JP2523033B2 - White balance adjustment device - Google Patents

Description

TECHNICAL FIELD The present invention relates to an automatic white balance adjusting device for a color video camera, which controls white balance based on an imaged video signal obtained from an image pickup device.

(B) Conventional Technology In a color video camera, it is necessary to control 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.

Figure 5 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), R,
The three primary color signals of G and B are extracted, and the G color signal is directly input to the camera process and the matrix circuit (6) via the R amplification circuit (4) and the B amplification circuit (5). The luminance signal Y, the color difference signals RY and BY for red and blue, respectively, are created and sent to the video circuit.

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) are integrated for a sufficiently long time so that the result becomes zero. Adjust the gain.

(C) Problem to be Solved by the Invention The above-mentioned method is based on the empirical rule that, when a general subject is photographed, the averaged color difference signals of the entire screen are equivalent to those when a perfect white surface is photographed. Therefore, it is necessary for the shooting screen to include each color on average.

Therefore, when there is a color deviation in the entire screen, the gain changes in the direction of canceling the color, and there is a drawback that proper color reproduction cannot be performed. For example, when shooting outdoors, a blue sky often appears on the upper side of the screen, and as a result, the white balance shifts to the complementary side of blue.

(D) Means for Solving the Problems The present invention provides a white balance adjustment for a color information signal in a predetermined area when the color information signal level and the brightness level in the predetermined area of the imaging screen are equal to or higher than a predetermined level. It is characterized by reducing the contribution degree from other areas, and more specifically, a color evaluation value detection for obtaining a color information signal level as a color evaluation value of each color for each of a plurality of areas set by dividing an imaging screen. Means, a brightness evaluation value detection means for obtaining the brightness level of each area as a brightness evaluation value, and a color of the selected area only when the color evaluation value and the brightness evaluation value in the selected area selected from all areas are larger than the reference value. Color evaluation value adjusting means for adjusting the color evaluation value by reducing the evaluation value by a predetermined amount or reducing the weighting amount compared to other areas, and the color evaluation value for the entire screen from the color evaluation values of all areas after the color evaluation value adjustment. Screen color rating A screen color evaluation value calculation means for calculating the value and a gain control means for controlling the amplification gain of each color signal based on the screen color evaluation value are provided.

(E) Action Since the present invention is configured as described above, it is possible to minimize the deviation of the white balance to the complementary color side of this color in the situation where a subject of the same color exists in a predetermined area. Becomes

(F) Embodiment One 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 according to this embodiment.

The light passing through the lens (1) is imaged on the CCD (2) and photoelectrically converted, and then R,
It is taken out as three primary color signals of G and B. The R and B signals of these three primary color signals are input to the camera process and matrix (6) together with the G signal through the R and B amplifier circuits (4) and (5), respectively, and the luminance signal (Y ), Red and blue color difference signals (RY), (B-
Y) is created, supplied to the video circuit (7), and subjected to well-known processing. In addition, (Y) (RY) (BY)
The respective signals are also 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. (Y) → (RY) → (BY
Y) → (Y) → (RY) → ... Is output to the A / D transmission (22) at the subsequent stage for each field. 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 transmission (22) has a signal (Y) (RY) (B-) selected by the selection circuit (21) at a predetermined sampling cycle.
One of Y) is finely sampled and sequentially converted into a digital value, and this value is output to the integrator (23). By the way, the timing circuit (25) is a vertical and horizontal synchronizing signal from the camera process and matrix circuit (6) and CCD.
Based on the fixed oscillator output that drives (2), the imaging screen is divided into 8 × 8 rectangular areas (A11), (A12), (A13) ... Of 64 shown in FIG. For each area, a switching signal (S2) for extracting the output of the selection circuit (21) in these areas by its own division is output to the integrator (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, and finally, selects the selection circuit (for each of the 64 regions) ( 2
Digitally integrates the signal selected in 1).

FIG. 3 shows the internal structure of the integrator (23) in more detail. The A / D converted value of each sampling data is supplied to the switching circuit (61). The switching circuit (61) receives the switching signal (S2), and the corresponding sampling point exists in the adders (P11) (P12) ... (P88) prepared for each A / D conversion value for each area. It has a role of supplying the adder for the area.
That is, if the sampling point of a certain arbitrary sampling data is included in the area (A11, this data is supplied to the adder (P11) for the area (A11).
Similarly, the adder (Aij) (i, j = 1 to 8) is the area (Pij)
It is set for (i, j = 1 to 8), and a total of 64 adders are prepared. The holding circuit (Qi
j) (i, j = 1 to 8) are respectively arranged, and each added value is temporarily held in each holding circuit. The data held in each holding circuit is input again to the adder and added to the next sampling data. Further, each holding circuit is reset for each field in synchronization with 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 in one set of adder and holding circuit, and a total of 64 integrator circuits configure the integrator (23), and each holding circuit is configured for each field.
The digital integrated value is input to the memory (26) for each of the 64 areas.

When the integration for this field is completed, the integrated value for each area is held in the memory (26) as a brightness evaluation value or a color evaluation value. As a result, digital integration values of the luminance signal (Y) corresponding to 64 areas in a given field are 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 result of integration in each area of the integrator (23) results in each area of the color difference signal (RY). The digital integrated value of is 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), the color difference signal (B-Y) is obtained as a result of integration by the integrator (23).
Y) the digital integrated value for each area is 64 color evaluation values (bi
obtained as j). Thus, when the integration of the three fields of the luminance signal (Y) and the color difference signals (RY) (BY) is completed, the luminance evaluation value (yij) and the color evaluation value (rij)
The 64 × 3 values of (bij) are 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 value (rij) (bij) thus obtained are supplied to the color evaluation value adjusting circuit (27) in the subsequent stage. The color evaluation value adjustment circuit (27) determines whether or not there is a certain level of brightness level in a preselected specific area among the 64 areas and whether or not there is an object of a certain specific color. In this case, the color evaluation value level of the corresponding area is reduced by a predetermined amount (P), and specifically, it is configured as shown in FIG.

By the way, generally, in outdoor photography, there is a very high probability that a blue sky exists on the upper side of the imaging screen, and when the entire screen is taken into consideration, there is a high risk of a screen biased toward the blue component. Therefore, in the color evaluation value adjustment circuit (27), the specific area
FIG. 4 will be described by selecting 16 areas and selecting blue as a specific color.

Note that the blue sky will be described in consideration of being a subject having a relatively high luminance level and a very high color difference signal (BY).

In FIG. 4, the brightness evaluation value (yij) of each area
Are in the order of the regions, that is, (y ₁₁ ) → (y ₁₂ ) → …… (y ₁₈ ) → (y
₂₁ ) → ... → (y ₈₈ ) are input in this order to the brightness comparator (62) and compared with the brightness threshold value (Ny) stored in advance in the brightness threshold value memory (63). Where the brightness comparator (62)
The comparison operation by is executed only when the brightness evaluation value of the area selected by the area selection circuit (64) is input.
In the present embodiment, attention is focused on the blue sky as a subject of the same color, and the areas selected by the area selection circuit (64) are 16 areas (A11) (A12) ... (A28) at the top of the imaging screen. ), The comparison operation by the brightness comparator (62) is actually executed only for the brightness evaluation values of the above 16 areas. When it is determined that the brightness evaluation value is larger than the brightness threshold value (Ny) as a result of the comparison operation described above, the H level comparison signal (S3) is issued for the corresponding region.

The color comparator (65) compares the level of the color evaluation value (bij) with the B threshold value (Nb) stored in the color threshold value memory (66) only while the comparison signal (S3) is at the H level. It is a thing. Therefore, by the comparison by the brightness comparator (62), only the color evaluation value (bij) of the area where the brightness evaluation value is judged to be larger than the brightness threshold value (Ny) is compared with the B threshold value (Nb). . As a result of this comparison operation, only when the color evaluation value (bij) is larger than the B threshold value (Nb), the H level comparison signal (S4) is issued for the corresponding region.

The switching signal circuit (66) is composed of two switches (67) and (68), and the switch (67) is connected to a fixed contact (67a) to which the color evaluation value (bij) is input and a B attenuator (69). Fixed contact (67b) or fixed contact (67c) coupled to the output terminal (71) is selectively connected,
The switch (68) has a fixed contact (68a) to which the color evaluation value (rij) is input and a fixed contact (6) connected to the R attenuator (70).
8b) or fixed contact (68) coupled to the output terminal (72)
It has a function to selectively connect c).

Both switches (67) and (68) are interlocked and controlled by a comparison signal (S4) as a switching signal, and when the comparison signal (S4) is at L level, they are on the fixed contact (67c) (68c) side, respectively. The color evaluation values (bij) (rij) in the area are output to the output terminals (71) (72) as they are without any attenuation, and switch to the fixed contacts (67b) (68b) side at H level, Color evaluation values (bij) (rij) are input to the B and R attenuators (69) (70) in the corresponding area.

The B and R attenuators (69) (70) subtract a preset predetermined amount (Z) from the input color evaluation values (bij) (rij) to obtain (bij-Z), (rij-Z). And calculate the output terminal (7
1) Derived to (72).

Therefore, the preselected areas (A11) (A12) ... (A2
Regarding each of 8) (i) Luminance evaluation value (yij) (i = 1, 2, j = 1 to 8)
Is above the brightness threshold (Ny).

(Ii) The blue component is remarkably large so that the color evaluation value (bij) (i = 1, 2, j = 1 to 8) exceeds the B threshold value (Nb).

It is judged whether or not the two conditions are satisfied at the same time, and the function of attenuating the color evaluation values (bij) (rij) of the satisfied area by a predetermined amount (Z) is adjusted by the color evaluation value adjustment circuit (27). It can be said to work.

The luminance and the color evaluation values (yij) (bij) (rij) input from the memory (26) to the color evaluation value adjustment circuit (27) are both input in synchronization with each other in the same area, and accordingly, adjustment is performed. The processing in the circuit is also sequentially executed for all 64 areas.

Further, both the brightness threshold value (Ny) and the B threshold value (Nb) are set by actual measurement data that can be recognized as blue sky, and similarly, the attenuation amount (Z) is actually the blue sky in the selected area of the areas (A11) ... (A28). It is set by the actual measurement value when the optimum white balance can be realized in the shooting state in which there is.

The non-attenuated or attenuated color evaluation values that are derived from the output terminals (50) (51) are sent to the screen evaluation circuit (28) and based on the following equations (1) and (2), the entire screen of each color difference signal is displayed. The color evaluation value of is calculated as the screen color evaluation value (Vr) (Vb).

The formulas (1) and (2) are passed through the color evaluation value adjusting circuit (27).
The sum total of all 64 color evaluation values (rij) (bij) of each area is divided by the number of areas to calculate an average value for one area as a screen color evaluation value.

The gain control circuits (29) and (30) set P so that the screen color evaluation values (Vr) (Vb), which are the color evaluation values of the entire screen, become zero.
And the gains of the B amplifier circuits (4) and (5) are controlled. In this way, if the screen color evaluation value (Vr) (Vb) becomes zero,
White balance adjustment is complete.

As described above, in the present embodiment, by setting the specific area to the upper side of the screen and the specific color to blue, even if the blue sky exists on the imaging screen, the influence of the blue sky on the white balance adjustment of blue is suppressed. Although the entire screen is prevented from being biased toward the complementary color side of blue, the specific area or color can be freely selected.For example, the specific area is held on the upper side of the screen and the specific color is selected as red. By inputting (rij) instead of the color evaluation value (bij) into the comparator, it is possible to suppress the influence on the red white balance adjustment of the sunset instead of the blue sky and prevent the bias of the red toward the complementary color side. In this embodiment, as a specific example of the color evaluation value adjustment operation in the color evaluation value adjustment circuit (27), a method of subtracting a predetermined attenuation amount (Z) from the color evaluation values (rij) (bij) is adopted. As another method, there is a method of changing the weighting amount as shown in FIG. That is, in the area where the comparison signal (S4) is at the L level, the weighting circuits (101) (103) apply a predetermined weighting amount (D) to each color evaluation value.
1) Weighting, that is, multiplication of rij × D1 or bij × D1, and for the area where the comparison signal (S4) becomes H level, the weighting circuit (100) (102) weights the amount (D1).
By weighting with a smaller weighting amount (D2) and outputting this multiplied value as the adjusted color evaluation value of each area, the contribution of the area of yij> Ny and bij> Nb to the entire screen is substantially achieved. You can reduce the degree.

It is needless to say that if the user can freely select the specific area and the specific color with the operation button, the white balance can be properly adjusted under various shooting situations.

In addition, in the present embodiment, since the A / D converter (22) is shared, the selection circuit (21) uses the luminance or color difference signal (Y),
Since it is configured to select one of (RY) and (BY), the period for updating the evaluation value of each component is 3 fields, but (Y), (RY), 3 A / for (BY)
If a D converter and an integrator are provided, each evaluation value can be updated for each field, and white balance adjustment can be performed with higher accuracy.

(G) Effect of the Invention As described above, according to the present invention, in a situation where a subject of a predetermined color exists in a predetermined region, this subject does not need to contribute to white balance adjustment in advance. Considering that, it is possible to suppress the deviation of the white balance from the specific color to the complementary color side.

[Brief description of drawings]

1 to 5 relate to an embodiment of the present invention, FIG. 1 is an overall circuit block diagram, FIG. 2 is an explanatory diagram of area division, and FIG.
FIG. 4 and FIG. 4 are main circuit block diagrams, FIG. 5 is a main circuit block diagram of another embodiment, and FIG. 6 is an explanatory view of a conventional example. (27) …… Color evaluation value adjustment circuit, (28) …… Screen evaluation circuit, (23) …… Integrator, (29) (30) …… Gain control circuit.

Claims (3)

(57) [Claims] 1. A white balance adjusting device for performing white balance adjustment based on color information in a picked-up video signal, when a specific color information signal level and a brightness level in a predetermined area of a screen are equal to or higher than a predetermined level, the area is adjusted. A white balance adjusting apparatus which reduces the contribution of the color information signal to the white balance adjustment in other areas than in other areas. 2. A color evaluation value detecting means for obtaining a color information signal level as a color evaluation value of each color for each of a plurality of areas set by dividing an image pickup screen, and a brightness level of each area as a brightness evaluation value. Brightness evaluation value detection means, only when the color evaluation value and the brightness evaluation value of a specific color in the selected area selected from the areas are larger than a reference value, a color evaluation that reduces the color evaluation value of the selected area by a predetermined amount. A color evaluation value adjusting means for performing value adjustment; a screen color evaluation value calculating means for calculating a color evaluation value for the entire screen as a screen color evaluation value from the color evaluation values of all areas after the color evaluation value adjustment; A white balance adjusting device comprising a gain control means for controlling an amplification gain of each color signal based on a color evaluation value. 3. A color evaluation value detecting means for obtaining a color information signal level as a color evaluation value of each color for each of a plurality of areas set by dividing an image pickup screen, and a brightness level of each area as a brightness evaluation value. Brightness evaluation value detection means, a screen color evaluation value that calculates a color evaluation value for the entire screen as a screen color evaluation value from the color evaluation values of all areas after weighting the color evaluation value with a predetermined weighting amount. The calculation means and the gain control means for controlling the amplification gain of each color signal based on the screen color evaluation value are provided, and the color evaluation value and the brightness evaluation value of a specific color are selected in the selected area from all areas. A white balance adjusting apparatus, wherein the weighting amount is reduced for an area larger than a reference value.