JP2002095003A - Electronic camera - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an electronic camera which improves the accuracy of the determination of white and can obtain superior white balance, when white is not present in an imaging object. SOLUTION: This electronic camera is equipped with an imaging means 12 which converts a signal of an object into an electrical signal and outputs an analog image signal, an A/D-converting means 14 which converts the analog image signal to a digital image signal, an image-dividing means 20 which divides the digital image signal into plural regions; a selecting means 26, which determine selecting or not-selecting regarding the plural divided regions according to prescribed reference; and a WB-detecting means 30 which obtains a WB correction value by using information of plural regins selected by the selecting means.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electronic camera, and more particularly, to adjustment of WB (white balance) of an electronic camera.

[0002]

2. Description of the Related Art There is known a technique for automatically adjusting white balance (WB) based on an output signal of an image pickup device or the like. In such a technique, if the white balance gain is not within a certain range, a specific gain (for example,
A technique for setting sunlight has been disclosed (Japanese Patent Application Laid-open No.
-25188). However, in this case, for example, when there is no white under the light source A or under the fluorescent lamp, there is a problem that the white balance is largely shifted. There is also disclosed an apparatus that determines indoors and outdoors based on the luminance of a subject and adjusts the white balance by further changing the white determination area based on the determination result (Japanese Patent Application Laid-Open No. Hei 7-2518845). Here, it is described that the WB area is changed according to the light source. However, when there is no white, it is described that the value previously determined as white is used. Therefore, even with this method, since the image was not necessarily taken under the light source last time, the white balance may be largely shifted.

[0003]

As described above, in the prior art, the white balance is adjusted based on white in the white balance adjustment. Therefore, when there is no white, the white balance is greatly shifted. There is a problem.

The present invention improves the accuracy of white determination and
It is an object of the present invention to provide an electronic camera capable of obtaining a good white balance even when a subject to be photographed has no white.

[0005]

According to the present invention, the following means have been taken in order to solve the above-mentioned problems.

[0006] An electronic camera according to the present invention includes: an imaging unit that converts a signal of a subject into an electric signal and outputs an analog image signal; an A / D conversion unit that converts the analog image signal into a digital image signal; Image dividing means for dividing the digital image signal into a plurality of areas; selecting means for selecting or unselecting the plurality of divided areas according to a predetermined criterion; and a plurality of areas selected by the selecting means And a WB detecting means for obtaining a WB correction value using the information of (1).

A preferred embodiment of the above electronic camera is
It is as follows.

(1) The number of divisions set by the image division means is n times or 1 / m of the number of pixels of the thumbnail image.
(N and m are positive integers). (2) The selecting means further includes a block luminance calculating means, and the selection or non-selection is determined according to the luminance value calculated by the block luminance calculating means. (3) The selecting means further includes a block saturation calculating means, and the selection or non-selection is determined according to the output. (4) The selection means has area information of a predetermined color space, and determines selection or non-selection according to whether or not the color space area is included. (5) In (4), the color space area information is a substantially blue color space, and the selecting unit does not select an area included in the area. (6) In the item (4), the color space area information is substantially a lawn color space, and the selecting means does not select an area included in the area. (7) In (4), the color space area information is a substantially white color space, and the selecting means selects an area included in the area.

[0009]

Embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a schematic block diagram of an electronic camera according to the present invention, and is a diagram showing processing blocks from imaging to image processing. The optical image of the subject transmitted through the lens 11 is converted into an electric signal by the CCD 12, amplified by the amplifier 13, and then converted into a digital signal by the A / D converter 14. The output from the A / D converter 14 is output from the minute area integrator 20, the WB correction unit 30, and the luminance signal processing unit 40.
Entered as The minute area integrator 20 receives a digital signal and outputs RGB components. This output is SD
Output to the RAM 21 and the WB evaluation value calculation unit 25,
The RGB signals input to the AM 21 are input to the image processing unit 22 to create a thumbnail image. On the other hand, the RGB signals input to the WB evaluation value calculation unit 25 are converted into Y, R / G, B / G signals, and input to the WB detection unit 26. The WB detecting section 26 detects WB based on the Y, R / G, B / G signals and the output from the AE means. The detection result of the WB detection unit 26 is input to the WB correction unit 30, and the WB correction unit 30 performs WB correction based on the input and the previous digital signal.
Subsequent processing is performed through a color matrix correction, a γ correction, an LPF color separation, a YC conversion, and image processing, as in a normal electronic camera. Are multiplexed by the multiplexer 41 and output as a Y component. In addition, the image processing unit outputs color component data (UV).

The operation of the electronic camera according to the present invention configured as described above will be described with reference to FIG. FIG. 2 is a flowchart showing the operation of the electronic camera according to one embodiment of the present invention.

First, as shown in FIG. 3, an image is divided into minute regions (also called "blocks") (step A).
1). In FIG. 3, each minute area (for example, minute area 0
0, minute region 01, minute region 10, and minute region 11) include 6 × 6 = 36 pixels. In this case, it is preferable to divide the image so that the number of micro regions is the same as the number of pixels of the thumbnail image, or an integer multiple of the number of pixels of the thumbnail image or a reciprocal thereof. Next, an integrated value of R, Gr, Gb, and B in the minute area is obtained, and an average value thereof is calculated (step A).
2). Here, R, Gr, G obtained by averaging these values
b and B are written in the DRAM to be thumbnail image data. Then, first, Y (luminance) is calculated for the minute area (step A3), and it is determined whether the luminance is within a predetermined value range (20 ≦ Y ≦ 190 in this embodiment) (step A4). If the luminance is not within the predetermined range, that is, if it is determined that the luminance is too low or too high, this area is set to non-selection. In step A4, if the luminance is within a predetermined range, B / G,
R / G is calculated (step A5). As a result, the color coordinate system becomes B / G and R / G. FIG. 4 shows a display example using this color coordinate system. The B / G and R / G coordinate systems have a characteristic that an approximate white color temperature curve becomes a straight line. Here, the determination of high saturation is determined by whether or not the portion is indicated by the hatched portion in the figure.

Here, it is determined whether at least one of B / G or R / G exceeds a predetermined value (step A).
6) If it exceeds the predetermined value, it is determined that the color saturation is high and the area is not selected (step A9). If B / G and R / G are equal to or smaller than the predetermined values in step A6, the color space is determined (step A7). The following criteria are used to determine the color space. For example, (1) If the area is a blue color space, it is not selected. (2) If the area is a lawn color space, it is not selected. (3) If the area is a white color space, it is selected. As described above, selection or non-selection of a region is determined according to the color space corresponding to the region. In this case, the position of each determination area in the color space is as shown in FIG. Then, for the selected block, the number of blocks is incremented, and B / G and R / G are added (step A8). Then, the operations from step A2 to step A8 are repeated until the final block is reached (step A10). When the processing of the final block is completed, the average value of B / G and R / G is calculated (step A1).
1).

As described above, according to the present invention, the image area is divided into minute areas, and then the white balance is adjusted by judging the luminance, the saturation, and further the color space. And a good white balance can be obtained even when there is no white in the photographing subject.

The present invention is not limited to the above embodiments of the present invention, and it is needless to say that various modifications can be made without departing from the spirit of the present invention.

[0015]

As described above, according to the present invention, when white balance is adjusted as in the prior art, there is a possibility that the white balance is largely shifted without "white" basically. Was. On the other hand, in the present invention, first, the image area is divided into minute areas, and selection or non-selection of the minute area is determined under predetermined conditions (luminance, saturation, color space, etc.), and the selected area is selected. Based on the information of the minute area
Since the white balance is adjusted, the white determination accuracy is improved, and a good white balance can be obtained even when there is no white in the photographed subject.

[Brief description of the drawings]

FIG. 1 is a schematic block diagram of an electronic camera according to the present invention, showing processing blocks from imaging to image processing.

FIG. 2 is a flowchart showing an operation of the electronic camera according to one embodiment of the present invention.

FIG. 3 is a diagram showing an example of division when an image is divided into minute regions.

FIG. 4 is a diagram showing a display example in an RGB coordinate system.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 11 ... Lens 12 ... CCD 13 ... Amplifier 14 ... A / D converter 20 ... Micro area integrator 21 ... SDRAM 22 ... Image processing part 25 ... WB evaluation value calculation part 26 ... WB detection part 30 ... WB correction part 40 ... Brightness Signal processing unit 41: Multiplexer

Claims (8)

[Claims] An imaging unit configured to convert a signal of a subject into an electric signal and output an analog image signal; and A configured to convert the analog image signal into a digital image signal.
/ D conversion means, image division means for dividing the digital image signal into a plurality of areas, selection means for selecting or non-selecting the plurality of divided areas according to a predetermined criterion, Using the information of the plurality of selected areas, W
An electronic camera, comprising: WB detecting means for obtaining a B correction value. 2. The electronic camera according to claim 1, wherein the number of divisions set by the image dividing means is n times or 1 / m (n and m are positive integers) of the number of pixels of the thumbnail image. An electronic camera characterized by the following. 3. The electronic camera according to claim 1, wherein said selection means further comprises a block brightness calculation means, and the selection or non-selection is determined according to the brightness value calculated by said block brightness calculation means. Electronic camera featuring. 4. The electronic camera according to claim 1, wherein said selection means further comprises a block saturation calculation means, and determines selection or non-selection according to the output. 5. The electronic camera according to claim 1, wherein the selection unit has area information of a predetermined color space, and determines whether to select or not to select according to whether or not the color space area is included. Electronic camera featuring. 6. The electronic camera according to claim 5, wherein said color space area information is a substantially blue color space, and said selecting means does not select an area included in said area. camera. 7. The electronic camera according to claim 5, wherein said color space area information is substantially a lawn color space, and said selection means does not select an area included in said area. camera. 8. The electronic camera according to claim 5, wherein said color space area information is a substantially white color space, and said selection means selects an area included in said area. .