JPS5883490A - Magnetic recorder and reproducer - Google Patents

Abstract

PURPOSE:To obtain the high speed reproducing picture in excellent way at a long time mode, by using a magnetic head having a large reproduced output sequentially through switching at the high speed reproduction of the 2hr mode recording. CONSTITUTION:An output of amplitude detection circuits 3a, 3b is given to an amplitude comparison circuit 4, the output level is compared, and when the output of the circuit 3a is larger than the output of the circuit 3b, a high level is outputted and when smaller, a low level is outputted. An output (b) is applied as a control signal of a switching circuit SW3 and the switching circuit is selected to the contact (a) at high level and to the contact (b) at low level. Thus, as the output of the circuit SW3, a signal having the largest output level from heads R, L, R', L' is conducted at the high speed reproduction.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention utilizes two rotating magnetic heads having different azimuth angles to produce one field of video signal along one recording trajectory inclined with respect to the longitudinal direction of the magnetic tape. This invention relates to a helical scan type magnetic recording/reproducing apparatus (VTR) that sequentially records color television signals.

An example of this type of VTR is a VH3 type VTR.

This VH8 system VTR generally switches the tape speed to standard recording mode (2 hour recording mode, track pitch 6).
8 .mu.m) and a long-time recording mode (6 hour recording mode, track pitch 19 .mu.m).

The present invention enables high-speed playback of a VTR that can be switched between the standard recording mode and the long-time recording mode, in which the tape speed is higher than the tape speed at the time of recording, even in each recording mode. It is composed of

One embodiment will be described below with reference to the drawings, taking the V) (S method as an example).

Figure 1 schematically shows the arrangement of the magnetic heads on the rotating head cylinder, where R and L are a pair of magnetic heads for the 6-hour mode, and R' and L' are for the 2-hour mode. A pair of magnetic heads for mode, each with a head width of R and L.
, R' is 30 μm, and L' is 46 μm.

The magnetic heads R and R' and L and L' have the same azimuth angle, and the distance between the magnetic heads R and L/and the distance between L and W is the length of the recording trajectory of one horizontal scanning period on the magnetic tape (
370 μm) on the same plane.

That is, during recording and playback in the 2-hour mode, R/, L/
When recording and reproducing in 6-hour mode, the pair of magnetic heads is set to R,
Recording and reproduction are performed using a pair of L magnetic heads.

Recording trajectories on the magnetic tape in this image recording mode are schematically shown in FIGS. 2a and 2b, respectively. If magnetic heads L and L' with the same azimuth angle are used when reproducing a still image in 2-hour mode recording, and magnetic heads R and R' are used when reproducing a still image in 6-hour mode recording, one field of video signal will be repeatedly reproduced. Field still images can be obtained.

Also, during high-speed playback where the tape is played back at a faster tape speed than the tape speed during recording, heads R and L can be used for 6-hour mode recording, but only heads R' and L' are used for 2-hour mode recording. Then, as shown in Figure 2a, 2
In time mode recording, there are wide recording zones between recording trajectories, so good high-speed reproduction images cannot be obtained.

The feature of the present invention is that it solves this problem during high-speed playback in two-hour mode recording.

That is, during high-speed reproduction of 2-hour mode recording, the magnetic head, which is the reproduction output dog, is sequentially switched to use.

FIG. 3 shows the recording trajectory of the reproducing head during high-speed reproduction (6x speed) of 2-hour mode recording.

Ra and La in FIG. 3 are the recording trajectories of heads R and L, respectively, where part A is the reproduction part of heads R and R/, and part B is the reproduction part of heads L and L/.

FIG. 4 is a block diagram of one embodiment. Head R
, L are connected to a first head switching circuit SW1 via amplifiers 1a and 1b, respectively, and heads R' and L' are connected to a second head switching circuit SW2 via amplifiers 1c and 1d, respectively. There is.

The 't' IX 2 head switching circuit S
W1°SW2 is alternately switched to contacts a and b by a conventionally known head switching pulse (FIG. 6a) that is applied to terminal 2 and is switched every half revolution of the head drum.

Further, the output of the first head switching circuit SW1 is led to the contact a of the first amplitude detection circuit 3& and the third head switching circuit SWa, and the output of the second head switching circuit SW2. is the second amplitude detection circuit 3
b and the third head isolating circuit SW3.

The outputs of the first and second amplitude detection circuits 3a and 3b are led to an amplitude comparison circuit 4, where their output levels are compared, and as shown in FIG. When the output of 3a is larger than the output of the second amplitude detection circuit 3b, a high level is output, and when it is smaller, a low level is output.

This output signal is applied as a control signal to the third switching circuit SW3, and is switched to contact a when the signal is at a high level and to contact a when it is at a roller level.

Therefore, the output of this switching circuit SW3 is:
The signal with the highest output level among heads R, L, L', and R' during high-speed reproduction is derived.

In the output of this switching circuit SW3, the luminance signal component is detected by the frequency detection circuit 5 and mixed by the mixing circuit 6 as in the conventional case.
The low-pass converted color signal component is extracted through a low-pass filter, and then converted by a balanced modulator 8 into the original 3.58 MHz signal with time axis fluctuation components removed. The signal is guided to the mixer 6, mixed with the luminance signal, and output to the output terminal 9.

With the second configuration described above, a good reproduced image can be obtained even during high-speed reproduction in the 6-hour mode.

Incidentally, recent VTRs such as the VH8 system are configured so that the carrier waves of the color signals between adjacent recording tracks have a phase difference of 180 in order to eliminate crosstalk of the color signals between adjacent tracks. For example, in the recording trunk by heads R and R', the phase of the carrier wave is advanced by 9o0 every horizontal scanning period, and the head L, R' is
In the recording track L', the phase is shifted in the opposite direction by 90 degrees.

Therefore, when playing part A and playing part B in Fig. 3,
Continuous signal (4,27MH) applied to the balanced modulator 8
It is necessary to switch the direction of change in the phase of z).

Next, this configuration will be explained.

A part of the output of the balanced modulator 8 is applied to a boost gate circuit 9, and a burst signal is extracted and applied to a phase comparator 10;3. The phase is compared with the output of the essMHz reference oscillator 11, and the output according to the phase difference is
A variable oscillator 12 with a center frequency of 3.5 sMHz is controlled to create a continuous signal of 3.58 MHz. on the other hand,
The synchronization separation circuit 13 extracts a horizontal synchronization signal from the reproduced signal, and this horizontal synchronization signal drives the burst gate circuit 9, and the PLL circuit 14 drives the burst gate circuit 9.
Create a KHz signal.

The output of this PLL circuit 14 is applied to a 90° phase rotary circuit 16 which advances or retards the phase shift by 9o0 every 1' horizontal scanning period depending on the control signal.

The control signal is generated by the logic processing circuit 16 from the head switching pulse a and the output signal of the amplitude comparison circuit 4.

That is, as shown in FIG. 6C, a signal whose polarity is inverted between the phase synchronization signal and the low level and the low level of the head switching pulse a is created, and this control signal C is used to control the 90° phase rotor circuit 15. 4. Switch the phase shift direction of , and add the output of this 90° phase rotary circuit 15 and the output of the variable oscillator 12 from the balanced modulator 17;
It is applied to the balanced modulator 8 as a 27 MHz signal.

With this configuration, the output terminal 9 is connected to A and B in FIG.
A continuous signal can be obtained by reproducing a portion of the signal.

As described above, according to the present invention, good high-speed reproduction images can be obtained even in the long-time mode.

[Brief explanation of drawings]

FIG. 1 is a plan view schematically showing the arrangement of heads on a head cylinder according to an embodiment of the present invention, and FIG. b is a diagram schematically showing recording trajectories in standard recording mode and long-time recording mode, FIG. 3 is a diagram illustrating a scanning trajectory during high-speed playback in long-term recording mode, and FIG. The electrical block diagram shown in FIG. 5 is an explanatory diagram of the same operation. 1a, 1b, 1c, 1d--amplifier, 3a, 3b...
... Amplitude detection circuit, 4 ... Amplitude comparator, 6
...Frequency detection circuit, 6...Mixing circuit,
7...Low pass filter, 8.1'...
... Balanced modulator, 9 ... Burst gate circuit, 10 ... Phase comparator, 11 ... Reference oscillator, 12 ... Variable oscillator, 13 ...・・Synchronization separation circuit, 14---0- PLL circuit, 16...
...900 phase rotary circuit, 16 ... logic processing circuit. Name of agent: Patent attorney Toshio Nakao and 1 other person No. 3
Figure A Figure 4

Claims (1)

[Claims] Two pairs of magnetic heads are each formed of two magnetic heads having different azimuth angles, each pair of magnetic heads has an indexing angle of approximately 18o0, and the magnetic heads between the different pairs of magnetic heads are as follows: Magnetic heads with different azimuth angles are placed close to each other on a rotating cylinder on the same plane, and the magnetic tape is wound along the rotation locus of the magnetic heads to selectively adjust the magnetic tape to two tape speeds. one of the two magnetic head pairs is selected in accordance with the tape speed, and the two magnetic heads of the selected magnetic head pair are sequentially switched for one horizontal scanning period per field. has color signals with different phase shift directions,
A control signal is generated by comparing the reproduction output level of the magnetic head in a high-speed reproduction image reproduction state by making the tape speed faster than the recording speed during reproduction. A magnetic recording and reproducing apparatus characterized in that the reproduction output of the head is sequentially extracted to produce a reproduction signal, and the phase shift direction of a color signal in the reproduction signal is switched according to the magnetic head selected by the control signal.