JPH0828879B2 - White balance adjuster - Google Patents

Description

The present invention relates to a white balance adjusting device for a color video camera that controls white balance based on an imaged video signal obtained from an image sensor.

(B) Conventional technology In a cover video camera, it is necessary to control the white balance in order to correct the difference in the wavelength distribution of light depending on the 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. Generally, for example, as shown in JP-A-62-35792 (H04N9 / 73), a method of adjusting the gain so that the integrated value of the color difference signals RY and BY of the screen becomes zero is used. 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 the image sensor (CCD).
After photoelectric conversion in (2), the color separation circuit (3, R,
The G signal thus obtained, which is extracted as the three primary color signals of G and B, 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). 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 respectively integrated by an integrating circuit (17).
At (18), the gain control circuits (13) and (14) adjust the gains of the amplifier circuits (4) and (5) of R and B, respectively, so that they are integrated for a sufficiently long time and the result becomes zero.

In this method, if various color distributions of the screen shot by the video camera are devised, such as lengthening the time constant of the integrating circuit (17 (18), and averaging these color distributions. , The color components that make up the color distribution cancel each other out,
It is assumed that it can be approximated to a nearly white screen state.

However, with this method, when there is a bias in the color of the subject itself, for example, when a green grass or blue sky occupies a large area on the screen, or when a person wearing a red sweater is close up, Even if the entire color distribution is averaged, the white screen will not be displayed and the white balance will be lost.If such white balance adjustment is applied to such a subject, the gain will be canceled in the direction of canceling the uneven color. There is a drawback that the white balance changes and the white balance shifts to the complementary color side, and proper color reproduction cannot be performed.

Therefore, the present applicant previously filed Japanese Patent Application No. 01-300239 (Heisei 1
(Filed Nov. 17, 2013) proposes a white balance adjusting device that solves this drawback. This prior application technology reduces the contribution of the color information signal to the white balance adjustment in the area where the variation amount of the color information signal is less than the reference amount in the image pickup screen from other areas, so that the same color, large area It is intended to deal with a screen including the subject.

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

As in the conventional example, the light passing through the lens (1) is
After being imaged on the CCD (2) and photoelectrically converted, the color separation circuit (3) takes out the signals as three primary color signals of R, G and B. The R and B signals in these three primary color signals are respectively R
It is input to the camera process and the matrix circuit (6) together with the G signal through the B and B amplification circuits (4 (5)), and based on these, the luminance signal (Y) and the color difference signals (R-
Y) and (B-Y) are created and supplied to the video circuit (7) for known processing.
Each signal of Y) is simultaneously supplied to the selection circuit (21). The selection circuit (21) receives the luminance signal (Y) and the color difference signal (R−) according to the selection signal (S1) from the timing circuit (25).
One of the three signals of (Y) and (BY) is sequentially selected for each field, and (Y) → (RY) → (B
-Y)->(Y)->(RY)-> ... is output to the A / D converter (22) in the subsequent stage for each field. 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 a signal (Y (BY) (B-B) selected by the selection circuit (21) at a predetermined sampling period.
One of Y) is converted into a digital value and this value is output to the integrator (23). By the way, the timing circuit (25) displays the photographing screen on the basis of 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), and the 8 × 8 screen shown in FIG. 64 rectangular areas (A11), (A12), (A13) ... (A88),
That is, it is divided into (Aij) (i, j = 1 to 8 is an integer), and the switching signal (S2) for extracting the output of the selection circuit (21) in these areas in a time division manner is integrator for each area. (Output to 23.

The integrator (23) receives the switching signal (S2), adds the A / D converted value of the output of the selection circuit (21) over one field period for each region, that is, digitally integrates for every 64 regions, When the integration for one field is completed, the integrated value is held in the memory (26) as the brightness evaluation value or the color evaluation value. As a result, the brightness signal (Y) corresponding to 64 areas in any given field is stored. The digital integrated value is obtained as 64 luminance evaluation values (yij) (i, j: 1 to 8). In the next field, since the color difference signal (RY) is selected by the selection circuit (21), the adder (23)
As a result of integration in each area of, the digital integrated value of each area of the color difference signal (RY) is obtained as 64 color evaluation values (rij). Further, in the next field, the color difference signal (BY) is selected by the selection circuit (21). As a result of the integration of the adder (23), the white integration signal (BY) is digitally integrated for each area. Values are obtained as 64 color evaluation values (bij). Thus, the luminance signal (Y) and the color difference signal (RY)
When the integration of the three fields of (BY) is completed, the 64 × 3 value of the luminance evaluation value (yij) and the color evaluation value (rij (bij) is held in the memory (26). After this,
The same operation as described above is repeated, and the luminance signal (yij) in the next field and the color evaluation value (r
ij) will be updated sequentially.

FIG. 6 shows the internal structure of the integrator (23) in more detail. Each A / D conversion data is supplied to the switching circuit (61). This switching circuit (61) receives the switching signal (S2) and
Adder (F11) (F12) with A / D conversion value prepared for each area
It has a role of supplying to the adder for the area where the sampling point of the relevant data exists in (F88). That is, if the sampling point of certain arbitrary data is included in the area (A11), this data is supplied to the adder (F11) for the area (A11). In the same way, adder (Fij)
(Ij = 1 to 8) are set for the area (Aij), and 64 in total.
Individual adders are provided. A holding circuit (Qij) is arranged 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 added to the data input next. Further, each holding circuit is reset for each field based on the vertical synchronizing signal, and only the held data immediately before this reset is supplied to the memory (26). Therefore, one digital integrator circuit is configured by one set of adder and holding circuit, and a total of 64 integrator circuits constitute the integrator (23), which means that 64 holding circuits are used for each field. The digital integrated value is input to the memory (26) for each of the regions.

When the integration for this one field is completed, this integrated value is held in the memory (26) as a brightness evaluation value or a color evaluation value. As a result, a digital integration value for each area of the luminance signal (Y) corresponding to 64 areas in a given field is obtained as 64 luminance evaluation values (yij). In the next field, the color difference signal (R-
Since Y) is selected, the integrator (the result of the integration of 23,
The digital integrated value of each area of the color difference signal (RY) is obtained as 64 color evaluation values (rij), and similarly, the color evaluation value (bij) of the color difference signal (BY) is obtained in the next field. To be

The reference level, that is, the zero level of the luminance and the color difference signals input to the A / D converter (22) is preset to the level obtained when a perfect achromatic surface is photographed. It goes without saying that the A / D conversion value can be a negative value as well as a positive value.

The latest color evaluation value (yij) (ri
j) (bij) (i, j: 1 to 8) is input to the same color processing circuit (27). This same color processing circuit (27) judges whether or not a plurality of areas which are continuous in the vertical or horizontal direction among 64 areas have the same color, and counts the number of times of the judgment of the same color. The operation is shown in the flowchart of FIG.

In this flowchart, the initial settings for making the determination from the area (A11) in STEP (100) and (101) are performed.
The weighting amount (wij) is initialized in P (102), and the weighting amounts of all areas are set to 1 first. STEP (10
In 4), the difference | rij-ri-1j | of the color evaluation values of the color difference signals (RY) in the area that is continuously arranged in the vertical direction is the reference value (C
It is judged whether it exceeds 1), and similarly, STEP (105)
In (106), the color difference signal (B
-Y) The difference between the color evaluation values | bij-bi-1j | and the difference between the brightness evaluation values | yij-yi-1j | exceed the reference values (C2) and (C3), respectively. Then, when the difference in any evaluation value does not exceed the reference value (C1) (C2) (C3), it is determined that the screens of the two consecutive areas above and below have the same color, and ST
The weight (wij) is halved in EP (107).

The reference values (C1), (C2), and (C3) are thresholds that can be regarded as the same color, and are constants that are set in advance based on experimentally measured values.

STEP (103) does not exist for the upper eight areas arranged on the top of the screen.
It has a function to avoid the judgments of 4) to (106).

In STEP (109), the difference between the color evaluation values of the color difference signal (RY) in the area that is lined up in the left-right direction of the screen | rij-ri
It is determined whether or not j−1 | exceeds a predetermined value (C1). Similarly, in STEP (110) (111), the color evaluation value of the color difference signal (BY) in the area continuous in the left-right direction. Difference | bij−bij−1 | and the luminance evaluation value difference | yij−yij−1 | are reference values (C2),
Determine whether or not (C3) is exceeded. Then, when the difference between the evaluation values does not exceed the reference values (C1) (C2) (C3), it is determined that the screens of the two areas continuous to the left and right have the same color, and STEP (112) The weighting amount is halved. Note that the STEP (108) does not exist on the left side of the eight areas lined up on the left edge of the screen.
It has a function of avoiding the judgments of (109) to (111). To determine whether or not the same series of colors has been determined, see STEP (113).
Is performed for all areas.

The weighting amount (wij) of each area thus determined by the same color processing circuit (27) is input to the screen evaluation circuit (28) and the color difference signal (RY) based on the next colors (1) and (2). (B
-Y) Screen color evaluation value (Vr) for each entire screen
Calculated as (Vb).

The equations (1) and (2) are used to calculate the color evaluation values (ri
j) Means to perform a weighted average of all sums of (bij).

The gain control circuits (29) (30) adjust the gains of the R and B amplification circuits (4) (5) so that the screen color evaluation values (Vr) (Vb), which are the color evaluation values of the entire screen, become zero. Are in control.

(C) Problems to be Solved by the Invention The above-mentioned method is based on the white balance of the color information signal in the area where the variation amount of the color information signal in the imaging screen is less than the reference amount (C1) (C2) (C3). By reducing the contribution to adjustment as compared with other areas, it is intended to cope with a screen including a subject of the same color and a large area.

However, in this method, the reference value for determining the magnitude of the fluctuation amount is fixed, and for example, on the wide-angle side where the focal length of the lens is short, or when the distance to the subject is long, the corner area is Various subjects are likely to enter, and the average evaluation value of each area is less likely to vary. For this reason, even if a plurality of colors are mixed, it is determined that they are the same color, and as a result, the accuracy of white balance adjustment is reduced.

Further, in a region where the absolute value of the evaluation value is large, the amount of change when changing at the same ratio is large, and as a result, it is difficult to determine that the color is the same. However, in reality, the contribution to the control of the white balance adjustment should be made larger in the area closer to the achromatic color where the absolute value of the evaluation value is lower, which causes a decrease in the adjustment accuracy.

(D) Means for Solving the Problems The present invention is for performing white balance adjustment based on color signal information in an image pickup signal, and in a region where the variation amount of the color information signal is below the reference value in the image pickup screen. In reducing the contribution of the color information signal to the white balance adjustment from other areas, the reference amount can be changed according to the focal length of the lens, the distance to the subject, and the absolute value of the color signal information, or The feature is that the amount of contribution reduction is changed.

(E) Operation Since the present invention is configured as described above, it is possible to always accurately and accurately reduce the influence of a subject having the same color and a large area in various shooting situations.

(F) Example An example of the present invention will be described with reference to the drawings.

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

 It should be noted that the description of the parts common to the conventional example will be omitted.

Reference numeral (40) is a well-known zoom mechanism used in general video cameras. By displacing the zoom lens that constitutes this zoom mechanism, the focal length of the entire lens system of the camera is changed to zoom from wide-angle to telephoto. It is possible to select a desired state from the area.

A 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) basically functions to reduce the weighting amount of the corresponding area when the areas of the same color continuously exist as in FIG. 2, but based on the lens focal length information. A reference value changing routine (200) for changing the reference values (C1) (C2) (C3) used in determining the weighting amount is added as shown in the flowchart of FIG.

The reference value change routine (200) is as shown in FIG.
As in STEP (201), it is determined whether the focal length (f) is shorter than the preset reference focal length (f ₀ ), that is, it is on the wide-angle side. If it is on the wide-angle side, STEP ( In 202), the reference values (C1), (C2), and (C3) are all halved, and conversely, they are longer than the reference focal length (f ₀ ), that is, the reference values (C1) (C2) (C3 ) Is maintained as is. Based on the reference value thus obtained, the same operation as in the conventional example is performed. Therefore, when a wide angle is used in which various subjects are less likely to enter and color bias is more likely to occur in each area than in the telephoto mode where a specific subject occupies a large area on the screen and biases in specific colors are likely to occur Therefore, STEP (104)
In the determination operation of the same color in steps (106) to (109) to (111), it is difficult to determine the same color unless the variation amount is significantly small, and it is possible to prevent an incorrect determination of the same color.

FIG. 9 is a circuit block diagram of the second embodiment.
In this figure, (42) is a well-known focus mechanism that measures the distance to a subject using infrared rays and the like, and moves the lens (1) forward and backward in the optical axis direction according to the subject distance to bring the lens into focus. , Subject distance (L) obtained by the focus mechanism
Information is input to the same color processing circuit (67) and used for the same color determination.

The same color processing circuit (67) basically performs the same operation as in the flow chart of FIG. 7 as in the first embodiment. However, the reference value changing routine (200 ') changes the reference values (C1) (C2) (C3) used in determining the weighting amount based on the subject distance as shown in FIG. That is, when the subject is at a distant position, the actual area of the subject that enters each area of the screen becomes large, and since various subjects enter the area, the difference in color and luminance signals between the areas tends to be small. In consideration of this, in STEP (210), it is determined whether or not the subject distance (L) is greater than the preset reference subject distance (L ₀ ), and it is determined that the subject distance (L) is far, When it does, the standard value (C1) (C2) in STEP (211)
(C3) is 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, if the evaluation values do not change extremely greatly, the same color No more judgment is made, and erroneous same color judgment is prevented.

In this embodiment, the distance measuring method using infrared rays as the focus mechanism is shown, but the present invention is not limited to this. For example, a method of moving the lens back and forth so that the high frequency component of the luminance signal can be taken out most It may be used, and in this case, the subject distance may correspond to the position of the focus lens with respect to the CCD.

Further, FIG. 11 is a flowchart of the third embodiment,
The difference from FIG. 5 is that STEP (300) (301) is added. That is, a reference value (C1) that is a constant value in advance
This is to calculate from the absolute value of each evaluation value without setting (C2) and (C3). Specifically, in STEP (300) (301), 1/8 of the evaluation value at that time is calculated. Use as the reference value for the area.
That is, C1 = rij / 8, C2 = bij / 8, C3 = yij / 8. As a result, the area where the evaluation value changes at a certain ratio or more,
The same color region is not considered, and as a result, the absolute value of each evaluation value is prevented from affecting the same color determination.

Further, FIG. 12 is a flow chart of the fourth embodiment.
The difference from Fig. 11 is that instead of STEP (107) (112), STEP
(400) and (401) are added. That is, the weighting reduction amount is variable according to the deviation of the color evaluation value from the absolute value. Here, as the magnitude of the color evaluation value, the square root of the sum of squares of each color evaluation value (rij) (bij), that is, the distance from white on the color plane is used.

In STEP (400) (401), wij = wij / a (4) (where R is a constant preset based on an actual measurement value) is calculated. This is due to STEP (104) to (106) and
For areas determined to be the same color in STEPs (109) to (111), the degree of separation from the achromatic color of the same color is obtained as a in equation (3), and weighted in equation (4). The amount (wij) is inversely proportional to a, and the weighting amount of a highly saturated region far from white is greatly reduced to prevent the contribution of the low-saturation portion close to white from dropping. Needless to say, if the value of a is equal to or smaller than a certain value, it is possible not to reduce the contribution.

As mentioned above, the focal length of the lens, the distance to the subject,
By varying the reference amount or changing the contribution reduction amount according to the absolute value of the color signal information, it is possible to more appropriately select and process an effective region for white balance adjustment. Like

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) by software using a microcomputer, and considering that this processing itself contains ambiguity. Control using fuzzy reasoning is also possible.

(G) Effect of the Invention As described above, according to the present invention, the deviation of the white balance can be suppressed to the maximum upper limit for various screens including the same color and a large area of the subject.

[Brief description of drawings]

FIG. 1 is a circuit block diagram of the first embodiment of the present invention, FIGS. 7 and 8 are the same flow charts, FIG. 9 is a circuit block diagram of the second embodiment, FIG. 10 is the same flow chart, and FIG. Is a flowchart of the third embodiment, and FIG. 12 is a flowchart of the fourth embodiment. Further, FIG. 2 is a circuit block diagram of a conventional example, FIGS. 3, 6, and 5 are circuit block diagrams and flowcharts of prior art, and FIG. 4 is an explanatory diagram of screen division. (4) …… R amplifier circuit, (5) …… B amplifier circuit, (57)
(67) …… Same color processing circuit, (28) …… Screen evaluation circuit.

Claims (7)

[Claims] 1. A white balance adjusting device for performing white balance adjustment for controlling the gain of each color signal based on a color information signal in a picked-up image signal, wherein the fluctuation amount of the white information signal in an image pickup screen is below a reference value. A white balance adjusting device characterized in that contribution of a color information signal in an area to white balance adjustment is reduced as compared with other areas, and the reference value is made variable according to a focal length of a lens. 2. The white balance adjusting apparatus according to claim 1, wherein the reference value is reduced as the focal length becomes shorter. 3. A white balance adjusting device for performing white balance adjustment for controlling the gain of each color signal on the basis of a color information signal in a picked-up video signal, wherein a variation amount of the color information signal within an image pickup screen is below a reference value. A white balance adjusting apparatus, wherein contribution of a color information signal in an area to white balance adjustment is reduced as compared with other areas, and the reference value is variable according to a distance to a subject. 4. The white balance adjusting apparatus according to claim 3, wherein the reference value is reduced as the distance to the subject becomes longer. 5. A white balance adjusting device for performing white balance adjustment for controlling the gain of each color signal based on a color information signal in a picked-up image signal, wherein the variation amount of the color information signal within an image pickup screen is below a reference value. A white balance adjusting device, wherein contribution of a color information signal in an area to white balance adjustment is reduced as compared with other areas, and the reference value is variable according to an absolute value of the color information signal. 6. The white balance adjusting apparatus according to claim 5, wherein the reference value is increased as the absolute value of the color information signal increases. 7. Color information in an area in which white balance adjustment for controlling the gain of each color signal is performed based on the color information signal in the picked-up image signal and the variation amount of the color information signal is below a reference value in the picked-up screen. A white balance adjusting apparatus for reducing the contribution of a signal to white balance adjustment from other areas, wherein the reduction amount of the reducing operation is reduced in an area where a color information signal is close to an achromatic color. .