, 13...Monoma) L/f. Name of agent: Patent attorney Toshio Nakao and 1 other person'1 439

Claims (1)

[Claims] When switching from a normal playback state to still image playback, a capstan drive means that switches the capstan to low-speed drive and a section in which the level of an envelope formed by the playback direction of the rotary head are equal to or higher than a predetermined detection level are detected. A logical product output is obtained between a level determining means and a pulse of a constant width created from the rising or falling portion of the determination signal obtained from the level determining means and a pulse created by delaying the switching pulse of the rotary head by a certain period of time. A rotary head type magnetic recording and reproducing apparatus comprising a logic means and a capstan stop means for stopping low-speed driving of the capstan based on an AND output of the logic means.