JPH0664721B2 - Pilot signal recording / reproducing method - Google Patents

Description

The present invention relates to a method for recording / reproducing a pilot signal in a video tape recorder (VTR) having a function of displacing a recording / reproducing head in a rotation vertical direction.

(B) Conventional Technology In a standard called 8 mm video, a tracking method is defined as an option, which allows a recording / reproducing (R / P) head to be displaced in a rotation vertical direction by a bimorph or the like. With this tracking method, R /
In order to control the position of the P head in the vertical direction of rotation, a pilot signal (usually referred to as ₅ and 230 KHz as shown in FIG. 7 is used.
With a frequency of 1) is used.

That is, when the R / P heads opposed to each other by 180 degrees supported by a bimorph are attached to the rotating cylinder and the tape is wound about 221 degrees around the cylinder, the PCM area (1) and the video area (2) are The pilot signal ₅ is recorded / reproduced during a predetermined period (3).

In the figure, arrow A indicates the tape running direction, and arrow B indicates the head rotating direction. Further, this pattern shows the case where the tape running speed is 14.345 mm / sec, and αH is 1H. Tracks (a ₁ ), (a ₂ ), and (a ₃ ) are tracks recorded in one of the heads (a), (b ₁ ), (b
₂ ) and (b ₃ ) are recorded at the other head (b).

The pilot signal ₅ is recorded by the R / P head (a),
It is recorded for a period of 1H from a predetermined position from the bottom edge of the tape. Immediately after that, the R / P head (a) is in the reproducing state for the 1H period, and the crosstalk of the pilot signal ₅ of the track (for example, (b ₁ )) previously recorded by the head (b) is reproduced. The level of the crosstalk signal obtained on the track (a ₂ ) and the level of the crosstalk signal reproduced on the stored track (b ₁ ) are compared to determine the direction of rotation of the R / P head (arrow C in the figure). ) Position control is performed. The part indicated by the broken line is the part from which the crosstalk signal can be taken out.

Now, in order to enable recording for a longer time on a VTR, a method of reducing the tape running speed during recording is usually adopted. At this time, αH also decreases, and, for example, when the tape traveling speed is 1/2 (7.1725 mm / sec) of the above case, αH also becomes 0.5H. FIG. 8 shows a case where the tape running speed is halved.

At this time, the track pitch is halved, but the 1H period is the same as in the case of FIG. 7, and the pilot signal ₅ is applied.
When recording for 1H period after the PCM area (1) and reproducing for 1H period immediately after that, the crosstalk signal can be derived only in the portion indicated by the broken line. That is, the period during which the crosstalk signal can be taken out is shorter than in the case of FIG.

Further, when the R / P head is switched from the recording state to the reproducing state, the reproducing signal can be taken out only at a point slightly after the start of the reproducing state, so that the period during which the crosstalk signal can be obtained is further shortened. It is difficult to derive a control signal for controlling the position of the / P head in the rotational direction without error.

In consideration of this point, Japanese Patent Application Laid-Open No. 58-139328 discloses, as shown in FIG. 4 or FIG. 13 of the publication, a pilot signal ₅ for a predetermined period irrelevant to .alpha.H recorded in the immediately preceding track.
A technique is described in which a short time R / P head of a period of scanning adjacent to a recording section is set to a reproducing state.

However, as described above, even if the R / P head is in the reproduction state, the crosstalk signal cannot be obtained immediately,
If the reproduction period is shortened, there is a possibility that a sufficient crosstalk signal cannot be obtained.

(C) Problems to be Solved by the Invention As described above, in the prior art, when the tape running speed is reduced to lengthen the recording time, the rotational vertical position control of the R / P head is performed. Therefore, there is a possibility that a sufficient crosstalk signal may not be obtained, and thus the position control of the R / P head may malfunction.

(D) Means for Solving the Problems In the present invention, the recording / reproducing timing of the pilot signal ₅ is controlled with four consecutive tracks as one cycle. The recording period and the reproducing period are equal, and this is indicated by G. Further, the upper limit timing of the recording / reproducing area of the pilot signal ₅ is S. In the first track Record the pilot signal ₅ for the period G from the timing of From the timing of, the R / P head is set to the reproduction state for the period G. In the second track, the pilot signal ₅ is recorded from the timing of (S-3G), and the reproduction state starts from the timing of (S-2G). In the third track From the timing of, the R / P head is in the replay state, From the timing of, the pilot signal ₅ is recorded for the period G only. In the fourth track, the pilot signal ₅ is recorded for a period G from the timing of (S-2G), and (S-
The reproduction state starts from the timing of G). After that, the same operations as the first to fourth tracks are repeated. Also, the recording period and the reproducing period G are changed according to the tape running speed,
= K · αH (K is a constant).

(E) Assuming that the operation recording period and reproduction period G (= K · αH), the period T during which the crosstalk signal can be taken out is K ≦ 2.
At the time of , And when K> 2, Indicated by. Therefore, by changing the recording and reproducing period G with respect to αH, it is possible to set the period during which the crosstalk signal can be taken out to a desired value.

(F) Example First, the principle will be described with reference to the drawings. FIG. 5 is a diagram showing the arrangement of the recording period (R) and the reproducing period (P) of the pilot signal ₅ , and the reference numerals such as (Rn) indicate that they correspond to the nth track. Also, this arrangement is the first
~ The combination of the fourth track is one cycle.
With the arrangement shown in FIG. 5, the recording and reproduction are reversed at the third track, so the period during which the crosstalk signal can be taken out is always equal to the recording period and the reproduction period G.

Next, the relationship between the period G and αH can be considered as shown in FIG. That is, the pilot signal ₅ has a period (P ₄ )
It is arranged between the line (11) connecting the end (10) of the and the line (13) connecting the starting end (12) of the period (R ₂ ). It is considered that the length (A) corresponds to αH. Therefore, the period G is equal to 2αH (K = 2). On the other hand, the area (B) regarding the pilot signal ₅ becomes equal to the 3G period.

Next, the timing of the actual tape pattern will be obtained based on FIG. In the figure, arrow A indicates the tape running direction, and arrow B indicates the head scanning direction. Area (1) is an area for PCM recording and area (2) is an area for video signals.
An area (corresponding to the 3G period) (20) for the pilot signal ₅ is set between them. Consider the start timing (S) of the video area (2) indicated by the chain line (21) as a reference.
(However, (S) is defined as the timing from the lower end (22) of the tape.) In the fourth track (T ₄ ), since the end of the reproduction period (P ₄ ) coincides with (S), reproduction is performed. The period (P ₄ ) is started at the timing of (S-G), and similarly, the recording period (R ₄ ) is started at the timing of (S-2G). In the first track (T ₁ ), the reproduction period (P ₁ ) is shorter than that in the fourth track (T ₄ ). The timing and recording period (R ₁ ) Will be started at the timing of.

In the second track (T ₂ ), since the start timing of the recording period (R ₂ ) coincides with the start of the pilot signal ₅ area corresponding to the time width 3G, the recording period and the reproducing period (R ₂ ) (P ₂ ) The start timing of each is (S-3G),
(S-2G). In the third track (T ₃ ), the reproduction period (P ₃ ) is shorter than that in the second track (T ₂ ). At the timing of, the recording period (R ₃ ) Will be started at the timing of.

The portion indicated by the broken line shows the period T during which the crosstalk signal can be taken out as in FIG. 7, and in the case of FIG. 1, the period T is equal to 2αH.

Next, start the recording period of the pilot signal in each track,
And the timing of starting the reproduction period is the same as in the first case, but the relationship between the period G and αH is different, that is, G = K ·
Consider the case where K ≠ 2 at αH.

FIG. 2 shows the case of K = 1.5 (<2). In this case, the period T shown by the broken line is obtained by subtracting the start timing of the recording period of the immediately preceding track from the timing of the end of the reproduction period (P ₁ ), for example. That is, Becomes

FIG. 3 shows the case of K = 2.5 (> 2). In this case, the start end of the reproduction period (P ₁ ) of the first track (T ₁ ) may be subtracted from the end of the recording period (R ₄ ) of the fourth track (T ₄ ). Ie When K = 2, both equations are the same.

FIG. 4 shows the configuration of an apparatus for realizing FIGS. 1 to 3. In order to realize it, VTR at the timing shown in Figs.
It is sufficient to create a recording gate signal and a reproduction gate signal for setting the pilot signal _{5 in the} recording state and the reproducing state.
In FIG. 4, (30) is an input terminal of the RF switching pulse which is a reference signal indicating the rotation phase of the rotation head, and (3)
1) is a gate signal generation circuit that creates each gate signal based on the RF switching pulse, and (32) and (33) are reproduction gate signals by selecting the output of the gate signal generation circuit (31) based on the RF switching pulse. (34) and the recording gate signal (35) are first and second switching switches for sequentially deriving.

Since the start edge (S) of the video area is specified by the timing from the rising edge and falling edge of the RF switching pulse, the timing of each gate signal is also the delay amount from the rising edge and falling edge of the RF switching pulse. It is possible to easily create a gate signal having a width G defined by That is, from the terminal (31a) is delayed from the edge of the RF switching pulse, A gate signal whose H level is equal to that of the G period is obtained. Similarly, the rising timing from the terminal (31b) is (S-2G), and from the terminal (31c) , A (S-G) timing from the terminal (31d), and a (S-3G) timing gate signal from the terminal (31e). The predetermined delay from the RF switching pulse can be easily achieved using monomulti.

The first and second switching switches (32) (33) are sequentially switched based on the RF switching pulse, and the terminal (P ₁ ) (R ₁ ) is selected during recording of the first track.

Next, consider the tape traveling speed shown in FIGS. 7 and 8. In the case of FIG. 8, αH = 0.5H. At this time, in order to set T = 1H, it suffices that G is equal to the 1H period from equation (2) (hence K = 2). Therefore, even if the tape running speed decreases and αH decreases, a sufficient period for extracting the crosstalk signal can be taken.

Also, in the case of αH = 1H shown in FIG. 7, T =
In order to set it to 1H, it is sufficient to set G = 4 / 3H from (1), and the region (20) at this time is equal to the 4H period. Therefore, in both the case of FIG. 7 and the case of FIG. 8, a sufficient area (20) is provided in front of the video area, and the G of the gate signal generating circuit is controlled by an appropriate control signal according to the tape running speed. The value of may be changed.

(G) Effect of the Invention As described above, according to the present invention, the period during which the crosstalk signal can be taken out can be set to be sufficiently long even when the tape running speed decreases and αH becomes small. It is possible to prevent the malfunction of the position control of the head in the vertical direction of rotation of the head.

[Brief description of drawings]

1, 2 and 3 are diagrams showing a track pattern of the present invention, and FIG. 4 is a block diagram of a gate signal generating circuit,
5 and 6 are explanatory diagrams for explaining the principle of the present invention. FIG. 7 and FIG. 8 are diagrams showing track patterns in the prior art. The (n + 1) th to the (n + 4) th track ... (T ₁ ) (T
₂ ) (T ₃ ) (T ₄ ), Pilot signal recording period ...
(R ₁ ) (R ₂ ) (R ₃ ) (R ₄ ), pilot signal reproduction period ... (P ₁ ) (P ₂ ) (P ₃ ) (P ₄ ).

Claims (1)

[Claims] 1. When a signal is recorded on a tape by using a plurality of heads which can be displaced in the vertical direction of rotation, a scanning timing at which the recording of the signal is started on a track formed on the tape is defined as (S). , G from the pilot signal recording period, G from the timing of (S- (5/2) G) in the (n + 1) th (n is an integer) track.
The pilot signal is recorded for a period of time and the nth period of the following G period.
The head forming the + 1st track is set to the reproduction state, and the pilot signal is recorded for the G period from the timing (S-3G) at the (n + 2) th track, and the n + 2th track is formed for the subsequent G period. The head is in a reproducing state, and in the (n + 3) th track, from the timing of (S− (5/2) G) to the Gth period.
The head forming the + 3rd track is set to the reproducing state, the pilot signal is recorded for the subsequent G period, and the nth + 4th
In the second track, the pilot signal recording / reproducing method in which the pilot signal is recorded for the G period from the timing of (S-2G), and the head forming the (n + 4) th track for the subsequent G period is brought into a reproducing state.