KR920006057Y1 - White balance circuit - Google Patents

Abstract

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Description

White balance operation part detection circuit

1 is a full auto white balance system.

2 is a circuit diagram of the present invention

* Explanation of symbols for main parts of the drawings

3,3 ': Gate 4,4': Level comparison detector

8: White balance driver detection circuit 9: Clamp

10: high brightness determination unit 11: white balance control voltage generator

OP1-OP7: Op amp Q1, Q2, Q3: Transistor

The present invention provides a full auto white balance system in which a white balance is adjusted by detecting only a specific portion inside an electric signal of a subject incident to a video camera, so as to effectively detect the detection of the specific portion. A white balance operation part detection circuit is provided.

In other words, when shooting a subject with a very bright subject (including high saturation components), this part is detected and the white balance is detected and removed to solve the color shift by detecting the white balance. It is a white balance operation unit detection circuit to enable effective white balance.

First, when shooting a subject using a white camera camera of a video camera, the R component (red component: long wavelength component in visible light) and B component (blue component: short wavelength component in visible light) are included depending on the light source conditions of the projectile. In order to prevent the screen shot from being red or blue, the ratio of red and blue signals is compared to adjust the gain of the red signal amplifier and the blue signal amplifier so that the ratio is always constant regardless of the light source. System to maintain the ratio.

The configuration of such a general white balance system is as shown in FIG. 1, which will be described below.

In other words, the light from the video camera through the lens is photoelectrically changed by the image pickup device to be converted into an electrical signal, and then separated into a Y signal (luminance signal), R signal (red signal), and B signal (blue signal) through signal processing. do.

The separated R and B signals are applied to the R-Y matrix 2 and the B-Y matrix 2 'to which the Y signal is applied through the respective color signal heavy amplifiers 1 and 1'. A color difference signal of B-Y is generated, which is balanced-modulated into a chroma signal, mixed with the Y signal, and made into a composite video signal.

In this process, the control of the white balance system is performed to balance the R signal and the B signal. In the television and video signals, the luminance signal is formed by Y = 0.3R + 0.59G + 0.11B and white in light. ) Uses the same ratio of RGB, which is the three primary colors of light, to achieve white balance using the characteristic that the color difference signal becomes R-Y = 0 and B-Y = 0 when photographing white.

That is, the R-Y and B-Y signals are applied to the level comparison detecting section 4 (4 ') to determine whether the levels of R-Y and B-Y are' 0 ', respectively (R-Y <0, B -Y <0 outputs high level and R-Y> 0, B-Y> 0 outputs low level.) Digital / Analog is controlled by controlling count operation of up / down counter (5) (5 '). The output voltage of the converter 6, 6 'is changed and applied to the red signal amplifier 1 and the blue signal amplifier 1' through the buffers 7 and 7 'to adjust the gain.

Thus, the white balance is adjusted to R-Y = 0 and B-Y = 0 by repeating the process of controlling the detection output of the gain level comparison detecting section 4 (4 ') of the color signal amplifier 1 (1'). .

At this time, when R-Y = 0 and B-Y = 0, R = B = G and R and B are in a balanced state.

Here, the Full Auto white balance system detects only a certain portion of the white balance driver detecting circuit 8 within the electrical signal of the subject incident on the video camera, and operates the gate 3 (3 ') to operate the system. The present invention relates to a system for switching, and the present invention relates to the configuration of the white balance driver detecting circuit 8 to more effectively detect such a specific part.

The present invention as described above is described in detail the configuration and the effect according to Figure 2 as follows.

-(R-Y) and-(B-Y) signals are applied to the white balance control voltage generator 11 after passing through the gates 3 and 3 'to control the gain of the red signal amplifier and the blue signal amplifier. A white balance adjustment circuit for generating a voltage to be used, comprising: a clamp portion 9 for clamping an input luminance signal Y to a clamp voltage supplied from an op amp OP1 in a transistor Q1 operated by a clamp pulse, When the level of the luminance signal clamped by the clamp unit 9 is higher than or equal to a predetermined level, the clamp unit 9 detects the output signal and outputs a gate 3 (3 ') blocking signal and simultaneously applies the clamp voltage applied to the transistor Q1 of the clamp unit 9. A high luminance discrimination unit 10 which raises a predetermined amount of light, and a luminance signal Y and a color difference signal (-(R-Y)) (-(B-Y)) are detected to detect a portion having high luminance and low saturation. 3) White balance driver detection time outputting an operation signal to (3 ') Will connect the configuration (8).

At this time, the clamp unit 9 causes the Y signal to be applied to the collector of the transistor Q1 through the capacitor C2, the clamp pulse is applied to the base thereof, and the clamp voltage (to the emitter of the transistor Q1). Is configured to apply the output of the operational amplifier OP1.

The clamped luminance signal is applied to the op amp OP2 and compared with the reference voltage by the resistors R6 and R7 and then applied to the white balance driver detecting circuit 8 and at the same time the inverting terminal of the op amp OP3. In the op amp OP3, the output of the op amp OP2 is compared with the set voltage set by the resistors R8 and R10, and the output of the op amp OP3 is applied to the transistor of the clamp unit 9. The high brightness determining unit 10 is configured to adjust the brightness clamp voltage without going to Q1.

The Y signal is applied to the non-inverting terminal (+) of each of the op amps OP4-OP7, and the-(R-Y) and-(B-Y) signals are synthesized and inverted by the transistor Q2, and then the transistor Q3. Is applied to the inverting terminal (-) of the operational amplifier OP6 and the non-inverting terminal (+) of the operational amplifier OP7 through?).

At this time, the-(B-Y) signal is applied to the inverting terminal (-) of the op amp (OP4) and the-(B-Y) signal is applied to the inverting terminal (-) of the op amp (OP5). The inverting terminal (-) of OP7 is configured to be applied to the reference voltage Vref by the resistors R23 and R24.

The op amps OP2 and OP4-OP7 are wired and open collector comparators.

The white balance driver detecting circuit 8 of the present invention configured as described above has a-(B-Y) and Y,-(R-Y) and Y, ((R in the open-amp type comparator op amp OP4-OP7, respectively. -Y) + (B-Y)) and Y, ((R-Y) + (B-Y) + Y) and Vref The circuit is configured to detect only the high brightness and low saturation parts, and applies a high level signal to the gates 3 and 3 'only when all four outputs of the op amps OP4-OP7 are high level. The-(R-Y) signal and the-(B-Y) signal are input to the control voltage generator 11 for white balance so as to sense only a specific portion inside the subject to operate the white balance.

At this time, the toristor Q2 of the white balance driver detecting circuit 8 inverts the-(R-Y) and-(B-Y) signals, and inverts the mixed and inverted signals of the transistor Q2. It is applied to the op amps OP6 and OP7 through the transistor Q3.

Y>-(B-Y) for the operational amplifier (OP4), Y>-(R-Y) for the operational amplifier (OP5), Y> (R-Y) + (B-Y) for the operational amplifier (OP6). The op amp OP7 outputs a high level when (R-Y) + (B-Y) + Y> Vref.

That is, the op amps OP4-OP7 determine the portions having the high brightness and the low saturation components as described above to make the switching signals of the gates 3 and 3 '.

However, if there is a part of the subject that is very bright and has a high saturation component, the above operation selects the high luminance part first, so if this part (a very bright part with high saturation component) is detected and the white balance is achieved based on this part, It is determined that this part (high brightness part) is white, and thus the gains of the red signal amplifier and the blue signal heavy amplifier are adjusted so that red or blue or other colors thereof are distorted.

In order to protect such a phenomenon, the clamp unit 9 and the high brightness discriminating unit 10 were configured.

That is, the op amp (OP1) is the clamp voltage ( ) Is an emitter power supply, which is used to remove noise and prevent oscillation.

The transistors Q1, capacitors C2, C3, and resistor R4 clamp the input Y signal to the clamper voltage of the transistor Q1 by the clamp pulse input to the base of the transistor Q1. .

In addition, the voltage applied to the non-inverting terminal (+) of the operational amplifier (OP2) ( When a higher level Y signal is applied to the inverting terminal (−) of the operational amplifier OP2, the output terminal output of the operational amplifier OP2 falls to the low level.

This means that when a very bright subject part is input, the output of the operational amplifier OP2 is dropped to a low level.

On the other hand, the output of the op amp (OP2) is an open collector type and is connected to the output terminal of the op amp (OP4-OP7) to form a wired AND, so that a very bright subject part is formed by the op amp (OP4-OP7). Although detected, the output of the operational amplifier OP2 is at the low level, so the control signal input to the gate 3 (3 ') is at the low level so that this part is not selected.

However, in this case, if the majority of the subject is a very bright part, most of the subject is not selected by the op amp (OP2), and the rest of the subject is a low brightness part and is not selected by the op amp (OP4-OP7). Since the white balance function cannot be performed at this time, the clamp voltage of the Y signal is increased by a predetermined amount to determine a component having a slightly lower luminance, and thus the white balance is performed by "on" the gate 3 (3 ').

That is, during normal operation, the output of the operational amplifier OP2 is at a high level, and current does not flow through the resistor R11. Since the output of the operational amplifier OP3 is at a low level, the output of the operational amplifier OP3 is at a low level, and an electric current can flow to the output terminal of the operational amplifier OP3. Therefore, the emitter voltage of the transistor Q1 is (OP1 output voltage × ) To be used as the clamp voltage of the Y signal.

However, when the output of the operational amplifier OP2 becomes low due to a very bright subject, the inverting terminal (−) input voltage of the operational amplifier OP3 is lower than the input voltage of the non-inverting terminal (+). Since the output goes high, the emitter voltage of transistor Q1 is (OP1 output voltage x ), The clamp voltage for the Y signal is increased, so that a signal component having a lower luminance signal is selected, thereby performing normal height balance operation.

As described above, the present invention detects and removes a very bright subject part to prevent color shifting by detecting a white balance when detecting a subject including a very bright subject (including a high saturation component) and white balance. By increasing the clamp voltage, the white balance is operated to prevent the white balance from malfunctioning even if a very bright part is included inside the subject.

Claims (3)

In the white balance adjustment circuit which controls the-(R-Y) and-(B-Y) signals applied to the white balance control voltage generator 11 at the gates 3 and 3 ', by a clamp pulse. The clamp unit 9 for clamping the input luminance signal Y in the operated transistor Q1 to the clamp voltage supplied from the op amp OP1 and the circuit signal level clamped in the clamp unit 9 have a predetermined level. If it is abnormal, it detects this and outputs the gate 3 (3 ') blocking signal and at the same time increases the clamp voltage applied to the transistor Q1 of the clamp unit 9 by a certain amount, and the luminance signal ( A white balance driver which detects a portion with high brightness and low saturation by comparing the color difference signal (-(R-Y)) (-(R-Y)) with Y and outputs an operation signal to the gates 3 and 3 '. Detection circuit of the white balance operation part, characterized in that the detection circuit 8 is connected 2. The high brightness determination unit 10 is provided with an op amp (OP2) for comparing the luminance signal input clamped by the clamp unit (9) with a voltage set by the resistors (R6) and R7. The output of OP2 is connected to the gate (3) (3 ') control signal and is provided with an op amp (OP3) for comparing the output of the op amp (OP2) and the voltage set by the resistor (R8) (R10) And the output of the op amp OP3 is connected to the emitter of the transistor Q1. 2. The white balance driver detection circuit (8) according to claim 1, wherein the white balance driver detection circuit (8) includes an op amp (OP4) (OP5) for comparing the Y signal with the-(B-Y) and-(R-Y) signals. And a transistor Q2 for synthesizing and inverting the Y and-(R-Y) signals, and having an op amp OP6 for comparing the Y signal and the synthesis inverted signal of the transistor Q2. And an op amp OP7 for comparing the synthesized inverted signal and the Y signal synthesized with the reference voltage Vref set by the resistors R23 and R24, and then outputting the op amps OP4-OP7. And the op amp (OP2) output of the high brightness determination unit 10 is wired and coupled so as to be applied as a control signal of the gate (3) (3 ').