JPS61199390A - White balance device - Google Patents

Abstract

PURPOSE:To continuously maintain the white balance by constituting the titled device so that the control voltage is obtained based on the integrated voltage obtained by integrating each field of a chrominance component difference signal, by which the gain is controlled, so that the said voltage is maintained zero as pursuing the chromaticity of the illuminant lights and the contents of pattern of the object that continuously change during the image picking-up. CONSTITUTION:The chrominance signals B and R obtained from an image pickup element is processed by a variable-gain circuit, and thereafter subtract- processed with the low-frequency component of the generated brightness signal, and chrominance component difference signals B-Y, R-Y are formed. The said signals are integrated by integrating circuits 3 and 4, and the integrated voltages are compared with the reference voltage by comparators 6 and 7, and supplied to up/down switching circuits 8 and 9. When a mode-switching signal M is set 'L', the up-counters 10 and 11 of the up/down switching circuits 8 and 9 at all time operate, from whose output terminals 14 and 15, the gain- control voltage is outputted. Accordingly, even if the color temperature and the contents of pattern of the object varies, the white balance is automatically adjusted by pursuing the said variation.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Application of the Invention] The present invention relates to a white balance device suitable for use in a color video camera.

[Background of the invention]

A color video camera is provided with a white balance device to prevent deterioration of color reproducibility due to the color temperature of a subject. This white balance device detects the color temperature of the subject and adjusts the amplitude of the red (几) signal and blue (B) signal obtained from the sensor so that the white subject is reproduced as white correctly for this color temperature. However, different types of white balance devices have been proposed that have different means for detecting the color temperature of the subject.

One of them utilizes a method called an external light metering method, and as disclosed in Japanese Patent Application Laid-open No. 58-57885 (hereinafter referred to as known example 1),
The color temperature detection circuit is provided with a color temperature detection circuit using an external light photometry sensor, and the gains of the red (R) and blue (B) signal circuits of the color video camera are adjusted in response to a control signal obtained from the output signal of the color temperature detection circuit. This method makes it possible to automatically adjust the white balance at all times by following the color temperature of the illumination light that changes continuously during shooting, making it extremely easy to operate the video camera. Due to the finite dynamic range of the sensor, there are problems in which it is not possible to accurately adjust white balance in low-light and high-light regions, and there are shooting situations where the color temperature of the shooting range where the lens fits and the range that the sensor sees differs. There was a problem. Furthermore, automatic white balance devices that include external light metering sensors are an impediment to lower cost and smaller size of color video cameras.

The other one is based on a different principle, for example, National Technical Re.
port"v'ol, 28 No. 2 (Apr.
1982) pp. 151-155 “Automatic white balance system for video cameras” by Akiharu Nishikawa et al.
(hereinafter referred to as Publicly Known Example 2) and Hitachi Civil Use I
C Data Book 1982, 2 pp, 125-1281
-HA 11777MPj (hereinafter referred to as known example 3)
It is disclosed in the following. These systems employ a method called internal light metering, and in color video cameras, when a white subject is photographed, if the color difference signal is zero, it means that the white balance is correct. It is based on Therefore, this method photographs a white subject, detects the color difference signal at this time, and
Controlling the gains of the R9 and B signal circuits of the color video camera with a control signal obtained based on the detection signal,
A negative feedback loop is formed to automatically reduce the color difference signal to zero.
Moreover, it is constructed in a pure circuit manner. This method does not require photometry of external light as in Known Example 1, and does not require photometry of external light as in Known Example 2. As shown in Known Example 3, it can be realized with one dedicated IC and some peripheral parts, so it is a small and inexpensive system, and as mentioned above, it forms a feedback loop, so it can accurately whiten. Balance is adjusted. In such a system, the IC has a gain control circuit control l11.
It is characterized by digital signal processing using an up-down counter that functions as a starting pottery and as a memory circuit. That is, as described in Publication Example 2, when a white subject is first imaged and the negative feedback loop is activated, the white balance is automatically established (the color difference signal is at zero level), and then, By cutting off the negative feedback loop, it is possible to maintain a well-balanced white balance when photographing. This means that
Indoors, outdoors or early in the morning.

According to various ambient light conditions such as dusk, clear skies, and cloudy skies, the photographer must perform preparatory operations such as photographing a white subject and setting the white balance, albeit mechanically, before taking an image. Unlike the device described above, it is not possible to automatically adjust the white balance at all times by following the color temperature of the illumination light that changes continuously during imaging, which hinders the operability of color video cameras.

[Purpose of the invention]

SUMMARY OF THE INVENTION An object of the present invention is to provide a white balance device that eliminates the problems of the prior art described above and that can constantly maintain a white balance state by internal light metering without interfering with operability.

[Summary of the invention]

When the white balance is correct, not only when the subject is white, but even when the subject is not white, for most subjects, the integral (average) of the color difference signal over one field period is used. It was found that the value is zero or close to zero. The present invention has been made with this point in mind, and a control voltage is obtained based on the integrated voltage obtained by integrating the color difference signal for each field, and this control giJ voltage is used to control the R signal circuit. The gain of the B signal circuit is controlled so that the integrated voltage becomes zero in accordance with the chromaticity of illumination light and the picture content of the subject, which continuously change during imaging.

Even with this control, the white balance condition is not affected as much by the color temperature of the illumination light or the image content of the subject.
It was confirmed that this does not pose a problem in practice.

However, if the subject has a special pattern, such as the entire surface of the image being photographed in red or blue, the integrated voltage of the color difference signal may deviate sharply from zero even if the white balance is correct. Therefore, if this integrated voltage is controlled to be zero, the white balance will shift significantly. In such a case, by controlling the gain control amount of the negative feedback gain control loop, the above-mentioned integral 'l1LEE is limited to a predetermined value, and the white balance operation is slowed down so that this integral voltage becomes zero. It should be controlled so that this does not occur.

[Embodiments of the invention]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a block diagram showing an embodiment of a white balance device according to the present invention, in which 1 and 2 are input terminals, 3.4
is an integration circuit, 5 is an input terminal, 6゜7 is a comparator, 8
, 9 is an up/down switching circuit, 10.11 is an up-down counter, 12.13 is a digital/analog (D/A
A) Converter, 14 and 15 are output terminals, 16 is a reset circuit, 17 and 18 are input terminals, and 19 is a start/stop control circuit.

20.21 is a convergence detection circuit, and 22 is an AND gate.

23 is a stop control circuit, 24 is a clock pulse generator, 25 is a start delay circuit, and 26 to 29 are input terminals.

In a color video camera, the color signals B and R obtained from the image sensor are processed by a variable gain circuit, and then subtracted from the low frequency component of the generated luminance signal (hereinafter referred to as luminance signal Y). Then, color difference signals B-Y and B-Y are formed. These color difference signals B-Y and R-Y are each clamped at a reference level and sampled by a sampling pulse of a predetermined period in order to form a control signal for white balance. The color difference signal B-Y obtained by processing in this manner is supplied to the input terminal 1 in FIG. 1, and the color difference signal B-Y is supplied to the input terminal 2 in FIG.

The color difference signal B-Y is integrated by an integrating circuit 3 whose time constant is set to a period of one field or an integral multiple thereof, to form an integral '1 voltage Vm-y of the color difference signal B-Y. The color difference signal -Y is also integrated by a similar integration circuit 4, and the integrated voltage VR-
Y is formed. The integral '[, [E Vl-T is supplied to the comparator 6, and the reference '1K Vre from the input terminal 5
compared with t. Comparator 6 is Vm-y≧Vr
When e f, it is "L" (low level) and Vm-y
(When Vref, an output voltage of 'H' (high level) is generated and supplied to the up/down switching circuit 8. Similarly, the comparator 7 selects the integrated voltage v3a and the reference voltage Vr e f. are compared, and an output voltage is formed which becomes 'L' when vtd≧Vref and becomes H' when Va-y (Vref) and is supplied to the up/down switching circuit 9.

The up/down switching circuits 8 and 9 change the level of the output voltage of the comparator 6゜7 for each clock pulse φ supplied from the clock pulse generator 24 of the start/stop control circuit 19 at a cycle of one field or an integral multiple thereof. The 5- to 6-bit up/down counters 10 and 11 are set to up-count mode or down-count mode based on the results of these determinations. These up/down counters 10.11 count up or down the clock pulse φ depending on the set mode.

The count values of the up/down counters 10.11 are respectively converted into analog signals by digital/analog converters 12.13, and supplied as gain control voltages from output terminals 14.15 to the above-mentioned variable gain circuit (not shown).

In this way, a negative feedback control loop is constructed for each color signal B, and by appropriately setting the reference voltage Vraf,
The gain of the variable gain circuit is controlled so that the integral value v, Vll-Y becomes zero or almost zero.

On the other hand, in the start/stop control circuit 19, the level determination result of the up/down switching circuit 8 is supplied to the convergence detection circuit 20, and the up/down switching circuit 90
The level determination result is supplied to the convergence detection circuit 21. These convergence detection circuits 20 and 21 output a detection signal of "H" when the level of the input signal is inverted every clock pulse φ and the number of inversions is set in advance and continues for nine predetermined times.

This means that the integral values Vm-v and Va-y have become zero or almost zero. Convergence detection circuit 20
The detection signal from ゜21 is supplied to the AND gate 22, but when both are R'' and the mode switching signal M from the input terminal 26 is H'', the output signal of the AND gate 22 is H''. (This state is said to be that the white balance has converged.) As a result, the stop control circuit 23
generates a stop control signal and clock pulse generator 2
Stop the operation of step 4.

When the mode switching signal M is “L”, the convergence detection circuit 20
．． Regardless of the output level of the AND gate 21, the output level of the AND gate 22 is L'', and therefore the clock pulse generator 24 always generates the clock pulse φ.

The mode switching signal M is used to select whether to adjust the white balance all the time or to adjust the white when necessary, and is set to "L" in the former case and "R" in the latter case. is set to

Now, if the mode switching signal M is set to "L",
As is clear from the previous explanation, the output level of the AND gate 22 is always "L", and the output level of the clock pulse generator 2
4 is always active, so up/down switching circuits 8 and 9
, up/down counter 10.degree. 11 also operates at all times, and a gain control voltage is always outputted from output terminals 14,15. Therefore, even if the color temperature or picture content of the subject changes, the white balance is automatically adjusted to follow this change.

As in the prior known example 3, when adjusting the white balance using a milky-white optical filter that diffuses light, or when adjusting the white balance when necessary using a white subject, the mode switching signal is used. Set the M level to "H". The convergence detection circuit 20゛21 integrates the voltage Vm-
When it is detected that r, V*-r are zero or nearly zero, the output level of the AND gate 22 becomes 'H' and the clock pulse generator 24 stops operating.This causes the up/down counter 10. 11 holds the immediately preceding counter value, and the gains of the color signal B and the general variable gain circuit are held constant by a constant level gain control voltage corresponding to these count values.

In this way, when using a milky white optical filter,
White balance adjustment is started by operating a white balance switch (not shown). At this time, this optical filter is inserted into the original path of the optical system and the mode switching signal M becomes H". A pulse generated by the operation of Generation of the clock pulse φ is started.The start delay circuit 25 is provided to prevent the influence of mechanical vibrations at the moment when the milky white optical filter is inserted into the optical path of the optical system.

In this manner, by operating the white balance switch, it is also possible to adjust the white balance using a milky white optical filter, as in the prior art example 3.

A driving voltage is applied to the clock pulse generator 24 from the input terminal 27, and a voltage is applied to the input terminal 28, as will be described later, to forcibly stop the clock pulse generator 24.

Further, the reset circuit 16 prevents abnormal image quality such as a change in hue of the reproduced image when the color video camera is powered on or when the mode is switched by the mode switching signal M, and the reset circuit 16 prevents abnormal image quality such as a change in hue of the reproduced image when the color video camera is turned on or when the mode is switched by the mode switching signal M. At the same time, a reset pulse is supplied from the input terminal 18, and a level inversion of the mode switching signal (2) from the input terminal 26 is detected.

This reset circuit 16 resets the up/down counter 10.11 so that the gain control voltage obtained at the output terminal 14.15 takes an intermediate value.

As explained above, according to this embodiment, the white balance is always automatically adjusted, or a white subject is photographed, the negative feedback loop is operated, the white balance is automatically maintained, and then the white balance is automatically adjusted. If it is possible to select one of the systems that maintains this, or to use both systems in combination, an inexpensive and highly versatile white balance system can be realized. However, as described above, this embodiment has a problem in that if the white balance is constantly operated when images of red, blue, etc. are photographed, the white balance of such images will be greatly distorted.

This problem will be explained below.

Normally, a color television camera is basically adjusted so that the colors of a photographed object are accurately reproduced at a color temperature of 32,006. i.e. color temperature, 3200'
, so that white subjects appear white (i.e.
Adjust the levels of the color signals B and R so that the color difference signal becomes zero. The levels of color signals B and R at this time are shown in Figure 2 (
As shown in a), if OdB is used, a level change as shown in the figure occurs as the color temperature changes, and the white balance is disrupted.

In general, it is necessary to consider the color temperature of approximately 2000° to 10000°K. Therefore, as shown in Fig. 2(b), a variable gain circuit that can sufficiently control the gain at a maximum of ±7 to ±9 dB or more is installed, and the white balance can be adjusted within a wide range of color temperature variations. ing. For this reason, in FIG. 1, the output voltages of the digital i-analog transformers 12 and 13 cannot be directly used as the output voltage of the variable gain circuit, and as shown in FIG. / Low EE output voltage of analog converter 12.13! The conversion circuit 30 converts the color signal B.

The gain control of the variable gain circuits 31 and 32 as described above can be achieved.

Note that FIG. 4 shows a specific circuit configuration of the digital/analog converter 12 and voltage conversion circuit 3o in FIG. 3.

On the other hand, the state of white balance breakdown differs depending on the degree of leakage of the carrier (carrier color signal), and this leakage amount is extremely small in the state after white balance is achieved. Normally, if it is less than 60 to 80 m Vp-p, a reproduced image of a white subject will be perceived as white.

Now, in an NTSC color video camera, if you take an image of a white subject, adjust the white balance at 3200 degrees, and then measure the amount of carrier leakage for each color temperature without adjusting the white balance, the fifth The result is as shown by the solid line in Figure (a). On the other hand, the solid line A indicates the amount of carrier leakage when the mode switching signal M is set to "L" and the automatic white balance adjustment mode is set in the above embodiment. It can be seen that it can be taken well.

By the way, in the above embodiment, as explained earlier,
Since the color signal B is capable of changing the gain side over a wide range with ordinary variable gain circuits, when the subject has a special picture content, for example, the color red, the integration circuit 4 (Fig. 1)
The integrated voltage Vn-y obtained from is significantly different from zero,
Even if white balance is actually achieved, the output terminal 15 is set so that this integral voltage VR-Y becomes zero.
A gain control voltage is generated (FIG. 1). As a result, the white balance condition is disrupted. The solid line A in FIG. 5(b) indicates that when a red-colored object with a constant color temperature is to be imaged and automatic white balance adjustment is performed in the above embodiment, the solid line A corresponds to the difference in the area of the red object relative to the entire imaged area. It can be seen that the larger the area ratio of this red object is, the greater the attenuation amount with respect to the carrier color signal level K (0 dB) that should be obtained when white balance is maintained. This means that the saturation of the red portion of the playback screen decreases significantly with the imaging area. The disadvantage of such image quality deterioration is that, according to experiments, the amount of attenuation of the carrier color signal level that increases as the area increases is approximately 4 to 6 dB@ It was found that the visual image quality improvement effect was extremely large. in this case,
If a white subject is photographed, the characteristics will be as shown by the broken lines B and C in FIG. 5(a), and although the accuracy of the white balance will be somewhat poor, it will be fully usable for practical use and automation can be realized without any inconvenience.

To achieve the characteristics shown in broken lines B and C in FIG. 5 above,
This can be achieved by limiting the gain control range, reducing the loop gain of the negative feedback control loop, etc.

FIG. 6 is a block diagram of main parts showing another embodiment of the white balance device according to the present invention in view of the above points,
Reference numeral 5 denotes a voltage conversion circuit, and parts corresponding to those in FIGS. 1 and 3 are denoted by the same reference numerals and redundant explanations will be omitted.

In this embodiment, a voltage conversion circuit 35 is provided in addition to the voltage conversion circuit 30, and due to their combined conversion characteristics, for example,
As shown in FIG. 2(b), the range of the gain control voltage obtained at the output terminals 33 and 34 is limited to the α region. When limited as shown in this figure, the variable gain circuit 31
．． 32 (Figure 3) gain controllable range is ±4.5dB
If it is more than this, it means that the up/down counter 10.degree. 11 has overflowed, and the gain control range of the variable gain circuits 31, 32 is limited.

According to this embodiment, the operating characteristics shown by broken lines B are obtained in the VCs shown in FIGS. 5(a) and 5(b), respectively.

Note that, as shown in the figure, the voltage conversion circuit 35 is connected in series between a power supply terminal and a ground terminal, and has a resistor 10. )t
ll and 13 with a resistance ratio of 12°, which are also connected in series, with a resistance ratio of 10. All connection point to output terminal 14
and connect the connection point of resistance ratio 12°R13 to output terminal 15.
It has a simple configuration that connects to. Of course, instead of providing separate voltage conversion circuits 30 and 35,
A voltage conversion circuit with a characteristic equal to these composite conversion characteristics may be used.

FIG. 7 is a block diagram of main parts showing still another embodiment of the white balance device according to the present invention, in which 36 and 37 are switches, and parts corresponding to those in FIG. 6 are given the same reference numerals. The explanation will be omitted.

In this embodiment, the switches 36 and 37 are operated in conjunction and turned on and off as necessary to connect and disconnect the voltage conversion circuit 35, increasing the degree of freedom in white balance operation. be. That is, if automatic white balance adjustment is to be performed at all times, the switches 36 and 37 are turned on to limit the gain control range of the variable gain circuit as in the embodiment shown in FIG. On the other hand, if you place extreme importance on the white balance, turn off the switch 36, 37't, take a picture of a white subject, and set the mode switching signal M (Fig. 1) to "H". By doing so, a sufficient amount of gain control can be achieved in response to changes in color temperature.

FIG. 8 is a block diagram showing still another embodiment of the white balance device according to the present invention, in which 38 is a waveform processing circuit, 39 is an output terminal, and parts corresponding to those in FIG. 1 are given the same reference numerals. It's boxed up.

In the embodiment shown in FIGS. 6 and 7, when performing automatic white balance adjustment at all times, the variable gain circuit 31.32 (third Although the gain control range of FIG. 8 is limited, in this embodiment shown in FIG. The same effect can be obtained by limiting the amount within the range vAh. Color difference signal (R
-Y), and as a result, the loop gain of the diagonal loose on the negative feedback side becomes smaller, and the characteristics shown by the broken line C in Fig. 5(a) and (b) are obtained for the amount of carrier leakage. It will be done.

Note that the waveform processing circuit 38 may be one that gradually compresses the amplitude of the color difference signal.
Needless to say, when the white balance is changed to Llf, the camera is in a non-operating state.

FIG. 9 is a block diagram showing still another embodiment of the white balance device according to the invention, in which 40 is a voltage range detection circuit, 41 is a reference voltage source, 42 is a current source, and 43
．． 44 is a comparator, and parts corresponding to those in FIG. 1 are given the same reference numerals.

In FIG. 1, constant automatic white balance adjustment is performed digitally. Therefore, in the convergence state where the integrated voltage of the color difference signal is zero or almost zero, the AND gate 22 does not operate, so the output of the comparator 6.7 that compares this integrated voltage with the reference voltage Vref is clocked. The level is inverted every pulse φ. As a result, the count value of the up/down counter 10.11 also changes every clock pulse φ, and the gain control voltage fluctuates, causing periodic color flicker on the reproduced screen.

This embodiment shown in FIG. 9 is intended to solve this problem. In the white balance convergence state, the average level of the color difference signal is set to the reference potential Vref (
This system focuses on the clamp level, which is extremely close to the zero level (usually zero level), and determines that the white balance has converged when the difference between the two is within a predetermined voltage range ΔV, and stops the clock pulse generator 24. It is.

That is, in FIG. 9, the reference voltage source 41 . Resistor 1-L14. R, 15, current source 4
A voltage range detection circuit 40 consisting of 2° voltage range converters 43 and 44 is provided, and resistors R14, R15 and a t-current source 42 are connected in series in order to detect a reference voltage from a reference voltage source 41 at the connection point of resistors R14° and R15. By applying Vref, a voltage (Vraf+
Δv), a voltage (Vref - ΔV) is generated at the connection point q between the resistance ratio 15 and the current source 42, and this voltage (Vre
f+ΔV) is the non-inverting input of the comparator 43, and the voltage (Jref-ΔV) is the inverting input of the comparator 44.The integral area king from the integrating circuit 8 is; It becomes a non-inverting input, thereby producing an "H" voltage at the terminal 28 when (Vref-ΔV)≦integrated voltage≦(Vref+ΔV).

This voltage is supplied from terminal 28 to clock pulse generator 24 of FIG. When this voltage is "H", the clock pulse generator 24 becomes inactive, so that the up/down counter 10°110 count value is maintained as it is, and in the white balance convergence state, the gain control 11I11! Keep the king constant. The integrated voltage is Vr
When the voltage is outside the range of ef±ΔV, the voltage at the terminal 28 becomes "L", the clock pulse generator 24 starts operating, and the white balance is automatically adjusted.

It goes without saying that the same applies to the color difference signal 1 (, -Y).

FIG. 10 is a block diagram showing still another embodiment of the white balance device according to the present invention, in which numeral 45 is a low illuminance detection circuit, and 46 is a reference voltage source.

47 is a comparator, 48 is an input terminal, and parts corresponding to those in FIG. 1 are given the same reference numerals.

In the embodiment shown in FIG. 1, in an extremely low illuminance region, that is, under a poor S/H condition, the comparator 6.7 that compares the integrated voltage of the color difference signal with the reference voltage causes an erroneous judgment due to noise. Maintain an abnormal white balance state.

Thereafter, when the imaging situation changes continuously to a level that does not cause erroneous judgments, an abnormal color change may occur in the captured image during this process. In this embodiment shown in FIG. 10, a low illuminance detection circuit 45 is installed to improve this problem. That is, the level of the predetermined set voltage V's of the reference voltage source 46 and the luminance signal input to the input terminal 48 is compared by the comparator 47, and it is detected that the luminance signal has reached a predetermined voltage (low illumination). When the luminance signal level becomes lower than the set voltage Vg, the output of this comparator 47 becomes "H", and this output voltage is applied to terminal 2 in FIG.
8, the clock pulse generator 24 is stopped, and the white balance situation in the immediately preceding white balance situation is maintained to eliminate the abnormal phenomenon during the above-mentioned transition.

〔Effect of the invention〕

As explained above, according to the present invention, automatic white balance is always maintained using color signals obtained from the camera sensor.
This simplifies the operation for white balance adjustment, eliminates the need for dedicated means such as a sensor to detect color temperature, and simplifies the configuration and reduces costs. Further, it is possible to image a white subject and perform highly accurate white balance adjustment, and it is possible to solve the problems of the prior art described above and provide a white balance device with excellent functions.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing an embodiment of a white balance device according to the present invention, FIG. 2(a) is a characteristic diagram showing white balance deviation with respect to color temperature, and FIG. 2(b) is a color signal variable gain circuit. 31\1 is a block diagram showing the gain control voltage generation means in the embodiment shown in Fig. 1, and Fig. 4 is a specific example of the analog/digital converter and voltage conversion circuit in Fig. 3. A circuit diagram showing the circuit diagram, Fig. 5(a)
), Φ) are characteristic diagrams of white balance adjustment according to the present invention, and FIGS. 6 to 10 are block diagrams of essential parts showing other embodiments of the white balance apparatus according to the present invention, respectively. 3.4... Integration times M, 6.7... Comparator. 8.9...Hot! Down switching circuit, 10.11
...Up-down counter, 12.13...
...Digital/analog converter, 19...
Start/stop control circuit, 20.21...
Convergence detection circuit, 22...And gate, 23.
... Stop control circuit, 24 ... Clock pulse generator, 25 ... Star) delay circuit,
26...Mode switching signal input terminal, 30°35
...Electronic EE conversion circuit, '36.37...
·switch. 38...Waveform processing circuit, 40...Voltage range detection circuit, 45...Low illuminance detection circuit, 48
...Brightness signal input terminal. Fig. 2 Gain side at pressure Fig. 3 Fig. 4 Fig. 5 (a) = (b) Red β plane ellipse Fig. 6 Fig. 7 Fig. 8 Fig. 9 Fig. O n Fig. 10 21-- ]-1”

Claims (8)

[Claims] (1) A variable gain circuit that processes a color signal, an arithmetic circuit that forms a color difference signal from the output color signal of the variable gain circuit, an integration circuit that smoothes the color difference signal, and an integrated voltage output from the integration circuit. and a reference voltage to generate a binary voltage according to the level relationship between the two voltages; A down counter, a start/stop control circuit that supplies count clock pulses of the up-down counter, a digital/analog converter that converts the count value of the up-down counter into an analog voltage, and an amplitude change range of the analog voltage. A white balance device comprising: amplitude range setting means for setting the amplitude range setting means, wherein the analog voltage whose amplitude change range is set by the amplitude range setting means is used as a gain control voltage of the variable gain circuit. (2) In claim (1), the start/stop control circuit determines a white balance convergence state based on the determination results of the clock pulse generator that generates the clock pulses and the up/down switching circuit. a convergence detection circuit for detecting, an AND gate inputting a mode switching signal and a detection output signal of the convergence detection circuit, and the detection output signal passed through the AND gate is supplied to stop the operation of the clock pulse generator. A stop control circuit is provided, and according to the mode switching signal, a first operation mode in which the clock pulse is constantly generated to perform white balance adjustment, and a second operation mode in which the generation of the clock pulse is stopped when the white balance converges. A white balance device characterized by being configured to be switchable. (3) In claim (1) or (2), the amplitude range setting means sets an amplitude change range of the analog voltage such that the gain of the variable gain circuit can be changed to a maximum extent. A white balance device characterized by being a voltage conversion circuit. (4) In claim (1) or (2), the amplitude range setting means sets the first amplitude of the analog voltage so as to change the gain of the variable gain circuit to the maximum extent possible. It is characterized by comprising a first means having a set variation range, and a second means for limiting the gain of the variable gain circuit to a predetermined range together with the first means at least in the first operation mode. White balance device. (5) In claim (4), the first,
A white balance device characterized in that the second means is a voltage conversion circuit that converts the analog voltage. (6) In claim (4), the first means is a voltage conversion circuit that converts the analog voltage, and the second means converts the amplitude of the color difference signal generated by the arithmetic circuit. A white balance device characterized by a limiting waveform processing circuit. (7) Claims (1) to (5) further include a voltage range detection circuit that detects the integrated voltage from the integrating circuit to determine whether or not the white balance has converged; 1. A white balance device characterized in that, in operation mode 1, the supply of clock pulses from the start/stop control circuit to the up-down counter is stopped during a period when the white balance is in a converged state. (8) Claims (1) to (7), further comprising a low illuminance detection circuit that detects a low illuminance period by detecting the level of a luminance signal, and in the first operation mode, A white balance device characterized in that the supply of clock pulses from the start/stop control circuit to the up-down counter is stopped during a period of low illuminance.