JP3175432B2 - Tracking control device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a helical scan type magnetic recording / reproducing apparatus, and more particularly to a tracking control apparatus for adjusting a tracking phase using characteristic data of a reproduction envelope level of a reproduction signal with respect to a tracking phase. Things.

[0002]

2. Description of the Related Art Generally, a video tape recorder (hereinafter, referred to as VTR) used for recording a video signal is different from a VTR used for reproducing a video signal, or the same VTR is used for recording and reproduction. However, if the magnetic tape expands due to an environmental change or the like, the position of the rotary head is shifted from the position of the helical track formed on the magnetic tape, and the envelope level of the reproduced signal is reduced. Therefore, this affects the reproduced image.
In such a case, it is necessary to adjust the tracking phase so that the position of the rotary head matches the position of the helical track recorded and formed on the magnetic tape.
Therefore, it is important to optimize the tracking phase.

Conventionally, a tracking phase, which is a phase of a reproduction control signal with respect to a reference signal, is gradually changed to detect an envelope level of a video signal reproduced from a rotary head, and to obtain a tracking phase at which the envelope level becomes maximum. A tracking control device that performs matching is proposed.

[0004]

However, in the above-described conventional tracking control device, the step of changing the tracking phase is made fine in order to improve the tracking accuracy. Therefore, there is a problem that the time required for the tracking operation becomes long.

FIG. 2A is a graph showing characteristics of an envelope level with respect to a tracking phase when a head width of a rotary head used for reproduction is wider than a track width of a helical track formed on a magnetic tape. .
FIG. 2B is a diagram showing a relative position between the helical track and the rotary head in each tracking phase. The helical track 202 is a track that the rotary head 201 should scan originally, and has the same azimuth angle as the rotary head 201. Has been recorded. Further, since the helical track 203 is recorded at an azimuth angle different from that of the rotary head 201, the reproduction envelope level from this track decreases due to azimuth loss. Also,
The helical track 204 is not originally a track to be scanned by the rotary head 201, but is recorded at the same azimuth angle as the rotary head 201, so that the reproduction envelope level from this track becomes high. In this way, when the head width of the rotary head is wider than the track width of the helical track, the optimum tracking phase is determined by considering the factors such as the helical track bending and the center of the helical track recorded on the magnetic tape. The tracking phase is such that the center of the rotating head used sometimes coincides, and the point F corresponds to the center point of the characteristic curve on the trapezoid.

However, in the characteristic data of the reproduction envelope level with respect to the tracking phase when the track width of the helical track and the head width of the rotary head are different, the tracking phase at which the envelope level becomes maximum has a certain range. Therefore, it is difficult for the conventional tracking control device to uniquely determine the optimum tracking phase.

According to the present invention, the time required for a tracking operation is shorter than that of a conventional tracking control device, and the track width of a helical track formed on a magnetic tape is different from the head width of a rotary head used for reproduction. Another object of the present invention is to provide a tracking control device that determines an optimum tracking phase with high accuracy and uniqueness, and controls the phase of the running of the magnetic tape so as to achieve the tracking phase.

[0008]

In order to achieve this object, a tracking control device according to the present invention records a control signal synchronized with a reference signal on a control track formed in the longitudinal direction of a magnetic tape. In a helical scan type magnetic recording / reproducing apparatus which adjusts a relative position between a helical track recorded on the magnetic tape and a rotary head by adjusting a tracking phase which is a phase of a reproduction control signal with respect to a reference signal. Data acquisition means for acquiring characteristic data of an envelope level of a reproduction signal obtained from the rotary head with respect to a predetermined range of tracking phases around the command value, and the characteristic data obtained by the data acquisition means. , Perform a curve regression calculation, and the obtained regression curve And a curve regression calculating means for feeding back the tracking phase as a command value to the data obtaining means, wherein the difference between the command value output by the curve regression calculating means and the previous command value is equal to or less than a predetermined value. And the relative position between the helical track and the rotary cylinder is adjusted so that the command value output by the curve regression calculating means substantially coincides with the tracking phase.

[0009]

In the tracking control device of the present invention, since the curve regression calculation is performed on the characteristic data of the tracking phase and the envelope level of the reproduced signal, the data between the tracking phase steps is also interpolated by a continuous function. Therefore,
It is not necessary to make the tracking phase variable step finer when obtaining the characteristic data.

When acquiring characteristic data of the envelope level with respect to the tracking phase, the envelope level is acquired M times (M is an integer of 2 or more) for each tracking phase within a predetermined range, and the average value thereof is used as the reproduction envelope level. In this case, the influence of the envelope level fluctuation of the reproduction signal due to the contact state between the rotary head and the magnetic tape or the like is reduced.

Further, by selecting a quadratic polynomial as the regression curve, the obtained regression curve has an extreme value (maximum value).
, And is a curve that is line-symmetric with respect to the tracking phase that takes its extreme value. Further, the calculation of the tracking phase having the extreme value can be performed only by the four arithmetic operations of the coefficients of the second-order polynomial, so that the configuration is simplified. In both cases where the track width of the helical track recorded on the magnetic tape and the head width of the rotary head are the same or different, the characteristics of the reproduction envelope level with respect to the tracking phase are linear with respect to the optimum tracking phase. Shows symmetrical characteristics. Therefore, by performing a curve regression calculation using a quadratic polynomial on the characteristic data of the reproduction envelope level with respect to the tracking phase, the optimum tracking phase that is the center line of the characteristic data and the obtained regression curve have extreme values (maximum values). Tracking phase).

As described above, according to the present invention, the time required for the tracking operation is shorter than that of the conventional tracking control device, and it is hardly affected by the fluctuation of the envelope of the reproduction signal. Even when the track width of the helical track is different from the head width of the rotary head used for reproduction, the optimum tracking phase can be uniquely determined with high accuracy.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of a tracking control device according to the present invention will be described below with reference to the drawings. FIG. 1 is a block diagram of a tracking control device according to an embodiment of the present invention.

The magnetic tape 101 runs and is driven by a pinch roller 102 and a capstan shaft 103 directly connected to a capstan motor 104. Further, the magnetic tape 101 is wound around the rotating cylinder 106 at an appropriate angle. The rotary cylinder 106 has a rotary head 107,
108, and the magnetic tape 1
A helical track recorded and formed on the data track 01 is scanned to obtain a reproduced signal. The rotary heads 107 and 108 have different azimuth angles and have substantially the same head width. The head width of the rotary heads 107 and 108 is approximately 1.5 times the track width of the helical track. The control head 105 reproduces a control signal recorded in the longitudinal direction of the magnetic tape 101 to obtain a reproduction control signal CTL. The reference signal generator 109 generates a reference signal REF serving as a reference when detecting the phase of the reproduction control signal CTL. The phase comparator 112 includes:
The reference signal REF and the reproduction control signal CTL are input, and the reproduction control signal CT for the reference signal REF is input.
The tracking phase X, which is the phase of L, is detected. The phase error detector 113 includes a tracking phase X and a tracking phase command signal PR which is a target value of the tracking phase X.
EF is input and outputs the phase error of those signals.
The phase control circuit 111 supplies power proportional to the output signal of the phase error detector 113 to the capstan motor 104. Therefore, the running of the magnetic tape 101 is controlled so that the tracking phase X becomes the phase given by the tracking phase command signal PREF.

Now, the operation performed by the tracking control device of the present embodiment will be described. First, switch 11
7 is connected to the contact a, and the tracking phase command signal PR
The output signal of the tracking phase variable signal generator 118 is selected as EF. The variable tracking phase signal generator 118 generates a ramp-shaped signal. As a result, the tracking phase, which is the phase of the reproduction control signal CTL with respect to the reference signal REF, changes like a ramp as in the output signal of the tracking phase variable signal generator 118.
On the other hand, the reproduction signal from the rotary head 107 is input to the envelope level detector 110. The envelope level detector 110 samples the envelope level of the input reproduction signal five times, sets the average value as the reproduction envelope level Y, and outputs it to the data acquisition means 120.

The data acquisition means 120 is provided in the semiconductor memory 1
14 and a data extractor 119. At the timing when the reproduction control signal CTL is input, the tracking phase X changing in a ramp shape and the reproduction envelope level Y corresponding to the tracking phase X are sequentially stored in the semiconductor memory 114 as a pair of data. FIG. 3 is a graph in which the data of the envelope level Y with respect to the tracking phase X stored in the semiconductor memory 114 is plotted on a graph.

Next, the data extractor 119 outputs the tracking phase Xp input from the output switch 116.
, 128 data pairs before and after the data pair, ie, a total of 256 data pairs,
4 is output to the curve regression calculator 115. However, in the initial stage, the output changeover switch 116 is connected to the contact d, and outputs the tracking phase “0” held by the device as an initial value.

In the curve regression calculator 115, 256 data pairs (Xi, Y) input from the data extractor 119 are input.
Curve regression calculation is performed using i) (i is a natural number of 256 or less). In this embodiment, a second-order polynomial is used as the regression curve. That is, the tracking phase X and the reproduction envelope level Y are approximately the following (Equation 1)
And the data actually measured (Xi, Y
The coefficients a, b, and c of the second-order polynomial are determined so as to best match the characteristic of i).

[0019]

(Equation 1)

Here, a polynomial for X on the right side of (Equation 1) is defined as a function f (X), and

[0021]

(Equation 2)

For convenience, they are defined as follows. Further, the function G is defined as follows.

[0023]

(Equation 3)

The function G defined here is for obtaining the sum of squares of the error between the actually measured reproduction envelope level Yi and the corresponding approximate value f (Xi). Therefore, when this function G is minimized, the measurement data (Xi,
Yi) and the approximated curve represented by (Equation 1) best match. The function G is minimized when the function G is 2
The value obtained by partially differentiating each of the polynomial coefficients a, b, and c is "
0 ".

From this, as shown below, a ternary simultaneous equation relating to the coefficients a, b, and c of the second-order polynomial is obtained.

[0026]

(Equation 4)

[0027]

(Equation 5)

[0028]

(Equation 6)

The solution of this simultaneous equation can be expressed in the form of a determinant as shown in (Formula 7).

[0030]

(Equation 7)

Here, "-1" represents an inverse matrix of the matrix. Since the regression curve thus obtained is a second-order polynomial, there is only one extreme value. The tracking phase Xp that gives the extreme value is expressed by the following (Equation 8) using the coefficients a and b of the second-order polynomial.

[0032]

(Equation 8)

FIG. 4 shows the measured data shown in FIG.
9 is a graph of a regression curve obtained by performing a curve regression calculation using a quadratic polynomial. At this time, the obtained values of the coefficients a, b, and c of the second-order polynomial and the tracking phase Xp that gives the extreme value of the second-order polynomial are:

[0034]

(Equation 9)

[0035]

(Equation 10)

[0036]

[Equation 11]

[0037]

(Equation 12)

Is as follows. As a result of such calculation, the curve regression calculator 115 outputs the tracking phase Xp to the output switch 116, the delay unit 121, and the subtractor 122.

The delay unit 121 receives the input tracking
Holds the phase Xp and reduces the previously input tracking phase
Output to the arithmetic unit 122. Therefore, the subtractor 122 is
Tracking phase Xp input from regression calculator 115
Switch the difference between the tracking phase and the previously input tracking phase
Output to the switch 116. Output switch 1
16 indicates that the absolute value of the value input from the subtractor 122 is predetermined.
(In this embodiment, 1 × 10^-1And above)
Tracking input from the curve regression calculator 115
The phase Xp is fed back to the data extractor 119. Therefore,
The signal is input from the arithmetic unit 122 to the output switch 116.
The absolute value of the value is 1.0265 and 1 × 10 ^-1Is it more than
Output switch is connected to contact d
The tracking phase Xp input from the recursive calculator 115 is
The data is returned to the data extractor 119.

The data extractor 119 performs a one-way operation around the data pair corresponding to the input tracking phase Xp again.
28 data pairs, that is, a total of 256 data pairs are requested from the semiconductor memory 114 and output to the curve regression calculator 115. The curve regression calculator 115 performs the above-described curve regression calculation using the obtained 256 data pairs. The resulting coefficients a, b, and c of the quadratic polynomial and the tracking phase Xp that gives the extreme value of the regression curve are:

[0041]

(Equation 13)

[0042]

[Equation 14]

[0043]

(Equation 15)

[0044]

(Equation 16)

As described above, the curve regression calculator 115 outputs the tracking phase Xp to the output switch 116, the delay unit 121, and the subtractor 122. Therefore, the absolute value of the value input from the subtractor 122 to the output switch 116 is 8.228 × 10 ⁻² , and 1 ×
Since it is 10 ^-1 or less, the output changeover switch 116 is connected to the contact c.

When a series of operations as described above is completed, the switch 117 is connected to the contact b and selects the tracking phase Xp finally calculated by the curve regression calculator 115 as the tracking phase command signal PREF. Accordingly, the phase (tracking phase X) of the reproduction control signal CTL with respect to the reference signal REF is changed by the curve regression calculator 1
15 is controlled so as to coincide with the finally calculated tracking phase Xp.

Here, FIG. 5 is a graph of a regression curve obtained by the second curve regression calculation for the measurement data shown in FIG. The optimum point of the true tracking phase is a tracking phase at which the center of the helical track coincides with the center of the rotary head 107 as shown in FIG. 2, and its value is “1”. Therefore, it can be seen that the optimum tracking phase is obtained with high accuracy.

Therefore, even when the track width of the helical track and the head width of the rotary heads 107 and 108 are different, the optimum tracking phase can be uniquely determined.

In this embodiment, however, the ratio of the head width of the rotary heads 107 and 108 to the track width of the helical track is 1.5 times, the number of envelope level samplings for detecting the reproduction envelope is 5 times, and the curve is curved. The reason why the regression calculator 115 requests the semiconductor memory 114 to have 256 data items and the value used as a criterion for switching the output changeover switch 116 to be 1 × 10 ⁻¹ will be easily understood in describing the present embodiment. For
The present invention is not limited to this case, and various modifications are possible.

In the present embodiment, the characteristic data of the reproduction envelope level for a wide range of tracking phases is stored in advance in the semiconductor memory 114, and the characteristic data of a necessary range is extracted from the characteristic data and a plurality of curve regression calculations are performed. The case where the calculation is performed has been described. However, a similar effect can be obtained by newly acquiring characteristic data in a necessary range every time the curve regression calculation is performed and performing the curve regression calculation on the obtained data.

[0051]

As is clear from the above description, according to the tracking control device of the present invention, the time required for the tracking operation is shorter than that of the conventional device, and the track width of the helical track and the time required for reproduction are reduced. Even if the head width of the rotating head differs, a tracking control device capable of uniquely determining an optimum tracking phase with high accuracy can be provided.

Also, in the case of insert editing or assemble editing which is often performed in a broadcast VTR or the like, the tracking control device of the present invention operates effectively, eliminating the need for an operator to perform tracking adjustment, and reducing the recording pitch of a helical track. Can be automatically equalized.

[Brief description of the drawings]

FIG. 1 is a block diagram of a tracking control device according to an embodiment of the present invention.

FIG. 2A is a diagram showing characteristics of a reproduction envelope level with respect to a tracking phase when a head width of a rotary head used for reproduction is wider than a track width of a helical track formed on a magnetic tape; Is a diagram showing the relative positions of the helical track and the rotating head in each tracking phase

FIG. 3 is a graph in which a data pair of a reproduction envelope level Y with respect to a tracking phase X stored in a semiconductor memory 114 is plotted on a graph.

4 is a diagram showing a regression curve obtained by performing a curve regression calculation on the measurement data shown in FIG. 3;

FIG. 5 is a diagram showing a regression curve obtained by a second curve regression calculation for the measurement data shown in FIG. 3;

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 101 Magnetic tape 102 Pinch roller 103 Capstan shaft 104 Capstan motor 105 Control head 106 Rotating cylinder 107,108 Rotating head 109 Reference signal generator 110 Envelope level detector 111 Phase controller 112 Phase comparator 113 Phase error detector 114 Semiconductor Memory 115 Curve regression calculator 116 Output changeover switch 117 Switch 118 Tracking variable phase signal generator 119 Data extractor 120 Data acquisition means 121 Delay unit 122 Subtractor

Claims (6)

(57) [Claims] 1. A control signal synchronized with a reference signal is recorded on a control track formed in a longitudinal direction of a magnetic tape, and a tracking phase, which is a phase of a reproduction control signal with respect to the reference signal, is adjusted at the time of reproduction. In a helical scan type magnetic recording / reproducing apparatus for adjusting a relative position between a helical track recorded on a magnetic tape and a rotary head, a helical scan type magnetic recording / reproducing apparatus obtains a tracking phase within a predetermined range around an input command value from the rotary head. Data acquisition means for acquiring characteristic data of the envelope level of the reproduced signal to be obtained, and performing a curve regression operation on the characteristic data obtained by the data acquisition means, and obtaining a tracking phase at which the obtained regression curve becomes an extreme value. Curve regression operation returning to the data acquisition means as a command value Calculation means, and when the difference between the command value output by the curve regression calculation means and the previously output command value is equal to or less than a predetermined value, the feedback to the data acquisition means is stopped, and the helical track and the rotation A tracking control device, wherein a tracking value and a command value output by the curve regression calculating means are adjusted to substantially match a tracking position by adjusting a relative position with respect to a cylinder. 2. The tracking control device according to claim 1, wherein the curve regression calculation means performs a curve regression calculation using a quadratic polynomial as a regression curve. 3. A data acquisition means for acquiring characteristic data of an envelope level with respect to a predetermined range of a tracking phase around a command value inputted by the curve regression calculation means, and determining a relative position between the helical track and the rotary head. 2. The tracking control device according to claim 1, wherein the tracking control device is configured to acquire and collect again by adjusting. 4. A data acquisition means having a memory means for storing characteristic data of an envelope level with respect to a tracking phase in a second predetermined range which is set in advance, and a command value inputted by said curve regression calculation means. 2. The tracking control device according to claim 1, wherein characteristic data corresponding to a tracking phase in a predetermined range around the center is extracted from the memory means. 5. A data acquisition means for acquiring characteristic data of an envelope level with respect to a predetermined range of tracking phases centered on the command value inputted by the curve regression calculation means, for each tracking phase within the predetermined range. , The envelope level is acquired M times (M is an integer of 2 or more),
2. The tracking control device according to claim 1, wherein the average value is used to acquire characteristic data that is used as an envelope level. 6. A data acquisition means for acquiring envelope level characteristic data for a tracking phase in a second predetermined range set in advance by K times the envelope level for each tracking phase in the second predetermined range. (K is an integer of 2 or more) having a memory means for storing characteristic data obtained as an envelope level with an average value thereof, and a tracking phase in a predetermined range around a command value inputted by the curve regression calculating means. 2. The tracking control device according to claim 1, wherein characteristic data corresponding to the following is extracted from said memory means.