KR20100019222A - Method and apparatus for controlling automatic white balance using optical sensor, and digital photographing apparatus using thereof - Google Patents

Abstract

PURPOSE: An automatic white balance adjusting method, a device thereof, and a digital photographing device using the same are provided to enable white balance according to the color temperature of an external light source. CONSTITUTION: A digital signal processor(320) controls the white balance of an input image based on an AWB(Automatic White Balance) coefficient value. The digital signal processor comprises a mapping table(323), a color temperature mapping part(322) and an AWB coefficient value decision part(324). The mapping table stores the AWB coefficient value corresponding to the color temperature of the predetermined light source. The color temperature mapping part maps the AWB coefficient value corresponding to the color temperature' with reference to the mapping table. According to the mapping result of the color temperature mapping part, the AWB coefficient value decision part decides the AWB coefficient value.

Description

Method and apparatus for controlling automatic white balance using an optical sensor and a digital photographing apparatus using the same

The present invention relates to an automatic white balance adjusting method and apparatus, and more particularly, to an automatic white balance adjusting method and apparatus using an optical sensor, and a digital photographing apparatus using the same.

In general, the human eye feels white under any light source (for example, sunlight, fluorescent light, incandescent light, etc.) but becomes red or blue depending on the light source when viewed through a camera's image tube. This is due to the color temperature of the light source, and high color temperature results in a blue color, and low color results in a red color. Therefore, the image processing device generally displays the final desired image by mixing three colors of red, green, and blue (R, G, B), and when the colors on the screen do not match, the original natural color of the object In addition, the deformed color is displayed to blur the visual characteristics of the human, and may be recognized as a significant shortcoming of the deterioration of the image output device itself.

If you adjust a white subject to appear white under a certain light source, other colors can also be reproduced correctly. This adjustment is called white balance adjustment.

In general, in order to compensate for the same color difference caused by different color temperatures of different light sources, a method called automatic white balance (AWB) is used in most imaging devices, for example, a camera and a camcorder.

The automatic white balance method means that the color average value of the screen is assumed to be white and the color average value is shifted to white regardless of a change in the light source.

The conventional automatic white balance method converts image data generated through an image sensor into color signals R, G, and B, and adjusts gains of R and B in the color signals. When the adjusted data is converted into a color gamut by the luminance Y and the color difference signals Cr and Cb, the color difference signal of one screen is integrated and the average value is extracted, and this average value is assumed to be a white value. When the white value is changed by the change of the external light source, the calculated gain of R and B is calculated, and the white balance is adjusted by adjusting the gain of R and B for the change. Therefore, in order to shift the average value to the white value, that is, the origin of the Cr and Cb axes, the gain for R and B is adjusted to move the average value for the color difference signal to the origin.

However, in the conventional automatic white balance method, it is difficult to accurately reflect the change in the light source by specifying the AWB coefficient according to the change of the external light source or by changing the AWB coefficient by comparing the pixels operating in response to the light source change. There was a problem that the amount of calculation was large by comparison.

The present invention has been made to solve the above problems of the conventional automatic white balance method, by implementing a white balance according to the color temperature of the external light source, an automatic white balance adjustment method and apparatus using an optical sensor having accurate AWB performance The purpose is to provide.

Another object is to provide a digital photographing apparatus using the same.

In order to solve the above technical problem, the automatic white balance adjusting method using an optical sensor according to an embodiment of the present invention comprises the steps of detecting the color temperature of a predetermined light source using the optical sensor; Mapping AWB coefficient values corresponding to the detected color temperature with reference to a mapping table storing AWB coefficient values corresponding to color temperatures; And determining an AWB coefficient value according to the mapping result and adjusting a white balance of the input image based on the determined AWB coefficient value.

Preferably, the method further comprises the step of receiving A / D conversion of the resistance value according to the wavelength of the light source.

In order to achieve the above technical problem, the automatic white balance adjusting apparatus using the optical sensor according to another embodiment of the present invention includes a digital signal processor for adjusting the white balance of the input image based on the AWB coefficient value,

The digital signal processing unit may include: a mapping table for storing AWB coefficient values corresponding to color temperatures of predetermined light sources; A color temperature mapping unit configured to receive a color temperature of a predetermined light source from the optical sensor and map an AWB coefficient value corresponding to the detected color temperature with reference to the mapping table; And an AWB coefficient value determination unit that determines an AWB coefficient value according to a mapping result of the color temperature mapping unit.

Preferably, the digital signal processing unit further includes an A / D conversion unit which receives the resistance value according to the wavelength of the light source and performs A / D conversion to provide the color temperature mapping unit.

According to another aspect of the present invention, there is provided a digital photographing apparatus having an automatic white balance function, the color temperature detecting unit detecting a color temperature of a predetermined light source; The AWB coefficient value corresponding to the detected color temperature is mapped with reference to a mapping table storing the AWB coefficient value corresponding to the color temperature detected by the color temperature detection unit, and the digital value determines the AWB coefficient value according to the mapping result. A signal processor; And an automatic gain adjuster for adjusting a white balance of an image output from the image sensor by using the AWB coefficient value output from the digital signal processor.

Preferably, the color temperature detection unit is characterized in that it comprises an optical sensor.

Preferably, the digital signal processing unit receives the resistance value according to the wavelength of the light source from the optical sensor and performs A / D conversion, and the mapping table stores the AWB coefficient value according to the A / D converted resistance value. It features.

The automatic white balance adjustment method using the optical sensor according to an embodiment of the present invention can obtain accurate AWB performance by implementing the white balance according to the detected color temperature by detecting the color temperature of the external light source.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings. In the following description, only parts necessary for understanding the operation according to the present invention will be described, and descriptions of other parts may be omitted so as not to distract from the gist of the present invention.

In addition, terms and words used in the following description and claims should not be construed to be limited to ordinary or dictionary meanings, but are to be construed in a manner consistent with the technical idea of the present invention As well as the concept.

1 is a schematic block diagram of an automatic white balance adjusting device according to the prior art.

1 is a view illustrating a structure of a conventional video camera. The conventional video camera includes a signal input unit 10 that receives an image of a subject and converts the image into an electrical signal, and converts an analog signal into a digital signal. The digital conversion unit, each of the digitally converted red, green, and blue signals is composed of one frame, and the automatic white balance coefficient is obtained in response to the output frames of the video signal processing unit 30 and the video signal processing unit for gamma correction. In response to the output of the AWB control unit 40 and the video signal processing unit 30 which feeds back the coefficient value to the video signal processing unit 30, an image output unit which changes a signal to match the display device to be used and outputs it to the display device. It consists of 50.

First, the image signal of the subject passing through the lens is applied to the image sensor to be converted into an electrical signal. Each image sensor recognizes only a color signal of either red, green, or blue. Next, the color signals are subjected to analog-to-digital conversion through a sampling process, and are applied to the video signal processor 30 to form each frame. In addition, the video signal processing unit 30 performs gamma correction to correct distortion generated when displaying the video signal. Next, the AWB control unit 40 corresponding to the output of the video signal processing unit 30 compares the distributions of red, green, and blue included in the output of the video signal processing unit 30 to generate a white balance coefficient and again. The image signal is corrected by feeding back to the video signal processor 30.

2 is a schematic block diagram of another automatic white balance adjustment device according to the related art.

The automatic white balance circuit shown in FIG. 2 is configured to determine whether the auto white balance operation is activated in response to the output of the pixel comparing means 60 and the pixel comparing means 60 operating in response to the change of the light source. Whether to use the output of the coefficient determination means in response to the output of the selection means 70, the coefficient determination means 80 for generating the auto white balance coefficient in response to the output of the auto white balance selection means, and And a coefficient output means 90 for determining.

Here, when the auto white balance selecting means 70 is activated, the coefficient determining means 80 determines the AWB coefficient in response to the image data passing through the first pixel comparing means and the second pixel comparing means. The coefficient value determined by the coefficient determining means 80 is stored in the coefficient register after the multiplexer, fed back to the video signal processing means to adjust the color value for the current image frame, and then through the output means to fit the display device. Will be converted and output.

3 is a schematic block diagram of a digital photographing apparatus including an automatic white balance adjusting device 300 according to a change in a light source according to an exemplary embodiment.

Referring to FIG. 3, the digital photographing apparatus includes an image input unit 100, an automatic gain adjuster 200, an automatic white balance adjuster 300, and a display 400. The image input unit 100 includes a lens unit 110 and an image sensor 120, and the automatic white balance adjusting device 300 includes a color temperature detector 310 and a digital signal processor 320.

The lens unit 110 includes a zoom lens (not shown) that enlarges and reduces the magnification of the subject, a focus lens (not shown) that focuses on the subject, and an aperture (not shown) that adjusts the amount of light, thereby providing light from an external light source. Receives and processes the image. The image sensor 120 is used as a photographing element, accumulates the amount of light input through the lens unit 110, and photoelectrically converts the image photographed by the lens unit 110 into an electrical signal according to the accumulated amount of light. Here, the image sensor 120 may use a charge coupled device (CCD) or a complementary metal oxide semiconductor image sensor (CIS).

The automatic gain control unit 200 controls the gain of the signal output from the image sensor 110. For example, the gain of each signal is controlled in the image signals of R, G, and B output from the CCD. In a preferred embodiment of the present invention, the automatic gain adjuster 200 adjusts the white balance of the image output from the image sensor using the AWB coefficient value output from the digital signal processor.

The color temperature detector 310 detects a color temperature of an external light source at the time of photographing a specific subject using a digital photographing apparatus. Even when shooting the same subject, the apparent image captured by various light source conditions, such as under outdoor sunlight, cloudy days, under white lamps under indoor lighting, and under fluorescent lighting, can detect color temperatures of various external light sources. Thus, the AWB can be performed by dividing the above-described shooting conditions.

Preferably, the color temperature detector 310 is implemented by an optical sensor. The optical sensor may distinguish the type of the light source by outputting a different resistance value according to the wavelength of the light source.

The digital signal processor 320 adjusts the white balance of the input image based on the determined AWB coefficient value. In particular, the digital signal processing unit receives an AWB coefficient value corresponding to the color temperature of the light source, and receives the color temperature of the light source from the color temperature detection unit 310 and refers to the mapping table to obtain an AWB coefficient value corresponding to the color temperature. It consists of a color temperature mapping part to map, and an AWB coefficient value determination part which determines AWB coefficient value according to the mapping result of a color temperature mapping part. In a preferred embodiment of the present invention, the digital signal processor 320 feeds back the determined AWB coefficient value to the automatic gain control unit 200 to adjust the white balance of the input image. The digital signal processor which performs the conventional AWB adjustment detects white by receiving an image signal converted into a digital signal, calculates R, G, and B coefficients for white balance correction using the detected white, and applies it to the image signal. As a result, although a large amount of resources are consumed in calculating the change of the pixel to detect the white, the digital signal processor 320 according to the preferred embodiment of the present invention refers to the mapping table according to the detected color temperature, thereby providing the AWB coefficient value. Can be calculated simply.

A detailed configuration of the digital signal processor 320 will be described later with reference to FIG. 4.

The display unit 400 displays an image on which the white balance output from the digital signal processor 320 is performed. The display unit 400 may include a liquid crystal display panel (LCD), an organic light emitting display panel (OLED), an electrophoretic display panel (EDD), or the like.

4 is a schematic block diagram of the automatic white balance adjusting device 300 shown in FIG. 3.

Referring to FIG. 4, the automatic white balance adjusting device 300 includes a color temperature detector 310, an A / D converter 321, a color temperature mapper 322, a mapping table 323, and an AWB coefficient value determiner. 324.

 The color temperature detector 310 detects a color temperature of an external light source at the time of photographing a specific subject using a digital photographing apparatus. Preferably, the color temperature detector 310 is implemented as an optical sensor. The optical sensor may distinguish the type of the light source by outputting different resistance values according to the wavelength of the light source. In addition, the analog resistance value is provided to the A / D converter 321.

The A / D converter 321 outputs a digital value of the analog resistance value sampled to the color temperature mapping unit 322.

The color temperature mapping unit 322 maps the AWB coefficient values according to the color temperature with reference to the mapping table 323 storing the AWB coefficient values according to the digital values reflecting the color temperature. Here, the mapping table 323 prestores the AWB coefficient value according to the specific color temperature, which is preferably a white balance calculated value previously measured.

The AWB coefficient value determination unit 324 determines the AWB coefficient value according to the mapping result from the color temperature mapping unit 322. Then, the determined AWB coefficient value is fed back to the automatic gain adjusting unit 320 and applied to all pixels of the input image to adjust the white balance.

5 is a flowchart illustrating an automatic white balance adjustment method according to a light source change according to another exemplary embodiment of the present invention.

Referring to FIG. 5, in step 500, a color temperature according to an external light source is detected. Therefore, conventionally, in the case of natural light, indoors, incandescent lamps, color image detection is more accurately performed by detecting color temperature more accurately than performing automatic white balance with predetermined AWB coefficient values according to respective predetermined light sources. can do.

In step 502, reference is made to the color temperature / AWB coefficient value mapping table. In step 504, AWB coefficient values are mapped according to the detected color temperature. In step 506, AWB coefficient values are determined according to the mapping result. Thus, the AWB coefficient value appropriate for the color temperature of the current external light source can be determined. In step 508, the white balance of the input image signal is performed using the determined AWB coefficient value.

Meanwhile, the present invention can be embodied as computer readable codes on a computer readable recording medium. The computer-readable recording medium includes all kinds of recording devices in which data that can be read by a computer system is stored.

Examples of computer-readable recording media include ROM, RAM, CD-ROM, magnetic tape, floppy disks, optical data storage devices, and the like, which may also be implemented in the form of carrier waves (for example, transmission over the Internet). Include. The computer readable recording medium can also be distributed over network coupled computer systems so that the computer readable code is stored and executed in a distributed fashion. And functional programs, codes and code segments for implementing the present invention can be easily inferred by programmers in the art to which the present invention belongs.

So far I looked at the center of the preferred embodiment for the present invention. Those skilled in the art will understand that the present invention can be embodied in a modified form without departing from the essential characteristics of the present invention. Therefore, the disclosed embodiments should be considered in descriptive sense only and not for purposes of limitation. The scope of the present invention is shown not in the above description but in the claims, and all differences within the scope should be construed as being included in the present invention.

1 is a schematic block diagram of an automatic white balance adjusting device according to the prior art.

2 is a schematic block diagram of another automatic white balance adjustment device according to the related art.

3 is a schematic block diagram of a digital photographing apparatus including an automatic white balance adjusting device 300 according to a change in a light source according to an exemplary embodiment.

4 is a schematic block diagram of the automatic white balance adjusting device 300 shown in FIG. 3.

5 is a flowchart illustrating an automatic white balance adjustment method using an optical sensor according to another embodiment of the present invention.

<Explanation of symbols for the main parts of the drawings>

100: image input unit 110: lens unit

120: image sensor 200: automatic gain control unit

300: automatic white balance adjustment device 310: color temperature detection unit

320: digital signal processing unit

Claims (8)

As an automatic white balance adjustment method using an optical sensor, (a) detecting a color temperature of a predetermined light source using the optical sensor; (b) mapping an AWB coefficient value corresponding to the detected color temperature with reference to a mapping table storing the AWB coefficient value corresponding to the color temperature; And (c) determining an AWB coefficient value according to the mapping result, and adjusting a white balance of the input image based on the determined AWB coefficient value. The method of claim 1, And A / D conversion by receiving a resistance value according to the wavelength of the light source. A recording medium having recorded thereon a program for executing a method according to any one of claims 1 and 2 on a computer. Automatic white balance control device using light sensor, A digital signal processor for adjusting a white balance of the input image based on the AWB coefficient value; The digital signal processing unit, A mapping table for storing AWB coefficient values corresponding to a color temperature of a predetermined light source; A color temperature mapping unit configured to receive a color temperature of a predetermined light source from the optical sensor and map an AWB coefficient value corresponding to the detected color temperature with reference to the mapping table; And And an AWB coefficient value determination unit that determines an AWB coefficient value according to a mapping result of the color temperature mapping unit. The method of claim 4, wherein The digital signal processing unit, And an A / D conversion unit for receiving the resistance value according to the wavelength of the light source and providing the A / D conversion unit to provide the color temperature mapping unit. In a digital photographing apparatus having an automatic white balance function, A color temperature detector detecting a color temperature of a predetermined light source; The AWB coefficient value corresponding to the detected color temperature is mapped with reference to the mapping table storing the AWB coefficient value corresponding to the color temperature detected by the color temperature detector, and the digital value for determining the AWB coefficient value according to the mapping result is determined. A signal processor; And And an automatic gain adjuster for adjusting a white balance of an image output from an image sensor by using the AWB coefficient value output from the digital signal processor. The method of claim 6, The color temperature detection unit, Digital imaging device comprising a light sensor. The method of claim 7, wherein The digital signal processing unit, A / D conversion by receiving the resistance value according to the wavelength of the light source from the optical sensor, The mapping table stores an AWB coefficient value according to the A / D converted resistance value.

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