JPH06150465A - Information reproducing device - Google Patents

Abstract

PURPOSE:To provide an information reproducing device improving the influence to a regenerative signal due to a track bend by using a tracking error signal obtained from an entire track area substantially. CONSTITUTION:A tape 8 forming a track containing a tracking pilot is scanned by a head 1, and the regenerative signal is outputted. The tracking error signal is generated from the regenerative signal by a tracking error detection circuit 2. A tracking control signal is formed from the tracking error signal in the track according to the pattern of the track bend by a control signal former 3. A positional relation between the head and the track is controlled according to a signal impressed from the control signal former 3 by a tracking control means 4. Thus, the decrease in the amplitude of the regenerative signal occurring due to the track bend is suppressed by optimizing the tracking position, and the dignity of the regenerative signal is enhanced.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an information reproducing apparatus for reproducing information such as images, sounds and data recorded on tracks on a tape.

[0002]

2. Description of the Related Art An information reproducing apparatus using a magnetic tape as a medium such as a VTR has been put into practical use and is in widespread use. In such a device, it is important to perform accurate tracking of the head and the track in order to stably reproduce information from the track and to ensure compatibility. For this purpose, an information reproducing apparatus has been put into practical use, which employs a tracking control method called an ATF method in which a pilot signal is frequency-multiplex-recorded on a track together with an information signal during recording and tracking is performed by using the pilot signal during reproduction. There is. A typical example is an 8 mm VTR. In such a system, the head scanning position (mostly the tape feeding speed by the capstan) is controlled so that the tracking error signal detected becomes zero. However, the high frequency error signal remains according to the control band.

[0003]

However, in the conventional information reproducing apparatus as described above, when there is a track bend with respect to the head scanning, the tracking control may be performed in an optimum state from the viewpoint of the reproduction signal level. There was

The slanted track formed on the tape medium and the head scanning have some deviations due to mechanical variations of the information reproducing apparatus. For example, in general, a helical scan is performed by a rotary head for reproduction, but various factors such as shaft runout of a cylinder with a head attached, tape running fluctuation, and tape deformation cause a track on the tape medium and a head scanning locus during reproduction. Deteriorates the linearity of.
On the other hand, in the tracking control, the control band changes depending on the setting of the control loop gain, but at least the DC component of the tracking error signal is controlled to be zero. Further, in the configuration of capstan feeding, the head cannot generally follow the bend in the track. Therefore, for example, when there is a track bend as schematically shown in FIG. 6, the scanning locus of the head 13 when the control system reaches the steady state becomes as shown by the broken line in FIG. 1
It can be seen that the track 14 protrudes from the scanning locus of No. 3, that is, the reproduction signal level decreases at the end of the track 14. However, in reality, as shown by the broken line in FIG. 6B, there is a head locus in which reproduction can be performed in the entire region without lowering the reproduction signal level.

SUMMARY OF THE INVENTION In view of the above problems, it is an object of the present invention to provide an information reproducing apparatus capable of suppressing a decrease in reproduction signal amplitude even when there is a track bend.

[0006]

In order to solve the above problems, the information reproducing apparatus of the present invention scans a tape having an information track containing a tracking pilot signal, and outputs the reproduction signal by scanning the track. A head, a tracking error detecting means for detecting a tracking error of a head scanning with respect to a track by a tracking pilot signal in a reproduction signal, and a tracking for controlling a scanning position by the head according to a track bending pattern indicated by the tracking error signal. The control signal generating means for generating an error signal and the tracking control means for controlling the track scanning position of the head in response to the output of the control signal generating means are provided.

[0007]

According to the present invention, since the head scanning position is corrected by the tracking control means in accordance with the track bending by the above-mentioned structure, it is possible to suppress the reduction of the reproduction signal.

[0008]

DESCRIPTION OF THE PREFERRED EMBODIMENTS A magnetic recording / reproducing apparatus according to an embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 is a block diagram showing the structure of an information reproducing apparatus according to an embodiment of the present invention. In FIG. 1, 1
Is a head, 2 is a tracking error signal detection circuit, 3 is a control signal generator, 4 is tracking control means, 5 is a cylinder, 6 is a cylinder control circuit, 7 is a rotation detector, 8 is a tape, and 12 is a head amplifier. . The tracking control means 4 includes a capstan 9, a capstan control circuit 10,
It is composed of a rotation detector 11.

The cylinder control circuit 6 controls the rotation of the cylinder 5 to be constant based on the cylinder rotation speed and phase detection from the rotation detector 7. The head 1 is mounted on the cylinder 5, and the tape 8 wound around the head 5 is scanned as the cylinder 5 rotates. Head 1
The reproduced signal from is amplified by the head amplifier 12 to an amplitude sufficient for the subsequent processing. If it is necessary to switch and reproduce a plurality of heads depending on the configuration of the cylinder (for example, two heads facing each other by 180 degrees), the switching operation is performed at this stage. The cylinder control circuit 6 creates a head switch signal necessary for this processing based on the rotational position signal from the rotation detector and supplies it to the head amplifier 12. Since the process of demodulating and processing the reproduced signal to the final usable form after the head amplifier output depends on the specific device method and type, detailed description is omitted here, but generally waveform equivalent , Data playback (binarization),
Processing such as error correction and demodulation will be performed after clock extraction, synchronization pattern detection, and the like.

The reproduced signal is also input to the tracking error detection circuit 2, where the tracking pilot signal component included in the reproduced signal is extracted and a tracking error signal corresponding to its amplitude is output. A pilot signal for tracking is recorded on the track formed on the tape 8 in addition to the digital information signal, and the crosstalk amount of the pilot signal from the adjacent track leaking into the head 1 is related to the head-track positional relationship. A tracking error is created by utilizing the fact that it changes according to. The specific configuration depends on the recording method of the pilot signal, but the minimum requirement is that tracking errors can be detected over the entire track to the extent that the track bending pattern can be discriminated (at least three locations if the pilot is burst-like). The pilot does not necessarily have to be recorded continuously over the entire track, and the reproduction system does not necessarily have to continuously perform error detection, but in this example, it is a continuous system.

The detected tracking error signal is given to the capstan control circuit 10 via the control signal generator 3. The configuration and operation of the control signal generator 3 will be described later. The capstan control circuit 10 controls the speed of the capstan 9 in accordance with the speed signal from the rotation detector 11 and also controls the phase so that the given tracking error signal becomes zero. Thus, the tape running is controlled so that the head traces the track.

The operation of the control signal generator 3 will be described first with reference to FIG. FIG. 2 is a signal waveform diagram for explaining the operation of the control signal generator. In the figure, a and b represent signal waveforms at points A and B in FIG. 1, respectively. Reference numeral b represents a tracking error signal, and a signal for one track is output every time the head switch signal a is inverted. From this waveform, it can be seen that a large track bend occurs near the end of the track. The broken line b1 drawn on b is the average value of the tracking error signal in the track, and the alternate long and short dash line b2
Indicates the average of the maximum and minimum values. In the normal control, the control is performed so that the DC component of the tracking error signal becomes zero, so that the control is performed with b1 as the center in FIG. However, as a result, as shown in this example, the error appears largely on the upper side, and the reproduction signal is lowered at that portion.

When reproducing analog-recorded information such as VHS and 8 mm VTR, the reproduction S / N becomes a problem, so it is necessary to control the head so as to be the track center in as many areas as possible. However, in the case of digital recording, the tracking position itself does not affect the final reproduction signal quality as long as the data can be normally reproduced or the error correction capability is satisfied. Therefore, even if the tracking error within the range is allowed, it is important to reduce the area exceeding the range. That is, it is necessary to minimize the maximum reduction amount of the reproduction signal amplitude. In order to minimize the reduction of the reproduction signal, the amplitude of the remaining tracking error should be equally distributed vertically. Therefore, since the control target is not the average value but the average of the maximum and minimum values of the tracking error signal, b2 in FIG. 2, this value may be given to the tracking control system as a new error signal. Here, an example in which this processing is realized by software on the signal processor is shown below.

FIG. 3 is a flow chart showing an example of the signal processing algorithm of the control signal generator 3. Process 101
Is waiting for the timing for performing this detection processing at appropriate intervals. As described above, the processing interval is selected so that the input processing is performed at least three times (more if possible) within the scanning time of one track. Actually, a predetermined time elapses by referring to a hardware or software timer provided in the processor. It should be noted that such a waiting loop is not necessary when the entire flow is processed by the timer interrupt. In process 102, it is determined whether or not one track scan is completed. Specifically, the polarity of the head switch signal is checked, and if it is inverted with respect to the previous polarity, one scan is completed. If it is not flipped, it will go down as it is. The polarity of the head switch read each time needs to be stored for the next determination. Process 103 is an input process of the tracking error signal. If the tracking error signal is an analog signal, AD conversion is performed, and if it is digital, the value is directly read into the internal memory (denoted as X). Process 104 is a maximum / minimum value detection process. Maximum and minimum past values stored in memory (respectively Xmax and Xm
In) and the current tracking error signal value X are compared in magnitude, and Xmax and Xmin are updated according to the comparison result. As described above, one process during the scanning period is completed, and the process returns to the next process timing wait.

If it is determined that the track scanning has ended, a control signal is calculated and output in step 105. The calculation formula is as shown in the figure. Further, after the control signal is output, preparation for detecting the next track, that is, Xmax, X
The process of presetting min is also performed here.

As described above, according to the present embodiment, the maximum / minimum value of the tracking error signal is obtained for each scan, and the control signal for minimizing the maximum value of the tracking error is set at the output. Therefore, the tracking control system operates with this new position as a target, and the maximum value of the reduction of the reproduction signal is minimized.

Next, another embodiment of the present invention will be described with reference to FIG. FIG. 4 is a second embodiment of the flowchart of the control signal generator realized by software similarly to FIG. 3, and has the same configuration as that shown in FIG. 1 except for the control signal generator. According to the algorithm of FIG. 3, if the amount of track bending is equal to or less than the difference between the head width and the track width, the optimum tracking position control is performed. In some cases, another evaluation index may be needed for the tracking position.
For example, in the example of FIG. 2b, when the amplitude decrease occurs not only in the track end but also in the first half, conversely, even if the short-term amplitude decrease near the end is allowed, the first half long-term amplitude decrease should be suppressed. However, the influence on the signal reproduction is considered to be small. In FIG. 4, improvement is attempted by correcting the control signal so that the positive and negative periods of the tracking error signal are substantially the same. In FIG. 4, processes 101 to 104 are the same as those in FIG. Reference numeral 106 is a process for measuring the time length of the tracking error signal for each polarity. That is, the memory (SUMT) is incremented or decremented according to the polarity of the tracking error signal X. By this processing, the SUMT can obtain the number of sample points corresponding to the difference between the positive period and the negative period of the tracking error at that time.
Since the time length is measured by sampling, it is necessary to secure a sufficient number of sample points in order to ensure accuracy.

At this time, this processing may be performed only when the absolute value of the tracking error signal is a predetermined value or more. If a value corresponding to, for example, (head width-track width) / 2 is selected as the predetermined value here, only the portion where the reproduction signal amplitude actually decreases will be evaluated. In addition, as a predetermined value, an amplitude (for example, PLL) that affects the quality of the reproduced signal after demodulation appears.
, The error rate exceeds the correction limit, etc.), it is possible to evaluate only the portion that affects the quality of the reproduced signal.

In step 108, the S thus obtained is obtained.
Using the UMT, the control signal value calculated in the process 107 is corrected and output. Specifically, for example, the control signal is increased or decreased at a constant rate depending on the polarity of SUMT, or
The MT is multiplied by a predetermined value to be added to the control signal value, and the correction is performed so that the tracking position is shifted to the side where the reproduction signal is largely decreased. Also, SUMT is cleared in preparation for the next detection. It should be noted that this processing is performed when the amount of track bending is large and the reduction of the reproduction signal amplitude cannot be avoided, that is, when Xmax-Xmin is (head width-
It may be executed only when the width is equal to or more than the track width.

As described above, according to the present embodiment, the control signal is modified so that the reduction period of the reproduction signal becomes equal to the positive and negative in addition to the previous embodiment, so that the track bend is large and the amplitude of the reproduction signal is reduced. If it is unavoidable, the tracking position can be corrected so as to reduce the influence.

Next, another embodiment of the present invention will be described with reference to FIG. FIG. 5 is a flow chart of the control signal generator 3 realized by software similarly to FIG. 3, and the configuration is the same as that shown in FIG. 1 except for the control signal generator. In the second embodiment of the flow chart, an example is shown in which the absolute value of the tracking error signal is not less than the predetermined value and the control signal is modified according to this period. This is an example of proceeding to determine the control signal itself according to the portion where the absolute value of the tracking error signal is equal to or greater than a predetermined value. In FIG. 5, 101 to 103 have the same contents as in FIG. The process 109 is a averaging process with a condition, and the tracking error X read in 103 is added to the internal memory (SUMX) only when the absolute value is equal to or larger than a predetermined value. As in the second embodiment, the predetermined value may be (head width-track width) / 2, or a value that affects the reproduced signal quality after demodulation. In process 110, SUMX integrated over one scan is multiplied by a constant as necessary and output. Also, SUMX is cleared in preparation for the next detection.

As described above, according to this embodiment, the tracking control is performed at a position where the amount that substantially affects the reproduction signal quality is the smallest.

The embodiment is an example of the present invention, and various modifications can be made to the realizing means and the specific configuration without departing from the spirit of the present invention.

For example, although the control signal generator is implemented by software, the hardware may be equivalent.

The algorithm shown in FIGS. 3 and 4 is basically an iterative process by an infinite loop, but the minimum required is to take a plurality of samples in one track, which is the object of reproduction. It is not necessary to do the same for all tracks. The processing may be performed intermittently one track at a time, or the correction processing of FIG. 4 may be calculated only at the start of reproduction or the like.

Further, with respect to the detection of the maximum value and the minimum value in FIGS. 3 and 4, the past detection value is held and the average or low-pass processing is performed in consideration of the repeatability of track bending. It is very preferable from the viewpoint of stabilization of. At this time, when the bending pattern changes depending on the head mounting position on the cylinder, it is preferable to detect and store the maximum and minimum values for each head.

[0028]

As described above, the information reproducing apparatus of the present invention has a head for scanning a track on which an information track containing a tracking pilot signal is formed and outputting the reproduced signal, and a head for reproducing the reproduced signal. Tracking error detection means for detecting a tracking error of a head scan with respect to a track by the tracking pilot signal, and control for creating a tracking error signal for controlling a scanning position by the head according to a track bending pattern indicated by the tracking error signal. Since the signal generating means and the tracking control means for controlling the track scanning position of the head in response to the output of the control signal generating means are provided, the tracking is performed so as to suppress the decrease of the reproduction signal amplitude due to the track bending. Correct the position to improve the quality of the playback signal. Can.

Further, the control signal generating means is configured to output the average of the maximum value and the minimum value of the tracking error signal within the predetermined track length, so that the control is performed in comparison with the control at the substantially average value. It is possible to suppress the decrease of the signal amplitude to the minimum and improve the quality of the reproduced signal.

Further, the control signal generating means is configured to correct the output value in a direction to reduce the difference in time length between the positive period and the negative period of the tracking error signal within the predetermined track length, whereby a large track bend can be prevented. Therefore, when the decrease of the reproduction signal amplitude cannot be avoided, the amplitude decrease period can be suppressed and the influence can be suppressed to the minimum.

Further, the control signal generating means may be configured to output an average value of the tracking error signal or an average value of an excess amount from the predetermined value during a period in which the absolute value is equal to or larger than the predetermined value within the predetermined track length. For example, tracking control can be performed with a target at a position where the effect on the reproduction signal quality is minimized.

As described above, the present invention provides an information reproducing apparatus which gives the best reproduction signal quality when reproducing the information on the tape which is relatively affected by the track bending due to the narrowed track. It is a thing.

[Brief description of drawings]

FIG. 1 is a block diagram of an information reproducing apparatus according to an embodiment of the present invention.

FIG. 2 is a signal waveform diagram for explaining an embodiment of the present invention.

FIG. 3 is a flowchart showing an algorithm of the control signal generator in the embodiment of the present invention.

FIG. 4 is a flowchart showing another algorithm of the control signal generator in the embodiment of the present invention.

FIG. 5 is a flowchart showing another algorithm of the control signal generator in the embodiment of the present invention.

FIG. 6 is a schematic diagram for explaining the problems of the conventional information reproducing apparatus.

[Explanation of symbols]

 1 head 2 tracking error detection circuit 3 control signal generator 4 tracking control means 8 tape

Claims (4)

[Claims] 1. A head for scanning a track on which information tracks containing a tracking pilot signal are formed and outputting a reproduction signal, and a tracking pilot signal in the reproduction signal, which causes a tracking error in head scanning with respect to the track. Tracking error detecting means for detecting, a control signal creating means for creating a tracking error signal for controlling a scanning position by the head according to a track bending pattern indicated by the tracking error signal, and an output of the control signal creating means. An information reproducing apparatus comprising: a tracking control unit that controls the track scanning position of the head in response to the information. 2. The information reproducing apparatus according to claim 1, wherein the control signal generating means outputs an average of the maximum value and the minimum value of the tracking error signal within a predetermined track length. 3. The control signal generating means corrects the output value in a direction to reduce the difference between the time lengths of the positive period and the negative period of the tracking error signal within a predetermined track length. Information reproduction device. 4. The control signal generating means outputs an average value of the tracking error signal or an average value of an excess amount from the predetermined value during a period in which the absolute value is equal to or larger than the predetermined value within a predetermined track length. The information reproducing device according to claim 1.