JP2615492B2 - Magnetic recording / reproducing device - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magnetic recording / reproducing apparatus (hereinafter, referred to as VTR) for recording / reproducing a video signal as a discontinuous track trajectory inclined in the longitudinal direction of a magnetic tape. In particular, the present invention relates to a magnetic recording / reproducing apparatus having a small-diameter cylinder whose cylinder diameter is reduced to 2/3 of that of a conventional one.

2. Description of the Related Art In recent years, magnetic recording / reproducing devices have been
Many S-type or VHS-C type camera-integrated cameras are on the market. In the servo system, theoretically,
There is a state called back tracking reproduction, and there is a problem that the jitter level cannot be ignored even in self-recording reproduction. Here, since the basic operation of the servo system is generally known, a description thereof will be omitted, but the above-described back tracking reproduction will be described with reference to the drawings.

FIG. 2 is a head arrangement diagram of a small-diameter cylinder in which the A head and the A 'head and the B head and the B' head have the same azimuth angle.

FIG. 3a shows a VHS using the small-diameter cylinder shown in FIG.
(Including VHS-C ... the same applies hereinafter) is a recording trajectory (only relevant parts are shown), and rising edges a ₁ and a _{2 of} the control track have reproduction control signals (hereinafter PB CTL and PB CTL) used for reproduction servo. ). In the figure, distance relationship between control head and cylinder (X value)
Is ignored.

As VHS servo systems, a ₁ and a _{2 of} PB CTL
Are controlled equally without distinction, the servo is normally controlled even when the track recorded by the A head is reproduced by the A or A 'head. Therefore, despite the self-recording / reproducing, a state where the recording trajectory and the reproducing head trajectory are different theoretically occurs with a probability of 1/2. This state is called back tracking reproduction. A state in which the recording track and the reproducing head track are on the same track is referred to as front tracking reproduction.

In order to improve the jitter caused by the back tracking reproduction described above, one frame by the A and B heads and one frame by the A 'and B' heads are distinguished at the time of recording. There is a method that allows determination of whether or not it is. As shown in FIG. 3B, the duty of the control signal (CTL) is set to 1 for the A and B heads.
A distinction is made by making the frame longer than before (60:40). In this case, the PB required for the servo system
Does not affect CTL. That is, in FIG. 3a, ▲ ▼: ▲ ▼ = ▲ ▼: ▲
= 60:40, and there is no distinction between one frame of A and B and one frame of A 'and B'. However, in FIG. 3B, for example, ▼: ▲ = 65: 35 ▼: ▲ = 60: 40, and A and B can be distinguished from A 'and B'.

Hereinafter, a conventional example will be described with reference to the drawings based on the above method.

FIG. 4 is a block diagram of a back tracking correction circuit of the above-mentioned conventional magnetic recording and reproducing apparatus. 1 is a duty ratio of a recording control signal (hereinafter referred to as REC CTL) of 60:40.
Recording control signal duty converter (hereinafter referred to as duty converter) for converting to repetition of 65:35 and 60:40 from the above, 2 is back tracking reproduction discriminator (hereinafter called back tiger discriminator), 3 is acceleration The pulse generator 4 is a capstan phase inversion detector (hereinafter referred to as an inversion detector). A recording control signal (hereinafter referred to as REC CTL (IN)) before being subjected to duty conversion to the input 11 of the duty converter 1
), A head switching signal (hereinafter referred to as HSW) is input to input 12, and HSW 2 is input to input 13.
1/2 head switching signal with double period (hereinafter 1 / 2HS)
W) is input, and the recording control signal after duty conversion (hereinafter referred to as REC CTL (OUT)) is output 14
Is output and supplied to a control head (hereinafter referred to as a CTL head). A reproduction control signal (hereinafter referred to as PB CTL) is input to the input 21 of the reverse tiger discriminator 2, HSW is input to the input 22, 1 / 2HSW is input to the input 23, and reverse tracking is input to the input 25. A discrimination operation command is input. Then, an acceleration command signal is output to the output 24 and supplied to the input 31 of the acceleration pulse generator 3. Acceleration pulse generator 3
An acceleration pulse is output to the output 32 of the PB, and the input 41 of the inversion detector 4 used as the capstan control signal _ECAP is input to the PB
CTL is input, HSW is input to input 42, and an acceleration stop signal is output to output 43, which is supplied to input 33 of acceleration pulse generator 3.

The operation of the conventional example configured as described above will be described below.

At the time of recording, as shown in FIG. 5, the phase relationship between HSWa and 1 / 2HSWb is defined, and REC CTL (OUT) c is obtained for these two signals via the duty converter 1. That is, H
For one frame in which SWa is at High level H and 1 / 2HSWb is at High level H, the duty of REC CTL (OUT) is ▲ ▼: ▲ ▼ = 65: 35, and HSW
For one frame where a is H and 1 / 2HSWb starts at LOW level L, the duty of REC CTL (OUT) c is ▲
▼: ▲ = 60: 40. REC CTL (OU
T) is supplied to the CTL head and recorded.

At the time of reproduction, as shown in FIG. 6, the rise of PB CTLd is caused by the servo system operation and the servo error reference signal e
It is controlled to come to the center of the slope. This is because the servo system has an effect in the direction of advancing the phase when the rising edge of PB CTLd is in the "+" part of the servo error signal reference e and in the direction of delaying the phase in the "-" part of the servo error signal reference e. It is. HSWa and 1 / 2HSWb have the same phase relationship as in FIG. 5, and these signals are input to the back tiger discriminator 2, and the phase reference signal c is created by the back tiger discriminator 2.

 That is, the relationship shown in Table 1 below is obtained.

Here, L... LOW level, H... High level When PB CTLd is in the state shown in FIG. 6, the phase of one frame is shifted from REC CTL (OUT) d in FIG. Tracking playback is in effect.

Table or by one frame of the rising edge a ₁ phase is in either of the periods L or H, at the time of reproduction tracking is back duty 65:35 PB CTLd to the phase reference signal c Can be determined.
Rising edge a ₁ of H, the relationship of the reproduction tracking state and L period is a relationship of the following Table 2.

As described above, as a result of determining whether the reproduction tracking state is reverse or front, in the case of reverse tiger reproduction, an acceleration command is output from the reverse tiger discriminator 2 and input to the acceleration pulse generator 3 to generate an acceleration pulse j. Then the capstan begins to accelerate.
Further, in the inversion detector 4, an inversion detection gate signal h is generated in synchronization with the HSW signal a, and a PB CTL (acceleration) signal f obtained after acceleration of the capstan by the acceleration pulse.
Rising edge during the detection period of the inversion detection gate i (High
Level), the acceleration stop command i is output, the acceleration pulse j ends, and the capstan stops accelerating.
Then, the PB after acceleration is
The rise of CTL (acceleration) f is controlled to be at the center of the servo error reference signal e, and the phase inversion operation of the capstan is completed.

However, in the above-described configuration, the VHS VTR usually has two recording modes, a standard mode and a triple mode. Is changed from the standard mode to the triple mode,
When the mode is changed from the double mode to the standard mode, there is a problem that theoretically, the state of the front tracking reproduction is changed to the back tracking reproduction with a probability of 1/2.

The present invention has been made in view of the above problems, and when the above-described recorded mode changes from the standard mode to the triple mode and when the mode is changed from the triple mode to the standard mode, the state of the back tracking reproduction is changed to the front tracking reproduction. To provide a magnetic recording / reproducing apparatus capable of preventing the jitter caused by the back tracking reproduction.

Means for Solving the Problems To achieve the above object, a magnetic recording / reproducing apparatus according to the present invention comprises a first recording control signal input to a first input unit and a head input to a second input unit. A second recording control signal duty-converted from the first output unit based on a switching signal and a 1/2 head switching signal having a cycle twice as long as the head switching signal input to a third input unit. A recording control signal duty converter for generating and supplying the same to a control head, a reproduction control signal input to a fourth input unit, the head switching signal input to a fifth input unit, and a sixth input unit From the second output unit based on the 1/2 head switching signal input to the second input unit and the back tracking determination operation command input to the seventh input unit. A back tracking reproduction discriminator for outputting an acceleration start command signal, a third command based on the acceleration start command signal input to an eighth input section, and an acceleration stop command signal input to a ninth input section. An acceleration pulse generator that outputs a capstan control signal from an output unit, the acceleration switching unit based on the head switching signal input to a tenth input unit, and the reproduction control signal input to an eleventh input unit. A back-tracking discrimination operation command is output from a fourth output unit based on a capstan phase inversion detector that outputs a capstan acceleration stop command signal to a pulse generator and a recording mode discrimination signal input to a twelfth input unit. A back tracking discriminating operation command generator is provided.

According to the present invention, when the mode recorded during playback changes from the standard mode to the triple mode,
In addition, since it is possible to detect the time when the mode is changed from the triple mode to the standard mode, it is possible to execute the back tracking discrimination operation and to prevent the jitter generated by the back tracking reproduction.

Embodiment Hereinafter, a magnetic recording and reproducing apparatus according to an embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a block diagram of a magnetic recording and reproducing apparatus according to one embodiment of the present invention. The same components as those in the related art are denoted by the same reference numerals, and detailed description thereof is omitted.

In FIG. 1, 1 is a recording control signal duty converter, 2 is a reverse tracking reproduction discriminator, 3 is an acceleration pulse generator, 4 is a capstan phase inversion detector, and the above is the same configuration as the conventional one. Reference numeral 5 denotes a back tracking determination operation command generator.

In the magnetic recording / reproducing apparatus configured as described above,
The operation will be described below with reference to FIG.

A recording mode determination signal is input to an input 51 of the back tracking determination operation command generator 5. For example, an L level is input in the standard mode, and an H level is input in the triple mode. The back tracking discrimination operation command generator detects that the recording mode discrimination signal has changed from H → L or L → H, and generates a back tracking discrimination operation command from the output 52. The back tracking reproduction discriminator 2 receives the back tracking discrimination operation command from the input 25 and starts the back tracking discrimination operation. The following operations are the same as in the conventional example, and will not be described.

As described above, according to the present embodiment, a change in the mode recorded during reproduction is detected, and the back tracking determination operation can be started by the back tracking determination operation command generator. It is possible to prevent entering into the state of back tracking reproduction when this occurs.

Effects of the Invention As described above, according to the present invention, even when the mode recorded during reproduction changes from the standard mode to the triple mode, and when the mode changes from the triple mode to the standard mode, the back tracking reproduction discrimination is performed. Tracking correction operation (being in the front tracking playback state) can be performed by the device, so during playback on a VTR using a small-diameter cylinder,
It is possible to obtain an excellent effect that it is possible to prevent jitter in the state of back tracking reproduction which occurs when the recorded mode changes.

[Brief description of the drawings]

FIG. 1 is a block diagram showing an embodiment of a magnetic recording / reproducing apparatus according to the present invention, FIG. 2 is a head arrangement diagram of a small-diameter cylinder of the apparatus, FIG. 3 is a VHS recording pattern diagram, and FIG. Is a block diagram showing the magnetic recording / reproducing apparatus, FIG. 5 is an operation timing chart of the apparatus at the time of recording, and FIG. 6 is an operation timing chart of the apparatus at the time of reproduction. 1 ... Recording control signal duty converter, 2 ...
... Reverse tracking reproduction discriminator, 3... Acceleration pulse generator, 4... Capstan phase inversion detector, 5.

 ──────────────────────────────────────────────────続 き Continuation of the front page (72) Inventor Tohru Okamoto 1006 Kadoma Kadoma, Osaka Prefecture Matsushita Electric Industrial Co., Ltd. (56) References JP-A-64-21742 (JP, A) JP-A 64- 25338 (JP, A)

Claims (1)

(57) [Claims] 1. A recording control signal (duty... 60:40) is supplied to a first input section, a head switching signal is supplied to a second input section, and a head switching signal of the head switching signal is supplied to a third input section. A 1/2 head switching signal having a double cycle is supplied, and a duty-converted recording control signal (duty ... 6
5:35 and 60:40) and supplies a recording control signal duty converter to the control head, supplies a reproduction control signal to a fourth input section, and supplies a head switching signal to a fifth input section. , A half head switching signal to the sixth input unit, a back tracking discrimination operation command to the seventh input unit, and an acceleration start command signal to the second output unit. A tracking reproduction discriminator, an acceleration start command is supplied to an eighth input section, an acceleration stop command signal is supplied to a ninth input section, and a capstan acceleration pulse is generated at a third output section. An acceleration pulse generator for supplying a control signal;
Supplying the head switching signal to a tenth input unit,
A capstan phase inversion detector that supplies the reproduction control signal to an eleventh input unit, generates the acceleration stop command signal at a fourth output unit, and supplies a recording mode determination signal to a twelfth input unit. And a fifth output section comprising a back tracking determination operation command generator for generating the back tracking determination operation command.