JPH07255062A - Color video camera - Google Patents

Abstract

PURPOSE:To maintain a white balance state corresponding to color temperature at all times by an internal light measurement system. CONSTITUTION:Color difference signals B-Y and R-Y are integrated by integration circuits 3 and 4 to detect their mean value voltages VB-Y and VR-Y. Comparators 6 and 7 compares the mean value voltages VB-Y and VR-Y with a reference voltage Vref and generate a comparison detection signal of 'H' or 'L' according to their large/small relation. Up/down switching circuits 8 and 9 set up/down counters 10 and 11 to an up-counting mode or down-counting mode according to the comparison detection signal. The up/down counters 10 and 11 counts clock pulses pu from a clock pulse generator 24 in the set mode and their counted values are converted by D/A converters 12 and 13 into analog control voltages. By those control voltages, a variable gain circuit for chrominance signal is gaincontrolled.

Description

Detailed Description of the Invention [0001] BACKGROUND OF THE INVENTION The present invention relates to a color video camera.
In particular, the present invention relates to the white balance device. [0002] 2. Description of the Related Art In a color video camera, the subject
In order to prevent deterioration of color reproducibility due to the color temperature of
It balance device is provided. This white rose
The sensing device detects the color temperature of the subject and measures the color temperature
To ensure that the white subject is reproduced correctly in white.
Amplitude of red (R) and blue (B) signals obtained from the image element
The color temperature of the subject is detected by
Different types of white balance devices have already been proposed
It One of them is a method called an external light metering method.
, Which is disclosed in, for example, Japanese Patent Laid-Open No. 58-578.
As disclosed in Japanese Patent Publication No. 85 (hereinafter, referred to as known example 1
Equipped with a color temperature detection circuit using an external light metering sensor
The color signal in response to the control signal obtained from the output signal.
Use of the red (R) and blue (B) signal circuits of the Deo camera
It is to adjust the profit. This method is continuous during shooting
The color temperature of the illuminating light that changes to
Since the lance can be automatically adjusted, the video camera
Makes it extremely easy to operate. The other one has a different principle from this.
So, for example, "National Technical Report" Vo
L.28, No.2 (Apr.1982) pp.151-155
By Shoji Nishikawa of "Video camera automatic white rose
"System" (hereinafter, known example 2)
And Hitachi consumer IC data book Sho 59.2, pp. 1
25-128 "HA11777MP" (hereinafter, known example 3
That is) disclosed. These adopt a system called internal light metering system.
Which was used in a color video camera,
If the color difference signal is zero when shooting a white subject,
Based on being in a well-balanced state
It is a spider. Therefore, this method shoots a white subject
Then, the color difference signal at this time is detected, and based on this detection signal
R signal of the color video camera by the control signal obtained in
The color difference signal is automatically controlled by controlling the gain of the signal circuit and B signal circuit.
Form a negative feedback loop so that the signal becomes zero, and in a pure circuit
It is composed. According to this method, as in the known example 1, the external light is measured.
No need to illuminate, as shown in known examples 2 and 3
Can be realized with one dedicated IC and some peripheral parts
It is a small and inexpensive system, and
Since a feedback loop is formed in the
The white balance is adjusted. [0007] By the way, the above-mentioned known examples
The technique described in No. 1 uses an illumination light that changes continuously during shooting.
Automatically adjusts the white balance at all times by following the color temperature.
It is possible to use the above external light metering sensor.
For low dynamic range and high illuminance due to the limited dynamic range
That the white balance cannot be adjusted accurately in the area
The problem, the shooting range seen by the lens and the range seen by the sensor
There is a problem that there are shooting situations with different color temperatures.
It was In addition, an automatic white rose including an external light metering sensor
Device, cost reduction and miniaturization of color video camera
Is hindering The method disclosed in the above-mentioned publicly known examples 2 and 3
In, the IC is a control voltage generator of the gain control circuit.
Up and down with the functions of a memory circuit
Digital signal processing is performed using a counter
However, there is a feature. That is, it is described in the known example 2.
First, image the white subject and move the negative feedback loop.
When you make it, white balance is automatically achieved
(Color difference signal becomes zero level), and then the negative feedback loop
By turning it off, the white balance is maintained.
You can hold and take an image. However, from this point of view,
Outside or various ambient light such as early morning, evening twilight, clear sky, cloudy sky
Depending on the state of the
And, although it is mechanical, when you set the white balance
The above-mentioned preparatory operation is required, and like the device of the known example 1,
Following the color temperature of the illumination light that changes continuously during imaging,
You can always say that the white balance is automatically adjusted.
However, it hinders the operability of the color video camera. The object of the present invention is to solve the above problems,
Internal light metering keeps the haze constant without disturbing operability.
White roses that can maintain balance
To provide a color video camera equipped with
is there. [0011] [Means for Solving the Problems] To achieve the above object
According to the present invention, the first and second primary colors obtained from the image sensor are
Of the first and second variable gain circuits which respectively control the gain of the signal
A color temperature signal is generated from the output signal, and the color temperature
The color difference signal is used as the signal and
Is the average value obtained by integrating every multiple field period
Color temperature detection that constantly detects color temperature information by comparing with a reference value
Output means and the first and the first based on the detected color temperature information.
Controlled by control means for controlling the gain of the second variable gain circuit
Form a loop and let the control loop follow the change in color temperature
If you move it tightly, it will change continuously during shooting.
Automatically adjusts the white balance by following the color temperature of the light source
adjust. [0012] [Function] When the white balance is maintained, the subject
Not only when it's white, but when it's not white,
For most subjects, even one field period
Is the average (integral) value of the color difference signal in multiple field periods
Has been found to be at or near zero.
The present invention has been made by paying attention to this point.
Signals every 1 field period or multiple field periods
The control voltage is obtained based on the integrated voltage obtained by integrating
Control voltage to control the gain of R signal circuit and B signal circuit.
The chromaticity of the illumination light and the subject that change continuously during imaging
Follow the pattern contents of so that the integrated voltage becomes zero.
It is a thing. Even with this control, the color temperature of the illumination light
The white balance state is left depending on the subject and the picture content of the subject.
It was confirmed that it was not so affected and did not cause any problems in practical use.
It was [0013] Embodiments of the present invention will now be described with reference to the drawings.
It FIG. 1 shows an embodiment of a color video camera according to the present invention.
2 is an input terminal, and 3 and 4 are block diagrams showing
Integrator circuit, 5 is an input terminal, 6 and 7 are comparators, 8 and
9 is an up / down switching circuit, 10 and 11 are up / down
Counters 12 and 13 are digital / analog (D / A)
Converters, 14 and 15 are output terminals, 16 is a reset circuit,
17 and 18 are input terminals, 19 is start / stop control
Circuits, 20 and 21 are convergence detection circuits, 22 is AND gate
23, stop control circuit, 24 clock pulse generation
Living device, 25 is a start delay circuit, 26 to 29 are input terminals
Is. In a color video camera, the
The obtained color signals B and R are processed by the variable gain circuit,
The low-frequency component of the generated luminance signal (hereinafter referred to as the luminance signal
Y)) and the color difference signals BY and RY are subtracted.
It is formed. These color difference signals BY and RY are
In order to form the control signals for balancing,
It is clamped at a quasi level and the sampling pulse of a predetermined cycle
Sampled by Obtained by processing in this way
The obtained color difference signal BY is applied to the input terminal 1 in FIG.
The color difference signal RY is also supplied to the input terminal 2.
Be done. The color difference signal BY has a time constant of 1 field.
Integrate with the integration circuit 3 that is set during the integral multiple period
The integrated voltage V of the color difference signal BY_BYTo form. color
The difference signal RY is also integrated by the same integrating circuit 4 to obtain an integrated voltage.
V_RYIs formed. Integrated voltage V_BYTo the comparator 6
The reference voltage V supplied from the input terminal 5_refCompared to
It Comparator 6 is V_BY≧ V_ref"L" when
(Low level), V_BY<V_ref"H" (high level
Output circuit that generates an output voltage
Supply to 8. Similarly, the integrated voltage is
V_RYAnd reference voltage V_refIs compared with V_RY≧ V_ref of
Sometimes "L", V_RY<V_refOutput that becomes "H" when
A voltage is formed and supplied to the up / down switching circuit 9.
It The up / down switching circuits 8 and 9 are star
Clock pulse generator 24 of start / stop control circuit 19
Is supplied from 1 field or the cycle of integral multiple
For each clock pulse φ
The level of pressure is judged, and 5-6 depending on the judgment result.
Bit up / down counters 10 and 11 are counted up.
Set to count mode or down count mode.
These up / down counters 10 and 11 are set
Up-counts the clock pulse φ according to the mode
To count down. Counting up / down counters 10 and 11
Values are converted into analog signals by the D / A converters 12 and 13, respectively.
The gain control voltage from the output terminals 14 and 15
It is supplied to the above-mentioned variable gain circuit (not shown). In this way, negative feedback is made for each of the color signals B and R.
A control loop is configured, and a reference voltage V_ref
Is set appropriately, the integrated value V_BY, V_RYIs zero
The gain of the variable gain circuit is set so that it becomes almost zero.
Controlled. On the other hand, the start / stop control circuit 19
In addition, the level determination result of the up / down switching circuit 8
Is supplied to the convergence detection circuit 20, and also up / down
The level determination result of the switching circuit 9 is supplied to the convergence detection circuit 21.
To be done. These convergence detection circuits 20 and 21
The level is inverted every clock pulse φ, and the number of inversions is
When it continues for a preset number of times, "H" is detected
Output a signal. This means that the integrated value V_BY, V_RYIs zero
Or it means almost zero. The detection signals from the convergence detection circuits 20 and 21 are
Both are supplied to AND gate 22, but both are "H"
And the mode switching signal M from the input terminal 26
When "H", the output terminal of the AND gate 22 is
It becomes “H” (white balance converges in this state)
This causes the stop control circuit 23 to stop.
Generates a control signal and operates the clock pulse generator 24.
To stop. When the mode switching signal M is "L", the
Irrespective of the output levels of the bundle detection circuits 20 and 21,
The output level of the gate 22 is "L", and therefore the clock level is
The clock pulse generator 24 constantly generates the clock pulse φ.
It The mode switching signal M is always a white balun.
Adjustment or adjust the white balance when needed.
This is to select whether or not to adjust the lance.
In the case, it is set to "L", and in the latter case, it is set to "H". Now, set the mode switching signal M to "L".
In this case, as is clear from the above explanation,
The output level of the port 22 is always "L", and the clock
Since the loose generator 24 operates all the time, up / down
The exchange circuits 8 and 9 and the up / down counters 10 and 11 are always
It operates and the gain control voltage is always output from the output terminals 14 and 15.
I will be forced. Therefore, the color temperature of the subject and the contents of the pattern change.
However, following this, the white balance is automatically adjusted.
Is performed. A milky white that diffuses light as in the above-mentioned known example 3.
Do not adjust the white balance using the optical filter of
However, white balance can be achieved when necessary using a white subject.
The level of the mode switching signal M when adjusting
Set to "H". The convergence detection circuits 20 and 21 enable integration
Pressure V_BY, V_RYIs detected to be zero or nearly zero.
Then, the output level of the AND gate 22 becomes "H".
The clock pulse generator 24 stops operating. this
The up / down counters 10 and 11 are
Holds the counter values and keeps them constant according to these count values
Variable gain of the color signals B and R by the level gain control voltage
The gain of the circuit is kept constant. As described above, a milky white optical filter is used.
The white balance switch (not shown)
Start the white balance adjustment, but at this time,
When this optical filter is inserted in the optical path of the optical system,
At the same time, the mode switching signal M becomes "H". Also, why
Input the pulse generated by operating the balance switch
It is supplied from the terminal 29 to the start delay circuit 25.
The start control signal is delayed by about 0.25 seconds.
Supplied to the generator 24. This allows the clock pulse
The pulse generator 24 starts generating the clock pulse φ. The start delay circuit 25 has a milky white color.
At the moment the optical filter is inserted in the optical path of the optical system
This is to prevent the influence of mechanical vibration. In this way, the white balance switch
By operating, similar to the above-mentioned known example 3, milky white light
It is also possible to adjust the white balance using an optical filter.
It From the input terminal 27 to the clock pulse generator 2
4 is applied with a drive voltage, and the input terminal 28 is
As described later, a voltage is applied and a clock pulse is generated.
The device 24 is forcibly stopped. The reset circuit 16 is a color video
The mode is turned off when the camera is turned on or the mode switching signal M
Prevents abnormal image quality such as hue change of the reproduced image during conversion
Backup to the input terminal 17
A reset pulse is input from the input terminal 18 as the voltage is applied.
Mode switching signal M supplied from the input terminal 26
Detects the level inversion of. With this reset circuit 16,
The gain control voltage obtained at the output terminals 14 and 15 is intermediate
The up / down counters 10 and 11 are reset so that they take a value.
Set. As described above, according to this embodiment,
For example, there is a constant automatic white balance adjustment system.
Or a white subject is imaged, the negative feedback loop is activated, and
Dynamically balance the white balance, then
Select one of the two systems to hold
White roses that are inexpensive and highly versatile, such as can be used in combination
Can be realized. However, in this embodiment, as described above,
On the other hand, when a picture such as one color of red or one color of blue is picked up,
When the weight balance operation is performed, such a pattern is
There is a problem that the balance of the balance is greatly lost. This problem will be described below. Color television cameras are generally 3
Accurate color of an object illuminated at a color temperature of 200 ° K
Basically adjusted to be reproduced. That is, the color temperature
A white subject should be reproduced white at 3200 ° K (immediately
Then, so that the color difference signal becomes zero), the level of the color signals B and R is
Adjust the The levels of the color signals B and R at this time are shown in FIG.
As shown in (a), when it is set to 0 dB, the color temperature changes.
No white level rose as shown in the figure.
I'm crushed. Generally, the color temperature is approximately 2000 ° K to 10
It is necessary to consider 000 ° K. Therefore, as shown in FIG.
As shown in, the maximum gain control is ± 7 to ± 9 dB or more.
Adjustable white gain adjustment by installing a variable gain circuit
The possible range is taken according to a wide range of color temperature changes. Therefore, in FIG. 1, D / A conversion is performed.
The output voltage of the output devices 12 and 13 directly to the control voltage of the variable gain circuit
As shown in FIG. 3, the D / A converter cannot
The output voltage of 12 and 13 is converted by the voltage conversion circuit 30,
Use of the variable gain circuits 31 and 32 for the signals B and R as described above.
The control voltage is obtained. FIG. 4 shows the D / A converter 1 in FIG.
2 and the specific circuit configuration of the voltage conversion circuit 30.
is there. On the other hand, the amount of carrier (carrier color signal) leakage
Depending on the degree of
This amount of leakage is in a white-balanced state.
Are very few. Usually 60-80 mV
_PPIf the following, the reproduced image for a white subject is white.
It is felt as a color. Now, an NTSC color video camera
At a white object at 3200 ° K
Balance and then adjust the white balance.
Measures the amount of carrier leakage for each color temperature when there is no light
Then, it becomes as shown by the solid line D in FIG. to this
On the other hand, the solid line A indicates the mode switching signal in the above embodiment.
Set M to "L" to set the automatic white balance adjustment mode.
It shows the amount of carrier leakage when the
Good white balance for various color temperatures
I understand. By the way, in the above embodiment, the description will be given first.
As described above, the variable gain circuit for the color signals B and R has a wide range.
Gain control is possible across the subject, so the subject is a special picture
In the case of the pattern content, for example, a single color of red, the integrating circuit 4
Integrated voltage V obtained from (FIG. 1)_RYIs very different from zero
In reality, the white balance is
However, this integrated voltage V_RY Output terminal so that
A gain control voltage occurs at 15 (FIG. 1). As a result,
The balance of the balance is lost. The solid line A in FIG. 5 (b) is red with a constant color temperature.
The subject of one color is targeted for imaging, and the automatic white
When performing balance adjustment,
Shows the amount of carrier leakage according to the difference in the area ratio of the object
And the proportion of the area of this red subject is large
How much transport should be obtained when white balance is achieved
The amount of attenuation with respect to the color signal level (0 dB) increases.
I understand. This means that the saturation of the red part of the playback screen is
It means that it decreases greatly with the shadow area. According to the experiment, the drawback of such image quality deterioration is
For example, as shown by broken line B or broken line C in FIG.
Attenuation of carrier color signal level that increases with product expansion
Is reduced by about 4 to 6 dB, and the visual image is improved.
It was found that the quality improvement effect was extremely large. in this case,
If a white subject is photographed, the broken lines B and C in FIG.
Characteristics, and the accuracy of white balance is slightly reduced.
However, it can be supplied practically and is automated without any inconvenience.
Can be realized. The characteristics shown by the broken lines B and C in FIG.
The negative feedback control loop that limits the gain control range.
Can be achieved by reducing the loop gain of
Wear. FIG. 6 shows the color according to the present invention in view of the above point.
FIG. 13 is a block diagram of a main part showing another embodiment of a video camera.
35 is a voltage conversion circuit, which corresponds to FIG. 1 and FIG.
The same reference numerals are given to the parts to be omitted and duplicate explanations are omitted.
It In this embodiment, in addition to the voltage conversion circuit 30,
A voltage conversion circuit 35 is provided and the combined conversion characteristics of these are used.
For example, as shown in FIG. 2B, the output terminals 33,
The range of the gain control voltage obtained in 34 is limited to the α region.
It is a thing. In the case of limitation as shown in this figure, the variable profit
The gain controllable range of the acquisition circuits 31 and 32 (FIG. 3) is ±
It is about 4.5 dB.
That the counters 10 and 11 overflowed
And the gain control range of the variable gain circuits 31 and 32 is limited.
To be done. According to this embodiment, as shown in FIGS.
In addition, the operating characteristics shown by the broken line B are obtained. The voltage conversion circuit 35 is as shown in the figure.
And a resistor R connected in series between the power supply terminal and the ground terminal.
10, R11 and resistors R12, R which are also connected in series
13 and the connection point of resistors R10 and R11
The connection point of the resistors R12 and R13 is connected to the output terminal 15 of the child 14.
It has a simple configuration of connecting to each. Of course
However, instead of providing the voltage conversion circuits 30 and 35 separately,
One voltage conversion circuit having characteristics equal to their combined conversion characteristics
May be used. FIG. 7 shows a color video camera according to the present invention.
It is a principal part block diagram which shows another Example, Comprising:
Reference numerals 6 and 37 are switches, and the parts corresponding to FIG.
A single reference numeral is given and duplicate description is omitted. In this embodiment, the switches 36 and 37 are interlocked.
It operates by turning on and off as needed.
The white balun by connecting and disconnecting the voltage conversion circuit 35.
This is to increase the degree of freedom in operating the operation. That is, the automatic white balance adjustment is always performed.
To do so, turn on the switches 36 and 37,
As in the embodiment shown in FIG. 6, gain control of a variable gain circuit
Limit the range. On the other hand, the accuracy of white balance is maximized
Switch 36, 37 to the off state
To capture an image of a white subject, and select the mode switching signal M (Fig.
By setting 1) to "H", the charge according to the change in color temperature can be
Try to secure a sufficient gain control amount. FIG. 8 shows a color video camera according to the present invention.
38 is a block diagram of a main part showing still another embodiment, in which 38 is
The waveform processing circuit 39 is an output terminal, and corresponds to FIG.
The parts are given the same reference numerals. The embodiment shown in FIG. 6 and FIG.
D / A converter 1 for automatic adjustment of balance
By limiting the output voltage of 2 and 13,
Although the gain control range of the paths 31 and 32 (Fig. 3) is limited,
In this embodiment shown in FIG. 8, the color difference signal B− from the input terminal 1 is
The amplitude of Y is centered on the clamp potential in the waveform processing circuit 38.
Voltage range V_thYou can get the same effect by limiting it to
It is a scam. The same applies to the color difference signal RY.
This reduces the loop gain of the negative feedback loop.
As shown in FIG.
The characteristic indicated by the broken line C in (b) is obtained. The waveform processing circuit 38 shifts the color difference signals.
It could be something like a gradual compression of the width,
When capturing the subject and setting the white balance
Needless to say, will be inactive. FIG. 9 shows a color video camera according to the present invention.
4 is a block diagram showing a main part of still another embodiment,
0 is a voltage range detection circuit, 41 is a reference voltage source, and 42 is a current
Sources 43 and 44 are comparators, corresponding to FIG.
The parts are given the same reference numerals. In FIG. 1, constant white balance
Is automatically digitally adjusted. For this,
Convergence state where the integrated voltage of the color difference signal is zero or almost zero
In this state, the AND gate 22 does not work.
Integration voltage and reference voltage V_refA comparator that compares with
The levels of the outputs of 6 and 7 are inverted every clock pulse φ.
As a result, the countdown of the up / down counters 10 and 11
Value also changes with each clock pulse φ and the gain control voltage changes.
And periodic color flicker occurs on the playback screen. This embodiment shown in FIG. 9 has such a problem.
It is to be resolved, and in the convergence state of white balance
Indicates that the average level of the color difference signal is the reference potential V of this color difference signal.
_ref(Clamp level, usually zero level)
The difference between the two is within the predetermined voltage range Δv.
, The white balance is determined to have converged and the
The lock pulse generator 24 is stopped. That is, in this embodiment, the reference voltage V_refof
Reference voltage source 41, resistors R14 and R15, current source 42, and
Voltage range detection circuit 40 including comparators 43 and 44
Are provided, and the resistors R14 and R15 and the current source 42 are provided.
Are connected in series in order and reference is made to the connection point of resistors R14 and R15.
Reference voltage V from voltage source 41_refBy applying
At the end p of the resistor R14, the voltage (V_ref+ Δv) to the resistance R
At the connection point q between 15 and the current source 42, the voltage (V_ref-Δv)
Respectively, and this voltage (V_refComparing + Δv)
Data input to the non-inverting input of_ref-Δv)
It is used as the inverted input of the comparator 44. Also, the integration circuit
The integrated voltage from 8 and the inverting input of comparator 43
It becomes the non-inverting input of the comparator 44, which causes (V
_ref−Δv) ≦ integral voltage ≦ (V_ref+ Δv), the terminal
A voltage of "H" is generated at 28. This voltage is the clock of FIG.
It is supplied to the pulse generator 24. When this voltage is "H"
The clock pulse generator 24 is inactive.
As a result, the power of the up / down counters 10 and 11 is
Unt value is kept as it is, white balance is converged
In the state, the gain control voltage is kept constant. Integral voltage is
V_ref When the voltage is out of the range of ± Δv, the voltage of the terminal 28 becomes
It becomes “L” and the clock pulse generator 24 starts to operate.
White balance is automatically adjusted. The same applies to the color difference signal R-Y.
Needless to say. FIG. 10 shows a color video camera according to the present invention.
FIG. 4 is a block diagram of a main part showing still another embodiment of FIG.
5 is a low illuminance detection circuit, 46 is a reference voltage source, and 47 is a comparator.
1 and 48 are input terminals.
Are given the same symbols. In the embodiment shown in FIG. 1, extremely low illuminance
In the range, and therefore under poor S / N, noise causes
Comparator that compares the integrated voltage of the difference signal with the reference voltage
6 and 7 cause wrong judgment and abnormal white balance
Hold on. After that, set the illuminance to a level that will not cause misjudgment.
When the imaging situation changes continuously, in the process,
An abnormal color change may occur in the captured image. This embodiment, shown in FIG. 10, improves upon this.
Therefore, the low illuminance detection circuit 45 is installed. That is, a predetermined set voltage V of the reference voltage source 46
_SAnd the brightness signal input to the input terminal 48 to the comparator 4
The levels are compared in step 7 and the luminance signal becomes a predetermined voltage (low illuminance).
It is detected that the set voltage V_SMore brightness
When the signal level becomes low, the output of this comparator 47 becomes
It becomes "H", and this output voltage is input to the terminal 28 shown in FIG.
Force to stop the clock pulse generator 24,
To maintain the white balance situation in the image situation
To improve the abnormal phenomenon in the transient time.
It [0061] As described above, according to the present invention,
Uses color signals obtained from the image sensor to constantly separate white
The white balance can be adjusted automatically.
The operation for adjusting the lance can be simplified and the color temperature can be detected.
A dedicated means such as a sensor for
You can achieve simplification, cost reduction, and
You can also take a picture and adjust the white balance with high accuracy.
You can

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a block diagram showing an embodiment of a color video camera according to the present invention. FIG. 2 is a diagram showing a white balance shift characteristic with respect to color temperature and a characteristic of a color signal variable gain circuit. 3 is a block diagram showing a means for generating a gain control voltage in the embodiment shown in FIG. 4 is a circuit diagram showing a specific example of an analog / digital converter and a voltage conversion circuit in FIG. FIG. 5 is a characteristic diagram of white balance adjustment according to the present invention. FIG. 6 is a block diagram of main parts showing another embodiment of the color video camera according to the present invention. FIG. 7 is a principal block diagram showing still another embodiment of the color video camera according to the present invention. FIG. 8 is a principal block diagram showing still another embodiment of the color video camera according to the present invention. FIG. 9 is a principal block diagram showing still another embodiment of the color video camera according to the present invention. FIG. 10 is a principal block diagram showing still another embodiment of the color video camera according to the present invention. [Explanation of Codes] 3,4 Integration circuit 6,7 Comparator 8,9 Up / 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 Start delay circuit 26 Mode switching signal input terminals 30, 35 Voltage conversion circuit 36, 37 Switch 38 Waveform processing circuit 40 Voltage range detection circuit 45 Low illuminance detection circuit 48 Luminance signal input Terminal

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Michio Masuda             292 Yoshida-cho, Totsuka-ku, Yokohama-shi, Kanagawa             Ceremony Company Home Appliance Research Laboratory, Hitachi, Ltd.

Claims (1)

[Claims] 1. It has first and second variable gain circuits for respectively controlling the gains of the first and second primary color signals obtained from the image sensor, and outputs the color temperature signal from the output signals of the first and second variable gain circuits. In the color video camera configured to generate, color temperature detecting means for constantly detecting color temperature information by an average value of the color temperature signal for each constant period, and the first and first color temperature information detecting means based on the detected color temperature information. By providing a control loop consisting of the control means for controlling the gain of the variable gain circuit No. 2 and operating the control loop so as to follow the change in the color temperature, the color temperature of the light source continuously changing during photographing. The color temperature detection means integrates the color difference signals obtained by calculating the luminance signal and the primary color signals of the red signal and the blue signal respectively for each one field period or every plural field periods. hand The color temperature information is detected by comparing the average value and a predetermined reference value with a comparison and amplification circuit, and the control means controls the detection signal to control the gain of the first and second variable gain circuits. A color video camera, which is a control signal generation circuit for converting into a control signal of. 2. The first aspect of the invention is that the comparison amplifier circuit generates a binary signal according to a level relationship of an input signal, and the control signal generation circuit responds to the binary signal in an up-count mode. Or an up / down counter set to down count mode,
A clock pulse generation circuit that supplies a clock pulse that is continuously generated at all times to the up / down counter as a count clock pulse, and a voltage conversion circuit that converts the count value of the up / down counter into a DC control voltage in a desired range. The color video camera is characterized in that the control loop is continuously closed to operate during shooting. 3. The first aspect of the invention is that the comparison amplifier circuit generates a binary signal according to a level relationship of an input signal, and the control signal generation circuit responds to the binary signal in an up-count mode. Or an up / down counter set to down count mode,
A clock pulse generation circuit that supplies the generated clock pulse as a count clock pulse to the up / down counter, a start / stop control circuit that controls the supply of the count clock pulse to the up / down counter, and a count of the up / down counter. A color video camera comprising a voltage conversion circuit for converting a value into a DC control voltage in a desired range. 4. The voltage conversion circuit according to claim 2 or 3, wherein the voltage conversion circuit converts a count value of the up / down counter into an analog voltage, and an amplitude setting range of the amplitude of the analog voltage. A color video camera comprising a range setting means. 5. In Claim 2 or 3, the color temperature detecting means has a detecting means for detecting an integrated value of the color difference signal, and the detected integrated value is within a predetermined range. , The control loop is opened by stopping the supply of the count clock pulse to the up / down counter, and when the detected integral value is out of the predetermined range, the up / down counter is caused to count. A color video camera, characterized in that a clock pulse is reapplied to re-close the control loop. 6. A convergence state detection circuit for detecting a white balance convergence state by determining the number of consecutive up / down inversions of the up / down counter according to claim 2 or 3, and first and second operations. A function mode switching means for generating a function mode switching signal for mode switching, a logic gate circuit to which the function mode switching signal and the detection output signal of the convergence state detection circuit are supplied, and the detection output signal is A start / stop circuit for stopping the generation of the clock pulse from the clock pulse generation circuit when supplied through the logic gate circuit, and in the first operation mode, By constantly generating the clock pulse, the control loop is always closed to perform white balance adjustment. In the operation mode, the start with the detection of the convergence of the white balance due to the convergence state detection circuit, which is the detection output signal is supplied through the logic gate circuit /
A color video camera characterized in that the stop circuit stops the generation of the clock pulse from the clock pulse generation circuit, and the up / down counter holds the white balance state immediately before the stop. 7. In Claim 2 or Claim 3, The said voltage conversion circuit produces | generates the control voltage limited to the control amount which is not less than the controllable maximum gain control amount of the said variable gain circuit, It is characterized by the above-mentioned. A color video camera. 8. The claim 6 WHEREIN: The said voltage conversion circuit generate | occur | produces the control voltage limited to the control amount smaller than the controllable maximum gain control amount of the said variable gain circuit at the time of the said 1st operation mode, A color video camera, wherein a control voltage within a controllable maximum gain control amount of the variable gain circuit is generated in the second operation mode. 9. The color video camera according to claim 1, further comprising a waveform processing circuit that limits the amplitude of the color temperature signal in order to limit the control amount of the control loop.