JPH0715775B2 - Magnetic recording / reproducing device - Google Patents

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magnetic recording / reproducing apparatus such as a video tape recorder using a small diameter cylinder.

2. Description of the Related Art In recent years, magnetic recording and reproducing devices have been using VHs that use a small diameter cylinder.
Many S-type or VHS-C type integrated cameras have been released. In that servo system, theoretically,
There is a condition called back tracking reproduction, and there is a problem that there is a jitter level that cannot be ignored even in self-recording reproduction. Here, the 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. 6 (a) is a VHS (including VHS-C ...) recording method using a small diameter cylinder (only the relevant portions are shown), in which a ₁ and a ₂ of the control track are used as reproduction servos. Playback control signal used (hereinafter PB CTL
Is called). As a VHS type servo system, P
Since a ₁ and a ₂ of B CTL are indistinguishably equal and the phase is controlled, 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 / reproduction, there is a 1/2 probability that the recording and reproducing tracks are different. This state is called back track playback. Further, 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 the sixth (b), the duty of the control signal (CTL) is set to 1 for the A and B heads.
Differentiate the frame by making it longer than before (duty 60:40). In this case, it does not affect the PB CTL required for the servo system. That is, in FIG. 6 (a), Therefore, there is no distinction between one frame of A and B and one frame of A'and B '. However, in (b), for example, Therefore, it is possible to distinguish between A and B and A ′ and B ′.

Based on the above method, a conventional magnetic recording / reproducing apparatus will be described below with reference to the drawings.

FIG. 3 shows the configuration of a conventional magnetic recording / reproducing apparatus. 1 is a duty converter of a recording control signal (hereinafter referred to as a duty converter) for converting the duty of a recording control signal (hereinafter referred to as REC CTL) from 60:40 to repetition of 65:35 and 60:40. ), 2 is a discriminator for backtracking reproduction (hereinafter referred to as backtra discriminator), and 3 is an acceleration pulse generator. A control signal (REC CTL (IN)) for recording before duty conversion is input to the input 11 of the duty converter 1, a head switching signal (hereinafter, referred to as HSW) is input to the input 12, and the input 13 is the above-mentioned. A switching signal with a period twice that of HSW (1 / 2HS
W) is input, and a recording control signal (REC CTL (OUT)) after duty conversion is output from the output 14 and supplied to the control head (CTL head). The playback control signal (PB
CTL), the HSW is input to the input 22, and the 1 / 2HSW is input to the input 23, and the acceleration command signal is output from the output 24 and supplied to the input 31 of the acceleration pulse generator 3. An acceleration pulse is output from the output 32 of the acceleration pulse generator 3 and supplied to the capstan motor as a capstan control signal E _CAP .

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

(1) During recording, as shown in Fig. 4, HSW (a) and 1/2
The phase relationship of HSW (b) is defined, and these 2 signals are input to REC CTL (OLT) via duty converter 1.
(C) is obtained. That is, HSW (a) is high level (H), 1
The duty of REC CTL (OUT) for one frame where / 2HSW (b) starts at HIGH level (H) is: And HSW (a) is (H) and 1 / 2HSW (b) is at LOW level (L), REC CTL (OU
T) duty is Is. The above-mentioned REC CTL (OUT) is supplied to the CTL head and recorded.

(2) During playback, as shown in Fig. 5, HSW (a), 1 / 2H
SW (b) has the same phase relationship as in FIG. 4, and these two signals are input to the back-tra discriminator 2 and the phase reference signal (d)
Is created inside the back tray discriminator 2. That is, the relationship is as shown in Table 1 below.

Here, L ... LOW level, H ... HIGH level, and when PB CTL (e) is in the state of FIG. 5, REC of FIG.
The phase of CTL (OUT) (c) and one frame are shifted, and the state is so-called back trashing reproduction. Depending on whether the phase of the rising edge a ₁ of one frame with a duty of 65:35 of PB CTL (e) is L or H with respect to the phase reference signal (d), tracking during reproduction is performed. It is possible to determine whether it is the back side or the front side, and the relationship shown in Table 2 below is established.

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-track reproduction, an acceleration command is output from the back-track discriminator 2 and input to the acceleration pulse generator 3, and the acceleration pulse (f) Is generated and supplied as a capstan control signal E _CAP to accelerate the capstan. Fig. 5 (g) shows the accelerated PB CTL (acceleration), and the acceleration pulse (f) accelerates the capstan about 1.3 times for about 2 frame periods (constant time).
As indicated by CTL (acceleration) (g), forcibly accelerating to run for about 3 frames in 2 frame periods, the back tracking reproduction is shifted to the front tracking reproduction. At the end of the acceleration pulse (f), the state is almost close to the table tracking, and then the normal servo system pulls the table tracking reproduction. It should be noted that no acceleration pulse is generated during the surface tracking reproduction.

Problems to be Solved by the Invention Generally, the back or front of the playback tracking is determined by the establishment of 1/2 when the playback mode is started, but the cycle and phase of the playback control signal are constant immediately after the playback is started. If the back tray discrimination is always operating as in the above-mentioned conventional example, the table tracking may be performed due to an erroneous discrimination immediately after the start of reproduction or due to external noise during reproduction. There was an inconvenience that the back tracking was erroneously determined.

Means for Solving the Problems In order to solve the above-mentioned problems, the magnetic recording / reproducing apparatus of the present invention provides a timing signal for operating the back tracking reproduction discriminator only for a certain period after a certain period of time after the reproduction is started. A discrimination pulse generator for generating the discrimination pulse is provided.

Effect As described above, according to the present invention, by adding the discrimination pulse generator, it is possible to correctly discriminate the back tiger reproduction when the cycle and the phase of the reproduction control signal are stabilized after the reproduction is started. Becomes Therefore, back tracking reproduction can be prevented without malfunction, and as a result, jitter can be reduced and image quality can be improved.

Example A magnetic recording / reproducing apparatus according to an example of the present invention will be described below.
A description will be given with reference to the drawings. FIG. 1 shows a block diagram of a magnetic recording / reproducing apparatus according to an embodiment of the present invention. Figure 2 shows
FIG. 6 is a timing diagram according to an embodiment of the present invention. Incidentally, in FIG. 1, parts having the same configurations as those of the conventional magnetic recording / reproducing apparatus of FIG. 3 are designated by the same reference numerals, and detailed description thereof will be omitted. In FIG. 1, the duty converter 1
The recording control signal (REC CTL
(IN)), HSW for the second input 12 and 1/2 for the third input 13
Input each HSW and connect output 14 to the CTL head.
The first input 21 of the back tiger discriminator 2 is PB CTL, the second input 22 is HSW, the third input 23 is 1 / 2HSW, and the fourth input 25 is discrimination pulse. Input, and the output 24 is input to the first input 31 of the acceleration pulse generator 3. The discrimination pulse is input to the second input 33 of the acceleration pulse generator 3, the acceleration pulse is output from the output 32, and the control signal E _{CAP for} controlling the drive of the capstan motor is supplied.
A reproduction start command signal or operation is applied to the input 41 of the discrimination pulse generator 4, and the discrimination pulse is obtained at the output 42.

The operation of the magnetic recording / reproducing apparatus of one embodiment of the present invention configured as described above will be described below with reference to FIG.

(1) At the time of recording, exactly the same as at the time of recording of the above-described conventional example, the duty-converted REC CTL (OUT) is supplied to the CTL head for recording.

(2) the time of reproduction, from the starting point t ₀ of the playback start command (h) as shown in FIG. 2, the operation period of the predetermined time period T ₂ of the from t ₁ point delayed by a predetermined time T ₁ to point t ₂ Such a discrimination pulse (i) is generated at the output 42 of the discrimination pulse generator 4.
During the above delay time T ₁ , PB CTL (e) ′ is →→
As shown in →, the cycle and phase become stable.
Thereafter, the discrimination pulse (i) is supplied to the back tiger discriminator 2 and the acceleration pulse generator 3 as shown in FIG.
During the operation period T ₂ , just like the above-mentioned conventional reproduction, by performing the back tiger discrimination and accelerating the capstan, the back tiger reproduction is performed as in →→→ of PB CTL (e) ′. Inverts the capstan phase for table tiger reproduction. Generally, the delay time T ₂ is 0.5 to 1 second, and the operation period T ₂ is 0.3 to 0.5 seconds.

EFFECTS OF THE INVENTION As described above, according to the present invention, it is possible to perform back-traffic discrimination in a state where the cycle and phase of the reproduction control signal are stable,
Back tracking playback can be prevented stably. Therefore, it is possible to prevent the occurrence of jitter due to the back tracking reproduction without malfunction, and it is possible to improve the reproduction image quality.

[Brief description of 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 diagram during reproduction in the same embodiment, and FIG. 3 is a block diagram showing a configuration of a conventional magnetic recording / reproducing apparatus. FIG. 4 is an operation timing chart at the time of recording of the device,
FIG. 5 is an operation timing chart for the same reproduction, and FIG. 6 is a VHS recording pattern chart. 1 ... Duty converter, 2 ... Back tracking reproduction discriminator, 3 ... Acceleration pulse generator, 4 ... Discrimination pulse generator.

Claims (1)

[Claims] 1. A first recording control signal is supplied to a first input section, a head switching signal is supplied to a second input section, and a cycle twice that of the head switching signal is supplied to a third input section. The first and second duty-converted first and second head switching signals are supplied to the first output section.
The recording control signal duty converter for generating an alternate signal of the recording control signal of No. 2 and the reproduction control signal to the fourth input section, and the head switching signal to the fifth input section. Then, the 1/2 head switching signal is supplied to the sixth input section, and the discrimination pulse is supplied to the seventh input section.
And a back tracking reproduction discriminator that generates an acceleration command signal at the output section of, and the acceleration command signal at the eighth input section,
An acceleration pulse generator that supplies the discrimination pulse to the ninth input section, generates a capstan acceleration pulse to the third output section, and supplies a capstan control signal, and a reproduction start command to the ninth input section. A magnetic recording / reproducing apparatus comprising: a discriminating pulse generator that supplies a signal and outputs the discriminating pulse that defines an operation period of the back tracking reproducing discrimination.