JPH0715776B2 - Magnetic recording / reproducing device - Google Patents

Description

The present invention relates to a magnetic recording / reproducing apparatus.

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

FIG. 3 (a) is a schematic diagram for explaining a VHS (including VHS-C ...) recording method using a small diameter cylinder (only relevant portions are shown).
a ₁ and a ₂ are reproduction control signals (hereinafter referred to as PB CTL) used for reproduction servo. In a VHS type servo system, since a ₁ and a ₂ of PB CTL are equal and the phases are controlled, the track recorded by the A head is
The servo is normally controlled regardless of whether reproduction is performed by the A'head. Therefore, despite the self-recording / reproduction, there is a 1/2 probability that the recording and reproducing tracks are different. The state in which different tracks are operated during recording and reproduction is called back tracking reproduction.

A state in which recording and reproduction are on the same track will be referred to as table tracking reproduction.

In order to improve the jitter by eliminating the back tracking reproduction described above, one frame of the A and B heads can be distinguished from one frame of the A'and B'heads during recording, and the back tracking can be performed during the reproduction. There is a method of making it possible to determine whether or not the reproduction is performed.

As shown in Fig. 3 (b), the control signal (hereinafter CT
The duty ratio of (L) is (65:35) and (6:
It is a method to distinguish by repeating (0:40). In this case, it does not affect the PB CTL required for the servo system. That is, in FIG. 3 (a), Therefore, there is no distinction between one frame of A and B and one frame of A'and B '. However, in FIG. 3 (b), for example, Therefore, it is possible to distinguish between A and B and A ′ and B ′.

Based on the method as described above, a conventional example will be described below with reference to the drawings.

FIG. 4 shows a block diagram of the conventional magnetic recording / reproducing apparatus. 1 is a recording control signal (hereinafter referred to as REC CTL)
The recording control signal duty converter (hereinafter referred to as the duty converter) for converting the duty ratio of 60:40 to the repetition of 65:35 and 60:40, 2 is a back tracking reproduction discriminator (hereinafter referred to as a back tiger discriminator) 3 is an acceleration pulse generator, and 4 is a capstan phase inversion detector (hereinafter referred to as an inversion detector). The recording control signal before duty conversion (hereinafter referred to as REC CTL (IN)) is input to the input 11 of the duty converter 1, the head switching signal (hereinafter referred to as HSW) is input to the input 12, and the input 13 1/2 head switching signal (hereinafter referred to as 1 / 2HSW) with twice the cycle of HSW is input to and output
Recording control signal after duty conversion to 14 (below
REC CTL (OUT) is output and supplied to the control head (hereinafter referred to as CTL head). The playback control signal (hereinafter PB CTL
Input), HSW is input to input 22, input 2
1 / 2HSW is input to 3. Then, the acceleration command signal is output to the output 24 and is supplied to the input 31 of the acceleration pulse generator 3. An acceleration pulse is output to the output 32 of the acceleration pulse generator 3, PB CTL is input to the input 41 of the inversion detector 4 used as the capstan control signal E _CAP , and HS is input to the input 42.
W is input, and an acceleration stop signal is output to the output 43 and is supplied to the input 33 of the acceleration pulse generator 3.

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

[I] During recording, as shown in Fig. 5, HSW (a) and 1 / 2HS
The phase relationship of W (b) is specified, and these 2 signals are passed through REC CTL (OUT) via duty converter 1.
(C) is obtained. That is, HSW (a) is high level (H)
Then, the duty of REC CTL (OUT) is 1 frame for 1 / 2HSW (b) starting at High level (H). And HSW (a) is (H) and 1 / 2HSW (b) is at LOW level (L), REC CTL (OU
Duty of T) (c) is Is. The above-mentioned REC CTL (OUT) is supplied to the CTL head and recorded (see the above description with reference to FIG. 3).

[Ii] During reproduction, as shown in FIG. 6, the rise of PB CTL (d) is controlled by the action of the servo system so as to come to the center of the slope of the servo error reference signal (e). This is because in the servo system, when the rising edge of PB CTL (d) is in the "+" part of the servo error signal reference (e), the phase is advanced, and when it is in the "-" part, the phase is delayed. Because it has an effect on. Also HSW
(A) and 1 / 2HSW (b) have the same phase relationship as in FIG. 5, these signals are input to the back-tra discriminator 2, and the phase reference signal (c) is created by the back-tra discriminator 2. To be done. That is, the relationship is as shown in Table 1 below.

If PB CTL (d) is in the state shown in FIG.
The REC CTL (OUT) (d) in the figure is shifted by one frame phase and is in the so-called back tracking reproduction state.

Depending on whether the phase of the rising edge a ₁ of one frame of duty 65:35 of PB CTL (d) with respect to the phase reference signal (c) is L or H, the tracking during reproduction is It is possible to determine whether it is a table or a table. The relationship between the H and L periods of the rising edge a ₁ and the reproduction tracking state is as shown in Table 2 below.

As a result of determining whether the reproduction tracking state is the back side or the front side as described above, in the case of the back tiger reproduction, an acceleration command is output from the back tiger discriminator 2 and is input to the acceleration pulse generator 3 to generate an acceleration pulse (j). Occurs and the acceleration of the capstan is started. Further, in the inversion detector 4, the inversion detection gate signal (h) is created in synchronization with the HSW signal (a), and the PB CTL obtained after the capstan is accelerated by the acceleration pulse.
When the rising edge of the (acceleration) signal (f) coincides with the detection period (High level) of the inversion detection gate (i), the acceleration stop command (i) is output and the acceleration pulse (j) ends,
The acceleration of the Capastan stops. After that, by the action of the servo system, the rising edge of PB CTL (acceleration) (f) after acceleration is controlled to come to the center of the servo error reference signal (e), and the phase inversion operation of the capaster is completed.

Problems to be Solved by the Invention The servo system in the conventional magnetic recording / reproducing apparatus described above uses HSW (a) and PB CTL in order to correct the deviation between the position of the track A and the control signal a ₁ in FIG. 3 (b).
The system is capable of changing the phase of (d). This is commonly called variable tracking. Therefore, as shown in Figure 7, HSW
When the phase of (a) and PB CTL (d) are out of phase, if the inversion detection gate (h) is created in synchronization with HSW (a), an acceleration stop command is output at the time of FIG. 7A and the acceleration pulse ( j)
Is stopped, the phase of the PB CTL (acceleration) (f) signal is delayed by the action of the servo system.
Although the phase difference of the rising edge of the SW signal is corrected, it is held in the back tracking state before the pulse acceleration, and there is a problem that the phase inversion operation of the capstan is not performed.

The present invention solves the above-mentioned conventional problems, and provides a magnetic recording / reproducing apparatus that accurately performs the inversion from the back tracking reproduction state to the normal tracking reproduction state and does not cause the jitter due to the back tracking reproduction. It is intended.

Means for Solving the Problems In order to achieve the above object, a magnetic recording / reproducing apparatus according to the present invention uses a first recording control signal input to a first input section and a head input to a second input section. A second recording control signal duty-converted from the first output unit based on the switching signal and the 1/2 head switching signal having a period twice that of the head switching signal input to the third input unit. Recording control signal duty converter for generating and supplying to the control head, a reproduction control signal input to the fourth input section, the head switching signal input to the fifth input section, and a sixth input section. A back tracking reproduction discriminator that outputs an acceleration start command signal from the second output section based on the 1/2 head switching signal input to , 7th
An acceleration pulse generator that outputs a capstan control signal from the third output unit based on the acceleration start command signal input to the input unit of the above and the acceleration stop command signal input to the eighth input unit; A capstan that outputs a capstan acceleration stop command signal to the acceleration pulse generator based on the head switching signal input to the ninth input section and the reproduction control signal input to the tenth input section. A phase inversion detector, wherein the capstan phase inversion detector detects the phase difference between the head switching signal and the reproduction control signal, and the head based on the output of the phase difference detector. Inversion that outputs an inversion detection gate signal that is formed by delaying a pulse signal of a predetermined length earlier than the switching signal, which rises earlier in the phase difference by a minute time. And over preparative detector, is characterized in that it has a comparator for outputting the acceleration stop command signal on the basis the playback control signal and the inversion detection gate signals and.

When the head switching signal and the reproduction control signal are out of phase by providing a capstan phase inverter having a phase difference detector that detects the phase difference between the head switching signal and the reproduction control signal in the above configuration (tracking Even if the variable), the capstan motor acceleration control can be performed by using the reversal detection gate signal that corrects the phase difference to reliably reverse the phase of the capstan, and the normal tracking reproduction from the back tracking reproduction state. You can make changes to the state.

Embodiment A magnetic recording / reproducing apparatus according to an embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a block diagram of a magnetic recording / reproducing apparatus according to an embodiment of the present invention, and FIG. 2 is a timing chart for explaining the operation of the magnetic recording / reproducing apparatus.
The same components as those of the conventional one are designated by the same reference numerals, and detailed description thereof will be omitted.

In FIG. 1, 1 is a recording control signal duty converter, 2 is a back tracking reproduction discriminator, 3 is an acceleration pulse generator, and the above is the same configuration as the conventional one. A capstan phase inversion detector 5 is composed of a phase difference detector 51, an inversion detection gate generator 52, and a comparator 53.

In FIG. 1, reference numerals 61 to 65 are conventionally known main servo circuits, 61 is a tracking volume for controlling the advance and delay of the HSW signal, and the output signal of the tracking volume 61 and the HSW signal are servo errors. Reference signal source 6
Entered in 2. The servo error reference signal output from the servo error reference signal source 62 and the PB CTL signal are compared by the comparator 63.
Is input to the capstan motor 65 via the adder 64, and main servo control is performed.

The operation of the magnetic recording / reproducing apparatus of this embodiment constructed as above will be described below.

The reproduction tracking state is discriminated by the phase of the rising edge a ₁ of the duty ratio (65:35) of PB CTL (d) with respect to the phase reference signal (c) as in the conventional discriminating method, whether the phase is L level or H level. It That is, FIG. 2 shows a state in which the back tracking state shifts to the front tracking state.

First, in the state before the acceleration control of the capstan,
Both the PB CTL (d) and the HWS signal (a) are input to the phase detector 51, and for example, any one of the pulse signals obtained by dividing one frame of the HWS signal (a) into 16 a rises of the PB CTL signal. Depending on whether ₁ or ₂ corresponds, HSW signal (a)
The phase difference Y of PB CTL (d) is detected.

Next, when the acceleration start pulse (g) is output by the back tracking determination and the capstan motor 65 is accelerated, PB CTL (d) changes to PB CTL (acceleration) (f). Along with this, based on the phase difference Y previously detected by the phase difference detector 51, the phase difference Y for the HSW signal is detected.
And the inverted detection gate signal (h) delayed by X is output. The inversion detection gate signal (h) has a pulse width of, for example, 1/4 frame and is delayed by X = 1/16 frame. By the way, for the purpose of correcting only the phase difference Y, the rising edge a of the HSW signal (a) is changed by the phase difference Y.
_1, it is considered to use a fast elevation rise pulse signal from a ₂ as inversion detection gate signal. However, with such a pulse signal, if the acceleration control process is not normally executed for some reason, the rising edge of the PB CTL signal takes the H level period of the pulse signal, and the acceleration stop process is performed. The desired control processing cannot be executed. Therefore, a pulse signal having a predetermined pulse width (for example, 1/4 frame period) that rises earlier than the rising edges a ₁ and a ₂ of the SHW signal (a) by the phase difference Y is formed by delaying it for a minute time (X = 1/16 frame). The inverted detection gate signal (h) is used.

Now, the inverted detection gate signal (h) formed and output in this way is input to the comparator 53, and PB CTL (acceleration)
Inversion detection gate signal (h) between signal (f)
When the PB CTL (acceleration) signal changes from the L level to the H level while is in the H level period, that is, when the PB CTL (acceleration) signal (f) is in the rising state, the comparator 53 accelerates. The stop command signal (i) is output and the acceleration control process is stopped.

Therefore, in the conventional configuration, the inversion detection gate signal (h ') in the conventional configuration shown by the broken line in FIG. 2 (h) is always output with a constant phase difference X with respect to the HSW signal. If the HSW signal (a) and the PB CTL signal (d) were not synchronized before the capstan motor acceleration control, there was a problem as shown in FIG. HSW signal (a) and P before control
Since the inversion detection gate signal (h ') formed by obtaining the phase difference information Y of the B CTL signal (d) and performing the correction with the phase difference information Y is configured to perform the acceleration control of the capstan motor. In addition, it is possible to reliably reverse the back tracking state to the front tracking state without malfunction.

The width of the delay X described above is, for example, the rising edge of the PB CTL signal (d) when the acceleration processing is not executed due to a malfunction.
a ₂ is set so that it does not fall on the rising edge (H level period) of the inversion detection gate (h).
It is not limited to 1/16 frame. Further, the pulse width of the inversion detection gate is not limited to 1/4 frame.

According to the present invention, the phase difference between the head switching signal and the reproduction control signal is detected prior to performing the inversion process from the back tracking state to the front tracking state by accelerating the capstan, and the phase difference signal ( Information), an inversion detection gate signal is formed by correcting the phase difference between the head switching signal and the reproduction control signal, and an acceleration stop command signal is generated based on this inversion detection gate signal and the reproduction control signal obtained after the start of capstan acceleration. Since it is configured to output, tracking inversion failure caused by the phase difference between the head switching signal and the reproduction control signal seen in the conventional configuration does not occur,
It is possible to reliably realize the inversion from the back tracking state to the front tracking state. As a result, it is possible to prevent the occurrence of jitter due to back tracking,
It is possible to obtain a good reproduced image in the front tracking state.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a block diagram of a magnetic recording / reproducing apparatus according to an embodiment of the present invention, FIG. 2 is a timing chart explaining the operation of the magnetic recording / reproducing apparatus, and FIG. 3 is a VHS system VTR. FIG. 4 is a block diagram of a tape recording pattern of the conventional magnetic recording / reproducing apparatus, FIG. 5 is a timing chart for explaining the phase inversion operation of the same, and FIGS. 6 and 7 are conventional magnetic recording / reproducing apparatus. 3 is a timing chart for explaining the operation of FIG. 1 ... Recording control signal duty converter, 2 ...
… Back tracking reproduction discriminator, 3 …… Acceleration pulse generator, 5 …… Capstan phase inversion detector, 51 …… Phase difference detector, 52 …… Inversion detection gate generator, 53 …… Comparator.

Claims (1)

[Claims] 1. A first recording control signal input to a first input section, a head switching signal input to a second input section, and a head switching signal input to a third input section. A recording control signal duty converter for generating a second recording control signal whose duty is converted from the first output section on the basis of the 1/2 head switching signal having a double cycle and supplying it to the control head; Of the reproduction control signal input to the input section, the head switching signal input to the fifth input section, and the 1 / input input to the sixth input section.
A back tracking reproduction discriminator that outputs an acceleration start command signal from the second output unit based on the two-head switching signal, the acceleration start command signal input to the seventh input unit, and the eighth input unit. An acceleration pulse generator that outputs a capstan control signal from the third output unit based on the acceleration stop command signal that is input, the head switching signal that is input to the ninth input unit, and the tenth input unit. A capstan phase inversion detector that outputs a capstan acceleration stop command signal to the acceleration pulse generator based on the input reproduction control signal, wherein the capstan phase inversion detector is the head switching device. A phase difference detector for detecting the phase difference between the signal and the reproduction control signal, and the output of the phase difference detector, and the head switching signal An inversion gate detector which outputs an inversion detection gate signal formed by delaying a pulse signal whose phase difference rises earlier than a rise by a minute time, a reproduction control signal and the inversion detection gate signal obtained after generation of the acceleration start command signal And a comparator that outputs the acceleration stop command signal based on the above.