JPH0770114B2 - 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 / reproducing devices have been using VHs that use small diameter cylinders.
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 the jitter level cannot be ignored 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.

Figure 6 (a) shows a VHS (VHS-C) using a small diameter cylinder.
The same applies to the following) recording method, and a ₁ and a ₂ of the control track are playback control signals (hereinafter referred to as PB CTL) used for playback servo. In a VHS type servo system, since a ₁ and a ₂ of PB CTL are phase-controlled as equal without distinction, even if the track recorded by the A head is reproduced by the A head or A'head, the servo is normally operated. Controlled. 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 tracking reproduction. 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 it is reproduction.

As shown in FIG. 6 (b), the control signal (CTL)
The duty is set to be longer than that of the conventional one (duty ratio 60:40) for one frame of the A and B heads, thereby making a distinction. 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 control method as described above, a conventional example will be described below with reference to the drawings.

FIG. 3 shows the configuration of a conventional magnetic recording / reproducing apparatus. In FIG. 3, 1 is a duty converter of a recording control signal (hereinafter referred to as duty conversion) for converting the duty ratio of the 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 back tracking reproduction (hereinafter referred to as a back tiger discriminator), 3
Is an acceleration pulse generator, and 4 is a period reference generation timer. A control signal (REC CTL (IN)) for recording before duty conversion is supplied to the input 11 of the duty converter 1, a head switching signal (hereinafter referred to as HSW) is supplied to the input 12, and an HSW of the HSW is supplied to the input 13. A switching signal (hereinafter referred to as 1 / 2HSW) with a doubled cycle is supplied and output
Recording control signal after duty conversion to 14 (hereinafter RE
C CTL (OUT) is output and supplied to the control head (hereinafter referred to as CTL head). The reproduction control signal (hereinafter referred to as PB CTL) is supplied to the input 21 of the back tray discriminator 2, HSW is supplied to the input 22, 1 / 2HSW is supplied to the input 23, the cycle reference I is supplied to the input 25, and the output twenty four
An acceleration command signal is output from 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 and is supplied as a capstan control signal (E _CAP ). HS on input 42 of cycle reference generation timer 4
W is supplied, 1/2 HSW is supplied to the input 43, and the period reference I is generated at the output 41.

The operation of the conventional magnetic recording / reproducing apparatus configured as described above will be described below.

(1) During recording, as shown in Fig. 4, HSW (a) and 1 / 2HS
The phase relationship of W (b) is specified, and these two signals are passed through the duty converter 1 to RECCTL (OUT) (c)
To get That is, HSW (a) is high level (H), 1 / 2HSW
For one frame in which (b) starts at HIGH level (H), the duty of RECCTL (OUT) is REC CTL (OUT) for one frame starting with HSW (a) at (H) and 1 / 2HSW (b) at LOW level (L).
Duty is Is. REC CTL (OUT) is supplied to the CTL head and recorded.

(2) During playback, HSW (a), 1 / 2HSW as shown in Fig.5
(B) has the same phase relationship as in FIG. 4, these two signals are input to the back-tra discriminator 2, and the phase reference signal (d) is
It is created inside the back tiger discriminator 2. That is, the first
It becomes a table relationship.

Further, the period reference (e) is generated from the period reference generation timer 4 for HSW (a) and 1 / 2HSW (b). here
T ₁ indicates the pulse width corresponding to about 62.5% of the time for the PB CTL cycle.

When PB CTL (f) is in the state shown in FIG.
The REC CTL (OUT) (c) and the phase of one frame are shifted, and it is in a so-called back tracking reproduction state.
H period of PB CTL (f) with respect to the above cycle reference (e) ▲
After determining that ▼ is longer than T ₁ , the rising edge immediately after one frame of a ₁ b ′ ₁ a ₂ (duty ratio 65:35) of PB CTL (f) with respect to the phase reference signal (d). a
Depending on whether the _two phases are in the L or H period, it is possible to determine whether the tracking during reproduction 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 reverse or the front as described above, in the case of the reverse tiger reproduction, an acceleration command is output from the reverse tiger discriminator 2 and is input to the acceleration pulse generator 3 to accelerate the acceleration pulse (g). Is generated and supplied as a capstan control signal E _CAP to accelerate the capstan. FIG. 5 (h) shows the state of accelerated PB CTL (acceleration), and the acceleration pulse (g) is obtained by accelerating the capstan about 1.3 times for a certain period of time, for example, about 2 frame periods. As shown in PB CTL (acceleration) (h), forcibly accelerating to run for about 3 frames in 2 frame periods, and reverse tracking reproduction is shifted to front tracking reproduction. At the end of the acceleration pulse (g), the state is almost close to the table tracking, and then the normal servo system pulls the table tracking reproduction. However, during table tracking reproduction, no acceleration pulse is naturally generated.

Problems to be solved by the invention The back or front of the playback tracking is determined by the establishment of 1/2 at the start of the playback mode, but immediately after the start of playback, it is generally 60:40 due to the rising state of the capstan rotation. Set the duty (▲ ▼) to T ₁ (62.5
%), It may be erroneously discriminated, and as a result, there is a disadvantage that front tracking is shifted to back tracking.

The present invention solves the above-mentioned problems, and an object of the present invention is to provide a magnetic recording / reproducing apparatus capable of accurately preventing the occurrence of back tracking without causing a malfunction such as shifting front tracking to back tracking.

Means for Solving the Problems In order to achieve the above object, the magnetic recording / reproducing apparatus of the present invention generates a second cycle reference in a frame different from the first cycle reference. Is provided with a cycle reference generation timer.

Effect As described above, the present invention adds the second period discrimination timer II to the conventional example, and correctly discriminates the back tiger reproduction when the reproduction control signal becomes stable after the reproduction is started. Can be able to

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 illustrating the operation of the magnetic recording / reproducing apparatus according to the embodiment of the present invention. In FIG. 1, the same components as those in FIG. 3 are designated by the same reference numerals, and detailed description thereof will be omitted. Also, in FIG. 2, the same symbols are assigned to the same signals as in FIG.

In the figure, REC is applied to the first input 11 of the duty converter 1.
CTL (IN), 2nd input 12 HSW, 3rd input 13 1 / 2HSW
REC CTL (OU
T) is output. PB is used as the first input 21 of the back tiger discriminator 2.
CTL, HSW is supplied to the second input 22, 1/2 HSW is supplied to the third input 23, and the first cycle reference I is supplied to the fourth input 25 from the cycle reference generation timer I4. Supply,
A second cycle reference II is supplied to the fifth input 26 from the cycle reference generation timer II5 and an acceleration command signal is obtained at 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 as a capstan control signal E _CAP .

Now, supply HSW to the input 42, supply 1 / 2HSW to the input 43 and output 4 of the above-mentioned first periodic reference generation timer I4.
The period reference I is generated at 1. Also, HSW is supplied to the input 52 of the second cycle reference generation timer II5 and 1 / 2HSW is supplied to the input 53.
To produce the period reference II at output 51.

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 the drawings.

(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 connected to the CTL head and recorded.

(2) At the time of reproduction, as shown in FIG.
The cycle reference generation timer II of is added, and as shown in FIG. 2, for the HSW (a) and 1 / 2HSW (b), the cycle reference II
(E) 'is generated. After it is judged that the H period ▲ ▼ of PB CTL (f) is shorter than T _{1 with} respect to the cycle reference II (e) ′, the H period of the next frame ▲
It is determined that ▼ is longer than T _{1 with} respect to the cycle reference (e), and thereafter, the front and back of the tracking are determined with respect to the phase reference (d) in exactly the same manner as the conventional example described above, and in the case of the back tiger. Performs the capstan acceleration to reversely shift the capstan phase from the back tiger reproduction to the front tiger reproduction.

As described above, according to this embodiment, the cycle reference generation timer I4
The cycle reference generation timer II5 and the cycle reference I
And the cycle reference II are alternately output to different frames, and the back tracking reproduction discriminator 2 generates the cycle reference in a state where the reproduction control signal is shorter than the cycle reference II and the rotation of the capstan is stable. Since the back tracking reproduction is determined based on the output of the timer I4, the back tracking reproduction determination can be performed without malfunction even when there is unevenness in the operation at the start of the operation of the capstan.

According to the present invention, the first cycle reference output by the first cycle reference timer and the second cycle reference output by the second cycle reference timer.
The frame reference is alternately output for each frame, and the back tracking reproduction discriminator makes the discrimination, so that the back tracking discrimination is performed after the reproduction control signal becomes stable even when the capstan drive is started. Therefore, the determination is performed without malfunction. Therefore, it is possible to prevent the jitter due to the back tracking reproduction and improve the 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 an operation timing chart at the time of reproducing 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 apparatus, FIG. 5 is an operation timing chart at the time of reproduction in the conventional example, and FIG. 6 is a recording pattern chart of the VHS system. 1 ... Duty converter, 2 ... Back tracking reproduction discriminator, 3 ... Acceleration pulse generator, 4 ... First cycle reference generator, 5 ... Second cycle reference generator.

Claims (1)

[Claims] 1. A first, a second and a third input section and a first output section, wherein a first recording control signal is supplied to the first input section and a second input section is supplied. A head switching signal is supplied, a 1/2 head switching signal having a cycle twice that of the head switching signal is supplied to the third input unit, and the duty-converted first and second head switching signals are supplied to the first output unit. A recording control signal duty converter for generating a repetitive signal of the second recording control signal and supplying it to the control head, and a fourth, fifth, sixth, seventh and eighth input section and a second output section, A reproduction control signal is supplied to the fourth input section, the head switching signal is supplied to the fifth input section, and the sixth input section is supplied with the head switching signal.
1/2 head switching signal is supplied, the seventh input section is supplied with a first cycle reference, the eighth input section is supplied with a second cycle reference, and the second output section is supplied. Has a back tracking reproduction discriminator for generating an acceleration command signal, a ninth input section and a third output section, and supplies the acceleration command signal to the ninth input section to output the third output. Section has an acceleration pulse generator for generating a capstan acceleration pulse to supply a capstan control signal, a tenth and eleventh input section and a fourth output section, and the tenth input section includes the head. A switching signal is supplied, the ½ head switching signal is supplied to the eleventh input portion, and the head switching signal HI is supplied to the fourth output portion based on the first cycle reference.
A first cycle reference generation timer that is generated at a GH level during the frame period in which the 1/2 head switching signal starts at a LOW level, and a twelfth, thirteenth input section and a fifth output section
The head switching signal is supplied to the twelfth input section, the 1/2 head switching signal is supplied to the thirteenth input section, and the second cycle reference is supplied to the fifth output section. When the head switching signal is HIGH level
A magnetic recording / reproducing apparatus comprising: a second cycle reference generation timer which is generated in a frame period in which a 1/2 head switching signal starts at a HIGH level.