JPH06339149A - White balance adjusting device - Google Patents

Abstract

PURPOSE:To prevent white balance from being deviated toward a complementary color by evaluating a pattern so as to stop white balance adjustment by including not sufficiently many objects in a picked up pattern because of a narrow field angle or a short distance up to an object so as to stop white balance adjustment through the evaluation of the pattern when a color in the pattern is localized. CONSTITUTION:In the white balance adjustment in which a gain correction quantity is revised so as to approach an object to control the gain of R, B amplifier circuits 4, 5, when the gain correction quantity enters a predetermined range from an object value, the stop mode to inhibit the revision of a gain correction thereby fixing the gain is set and when an object value is changed by pattern evaluation in the stop mode and when the gain correction reaches at the outside of the range with respect to the object, the stop mode is released to execute white balance adjustment and when a field angle is narrow or an object distance is short, the prescribed range is increased to allow the stop mode to be hardly released.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an automatic white balance adjusting device for a color video camera which controls white balance based on a picked-up image signal obtained from an image pickup device.

[0002]

2. Description of the Related Art In a color video camera, it is necessary to control white balance in order to correct a difference in wavelength distribution of light depending on a light source.

This control is performed by adjusting the gain of each color signal so that the ratio of the three primary color signals of red (hereinafter R), blue (hereinafter B) and green (hereinafter G) is 1: 1: 1. Be seen.
Generally, for example, JP-A-62-35792 (H04
N9 / 73), the screen color difference signal RY,
A method of adjusting the gain so that the integrated value of BY is zero is used.

FIG. 12 is a block diagram of a white balance circuit using this method. The light that has passed through the lens group 1 composed of a plurality of lenses for zooming and focusing is
After being photoelectrically converted by the image sensor CCD 2, the color separation circuit 3
Then, the three primary color signals of R, G, and B are extracted, and the G color signal is directly input to the camera process and the matrix circuit 6 via the R amplification circuit 4 and the B amplification circuit 5, respectively. Then, the luminance signal Y and the color difference signals RY and BY of red and blue are generated and sent to the video circuit 7.

At the same time, the two color difference signals are integrated by the integrating circuits 17 and 18, respectively, for a sufficiently long time, and the gain control circuits 13 and 14 are respectively integrated into the amplifier circuits 4 of the R and B so that the result becomes zero. Adjust the gain of 5.

[0006]

SUMMARY OF THE INVENTION The above-mentioned method is used for various color distributions of a screen photographed by a video camera.
It is premised that if the time constants of the integration circuits 17 and 18 are lengthened and the color distributions thereof are averaged, the color components forming the color distributions cancel each other out and approximate a white screen state. However, in the above-mentioned configuration, the feedback always works, so that when a subject having an uneven color integration result on the screen is photographed, the white balance shifts to the complementary color side and an unstable correction operation is performed. I have a problem.

Therefore, a white balance adjusting device capable of performing stable correction without wobbling is disclosed in Japanese Patent Laid-Open No. 4-988. This apparatus sets an operation mode and a stop mode for white balance correction, and shifts the white balance correction from the stop mode to the operation mode only when the color difference signal obtained from the color signal exceeds a specific range.
As a result, the unstable white balance correction is not performed even when a subject having a slight deviation in the color integration result on the screen is photographed.

However, when the angle of view of the lens at the time of shooting is narrow or the distance to the subject is short and the effective area entering the screen is small, there is a large deviation in the integration result of the colors in the screen. It tends to occur. Therefore, if the set value in the above-mentioned specific range is small, the white balance correction easily shifts from the stop mode to the operation mode, resulting in unstable operation. On the other hand, if this set value is set to a large value, the instability due to the subject color is eliminated, but it is conceivable that correction will not be performed even if the light source actually changes and the wavelength distribution of light changes.

[0009]

SUMMARY OF THE INVENTION The present invention is a white balance adjusting device for performing white balance adjustment by correcting the gain of a color signal in a picked-up video signal with a gain correction amount. Gain control means for evaluating the screen to calculate the target value of the gain correction amount, gain correction amount increasing / decreasing means for changing the gain correction amount so as to approach the target value, and gain correction amount within a predetermined range from the target value. The gain correction amount increasing / decreasing unit prohibits the gain correction amount from being changed, and the gain correction amount increasing / decreasing unit changes the gain when the gain correction amount when the gain is fixed exceeds the predetermined range from the target value. A gain correction amount fixing releasing means for releasing prohibition of change of the correction amount is provided, an effective area in the image pickup screen is obtained from an angle of view of the lens and a subject distance, and the size of the predetermined range is changed according to the effective area. It is characterized by

Further, as another means, when the gain correction amount falls within a predetermined range from the target value, gain correction amount fixing means for prohibiting the change of the gain correction amount by the gain correction amount increasing / decreasing means and the gain signal are obtained from the color signal. When the level of the color difference signal to be obtained exceeds a predetermined allowable range with respect to the reference level, a gain correction amount fixing releasing means for releasing the prohibition of the gain correction amount by the gain correction amount increasing / decreasing means is provided, and the angle of view of the lens and the object It is characterized in that the effective area in the image pickup screen is obtained by obtaining the distance, and the predetermined allowable range is changed according to the effective area.

Furthermore, when the color difference signal obtained from the color signal changes by a predetermined amount with respect to the level when the change of the gain correction amount by the gain correction amount increasing / decreasing means is changed by a predetermined amount, the gain correction amount by the gain correction amount increasing / decreasing means is changed. A gain correction amount fixing releasing means for releasing the prohibition is provided, an effective area in the image pickup screen is obtained by obtaining a field angle of the lens and a distance to the subject, and the predetermined amount is changed according to the effective area. To do.

[0012]

Since the present invention is configured as described above, when the angle of view is narrow or the distance between the objects is short, a sufficient number of objects are not included in the screen and the colors in the screen are biased. , Hold white balance adjustment in stop mode.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a circuit block diagram of an automatic white balance adjusting circuit of a color video camera according to this embodiment. The light passing through the lens group 1 is imaged on the CCD 2 and photoelectrically converted, and then extracted by the color separation circuit 3 as three primary color signals of R, G, and B. The R and B signals of these three primary color signals are input to the camera process and matrix circuit 6 together with the G signal through the R and B amplifier circuits 4 and 5, respectively, and the luminance signal Y and the red and blue signals are respectively inputted based on these signals. Color-difference signals R-Y and B-Y are generated and supplied to the video circuit 7 and subjected to known processing. Further, the RY and BY signals are simultaneously supplied to the selection circuit 21.

The selection circuit 21 sequentially selects one of the two color difference signals RY and BY by the selection signal S1 from the timing circuit 25 for each field. RY → It is output to the A / D converter 22 in the subsequent stage in the order of BY, RY, ... The selection signal S
1 is created based on the vertical sync signal obtained from the sync separation circuit 24 as described later.

The A / D converter 22 has color difference signals RY and B selected by the selection circuit 21 at a predetermined sampling period.
-One of Y is sampled and converted to a digital value,
This value is output to the integrator 23. By the way, the timing circuit 25 uses the camera process and the vertical and horizontal synchronizing signals from the matrix circuit 6 and the fixed oscillator output for driving the CCD 2 to display an image pickup screen of 8 × 8 6 pixels.
.. are divided into four rectangular regions A11, A12, A13, ... And a switching signal S2 for taking out the output of the selection circuit 21 in these regions by time division is output to the integrator 23 for each region.

Upon receipt of the switching signal S2, the integrator 23 adds the A / D converted value of the output of the selection circuit 21 for each field over one field period, that is, digitally integrates for every 64 fields, and this 1 When the integration for the field is completed, the integrated value is stored in the memory 26 as a color evaluation value. As a result, the digital integrated values of the color difference signals RY corresponding to the 64 areas in a certain arbitrary field are obtained as the 64 color evaluation values rij (i, j: 1 to 8). .
In the next field, the color difference signal B-
Since Y is selected, as a result of integration in each area of the adder 23, digital integration values of each area of the color difference signal BY are obtained as 64 color evaluation values bij. Thus, when the integration of the two fields of the color difference signals RY and BY is completed, the values of 64 areas of the color evaluation values rij and bij are held in the memory 26. After that, the same operation as described above is repeated, and the color evaluation value rij is obtained in the next field, and the color evaluation value bij is obtained in the next field.
It will be updated sequentially.

The latest color evaluation value r obtained as described above
ij and bij (i, j: 1 to 8) are the screen evaluation circuit 27.
And calculated as the screen color evaluation values Vr and Vb of the entire screen of each color difference signal based on the following equations 1 and 2.

[0018]

[Equation 1]

[0019]

[Equation 2]

The numbers 1 and 2 are obtained by dividing the total sum of all 64 color evaluation values rij and bij of each area by the number of areas and
The average value for each area is calculated as the screen color evaluation value. The screen color evaluation values Vr and Vb are the gain control circuit 28,
It is sent to the first evaluation value comparison circuit 30 and the second evaluation value comparison circuit 31.

The gain control circuit 28 corrects the current gains of the R and B amplifier circuits 4 and 5 to make the screen color evaluation values Vr and Vb, which are the color evaluation values of the entire screen, zero. A correction value signal corresponding to the correction values Gpr and Gpb for the gain is generated and output to the correction value comparison circuit 29.

Next, the correction value comparison circuit 29, the first and the second
The operation of the evaluation value comparison circuits 30 and 31 will be described.

The correction value comparison circuit 29 is constructed as shown in FIG. That is, the current gain correction values Gmr and Gmb stored in the R and B correction value memories 33 and 34 and adjusting the current gains of the R and B amplifier circuits 4 and 5, and the gain correction value Gm.
By evaluating the screen generated by the gain control by r and Gmb, the new correction values Gpr and Gpb obtained from the gain control circuit 28 are compared by the R correction value comparator 29a and the B correction value comparator 29b, respectively. As a result, when the R correction value comparator 29a determines that Gmr = Gpr, the control signal Pr1 is an H level signal, and Gmr ≠ Gpr.
If it is determined that the L level signal is output to the correction value increasing / decreasing circuit 35 as the control signal Pr1. At this time, if Gmr <Gpr, an H level signal is output as the control signal Pr2, and if Gmr> Gpr, an L level signal is output as the control signal Pr2 to the correction value increasing / decreasing circuit 35.

The B correction value comparator 29b also makes the same determination, and when it is determined that Gmb = Gpb, an H level signal as the control signal Pb1 and Gmb ≠ Gpb.
When it is determined that the L level signal is output as the control signal Pb1 to the correction value increasing / decreasing circuit 35, Gmb <
If it is Gpb, an H level signal is given as the control signal Pb2, and if Gmb> Gpb, it is given as L as the control signal Pb2.
The level signal is output to the correction value increasing / decreasing circuit 35.

At the same time, in the R correction value comparator 29a, the absolute value │Gmr-Gpr│ of the difference between the input correction values Gmr and Gpr.
However, the B correction value comparator 29b calculates the absolute value | Gmb-Gpb | of the difference between Gmb and Gpb, and the correction value adder 2
Sent to 9c.

In the correction value adder 29c, the sum of these absolute values, that is, | Gmr-Gpr | + | Gmb-Gpb | is calculated, and in the correction value comparator 29e, the correction value threshold value calculation circuit 44 described later is used. The magnitude relationship with the calculated threshold value TG stored in the correction value threshold memory 29d is compared. As a result, when the expression 3 is established, the control signal P1 becomes H
When the level signal is satisfied and the equation 4 is satisfied, the L level signal is output as the control signal P1.

[0027]

[Equation 3]

[0028]

[Equation 4]

The first evaluation value comparison circuit 30 is constructed as shown in FIG. First, in the first R evaluation value subtractor 30a, the absolute value | Vr-V1r | of the difference between the screen color evaluation value Vr output from the screen evaluation circuit 27 and the R reference value V1r stored in advance in the R reference value memory 30c. Is the first B evaluation value subtractor 30
b, the screen color evaluation value Vb and the B reference value memory 30d in advance.
Absolute value of the difference from the B reference value V1b stored in | Vb−
V1b | is calculated and sent together to the first evaluation value adder 30e.

In the first evaluation value adder 30e, the sum of these,
| Vr−V1r | + | Vb−V1b | is calculated, in the first evaluation value comparator 30g, is calculated by the first evaluation value threshold value calculation circuit 45 described later, and stored in the first evaluation value threshold value memory 30f. The magnitude relationship with the threshold value TV1 is compared.
As a result, when the expression 5 is established, an H level signal is output as the control signal P2, and when the expression 6 is established, an L level signal is output as the control signal P2.

[0031]

[Equation 5]

[0032]

[Equation 6]

The second evaluation value comparison circuit 31 is constructed as shown in FIG. First, in the second R evaluation value subtractor 31a, the absolute value | Vr-V2r | of the difference between the screen color evaluation value Vr output from the screen evaluation circuit 27 and the R evaluation value V2r stored in advance in the R evaluation value memory 31c. However, the second B evaluation value subtractor 31
b, the screen color evaluation value Vb and the B evaluation value memory 31d in advance.
Absolute value | Vb− of the difference from the B evaluation value V2b stored in
V2b | is calculated and both are sent to the second evaluation value adder 31e.

In the second evaluation value adder 31e, the sum of these,
That is, | Vr-V2r | + | Vb-V2b | is calculated, and the second
In the evaluation value comparator 31g, the second evaluation value threshold value calculation circuit 46 described later calculates the second evaluation value threshold value memory 31.
The magnitude relationship with the threshold TV2 stored in f is compared. As a result, when the expression 7 is established, an H level signal is output as the control signal P3, and when the expression 8 is established, an L level signal is output as the control signal P3.

[0035]

[Equation 7]

[0036]

[Equation 8]

A method of calculating the correction value threshold value TG, the first evaluation value threshold value TV1 and the second evaluation value threshold value TV2 will now be described. Reference numeral 140 denotes a well-known zoom mechanism used in a general video camera. By displacing the zoom lens in the lens group 1, the focal length of the lens system of the entire camera is changed to obtain a desired zoom range from a wide angle to a telephoto range. It becomes possible to select the angle of view of. The zoom mechanism 14
From 0, a signal indicating the lens position of the zoom lens is output to the subsequent angle-of-view detection circuit 141.

The angle-of-view detection circuit 141 receives the position signal of the zoom lens, detects the position in the zoom area at this time, and detects the horizontal position of the screen from the relationship between the zoom position and the angle of view shown in FIG. The angle of view Rw (unit is radian) and the angle of view RL in the vertical direction are calculated. By the way, as is obvious in FIG. 11, the angle of view Rw, R
L becomes large.

Reference numeral 142 is a well-known focus mechanism which measures the distance to the object using infrared rays or the like, and moves the focusing lens of the lens group 1 back and forth in the optical axis direction according to the object distance to bring the object into focus. The information on the subject distance L obtained by this focus mechanism is input to the effective area calculation circuit 143 in the subsequent stage.

In the effective area calculation circuit 143, the field angles Rw and RL from the field angle detection circuit 141 and the focus mechanism 14 are used.
Based on the subject distance L from 2, the effective amount (area) of all the subjects included in the screen (everything displayed on the entire screen including the main subject and the background) is calculated. Specifically, the effective area S is obtained by the equation 9.

[0041]

[Equation 9]

In this equation, Rw × L represents the effective length in the horizontal direction of all subjects, and RL × L represents the effective length in the vertical direction of all subjects. The effective area S thus obtained is calculated by the correction value threshold value calculation circuit 144, the first evaluation value threshold value calculation circuit 145,
And the second evaluation value threshold value calculation circuit 46.

The correction value threshold value calculation circuit 44 calculates the correction value threshold value TG by the formula 10 based on the input effective area S. Here, FIG. 14 shows the relationship of the equation 10.

[0044]

[Equation 10]

Further, the first evaluation value threshold value calculation circuit 45 calculates the first evaluation value threshold value TV1 by the equation 11 based on the input effective area S. Here, FIG. 15 shows the relationship of Expression 11.

[0046]

[Equation 11]

Further, the second evaluation value threshold value calculation circuit 46 calculates the second evaluation value threshold value TV2 by the formula 12 based on the input effective area S. Here, FIG. 16 shows the relationship of Expression 12.

[0048]

[Equation 12]

As described above, each threshold value calculation circuit has an effective area S
As is smaller, each threshold is set proportionally larger. This is because as the effective area S becomes smaller, the types of subjects included in the screen are limited, and the colors in the screen tend to be biased. This is to prevent it from moving to the side.

Therefore, the coefficients Atg, TG0, Atv1, TV10 and Atv in the equations 10, 11 and 12 are used.
2. The TV 20 is set in advance based on the actual measurement value of the experiment.

The threshold value TG set by the above equation 10 is used as the correction value threshold value memory 2 of the correction value comparison circuit 29.
9d to update the contents of this memory. Similarly, the threshold TV1 set by the equation 11 updates the contents of the first evaluation value threshold memory 30f of the first evaluation value comparison circuit 30, and the threshold TV2 set by the equation 12 is set by the second evaluation value comparison circuit. The contents of the second evaluation value threshold value memory 31f of 31 are updated.

The results compared by the correction value comparison circuit 29, the first evaluation value comparison circuit 30, and the second evaluation value comparison circuit 31 are input to the stability determination circuit 32 as control signals P1, P2, P3. It

The stability determination circuit 32 is constructed as shown in FIG.
The control signals P1, P2, P3 are input to the OR gate 51. The switch 52 has a function of selectively connecting the fixed contact 52a to which the control signal P1 is applied or the fixed contact 52b connected to the output of the OR gate 51 and the fixed contact 52c connected to the output terminal to the output terminal. The switching is controlled by the output control signal P4 generated at 1) and is connected to the fixed contact 52b side when the signal P4 is at the H level and is connected to the fixed contact 52a side when the signal P4 is at the L level.

Next, the operation of the stability determination circuit 32 will be described. First, the H level control signal P1 is output to the stability determination circuit 3
2 is input, the output of the OR gate 51 is always at the H level, and therefore the output control signal P4 is at the H level regardless of which fixed contact the switch 52 has.
Eventually, the switch 52 will be connected to the fixed contact 52b side. In this state, the output control signal P4 is at H level as long as at least one of the control signals P1, P2 and P3 is at H level. Next, assuming that the control signals P1, P2, and P3 that are all L level are input to the stability determination circuit 32, the output of the OR gate 51 becomes L level, so that the output control signal P4 becomes L level and the switch 52 is connected to the fixed contact 52a side. In this state, the output control signal P4 is at L level as long as the control signal P1 is at L level.

That is, when the equation 3 is satisfied in the correction value comparison circuit 29, the stability determination circuit 32 issues an H level output control signal P4, and this H level control signal P4 functions as a white balance stop signal as described later. .

On the other hand, in the correction value comparison circuit 29,
However, in the first evaluation value comparison circuit 30, Equation 6 is
When Expression 8 is both satisfied in the evaluation value comparison circuit 31, the stability determination circuit 32 issues an L level control signal P4, and this L level control signal P4 functions as a white balance operation signal.

The control signal P4 is input to the second evaluation value comparison circuit 31 and the correction value increasing / decreasing circuit 35. In the second evaluation value comparison circuit 31, as shown in FIG. 4, the edge detector 31h receives this control signal P4. Edge detector 31
The pulse h is emitted only when the control signal P4 changes from the L level to the H level. When the switch 31i receives this pulse, the switch 31i closes and allows the R evaluation value memory 31c and the B evaluation value memory 31d to pass the screen color evaluation values Vr and Vb, and the memories 31c and 31d display the screen immediately after the passage. The R evaluation value V2r and the B evaluation value V2b are updated with the color evaluation value.

Therefore, the screen color evaluation values Vr and Vb at the time when the white balance correction shifts from the operation mode to the stop mode, that is, at the time when the operation mode ends, are respectively the R evaluation value memory 3
1c and B evaluation value memory 31d, R evaluation value V2r and B
It is stored as the evaluation value V2b.

The configuration of the correction value increasing / decreasing circuit 35 which receives the current gain correction amounts Gmr, Gmb and the control signals Pr1, Pr2, Pb1, Pb2 is as shown in FIG. That is, the correction value increasing / decreasing circuit 35 includes six switches and R and B increasing circuits 46, 4
8 and R and B reduction circuits 47 and 49.
The switches 40 and 41 are controlled to be switched by the control signal P4, a signal indicating the gain correction amount Gmr is applied to the contact 40c, the fixed contact 40a is connected to the output terminal 35a, and the fixed contact 40b is connected to the contact 42c of the switch 42. It is connected. The switch 42 is switched and controlled by the control signal Pr1, the fixed contact 42a is connected to the output terminal 35a, and the fixed contact 42b is connected to the contact 44c of the switch 44. The switch 44 is switched and controlled by the control signal Pr2, and the fixed contacts 44a and 44b are connected to the R increase and R decrease circuits 46 and 47, respectively. Here, the outputs of the R increase and R decrease circuits 46 and 47 are led to the output terminal 35a.

Similarly, the contact 41c of the switch 41 is
A signal indicating the gain correction amount Gmb is applied to the fixed contact 41a.
Is the output terminal 35b, and the fixed contact 41b is the switch 4
3 is connected to the contact 43c. The switch 43 is switched and controlled by the control signal Pb1, the fixed contact 43a is the output terminal 35b, and the fixed contact 43b is the switch 45.
Is connected to the contact point 45c. The switch 45 is switched and controlled by the control signal Pb2, and the fixed contacts 45a, 4
5b is connected to B increasing and decreasing circuits 48 and 49, respectively. Here, the B increase and B decrease circuits 48 and 49 outputs are led to the output terminal 35b.

Next, the operation of the correction value increasing / decreasing circuit 35 will be described. First, when the H-level control signal P4 is input to the switch 40 and the switch 41, that is, when the white balance correction is in the stop mode, the switch 40 has the fixed contact 4
0a side and the switch 41 is on the fixed contact 41a side, and the values Gmr and Gmb stored in the R correction value memory 33 and the B correction value memory 34 are the gain correction values Gr and Gb as they are.
Is output to the output terminals 35a and 35b, and the gains of the R and B amplifier circuits 4 and 5 are adjusted. Next, the control signal P4
Is at the L level, that is, when the white balance is in the operation mode, the switch 40 is on the fixed contact 40b side and the switch 41 is on the fixed contact 41b side, and the R correction value memory 33 and the B correction value are set. Correction value G stored in memory 34
mr and Gmb are input to the switches 42 and 43, respectively.

The switch 42 is on the fixed contact 42a side when the control signal Pr1 is at the H level, that is, when the correction value comparison circuit 29 determines that Gmr = Gpr, and the value stored in the R correction value memory 33 is The gain correction value Gr is output as it is, and the gain of the R amplifier circuit 4 is adjusted. Next, when the control signal Pr1 becomes L level, that is, when the correction value comparison circuit 29 determines that Gmr ≠ Gpr, the switch 42 is on the fixed contact 42b side, and the R correction value memory 33.
The correction value Gmr stored in is input to the switch 44. On the other hand, the switch 43 also operates similarly to the switch 42, and when the control signal Pb1 is at the H level, B
The value stored in the correction value memory 34 is output as it is as the gain correction value Gb, and when the control signal Pb1 becomes L level, the value stored in the B correction value memory 34 is
It is input to the switch 45.

When the control signal Pr2 is at the H level, that is, when the correction value comparison circuit 29 determines that Gmr <Gpr, the switch 44 is on the fixed contact 44a side and the correction value stored in the R correction value memory 33. Gmr is the R increase circuit 46
Is input to, and a predetermined constant value r0 is added and output as a gain correction value Gr. That is, Gr = Gmr + r
It becomes 0. When the control signal Pr2 becomes L level,
That is, when the correction value comparison circuit 29 determines that Gmr> Gpr, the switch 44 is on the fixed contact 44b side, the correction value Gmr is input to the R reduction circuit 47, and the fixed amount value r0.
Is subtracted and output as a gain correction value Gr, that is, G
The gain of the R amplification circuit 4 is adjusted by setting r = Gmr−r0. On the other hand, the switch 45 performs the same operation as the switch 44, and when the control signal Pb2 is at the H level, B
The correction value Gmb stored in the correction value memory 34 is added with a constant amount value b0 by the B increasing circuit 48, and the control signal P
When b2 becomes L level, the correction value Gmb is subtracted by the constant amount value b0 in the B reduction circuit 49 to obtain the gain correction value Gb.
The output of the B amplifier circuit 5 is adjusted.

The R and B gain correction values Gr and Gb output from the correction value increasing / decreasing circuit 35 are stored in the R correction value memory 3 respectively.
3 and B are stored again in the correction value memory 34 and used in the next field as the current correction values Gmr and Gmb for white balance adjustment. Therefore, the R and B correction value memory 33,
The contents of 34 are output terminals 35a and 35b for each field.
It will be changed with the correction value from.

In the R amplifier circuit 4, the gain when amplifying the R signal changes according to the gain correction amount Gr, the gain is fixed to 1 when the correction value Gr is zero, and the correction value Gr changes in the positive direction. If so, the gain increases, and if it changes in the negative direction, the gain decreases. Similarly, in the B amplifier circuit 5, the gain correction amount Gb
The amplification gain of the B signal changes in accordance with the above, and the gain is fixed at 1 when Gb = 0.

The operation of each circuit described above will be described with reference to FIGS.
An example will be described in which a screen like this is taken.

First, the operation when the white balance control shifts from the operation mode to the stop mode on the screen of FIG. 17 will be described. Now, assuming that the gain correction value Gmr stored in each of the R correction value memory 33 and the B correction value memory 34,
It is assumed that the Gmb controls the amplification gains of the R amplification circuit 4 and the B amplification circuit 5 so that the white balance is properly maintained.
Here, for example, when the screen color evaluation value changes due to the switching of the illumination light from the fluorescent light to the incandescent light, the gain control circuit 2
The gain correction amounts Gpr and Gpb calculated in 8 change as shown in FIG. 7, and based on the comparison result in the correction value comparison circuit 29, the correction value increase / decrease circuit 35 stores the correction value memories 33 and 34 in R and B respectively. When the stored gain correction amount is increased / decreased and changed from Gmr, Gmb to Gmr ', Gmb', the relation of Equation 3 is established,
The H-level control signal P1 is output. In FIG. 7, the range in which the relationship of the expression 3 is established is a square area surrounded by the chain line 100 centering on Gpr and Gpb. Further, the size of this square depends on the threshold value TG itself, and is set to a value that allows the correction value threshold value calculation circuit 44 to determine that the gain of white balance adjustment may be fixed in the current effective area of the image pickup screen. There is. When the stability determination circuit 32 receives this and outputs the H-level control signal P4, the correction value increasing / decreasing circuit 35 stops increasing / decreasing the gain correction amount, and the white balance correction enters the stop mode.

In this way, the gain correction value increasing circuits 46 and 48
Alternatively, if the R or B increasing circuits 4 and 5 gradually change the gains in the decreasing circuits 47 and 49 to perform the white balance adjustment, and the gain correction value change is within the threshold TG for each field, the white balance adjustment is performed. In order to suppress the fluctuation of the gain, the gain correction amount is stopped increasing and decreasing, the gain correction value immediately before this stop is maintained, and the gains of the R and B increasing circuits 4 and 5 are fixed to a constant gain determined by this correction value. It Incidentally, the correction value at this time is kept held in the R and B correction value memories 33 and 34 while the stop mode is maintained. In other words, the gain of the R and B increasing circuits 4 and 5 during the stop mode is fixed by the correction value stored in the memory immediately before the stop mode.

Next, the operation of shifting the white balance adjustment from the stop mode to the operation mode will be described.

Now, temporarily, the gain correction values Gmr and G stored in the R correction value memory 33 and the B correction value memory 34, respectively.
It is assumed that the amplification gains of the R amplification circuit 4 and the B amplification circuit 5 are controlled by mb, and the white balance is in an appropriate state. Here, the gain correction amount obtained based on the screen color evaluation value is shown in FIG.
It is not necessary to change the gain correction amount as long as it changes within a certain range surrounded by the chain line 100 from Gmr and Gmb like Gpr 'and Gpb' in FIG. To be judged.

However, when the illumination light is switched from the incandescent lamp to the fluorescent lamp again, and the gain correction amounts Gpr and Gpb change like Gpr "and Gpb", the gain correction value Gr, When Gb is fixed to the correction values Gmr and Gmb held in the memories 33 and 34, it is determined that the proper white balance cannot be obtained, and the correction value comparison circuit 29 outputs L
The level control signal P1 is output.

Next, with respect to the same change in the screen color evaluation value,
The operation performed by the first evaluation value comparison circuit 30 will be described. First, in an appropriate white balance state, the screen color evaluation values Vr and Vb are V1r and V1b like Vr 'and Vb' in FIG.
From the above, it is not judged that the screen color evaluation value has changed as long as it changes within the range of the chain line 101 depending on the threshold value TV1, that is, within the range where the expression 5 holds. However, when the screen color evaluation value changes like Vr "and Vb" due to the change of the light source and the equation 6 is satisfied, the first evaluation value comparison circuit 30 outputs the L-level control signal P2. It

Here, the reference values V1r and V1b are preset to the screen color evaluation value of each color difference signal when a completely achromatic subject whose entire screen is white is photographed, and in this embodiment, the camera process is used. In the color difference signals R-Y and B-Y output from the & matrix circuit 6, the reference values V1r and V1b are both set to zero when a completely achromatic subject is photographed. Therefore, in equation 5, | Vr-V1
r | is a value indicating the distance from the zero level of the color difference signal RY, in other words, a value indicating how far from the achromatic color, and similarly | Vb-V1b | is the value from the zero level of the color difference signal BY. This is a value indicating the degree of separation, and the sum of the two indicates the degree of separation from white for the entire screen. Therefore, by setting the threshold value TV1 as an allowable width of the proper white balance, it can be determined that the proper white balance adjustment is realized on the image pickup screen if the expression 5 is satisfied. It is not necessary to operate, and if Equation 6 is satisfied, the image capturing screen immediately exceeds the allowable range in which it can be determined that proper white balance adjustment has been realized, and immediately performs white balance adjustment accompanying increase / decrease of the gain correction value. It is necessary to set the mode.

Further, for the same change in the screen color evaluation value,
The operation performed by the second evaluation value comparison circuit 31 will be described. R correction value memory 31c and B correction value memory 31d
Stores the screen color evaluation values when the white balance correction enters the stop mode as R and B evaluation values V2r and V2b, and the screen color evaluation value V newly calculated by the screen evaluation is stored.
r and Vb are V2r and V2b like Vr 'and Vb' in FIG.
From the above, it is not determined that the screen color evaluation value has changed as long as it changes within the range of the chain line 102 depending on the threshold value TV2, that is, within the range where Expression 7 holds.

However, when the screen color evaluation value changes like Vr "and Vb" due to the change of the light source and the equation 8 is satisfied, the second evaluation value comparison circuit 31 outputs the L level control signal P3. Is output.

Here, the threshold value TV2 is such that the change of the current screen color evaluation values Vr, Vb with respect to the screen color evaluation values V2r, V2b when the stop mode is entered does not require the white balance adjustment by the gain increase / decrease. It is a value for setting a permissible range that can be determined, and is set by the second evaluation value threshold value calculation circuit 46 so that the white balance gain may be fixed in the current effective area of the imaging screen.

Thus, in the correction value comparison circuit 29,
However, it is confirmed that the first evaluation value comparison circuit 30 satisfies the equation 6 and the second evaluation value comparison circuit 31 satisfies the equation 8, and the L level control signals P1, P2 and P3 are output. In response to this, the stability determination circuit 32 receives the control signal P4 of L level.
At the time of outputting, the correction value increasing / decreasing circuit 35 starts increasing / decreasing the gain correction amount, and the white balance correction enters the operation mode.

In other words, the condition for the white balance correction to enter the operation mode from the stop mode is that the gain correction values Gpr and Gpb calculated from the evaluation of the screen are maintained as the actual correction values Gr and Gb while the stop mode continues. Correction value Gmr, G
mb is changed by a threshold value TG or more, and the screen color evaluation values Vr, Vb are changed by a threshold value TV1 or more from a reference value which is set in advance when a completely achromatic subject is photographed. When all of the three conditions that the values Vr and Vb change to the threshold value TV2 or more with respect to the value at the time of entering the stop mode are satisfied at the same time, it is difficult to obtain a proper white balance in the stop mode, and the operation mode is considered to be difficult. It becomes.

Next, the operation when a screen as shown in FIG. 18 in which the human face in FIG. 17 is zoomed up is photographed will be described.

When the human face occupies a large part of the screen as shown in FIG. 18, the red component in the screen color evaluation value increases, and the gain correction amounts Gpr and Gpb obtained based on this increase.
It changes like Gpr3 and Gpb3 in FIG. If the correction value threshold value is still shown in the range of the chain line 100 in FIG. 8, the equation 4 holds, and the correction value comparison circuit 29 outputs the L-level control signal P1. However, as the human face is zoomed up, the effective area S calculated by the effective area calculation circuit 43 decreases, and the correction value threshold TG calculated by the correction value threshold calculation circuit 44 based on this decreases. Along with this, the range of the chain line 100 becomes large like the range surrounded by the solid line 110. Therefore, the gain correction amounts Gpr and Gpb obtained based on the screen color evaluation value are Gpr3 and Gp.
Even if it changes like b3, the equation 3 is still established, and the correction value comparison circuit 29 outputs the H-level control signal P1.

The screen color evaluation value input to the first evaluation value comparison circuit 30 is also the chain line 10 like Vr3 and Vb3 in FIG.
It changes outside the range of 1, but as the effective area S decreases,
Since the first evaluation value threshold TV1 is increased and the range of the chain line 101 is increased to the range surrounded by the solid line 111, Formula 5 is established, and the first evaluation value comparison circuit 30 outputs H
The level control signal P2 is output.

Further, the screen color evaluation value input to the second evaluation value comparison circuit 31 is also the chain line 1 like Vr3 and Vb3 in FIG.
Although it changes outside the range of 02, the second evaluation value threshold TV2 increases as the effective area S decreases, and the solid line 112
Since the range is surrounded by, the expression 7 is established, and the second evaluation value comparison circuit 31 outputs the H-level control signal P3.

In this way, if all of the control signals P1, P2, P3 are maintained at the H level, or any one of them is maintained at the H level, the control signal P4 becomes the H level and the white balance adjustment is performed. Remains in stop mode.

As described above, by changing the size of each threshold value according to the effective area S of the screen, it is possible to realize the white balance correction operation which is hardly influenced by the color of the subject.

In the above embodiment, the focus mechanism 42
Employs a so-called distance measuring method for measuring the distance to a subject using infrared rays, but the present invention is not limited to this method, and the applicant of the present application has already filed Japanese Patent Application No. 62-29493.
As proposed in No. 8, by using the principle that the high frequency component level of the luminance signal of the picked-up image signal becomes maximum at the in-focus position, this high frequency component is integrated for each field and focused. A so-called TTL method or the like in which an evaluation value is calculated and the focus lens is displaced to a position where the focus evaluation value is maximum may be substituted. In this case, the lens position of the focus lens at the time of focusing is also determined. The information shown is supplied to the effective area calculation circuit 43 in the subsequent stage as information indicating the subject distance.

In the above embodiment, the A / D converter 22 and the integrator 23 are commonly used to digitally integrate the levels of the two signals of the color difference signals RY and BY to extract them. However, the integrated value of each signal could only be updated in a 2-field cycle, but if an A / D converter and an integrator were provided exclusively for each signal, each signal level would be 1 field. It goes without saying that it can be updated for each card. It goes without saying that the operation of a series of circuit blocks from the screen evaluation circuit 27 to the correction value increasing / decreasing circuit 35 in FIG. 1 can be processed by software using a microcomputer.

[0087]

As described above, according to the present invention, the angle of view is narrow, or the distance between the subjects is short, and the screen does not include a sufficient number of subjects. When it occurs, it makes it difficult for the white balance adjustment to shift from the stop mode to the operation mode, prohibits the white balance adjustment based on this screen evaluation, shifts the white balance to the complementary color side, and the proper white balance is obtained. The occurrence of inconvenience that cannot be obtained is reduced.

[Brief description of drawings]

FIG. 1 is an overall circuit block diagram of an embodiment of the present invention.

FIG. 2 is a circuit block diagram of a correction value comparison circuit 29 according to an embodiment of the present invention.

FIG. 3 is a circuit block diagram of a first evaluation value comparison circuit 30 according to an embodiment of the present invention.

FIG. 4 is a circuit block diagram of a second evaluation value comparison circuit 31 according to an embodiment of the present invention.

FIG. 5 is a circuit block diagram of a stability determination circuit 32 according to an embodiment of the present invention.

FIG. 6 is a circuit block diagram of a correction value increasing / decreasing circuit 35 according to an embodiment of the present invention.

FIG. 7 is a diagram for explaining changes in the gain correction amount at the time of transition from the operation mode to the stop mode according to the embodiment of the present invention.

FIG. 8 is a diagram illustrating a change in the threshold value TG according to the embodiment of the present invention.

FIG. 9 is a diagram illustrating changes in the threshold TV1 according to the embodiment of the present invention.

FIG. 10 is a diagram for explaining changes in the threshold TV2 according to the embodiment of the present invention.

FIG. 11 is a diagram showing a relationship between a zoom position and an angle of view.

FIG. 12 is a circuit block diagram of a conventional example.

FIG. 13 is a diagram illustrating area division according to an embodiment of the present invention.

FIG. 14 is a characteristic diagram showing the relationship between the effective area of the screen and the correction value threshold TG.

FIG. 15 is a characteristic diagram showing the relationship between the effective area of the screen and the first evaluation value threshold TV1.

FIG. 16 is a characteristic diagram showing the relationship between the effective area of the screen and the second evaluation value threshold TV2.

FIG. 17 is a diagram illustrating an image pickup screen in a state where the angle of view is wide.

FIG. 18 is a diagram illustrating an image pickup screen in a state where the angle of view is narrow.

[Explanation of symbols]

 28 gain control circuit 35 correction value increasing / decreasing circuit 40 switch 41 switch 141 view angle detection circuit 142 focus mechanism

Claims (3)

[Claims] 1. A white balance adjustment for performing white balance adjustment by correcting a gain of a color signal in an imaged video signal obtained by photoelectrically converting incident light from a subject incident through a lens by a gain correction amount. In the apparatus, a gain control unit that evaluates an image pickup screen based on a color signal to calculate a target value of a gain correction amount; a gain correction amount increasing / decreasing unit that changes the gain correction amount so as to approach the target value; When the amount falls within a predetermined range from the target value, the gain correction amount changing means is prohibited from changing the gain correction amount,
When the gain correction amount exceeds the predetermined range from the target value while the change is prohibited, the control unit cancels the prohibition of the change of the gain correction amount by the gain correction amount increasing / decreasing unit, and the angle of view of the imaging screen by the lens. An angle-of-view detection unit that detects the distance and a subject-distance detection unit that detects the distance to the subject and outputs it as subject-distance information. The effective area in the imaging screen is calculated from the angle of view and the subject-distance information. A white balance adjusting device, wherein the size of the predetermined range is changed according to the above. 2. A white balance adjustment for correcting a gain of a color signal in a picked-up image signal obtained by photoelectrically converting incident light from a subject incident through a lens by a gain correction amount to perform white balance adjustment. In the apparatus, a gain control unit that evaluates an image pickup screen based on a color signal to calculate a target value of a gain correction amount; a gain correction amount increasing / decreasing unit that changes the gain correction amount so as to approach the target value; When the amount falls within a predetermined range from the target value, the gain correction amount changing means is prohibited from changing the gain correction amount, and the level of the color difference signal obtained from the color signal exceeds a predetermined allowable range from a predetermined reference level. In this case, the control means for canceling the prohibition of the change of the gain correction amount by the gain correction amount increasing / decreasing means, the angle of view detecting means for detecting the angle of view of the imaging screen by the lens, and the distance to the subject are detected to detect the object. Photo A subject distance detecting means for outputting as distance information, and obtaining an effective area in the imaging screen from the angle of view and the subject distance information, and changing the size of the predetermined allowable range according to the effective area. White balance adjustment device. 3. A white balance adjustment for correcting a gain of a color signal in an imaged video signal obtained by photoelectrically converting incident light from a subject incident through a lens with a gain correction amount to perform white balance adjustment. In the apparatus, a gain control unit that evaluates an image pickup screen based on a color signal to calculate a target value of a gain correction amount; a gain correction amount increasing / decreasing unit that changes the gain correction amount so as to approach the target value; When the amount falls within a predetermined range from the target value, the gain correction amount changing means is prohibited from changing the gain correction amount,
When the color difference signal obtained from the color signal exceeds a predetermined allowable range with respect to the level when the change of the gain correction amount by the gain correction amount increasing / decreasing unit is prohibited, the change of the gain correction amount by the gain correction amount increasing / decreasing unit is changed. A control means for canceling the prohibition, an angle-of-view detection means for detecting the angle of view of the image pickup screen by the lens, and an object-distance detection means for detecting the distance to the object and outputting it as object-distance information. A white balance adjusting apparatus, characterized in that an effective area in an image pickup screen is obtained from the subject distance information, and the size of the predetermined allowable range is changed according to the effective area.