JP3077456B2 - 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 a characteristic curve of an envelope level of a reproduction signal with respect to the tracking phase. Things.

[0002]

2. Description of the Related Art Generally, a video tape recorder (hereinafter referred to as a VTR) used for recording a video signal is different from a VTR used for reproducing a video signal, or even if the VTR used for recording and reproduction is the same. When the magnetic tape expands due to an environmental change, 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 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 variable step of the tracking phase is made fine in order to improve the tracking accuracy, and the reproduction caused by the contact state between the rotary head and the magnetic tape is performed. In order to reduce the influence of signal envelope fluctuation, envelope level detection is performed a plurality of times for each step of the tracking phase, and the average value is used as the envelope level for each tracking phase step. As a result, there is a problem that the time required for the tracking operation becomes long.

FIG. 2A is a diagram showing a characteristic curve 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. is there. 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 a similar azimuth angle to 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. Further, the helical truck 204 originally has the rotating head 201.
Is not the track to be scanned, but the rotating head 20
Since the track is recorded at the same azimuth angle as 1, when the track is on-track, the reproduction envelope level 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 bending factor of the helical track and the center of the helical track formed on the magnetic tape during reproduction. The tracking phase is such that the centers of the rotating heads used coincide with each other, and the point F corresponds to the center point of the characteristic curve on the trapezoid in FIG.

However, in the characteristic curve 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 is maximum has a predetermined 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 that the tracking phase becomes 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 that 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, A control signal synchronized with a reference signal is recorded on a control track formed in the longitudinal direction of the recording medium. At the time of reproduction, a tracking phase which is a phase of a reproduction control signal with respect to the reference signal is adjusted to be recorded and formed on the magnetic tape. Helical trucks and rotating In a helical scan type magnetic recording / reproducing apparatus for adjusting a relative position with respect to a track, data acquisition means for acquiring characteristic data of an envelope level of a reproduction signal obtained from the rotary head with respect to a tracking phase of a tracking phase range input and commanded, Curve regression calculation means for calculating a tracking phase at which a regression curve of a quadratic polynomial obtained by performing a curve regression calculation on the characteristic data obtained by the data acquisition means, and the curve regression calculation means The regression curve to be calculated is provided with a repetition number control unit that feeds back a plurality of times to the data acquisition unit by inputting a predetermined tracking phase range around the tracking phase that is an extreme value ,
Duplication to the data acquisition means by the repetition number control means
The tracking phase is adjusted by several feedbacks so that the tracking phase substantially matches the tracking phase finally calculated by the curve regression calculating means.

[0009]

According to the tracking control device of the present invention, since a curve regression operation is performed on the characteristic curve of the tracking phase and the envelope level of the reproduced signal, even if the envelope of the reproduced signal is changed, the averaging process is equivalently performed. Will be. Therefore, it is not necessary to perform envelope level detection a plurality of times for each tracking phase step.

Furthermore, since a curve regression operation is performed on the characteristic curve of the tracking phase and the envelope level of the reproduction 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 curve.

Further, by selecting a quadratic polynomial as the regression curve, the obtained regression curve has only one extreme value (maximum value), and is linearly symmetric with respect to the tracking phase having the extreme value. Curve. Further, the calculation of the tracking phase that takes the extreme value can be performed only by the four-law operation of the coefficients of the second-order polynomial, and 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 using a quadratic polynomial on the characteristic curve of the reproduction envelope level with respect to the tracking phase, the optimum tracking phase that is the center line of the characteristic curve and the obtained regression curve have extreme values (maximum values). ) Coincide with each other.

As described above, the operation time is shorter than that of the conventional tracking control device, and the helical track formed on the magnetic tape has a different track width from the rotary head used for reproduction. The optimum tracking phase can be uniquely determined with high accuracy.

According to the present invention, the time required for the tracking operation is shorter than that of the conventional tracking control device, and the track width of the helical track recorded on the magnetic tape is different from the head width of the rotary head used for reproduction. In this case, the optimal tracking phase can be determined with high accuracy and
It can be uniquely determined.

[0014]

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. Magnetic tape 101
Is driven and driven by a pinch roller 102 and a capstan shaft 103 directly connected to a capstan motor 104. Further, the magnetic tape 101 has a rotating cylinder 106.
It is wound at an appropriate angle. Rotary cylinder 10
Rotation heads 107 and 108 are attached to 6, and at the time of reproduction, a helical track recorded on the magnetic tape 101 is scanned to obtain a reproduction signal. The rotating heads 107 and 108 have different azimuth angles, respectively.
They have the same or 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, and reproduces a control signal CT.
Get L. The reference signal generator 109 outputs a reference signal R serving as a reference when detecting the phase of the reproduction control signal CTL.
Generate EF. The phase comparator 112 includes a reference signal RE.
F and the reproduction control signal CTL are input, and a tracking phase X which is a phase of the reproduction control signal CTL with respect to the reference signal REF is detected. Phase error detector 11
3, a tracking phase X and a tracking phase command signal PREF, which is a target value of the tracking phase X, are inputted, and a phase error of those signals is output. 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 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 P
As REF, a variable tracking phase signal generator 118
Select the output signal of 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 detects an envelope level of the input reproduction signal.

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 sampled and sequentially stored in the semiconductor memory 114 as a pair of data. FIG. 3 shows 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 includes 128 data pairs before and after the data pair corresponding to the tracking phase Xp input from the repetition number controller 116,
That is, a total of 256 data pairs are requested from the semiconductor memory 114 and output to the curve regression calculator 115. However, the repetition number controller 116 outputs the tracking phase “0” held by the device as an initial value.

In the curve regression calculator 115, the 256 data pairs (Xi, Y
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, assuming that the tracking phase X and the reproduction envelope signal Y approximately follow the following (Equation 1), the actually measured data (Xi, Y
The coefficients a, b, and c of the second-order polynomial are determined so as to best match the characteristic of i).

[0020]

(Equation 1)

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

[0022]

(Equation 2)

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

[0024]

(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 indicates a transposed 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.
It is represented by

[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 repetition number controller 116.

The repetition number controller 116 manages the number of times the tracking phase Xp calculated by the curve regression calculator 115 is input, that is, the number of calculations performed by the curve regression calculator 115. If there is, the input tracking phase Xp is output to the data extractor 119. Therefore, when the number of times is the second time, the data extractor 119 extracts 128 data pairs before and after the data pair corresponding to the re-input tracking phase Xp, that is, 256 data pairs in total, It requests the memory 114 and outputs it 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:

[0040]

(Equation 13)

[0041]

[Equation 14]

[0042]

(Equation 15)

[0043]

(Equation 16)

Is as follows. 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 where the center of the helical track coincides with the center of the rotary head 107 as shown in FIG. 2, and in this case, the value is about “7”.
Therefore, it can be seen that the optimum tracking phase is obtained with high accuracy.

When the number of times that the tracking phase Xp is input has reached a predetermined number (in this embodiment, two times), the repetition number controller 116 switches the finally input tracking phase Xp to the switch 117. Output to

When a series of operations as described above is completed, the switch 117 is connected to the terminal b, and selects the tracking phase Xp output from the repetition number controller 116 as the tracking phase command signal PREF. As a result, the phase (tracking phase X) of the reproduction control signal CTL with respect to the reference signal REF is controlled to match the tracking phase Xp output from the repetition number controller 116. 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 data required by the curve regression calculator 115 from the semiconductor memory 114 is 256, The reason why the number of repetitions serving as a criterion of the repetition number controller 116 is set to 2 is to make it easy to understand in describing the present embodiment, and the present invention is not limited to this case.
Various modifications are possible.

In the present embodiment, envelope level characteristic data for a wide range of tracking phases is stored in advance in the semiconductor memory 114, and a necessary range of characteristic data is extracted therefrom to perform a plurality of curve regression calculations. Although the case has been described, 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.

[0049]

As is apparent from the above description, the tracking control device of the present invention acquires the characteristic data of the envelope level of the reproduction signal obtained from the rotary head with respect to the tracking phase in the tracking phase range specified by the input. Data acquisition means, curve regression calculation means for calculating a tracking phase at which a regression curve of a quadratic polynomial obtained by performing a curve regression operation on the characteristic data obtained by the data acquisition means , A predetermined tracking phase range about the center of the tracking phase at which the regression curve calculated by the curve regression calculation means becomes an extreme value
Means for controlling the number of repetitions to be fed back to the data acquisition means a plurality of times as input.
Multiple times to the data acquisition means by the return number control means
By adjusting the tracking phase so that the tracking phase finally matches the tracking phase calculated by the curve regression calculating means, the time required for the tracking operation is shorter than that of the conventional device, and Even when the track width and the head width of the rotary head used for reproduction are different, the optimum tracking phase can be uniquely determined with high accuracy.

The tracking control device of the present invention can be effectively applied to insert editing and assemble editing which are often performed in a broadcast VTR and the like, eliminating the need for an operator to perform tracking adjustment and recording a helical track. This is to automatically equalize the pitch.

[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 a characteristic curve 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; Is a diagram showing the relative positions of the helical track and the rotating head in each tracking phase

FIG. 3 is a graph plotting a data pair of an envelope level Y with respect to a tracking phase X stored in a semiconductor memory 114;

4 is a graph of a regression curve obtained by performing a curve regression calculation on the measurement data shown in FIG.

5 is a graph of a regression curve obtained by a second curve regression calculation for the measurement data shown in FIG.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 101 Magnetic tape 102 Pinch roller 103 Capstan axis 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 Repetition number controller 117 Switch 118 Tracking variable phase signal generator 119 Data extractor 120 Data acquisition means

Claims (3)

(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. At the time of reproduction, a tracking phase which is a phase of a reproduction control signal with respect to the reference signal is adjusted. In a helical scan type magnetic recording / reproducing apparatus which adjusts a relative position between a helical track recorded on a magnetic tape and a rotary head, an envelope of a reproduction signal obtained from the rotary head with respect to a tracking phase in a tracking phase range inputted and instructed. Data acquisition means for acquiring level characteristic data, and a tracking phase at which a regression curve of a quadratic polynomial obtained by performing a curve regression operation on the characteristic data obtained by the data acquisition means is calculated. Curve regression calculation means ,
A repetition number control means for inputting a predetermined tracking phase range around a tracking phase at which the regression curve calculated by the curve regression calculation means becomes an extreme value and feeding back the data acquisition means a plurality of times; ,
To the data acquisition means by the repetition number control means
A plurality of feedbacks to adjust the tracking phase so as to substantially match the tracking phase finally calculated by the curve regression calculation means. 2. The data acquisition means according to claim 1, wherein the characteristic data of the envelope level with respect to the tracking phase within a predetermined tracking phase range instructed by the curve regression calculation means is provided.
2. The tracking control device according to claim 1, wherein the tracking control device is configured to acquire and collect data again by changing a tracking phase. 3. The data acquisition means has 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. 2. The tracking control device according to claim 1, wherein characteristic data corresponding to a range is extracted from said memory means.