JPH03250992A - White balance adjustment device - Google Patents

Abstract

PURPOSE:To avoid a disadvantage of white balance from being deviated to a complementary color side as to the entire pattern by limiting the degree of contribution in the white balance adjustment when an object with high saturation exists in the pattern. CONSTITUTION:R, B signals in three primary color signals are inputted to a camera process and matrix 6 via R, B amplifier circuits 4, 5 respectively together with the G signal, color difference signals R-Y, B-Y are generated and fed to a selection circuit 21. When the integration of two fields of the color difference signals R-Y, B-Y is finished by the selection circuit 21 and an integration device 23 by using a selection signal from a timing circuit 25, a color evaluation value is stored in a memory 26. A color evaluation value adjustment circuit 27 when an object with extremely high saturation exists in the pattern adjusts the color evaluation so as to reduce the effect onto the white balance adjustment over the entire pattern. Based on the color evaluation subject to adjustment and processing, a pattern evaluation circuit 28 calculates the pattern color evaluation being the entire color evaluation of the pattern and gain control circuits 29, 30 control the gain of the amplifier circuits 4, 5 so as to make the pattern color evaluation zero.

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 an automatic white balance adjustment device for a color video camera that controls white balance.

(B) Conventional Technology In a color video camera, it is necessary to control the white balance in order to correct for differences in the wavelength distribution of light depending on 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. In general, 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. 6 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) converts R, G, and B.
are extracted as three primary color signals, and the G color signal is directly extracted as the R color signal.
and B color signals are sent to the R amplification circuit (4) and the B amplification circuit (5).
The luminance signal Y and the red and blue color difference signals R- are input to the camera process and matrix circuit (6).
Y, B-Y are created and sent to the video circuit.

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

(c) Problems to be solved by the invention The above-mentioned method is based on the empirical rule that when photographing a general subject, the value obtained by averaging the color difference signals of the entire screen is equivalent to that when photographing a completely white surface. It is said that Therefore,
If a subject with extremely high saturation is included in the screen and the average of the screen does not become achromatic due to the influence of this saturation, the gain will change in the direction of canceling out the highly saturated colors and the white balance will change. It has the disadvantage that it shifts to the complementary color side, making it impossible to reproduce colors appropriately.

(D) Means for Solving the Problems The present invention includes an amplification means for adjusting the gain of a color signal obtained from an image sensor, and a gain control means for controlling the gain of the amplification means based on a color difference signal related to each color signal. The white balance adjustment device is characterized in that when the level of each color difference signal is outside a predetermined range, the degree of contribution of the color difference signal to gain control is limited or input to the gain control means is cut off.

(E) Effect Since the present invention is configured as described above, when a highly saturated object exists in the screen, by limiting the degree of contribution in the white balance adjustment operation, the white balance for the entire screen is adjusted to the side of the complementary color of the object. The inconvenience of shifting is suppressed.

(f) Example 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 mill balance adjustment circuit according to this embodiment.

The light that has passed through the lens (1) is imaged on a CCD (2), photoelectrically converted, and then separated into R, G by a color separation circuit (3).
, B are extracted as three primary color signals. The R and B signals among these three primary color signals are sent to the R and B amplifier circuits (4), respectively.
(5), it is input to the camera process and matrix (6) together with the G signal, and based on these, the luminance signal (Y) and the red and front color difference signals (R-Y) and (B-Y) are created. The video signal is then supplied to a video circuit (7) and subjected to well-known processing. Further, both the (RY) and (B-Y) signals are also supplied to the selection circuit (21) at the same time.

The selection circuit (21) sequentially selects one of the two color difference signals (R-Y) and (B-Y) for each field based on the selection signal (Sl) from the timing circuit (25). , (RY) → (B-Y) → (RY) →... and 1
Each field is output from the subsequent A/D converter (zz)i''.The selection signal (Sl) is created based on the vertical synchronization signal obtained from the synchronization separation circuit (24) as described later.

A/D conversion! (22) is the signal (RY) (B-Y) selected by the selection circuit (21) at a predetermined sampling period.
) is sampled and converted into a digital value, and this value is output to the integrator (23). By the way, the timing circuit (25) adjusts the imaging screen to 8x as shown in FIG.
8, 64 rectangular areas of the same area (All), (A
12), (A13)... and outputs a switching signal (S2) to the integrator (23) for time-divisionally extracting the output of the selection circuit (21) within these regions for each region.

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, adds each color difference signal for each of the 64 regions. is digitally integrated, and when the integration for one field is completed, this integrated value is held in the memory (26) as a color evaluation value. As a result, the digital integral value for each region of the color difference signal (R-Y) corresponding to 64 regions in a certain arbitrary field is 64 color evaluation values (ri]) (i=1-8
, co=1-8). Furthermore, in the next field, the color difference signal (B-Y) is selected by the selection circuit (21), so as a result of the integration of the adder (23), the color difference signal (B-Y) is selected by the selection circuit (21).
The digital integral value for each region of B-Y) is obtained as 64 color evaluation values (bij). In this way, the color difference signal (R
-Y)(B-Y), the color evaluation values bij)(bij) are held in the memory (26). After this, the same operation as described above is repeated, and the color evaluation value (rij) is updated in the next field, and the color evaluation value (bij) is updated in the next field.

Figure 1 shows the internal structure of this integrator (23) in more detail. The A/D converted value of each sampling data is supplied to a switching circuit (61). This switching circuit (61) receives the switching circuit (S2) and adds each A/D conversion value to an adder (PI 1 ) (PI2) prepared for each area (P88
) has the role of supplying data to the adder for the region where the corresponding sampling point exists. That is, if a sampling point of a certain arbitrary sampling data is included in the area (A11), this data is supplied to the adder (pH) for the area (All). Note that, in the following, the adder (Pi
j) (i, j=1-8) is the area (Aij)(i, j
= 1 to 8), and a total of 64 adders are provided. A holding circuit (Qi]) is provided after each adder.
(i, j=1-8) are provided, and each added value is temporarily held in each holding circuit. The data held by each holding circuit is again input to the adder and added to the next sampling data. Further, each holding circuit is reset for each field in synchronization with the vertical synchronization signal, and only the data held immediately before this reset is supplied to the memory (26). Therefore,
One set of adder and holding circuit constitutes one digital integration circuit, and a total of 64 integration circuits constitute an integrator (23).
The digital integral value of each color difference signal is input to the memory (26) for each of the 64 areas from each holding circuit for each field.

When the integration for one field is completed, the integrated value for each area is held in the memory (26) as a color evaluation value. As a result, the selection circuit (21)
Since the color difference signal (R-Y) is selected at , the color difference signal (R-Y) is selected as a result of integration in each region of the integrator (23).
The digital integral value for each region of Y) is 64 color evaluation values (
rij). Furthermore, in the next field, the color difference signal (B-Y) is selected by the selection circuit (21), so as a result of the integration by the integrator (23), the color difference signal (B-Y) is selected by the selection circuit (21).
) is the digital integral value for each region of 64 color evaluation values (b
ij). In this way, the color difference signal (R-Y)
When the integration of the two fields (B-Y) is completed, the 64 x 2 values of color evaluation values (riD and (biD) are stored in the memory (
26). From this point on, the same operation as above is repeated, and in the next field, the color evaluation value (r
ij), but in the next field, the color evaluation fi1m
(bij) will be updated sequentially. The latest color evaluation values (rii) (bij) obtained in this manner are supplied to the subsequent color evaluation value adjustment circuit (27).

Note that the color difference signal (R-
The reference level or zero level of Y) and (B-Y) is set in advance to a value at which a completely white achromatic screen is obtained, and therefore the individual A/
The D-conversion data includes not only positive values but also negative values, and when a completely white surface is photographed, the sum of all 64 areas of each color evaluation value becomes zero.

The color evaluation value adjustment circuit (27) uses the color evaluation value to determine whether or not there is an extremely highly saturated object in the screen, and if there is a highly saturated object, the color evaluation value of this object is adjusted. It has the function of reducing the influence of white balance adjustment on the entire screen, and specifically adjusts the color evaluation value according to the flowchart shown in FIG.

In this flowchart, S T E P (50
) to (54), the absolute value 1r of the color evaluation value (riJ)
The color evaluation value (riJ) is adjusted depending on whether ijl is less than or equal to the R threshold (dr), and S T E P (
50), the color evaluation value (riJ) of a certain area is equal to the R threshold (d
r), it is assumed that there is an object with high saturation of the red component in this area, and the color evaluation value of this area is changed to a new color evaluation value (r'iJ) in 5TEP (51). This color evaluation value (r'iD) and the color evaluation value (rij) before change are r'13=2dr-r ij
−−−■ There is a relationship.

In addition, in S T E P (52), it is assumed that a highly saturated subject exists even when the color evaluation value (rij) of a certain area is smaller than -dr, and in S T E P (54),
The color evaluation value (rij) is r'+ 3 = -2dr-r ij
・－－New color evaluation value (
r'ij).

Furthermore, in S T E P (50) (52) -dr≦r
When it is determined that ij≦dr, r'x3=rij .

Similarly, in S T E P (55) to (59),
The absolute value 1bijl of the color evaluation value (bij) is the B threshold (db
) or less, the color evaluation value (bij) is changed depending on whether or not, and when b1co>db, b'1j=2db
-bij... ■-db≦biko≦(When lb, b'1j=bij... ■When bij<-db, b'ij =-2db-bij... ■Depending on each condition, The color evaluation value (bij) is newly changed to the color evaluation value (
b'ij).

Here, the color evaluation value adjustment circuit (27)
Take the color evaluation values (rij) and (bii) input to
When shown on the coordinate axis with changed color evaluation value (r'1j) (b'iD) on the vertical axis, it becomes as shown in FIG. If the value is extremely large and there is an extremely highly saturated object in the area, it is monotonically decreased to reduce the influence of the color evaluation value of the area on white balance adjustment for the entire screen.

Similarly, when each color evaluation value is extremely small and there is an extremely highly saturated subject in the area, as in equation (3), ■,
By monotonically decreasing, the degree of influence of the color evaluation value of the corresponding area on white balance adjustment for the entire screen is reduced.

In S T E P (60), the color evaluation value adjustment process in accordance with each of the above-mentioned conditions is sequentially executed for each of the 64 regions.

Note that both the R threshold (dr) and the B threshold (db) are −
These values are expected to have a negative effect on white balance adjustment for each color unless the conditions dr≦rij≦dr and -db≦bij≦clb are satisfied, and are set in advance based on actually measured values.

The color evaluation ffL(r'ij)(
b'jj ) is sent to the screen evaluation circuit (28) and is calculated by the following equation (7
)(8), the color evaluation value of the entire screen of each color difference signal is calculated as the screen color evaluation value (Vr) (Vb).

i=1 j4 iJ )=1 Equations (7) and (8) are the sum of all the color evaluation values (r'1i) (b'ij) of each of the 64 areas that have passed through the color evaluation value adjustment circuit (27). is divided by the number of areas, and the average value for one area is calculated as the screen color evaluation value.

The gain control circuits (29) and (30) control the R and B amplifier circuits (4) and (5), respectively, so that the screen color evaluation values (Vr) (Vb), which are the color evaluation values of the entire screen, are both zero. The gain is controlled. When the screen color evaluation values (Vr) (Vb) become zero in this way, it means that the white balance adjustment is completed.

By the way, in this embodiment, in order to share the A/D converter (22), the selection circuit (21) selects the color difference signal (R-Y).
, (B-Y), the update cycle of the evaluation value of each component was 2 fields.
By placing two A/D converters and integrators for (RY) and (B-Y), each evaluation value can be updated for each field, allowing even more precise mill balance adjustment. It becomes possible.

In addition, in this embodiment, adjustment processing was performed using the function as shown in Fig. 4, but instead, for example, the color evaluation value of a highly saturated area as shown in Fig. 5 (a) is invalidated, that is, replaced with 0. or
As shown in FIG. 5(b), an equal product function can be considered that is fixed to a constant value and clipped.

Furthermore, in this embodiment, it is determined whether each color difference is outside the range or not, but the sum of squares of both color differences, that is, (rij+bij)
There is also a method of setting a range for and limiting the degree of contribution.

It is also conceivable to correct the amplification in the amplifier circuits (4) and (5), calculate a color difference signal for the original signal, and use this for discrimination.

Further, in this embodiment, the color evaluation value itself was directly corrected based on the adjustment processing in the color evaluation value adjustment circuit (27), but instead of this, it is usual to add a certain weight to the color evaluation value. (Dp
), for example, rljxDp), but it is also possible to obtain the same effect by reducing the amount of weighting for highly saturated color evaluation values.

(G) Effects of the Invention As described above, according to the present invention, even when a highly saturated object exists in the screen, the contribution of the high chroma component of this object can be reduced in screen evaluation for executing white balance adjustment. This makes it possible to suppress the shift of high chroma components toward the complementary color side in white balance adjustment.

3 is an explanatory diagram of area division, FIG. 4 is an explanatory diagram of an adjustment function, and FIG. 5 is an explanatory diagram of other adjustment functions. Further, FIG. 6 is a circuit block diagram of a conventional example.

Claims (2)

[Claims] (1) In a white balance adjustment device having an amplification means for adjusting the gain of a color signal obtained from an image sensor, and a gain control means for controlling the gain of the amplification means based on a color difference signal related to each color signal, each color difference signal level A white balance adjustment device, characterized in that the degree of contribution of the color difference signal to the gain control is limited when the color difference signal is outside a predetermined range. (2) In a white balance adjustment device having an amplification means for adjusting the gain of a color signal obtained from an image sensor, and a gain control means for inputting a color difference signal related to each color signal and controlling the gain of the amplification means, each color difference signal level A white balance adjustment device, characterized in that when the color difference signal is outside a predetermined range, input of the color difference signal to the gain control circuit is cut off.