KR930004659Y1 - Automatic image control circuit of tv system - Google Patents

Abstract

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Description

TV's automatic image control circuit

1 is a conventional automatic image control circuit diagram.

2 is an automatic image control circuit of the present invention (TV).

3 is a relationship between the amount of contrast and the relative sensitivity in FIGS. 1 and 2;

4 is a detailed circuit diagram of FIG.

* Explanation of symbols for main parts of the drawings

1: Intermediate image amplification and detector 2: Color signal processor

3: luminance signal filter 4: high-pass correction amplifier

5: contrast amplifier 6: color demodulator

7: Micom 8 ~ 10: D / A converter

20: high frequency correction control part Vi: video intermediate frequency signal

Vo: Color difference output

The present invention relates to an automatic image control circuit of a television. Especially, when the sharpness control level of the image control circuit is constant, it is suitable for eliminating the decrease in the sharpness caused by the variation of the contrast amount of the image. It relates to an automatic image control circuit of a (TV).

In the conventional TV image processing circuit which is generally used, as shown in FIG. 1, an image intermediate frequency signal Vi from a tuner (not shown) is provided at a predetermined level in the image intermediate frequency amplification and detection unit 1. And the detected video signal is detected only by the luminance component through the luminance signal receiver 3 and then the control signal VS of the DC level applied from the microcomputer 7 through the D / A converter 8. By the high frequency correction amplifier (4) is performed for the high frequency correction.

Meanwhile, the contrast amplifier 5 which receives the control voltage from the microcomputer 7 through the D / A converters 9 and 10 sufficiently amplifies the separated luminance signal and inputs the chromaticity signal input through the chroma signal processor 2. In addition, the color demodulator 6 is configured to obtain a color difference signal Vo for driving the output circuit of the water pipe (not shown).

Referring to the conventional TV image processing circuit configured as described above the operation and a number of problems with the circuit in detail as follows.

First, the image intermediate frequency signal Vi output from the tuner (not shown) is amplified and detected at a predetermined level by the image intermediate frequency amplifier and detector 1, and then the chroma signal is removed through the luminance signal filter 3. Only the video signal of the luminance component is applied to the high pass correction amplifier 4.

At this time, the high frequency compensation amplifier 4 is applied.

At this time, the high pass compensation amplifier 4 acts to attenuate or increase the transfer characteristic of the high frequency of the luminance signal, and the control output VS of the microcomputer 7 converted to direct current through the D / A converter 8. It is possible to increase or decrease the characteristics of the high frequency band so that the finally reproduced video signal is set to have an appropriate level of top view and a channel correction curve according to the viewer's preferences and the characteristics of the video signal.

On the other hand, the video signal output of the luminance component corrected by the high frequency compensation amplifier 4 is input to the contrast amplifier 5 and fully amplified, and the control of the microcomputer 7 through the D / A converters 9 and 10 is performed. In accordance with the signals VB and VC, an image signal of a luminance component is applied to the color demodulator 6 together with the chroma signal processed by the chroma signal processing unit 2 so as to drive a color difference signal necessary for driving the output circuit of the water pipe (not shown). Generates outputs (RY, GY, BY, -Y).

However, in the conventional circuit as described above, since contrast and brightness control independently control the image, the relative image sharpness, that is, the linearity of the image changes according to the change in the contrast, and the viewer in particular. If you adjust the contrast or brightness according to the surrounding brightness while the contour correction amount is fixed constantly, the contour correction amount is relatively emphasized when the contrast is large visually, and when the contrast is low, the contour correction amount is greatly reduced. There is a defect that the relative sharpness characteristic of the image is lowered.

Therefore, the objective of this paper is to compensate the high frequency of the luminance component signal relatively large when the contrast or brightness is below a certain level, and visually maintain the constant contour compensation by lowering the gain of the high frequency when the contrast or brightness is set higher than a certain level. Another aspect of the present invention is to provide an automatic image control circuit of a TV for maintaining the top view of an image.

2 is a circuit diagram of the present invention, as shown therein, an image intermediate frequency amplification and detection unit 1 which amplifies and detects an image intermediate frequency signal Vi from a tuner (not shown) to a predetermined level, and A high frequency correction amplifier for correcting the high frequency component of the luminance signal by the luminance signal filter 3 separating the luminance signal from the video signal and the DC level applied from the microcomputer 7 through the D / A converter 8; (4), a contrast amplifier 5 which amplifies the separated luminance signal to a sufficient level, and generates a color difference signal Vo by demodulating the separated luminance signal and the chroma signal inputted through the chroma signal processor 2 A color demodulator 6, a D / A converter 8-10 for receiving a digital control signal necessary for the correction of the luminance signal from the microcomputer 7, and converting it into an analog signal, and the D / A converter 8-8. 10) Contour correction signal (VS) and contrast signal through And a high pass correction control unit 20 which receives the VC and the brightness signal VB and adds them to generate a control signal for correcting the high range of the luminance signal.

On the other hand, the high frequency correction control unit 20 according to the present invention has a configuration of a detailed circuit as shown in Figure 4, the control from the D / A converter (9, 10) through the resistor (R7), (R8) The signals VC and VB are applied to the contrast amplifier 5 and the anodes of the ground resistors R4, R10 and diodes D2 and D1 through the resistors R5 and R11. Are applied to the cathodes of the diodes D1 and D2, respectively.

The emitter of the transistor Q1 is grounded and its collector is connected to the control input terminal C1 of the high frequency compensation layer aerator 4 through the resistor R3 and the resistance of the D / A converter 8. It is connected to (R2).

Referring to the operation and effects of the TV automatic image control circuit of the present invention configured as described above in detail as follows.

First, the present invention is to set the sharpness (Sharpness) to any constant value and to eliminate the deterioration of the sharpness when varying the contrast or brightness, which is performed by the following action.

That is, the image intermediate frequency signal Vi output from the tuner (not shown) is amplified by the image intermediate frequency amplification and detector 1, and the carrier is removed to be applied to the luminance signal filter 3 to separate the luminance signal. The signal is again corrected by the high frequency compensation amplifier 4 in accordance with the control signal VS. On the other hand, the contrast amplifier 5 receives the image signal of the luminance component corrected from the high frequency compensation amplifier 4, and applies it to the color demodulator 6 together with the chromaticity output signal of the chromaticity signal processor 2 to receive the water pipe ( Color difference signals (RY, GY, BY, -Y) required for driving the output circuit (not shown) are generated.

In addition, the gain control terminal C1 of the high frequency compensation amplifier 4 is used to control the transmission characteristics for the high frequency frequency of the luminance signal by the control signal of the DC level, and the contrast amplifier 5 is the control terminal C2. The gain of the luminance signal component of the video signal is controlled by the control signal of the DC level applied through the control circuit, and the brightness of the video signal is adjusted by the DC bias applied through the control terminal C3.

On the other hand, when the microcomputer 7 sends a digital control signal to the D / A converters 8 to 10 to control the image quality, the D / A converters 8 to 10 convert the signal into an analog signal and then the high range. It is applied to the correction amplifier 4 and the contrast amplifier 5 to increase or decrease the gain of the luminance signal or to reduce the DC bias of the luminance signal to maintain the desired contrast and brightness desired by the viewer. The control on the contrast amplifier 5 The signals VC and VB are mixed with each other in the high pass compensation controller 20 according to the present invention together with the contour correction signal VS through the D / A converter 8 and the control signal input terminal C1 of the high pass compensation amplifier 4. Is applied.

According to the present invention, the control signal applied to the control input terminal (X1) of the high frequency compensation amplifier (4) controls the gain of the high frequency compensation amplifier (4) to control the contrast level of the luminance signal, that is, the contrast static voltage The image quality is improved according to the magnitude of (VC) or the brightness control voltage VB of the luminance signal.

In general, the sensory characteristics of the human vision are that the sensitivity of the vision is increased when the contrast or brightness of the image signal is high, and the sensitivity of the vision is relatively decreased when the contrast or brightness of the image signal is low.

Therefore, when the viewer sets the contour correction amount of the image to any specific value, it is necessary to ensure that the sharpness remains constant regardless of the change in the contrast or brightness setting of the image signal.

On the other hand, the degree of contrast and brightness can be confirmed by the level of the control voltage (VC, VB) to control this, the present invention uses this value for the correction of the high frequency.

That is, the outputs VC and VB of the D / A converters 9 and 10 that control contrast and brightness are inverted, and this signal is added together with a constant contour correction amount VS output from the D / A converter 8. If the externally set contrast and brightness are below a certain level, the gain of the high frequency compensation amplifier 4 is increased to compensate for the high frequency relatively largely. On the contrary, if the externally set contrast or brightness is above a certain level, the trade When the gain of the high frequency signal is lowered by the control signal applied to the control input terminal C1 of the correction amplifier 4, the image signal is selected from the luminance component and the gain of the high frequency frequency is selected by the viewer for the fixed contour correction amount of a predetermined level. By changing the contrast or the brightness in response to a constant contour correction characteristic or the sharpness of the image can be maintained at all times.

When the circuit of the fourth invention performs such an operation quantitatively described as follows.

If the control signal input to the high-frequency correction amplifier 4 is Vc ₁ , then Vc ₁ = VS + (-VC-VB) = VS-VC-VB ... (1).

That is, as the control signal VC specifying the level of contrast and the control signal VB specifying the brightness increase, the control output Vc ₁ decreases relatively, and when the control signals VC and VB decrease, The control output Vc ₁ is increased.

If the contrast or brightness is changed when the contour correction amount VS is set to a constant value, the gain control signal Vc ₁ of the high pass compensation amplifier 4 is changed in accordance with the above formula (1), thereby automatically. This allows correction of gain.

That is, if the contrast and brightness set by the user are below a certain level, the gain of the high frequency compensation amplifier 4 is increased to compensate the high frequency relatively largely. On the contrary, when the contrast or brightness set from the outside is a certain level or higher, the high frequency is set. Will compensate for the low signal.

Hereinafter, the relationship between the equation (1) is established by the high-pass correction control unit 20 as follows.

First, the contrast control signal (VC) brightness control signal (VB) output from the D / A converters (9) and (10) is connected to the transistors (Q1) through diodes (D1) and (D2), respectively serving as an ora gate. If the contrast control signal VC and the brightness control signal VB increase, the voltage drop in the resistors R4 and R10 increases to increase the base current of the transistor Q1. .

Accordingly, since the transistor Q1 acts as an inverting amplifier with its output drawn from the collector resistor R3, the voltage drop V that appears in the resistor R2 due to the increase in the collector current flowing through the resistors R2 and R3. _R2 ) will also increase.

However, the high control signal (V _R1) which is input to the correction amplifier 4 is V _C1 = a contour correction signal (VS), - the voltage drop of the resistor (R2) (V _R1) ..... (2), so that a constant It can be seen that the high frequency correction control signal V _C1 is inversely proportional to the contrast control signal VC and the brightness control signal VB with respect to the contour correction signal VS.

Therefore, if the contrast and brightness are below a certain level, the gain for the high frequency compensation amplifier 4 becomes large, and the high frequency is relatively largely compensated. On the contrary, if the contrast or brightness set externally is above a certain level, the high frequency signal The low compensation ensures a constant contour correction sensitivity at all times, regardless of contrast or brightness.

On the other hand, Figure 3 shows the visual sensitivity of the contour correction amount with respect to the change in contrast compared to the conventional circuit, the conventional circuit shows a characteristic (linear A) that the visual sensitivity of the contour correction amount is proportional to the contrast amount However, the present invention shows a constant contour correction sensitivity regardless of the amount of contrast (straight line B), so that the viewer can feel the contour correction amount arbitrarily set regardless of the magnitude of the contrast.

As described in detail above, the present invention corrects the high frequency of the luminance component in the high frequency compensation amplifier in response to the size of the viewer whenever the viewer adjusts the contrast or the brightness for a constant contour correction amount to improve the visual sensitivity of the image diagram. By maintaining a constant, there is an effect of providing a high quality, high-quality TV (TV) by removing the deterioration of the image quality due to the change in contrast or brightness.

Claims (2)

In the TV image control signal, a contrast control signal VC and a brightness control signal VB are added to the contour correction signal VS to the contour correction signal VS, and when the contrast is above a certain level, the luminance component is high. High frequency compensation control unit 20 that applies a control signal to TV high frequency compensation amplifier 4 to compensate for the low frequency and to compensate the gain of the high frequency of the luminance component when the contrast is below a certain level to maintain a visually constant contour correction amount. TV automatic image control circuit comprising a. The high frequency compensation control unit 20 is characterized in that the contrast control signal VC and the brightness control signal VB pass through the resistors R5 and R11, respectively, and then the ground resistors R4 and R10, respectively. Applied to the anodes of diodes D2 and D1, respectively, the cathodes of diodes D1 and D2 are connected to the base of transistor Q1, and the collector resistor R3 of transistor Q1 is contour correction control. And a high frequency correction control signal (V _C1 ) of the television, which is commonly connected to the other terminal of the resistor (R2) to which the signal (VS) is applied, and outputs the high frequency correction control signal (V _C1 ) of the television.