JP2002159018A - Method and device for controlling white balance - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent deviation in white balance due to inappropriate light-source type selection by avoiding selecting a sun-light setting at indoor imaging at night or avoiding selecting a daytime setting at outdoor imaging in the evening or at dawn. SOLUTION: A control unit 36 functions both as a light-source type deciding means for selecting the light-source type for an object 31 based on the light- source temperature, and as a correcting means which generates a white balance correction value corresponding to the light source temperature of the light source type which is selected by the light-source type deciding means for correcting the image of the object. The light-source types include at least a first light source type corresponding to the sun light and second light source type. A clocking part 40 functions as a clocking means for clocking a present time. The control unit 36 also functions as an inhibiting means which inhibits the light-source type deciding means from selecting the first light source type if the present time provided by the clocking means is not within a day light time band.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a white balance control device and a white balance control method, and more particularly, to a white balance control device and a white balance control method applicable to a color image photographing device such as an electronic still camera or a video camera.

[0002]

2. Description of the Related Art The color of a subject included in a color image generated by an imaging device such as a CCD (Charge Coupled Device) is represented by an additive color mixture of three primary colors of R (red), G (green), and B (blue). Color of the light source to be used. In additive color mixing, as the mixing ratio of the three primary colors is increased, the amount of light increases additively, and the color changes more vividly, eventually resulting in an achromatic white color. In the above, a balance adjustment of three primary colors (RGB) based on an achromatic portion (white portion), that is, a so-called white balance adjustment is performed. Conventionally, as a white balance control device for performing such adjustment, for example, Japanese Unexamined Patent Application Publication No.
No. 30 is known.

[0003] This white balance control device is generally
The following operation is performed. (1) First, two color difference signals [(RY), (BY)] and a luminance signal are obtained from RGB primary color signals obtained by color separation of an output signal (color imaging signal) of a color imaging device. Generate Y. (2) Next, two color difference signals [(RY), (B-
Y)], two color saturation signals [(RB) and (R + B-2Y)] are generated by converting the color difference signal into axes. (3) Then, these two saturation signals [(RB),
(R + B-2Y)], a threshold (Shiichi) corresponding to the level of the luminance signal Y is provided to extract an achromatic portion (white portion) of the subject included in the color image pickup signal (hereinafter referred to as “white portion”). White area extraction area ”). (4) Finally, the coloration (white balance shift) of the achromatic subject is detected from the signal obtained by integrating the saturation signal included in the white portion extraction area, and the gain of each primary color signal is adjusted so as to eliminate the shift (white balance shift). Generally, R and B gains) are individually feedback controlled.

However, in the above-described white balance control device, the position of the white portion extraction region may not always coincide with the achromatic portion (white portion) of the subject included in the color image pickup signal. There is a drawback in accuracy that sometimes coloring (white balance deviation) of a subject cannot be accurately detected.

FIG. 13 is a schematic diagram showing two chroma signals [(RB) and (R + B-2Y)] obtained by converting the color difference signals into axes. This schematic diagram shows a color difference plane expressed in an orthogonal coordinate system of the (RY) axis and the (BY) axis, and the intensity of magenta (reddish purple) in the 45-degree direction and the intensity of blue in the 135-degree direction. Strength, 2
The intensity of green is represented in the direction of 25 degrees, and the intensity of red is represented in the direction of 315 degrees. The signal (RB) is on an axis 1 connecting red and blue, and the signal (R + B-2Y) is an axis 2 connecting magenta and green.
, And the luminance signal Y is in the Z-axis direction of this drawing (the front and back direction of the drawing).

In this figure, a rectangular figure 3 whose longitudinal direction is the direction of the axis 1 and whose short side is the direction of the axis 2 is
The position of the rectangular figure 3 is set along the locus 4 of the color temperature change according to the blackbody radiation. However, since the trajectory 4 merely represents the color temperature change of a specific light source such as sunlight, for example, and does not correspond to the color temperature change of another light source such as a fluorescent lamp or an incandescent lamp, the type of the light source Is changed, the position of the white area extraction area becomes inappropriate, and the color of the achromatic subject becomes white (white balance deviation).
Has the disadvantage that it cannot be detected accurately.

In order to cope with other light sources, the technique disclosed in the above publication is designed so that the position of the "white portion extraction region" on the color difference plane can be artificially changed for each type of light source. ing.

[0008]

However, in the technology described in the above publication, in order to cope with other light sources, the position of the "white portion extraction region" on the color difference plane is artificially changed for each type of light source. Can be changed manually, but it has to be set manually each time, which not only causes inconvenience in operation, but also inevitably results in erroneous operation.For example, if you select the setting for sunlight during indoor shooting at night Or, if the setting for daytime is selected during outdoor shooting in the evening or early morning, there is a problem that the white balance is greatly shifted.

Therefore, the problem to be solved by the present invention is that the type of the light source of the subject can be accurately determined, and thus, for example, the selection of the setting for sunlight during indoor shooting at night or the selection of the setting in the evening or early morning can be avoided. It is an object of the present invention to provide a white balance control device and a white balance control method that avoid the selection of daytime settings during outdoor shooting and prevent white balance deviation due to inappropriate light source type determination.

[0010]

According to a first aspect of the present invention, there is provided a white balance control apparatus comprising: a light source type determining unit for determining a light source type of a subject based on a light source temperature; and a light source type determining unit. Correction means for generating a white balance correction value corresponding to the light source temperature of the light source type and correcting the image of the subject, wherein the light source type is at least a first light source type corresponding to sunlight and a third light source type other than the first light source type. A light source type, and a first time light source type judging means in the light source type judging means when the current time measured by the time means does not fall in a daylight time zone. And a prohibition unit for prohibiting the operation. According to the present invention, when the current time is not in the daylight time zone, the white balance correction corresponding to the light source temperature of the first light source type corresponding to sunlight is forcibly prohibited. A white balance control device according to a second aspect of the present invention includes a light source type determination unit that determines a light source type of a subject based on the light source temperature, and a light source temperature of the light source type determined by the light source type determination unit. Correction means for generating a white balance correction value to correct the image of the subject, wherein the light source type includes at least a first light source type corresponding to sunlight and a second light source type other than the first light source type, Clocking means for measuring the current time; position detecting means for detecting the current position; time zone setting means for setting a daylight time zone from the sunrise time and sunset time of the current position detected by the position detecting means; If the current time measured by the clocking means does not fall within the daylight time zone set by the time zone setting means, the first light source type determining means And inhibiting means for inhibiting the determination of the source type, characterized by comprising a. According to the present invention, when the current time is not within the daylight time zone, the white balance correction corresponding to the light source temperature of the first light source type corresponding to sunlight is forcibly prohibited, and the daylight time zone is not changed. It is set from the sunrise time and the sunset time at the current position. According to a third aspect of the present invention, there is provided a white balance control device according to the first or second aspect.
In the white balance control device according to any one of the above,
The first light source type is divided into a first A light source type corresponding to early morning or evening sunlight and a first B light source type corresponding to daytime sunlight other than early morning and evening. When the current time measured by the clocking means does not fall in the early morning time zone or the evening time zone, the determination of the first light source type by the light source type determining means is prohibited, while the current time is in the early morning time zone and the evening time zone. When the daylight hours other than the time zone are not included, the determination of the first B light source type by the light source type determining means is prohibited. According to the present invention, when the current time is not in the early morning (or evening) time zone, the white balance correction corresponding to the light source temperature of the first A (or first B) light source type corresponding to the early morning (or evening) sunlight is performed. Forbidden. A white balance control method according to a fourth aspect of the present invention includes a light source type determining step of determining a light source type of a subject based on the light source temperature, and a light source temperature of the light source type determined in the light source type determining step. A correction step of generating a white balance correction value to correct the image of the subject, wherein the light source types include at least a first light source type corresponding to sunlight and a second light source type other than the first light source type,
Further, a clocking step of clocking the current time, and a prohibition step of prohibiting the determination of the first light source type in the light source type determination step when the current time measured in the clocking step does not fall in a daylight time zone, It is characterized by having. According to the present invention, when the current time is not in the daylight time zone, the white balance correction corresponding to the light source temperature of the first light source type corresponding to sunlight is forcibly prohibited. A white balance control method according to a fifth aspect of the present invention includes a light source type determining step of determining a light source type of a subject based on the light source temperature, and a light source temperature of the light source type determined in the light source type determining step. A correction step of generating a white balance correction value to correct the image of the subject, wherein the light source types include at least a first light source type corresponding to sunlight and a second light source type other than the above. A time measuring step for measuring the current time, a position detecting step for detecting the current position, and a time zone setting step for setting a daylight time zone from the sunrise time and sunset time of the current position detected in the position detecting step, If the current time measured in the time counting step is not within the daylight time zone set in the time zone setting step, the light source type determining step is performed. And having a prohibition step of prohibiting the judgment of the first light source type in-flop, a. According to the present invention, when the current time is not within the daylight time zone, the white balance correction corresponding to the light source temperature of the first light source type corresponding to sunlight is forcibly prohibited, and the daylight time zone is not changed. It is set from the sunrise time and the sunset time at the current position. A white balance control method according to a sixth aspect of the present invention is the white balance control method according to any one of the fourth and fifth aspects, wherein the first light source type is a first light source type corresponding to early morning or evening sunlight. The light source type is divided into a first B light source type corresponding to daytime sunlight other than early morning and evening. If the current time does not fall within the daytime hours other than the early morning time zone and the evening time zone, the light source type determination is made. It is characterized in that the determination of the first B light source type in the step is prohibited. According to the present invention, if the current time is not in the early morning (or evening) time zone, the early morning (or evening)
The white balance correction corresponding to the light source temperature of the 1A (or 1B) light source type corresponding to the sunlight is forcibly prohibited.

[0011]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be described below with reference to the drawings, taking an electronic still camera such as a digital camera as an example.

First, the configuration will be described. FIG. 1 is an external view of an electronic still camera. In the figure, an electronic still camera 10 includes a lens barrel 1 on a front surface of a camera body 11.
2. In addition to a finder window 13 and a strobe window 14, a shutter key 15, a strobe on / off key 16 and a self-timer key 17 are provided on the upper surface, and a power switch 18, a zoom button 19, a recording / playback mode are provided on the back surface. The camera includes a changeover switch 20, a display on / off key 21, a finder eyepiece window 22, a liquid crystal display 23, and the like.

The lens barrel 12 contains a photographing lens group having an optical zoom function and a mechanical shutter mechanism. The lens barrel 12 has a light-receiving surface of an image sensor, which will be described later, disposed at the rear end of the lens barrel 12. This is for forming an image of a subject. The finder window 13 is integrated with the finder eyepiece window 22 on the rear side of the camera body 11, and is used when visually confirming the composition. The strobe window 14 is a transmission window through which strobe light is emitted, which will be described later. In many cases, a small lens for adjusting the spread of the luminous flux of the strobe light according to the angle of view of the photographing lens group is arranged on the entire surface. I have.

The shutter key 15 is depressed during photographing. Also, strobe on / off key 1
Reference numeral 6 designates whether to permit or inhibit strobe light emission, and a self-timer key 17 switches on / off of a self-timer. Although various function keys such as a menu key are provided in addition to these, they are omitted in the figure. The power switch 18 turns on and off the power of the electronic still camera 10. The zoom button 19 is the angle of view of the optical lens (ie, the zoom ratio)
When the "+" side is pressed, the angle of view is reduced, and when the "-" side is pressed, the angle of view is increased.

Recording / reproduction mode switch 20
Switches the operation mode of the electronic still camera 10 between the recording mode and the reproduction mode. When the recording mode is set, the liquid crystal display 23 can be used as a finder. The display on / off key 21 is used for the liquid crystal display 23 in the recording mode.
Is used as a substitute for the finder. The liquid crystal display 23 is a high-resolution color liquid crystal display. As described above, a through image is displayed in the recording mode, used as a finder, a preview image is displayed during reproduction, and various setting screens are displayed. Things.

FIG. 2 is a conceptual functional block diagram of the electronic still camera 10. In this block diagram, for convenience, the imaging unit 32, the image processing unit 33, the strobe unit 34, the operation unit 35, and the control unit 36 (light source type determination unit, correction unit,
Display control unit 37, display unit 38 (corresponding to the liquid crystal display 23 in FIG. 1), image storage unit 39, clock unit 40 (clock unit), and position detection unit 41.
(Position detecting means).

The image pickup section 32 includes a photographing lens group, a mechanical shutter mechanism, and the like. The image pickup section 32 picks up an image of the subject 31 and generates a color image signal of several tens of frames per second. )including. The color image sensor includes an auxiliary circuit such as a timing circuit, a sampling and holding circuit, and an analog-to-digital conversion circuit. The color image signal digitized by the analog-to-digital conversion circuit (hereinafter, simply referred to as an image signal) is processed by the image processing unit 33. Output to The image processing unit 33 separates the input image signal into a luminance component (Y) and color components (Cr, Cb), performs white balance correction described below, and then outputs the corrected YCrCb signal to the control unit 3.
6 is output.

The strobe section 34 emits instantaneous auxiliary light (strobe light) 34a for illuminating the subject 31 in accordance with a drive signal from the control section 36. The operation unit 35 includes various operation keys provided on the camera body 11, that is,
The aforementioned shutter key 15, strobe on / off key 1
A key signal in response to the operation of the self-timer key 6 and the self-timer key 17 is generated and output to the control unit.

The control unit 36 includes a CPU 36a as shown in the block diagram of FIG.
36a, a program memory 36 via a bus 36b.
c, work memory 36d, input unit 36e, and output unit 36
f etc. are connected. The CPU 36a loads a predetermined control program stored in the program memory 36c into the work memory 36d and executes the control program, thereby fetching data from the input unit 36e and outputting the data to the output unit 36e.
The entire operation of the electronic still camera 10 is controlled while writing data to f.

The display control unit 37 converts the through image, preview image, various setting screens, and the like output from the control unit 36 into a display format of the display unit 38 and outputs the display format to the display unit 36. Control unit 37 and display unit 38
Constitute display means integrally. The image storage unit 39
A recording medium for recording a captured image (also referred to as a captured image) in a nonvolatile manner (that is, information is not lost even when the power is turned off). For example, a semiconductor storage device such as a flash memory or a magnetic memory device is used. Used. Note that the image storage unit 39 may be detachably mounted on the electronic still camera.

The clock section 40 measures the current date and time information (date information and time information). Although the timing unit 40 is externally attached to the control unit 36 in FIG.
Since the microcontroller including U has a date and time measurement function, the built-in function may be used as a timer. The position detection unit 41 acquires position information of the electronic still camera 10, and the position information is, for example, GPS information.
(Global Positioning System)
Information and location information (zone information) of a cellular mobile phone system such as a PHS (Personal Handy-phone System) can be used.

Here, since the point of the present invention lies in the white balance control, a portion related to the control function will be described in detail. FIG. 4 is a block diagram of the image processing unit 33 having a white balance control function. In this figure, an image signal output from an imaging unit 32 is input to a color separation circuit 41, where the three primary color component signals of a light source color, that is, a red signal (R) and a green signal (G ) And a blue signal (B). Hereinafter, these red, green, and blue signals may be referred to as “primary color signals”.

The three primary color signals R, G, and B are sent to the color difference signal generation circuit 44. The two primary color signals of R and B are transmitted to the amplifier 4 inserted in the transfer path.
The gain can be adjusted by 2, 43.
That is, the amplifier 42 in the R path controls the gain of the primary color signal R according to the signal Sa, the amplifier 43 in the B path controls the gain of the primary color signal B according to the signal Sb, and the light source is controlled by using these signals Sa and Sb. Three primary color signals R, G, B
You can adjust the balance.

The color difference signal generation circuit 44 generates a luminance signal Y and two color difference signals [(RY), (BY)] based on the three primary color signals R, G, B, and generates them. The signal is output to the control unit 36 as a YCrCb signal, and is also output to the saturation signal generation circuit 45. Where YC
Y of the rCb signal is a luminance signal (Y), Cr is one color difference signal (RY), and Cb is the other color difference signal (BY).

The saturation signal generation circuit 45, the white area extraction circuit 46, and the WB (white balance) setting circuit 47 integrally perform operations similar to those of the prior art white balance control device described at the outset. That is, the saturation signal generation circuit 45 outputs two color difference signals [(RY) and (B-
Y)] at a predetermined ratio (here, 1: 1 for convenience) to generate two chroma signals [(RB), (R + B-2Y)] obtained by axially transforming the color difference signal. , The white area extraction circuit 46 outputs these two saturation signals [(R−
B), (R + B−2Y)], a threshold (Shiichi) corresponding to the level of the luminance signal Y is applied, and a saturation included in a predetermined “white portion extraction region” of a saturation signal exceeding the threshold is applied. Extract the degree signal. The WB setting circuit 47 detects the coloring (white balance shift) of the achromatic subject from the signal obtained by integrating the extracted chroma signal, and individually adjusts the gains of the primary color signals R and B so as to eliminate the shift. Signals Sa and Sb for feedback control are generated.

Here, the white portion extraction region is a region corresponding to the rectangular figure 3 in FIG. The position of the white portion extraction region (the position on the axis 1 and the axis 2 in FIG. 13) is set based on the output signal E of the position designation signal generation circuit 48.
The position designation signal generation circuit 48 includes an average value calculation unit 49, a chromaticity conversion unit 50, a chromaticity pattern evaluation unit 51, and a chromaticity pattern table 52, and the functions of each unit are as follows.

<Average Value Calculator 49> Average Value Calculator 49
Is the average value of the primary color signals R, G, B in the image plane
R_AV, G _AV, B_AVIs calculated. Outline this averaging operation
Then, the image of the image signal after the color separation by the color separation circuit 41 is performed.
The elementary array can be represented schematically as shown in FIG.
Wear. However, the example shown is a general Bayer type pixel arrangement.
Columns, but not limited to. Fig. 5 (a)
Each of the cells constituting the image signal 61 is
Red pixel (R), green pixel (G) and blue pixel (B)
is there. In the average value calculation processing, as shown in FIG.
The image signal 61 is divided into N × N pixel blocks.
Average value of red pixels included in each pixel block
(R_AV), The average value of the green pixels (G_AV) And blue pixel flat
Average value (B_AV) Is calculated. In FIG. 5B, N = 2
However, this is convenient for illustration. Actually N is
It is an integer of 2 or more.

<Chromaticity Conversion Unit 50> The chromaticity conversion unit 50 converts the R _AV , G _AV , and B _AV for each pixel block into chromaticity (R
/ G, B / G). Here, a curve 63 shown on the chromaticity diagram of FIG. 6 is a locus of chromaticity (color temperature) of, for example, the relative spectral distribution of sunlight in a perfect radiator (black body). Some points and numerical values (15
00∞) represents the color temperature at that point, and this curve 6
From FIG. 3, it can be seen that even with the same light source, the color temperature differs depending on the time zone.

<Chromaticity Pattern Table 52> The chromaticity pattern table 52 has a preset data table, for example, as shown in FIG. In FIG. 7, the data table 64 has a two-dimensional table map structure in which the vertical axis is B / G and the horizontal axis is R / G, and each cell is defined as a point of chromaticity coordinates (x, y). , Some points are collected into a segment, and the collection of segments is used as a pattern. Each of s0 to s28 is a segment, and a weight value (w0 to w28) is set for each segment.

Here, for example, s9, s10 and s11
These three segments constitute one pattern corresponding to the curve 63 shown on the chromaticity diagram of FIG. Hereinafter, this pattern is referred to as a “sunlight pattern” for convenience. Although not shown, artificial light other than sunlight, for example, a "fluorescent light pattern" or an "incandescent light pattern" is similarly constituted by some other segments.

<Chromaticity Pattern Evaluating Unit 51> The chromaticity pattern evaluating unit 51 uses the chromaticity pattern table 52 to evaluate the chromaticity (R / G, B / G) pattern for each pixel block. Do. That is, as shown in FIG. 8A, first, the corresponding segment of the chromaticity pattern table 52 corresponding to the coordinate position of the input chromaticity (R / G, B / G) (in the figure, the segment 65 for convenience). To identify. The x mark shown in the square of the segment 65 is the chromaticity coordinate position (x, y) of the input chromaticity (R / G, B / G),
In the illustrated example, the chromaticity (R /
Since the coordinate position (x, y) of (G, B / G) matches, as shown in FIG. 8B, the value of the match count number n corresponding to each cell is updated by +1. By executing this operation for all the chromaticities (R / G, B / G) of each pixel block, the pattern evaluation data (the match count corresponding to each cell) of the image signal currently being processed is obtained. Data containing the value of the number n).

FIG. 9 is a flowchart showing the operation up to this point including the above-described calculation of the average values of R, G, and B. This flowchart is described for each pixel block (step S21).
Calculation of average values of R, G, and B (R _AV , G _AV , B _AV ) (step S21a), chromaticity conversion (step S21b), and update processing of the match count n (step S21c) are performed. Pattern evaluation value calculation (step S22)
a) is repeatedly executed for all chromaticity patterns (step S22), and finally, an appropriate white point chromaticity is determined from the chromaticity pattern evaluation value and the current date and time information, and a white balance corresponding to the chromaticity is set. (Step S23).

As described above, in the present embodiment, the imaging unit 3
R for each pixel block of the image signal output from
The G and B average values (R _AV , G _AV , and B _AV ) are calculated, the chromaticity conversion and the update processing of the match count n are performed, and the calculation of the chromaticity pattern evaluation value is performed for all chromaticity patterns. It is repeatedly executed, and finally, an appropriate white point chromaticity is determined from the chromaticity pattern evaluation value and the current date and time information, and a white balance corresponding to the chromaticity is set. The chromaticity pattern evaluation value differs depending on whether sunlight or artificial light is used, or even the same sunlight depends on sunny weather, sunset, and the like.
Artificial light also differs between fluorescent lamps and incandescent lamps, which are due solely to differences in the color temperature of the light source. Although a certain degree of discrimination can be obtained by threshold value judgment alone, 100% certainty cannot be obtained. . This is because the color temperatures of different light sources may be partially similar. Therefore,
Color temperature (light source) discrimination based only on the chromaticity pattern evaluation value
Although it is undeniable to make a mistake, such a mistake refers to, for example, a sunlight pattern during indoor shooting at night or a daytime sunlight pattern during outdoor shooting in the early morning or evening. Therefore, there is room for improvement in that the white balance is shifted.

Therefore, in the present embodiment, it is determined whether or not it is a time zone in which the sun is not rising based on the time information at the time of photographing, and if so, the sunlight pattern is not referred to from the beginning. It is intended to ensure that the above disadvantages are avoided.

FIG. 10 is a specific flowchart of the above-described step S22 in which such a mechanism is implemented. In this flowchart, for example, it is assumed that three types of light source patterns, a sunlight (daylight) pattern, a fluorescent light pattern, and an incandescent light pattern, are evaluated. Evaluation shall also be performed.

When the flowchart is started, first, it is determined whether or not the time is in a time zone when the sun is rising (step S31). This time zone is called "daylight time zone" for convenience.
In this case, when it is determined that the daylight is in the daylight time zone, it is determined whether the sunlight pattern evaluation value is equal to or more than a specified value (step S32). The sunlight pattern evaluation value is a value of the match count number n corresponding to each cell of the sunlight pattern (for example, a pattern composed of the segments s9, s10, and s11 in FIG. 7) in the chromaticity pattern table 52. , Each segment s9, s10
And s11. For example,
Assuming that the match count numbers n of the segments s9, s10, and s11 are n9, n10, and n11, respectively, and the weight values are w9, w10, and w11, the sunlight pattern evaluation value is represented by the formula “n9 × w9 + n10 × w10 + n11 × w”.
11 ".

Now, assuming that the sunlight pattern evaluation value is equal to or greater than the specified value, it is determined whether the sky pattern evaluation value is equal to or greater than the specified value (step S33). If it is not less than the value, the weight value of the segment corresponding to the high color temperature in the sunlight pattern is reduced by a predetermined amount (step S34). Next, it is determined whether the color temperature of sunlight is different even during the daytime, for example, whether it is during the evening (step S35). In the case of the evening, the sunset pattern evaluation value is equal to or greater than the specified value. Is determined (step S36), and if the sunset pattern evaluation value is equal to or greater than the specified value, the weight value of the segment corresponding to the low color temperature in the sunlight pattern is reduced by a predetermined amount (step S37). . Then, the segment having the highest evaluation value is determined as a white point segment from the pixel blocks corresponding to the segments in the sunlight pattern (step S38), and the center of gravity of the pixel block data of the white point segment is designated as a white point extraction position. And outputs the signal E to the white area extraction circuit 46.

Therefore, of the segments s9, s10 and s11 constituting the sunlight pattern, for example, s1
If 1 is a segment with a high color temperature and s9 is a segment with a low color temperature, if the sunlight pattern evaluation value is equal to or greater than a specified value and the sky pattern evaluation value is equal to or greater than the specified value,
While the weight value of the segment s11 having a high color temperature is reduced and corrected, the sunlight pattern evaluation value is equal to or more than a specified value, and
If it is the evening time zone and the sunset pattern evaluation value is also equal to or more than the specified value, the weight value of the segment s9 having a low color temperature is reduced and corrected. , A suitable white point segment is dynamically determined in accordance with, and a signal E specifying the barycentric point of the pixel block data of the white point segment as a white point extraction position can be generated. As a result, the extraction position of the white portion in the white portion extraction circuit 46 is optimized for any of the captured image in a clear sky with a lot of blue sky and the captured image in the background of the sunset, and The special effect that the coloring (white balance deviation) of the colored object can be detected accurately can be obtained. In addition, when the current time does not fall in the evening time zone, the segment s9 having an absolutely low color temperature.
Since the weight value of is not reduced and corrected, the operation of determining a white point segment according to the difference in color temperature can be optimized,
A special effect is obtained in that erroneous white point extraction position designation can be avoided.

On the other hand, when the current time is in a time zone other than the daylight time zone (in the case of "No" determination in step S31), or when the sunlight pattern evaluation value is not equal to or greater than the specified value (step S32). In the case of “No” determination), it is determined that the artificial light source is other than the sunlight, and first, it is determined whether the fluorescent light pattern evaluation value is equal to or more than a specified value (step S40). If the fluorescent light pattern evaluation value is equal to or more than the specified value, the white point position is determined from the pixel block data center of gravity of the segment forming the fluorescent light pattern (step S41), and the fluorescent light pattern evaluation value must be equal to or more than the specified value. Then, it is determined whether or not the incandescent lamp pattern evaluation value is equal to or greater than a specified value (step S42). If the fluorescent light pattern evaluation value is equal to or more than the specified value, the white point position is determined from the pixel block data center of gravity of the segment constituting the incandescent light pattern (step S43), and the fluorescent light pattern evaluation value must be equal to or more than the specified value. For example, the white point position is determined from the pixel block data barycenter of the segment constituting the sunlight pattern (step S44).

Therefore, according to the present embodiment, not only sunlight but also color image signals photographed using other light sources such as fluorescent lamps and incandescent lamps can correspond to the color temperature of the light sources. White point position can be determined from the pixel block data center of gravity of the segment, and the position of the white portion extraction area is optimized regardless of the type of light source to accurately detect the coloring (white balance deviation) of the achromatic subject. In addition to the special advantage of being able to perform the process, when the current time is not in the daylight time zone, the process is forcibly branched to the artificial light source pattern evaluation processing step (step S40 and subsequent steps). For example,
Even when an artificial light source having a light source temperature similar to sunlight is used at the time of indoor shooting at night or the like, a unique effect is obtained in that the sunlight pattern evaluation processing step (step S32 and subsequent steps) is never executed. Can be

FIG. 11 is a conceptual diagram showing the effect of the present embodiment. In this embodiment, when the automatic white balance is set in the photographing standby state (step S11), the current time of the timer 40 is set. If the time information is within the set range corresponding to the daylight time zone (“YES” in step S12), the white balance is set based on the chromaticity pattern evaluation value other than sunlight (step S13), On the other hand, if not within the setting range ("NO" in step S12), the white balance is set based on one of all the chromaticity pattern evaluation values including sunlight (step S13). Then, the image of the subject 31 after the white balance is set is recorded in the image storage unit 39 when the shutter key 15 is pressed down.

Therefore, as can be understood from this conceptual diagram, even if an artificial light source having a light source temperature similar to that of sunlight is used outside the daylight time zone, it is absolutely necessary to Since the white balance setting (step S13) based on the evaluation value of the light pattern is not performed, the problem of the present invention described at the beginning, that is, the type of the light source of the subject can be accurately determined. A white balance control device and a white balance control that avoid selecting a setting for sunlight or avoiding selecting a setting for daytime during outdoor shooting in the evening or early morning to prevent a shift in white balance due to inappropriate light source type determination. A method can be provided.

By the way, strictly speaking, the daylight time zone is a time zone from sunrise to sunset, but the time of sunrise and sunset differs depending on the region. Instead, it is desirable to take into account information on the use position of the electronic still camera 10 (position information). FIG. 12 is a conceptual diagram in which position information is taken into account.
This is a modification of FIG. In FIG.
If the same step numbers are assigned to the steps corresponding to those in FIG. 11, the difference is that the current position information is fetched from the position information detecting unit 41 (step S51), and the sunrise and sunset times at the current position are calculated. (Step S52) and a step (Step S53) of determining whether or not the current time acquired from the timer 40 is in a time zone between sunrise and sunset. According to this, an accurate daylight time zone can be set by eliminating the regional difference.

In the present embodiment, the sunlight pattern is divided into a daylight pattern and an evening pattern, and when the evaluation value of the sunset pattern is equal to or more than a predetermined value, the weight of the segment corresponding to a low temperature is determined. As well as
In order to ensure the operation of the weight correction, if the current time is not in the evening time zone, the weight correction processing (step S37) is forcibly passed, but the present invention is not limited to this. . For example, the sunlight pattern is divided into an early morning pattern in addition to a daylight pattern and an evening pattern, and if the evaluation value of the early morning pattern is equal to or more than a predetermined value, the weight of the segment corresponding to a low temperature is reduced. In addition, in order to ensure the operation of the weight correction, if the current time is not in the early morning time zone, the weight correction process may be forcibly passed. Daylight hours can be divided into "early morning", "evening" and other time zones, and appropriate branch processing can be performed depending on whether the actual time is included in each time zone. Thus, more precise pattern evaluation processing can be performed.

[0045]

According to the present invention, when the current time is not in the daylight time zone, the white balance correction corresponding to the light source temperature of the first light source type corresponding to sunlight. Is forbidden. Therefore, avoiding the selection of sunlight settings during indoor shooting at night, or
A white balance control device or control method can be realized that avoids selection of daytime settings during outdoor shooting in the evening or early morning and prevents white balance deviation due to inappropriate light source type determination. According to the second or fifth aspect of the invention, when the current time is not in the daylight time zone, the white balance correction corresponding to the light source temperature of the first light source type corresponding to sunlight is forcibly prohibited. At the same time, the daylight time zone is set from the sunrise time and the sunset time at the current position. Therefore, it is possible to set an appropriate determination time zone in consideration of a regional difference, and it is possible to realize a white balance control device or control method with further less deviation. According to the third or sixth aspect of the present invention, if the current time is not in the early morning (or evening) time zone, the first A (or first B) light source type corresponding to early morning (or evening) sunlight The white balance correction corresponding to the light source temperature is forcibly prohibited. Therefore, not only during the daytime, but also in the early morning or evening outdoor shooting, good white balance correction can be performed, and inappropriate white balance correction other than early morning or evening hours (for the 1A or 1B light source type). Corresponding white balance correction) can be prevented.

[Brief description of the drawings]

FIG. 1 is an external view of an electronic still camera 10. FIG.

FIG. 2 is a conceptual functional block diagram of the electronic still camera 10.

FIG. 3 is a block diagram of a control unit 36.

FIG. 4 is a block diagram of an image processing unit 33.

FIG. 5 is a pixel array diagram of an image signal.

FIG. 6 is a chromaticity diagram of a perfect radiator.

FIG. 7 is a structural diagram of a chromaticity pattern table 52;

FIG. 8 is a conceptual explanatory diagram of chromaticity pattern evaluation.

FIG. 9 is an operation flowchart including an average value calculation of R, G, and B.

FIG. 10 is a diagram showing a specific flowchart of step S22 in FIG. 9;

FIG. 11 is a conceptual diagram showing an effect in the present embodiment.

FIG. 12 is a conceptual diagram (modification of FIG. 11) in which position information is added.

FIG. 13 is a schematic diagram showing two chroma signals obtained by converting the axis of a color difference signal.

[Explanation of symbols]

31 subject 36 control unit (light source type determination unit, correction unit, prohibition unit, time zone setting unit) 40 clock unit (clock unit) 41 position detection unit (position detection unit)

Continued on the front page F-term (reference) 5C065 AA01 AA03 BB02 CC01 DD02 DD17 EE05 EE06 FF05 GG15 GG17 GG22 GG26 GG32 5C066 AA01 CA08 CA11 EA15 GA01 GA02 GA05 GA33 KA12 KD06 KE05 KE07 KM01 KM05 K10 K03 K03

Claims (6)

[Claims] A light source type determining unit that determines a light source type of a subject based on the light source temperature; and a white balance correction value corresponding to a light source temperature of the light source type determined by the light source type determining unit. Correction means for correcting an image of a subject, wherein the light source type includes at least a first light source type corresponding to sunlight and a second light source type other than the above, and further, a clocking unit for clocking the current time; If the current time measured by the clocking means is not in the daylight time zone, the first light source type determining means
A white balance control device, comprising: prohibition means for prohibiting determination of a light source type. 2. A light source type determining means for determining a light source type of a subject based on the light source temperature; and generating a white balance correction value corresponding to a light source temperature of the light source type determined by the light source type determining means. Correction means for correcting an image of a subject, wherein the light source type includes at least a first light source type corresponding to sunlight and a second light source type other than the above, and further, a clocking unit for clocking the current time; Position detection means for detecting the current position; time zone setting means for setting a daylight time zone from the sunrise time and sunset time of the current position detected by the position detection means; and the current time measured by the time measurement means. Prohibition means for prohibiting the determination of the first light source type in the light source type determination means when the daylight time zone set by the time zone setting means has not been entered; A white balance control device comprising: 3. The first light source type is divided into a first A light source type corresponding to early morning or evening sunlight and a first B light source type corresponding to daytime sunlight other than early morning and evening. The prohibition means prohibits the first light source type determination by the light source type determination means when the current time measured by the time measurement means does not fall in the early morning time zone or the evening time zone. 3. The method according to claim 1, wherein the first light source type determination by the light source type determination unit is prohibited when the time is not in a daytime period other than an early morning time zone and an evening time zone. White balance control device. 4. A light source type determining step of determining a light source type of a subject based on the light source temperature; and generating a white balance correction value corresponding to the light source temperature of the light source type determined in the light source type determining step. A correction step of correcting an image of a subject, wherein the light source types include at least a first light source type corresponding to sunlight and a second light source type other than the above, and a time counting step of clocking a current time; A white balance control comprising: a prohibition step of prohibiting the determination of the first light source type in the light source type determination step when the current time measured in the timing step does not fall within the daylight time zone. Method. 5. A light source type determining step of determining a light source type of a subject based on the light source temperature; and generating a white balance correction value corresponding to the light source temperature of the light source type determined in the light source type determining step. A correction step of correcting an image of a subject, wherein the light source types include at least a first light source type corresponding to sunlight and a second light source type other than the above, and a time counting step of clocking a current time; A position detection step of detecting a current position; a time zone setting step of setting a daylight time zone from a sunrise time and a sunset time of the current position detected in the position detection step; and a current time measured in the clocking step. Prohibits the determination of the first light source type in the light source type determination step when does not fall within the daylight time zone set in the time zone setting step A white balance control method, comprising: 6. The first light source type is divided into a first A light source type corresponding to early morning or evening sunlight and a first B light source type corresponding to daytime sunlight other than early morning and evening. The prohibition step prohibits the determination of the first A light source type in the light source type determination step when the current time measured in the time measurement step does not fall in the early morning time zone or the evening time zone. The method according to claim 4, wherein the determination of the first B light source type in the light source type determination step is prohibited when the vehicle is not in a daytime time zone other than the early morning time zone and the evening time zone. White balance control method.