JP2005216388A - Tracking control method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a tracking method capable of obtaining a correct tracking adjusting position when an optimal tracking position is changed during tracking adjustment or an optimal adjusting position is mistaken due to noise or the like. <P>SOLUTION: During tracking adjustment, a maximum ENV(envelope value) is compared with the ENV of a best position in a step S13. When a difference between the two values is equal to or more than a prescribed value, tracking adjustment is carried out again. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a tracking control method for executing tracking control by controlling a relative phase between rotation of a cylinder to which a rotary head is attached and feeding of a magnetic tape in a helical scan type magnetic recording / reproducing apparatus.

  In the helical scan type magnetic recording / reproducing apparatus (VCR), a control signal recorded in synchronization with a reference signal is recorded in the longitudinal direction of the magnetic tape, and at the time of reproduction, the reproduced control signal, that is, the tracking phase and the rotation of the cylinder Auto tracking adjustment is performed to adjust the relative phase relationship.

  This shifts the relative phase between the control signal and the cylinder rotation reference signal during playback, searches for the tracking phase where the envelope obtained from the rotary head is maximized, and plays back at that phase. In this way, the servo is applied to the rotation of the cylinder or the feeding of the magnetic tape, and this is particularly effective when reproducing a magnetic tape recorded by another video tape recorder whose X value is shifted.

FIG. 5 shows a conventional auto-tracking control device.
1 is an envelope acquisition unit including an A / D conversion unit, 2 is a tracking control unit that controls the tracking phase, 3 is a servo unit that controls the phase, 4 is a memory unit that stores the acquired envelope value, and 5 is an envelope A Δ calculation unit for calculating the value of the difference Δ, 6 is a cylinder, 7 is a capstan motor, 8 is a tape, and 9 is an A / C head. The envelope acquisition unit 1, the tracking control unit 2, the servo unit 3, the memory unit 4, and the Δ calculation unit 5 are configured with a microcomputer as a main part.

The operation will be described with reference to FIG.
If the envelope values at the positions of the operating points 1, 2, 3, 4, and 5 are y1, y2, y3, y4, and y5, the difference between y1 and y2 at that time, Δy1_2, is calculated, and in the same manner, Δy2_3, Δy3_4 Is calculated according to the change of the tracking position.

  At this time, when the value of each Δ is equal to or less than a predetermined value, it is assumed that the change in the output of the envelope is reduced, and the peak is m of the peak of the envelope. Here, the operating point 4 corresponds to this. Then, the shift of the tracking position is advanced as it is, and conversely, the point where the value of Δ is equal to or greater than the specified value is set as the end point of the mountain top section m. Here, the operating point 6 corresponds to this.

  Then, the value of the tracking position ma intermediate between the tracking position m4 of the operating point 4 and the tracking position m6 of the operating point 6 is set as the best tracking adjustment position, and reproduction is performed at this tracking position.

  Here, changing the tracking position shifts the phase of a signal (hereinafter referred to as HSW signal) synchronized with the rotation of the cylinder 6 and a control signal (hereinafter referred to as CTL signal) output from the A / C head 9. Thus, the position of the reproducing head (rotating head) with respect to the recording track can be turned on track as shown in FIGS. 6B to 6A.

This is illustrated in FIG.
In FIG. 8, the phase control is performed by the time N from the rising edge of the HSW signal to the rising edge of the CTL signal. At the time of tracking adjustment, for example, this time N is intentionally controlled by controlling the rotation of the cylinder 6. Change the tracking position.

  Here, the relationship between the HSW signal and the CTL signal goes around once in one cycle of the HSW signal. Normally, at the time of tracking adjustment performed in advance before reproduction, by changing the time N, as described above, the peak portion of the envelope is detected and the midpoint of the peak portion is taken as the best point, and the best point Perform normal playback at.

FIG. 9A and FIG. 9B show the relationship between the tracking position and the head trace (not shown) of the cylinder 6.
FIG. 9A shows a case where the tracking is at the best position with respect to the recording track, and the head trace is in the best state. On the other hand, FIG. It shows a state where the head trace is deviated from the best position.

The tracking adjustment is to make the head trace position shown in FIG. 9A the best point by changing the time N shown in FIG. Therefore, when the tracking value is deviated, the head trace deviates from the recording track, and the output envelope value becomes small, resulting in a noisy video.
Japanese Patent Laid-Open No. 7-110987 JP-A-5-62427 Japanese Examined Patent Publication No. 6-73209

In the conventional tracking adjustment method, an adjustment failure may occur in the following cases.
In particular, overshooting is frequently performed at the beginning of the tape, etc.In this case, when overtaking is performed on a tape that has already been recorded, the recorded tracking position changes during tracking adjustment, and the best point is obtained. Cannot adjust.

This will be described with reference to FIG.
In the pattern of FIG. 10, when tracking adjustment is started from the start position, the envelope change Δ from the operating point a becomes less than the specified value, and conversely at the operating point d, the envelope change Δ exceeds the specified value. The section between a and the operating point c is determined to be the peak top section, and the operating point b is calculated as the best tracking point. The tracking adjustment is completed by detecting the operating point d necessary for determining the operating point c, and moves to the operating point b to end the tracking position.

  However, in this case, the overlap is performed, and the actual tracking best point should be the operating point e from the figure, and the envelope obtained when the tracking position is adjusted to the operating point b is the operating point It becomes the value of f and is not the best point.

  This is a poor adjustment every time, for example, when playback is always started from the same tape location, such as at the beginning of the tape, or when the overshoot portion is played back at the same timing during tracking adjustment. . If the tape is scratched or a noisy tape such as an old demagnetizing tape, a point corresponding to the operating point b may appear in the same way, and an erroneous determination of the tracking best point may occur.

  Here, tracking adjustment can be prevented if it is always determined by a change for the entire area (one cycle of the HSW signal), but in that case, not only adjustment is required, but also the noise screen continues for a long time due to the movement of tracking. Such an adjustment by tracking movement for one cycle of the HSW signal every time cannot be performed until a normal recording state occurs because of screen noise at the time of tracking adjustment.

  In addition, an automatic tracking method is used in which the envelope value is monitored after a certain period of time after the end of tracking adjustment, and the envelope value falls below the specified value. In order to prevent malfunctions due to, etc., it must be set to detect only when the envelope lowering level is large, and it takes time to detect the adjustment position incorrectly. There is a disadvantage that a noise screen appears for a long time before entering and adjusting.

  SUMMARY OF THE INVENTION An object of the present invention is to provide a tracking control device that can quickly and correctly perform tracking adjustment even when an overshoot portion or a noisy portion is reproduced during tracking adjustment.

  The tracking control device of the present invention compares again the maximum value of the envelope stored at the time of tracking adjustment and the envelope at the best point after detecting the mountain interval, and immediately performs the tracking adjustment again when there is a difference greater than a specified value. It is characterized by.

  The tracking control method according to claim 1 of the present invention is a helical scan type magnetic recording / reproducing apparatus in which a control signal is recorded in the longitudinal direction of a magnetic tape and recording data is picked up by a rotary head from a recording track of the magnetic tape during reproduction. When adjusting the relative phase relationship between the control signal reproduced from the magnetic tape and the rotation of the rotary head, a difference in envelope size between the previous tracking position and the current tracking position is detected, Detects an interval where the difference in magnitude is less than the specified value and executes tracking control with the midpoint of that interval as the optimum adjustment position, and after moving to the optimum adjustment position and the maximum value of the envelope being adjusted Compare the optimum position envelope values of the When Tsu is characterized by re-executing the tracking control.

  The tracking control method according to claim 2 of the present invention is the tracking control method according to claim 1, wherein the difference between the envelope at the current position before the completion of tracking control and the maximum value of the envelope during the current tracking control adjustment exceeds a specified value. In this case, the tracking control is re-executed so as to re-acquire the maximum value of the envelope during the tracking control adjustment, and when the difference is less than the specified value, the maximum value of the envelope during the tracking control adjustment is used to perform the tracking control. Control is executed.

  According to the tracking control method of the present invention, it is detected that the adjustment is not correct even when the tracking position changes due to overshooting or the like, especially when a change occurs at the start end or noise occurs during the adjustment. Since the adjustment is performed again, correct tracking adjustment can be performed, and a noise-free image can be obtained during normal reproduction.

Hereinafter, the tracking control method of the present invention will be described based on specific embodiments. In addition, the same code | symbol is attached | subjected and demonstrated to the thing similar to FIG. 5 which showed the prior art example.
(Embodiment 1)
FIG. 1 shows a helical scan type magnetic recording / reproducing apparatus employing the tracking control method of the present invention. The tracking control apparatus has a microcomputer as a main part, an envelope acquisition part 1, a tracking control part 2, a servo part 3, and a memory part 4. , Δ calculation unit 5 and comparison unit 11.

The comparison unit 11 compares the MAX envelope with the best point envelope.
During normal reproduction, the rotation speeds of the capstan motor 7 and the cylinder 6 are controlled by the HSW signal from the cylinder 6 and the CTL signal from the A / C head 9 so that the time N shown in FIG. Controlled by the unit 3. The method for changing the tracking position at the time of tracking adjustment is as already described.

The operation of the tracking control according to the present invention will be described with reference to FIG.
The envelope is acquired while sequentially changing the tracking position from the tracking start position, and the envelope change Δ shown in the figure is calculated. Then, a point between the point a where Δ is equal to or less than the predetermined value and a point c where the change starts to be more than a certain value is determined as the peak top section, and the midpoint b between the two points is set as the best tracking point. At that time, the value of the envelope MAX detected during the adjustment (the value yb at the point b in FIG. 2A) is stored. Then, when the point d is reached and the detection of the mountain top section is completed, the tracking position is changed to the best point b. At this time, the envelope at point b is detected again. Then, x = yb−yf is calculated, and when x is equal to or greater than a predetermined value, it is determined that adjustment has failed due to overshooting or noise, and tracking adjustment is resumed from the position of point b again.

FIG. 3 is a flowchart of the main part of the microcomputer, and the tracking control method will be described in detail based on this flowchart.
After the tracking adjustment is started, it is checked in step S1 whether or not the first tracking adjustment is started. In the first adjustment start, the tracking position is moved by an amount determined as a default value, and then the envelope value of the tracking position is acquired in step S2.

  If it is determined in step S1 that it is not the first adjustment start, the tracking position is moved by the amount determined in step S3. Usually, a movement amount of about 50 to 80 divisions in one cycle of the HSW signal is used. After the movement, the envelope value of the tracking position is acquired in step S2.

  In step S4 following step S2, it is checked whether the difference between the previous envelope value (previous ENV) and the current acquired envelope value (current ENV) is less than or equal to n.

  If it is determined in step S4 that n is exceeded, the process returns to step S1. If it is determined in step S4 that it is n or less, the left shoulder of the mountain top section (point a in FIG. 2A) is determined in step S5, assuming that the mountain top section has been entered.

  Next, in step S6, it is checked whether the left shoulder has been determined. If it is determined in step S6 that the left shoulder has not been determined, the process returns to step S1. If it is determined in step S6 that the left shoulder is determined, the previous ENV is compared with the current ENV in step S7.

  If it is determined in step S7 that the current ENV is larger than the maximum envelope value, the maximum envelope value (maximum ENV) is updated in step S8, and step S9 is executed. If it is determined in step S7 that the current ENV is not greater than the maximum value of the envelope, step S9 is skipped and step S9 is executed.

  In step S9, the previous ENV and the current ENV are compared, and it is checked whether the previous ENV is larger than the current ENV by a predetermined value n or more. If it is determined in step S9 that the difference between the previous ENV and the current ENV is less than n, the process returns to step S1.

  If it is determined in step S9 that the previous ENV has become n or more greater than the current ENV, the right shoulder of the mountain top section (point c in FIG. 2A) is determined in step S10, and the best point in step S11. b is obtained by calculation. In this case, as for the point b, an intermediate point between the points a and c is calculated. After the tracking position is moved to the best point, the envelope value (yf in FIG. 2A) at the best point is obtained in step S12.

  In step S13, a comparison is made with the maximum ENV that has already been acquired and updated (yb in FIG. 2A), and it is checked whether the difference between yb and yf is greater than or equal to the specified value p. If it is determined in step S13 that the specified value is greater than p, it is determined that the adjustment has failed. After setting the adjustment failure in step S14, the process returns to step S0 and again from the current position (best point position). , Resume adjustment.

  The adjustment failure setting is specifically performed by erasing the maximum ENV stored value, erasing the right shoulder position and left shoulder position, incrementing the number of times of failure, and the like. If it is detected in step S14 that the number of failures incremented by the adjustment failure setting has reached the specified value, the tracking adjustment is terminated without returning to step S0, and the trace is returned to the default center position and traced as it is. It is configured as follows.

  In step S13, when the difference is less than p, it is determined that the tracking adjustment is successful, and the adjustment ends in step S15. In this case, the adjustment failure can be detected with a value smaller than the comparison value between the maximum ENV used for automatic tracking and the current ENV after the adjustment is completed. This is because normal reproduction is being performed, and it is necessary to increase the comparison value in order to prevent malfunction due to small noise or the like. However, in the method of the present invention, determination is performed only within a limited time during tracking adjustment. Therefore, it is difficult to malfunction, and conversely, if noise is generated during tracking adjustment, there is a high possibility that tracking adjustment cannot be performed correctly, and adjustment should be performed again.

(Embodiment 2)
FIG. 4 shows a flowchart of (Embodiment 2) in place of the flowchart shown in FIG. 3 of (Embodiment 1).

  In the flowchart of FIG. 3, step S10 is executed after step S9. However, in the flowchart of FIG. 4, step S9-a is added between step S9 and step S10 in the flowchart of FIG. The only difference is that

  In step S9-a, it is checked whether the difference between the maximum ENV and the current ENV is equal to or less than a specified value p1. Only when it is determined in step S9-a that the difference is equal to or less than the specified value p1, the routines after step S10 are executed.

  When it is determined in step S9-a that the difference exceeds the specified value p1, the envelope is output to the point cc smaller than the specified value p1 next to the point b as shown in FIG. 2B. In this case, even if step S10 and subsequent steps are executed as they are, the best point is determined as the best point even if an attempt is made to calculate the best point. Therefore, the occurrence of such a state is determined before step S10 and subsequent steps. -A is detected, and step S14 is executed to re-acquire the maximum value of the envelope during the tracking control adjustment and re-execute the tracking control.

  By executing step S9-a in this way, a tracking malfunction can be avoided.

  The tracking control method of the present invention can be used for processing various data using a helical scan type magnetic recording / reproducing apparatus and a helical scan type magnetic recording / reproducing apparatus.

Configuration diagram of a helical scan type magnetic recording / reproducing apparatus employing the tracking control method of the present invention Relationship diagram between tracking position and envelope output for operation explanation Flowchart of (Embodiment 1) of the present invention The flowchart of (Embodiment 2) of this invention Block diagram of a conventional tracking control device Illustration of tracking adjustment Operation explanatory diagram of a conventional tracking control device Illustration of tracking phase Explanatory drawing of the state where the trace is the best for the recording track and the tracking adjustment Operation explanatory diagram at the time of poor adjustment of the conventional tracking control device

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Envelope acquisition part 2 Tracking control part 3 Servo part 4 Memory part 5 Envelope difference calculation part 6 Cylinder 7 Capstan motor 8 Tape 9 A / C head 10 A / D conversion part 11 Comparison part

Claims (2)

In a helical scan type magnetic recording / reproducing apparatus in which a control signal is recorded in the longitudinal direction of a magnetic tape and recording data is picked up by a rotary head from a recording track of the magnetic tape at the time of reproduction, the control signal reproduced from the magnetic tape and the When adjusting the relative phase relationship with the rotation of the rotary head,
Detects the difference in envelope size between the previous tracking position and the current tracking position, detects the section where the difference is less than the specified value, and sets the midpoint of that section as the optimal adjustment position In addition to executing control, the maximum value of the envelope being adjusted is compared with the optimum position envelope value after moving to the optimum adjustment position.If the optimum envelope is less than the specified value from the maximum value, the tracking control is performed. Tracking control method to be re-executed. When the difference between the envelope at the current position before the completion of tracking control and the maximum value of the envelope during the current tracking control adjustment exceeds the specified value, the maximum value of the envelope during the tracking control adjustment is reacquired. Re-execute tracking control,
The tracking control method according to claim 1, wherein when the difference is less than a specified value, the tracking control is executed using a maximum value of an envelope during tracking control adjustment.

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