KR910009468B1 - Position error automatic correcting circuit for head drum - Google Patents

Abstract

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Description

Automatic correction of mechanical position error of head drum

The accompanying drawings are detailed circuit diagrams showing embodiments of the automatic correction circuit of the present invention.

* Explanation of symbols for the main parts of the drawings

10: operation pulse signal generation unit 20: vertical synchronization signal input determination unit

30: counter 40: decoder

50: electronic variable resistance AD ₁ : end gate

OR ₁ , OR ₂ : ORA gate HD: Head switching signal

HS: Horizontal Sync Signal VS: Vertical Sync Signal

IV ₁ : Inverter

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a mechanical position error automatic correction circuit of a head drum which corrects the mechanical position error of two video heads provided in a rotating head drum in a video tape recorder.

In the cylindrical rotating head drum, two image heads are installed while maintaining an angle of 180 ° to each other. In addition, these two video heads do not accurately track the track on which the video tape program is recorded, and thus the program cannot be reproduced optimally, and a number of noise signals are mixed with the reproduced signal.

Therefore, manufacturers of rotating head drums install two image heads to maintain exactly 180 ° of each other when using a microscope to fix the image head to the rotating head drum. An error occurred.

In order to correct such a mechanical position error, conventionally, the time interval from the rising time and the falling time of the 30 Hz head switch signal for switching the video head to the time when the vertical synchronization signal of the reproduced video signal is generated is exactly 6.5H (where H The time constant of the head delay mono multivibrator is adjusted with two variable resistors.

However, it is very difficult to correct mechanical position error using two potentiometers, which is not only time-consuming and requires considerable skill, but also video recorded with a video tape recorder with mechanical position error on a rotating head drum. There was a problem in that the tape could not be corrected when playing a video tape recorder without mechanical position error.

Therefore, the object of the present invention is to automatically correct the mechanical position error of the two image heads installed on the rotating head drum, thereby preventing the confusion of the difference on the video tape and the mechanical position error, and can always reproduce a stable picture. It is to provide a mechanical position error automatic correction circuit.

The mechanical position error correction circuit of the present invention having the above object counts the horizontal synchronizing signal in the trace interval of the first and second image heads, and uses the counted number of horizontal synchronizing signals to switch the current. After recognizing the point, the error amount is detected, and the mechanical position error is corrected by controlling the electronic variable resistor according to the detected error amount and adjusting the time constant of the head delay mono multivibrator.

Hereinafter, with reference to the accompanying drawings will be described in detail the automatic correction circuit of the present invention.

The accompanying drawings are detailed circuit diagrams showing an embodiment of the automatic correction circuit of the present invention for correcting the mechanical position error of the first image head among two image heads. As shown therein, the 30 Hz head switching signal HD is a capacitor. The mono-multivibrator is connected to the cathode of the ground resistor R ₁ and the diode D ₁ via (C ₁ ), and the connection point thereof is connected to the time constant circuit of the resistor (R ₂ ) and the capacitor (C ₂ ). The operation pulse signal generator 10 was configured by connecting to the trigger terminal T ₁ of (11).

)에 접속하여 수직 동기신호 입력 판별부(20)를 구성하였다.And connecting the output terminal (OT ₁₎ of the mono-multivibrator 11, to one side input terminal of the AND gate (AD _1), and the other input terminal connected to be applied with the vertical synchronizing signal (VS) of the AND gate (AD ₁₎ The output terminal of the AND gate AD ₁ is connected to the trigger terminal T ₂ of the mono multivibrator 21 to which the time constant circuit of the resistor R ₃ and the capacitor C ₃ is connected. The output terminal OT ₂ of 21 is an enable terminal of the counter 30 (

), A vertical synchronization signal input discrimination unit 20 is constructed.

Further, connecting the output terminal (OT ₁₎ of the mono-multi Bob concentrator 11 to the one side input terminal of the AND gate (AD _2), and the other input terminal of the AND gate (AD ₂₎ is applied to the horizontal synchronizing signal (HS) The output terminal of the AND gate AD ₂ was connected to the clock terminal CK of the counter 30.

)는 앤드 게이트(AD₃~AD₁₇)로 구성된 디코더(40)의 입력단자에 접속하고, 앤드 게이트(AD₁₇)의 출력단자는 카운터(30)의 리세트 단자(RST)에 접속하며, 앤드 게이트(AD₃~AD₁₇)로 구성된 디코더(50)의 입력단자에 접속함과 아울러 앤드 게이트(AD₃~AD₈)(AD₉~AD₁₇)의 출력단자를 오아 게이트(OR₁)(OR₂)를 통해 전자식 가변저항(50)의 플러스 조절단자(CTL₊) 및 마이너스 조절단자(CTL_-)에 각기 접속하며, 전자식 가변저항(50)의 제어단자(CS)에는 상기 모노 멀티바이브레이터(21)의 출력단자(OT₂)를 인버터(IV₁)를 통해 접속하여 전자식 가변저항(50)의 출력단자(OUT)를 접지 콘덴서(C₄) 및 헤드지연 모노 멀티바이브레이터의 트리거단자에 접속하여 구성하였다.Output terminals Q0 to Q3 of the counter 30 (

) Is connected to the input terminal of the decoder 40 composed of AND gates AD ₃ to AD ₁₇ , and the output terminal of the AND gate AD ₁₇ is connected to the reset terminal RST of the counter 30. It is connected to the input terminal of the decoder 50 composed of (AD ₃ to AD ₁₇ ), and the output terminal of the AND gates (AD ₃ to AD ₈ ) (AD ₉ to AD ₁₇ ) is connected to the gate (OR ₁ ) (OR ₂ ). and each connected to), the electronic include the mono-multivibrator (21 a control terminal (CS) of the variable resistor ₅₀₎₎ electronic plus adjustment of the variable resistor 50, terminal (CTL ₊₎ and a negative control terminal (CTL via to the output terminal (OT ₂₎ connected through an inverter (IV ₁₎ was constructed by connecting the output terminal (OUT) of the electronic variable resistor 50 to the trigger terminal of a ground capacitor (C ₄₎ and the head delayed mono multivibrator .

The mechanical position error correction circuit of the second image head is configured in the same manner as the correction circuit for correcting the mechanical position error of the first image head as described above, and the head switching signal HD is transferred to the inverter IV ₂ . Invert to input.

In the description of the drawings, reference numeral B ₊ denotes a power source.

In the dual position error correction circuit of the present invention configured as described above, when the 30 Hz head switching signal HD is input while the power supply B ₊ is applied, the input head switching signal HD is a condenser C ₁ and Differentiated through the resistor R ₁ , the negative differential pulse signal is removed by the diode D ₁ , and the positive differential pulse signal is applied to the trigger terminal T ₁ of the mono multivibrator 11.

Then, the mono multivibrator 11 is triggered to output a high potential pulse signal for about 1.2 msec, which is a time constant time set to the values of the resistors R ₂ and condenser C ₂ , and the output high potential pulse signal is Since it is applied to one input terminal of the gates AD ₁ and AD ₂ , the AND gate AD ₂ is applied to the clock terminal CK of the counter 30 that outputs the horizontal synchronization signal HS applied to the other input terminal thereof. do.

)에 인가되므로 카운터(30)는 인에이블되어 앤드 게이트(AD₂)가 출력하는 수평동기신호(HS)를 카운트하게 된다.At this time, the mono multi-varbrator 21 is not triggered to output a low potential to the output terminal OT ₂ , and the output low potential is an enable terminal of the counter 30 (

The counter 30 is enabled to count the horizontal synchronization signal HS output from the AND gate AD ₂ .

When the vertical synchronizing signal VS is input while the counter 30 counts the horizontal synchronizing signal HS, the input vertical synchronizing signal VS is applied to the other input terminal of the AND gate AD ₁ . , wherein the aND gate one input terminal, it is applied to the high-potential output to the mono-multivibrator 11, aND gate (AD ₁₎ is the vertical sync applied to the other input signal (VS) as described above in (AD ₁₎ Is output to the trigger terminal T ₂ of the mono multivibrator 21.

)에 인가됨과 아울러 인버터(IV₁)를 통해 저전위로 반전되어 전자식 가변저항(50)의 제어단자(CS)에 인가되므로 카운터(30)는 인에이블되지 않아 수평 동기신호(HS)의 카운트를 정지하고, 전자식 가변저항(50)은 정상 동작하게 된다.Then, the mono multi-vibrator 21 is triggered and outputs a high potential pulse signal for about 0.8 msec, which is a time constant time set to the values of the resistor R ₃ and the capacitor C ₃ to enable the counter 30. Terminals(

In addition to being applied to the control terminal CS of the electronic variable resistor 50 after being inverted to the low potential through the inverter IV ₁ , the counter 30 is not enabled, so that the count of the horizontal synchronizing signal HS is stopped. Then, the electronic variable resistor 50 is operated normally.

In this state, the number of horizontal synchronization signals HS counted by the counter 30, that is, the horizontal synchronization signals HS input from the time when the head switching signal HD is input to the time when the vertical synchronization signal VS is input. ) Is output to the output terminals Q ₀ to Q ₃ and Q ₀ to Q ₃ , decoded by the AND gates AD ₃ to AD ₁₇ of the decoder 40, and then input to the electronic variable resistor 50. do.

Therefore, the electronic variable resistor 50 adjusts the time constant of the head delay mono multivibrator while being varied according to the output signal of the decoder 40 to correct the mechanical position error.

The preset value of the electronic variable resistor 50 is set to 2.636 msec when the angle of the image head is 20 degrees. In order to determine a correction direction from the preset value, the output signal of the AND gates AD ₃ to AD ₈ of the decoder 40 is logically summed with the OR gate OR ₁ , and then the positive adjustment of the electronic variable resistor 50 is performed. It is applied to the terminal (CL ₊ ) and used as the positive side control signal, and the output signal of the AND gates (AD ₉ to AD ₁₇ ) is ORed to the OR gate (OR ₂ ), and then the negative adjustment terminal of the electronic variable resistor (50). (CTL _-) Iowa is applied using a negative-side regulation control signal, while when the number of counts a horizontal synchronizing signal (HS) 6 or fewer, the output of the selective high potential to the aND gate (AD ₃ ~ AD ₈₎ to the gate (OR ₁ ) outputs a high potential, adjusts the time constant of the head delay mono multivibrator in the positive direction, and when the number of counted horizontal synchronizing signals (HS) is 6 or more, the AND gates (AD ₉ to AD ₁₇ ) Selectively outputting a high potential The agate OR ₂ outputs a high potential to adjust the time constant of the head delay mono multivibrator in the negative direction.

When the vertical synchronizing signal VS is not input for 1.2 msec time when the mono multi vibrator 11 outputs a high potential, the time constant time of the mono multi vibrator 21 has elapsed to its output terminal OT ₂ . The output low potential is inverted to high potential through the inverter (IV ₁ ) and then applied to the positive control terminal (CTL ₊ ) of the electronic variable resistor (50) through the OR gate (OR ₁ ) to time constant of the head delay mono multivibrator. Is corrected to 0.8msec in the positive direction.

This operation is repeated as the head switching signal is input to correct the mechanical position error of the rotating head drum. That is, when the image head is installed at an angle of 20 ° to the rotating head drum, the center point of the switching point is variably adjusted in the range of 96 to 3.306 msec.

As described in detail above, the mechanical position error correction circuit of the present invention automatically corrects the mechanical position error of the rotating head drum, thereby reducing the number of manufacturing tasks of the rotating head drum, thereby improving productivity, and switching according to video tape. By compensating for the instability of the playback screen due to the difference in points, not only a stable screen can be obtained, but also the quality of the product can be improved and the competitiveness of the product can be strengthened.

Claims (1)

An operation pulse signal generator 10 which is triggered by the head switching signal HD and outputs a high potential for a set time, and outputs a horizontal synchronization signal HS according to the output signal of the operation pulse signal generator 10. An AND gate AD ₂ , a vertical sync signal input discrimination unit 20 triggered by a vertical sync signal VS input after the operation pull signal generator 10 is triggered, and outputting a pulse signal; The AND gate AD ₂ is enabled by the output signal of the vertical synchronizing signal input determining unit 20 and is output from the input of the head switching signal HD until the vertical synchronizing signal VS is input. A counter 30 for counting a horizontal synchronization signal HS, a decoder 40 for decoding the output signal of the counter 30, and a head delay mono while varying a resistance value according to the output signal of the decoder 40. To change the time constant of the multivibrator When the number of child variable resistors 50 and the horizontal synchronization signal HS counted by the counter 30 is 6 or less, the vertical synchronization signal when there is no vertical synchronization signal VS as the output signal of the decoder 40. the output signal of the signal input discrimination section 20 to the output signal of the inverter (IV ₁₎ of inverting and Iowa gate (OR ₁₎ for adjusting the time constant of the head is delayed mono-multivibrator in the positive direction, the counter 30 When the number of the horizontal synchronization signal (HS) counted to 6 or more, the output signal of the decorner 40 is composed of an ora gate (OR ₂ ) for adjusting the time constant of the head delay mono multivibrator in the negative direction Automatic mechanical position error correction circuit for the head drum.

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