JPH03289793A - White balance adjusting device - Google Patents

Abstract

PURPOSE:To minimize the deviation of white balance in the pictures of objects with the same color and large area by suppressing the contribution of a color information signal to white balance adjustment in an area where the variation of the color information signal goes less than a reference value within an image pickup picture lower than another area, and varying the reference value corresponding to the focal distance of a lens. CONSTITUTION:A zooming mechanism 40 varies the focal distance of the lens system of whole camera by displacing a zoom lens, and a desired state can be selected from the area zooming from wide-angle to telephoto. A focal distance detection circuit 41 detects the position of the zoom lens, and calculates the focal distance of the lens system based on the position, and outputs a result as lens focal distance information. A same color processing circuit 57 reduces the weight of the area when the areas with the same color exist continuously. Thereby, it is possible to minimize the deviation of the white balance in the pictures of the objects with the same color and large area.

Description

DETAILED DESCRIPTION OF THE INVENTION (A) Field of Industrial Application The present invention is based on a captured video signal obtained from an image sensor.
The present invention relates to a white balance adjustment device for a color video camera that controls mill balance.

(B) Conventional Technology In a color video camera, it is necessary to perform white/French control in order to correct for differences in the wavelength distribution of light due to the light source.

This control includes red (hereinafter referred to as R), blue (hereinafter referred to as B), green (hereinafter referred to as G).
) by adjusting the gain of each color signal so that the ratio of the three primary color signals becomes 1:1:1. Generally, a method is used in which the gain is adjusted so that the integral value of the screen color difference signals R-Y and B-Y becomes zero, as shown in, for example, Japanese Patent Application Laid-Open No. 62-35792 (HO4N9/73). ing.

FIG. 2 is a block diagram of a white balance circuit using this method.

The light that has passed through the lens (1) is transferred to an imaging device (CCD) (2).
), the color separation circuit (3, R, G, B
The G signal thus obtained is directly input, and the R and B signals are input to the color process and matrix circuit (6) via the R amplification circuit (4) and the B amplification circuit (5). Signal Y, red and blue color difference signals R-Y and B-Y are generated and sent to the video circuit (7).
sent to.

At the same time, the two color difference signals are respectively sent to the integrating circuit (17).
In (18), the gain control circuits (13) and (14) adjust R, B so that the integration is performed for a sufficiently long time and the result becomes zero.
The gain of each amplifier circuit (4), (5) is adjusted.

In this method, the screen shot by a video camera,
If we take measures such as increasing the time constant of the integration circuit (17 (18)) for various color distributions and average these color distributions, each color component that makes up the color distribution will cancel each other out,
It is assumed that a substantially white screen state can be approximated.

However, with this method, when the color of the subject itself is biased, for example when green grass or blue sky occupies a large area on the screen, or when taking a close-up of a person wearing a red sweater, the screen may become distorted. Even if the overall color distribution is averaged, the screen will not be white and the white balance will be disrupted.
If you perform the white balance adjustment as described above for such a subject, the gain will change in the direction of canceling out the biased color, the white balance will shift to the complementary color side, and proper color reproduction will not be possible. have.

Therefore, the present applicant first filed Japanese Patent Application No. 01-300239 (
(filed on November 17, 1999) proposes a mill balance adjustment device that solves this drawback.

This prior art technology reduces the contribution of the color information signal to white balance adjustment in areas where the amount of variation in the color information signal is less than the reference amount in the imaging screen compared to other areas.
This is intended to accommodate screens that include large-area objects.

FIG. 3 is a circuit block diagram of the same system.

Similar to the conventional example, the light passing through the lens (1) is C
After being imaged on a CD (2) and subjected to photoelectric conversion, it is extracted as three primary color signals of R, G, and H in a color separation circuit (3). The R and B signals among 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 (5)), and based on these, the luminance signal (Y ) and red, blue celestial color difference signals (
(RY) and (B-Y) are created and supplied to the video circuit (7) and subjected to well-known processing.
-Y) are simultaneously supplied to the selection circuit (21). The selection circuit (21) selects one of the three signals, the luminance signal (Y), the color difference signals (R-Y), and (B-Y), according to the selection signal (Sl) from the timing circuit (25).
It selects each field sequentially, (Y) → (R-Y
)→(B-Y)→(Y)→(RY)→... are output to the subsequent A/D converter (22) for each field. In addition, the selection signal (Sl) is connected to the synchronous separation circuit (24) as described later.
It is created based on the vertical synchronization signal obtained from

The A/D converter (22) receives the signal (Y(R-Y)(B) selected by the selection circuit (21) at a predetermined sampling period.
-Y) into a digital value and outputs this value to the integrator (23). By the way, the timing circuit (25
) is based on the camera process and the vertical and horizontal synchronization signals from the matrix circuit (6) and the fixed oscillator output that drives the CCD (2), and the imaging screen is divided into 64 8x8 rectangular areas shown in Figure 4. (All), (A12), (A1
3)...(A88), that is, (Aij) (ij=1-8
(an integer number of ), and a switching signal (
S2) is output to the integrator (23).

The integrator (23) receives the switching signal (S2) and adds the A/D converted values of the output of the selection circuit (21) for each region over one field period, that is, digitally integrates each of the 64 regions. When the integration for one field is completed, this integral value is stored in memory (26
) As a result, the digital integral value of the luminance signal (Y) corresponding to 64 regions in an arbitrary field is obtained as 64 luminance evaluations 1 (yij) (i, j: 1 to 8). It will be done. Also, in the next field, the selection circuit (21) selects the color difference signal (R-Y), so as a result of the integration in each region of the adder (23), the digital signal for each region of the color difference signal (R-Y) is The integral value is obtained as 64 color evaluation values (rij).Furthermore, in the next field, the color difference signal (B-Y) is selected by the selection circuit (21), so the integral value of the adder (23) is As a result, the digital integral value for each region of the color difference signal (B-Y) is obtained as 64 color evaluation values (bij).In this way, the luminance signal (Y), the color difference signal (R-Y) (B-Y) When the integration of the three fields is completed, the luminance evaluation value (y i j )
The 64×3 value of the color evaluation value (rij (bij)) will be stored in the memory (26). From now on, the same operation as described above will be repeated, and in the next field, the luminance signal (yij) will be stored in the memory (26). , and in the next field, the color evaluation value (ri
j) will be updated sequentially.

FIG. 6 shows the internal structure of this integrator (23) in more detail. Each A/D converted data is supplied to a switching circuit (61). This switching circuit (61) receives the switching signal (S2) and converts each A/D conversion value into an adder (F
It has the role of supplying data to the adder for the area where the sampling point of the corresponding data exists in l1) (Fl2)... (F8g). That is, if a sampling point of a certain arbitrary data is included in the area (A1.1), this data is supplied to the adder (Fil) for the area (All). Note that the adder (Fij) (ij=1~
8) is set for the area (Aij), and a total of 64 adders are prepared. A holding circuit (Qij) is provided after each adder, and each added value is temporarily held in each holding circuit.

The data held in each holding circuit is input to the adder again, and
It is added to the next input data. In addition, each holding circuit is reset for each field based on the vertical synchronization signal, and only the held data immediately before this reset is stored in the memory (26
). Therefore, one set of adder and holding circuit constitutes one digital integrating circuit, and a total of 64 integrating circuits constitute the integrator (23). Digital integral values are input to the memory (26) for each region.

When the integration for one field is completed, this integrated value is held in the memory (26) as a brightness evaluation value or color evaluation value. As a result, digital integral values for each region of the luminance signal (Y) corresponding to 64 regions in a certain arbitrary field are obtained as 64 luminance evaluation values (yij).

Furthermore, in the next field, the color difference signal (R-Y) is selected by the selection circuit (21), so as a result of the integration by the integrator (23), the digital integral value for each region of the color difference signal (R-Y) is obtained. Similarly, in the next field, the color evaluation value 1 of the color difference signal (B-Y) is obtained as 64 color evaluation values (r ij).
f(bij) is obtained.

Note that the reference level, that is, the zero level, of the luminance and color difference signals input to the A/D converter (22) is set in advance to the level obtained when photographing a completely achromatic surface, and therefore, each It goes without saying that the A/D converted value can take not only positive values but also negative values.

The latest color evaluation fi(yij) obtained as described above
(rij) (bjj) (i, j: 1 to 8) are input to the same color processing circuit (27). This same color place 8! The circuit (27) determines whether or not a plurality of areas that are continuous in the vertical or horizontal direction among the 64 areas have the same color.
The number of times the colors are determined to be the same is counted, and its operation is shown in the flowchart of FIG.

In this flowchart, 5TEP (100) (10
In 1), initial settings are made to perform judgment from the area (All), and in 5TEP (102), weighting is performed by the amount (wij
) is initialized, and the weighting of all regions is first set to an amount of 1. 5TEP (104) determines whether the difference 1rij-ri-1jl in the color evaluation values of the color difference signals (R-Y) in areas that are consecutively arranged in the vertical direction exceeds the reference value (C1). Similarly, 5TEP (105) (
106), the color difference signal (B
-Y) color evaluation value difference 1bij-bi -1jl and brightness evaluation value difference 1)'1j-)'1-1j1 are determined whether they exceed the reference values (C2) and (C3), respectively. . The difference between the evaluation values is the reference value (CI) (C2) (C
3), it is determined that these two consecutive areas above and below the screen are the same color, and 5TEP (107)
The weighting amount (wij) is halved at .

Note that the reference value (CI) (C2) (C3) is a threshold value at which the colors can be regarded as the same, and is a constant set in advance based on experimentally measured values.

5TEP (103) is 5TEP (103) because there are no areas above this for the 8 areas lined up at the top of the screen.
It has the function of avoiding the judgments of TEP (104) to (106).

In 5TEP (109), the difference in color evaluation values of color difference signals (R-Y) in areas that are consecutively lined up in the left and right direction of the screen is 1.
It is determined whether or not r i j-r i j-11 exceeds a predetermined value (C1), and similarly 5TEP (110) (
111), the color difference signal (B
-Y) color evaluation value difference 1bij-bij-II and brightness evaluation value difference 1yij-yij-11 are respectively the reference value (C2
), it is determined whether or not it exceeds (C3). Then, when the difference between the evaluation values does not exceed the reference value (CI) (C2) (C3), it is determined that the two consecutive left and right areas of the screen are of the same color, and in 5TEP (112) The amount of weighting is halved. Note that 5TEP (108) is 5TEP (109) to (111) because there are no areas to the left of the eight areas lined up on the left edge of the screen.
) has the function of avoiding the judgment of The above series of determinations as to whether the colors are the same or not are performed for the entire area by 5TEP (113).

The weighting amount (wij) of each area determined in this way by the same color processing circuit (27) is inputted to the screen evaluation circuit (28), and the color difference signal (R -Y
)(B-Y) are calculated as screen color evaluation values (Vr) (Vb) for each entire screen.

These equations (1) and (2) are calculated using the color evaluation value (ri
Weighting means averaging all the sums of j)(bjj).

The gain control circuits (29) and (30) control the respective gains of the R and B amplifier circuits (4) and (5) so that the screen color evaluation values (Vr) (Vb), which are the color evaluation values of the entire screen, are both zero. is under control.

(C) Problems to be Solved by the Invention The above-mentioned method is a white balance of the color information signal in the area where the amount of variation of the color information signal is less than the reference amount (CI) (C2) (C3) within the imaging screen. By reducing the contribution to adjustment compared to other areas, it is possible to cope with screens that include objects of the same color and large area.

However, in this method, the reference value for determining the amount of variation is fixed, and for example, when the focal length of the lens is short at the wide-angle end or when the distance to the subject is long
Various objects are likely to be included in each area, and the average evaluation value of each area is less likely to vary. Therefore, even though a plurality of colors are mixed, they may be determined to be the same color, resulting in a decrease in the accuracy of white balance adjustment.

Further, in a region where the absolute value of the evaluation value is large, the amount of change when changing at the same ratio becomes large, and as a result, it becomes difficult to determine that the colors are the same. However, in reality, an area close to an achromatic color with a low absolute value of the evaluation value should make a large contribution to the white balance adjustment control, which causes a decrease in the accuracy of the adjustment.

(d) Means for Solving the Problems The present invention performs white balance adjustment based on the color signal information in the imaging signal, and adjusts the white balance in an area where the amount of variation in the color information signal is below a reference value within the imaging screen. In order to reduce the contribution of the color information signal to the white balance adjustment compared to other areas, the reference amount is varied depending on the focal length of the lens, the distance to the subject, and the absolute value of the color signal information, or It is characterized by changing the amount of contribution reduction.

(E) Function Since the present invention is constructed as described above, it is possible to always accurately reduce the influence of objects of the same color and large area under various photographing situations.

(f) Example Embodiments of the present invention will be described according to the drawings.

FIG. 1 is a circuit block diagram of an automatic white balance circuit according to a first embodiment.

Note that explanations of parts common to the conventional example will be omitted.

(40) is a well-known zoom mechanism used in general video cameras, and by displacing the zoom lens that makes up this zoom mechanism, the focal length of the entire lens system of the camera is changed, allowing zooming from wide-angle to telephoto. It becomes possible to select a desired state from the area.

The focal length detection circuit (41) detects the position of the zoom lens, calculates the focal length (f) of the lens system from this position, and outputs it as lens focal length information.

The same color processing circuit (57) is basically the same as in Fig. 2 (
When areas of the same color exist consecutively, weighting of the corresponding areas will even out the effect of reducing the amount, but weighting is used when determining the amount as shown in the flowchart in Figure 7 based on the lens focal length information. A reference value change routine (200) for changing the reference value (CI) (C2) (C3) is added.

The reference value change routine (200) is as shown in FIG.
First, as in 5TEP (201), it is determined whether the focal length (f) is shorter than a preset reference focal length (f, ), that is, on the wide-angle side, and if it is on the wide-angle side, 5T
Standard value (CI) (C2) (C3) at EP (202)
On the other hand, if it is longer than the reference focal length (f,), that is, on the telephoto side, the reference value (CI) (C2) (C
3) is maintained as is. Based on the reference value obtained in this way, the same operation as in the conventional example is performed.

Therefore, compared to telephoto mode, where a specific subject occupies a large area of the screen and tends to bias certain colors, the standard values are smaller at wide-angle mode, where there are various subjects within each area and color bias is less likely to occur. Therefore, 5TEP (104) to (106) or 5TEP (109) to (111)
), unless the amount of variation is extremely small, it is difficult to determine that the colors are the same, and it is possible to prevent erroneous determination that the colors are the same.

Further, FIG. 9 is a circuit block diagram of the second embodiment. In this figure, (42) is a well-known focusing mechanism that measures the distance to the subject using infrared rays, etc., and moves the lens (1) forward or backward in the optical axis direction according to this subject distance to bring it into focus. , object distance (L) obtained with the 7-o-cus mechanism
The information is input to the same color processing circuit (67) and used for the same color determination.

The same color processing circuit (67) basically operates in the same way as the chart 70 in FIG. 7, as in the first embodiment. However, the reference value changing routine (200') changes the reference values (CI) (C2) (C3) used in determining the weighting amount based on the subject distance as shown in FIG. In other words, when the subject is far away, the actual area of the subject that falls within each area of the screen becomes large, and various objects fall within the area, which tends to reduce the differences in color and luminance signals between the areas. Taking this into consideration, it is determined in 5TEP (210) whether the subject distance (L) is greater than a preset reference subject distance (L,), and it is determined that it is greater, that is, the subject is in a far position. 5 TEP (211
), the reference values (C1), (C2, and C3) are halved in the same manner as in the first embodiment, and the same color determination operation is performed thereafter, so that when the subject is far away, each evaluation value is Unless an extremely large variation is obtained, the colors will not be determined to be the same, and erroneous determination of the same color will be prevented.

In this embodiment, a distance measuring method using infrared rays is shown as a focusing mechanism, but the method is not limited to this. For example, a method of moving the lens forward and backward so that the highest frequency component of the luminance signal can be extracted can be used. In this case, the object distance may be made to correspond to the position of the 7 orcus lens with respect to the CCD.

Moreover, FIG. 11 is a flowchart of the third embodiment,
The difference with Figure 5 is 5TEP (300) (30
1) is added. That is, it attempts to calculate from the absolute value of each evaluation value without setting a constant reference value (CI) (C2) (C3) in advance.
At TEP (300) (301), 1/8 of the evaluation value at that time is set as the reference value for each area. That is, C1=r i
j/8, C2=bij/8, and C3-yij/8. As a result, an area where the evaluation value changes at a rate above a certain amount is not considered to be an area of the same color, and as a result, the absolute value of each evaluation value is prevented from influencing the same color determination.

Further, FIG. 12 is a flowchart of the fourth embodiment, and the difference from FIG. 11 is that 5TEP (107) (112
), 5TEP (400) (401) are added. That is, the weighting reduction amount is made variable in accordance with the deviation of the color evaluation value from the absolute value. Here, as the size of the color evaluation value, each color evaluation value (rij) (bij)
The square root of the sum of the squares of , that is, the distance from white on the color plane is used.

In 5TEP (400) (401), a= r 1)+ i J/R=(3) w i
j = w i j / a...
(4) (where R is a constant set in advance based on actual measurement values) is calculated. This is 5TEP (104) to (10
6) and 5TEP For the areas determined to be the same color in (109) to (111), the degree of departure of the same color from the achromatic color is determined as a using equation (3), and further, equation (4) The weighting makes the amount (wij) inversely proportional to a, and the weighting of the highly saturated areas far from white greatly reduces the amount, preventing the contribution of the low chroma areas close to white from dropping. I'm here. It goes without saying that if the value of a is less than a certain value, it is possible not to reduce the contribution.

As described above, white balance adjustment can be adjusted by varying the reference amount or the amount of contribution reduction depending on the focal length of the lens, the distance to the subject, and the absolute value of color signal information. This makes it possible to more appropriately select and process effective areas.

It is also possible to use one or more of the first to fourth embodiments simultaneously.

Furthermore, it is also possible to process the operations of the same color processing circuit and the screen evaluation circuit (28) in software using a microcomputer, and considering that this process itself includes ambiguity, , control using fuzzy inference is also possible.

(G) Effects of the Invention As described above, according to the present invention, deviations in white balance can be minimized for various screens including objects of the same color and large area.

[Brief explanation of drawings]

FIG. 1 is a circuit block diagram of the first embodiment of the present invention, FIGS. 7 and 98 are the same flowchart, FIG. 9 is a circuit block diagram of the second embodiment, and ts10 is the same flowchart.
FIG. 1 is a flowchart of the third embodiment, and FIG. 12 is a flowchart of the fourth embodiment. (4)...R amplifier circuit, (5)...B amplifier circuit, (
57) (67)... Same color processing circuit, (28)...
Screen evaluation circuit.

Claims (7)

[Claims] (1) In a white balance adjustment device that performs white balance adjustment that controls the gain of each color signal based on the color information signal in the captured video signal, the white balance adjustment device adjusts the white balance by controlling the gain of each color signal based on the color information signal in the captured video signal. A white balance adjustment device characterized by reducing the contribution of a color information signal to white balance adjustment compared to other areas, and making the reference value variable according to a focal length of a lens. (2) The white balance adjustment device according to item 1, wherein the reference value is made smaller as the focal length becomes shorter. (3) In a white balance adjustment device that performs white balance adjustment that controls the gain of each color signal based on the color information signal in the captured video signal, the white balance adjustment device adjusts the white balance to control the gain of each color signal based on the color information signal in the captured image signal. A white balance adjustment device characterized by reducing the contribution of a color information signal to white balance adjustment compared to other areas, and making the reference value variable according to the distance to a subject. (4) The white balance adjustment device according to item 3, wherein the reference value decreases as the distance to the subject increases. (5) In a white balance adjustment device that performs white balance adjustment that controls the gain of each color signal based on the color information signal in the captured video signal, the white balance adjustment device adjusts the white balance to control the gain of each color signal based on the color information signal in the captured image signal. A white balance adjustment device characterized by reducing the contribution of a color information signal to white balance adjustment compared to other areas, and making the reference value variable according to the absolute value of the color information signal. (6) The white balance adjustment device according to item 5, wherein the reference value is increased as the absolute value of the color information signal increases. (7) Based on the color information signal in the captured video signal, perform white balance adjustment to control the gain of each color signal, and adjust the color information signal in the area where the variation amount of the color information signal is less than the reference value within the captured image screen. A white balance adjustment device that reduces contribution to white balance adjustment compared to other areas, characterized in that in areas where color information signals are close to achromatic colors, the reduction amount of the reduction operation is made smaller.