KR950008752B1 - Automatic gain variable type tracking control device for vcr - Google Patents

Abstract

first and second gain adjusting units for adjusting head deviation voltage gains outputted from first and second level detecting units; a voltage comparing unit for comparing the output voltages of the first and second gain adjusting units to output a tracking error signal; and a microcomputer for controlling a capstan motor in accordance with the tracking control signal of the voltage comparing unit and for outputting a gain control signal to the first and second gain adjusting units.

Description

VRC's automatic gain variable tracking control

1 is a block diagram of a conventional tracking control device.

2 is a block diagram of an automatic gain variable tracking control device of the present invention.

(A) is a pilot signal state diagram recorded on a tape, (b) is a pilot signal value table according to a selection signal, and (c) is a balanced modulated pilot signal state diagram.

(A)-(k) of FIG. 4 are each input / output waveform diagram of FIG. 2 when a head is biased to the right.

* Explanation of symbols for main parts of the drawings

10 low pass filter 20 balance modulator

30A, 30B: Band pass filter 40A, 40B: Level detector

50A, 50B: gain control unit 60: voltage comparison unit

70: micom 80: pilot signal generator

V-HD: Video Head CM: Capstan Motor

According to the present invention, an automatic gain of a V-Cal to automatically obtain an optimal image by automatically varying the level of a tracking error signal during an automatic tracking-finding process for phase control of a capstan motor in a VCR regeneration mode. A variable tracking control device.

In general, VCRs feature Auto Tracking Finding, which controls the phase of the capstan motor in playback mode, allowing the head to accurately track the tracks on the tape to achieve optimal viewing.

The conventional tracking control device for performing this function is a pilot in a high frequency signal read from a tape by the recording / playback switching switch SWl and the video head V-HD, as shown in FIG. A low pass filter 10 for passing only a signal, and a balanced modulator for generating a tracking control signal by modulating a pilot signal output from the low pass filter 10 and a pilot signal generated by the pilot signal generator 80 ( 20), a first band pass filter 30A for passing only 16 KHz components of the output signal of the balanced modulator 20, and a second band pass filter for passing only 46 KHz components of the output signal of the balanced modulator 20; First and second level detection units 40A and 40B for detecting the levels of the 16 KHz and 46 KHz components output to the unit 30B, the first and second band pass filter units 30A and 30B. , The tracking error signal by comparing the output signals of the second level detectors 40A and 40B. It receives the tracking error signal of the voltage comparator 60 and the voltage comparator 60 to output the output from the microcomputer 70 and the microcomputer 70 to control the overall operation of the system including the capstan motor (CM) The pilot signal generator 80 and the pilot signal generator comprising a crystal resonator 81 and a divider 82 which determine the division ratio of the crystal resonator by generating the selected signals SEL1 and SEL2. And a mixing section 90 for mixing the pilot signal produced at 80 into a video signal to be recorded and outputting it to the video head V-HD.

When the video head V-HD reads a high frequency signal from the magnet tape in the playback mode in the conventional tracking control device configured as described above, the signal is passed through the low pass filter unit 10 through the recording / playback switching switch SW1. In this case, the high frequency signal includes a video signal and a pilot signal for automatic tracking finding.

The low pass filter unit 10 having a cutoff frequency of 200 KHz passes only the pilot signal among the input signals, and the extracted pilot signal is input to the balance modulator 20.

At this time, the pilot signal generator 80 receives the selection signals SEL1 and SEL2 output from the microcomputer 70 and divides the natural vibration frequency f ₀ of the crystal resonator 81 by the frequency divider 82. The division ratio N is determined, and the pilot signal generated by the divider 82 is applied to the balance modulator 20 and the mixer 90.

The balance modulator 20 balances and modulates a pilot signal output from the low pass filter unit 10 and the pilot signal generator 80 to generate a 16KHz component and a 46KHz component, which are tracking control signals. By passing through the second band pass filter part 30A, 30B, it separates into a 16KHz component and a 46KHz component.

The first level detector 40A detects the level of the 16KHz component, and the second level detector 40B detects the level of the 46KHz component and the voltage indicating the degree of head deviation from the track of the tape is two level detectors. It is output from 40A and 40B.

The voltage comparator 60 compares the two voltages and generates a tracking error signal according to the degree of head bias. The signal is input to the microcomputer 70 to move the tape from the microcomputer 70. It is a reference when controlling the phase of.

As described above, when the head traces a track continuously formed on the tape, a pilot signal recorded on the tape is detected so that the center of the track can be traced. The phase of the capstan motor was controlled by inputting it to the microcomputer as a signal.

However, in this method, the motor control signal according to the tracking error signal is already set in the micom, and the control signal is compensated for the head bias by outputting the control signal according to the tracking error signal currently input to the capstan motor. However, tracking control was performed irrespective of the head state, and thus an optimal screen state was not obtained.

SUMMARY OF THE INVENTION The present invention has been made to solve the conventional problems as described above, and an object of the present invention is to properly control the gain of left and right bias voltages according to the degree of head bias from the current tape when generating a tracking error signal using a pilot signal By providing a tracking error signal amplified than the actual value tracking control is proceeded faster to obtain an optimal image of VAL automatic gain variable tracking control device.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to FIGS. 2 to 4 as follows.

2 is a block diagram of an automatic gain variable tracking control device according to the present invention. The low pass allows only a pilot signal to pass through a high frequency signal read from a tape by a recording / playback switch SW1 and a video head V-HD. A balance modulator 20 for balancing the pilot signal output from the filter unit 10 and the low pass filter 10 and the pilot signal generated from the pilot signal generator 80 to produce a tracking control signal, and a balance A first band pass filter part 30A for passing only 16 KHz components of the output signal of the modulator 20, a second band pass filter part 30B for passing only 46 KHz components of the output signal of the balanced modulator 20, and And first and second level detectors 40A and 40B for detecting the levels of the 16KHz and 46KHZ components output from the first and second band pass filter units 30A and 30B and outputting the head bias voltage. The second according to the gain control signal of 70; First and second gain control units 50A and 50B for adjusting the gain of the head bias voltage output from the first and second level detection units 40A and 40B, respectively, and first and second gain adjustments. The voltage comparator 60 which compares the output voltages of the units 50A and 50B and outputs a tracking error signal, and receives the tracking error signal of the voltage comparator 60 and includes a capstan motor CM. The crystal resonator 81 and the frequency divider which determine the division ratio of the oscillation signal by the microcomputer 70 for controlling the entire operation, the selection signals SEL1 and SEL2 output from the microcomputer 70, and generate a pilot signal. A pilot signal generation unit 80 of 82, and a mixing unit 90 for mixing the pilot signal generated by the pilot signal generation unit 80 with the video signal to be recorded and outputting it to the video head V-HD. have.

The operation of the present invention configured as described above will be described based on the waveform diagram of FIG.

First, the pilot signal will be described. As shown in FIG. 3A, the pilot signal (hatched portion) is recorded in the tape traveling in the A direction perpendicular to the head travel direction B for each track. The pilot signal values according to the selection signals SEL1 and SEL2 of 70 are shown in table form in FIG.

FIG. 3 (c) shows a balanced modulated pilot signal state, which shows the difference component frequencies between the magnetic frequency and the left and right frequencies when the head traces the left and right tracks other than the magnetic tracks together.

Suppose that the tape advances a little faster when the VCR is in playback mode, so that the video head (V-HD) is twisted to the right and tracks the tracks on the track of the tape as shown in Figure 3 (a). Similarly, the two heads A and B alternately trace the track and read a high frequency signal as shown in FIG. _4B . At this time, the pilot magnetic frequency is sequentially changed to f _l -f ₄ in accordance with head switching.

The high frequency signal is input to the low pass filter unit 10 through the recording / playback switching switch SW1, and the low pass filter unit 10 passes only the pilot signal among the input signals, and the extracted pilot signal is balanced. 20).

At this time, the pilot signal generator 80 receives the selection signals SEL1 and SEL2 of the microcomputer 70 from the frequency divider 82 and divides the natural vibration frequency f ₀ of the crystal resonator 81. The ratio N is determined (see FIG. 3B), and the pilot signal generated by the divider 82 is applied to the balance modulator 20 and the mixer 90.

The balanced modulator 20 receives the pilot signal output from the pilot signal generator 80, that is, the frequency of the current track, and receives the pilot signal from the low pass filter 10 to balance modulate the third signal. As shown in (c) of FIG. 3, a 16 KHz component and a 46 KHz component, which are frequency differences between magnetic frequencies and adjacent track frequencies, are generated.

At this time, the l6KHz component and the 46KHz component are information indicating how far the head currently being traced from the tape is twisted left and right.

The output signal of the pop-shaped modulator 20 passes through the first and second band pass filter units 30A and 30B, and has a 16KHlz component such as (c) of FIG. 4 and a 46KHz component such as (d) of FIG. Are separated.

Here, it is assumed that the phase of the current tape is a little faster, so if the l6KHz component is large, the 46KHz component is small, if the 46KHz component is large, the 16KHz component is smaller, and f ₁ , f ₃ is larger than the 46KHz component. ₂ , f ₄ means that the tape advances faster when the 46KHz component is greater than the 16KHz component.

The first level detector 40A detects the level of the 16KHz component and outputs the head bias voltage as shown in FIG. 4E to the first gain adjuster 50A, and the second level detector 40B outputs the 46KHz component. Detects the level of and outputs the voltage as shown in FIG. 4 (f) to the second gain adjusting unit 50B.

The first and second gain adjusting units 50A and 50B increase or decrease the gains of the 16 KHz component and the 46 KHz component according to the gain control signal of the microcomputer 70. The microcomputer 70 uses the current head as the input tracking error signal. The gain control signal as shown in (g) of FIG. 4 is transferred to the first gain adjusting section 50A, and the gain control signal as shown in (h) of FIG. 4 is transferred to the second gain adjusting section 50B. By outputting each, f ₁ and f ₃ increase the gain of the 16KHz component while reducing the gain of the 46KHz component, while f ₂ and f ₄ control the gain on the contrary.

Then, the first gain control unit 50A outputs a signal whose gain is adjusted as shown in (i) of FIG. 4, and the second gain control unit 50B outputs a signal such as (j) of FIG. Depending on the amount the head is shifted to the right, the tracking error signal becomes larger than it actually is.

The voltage comparator 60 compares the two output voltages of the first and second gain adjusters 50A and 50B, and the tracking error signal is amplified than the actual one by gain control as shown in FIG. 4 (k). The microcomputer 70 generates a motor control signal corresponding to the input tracking error signal to control the capstan motor CM, and uses the tracking error signal to achieve first and second gains. The gain of the adjusting unit 50A, 50B is determined.

On the other hand, when the advancing of the tape is a little slow, the control is performed in a manner opposite to that described above.

As described above, the present invention does not control the phase of the capsdon motor using the tracking error signal as it is when tracking control using the pilot signal, but the 16KHz component and the 46KHz component according to the degree of head bias from the current tape. By properly controlling the level gain to generate a tracking error signal amplified than the actual value, the tracking control proceeds more quickly, resulting in a clearer image.

Claims (1)

First and second gain adjusting units 50A and 50B for adjusting the gain of the head bias voltage output from the first and second level detectors 40A and 40B, respectively, and the first and second gain adjusting units ( A voltage comparator 60 for comparing the output voltages of 50A and 50B and outputting a tracking error signal, and controlling the capstan motor according to the tracking error signal of the voltage comparator 60, and controlling the gain control signal to the first and second signals. A variable gain tracking control device of V-C, comprising a microcomputer 70 outputting to two gain control units 50A and 50B.