KR101356516B1 - Apparatus and method for compensation of white balance - Google Patents

Abstract

The present invention relates to an apparatus and method for compensating white balance by an ambient light source, the method comprising: detecting a color temperature and a white region by measuring R, G, and B light amounts from an external light source; Calculating a color temperature change trajectory by about a shift of R, G, and B color coordinates by calculating a difference value between the detected color temperature of the external light source and the set color temperature of the reference white balance; Correcting a color temperature by using a white balance gain control voltage value corresponding to the calculated change degree of the R, G, B color coordinates; And displaying the input image screen by maintaining the corrected color temperature at a constant level, and providing a clear image to a user in various environments by using a white compensation method considering color temperature shift caused by a light source surrounding the TV. .

Color temperature, white balance

Description

Apparatus and method for compensation of white balance}

The present invention relates to a display device, and more particularly to a white compensation display device and method by the color temperature shift of the ambient light source.

In general, the human eye has a certain degree of adaptability to recognize the color of the reflector even if the illumination is different, but since the image tube of the TV camera does not have such an adaptation, a device is required to compensate for this. Attach an optical filter in front of the camera with an energy spectral distribution such as C or D65 light as a reference to give a consistent color to objects regardless of background light, such as natural light, C light, or D65 light. The video signal is processed by adjusting the RGB gain so that the color coordinate of is equal to the color coordinate of the reference light.

In the conventional TV or monitor, since the color reproduction characteristics are based on white, different color coordinates reproduced for the same image signal are different when the reference white coordinates are different. In fact, the white color of a TV or monitor product does not consider the ambient light source at all, which causes a problem that the color reproduction characteristics are gradually changed by the ambient light source.

The present invention is to solve the above problems, the object is to provide a fresh white feeling to the user without being affected by the ambient light source according to the place or time by resetting the white transition curve by measuring the ambient light source.

White balance compensation apparatus of the present invention for achieving the above object is an RGB color sensor unit for detecting the color temperature and the white region by measuring the R, G, B light amount from an external light source; A color temperature calculator calculating a difference between a color temperature of the detected external light source and a color temperature of a reference white balance to calculate a color temperature change trajectory by a shift of R, G and B color coordinates; A white gain compensator for correcting a color temperature with a white balance gain control value corresponding to the calculated degree of change in the R, G, and B color coordinates; A control unit controlling R, G, B voltage values to correct the color temperature in the white gain compensator; And a memory configured to store R, G, B color coordinates and R, G, B voltage values of white corresponding to the set color temperature as a look-up table.

The RGB color sensor unit may detect a color temperature of an external light source and a white region of an R, G, and B distribution curve using a color matching function.

The RGB color sensor unit may include a digital camera having a spectral sensitivity characteristic filter.

The white gain compensator adjusts a correction range of the color temperature to a change trajectory of 2,500 to 10,000 K °.

The controller may set the white balance adjusted R, G, and B color coordinates to the current reference color temperature.

The memory may be configured to update and store R, G, and B color coordinates of the corrected color temperature to the color temperature of the set reference white balance.

In addition, the present invention provides a white balance compensation method using an ambient light source, the method comprising: detecting the color temperature and the white region by measuring the R, G, B light amount from an external light source; Calculating a color temperature change trajectory by about a shift of R, G, and B color coordinates by calculating a difference value between the detected color temperature of the external light source and the set color temperature of the reference white balance; Correcting a color temperature by using a white balance gain control voltage value corresponding to the calculated change degree of the R, G, B color coordinates; And displaying the input image screen by keeping the corrected color temperature constant.

The method may further include updating and storing the corrected color coordinates of the R, G, and B color coordinates to the set color temperature of the reference white balance.

The white balance gain control voltage value is a Cb, Cr gain value.

The corrected color temperature is characterized by having a correction range of 2,500 ~ 10,000K °.

The present invention provides a white compensation method in consideration of color temperature shift due to a light source surrounding a TV, thereby providing a user with a clear image even in various environments.

The objects, features and advantages of the present invention will be more readily understood by reference to the accompanying drawings and the following detailed description. In the following description of the present invention, a detailed description of known functions and configurations incorporated herein will be omitted when it may make the subject matter of the present invention rather unclear.

1 is an exemplary diagram illustrating UV chromaticity coordinates and white values according to RGB gains.

YUV was developed for PAL analog video, but digital video is also used for the European video standard CCIR601. YUV is a color system in which the human eye is most sensitive to light. Y represents brightness, luminance, and U and V represent chromaticity. The relationship between the RGB color coordinates and the equation (1).

Y = 0.299R + 0.587G + 0.114B

U = B-Y

V = R-Y

Here, the standard white point (W / P) according to the color temperature is D65 or 6500K. The color temperature depends on how much the red, green, and blue gains are mixed.

2 is an exemplary view showing a color temperature variation curve according to white application.

In general, the luminance increases as the color temperature increases, but the luminance value decreases due to the characteristics of human vision despite the high color temperature in any section. When the chromaticity temperature of 11,000K is maintained until the section (a) in FIG. 2, the luminance is maintained at a constant brightness. Section (a ~ b) is a section of the instrument, and when the color temperature rises to 15,000K, the brightness also has a constant slope and the brightness increases. (b ~ c) section is the application section when the color temperature is 15,000K, the brightness is stable with high brightness. (c) In the abnormal section, the color temperature decreases as the luminance increases according to the optical characteristics.

3 is a diagram illustrating an internal configuration of a white compensation display device based on a color temperature difference of an ambient light source according to the present invention.

RGB color sensor unit 30 measures the amount of R, G, B light for the external illumination. At this time, the white region is detected from the R, G, B distribution curves for the color temperature and the wavelength of the light of the external light source measured by the color matching function for matching the color and temperature proportional to the brightness. The RGB color sensor unit 30 can be easily implemented using a digital camera having a spectral sensitivity characteristic filter.

The color temperature calculation unit 32 calculates a difference value between the color temperature of the external light source measured by the RGB color sensor unit 30 and the color temperature of the reference white balance set at the factory to calculate the color temperature change trajectory of the R, G, B color coordinates. Calculate the degree of shift.

The white gain compensator 34 corrects the color temperature by applying a white balance gain control signal corresponding to the degree of change of the R, G, and B color coordinates calculated by the color temperature calculator 32. The white balance correction range according to the color temperature change has a color temperature change trajectory of 2,500 to 10,000K °. At this time, the R gray is fixed and the color temperature is adjusted in such a manner as to control the upper limit of the color coordinate values of the G gray and the B gray.

The display unit 36 displays an output image in which the color temperature is corrected by the white gain compensator 34.

The controller 38 outputs, to the white gain compensator 34, a voltage control value for adjusting gains for R, G, and B by the color temperature difference with the external light source calculated by the color temperature calculator 32. After adjusting the white balance, set the R, G, B color coordinates obtained from the R, G, B voltage values corresponding to the reference white to the current reference color temperature.

The memory 39 stores corresponding white R, G, B color coordinates and R, G, B voltage values for all color temperatures on a MPCD (Minimum Perceptible Color Difference) curve as a look-up table. In addition, the controller 38 updates the R, G, and B color coordinate values set to the current reference color temperature after the white balance is adjusted.

4 is an exemplary view illustrating a color shift by an ambient light source according to an exemplary embodiment of the present invention.

The color seen in the D65 (6500K, 8MPCD) light source must be shifted by the amount of the arrow on the color temperature axis of the light source by the influence of the tungsten light source (Tungsten, 3200K) to recognize the same color in human vision. In this standard light source, a specific color is mapped to another light source, and a color that is recognized as the same color in human vision is called a corresponding color.

For this reason, if the white compensation gain according to the ambient light source is the same, it means that the white of the TV screen can be seen sufficiently different.If the color value of the light source is measured, the corresponding color value of the corresponding white can be calculated or lookuptabled to compensate. Regardless of the light source, the user can feel crisp and fresh white with the same color.

5 is an exemplary diagram illustrating a change in white gain by a peripheral light source according to an embodiment of the present invention in Cb Cr coordinates.

In the present invention, by adding the Cb, Cr values for the signal close to the origin in the UV coordinates, the color temperature is increased by changing the R, G, B gain values. At this time, if the gain value of the blue color signal is increased, the sharpness increases due to human visual characteristics, thereby adding more Cb values.

In the D65 light source, the reference white (Cb ', Cr') coordinate system is shifted to the (Cb ", Cr") white coordinate system by the tungsten light source. .

6 is a flowchart illustrating a white compensation method of an input image based on a color temperature difference of an ambient light source according to the present invention.

The amount of light of the external light source according to the change of the ambient light source is sensed (S601).

The color temperature and the white region are detected by measuring the amount of R, G, and B light from the sensed external light source (S603). At this time, the white region is detected from the R, G, and B distribution curves for the color temperature of the external light source and the wavelength of the light measured by a color matching function for matching color and temperature proportional to brightness.

By calculating a difference value between the detected color temperature of the external light source and the set color temperature of the reference white balance, the color temperature change trajectory is calculated as the shift of the R, G, and B color coordinates (S605).

The white gain maintaining a constant color temperature is compensated by correcting the color temperature using the calculated white balance gain control voltage value corresponding to the calculated change degree of the R, G, B color coordinates (S607).

The terminology used in the present invention is defined in consideration of the functions of the present invention, and it may vary depending on the intention or custom of a technician working in the field. Therefore, .

The present invention is not limited to the above-described embodiments and various changes and modifications may be made by those skilled in the art.

1 is an exemplary diagram illustrating UV chromaticity coordinates and white values according to RGB gains.

Figure 2 is an exemplary view showing a color temperature variation curve according to the fresh white application.

3 is a diagram illustrating an internal configuration of a white compensation display device based on a color temperature difference of an ambient light source according to the present invention.

Figure 4 is an exemplary view showing a color shift by the ambient light source according to an embodiment of the present invention.

5 is an exemplary diagram showing a change in white gain by a peripheral light source according to an embodiment of the present invention in Cb Cr coordinates.

6 is a flowchart illustrating a white compensation method of an input image based on a color temperature difference of an ambient light source according to the present invention.

Description of the Related Art [0002]

30. RGB color sensor 32. Color temperature calculator

34. White Gain Compensator 36. Display

38. Controller 39. Memory

Claims (10)

Storing white R, G, B color coordinates and R, G, B voltage values corresponding to all color temperatures on a Minimal Perceptible Color Difference (MPCD) curve as a look-up table; Detecting a color temperature and a white region by measuring R, G, and B light amounts from an external light source; Calculating a color temperature change trajectory by about a shift of R, G, and B color coordinates by calculating a difference value between the detected color temperature of the external light source and the set color temperature of the reference white balance; Correcting a color temperature using a white balance gain control voltage value corresponding to the calculated degree of movement of the R, G, B color coordinates based on the stored lookup table, wherein the R gray is fixed and the G gray and the B gray The upper limit of the color coordinate value of is controlled; And And displaying the input image screen by maintaining the corrected color temperature at a constant level. The method according to claim 1, And updating and storing the corrected color coordinates of the R, G, and B color coordinates with the set color temperature of the reference white balance. The method according to claim 1, The white balance gain control voltage value is a Cb, Cr gain value, the white balance compensation method by the ambient light source. The method according to claim 1, The corrected color temperature has a correction range of 2,500 ~ 10,000K ° White balance compensation method by the ambient light source. A memory for storing white R, G, B color coordinates and R, G, B voltage values corresponding to all color temperatures on a MPCD curve as a look-up table; An RGB color sensor unit measuring R, G, and B light amounts from an external light source to detect color temperature and white region; A color temperature calculator calculating a difference between a color temperature of the detected external light source and a color temperature of a reference white balance to calculate a color temperature change trajectory by a shift of R, G and B color coordinates; A white gain compensator for correcting a color temperature with a white balance gain control value corresponding to the calculated degree of movement of the R, G, B color coordinates based on the stored lookup table, wherein the R gray is fixed and the G gray and B gray The upper limit of the color coordinate value of is controlled; And And a controller configured to control R, G, and B voltage values to correct the color temperature in the white gain compensator. 6. The method of claim 5, And the RGB color sensor unit detects a color temperature of an external light source and a white region of an R, G, and B distribution curve by using a color matching function. The method according to claim 6, And the RGB color sensor unit comprises a digital camera having a spectral sensitivity characteristic filter. 6. The method of claim 5, And the white gain compensator adjusts a correction range of the color temperature to a change trajectory of 2,500 to 10,000 K °. 6. The method of claim 5, And the control unit sets the white balance adjusted R, G, B color coordinates to the current reference color temperature. 6. The method of claim 5, And the memory updates and stores the R, G, and B color coordinates of the corrected color temperature to the set color temperature of the reference white balance.

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