JPS63283293A - White balance adjusting device - Google Patents

Abstract

PURPOSE:To utilize the information of a color measuring sensor even at the time of low illuminance and to suppress the influence of an error by providing the titled device with a means for restricting the output range of control voltage for an image pickup signal amplifier means and a detecting means for detecting the quantity of peripheral light and validating the restriction range of the control voltage based on a detected output. CONSTITUTION:Signals log(SR/SG), log(SG/SB) outputted from a differential circuit 3 and a signal log SG outputted from a logarithm compressing circuit 2 are digitized in a microcomputer 4 and read in as X, Y and L. A value Lth1 stored in a memory 9 as the lower limit reference value of brightness is compared with the value L. The value L is in direct proportion to the logarithm of a peripheral light quantity value. In case of L>Lth1, the value L is compares with the upper limit reference value Lth2. In case of L>Lth1 and L>Lth2, in case of L>Lth1 and L<Lth2 and in case of L<Lth1, the control voltages of an R signal amplifier 6 and a B signal amplifier 7 are controlled in accordance with said respective cases. Since the restriction range of the control voltages of red and blue amplifiers are narrowed when the illuminance of peripheral light is low, the information of the color measuring sensor 1 can be utilized even if the control voltage exceeds a fixed level at the time of low illuminance, the white balance can be prevented from being suddenly and sharply unbalanced and the influence of an error in the color measuring sensor can be reduced.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a white balance adjustment device in a color imaging device.

[Conventional Technique*] Conventionally, an automatic tracking type device that measures color using an external sensor has been known as a white balance adjustment device for a color imaging device.

Figure 3 is a block diagram showing a conventional white balance adjustment system, where l is a colorimetric sensor that detects red, green, and blue components of light source light and performs photoelectric conversion, and 2 is a colorimetric sensor that performs photoelectric conversion. A logarithmic compression circuit logarithmically compresses the red, green, and blue components of the light source light, 3 is a differential circuit that subtracts the output of the logarithmic compression circuit 2, and 5 is a photoelectric conversion circuit for subject light R, G, B. An imaging system detects the output as an output; 6 and 7 are an R signal amplifier and a B signal amplifier respectively amplifying the R and B outputs of the imaging system 5; and 8 is a signal processing system for obtaining a predetermined signal. Further, 12 is a constant voltage output circuit that outputs a constant voltage for controlling the R signal amplifier 6° and the B signal amplifier 7 instead of the output of the colorimetric sensor 1 when the amount of light incident on the colorimetric sensor 1 is low; 13 is a switch for switching between the output of the colorimetric sensor l and the output of the constant voltage output circuit 12.

In Fig. 3, the colorimetric sensor l measures the red of the light source.

It outputs Ss, Sa, and So signals corresponding to green and blue components. The output signals of SR, Sa, and Sn are logarithmically compressed by the logarithmic compression circuit 2, resulting in output sentences ogS,.

uogsa, get sentence ogSn. The output compressed by the logarithmic compression circuit 2 is sent to the differential circuit 3, which calculates the logarithmic difference between R and G and B and G. Converted to control voltage. The R signal amplifier 6 and the B signal amplifier 7 amplify the imaging signal from the imaging system 5 using the control voltage 1 and perform white balance adjustment.

At this time, when the ambient light is of low illuminance, errors in the outputs of the colorimetric sensor 1 and the logarithmic compression circuit 2 increase, resulting in inappropriate white balance adjustment. Therefore, in the conventional device as shown in FIG. 3, logs is detected as the illuminance of ambient light, and when the detected output logs falls below a certain reference level, a switch 13 is activated to turn off the colorimetric sensor l and the logarithmic compression circuit 2. ．． Control was performed by switching the control voltage derived by the differential circuit 3 to a constant voltage output. In this case, the constant voltage output is at a low color temperature (
Set the light source to a candle (equivalent to tungsten light).

Based on the above, I was trying to reduce the risk of the white balance becoming significantly off during low light conditions.

[Problems to be solved by the invention] As mentioned above, in the conventional white balance adjustment device,
If the illuminance detection output of ambient light falls below the fixed planting value, the control voltage is fixed to a constant voltage output, so if the output falls below the constant value of l, the information from the colorimetric sensor cannot be used at all. Therefore, if the ambient light is completely different from the color temperature assumed by constant voltage, there is a problem that an extremely large white balance deviation will occur.

This development I11 was developed in order to solve these conventional problems, and even in low illumination, it utilizes information from the colorimetric sensor to prevent the white balance from shifting significantly, and also uses the colorimetric sensor. An object of the present invention is to provide a white balance adjustment device that can suppress the influence of errors.

[Means for Solving the Problems] In order to achieve the above object, the present invention provides an imaging means for converting subject light into an electrical signal, an amplification means for amplifying the electrical signal obtained from the imaging means, It has a control voltage limiting means for limiting the output voltage range of the control voltage of the amplification means, and a means for detecting the amount of ambient light, and the limiting range of the control voltage is variable based on the output of the amount of ambient light detecting means. It has the following configuration.

[Function] By having the above configuration, it is possible to utilize the information of the colorimetric sensor even in low illuminance, and the influence of the error of the colorimetric sensor can be suppressed.

[Embodiment] Fig. 1 is a block diagram of a white balance adjustment device which is an embodiment of the present invention, Fig. 4 is a control voltage limit diagram for explaining Fig. 1, and Fig. 5 is a diagram illustrating Fig. 1. It is a flow chart for explanation.

In FIG. 1, 4 is a microcomputer (hereinafter referred to as microcomputer) for deriving the gain control voltage from the output of the differential circuit 3, and 9 is a memory that stores constants necessary for calculations in this microcomputer 4. Yes, there is also a third
The same reference numerals as in the figures indicate the same or corresponding parts.

Embodiments of the present invention will be described below with reference to FIGS. 1.4.5.

First, similarly to the apparatus shown in Fig. 3, the R of the light source light is measured using the colorimetric sensor l.
, G, B component values, SII, Sc, Sa are derived, logarithmic compression is performed in the logarithmic compression circuit 2, and logarithmic compression is performed in the differential circuit 3.
and logG, take the difference between logB and logG,
Obtain cross(SR/SG) and lOg(Sa/Sn). This output 1-0g (SR/SO), log
Input (Sa/Sn) and uogsa to microcomputer 4,
Control voltages for properly performing white balance correction in the R signal amplifier 6 and the B signal amplifier 7 are derived. Hereinafter, a method for deriving the control voltage will be explained using FIG. 5.

Input log (SR/So), log (Sa
/Sa).

1ogsa is converted into a digital signal by an A/D converter in the microcomputer 4 and read as X, Y, and L, respectively.

Next, Lthl and L stored in the memory are compared as the first limit reference value of brightness (Schip (1))
. At this time, since L is directly proportional to the logarithm of the surrounding light amount value, if the surrounding light is brighter than the first limit reference value LLhl, then L>Lthe. L>Lt
In the case of he, it is compared with the second limit reference value Rii2. However, Lth2 is a value corresponding to light brighter than LLhl (L
th2>LLhl).

Here, Lth2 corresponds to the brightness at which low-luminance correction starts in white balance control, and LLhl corresponds to the brightness at which low-luminance correction in white balance control is performed to the most extreme level, and for brightness below Lthl. If so, no further corrections will be made.

Now, when L>L and L>Lth* (step (2)), that is, when the brightness does not require low luminance correction, first, in step (3), the lower limit value d for Compare and X, and if X≦d, set X=d (
Step (14)) If x>a, leave it as is. Next, in step (4), the upper limit e for X is compared with X, and if X≧e, set X=e (step (15)), and if X<e, leave it as is ( d
, and the values of e are as shown in FIG. 4).

Similarly, for Y, from steps (5) and (6), Y≦
If f, Y≧g, then Y=f (step (16)
), Y = g (step (17)), Y>f
.

If Y<g, leave as is. The above is the flowchart in Figure 5.
(By (), it can be determined that X and Y are within the dashed line in FIG. 4.

Next, in step (7), a-x+b is calculated, and this value is set as Y' and compared with Y. In other words, it is determined whether the Y coordinate is above or below the straight line Y=a-x+b in FIG.

For example, point A is above the line Y=a-x+b and x'
<y (step (8)). In this case, the A coordinate
A Leave (X, Y) as is. On the other hand, point B is Y=a-
Since it is below the straight line of x + b and Y'> Y (step (8)), set x and Y of B (X, Y) to X=X
"=X-a2/(1+a"), Y=Y"=Y+
a/(1+a”) and step (18)), 4th
Move to B''(X''',Y'') in the figure. At this time, if you move point B to point B', that is, B' (X, Y'),
Since the movement is not perpendicular to the straight line n indicating the color change of the black body radiation, a large error occurs in white balance adjustment. On the other hand, if the movement is to point B'', the direction is perpendicular to the straight line n, so only the influence of the object color is removed, and no error occurs in white balance adjustment.

Next, in step (9), aX+C is calculated, and this value is set as Y' and compared with Y. In other words, it is determined whether the Y coordinate is above or below Y=ax+c in FIG. If it is below, that is, Y'> Y (step (10)), leave it as is, and if Y'≦Y, set B
(X, Y) (7) Let X, Y be X=X” =X+a”/(1
+a"), Y=Y" = Y-a/(1+a") (step (19)). Above, the flow in Figure 5 (b) and (
By (a), (X, Y) can be limited to the shaded area in FIG. The effect of this limitation is that it is not affected much by the object color. In addition, by widening the limited range (upper left of straight line n in Figure 54) for the area where the green color is stronger than the blackbody radiation of the straight line n, appropriate white balance adjustment can be made even for light sources that are strong in green, such as fluorescent lamps. I can do it.

Next, L > L the, L < L th2(
In the case where L = the brightness indicated by ogsa is brighter than the first limit value and darker than the second limit value), first, using the constant m stored in the memory, m・(L−Lth,
) and obtain the sentence (step (20)) (where m
If L = L tht then sentence = 0, L = L t
m = 1 / (L
thz L the). Also, the convergence point becomes extremely dark, and the values Z (Xz, Yz) that X and Y should take when L = LLhI are stored in memory, and using those Xz, YZ and the statement, d = X, - (X, -d) 4 e=X, + (e ,(23),
(24) ).

Also, since the straight line n has a slope a, its intercept y is Y, = a
・Xz+y ・”・y==YZ−a−xz Therefore, if the straight line n is represented by a, X, , Y, then Y=a−X
+(Yt-a-Xt).

Then, the intercept of the straight line Y=aX+b, Y=aX+c,
−Y7+a aXz )・1 (step (25)
, (26)').

Based on the constants calculated above, the above L〉L th
+, L > L If the range of X and Y is limited in the same way as in the case of th2, the limited range will become narrower as it gets darker and closer to 0 (in the direction of → in Fig. 4). Then, when the sentence becomes 0, x=x, ,'y=Yz.

Also, L < L th+ (L = 5LogS
If the brightness indicated by a is darker than the first limit value, then d=
e=Xt, f=g=Y, and the values taken by X and Y (7) are only x,,y, respectively, Ltb++LL of 0 or more
h2 is determined according to the specifications of each imaging device, and
, Y, is determined depending on which light source is set at the darkest time.

Now, using x and Y obtained as above 1, control voltages Ctt and Cn are calculated as C++ = h-X + 1
.

Derived by the formula Cu = j - Y +, C8°C1l is sent to the R signal amplifier 6 by the D/A converter in the microcomputer 4.
The signal is sent to the B signal amplifier 7 and white balance adjustment is performed.

FIG. 2 is a block diagram showing another embodiment of the present invention.
0 is the output 5LogS++ of the logarithmic compression circuit 2.

JlogSa to log (SR/SR), log
An arithmetic circuit 11 derives (SR' Su), an output fog (S, /Su) of this arithmetic circuit 10, a sentence og (S
This is an analog limiter circuit that limits the output of R-3u), and the same reference numerals as in FIGS. 1 and 3 indicate the same or corresponding parts.

In FIG. 2, a red component SR and a blue component SB of a light source are outputted from a colorimetric sensor 1, and logarithmically compressed by a logarithmic compression circuit 2 to obtain ogS, ogS,. Arithmetic circuit 10''t'
Jl og (S n/S a) and fog (SI
I"Su) is obtained by differential addition.

Next, log (SR-S u) is used as brightness information, and when this value exceeds a certain level and becomes small, the limiter circuit 11 is activated to limit the value of Jlog (SR/SR). Then, the circuit is configured such that the degree of limiter is strengthened according to the value of the signal og (Ss・Sa), and the voltages CR and Cp for controlling the R signal amplifier 6 and the B signal amplifier 7 are
By deriving l, we obtain a chance.

[Effects of the Invention] As explained above, the present invention narrows the control voltage range of the red and blue amplifiers when the ambient light illuminance is low, so that color measurement is possible even when the illuminance exceeds a certain level at low illuminance. It has been realized that sensor information can be used to prevent sudden large white balance shifts and to reduce the effects of colorimetric sensor errors.

[Brief explanation of the drawing]

Figure m1 is a block diagram of a white balance adjustment device that is an embodiment of this invention, Figure 2 is a block diagram of another embodiment of the present invention, and Figure 3 is a conventional white balance adjustment device. FIG. 4 is a control voltage limit diagram for explaining FIG. 1, and FIG. 5 is a flowchart for explaining FIG. 1. In the figure. l: Colorimetric sensor 2: Logarithmic compression circuit 3: Differential circuit
4: Microcomputer 5: Imaging system 6: R signal amplifier 7: B signal amplifier 8: Signal processing system 9: Memory 10: Arithmetic circuit 11: Limiter circuit 13: Switch agent Patent attorney 1) Haru Kitatake Figure 1 Figure 3 figure

Claims (1)

[Claims] an imaging means for converting subject light into an electrical signal; an amplification means for amplifying the electrical signal obtained from the imaging means; a control voltage limiting means for limiting the output voltage range of a control voltage of the amplification means; 1. A white balance adjustment device comprising: a detection means, and a limiting range of the control voltage is made variable based on the output of the ambient light amount detection means.