JPH08102960A - Video camera - Google Patents

Abstract

PURPOSE: To attain quick tracking to an object for white balance adjustment by selecting a higher threshold level when a value of an adjacent region corresponding to a same color region number is a reference value or over and a lower level when the reference value or less. CONSTITUTION: An integration device 23 obtains integrated values of color difference signals R-Y, B-Y corresponding to optional 64 sets of field areas and stores luminance evaluation values Yij, color evaluation values rij, bij (i, j=1-8) for the 64 areas to a memory 26 and a microcomputer 27 uses the values for white balance adjustment. The microcomputer 27 adjusts and changes gains of R, B amplifiers 4, 5 so that the color evaluation value is zero. When the frequency of the same color adjacent area is less than a threshold level T1 and number of areas not reflected on a light source color is less than a threshold level T2, a correction restart decision threshold level M for keeping stable mode is set higher. Furthermore, when the frequency is more than the threshold level T1 and the number of areas is more than the threshold level T2, the threshold level M is set smaller to easily release the stable mode.

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 an image pickup video 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. 11 is a block diagram of a white balance correction circuit using this method. Light that has passed through a lens group 1 composed of a plurality of zoom and focus lenses is photoelectrically converted by a solid-state image sensor (CCD) 2, and then is separated by a color separation circuit 3 into three primary colors of R, G, and B. The G color signal is directly extracted, and the R and B color signals are input to the camera process and the matrix circuit 6 through the R amplification circuit 4 and the B amplification circuit 5, respectively, and the luminance signals Y, red and blue are respectively output. Color difference signals R-Y and B-Y 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.

In this system, various color distributions of a screen photographed by a video camera are devised such that the time constants of the integrating circuits 17 and 18 are lengthened and the color distributions are averaged. It is premised that the color components that make up the color distribution cancel each other out and that they can be approximated to a substantially white screen state. However, in the above-mentioned configuration, since the feedback always works, the correction amount of the amplification gain easily fluctuates depending on the subject, and there is a problem that unstable white balance correction is performed.

Therefore, a white balance adjusting device capable of performing stable correction without wobbling is disclosed in Japanese Patent Laid-Open No. 4-988. This device sets the correction operation mode and stable mode for white balance correction, executes white balance correction, and once realizes the optimum white balance state,
The white balance adjustment is stopped, that is, the stable mode in which the amplification gains of the R and B signals are fixed is entered. In this stable mode, the white balance correction is shifted from the stop mode to the operation mode only when the change in the color difference signal exceeds a certain threshold value.

[0008]

In the above-mentioned conventional example, the threshold value for determining the necessity of the transition from the stop mode to the operation mode is set as a fixed value in advance, but it is unstable when the start and stop are frequently performed. When the threshold value is fixed to a relatively large value in order to prevent white balance adjustment, a specific color area occupies a large area on the screen, and colors that are not white even when the entire screen is averaged are biased. When the white balance adjustment is completed in a special shooting condition that is not convenient when performing the white balance adjustment when shooting the subject or displaying the color of the light source, the subject changes due to panning etc. Even if such a special shooting state is canceled and it becomes a situation where the white balance adjustment should be executed immediately, the white balance adjustment is not started until the change of the color difference signal exceeds the threshold, and the white balance adjustment is not started. Settling occurs is a problem that does not quickly follow the subject change.

[0009]

According to the present invention, a correction operation mode in which a gain of a color signal is changed based on a color information signal in a picked-up image signal to perform a white balance correction operation, and a gain of the color signal is fixed. A white balance adjusting device that selectively switches between two stable modes, that is, a color evaluation value detecting unit that detects a color information signal level as a color evaluation value for each of a plurality of areas set by dividing a screen. And a screen color evaluation value detection means for detecting the color information signal level of the entire screen as a screen color evaluation value, and for all of the plurality of areas, the color evaluation values are compared for each adjacent area to determine whether they are the same color. The value corresponding to the number of areas in which adjacent areas are determined to have the same color is the first
Same color area determination means for determining whether or not the reference value is exceeded, and change determination for determining whether or not the amount of change of the latest screen color evaluation value in the stable mode with respect to the previous screen color evaluation value exceeds the threshold value. Means and mode switching means for switching from the correction operation mode to the stable mode when the screen color evaluation value falls below the reference level during the correction operation mode, and switching from the stable mode to the correction operation mode when the amount of change exceeds a threshold value. The threshold value is increased when the value corresponding to the number of areas in which adjacent areas are determined to be the same color is determined to be smaller than the first reference value by the same color area determination means, and is determined to be larger than the first reference value. The feature is that the threshold value is reduced when

As another means, the light source color area determination for determining whether or not the number of areas having color evaluation values outside the distribution range of the color temperature change of the light source among the plurality of areas exceeds the second reference value. Means and a mode switching means for switching the mode from the stable mode to the correction operation mode when the amount of change exceeds a threshold value, and the light source color area determination means provides a color evaluation value outside the distribution range of the color temperature change of the light source. It is characterized in that the threshold value is increased when it is determined that the number of existing areas is smaller than the second reference value, and the threshold value is decreased when it is determined that the number of existing areas is larger than the second reference value.

[0011]

Since the present invention is configured as described above, there are few regions where the same color is continuous, and there are few regions of colors other than the highly saturated red and blue light source colors. When white balance correction is completed on a high-quality screen, shift from this shooting state to a subject with many areas where the same color continues or a subject with many colors other than the light source color,
When the screen becomes unreliable, it becomes difficult to restart the white balance correction. Conversely, when the white balance correction is completed on the unreliable screen, the shooting state shifts to a highly reliable screen. When you do, white balance correction is likely to be restarted quickly.

[0012]

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. Incident light that has passed through the lens group 1 is a solid-state image sensor (CCD) 2
After being imaged on the top and photoelectrically converted, in the color separation circuit 3,
It is taken out as three primary color signals of R, G and B. These three
The R and B signals of the 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 color difference of red and blue are respectively based on these signals. The signals R-Y and B-Y are created and supplied to the video circuit 7 where they are subjected to known processing. Also,
The Y, RY, and BY signals are simultaneously supplied to the selection circuit 21.

The selection circuit 21 receives the luminance signal Y and the color difference signals RY and B- in response to the selection signal S1 from the timing circuit 25.
One of the three Y signals is sequentially selected for each field, and Y → (RY) → (BY) → Y →
(R−Y) → (B−Y), ..., Every one field is output to the A / D converter 22 in the subsequent stage. The selection signal S1 is created based on the vertical sync signal obtained from the sync separation circuit 24 as described later.

The A / D converter 22 samples one of the luminance signal Y, the color difference signals RY and BY selected by the selection circuit 21 at a predetermined sampling period and converts it into a digital value. This value is output to the integrator 23. By the way, the timing circuit 25, based on the vertical and horizontal synchronizing signals from the camera process and the matrix circuit 6 and the fixed oscillator output for driving the CCD 2, displays an image pickup screen in a rectangular region A11 of 64 × 8 × 8 shown in FIG. , A12, A1
3 ... A88, and outputs to each integrator 23 a switching signal S2 for time-divisionally extracting the output of the selection circuit 21 in these areas.

Upon receipt of the switching signal S2, the integrator 23 adds the A / D conversion 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 the 1 When the integration for the field is completed, the integrated value is held in the memory 26 as a color evaluation value.

FIG. 12 shows the internal structure of the integrator 23 in more detail. Each A / D conversion value is supplied to the switching circuit 161. The switching circuit 161 receives the switching signal S2, and adds each A / D conversion value to the adder Gij prepared for each area.
(I, j: integer of 1 to 8), it has a role of supplying to the adder in the area where the corresponding sampling point exists. A holding circuit Hij is provided after each adder, and each added value is temporarily held in each holding circuit. Further, the data held in each holding circuit is input to the adder again and the next A / D
It is added to the converted value. Further, each holding circuit is reset for each field, and only the holding data immediately before this reset is supplied to the memory 26. Therefore, one digital integrating circuit is composed of one set of adder and holding circuit,
A total of 64 integrator circuits form the integrator 23, and the digital integrated value of each color difference signal is input to the memory 26 for each of 64 regions from each holding circuit for each field.

The reference level of the color difference signals input to the A / D converter 22, that is, the zero level, is set to a level obtained when a perfect achromatic surface is photographed, and is therefore digitized. Each color difference signal becomes not only a positive value, but also a negative value.Specifically, the digital integration operation adds the absolute value of the positive value, and conversely, the absolute value of the negative value. Will be subtracted.

As a result, the digital integrated value of the luminance signal Y corresponding to 64 regions in a certain arbitrary field is 6
It will be obtained as four luminance evaluation values yij. In the next field, the color difference signal RY is selected by the selection circuit 21.
As a result of integration in each area of the integrator 23, digital integration values for each area of the color difference signal RY are obtained as 64 color evaluation values rij. Further, in the next field, since the color difference signal BY is selected by the selection circuit 21, as a result of integration in each area of the integrator 23, the digital integrated value of each area of the color difference signal BY is 64.
It is obtained as individual color evaluation values bij. Thus, when the integration of the three fields of the luminance signal Y, the color difference signals RY, and BY is completed, the luminance evaluation value yij, the color evaluation value rij,
The value of 64 areas of bij is held in the memory 26. After that, the same operation as described above is repeated, and the luminance evaluation value yij in the next field and the color evaluation value rij in the next field are sequentially updated.

The latest luminance evaluation value yij and color evaluation values rij, bij (i, j: 1-8) obtained as described above.
From the memory 26 to the microcomputer
It is input to 27 and used for white balance adjustment. FIG. 3 is a flow chart for explaining the processing in the microcomputer. The flowchart will be described below.

At step 100, 6 is obtained by the equations 1 and 2.
From the color evaluation values rij and bij for four areas, the color evaluation values of the color difference signals of the entire screen are calculated as the screen color evaluation values Vr and Vb.

[0021]

[Equation 1]

[0022]

[Equation 2]

That is, 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 calculating the average value of one area as the screen color evaluation value. Vr,
It means to be calculated as Vb.

Step 200 is a step of determining whether or not the white balance correction is stopped, that is, in the stable mode, and specifically, it is determined whether or not a stable flag described later is in the set state. When the stability flag is in the set state, it means that the white balance correction operation is stopped and the amplification gains of the R and B amplifiers 4 and 5 are fixed. Conversely, when the stability flag is in the reset state. Means that the white balance correction operation is in the correction operation mode.

Step 300 is a step of evaluating the screen color evaluation value and determining whether it is necessary to newly execute the white balance correction or whether the white balance correction operation is terminated because it is no longer necessary. Specifically, the determinations of steps 31 and 32 in the flowchart of FIG. 4 are executed. That is, in steps 31 and 32, the absolute values of the latest screen color evaluation values Vr and Vb are compared with a preset threshold value K, and both conditions | Vr | <K and | Vb | <K are satisfied. In other words, in other words, when the white balance correction operation up to the previous field causes the screen color evaluation values Vr and Vb to both be close to zero enough to fall below the threshold value K,
It is judged that the white balance correction is no longer necessary, and the white balance correction operation is terminated. It should be noted that the threshold value K is a value at which it can be considered that the white balance correction is unnecessary, and is a value determined in advance by an experiment.

In step 400, the latest screen color evaluation value V
The microcomputer 27 adjusts the respective gains of the R amplifier circuit 4 and the B amplifier circuit 5 so that both r and Vb become zero.
The gain adjustment signal is output, and the R and B amplifier circuits 4 and 5 change the gains of the R and B signals according to the adjustment signal.
It should be noted that the R and B gain adjustment signals change for each screen, that is, for each field when the white balance correction operation is in the correction operation mode, but are maintained immediately before that in the stable mode. Then, the gains of the R and B amplifier circuits are also fixed to the values just before in this stable mode.

In step 500, it is determined whether or not a plurality of vertically adjacent regions in the 64 regions have the same color, and as a result of this determination, the adjacent regions have the same color. Is a step of issuing an output signal indicating whether the number is larger or smaller than the reference number. Specifically, the determination operation based on the flowchart shown in detail in FIG. 5 is executed.

In the flow chart of FIG. 5, count values P and Q, which will be described later, are reset in step 51, initial settings for making a determination from the area A11 are made in steps 52 and 53, and in step 55, the values are continuously set in the vertical direction. Then, it is determined whether or not the difference | rij-ri-1j | of the color evaluation values of the color difference signals RY in the areas arranged side by side exceeds the predetermined value C1. Of the color evaluation values of the color difference signal BY in the area continuous with | b
ij-bi-1j | and the difference in luminance evaluation value | yij-yi
It is determined whether −1j | exceeds the predetermined values C2 and C3, respectively. The difference between the evaluation values is the predetermined value C1, C
When it does not exceed 2, C3, it is judged that these two areas, which are upper and lower, have the same color, and the count value P is determined in step 58.
Is incremented. The predetermined values C1, C2, C3
Is a threshold that can be regarded as the same color for each evaluation value.

The step 54 has a function of avoiding the series of determinations in steps 55 to 58, since there is no area above the eight areas arranged at the top of the screen.

In step 60, it is judged whether or not the difference | rij-rij-1 | of the color evaluation values of the color difference signals RY in the areas which are continuously arranged in the left-right direction of the screen exceeds the predetermined value C1. Similarly, in steps 61 and 62, the difference | bi between the color evaluation values of the color difference signals BY in the left-right continuous region | bi
j-bij-1 | and the difference between the brightness evaluation values | yij-yij
It is determined whether -1 | exceeds the predetermined values C2 and C3, respectively. The difference between the evaluation values is the predetermined value C1, C
2, when it does not exceed C3
It is determined that the areas have the same color, and the count value Q is incremented in step 63. It should be noted that step 59 has a function of avoiding the determinations of steps 60 to 63 because there is no area on the left side of the eight areas arranged on the left end of the screen. The above-described series of same-color determination operation is executed in step 64 for the entire area of the screen.

The count values P and Q obtained as a result of these determinations become larger as the number of regions of the same color among the regions adjacent to each other in the vertical or horizontal direction increases. For example, in the image pickup screen as shown in FIG. 6, assuming that the shaded area is blue sky and the same color, P = 6 and Q = 11, whereas in the image pickup screen as shown in FIG. 7, P = 30, Q = 32. Therefore, the sum of the count values P and Q indicates the degree to which the continuous areas have the same color. Therefore, in step 65, it is judged whether or not the sum of both count values exceeds the threshold value T1, and if it exceeds this T1, step 8
00, and if it does not exceed 100, the process proceeds to step 700. Thus, step 500 ends.

In step 600, for each of the 64 areas, it is determined whether the number of areas that do not reflect the light source color is greater than the threshold value T2. Here, in general, considering the relationship between the color temperature change of the light source and each color difference signal, the color difference signal when the color temperature of the light source illuminating a white subject changes is as shown in the light source color temperature axis of FIG. Change. Therefore,
The set of color difference signals appearing in the first and third quadrants that do not include the light source color temperature axis does not reflect the color temperature of the light source and is preferably not considered as information when performing white balance adjustment. In other words, the screen where the average value of the color difference signal of the entire screen is far from the light source color temperature axis reflects the color of the subject itself more strongly than the color of the light source. It is not preferable to perform white balance correction on such a screen on the assumption that the components cancel each other out and can be approximated to a substantially white screen state.

In consideration of this, the color evaluation values of all 64 areas are plotted on the coordinates of FIG. 9 and it is determined whether or not this plot point exists in the area F surrounded by the diagonal line. .
Here, the region F corresponds to a light source color region that can be regarded as a light source color along the light source color temperature axis, and when the plot point is outside this region, it is not so preferable to perform white balance adjustment. It means that you are in a situation. The determination as to whether or not the area F exists is executed for all 64 areas. In FIG. 9, the color difference signals on the vertical axis and the horizontal axis in FIG. 8 are replaced with color evaluation values.

FIG. 10 is a flowchart showing the determination operation of step 600 more specifically. 10, in step 66, a count value R, which will be described later, is set.
Is reset, and initial settings for making a determination from the area A11 are made in steps 67 and 68. In step 69, whether or not plot points (bij, rij) of both color evaluation values are present in the area F. The count value R is incremented in step 70 only when it is determined to be outside the area F, and the same determination operation as this is performed in step 71.
Perform for all regions.

When the determination of the entire area is completed in this way, it is determined in step 72 whether the count value R exceeds the threshold value T2. Here, the threshold value T2 is a threshold value of the number of regions showing colors other than the light source color, which can be determined to be unfavorable for white balance adjustment, and the count value R exceeding the threshold value T2 means that the color does not reflect the light source color. It means that there are many areas where Thus, the count value R
If exceeds the threshold T2, the process proceeds to step 800, and if not exceeds, the process proceeds to step 700.

Steps 700 and 800 are steps for determining a restart determination threshold M, which will be described later. It is determined in step 500 that the frequency of adjacent areas having the same color is less than the threshold T1, and step 600 When it is determined that the number of regions that does not reflect the light source color is smaller than the threshold value T2 in step 700, the threshold value M is set to a relatively large value m1 in step 700 so as to easily maintain the stable mode.

Further, in step 500, it is judged that the frequency of adjacent areas having the same color is greater than the threshold value T1,
Alternatively, when it is determined in step 600 that the number of regions not reflecting the light source color is larger than the threshold value T2, the threshold value M is set to a value m2 smaller than the value m1 in step 800 so that the stable mode can be easily released. Set to.

Next, in step 900, the screen color evaluation values Vr, Vb are set as the screen color evaluation values Vr0, Vb0 of the previous screen for evaluation on the next screen, and in step 101, the stability flag is set.

In step 110, it is determined whether or not the expression 3 is satisfied. That is, the latest screen color evaluation value Vr and the screen color evaluation value V one field before set in step 900.
The difference between r0 (Vr-Vr0) and the latest screen color evaluation value Vb
Then, it is determined whether or not the absolute value of the sum of the differences (Vb-Vb0) of the screen color evaluation value Vb0 one field before set in step 900 is equal to or more than the threshold value M set in steps 700 and 800.

[0040]

(Equation 3)

Here, when the absolute value of the sum of the changes in the average value of the color evaluation values of the color difference signals RY and BY for the entire screen from the previous screen exceeds the threshold value, the stable mode is set. This means that the color of the entire screen has changed enough to restart the white balance correction operation in which the amplification gains of the R and B signals are fixed, and conversely, when the value is less than the threshold value M, a large screen change occurs. Means that the white balance correction based on new screen evaluation is not necessary until the stable mode is released.

Therefore, when it is determined that the white balance correction by the new screen evaluation is necessary, the process proceeds to step 120 to clear the stability flag, cancel the stable mode in the next field, and perform the new screen evaluation. When it is determined that the white balance correction is unnecessary, the step 120 is skipped and the stable mode is maintained in the next field.

Next, the operation of the microcomputer 27 will be described with reference to the flowchart of FIG. First, immediately after the video camera starts shooting, the white balance correction operation is naturally not in the stable mode, and the white balance correction operation is still not sufficiently operating, so that at least the absolute values of the screen color evaluation values Vr and Vb are absolute. One of the values does not become larger than the threshold value K and the white balance correction is not necessary, and the process proceeds from step 300 to step 400 and these screen color evaluation values Vr, Vb
R and B gain adjustment signals are created so that
And B amplifier circuits 4 and 5, and the gain adjustment of the R signal and the B signal is performed, and the well-known white balance correction operation is performed. That is, the white balance correction maintains the correction operation mode. The stability flag is in a reset state while the correction operation mode is maintained.

With the correction operation mode maintained, the microcomputer 27 causes the microcomputer 27 to store the luminance evaluation values yij and the color evaluation values rij, bi for 64 areas stored in the memory 26 for each field.
When j is input, the same white balance correction operation is continued. As a result, the screen color evaluation values Vr and Vb gradually converge to zero, and the absolute values of the screen color evaluation values Vr and Vb both fall below the threshold value K. If this happens, step 30
The process proceeds from 0 to step 500.

When the image pickup screen at the time of shifting to this step 500 is, for example, as shown in FIG. 6, the number of times that the regions connecting vertically and horizontally with the sky blue are the same color is 6 vertically and 11 horizontally. Therefore, assuming that the threshold T1 is 50, P + Q = 6 + 11 = 17 <T1, and it is not determined that there are many areas of the same color, and the process proceeds to step 600.

Color evaluation values rij, b of each area on the screen of FIG.
If the number of regions in which the plot points of ij exist in the light source color region F of FIG. 9 is smaller than the threshold value T2, step 600
Then, it is assumed that the color of the light source is reflected on this imaging screen, and the process proceeds to step 700.

In this way, when the process reaches the step 700 through the determination operations of the steps 500 and 600, the screen of FIG. 6 has a sufficiently small area of the same color, and the light source color to be the target of the white balance correction is sufficiently small. It is a screen that is reflected, and it is sufficiently reliable as an evaluation target of white balance correction, and the white balance correction made by evaluating such a screen is the optimum one. It is determined in step 300 that the evaluation values Vr and Vb are sufficiently small and white balance correction is no longer necessary.
Since the white balance correction is about to shift from the correction operation mode to the stable mode, frequent white balance correction causes fluctuations in the correction amounts of the amplification gains of the R and B signals, resulting in unstable white balance correction. To prevent this, the threshold M is set to a large value m1 so that the current state is maintained as much as possible and it is difficult to restart from the stable mode to the correction operation mode until it is recognized that the screen color has changed significantly.

After the threshold value M is set, the stability flag is set in step 101 to deactivate the white balance correction in the next field.

Therefore, even if the latest color evaluation values rij and bij are input to the microcomputer 27 in the next field and the screen color evaluation values Vr and Vb are calculated, the stability flag is in the set state, and therefore the process proceeds from step 200 to step 110. Therefore, the white balance correction operation in step 400 or the threshold M setting operation in steps 700 and 800 is not performed.

In this next field, step 11
If a large change does not occur in the screen or the light source of FIG. 6 such that the expression 3 does not hold according to the determination of 0, it is better to maintain the stable mode in which the white balance correction is not operated. By jumping over, the stable flag remains set, and the stable mode is maintained in the next field. In this case, even if the color of the screen shown in FIG. 6 changes a little at the time of shifting to the stable mode, the threshold value M is set to a relatively large value m1 as described above, and therefore the expression 3 is difficult to hold and the white value is white. Balance correction is not frequently performed.

Further, during the stable mode, in the situation where the screen of FIG. 6 is remarkably changed due to panning, tilting or the like or the light source is changed, it is necessary to immediately restart the white balance correction operation. Then, Equation 3 holds, the stability flag is cleared in step 120, and step 400 is performed again in the next field.
White balance correction is performed.

On the other hand, the white balance correction is executed in step 400 based on the imaged screen having a large number of sky blue shaded areas as shown in FIG. 7, and both screen color evaluation values in a certain field both fall below the threshold value K. In this case, it is determined in step 500 based on the color evaluation value in this field whether there are many areas of the same color. In this FIG. 7, as described above, the number of times that the areas connected vertically and horizontally on the screen of FIG. 7 have the same color is 30 in the vertical direction and 32 in the horizontal direction. Therefore, if the threshold value T1 is 50, P + Q = 30 + 32 = 6
Since 2> T1, it is determined that there are many areas of the same color, the process proceeds to step 800, and the threshold value M is set to a value m2 smaller than the value m1.

Therefore, in the stable mode of the next field transition, the mathematical expression 3 is likely to hold even for a small change in the color of the screen in FIG. 7 in step 110, and the stable mode is released sensitively to correct the white balance. Will be able to resume. Therefore, as shown in FIG. 7, areas of the same color are continuously expanded, so that even if the colors of the entire screen are averaged, white is not obtained, which is originally not desirable as an evaluation target when executing white balance correction. When the white balance correction for the screen with low reliability is completed and the mode shifts to the stable mode, if the color evaluation value changes due to the change of the screen, the white balance correction is restarted more quickly than in the case of FIG. 6 described above. hand,
When the subject changes due to panning or tilting, the stable mode is quickly released, and the fixed amplification gain of the R and B signals based on the evaluation of the unreliable screen is released.
White balance correction is performed on a new screen, and it is difficult to maintain the fixed gain on the complementary color side of the color of the same color area of the screen affected by the color of the subject itself.

Further, even when the white balance correction is completed for the screen on which the light source color is not reflected and the white balance correction is completed, the determination in step 600 moves to step 800 and the threshold value M becomes a small value m2. Is set. Therefore, in the stable mode after the next field,
When a change occurs in the color of the screen, the expression 3 is likely to hold and the stable mode can be quickly released and the white balance correction can be restarted. Therefore, for the unreliable screen that is not preferable for white balance correction, which is strongly influenced by the color of the subject itself without reflecting the color of the light source, the stable mode is released and the white balance correction is performed on a new screen. Is executed.

In the above-described embodiment, since the A / D converter 22 and the integrator 23 are respectively configured by one, the selection circuit 21 selects the luminance signal Y and the color difference signals RY and BY for each field. Since it was sequentially selected in, both the luminance evaluation value and both color evaluation values require 3 fields before updating,
In order to perform more accurate white balance correction, the selection circuit 21 of FIG. 1 is removed, and a dedicated A / D converter and integrator are independently provided for each of the luminance signal Y and both color difference signals. Is also possible. In this case, each of the three integrators has the same configuration as that of the integrator 23 in FIG. 1, and the evaluation value for 64 regions of each signal is derived from each integrator.

In determining the same color area in step 500, the count value P,
Although the total size of Q is used, this P + Q corresponds to the number of times adjacent regions have the same color, and P + Q also increases as the area of the same color region increases. In addition to this determination, the color evaluation value and the brightness evaluation value of the adjacent areas are actually compared, and whether the difference between the adjacent areas of the color evaluation values rij, bij and the brightness evaluation value yij is smaller than the threshold values C1, C2, C3. Needless to say, it is also possible to determine whether or not it is possible to count the number of areas that are actually determined to be small, and use this count value as a determination parameter instead of P + Q.

[0057]

As described above, according to the present invention, when the stable mode other than the correction operation mode is set and the white balance correction is once completed, the correction operation mode is continued after that and the gain of the color signal is gained. As an evaluation screen for white balance correction, while preventing unstable white balance correction that changes frequently, there are few areas where the same color is continuous and there are few areas of colors other than the highly saturated red and blue light source colors. When white balance correction is performed on a highly reliable screen, the threshold for restarting from the stable mode to the correction operation mode becomes large, and from this shooting state there are many areas where the same color is continuous due to panning etc. If you switch to shooting a subject with many colors other than colors and the screen becomes unreliable as an evaluation target for white balance correction, it will be difficult to restart white balance correction, and the subject itself Susceptible white balance correction the influence of the color components can be realized, on the contrary, when executing white balance correction in unreliable screen than the threshold is reduced,
It is possible to prevent the white balance correction from being promptly restarted when the screen shifts from this shooting state to a highly reliable screen, and the state where the white balance correction remains affected by the color of the subject itself is continued.

[Brief description of drawings]

FIG. 1 is a block diagram of one embodiment of the present invention.

FIG. 2 is a diagram illustrating screen division according to an embodiment of the present invention.

FIG. 3 is an overall flowchart of one embodiment of the present invention.

FIG. 4 is a flowchart detailing step 300 of one embodiment of the present invention.

FIG. 5 is a flowchart detailing step 500 of one embodiment of the present invention.

FIG. 6 is a diagram illustrating an imaging screen according to an embodiment of the present invention.

FIG. 7 is a diagram illustrating an imaging screen according to an embodiment of the present invention.

FIG. 8 is a diagram illustrating a change in color temperature of a light source on color coordinates.

FIG. 9 is a diagram illustrating a light source color area on color coordinates according to an embodiment of the present invention.

FIG. 10 is a flowchart detailing step 600 of one embodiment of the present invention.

FIG. 11 is a block diagram of a conventional example of the present invention.

FIG. 12 is a block diagram of an essential part of an embodiment of the present invention.

[Explanation of symbols]

 4 R amplifier 5 B amplifier 23 Integrator 27 Microcomputer

Claims (2)

[Claims] 1. A correction mode in which a gain of a color signal is changed based on a color information signal in an imaged video signal to perform a white balance correction operation, and a stable mode in which a gain of a color signal is fixed are selected. In a video camera equipped with a white balance adjusting device that switches in a single manner, a color evaluation value detection unit that detects a color information signal level as a color evaluation value for each of a plurality of areas set by dividing the screen, and a color of the entire screen. Screen color evaluation value detection means for detecting the information signal level as a screen color evaluation value, for all of the plurality of areas, to determine whether or not the same color by comparing the color evaluation value for each adjacent area, The same color area determination unit that determines whether or not the value that increases as the number of areas in which adjacent areas are determined to have the same color exceeds a first reference value, and the latest screen color evaluation value in the stable mode One screen before Change determination means for determining whether or not the amount of change with respect to a threshold value exceeds a threshold value, and when the screen color evaluation value falls below a reference level during the correction operation mode, the correction operation mode is switched to the stable mode, and the amount of change is A mode switching unit that switches from the stable mode to the correction operation mode when the threshold value is exceeded, and a value that increases as the number of regions in which adjacent regions are determined to be the same color by the same color region determination unit increases. Increases the threshold when it is determined that is smaller than the first reference value,
A video camera, wherein the threshold value is reduced when it is determined that the threshold value is larger than the first reference value. 2. A correction operation mode in which a gain of a color signal is changed based on a color information signal in an imaged video signal to execute a white balance correction operation, and a stable mode in which a gain of a color signal is fixed are selected. In a video camera equipped with a white balance adjusting device that switches in a single manner, a color evaluation value detection unit that detects a color information signal level as a color evaluation value for each of a plurality of areas set by dividing the screen, and a color of the entire screen. A screen color evaluation value detecting means for detecting the information signal level as a screen color evaluation value; and a number of areas in the plurality of areas where the color evaluation value exists outside the distribution range of the color temperature change of the light source, the second reference value. A light source color region determining means for determining whether or not to exceed, and a change determining means for determining whether or not the amount of change of the latest screen color evaluation value in the stable mode with respect to a value one screen before, exceeds a threshold value, The correction motion Mode switching means for switching from the correction operation mode to the stable mode when the screen color evaluation value falls below a reference level during the mode, and switching from the stable mode to the correction operation mode when the amount of change exceeds the threshold value; The threshold value is increased when the number of regions in which the color evaluation value exists outside the distribution range of the color temperature change of the light source is smaller than the second reference value by the light source color region determination unit, A video camera, wherein the threshold value is reduced when it is determined to be larger than a reference value.