KR20070087447A - Method and device for detecting color temperature - Google Patents

Abstract

A method and an apparatus for detecting a color temperature are provided to detect the color temperature in real time without a high error in an MCU(Micro Control Unit) of low performance. A region discriminating unit(130) receives pixel data in which an electric image signal inputted from an image sensor is interpolated, and selectively outputs only pixel data included in a predetermined color temperature detection region. A data collecting unit(135) outputs a channel-classified accumulation value, in which channel-classified data values of an RGB color for the pixel data inputted from the region discriminating unit(130) are accumulated and added, by each image frame unit. An MCU(140) stores light source color rate values according to color temperatures of two or more reference light sources previously selected, and calculates an input color rate value from the channel-classified accumulation values of each image frame unit inputted from the data collecting unit(135). The MCU(140) detects a color temperature corresponding to an input image by using distance proportion relation between cross points where straight lines, which have a uniform angle with a reference line formed by using the light source color rate values of the two predetermined reference light sources and pass through the input color rate value and the light source color rate values, are joined with a predetermined color temperature discrimination line. The light source color rate values are an average rate of a red data value for a green data value of the input image in the reference light sources and an average rate of a blue data value for the green data value.

Description

Method and device for detecting color temperature

1 is a block diagram illustrating an image signal processor capable of detecting a color temperature according to an exemplary embodiment of the present invention.

2 is a graph showing blackbody radiation curves and color temperature detection (CTD) regions.

3 is a view showing a color temperature determination line in a color coordinate system according to an embodiment of the present invention.

4 and 5 are views showing a color temperature detection method according to an embodiment of the present invention using the color temperature discrimination line shown in FIG.

6 is a flowchart illustrating a color temperature detection method according to an exemplary embodiment of the present invention.

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

100: image signal processor

110: image sensor

120: interpolator

130: region determination unit

135: data collector

140: MCU (Micro Control Unit)

150: gain control unit

160: the image processing unit

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to color temperature detection, and more particularly, to a method and apparatus for detecting color temperature in an imaging apparatus.

In general, the color that a person feels is recognized as the same color even if the light source changes due to the action of the cerebrum in addition to the physical stimulus. That is, even when the light source changes from a blue light source (for example, a fluorescent lamp) to a red light source (for example, an incandescent lamp), white is recognized as white.

However, in the case of the imaging device, color difference is generated by reproducing and storing the reflected light of a given color temperature as it is according to the light source. That is, the same object is reflected differently when placed on different light sources because the color temperature of each light source is different. For example, when a white object is placed on a light source of low color temperature, the reflected light becomes red. On the contrary, when a white object is placed on a light source of high color temperature, the reflected light becomes blue.

Therefore, in order to compensate for the color difference caused by different color temperatures of various light sources, most imaging devices (eg, cameras, etc.) use a method called Automatic White Balance (AWB). The automatic white balance function corrects the influence of the color temperature of the light source scanned on the subject when the image of the subject is formed on the image sensor. Therefore, it is necessary to detect the color temperature of the input image.

However, according to the conventional method, there was a burden of adding a separate hardware such as a color temperature measuring device to detect the color temperature, and even when the software is implemented, the algorithm is applied to obtain the performance as the color temperature measuring device. More elaborate configuration was required. After all, this means that the amount of computation for color temperature detection is increased, which puts a heavy burden on the microcontrol unit (MCU), which has to perform various functions such as automatic white balance adjustment and auto focus adjustment while controlling the overall image signal processor. There was a problem.

Accordingly, an object of the present invention is to provide a color temperature detection method and apparatus that can reduce the burden on the MCU by minimizing the amount of calculation according to the color temperature detection.

In addition, another object of the present invention is to provide a color temperature detection method and apparatus capable of real-time detection of color temperature without significant error even in a low-performance MCU.

In addition, another object of the present invention is to provide a color temperature detection method and apparatus which can reduce the manufacturing cost of the image signal processor by simply implementing in software in the image signal processor without adding additional hardware for color temperature detection It is to provide.

Other objects of the present invention will be readily understood through the following description.

According to an aspect of the present invention, there is provided an electronic image signal input from an image sensor, comprising: an area determining unit configured to selectively receive only pixel data included in a preset color temperature detection area by receiving interpolated pixel data; A data collector outputting a channel-specific cumulative value obtained by accumulating and summing data values of each channel of red (R), green (B), and blue (B) with respect to pixel data input from the area determination unit in each image frame unit. ; And store respective light source color ratio values according to color temperatures of two or more preselected reference light sources, calculate an input color ratio value from a cumulative value for each channel of each image frame unit input from the data collector, It forms a constant angle with the reference line formed by using the light source color ratio values of the two reference light sources, and uses the distance proportional relationship between the intersection points where the input color ratio values and the straight lines passing through the respective light source color ratio values meet a predetermined color temperature discrimination line. Accordingly, an image signal processor capable of detecting a color temperature including a micro control unit (MCU) for detecting a color temperature corresponding to an input image may be provided. Here, the light source color ratio value is an average ratio (R / G ratio) of the red data value to the green data value of the input image of the reference light source and the average ratio of the blue data value to the green data value (B / G ratio).

The area determining unit may include an achromatic pixel extraction filter, and the color temperature detection area may be an area corresponding to the achromatic pixel data.

Here, the reference line according to the present invention may be a straight line connecting the light source color ratio value of the reference light source having the highest color temperature and the light source color ratio value of the reference light source having the lowest color temperature.

Here, the data collector calculates the number of pixel data input from the area discriminator in each image frame unit, and the MCU calculates a first ratio obtained by dividing a cumulative value for red data by a cumulative value for green data among the cumulative values for each channel. The second ratio is calculated by dividing the cumulative value for the blue data by the cumulative value for the green data, and the input color ratio value is the average value of the first ratio and the second ratio divided by the number of pixel data input from the area discriminator. Can be.

Here, when the color temperature discrimination line according to the present invention is a reference line, two points existing at the intersection point corresponding to the input color ratio value and the shortest distance among the intersection points corresponding to the input color ratio value and each light source color ratio value. The color temperature can be detected using a distance proportional relationship between two intersections. In this case, the predetermined angle formed with the reference line may be, for example, 90 °.

Here, when the color temperature determination line is a vertical line or a horizontal line in which the ratio of the blue data value to the green data value or the ratio of the red data value to the green data value is set to 0, the intersection point and the angle corresponding to the input color ratio value The color temperature may be detected by using a distance proportional relationship between an intersection corresponding to the input color ratio value and two intersection points existing at the shortest distance among the intersection points corresponding to the light source color ratio value.

Here, the distance proportional relationship may be normalized and calculated by the MCU.

According to another aspect of the invention, (a) storing each light source color ratio value according to the color temperature of the two or more pre-selected reference light sources; (b) receiving the interpolated pixel data of the electrical image signal input from the image sensor and selectively outputting only pixel data included in a preset color temperature detection area; (c) accumulating and summing data values for each channel of red (R), green (B), and blue (B) for the selectively output pixel data to generate a cumulative value for each channel in units of image frames; (d) calculating an input color ratio value of each image frame unit from a cumulative value for each channel; (e) The distance between the intersection points where the straight lines passing through the input color ratio value and the light source color ratio value meet a predetermined color temperature discrimination line at a constant angle with the reference line formed by using the light source color ratio values of the two reference light sources. A color temperature detection method in an image signal processor may be provided that includes detecting a color temperature corresponding to an input image using a proportional relationship. Here, the light source color ratio value is an average ratio (R / G ratio) of the red data value to the green data value of the input image in the reference light source and the average ratio of the blue data value to the green data value (B / G ratio).

Here, the reference line according to the present invention may be a straight line connecting the light source color ratio value of the reference light source having the highest color temperature and the light source color ratio value of the reference light source having the lowest color temperature.

In addition, the color temperature detection method according to the present invention comprises the steps of (f) calculating the number of selectively output pixel data before each step (d) in each image frame unit; And (g) calculating a first ratio of a cumulative value for red data divided by a cumulative value for green data and a second ratio of a cumulative value for blue data divided by a cumulative value for green data. Further, the input color ratio may be an average value obtained by dividing the first ratio and the second ratio by the number of selectively output pixel data.

Here, when the color temperature discrimination line according to the present invention is a reference line, two points existing at the intersection point corresponding to the input color ratio value and the shortest distance among the intersection points corresponding to the input color ratio value and each light source color ratio value. The color temperature can be detected using a distance proportional relationship between two intersections.

Here, when the color temperature determination line is a vertical line or a horizontal line in which the ratio of the blue data value to the green data value or the ratio of the red data value to the green data value is set to 0, the intersection point and the angle corresponding to the input color ratio value The color temperature may be detected by using a distance proportional relationship between an intersection corresponding to the input color ratio value and two intersection points existing at the shortest distance among the intersection points corresponding to the light source color ratio value.

The following discussion illustrates the principles of the present invention. Accordingly, all detailed descriptions enumerating the principles and embodiments of the present invention should be understood to include structural and functional equivalents. In the following description of the present invention, if it is determined that the detailed description of the related known technology may obscure the gist of the present invention, the detailed description thereof will be omitted.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings, and the same or corresponding components will be denoted by the same reference numerals regardless of the reference numerals and redundant description thereof will be omitted.

In addition, the method and apparatus for detecting color temperature according to the present invention may be applied without limitation to any image capturing apparatus that receives an external image and displays it on a display unit, such as a portable terminal having a camera function or a digital camera.

1 is a block diagram illustrating an image signal processor capable of detecting color temperature according to an exemplary embodiment of the present invention, and FIG. 2 is a graph showing a blackbody radiation curve and a color temperature detection (CTD) region.

The blackbody radiation curve of FIG. 2 connects the average values of the general R / G ratio and B / G ratio distribution for each light source in a color coordinate with R / G ratio and B / G ratio on both axes. Means good. The R / G ratio and B / G ratio are the ratios of the red (R) data values to the green (G) data values in the RGB image data and the blue (B) data values to the green (G) data values. Means percentage.

Referring to FIG. 1, an image signal processor (ISP) 100 according to the present invention includes an interpolator 120, an area discriminator 130, a data collector 135, an MCU 140, and a gain. The controller 150 may include an image processor 160, a converter 170, and an output unit 180.

The interpolator 120 interpolates an electrical image signal input from the image sensor 110 to process data of red (R), green (G), and blue (B) (hereinafter, abbreviated as 'RGB data'). To convert). For example, the interpolator 120 is an image signal of an R / Gr / Gb / B format of a n-bit (Bay Bayer) pattern of n (for example, 10 as a predetermined natural number) input from the image sensor 110. Can be converted into n-bit RGB data per channel. For this conversion, various filters (eg, 3 × 3, 5 × 5 filters, etc.) may be used depending on the algorithm used for the interpolation process.

The interpolated RGB data may be input to the area determiner 130 and the gain adjuster 150, respectively.

The area determining unit 130 receives interpolated RGB data in pixel units, and a color temperature detection area in which the input pixel is predefined (set according to a light source or set by a user) (CTD zone: Color). It is determined whether the pixel is included in the temperature detection zone. Achromatic pixel extraction filter such as a CTD zone filter or a white zone filter may be used to determine the detection area.

Using the achromatic pixel extraction filter, the area discrimination unit 130 extracts only achromatic data (hereinafter referred to as 'white pixel data') corresponding to the color temperature detection area (hatched portion of FIG. 2) of the received RGB data. can do. Therefore, the color temperature detection region to be selectively extracted may be defined in the achromatic pixel extraction filter.

In this case, when it is determined that the input pixel is a pixel in the CTD area, the area determination unit 130 inputs RGB data of the pixel to the data collection unit 135. In more detail, the area determining unit 130 calculates the R / G ratio and the B / G ratio of the RGB data that have passed through the interpolator 130 by one pixel, and positions the pixels in the color coordinate system as shown in FIG. 2. Is determined to exist in the preset color temperature detection area, the R, G, and B values of the corresponding pixel are transmitted to the data collector 135.

As described above, the present invention extracts only achromatic pixels from the RGB data through the area discriminator 130, thereby greatly reducing the amount of computation in estimating color temperature to be performed later. In addition, there is an effect that it is possible to prevent an error in color temperature estimation that may occur when color temperature estimation is performed using chromatic color pixels. Through this, the present invention can more accurately and quickly detect the color temperature of the input image.

The data collector 135 receives the R, G, and B values of the pixels determined as the white pixel data by the area determination unit 130, and sums them for each channel (that is, for each data of the R, G, and B components). do. Channel summation by the data collection unit 135 is performed for each frame. That is, the data collection unit 135 performs channel-specific summation for all data determined as white data among data constituting one frame of image, and performs channel-specific summation for the next frame in the same manner.

Here, the sum totaled for each channel may be stored in a manner of being updated in a corresponding register (not shown) in the image signal processor 100. That is, whenever the data collector 135 sums the R, G, and B values of each of the white pixel data included in any one frame for each channel, the previous summation value stored in the corresponding register is updated to the newly summed cumulative value. Can be. At this time, the sum value stored in the register is transmitted to the MCU 140 at the same time as the input of the white pixel data corresponding to the next frame is started, and is initialized to "0" again. Here, the sum value for one frame stored in the register immediately before the register value is initialized to "0" will be referred to as a cumulative value for each channel.

In this way, the cumulative channel-specific values calculated for each frame by the data collector 135 are input to the MCU 140 in parallel for each channel (see 'R Sum', 'G Sum' and 'B Sum' in FIG. 1).

In addition, the data collection unit 135 may add the number of white pixel data input from the area determining unit 130 to each of the image frames and transmit the sum to the MCU 140 (see 'Cnt' of FIG. 1). The number of white pixel data per image frame may be used when acquiring reference data to be described later.

The MCU (Micro Control Unit) 140 is responsible for the overall control of the image signal processor 100, and includes various functions (eg, an auto exposure function (AE) and an auto focus function (e.g. AF), auto white balance function (AWB), etc.).

In particular, the MCU 140 according to the present invention is predefined and embedded in the algorithm for color temperature detection. The MCU 140 acquires reference data, which will be described later, from the cumulative value for each channel and the number of white pixel data input from the data collector 135 using the color temperature detection algorithm (see description of FIGS. 4 and 5). Further, by analyzing the acquired reference data, the color temperature of the input image data can be detected. Such a color temperature detection method will be described in detail with reference to FIGS. 3 to 6.

The MCU 140 generates a gain value (hereinafter, referred to as a 'balance gain value') required to perform automatic white balance (AWB) using the detected color temperature, and performs image processing of the image processor 160 to be described later. Various setting values (hereinafter, referred to as 'image processing setting values') may be generated. The MCU 140 may transfer / control the balance gain value or the image processing setting value to the gain adjuster 150 or the image processor 160. However, in the present invention, since the method of detecting the color temperature of the input image is the main point, a detailed description of the method of generating the balance gain value and the image processing setting value will be omitted.

The gain controller 150 adjusts the R / G gain and the B / G gain of the RGB data received from the interpolator 120 using the balance gain value input from the MCU 140. In other words, the gain adjusting unit 150 multiplies the balanced gain value by the interpolated RGB data and outputs the multiplied gain. In this case, the gain-adjusted RGB data is input to the image processor 160.

The image processor 160 performs various image processing on the RGB data input by the image signal processor 100. For example, the image processor 160 may perform scaling of image data, gamma correction, color correction, or the like of the image data. Therefore, the image processor 160 may include a scaler, a gamma correction unit, an RGB image filter, a color correction matrix, and the like.

In addition, the image processor 150 may adjust the RGB image filter or the color correction matrix value by applying an image processing setting value according to the detected color temperature received from the MCU 140.

The RGB data processed by the image processor 160 is input to the converter 170. At this time, the gamma correction unit (not shown) in the image processing unit 160 converts the n-bit RGB data received into m (R, 8-bit RGB data, for example, a predetermined random number). The image data input to) may be m-bit RGB data.

The converter 170 converts the RGB data input from the image processor 160 into YUV data. The YUV data means a Y signal that is a luminance component and a C signal that is a chrominance component (ie, a Cr signal and a Cb signal). That is, the converter 170 separates the RGB data into Y and C signals, and the separated Y and C signals are input in parallel to the Y image processing block and the C image processing block, respectively, in the converter 170. Image processing. The YUV data passing through the Y image processing block and the C image processing block is input to the output unit 180.

The output unit 180 outputs the YUV data received from the converter 170 in synchronization with a clock signal of the image signal processor 100. If the YUV data output by the output unit 180 is 4: 2: 2 format data, two clock signals are required for one pixel, and thus, twice the clock signal of the image signal processor 100 is output. You will use it as a clock.

3 is a view showing a color temperature determination line in the color coordinate system according to an embodiment of the present invention, Figures 4 and 5 is a preferred embodiment of the present invention using the color temperature determination line shown in FIG. 6 is a flowchart illustrating a color temperature detection method, and FIG. 6 is a flowchart illustrating a color temperature detection method according to an exemplary embodiment of the present invention. 5 is an enlarged view of a portion A of FIG. 4.

Referring to FIG. 3, four reference light sources 'HOR', 'INC', 'CWF' and 'DL' are distributed in a color coordinate system having R / G ratio and B / G ratio as both axes. Here, 'HOR' means a standard light source having a color temperature (approximately 2300K) similar to the sunset seen in the horizon at evening, and the average coordinates of R / G of the standard light source in the color coordinate system of FIG. The distribution values for the ratio and the B / G ratio are displayed (indicated by the red dots in FIG. 3). 'INC' means standard light source with incandescent color temperature (approximately 2800K), 'CWF' means standard light source with color temperature (approximately 4300K) similar to fluorescent light (cool white Fluorescent), 'DL' refers to a standard light source with a color temperature (approximately 6500K) similar to daylight in daylight. These 'INC', 'CWF' and 'DL' are also displayed in the color coordinate system of FIG. , Green dots and turquoise dots). 3, it can be seen that the color temperature increases as the B / G ratio increases and drops as the R / G ratio increases. Hereinafter, the R / G ratio and B / G ratio distribution of the reference light source displayed in the color coordinate system are called light source ratio points.

As can be seen from the foregoing, the four reference light sources illustrated in FIG. 3 are standard light sources that can roughly include an imaging environment that users encounter in daily life, and these reference light sources are standard light sources that can be easily obtained in a laboratory. admit. Of course, the reference light source can be selected differently according to the needs of the manufacturer or the needs of the user.

Here, the distribution values for the average R / G ratio and B / G ratio of each reference light source should be obtained in advance by the manufacturer, and will be reflected in the form of a table or matrix when designing the color temperature detection algorithm according to the present invention. Can be. Therefore, more accurate color temperature detection will be possible if the optimal reference light sources are selected for the imaging environment placed on the user by the manufacturer. In addition, the manufacturer may select the number of reference light sources according to the performance of the MCU 140. The image signal processor 100 including the high-performance MCU 140 may further increase the accuracy of color temperature detection by selecting more reference light sources, and the low-performance MCU 140 may reduce the number of reference light sources to reduce the MCU. Stable color temperature detection may be achieved by reducing the computational burden of 140.

However, hereinafter, the description will be made with respect to a case where four standard light sources illustrated in FIG. 3 are selected as reference light sources.

The color temperature discrimination line illustrated in FIG. 3 is displayed on the color coordinate system as a straight line connecting the ratio point of the 'HOR' light source and the ratio point of the 'DL' light source. That is, the color temperature discrimination line according to the present invention is characterized in that each of the light source having the lowest color temperature (in this example, 'HOR' light source) and the light source having the highest color temperature (in this example, 'DL' light source) among the reference light sources. It can be selected as a straight line between the ratio points. Here, the reason why the light source having the lowest color temperature and the highest light source among the reference light sources is selected is to include all general imaging environments that may be placed on the user.

Of course, each of the straight lines connecting the black body radiation curve itself according to the light source or the ratio point for each reference light source such as the dotted lines in FIG. 3 may be used as the color temperature discrimination line. 140) may increase the burden. In particular, when a curve such as a black body radiation curve is selected as the color temperature discrimination line, an attempt is made to determine the color temperature in a two-dimensional space, which complicates an algorithm for color temperature detection. In addition, also in the calculation amount, the calculation amount is increased by four times or more than when determining the color temperature in the one-dimensional space on the basis of using the same algorithm. In addition, although several straight lines are used as the color temperature discrimination line, there are some advantages in the calculation amount, but there is a disadvantage in that the criteria and algorithms for the color temperature detection cannot be simplified.

Therefore, in the present invention, only one straight line connecting the ratio point between the light source having the lowest color temperature and the highest light source is selected as the color temperature determination line. This greatly reduces the computational load, so that even the low-performance MCU 140 can perform color temperature detection in real time without significant errors.

However, the color temperature discrimination line is merely a straight line arbitrarily set in order to detect the color temperature of the input image by using the one-dimensional distance proportional relationship (see the description of step S606 in FIG. 6) to be described later. Therefore, the color temperature discrimination line according to the present invention can be used as any straight line that can represent the distance proportional relationship used for color temperature detection. For example, the R / G axis or the B / G axis on the color coordinate system may be used as the color temperature discrimination line. This may be more readily understood through the following description.

Hereinafter, the color temperature detection method according to an exemplary embodiment of the present invention of FIG. 6 will be described in detail with reference to FIGS. 4 to 5.

Referring to FIG. 6, in step S601, the area discriminator 130 extracts white pixel data existing in the color temperature detection area from input image data, and in step S602, the data collector 135 extracts the input white pixel data from the input white pixel data. The cumulative value for each channel and the number of white pixel data are calculated. Steps S601 and S602 have been described above in detail with reference to the region determination unit 130 and the data collection unit 135 of FIG. 1, and thus a detailed description thereof will be omitted.

Steps S603 to S606 are both performed by the MCU 140 using a predefined color temperature detection algorithm. In addition, hereinafter, only the color temperature detection process for one reference data will be described. However, the same color temperature detection process will be sequentially performed for each reference data acquired for each frame. In addition, it is assumed that the reference data is located at the point illustrated in FIG. 4 on the color coordinate system.

In step S603, the MCU 140 acquires reference data by using the cumulative value for each channel and the number of white pixel data received from the data collector 135. The MCU 140 calculates an R / G ratio and a B / G ratio based on the cumulative value of each channel for the input one frame. Subsequently, the MCU 140 may obtain the average R / G ratio and B / G ratio of the input image frame by dividing the R / G ratio and the B / G ratio calculated by the number of white pixel data, respectively. At this time, the calculated average R / G ratio and B / G ratio become reference data. For example, R, G, and the cumulative value of the B channel, and each R _T, G _T and B _T average percentage point of the white pixel data based on data number is, assuming k gaera obtained by the MCU (140) (hereinafter , Referred to as the 'reference ratio point', will be located at the points R _T / G _T / k and B _T / G _T / k on the color coordinate system.

At this time, the reference ratio points of the acquired reference data are distributed on the color coordinate system by the MCU 140 (see FIG. 4).

In step S604, the MCU 140 generates a normal (hereinafter referred to as a 'reference normal') on the color coordinate system connecting the reference ratio point and the predefined color temperature discrimination line. In step S605, the MCU 140 calculates an intersection point (hereinafter, referred to as a 'reference intersection') between the reference normal and the R / G axis on the color coordinate system.

In FIG. 6, as illustrated in FIGS. 4 and 5, a case in which a normal line connecting a reference ratio point and a color temperature discrimination line is used to obtain a reference intersection is described. However, it is not necessarily required to be a normal line. That is, it is not necessary to be a straight line perpendicular to the color temperature discrimination line, and any straight line passing through the reference ratio point at an angle with the color temperature discrimination line may be used. In this case, light source intersections preset in the color temperature algorithm may also be calculated using a straight line having the same inclination (ie, parallel) as the previous straight line, rather than using a light source normal as described below.

In step S606, the MCU 140 compares the size of the light source intersection points of the reference intersection point and the reference light source to determine which two reference light sources are located between the reference ratio points of the reference data. In this case, the MCU 140 may detect the color temperature of the corresponding reference data by using a proportional relationship between the color temperature determination reference intersection point and the light source intersection points for the two reference light sources previously determined.

Here, the light source intersection refers to an intersection where a normal line connecting the light source ratio point of the reference light source and the color temperature discrimination line (hereinafter, referred to as a 'light source normal') meets the R / G axis or the B / G axis on the color coordinate system. The light source intersection is precomputed for each reference light source and preset in the color temperature detection algorithm. However, in the following description, it is assumed that the intersection of the light sources is an intersection on the R / G axis as illustrated in FIGS. 4 and 5.

Referring to FIG. 5 as an example, step S606 will be described in more detail. Through step S604, a reference normal line (identification number 20) connecting the reference ratio point (identification number 2) and the color temperature determination line (identification number 40) of the reference data is obtained. Is generated. Further, a reference intersection point (identification number 2 ') between the reference normal line (identification number 20) and the R / G axis on the color coordinate system is obtained through step S605.

Here, the light source intersection point (identification number 1 ') of the reference light source' HOR 'is a light source normal line (identification number 10) connecting the ratio point (identification number 1) and the color temperature discrimination line (identification number 40) to R on the color coordinate system. Preset to the intersection with the / G axis. In addition, the light source intersection point (identification number 3 ') of the reference light source' INC 'is a light source normal line (identification number 30) connecting the ratio point (identification number 3) and the color temperature discrimination line (identification number 40). Preset to the intersection with the / G axis. Light source intersections of the reference light sources 'CWF' and 'DL' are also obtained in this manner and set in advance.

The MCU 140 determines which two light source intersections among the preset light source intersections are located between the calculated reference intersections (identification number 2 '). This can be easily determined by comparing the magnitudes between the coordinate values on the R / G axis of the reference intersection point and the coordinate values of the light source intersection points. In the case of Figure 5, the reference intersection (identification number 2 ') is located between the light source intersection (identification number 1') of 'HOR' and the light source intersection (identification number 3 ') of' INC '. This comparison makes it possible to estimate the approximate range of color temperature of the reference data. That is, the color temperature of the reference data may be estimated to have a value larger than the color temperature of the 'HOR' light source (2300K) and smaller than the color temperature of the 'INC' light source (2800K).

When the range of the color temperature of the reference data is estimated through the above-described comparison process, the MCU 140 calculates a distance between the reference intersection and two light source intersections including the reference intersection. For example, the MCU 140 may determine a difference between the coordinate value of the reference intersection point (identification number 2 ') and the coordinate value of the light source intersection point (Hidification number 1') of 'HOR' on the R / G axis of the color coordinate system ( That is, the distance can be easily calculated as a difference between the coordinate values of a) and the reference intersection (identification number 2 ') and the coordinate values of the light source intersection (identification number 3') of 'INC' (that is, b). Of course, a method such as calculating the sum of the absolute values may be used to calculate the distance between the intersection having a negative value and the intersection having a positive value.

Here, it is preferable that the distance between the reference intersection point and each light source intersection point (see a and b of FIG. 5) is normalized and calculated by the MCU 140. For example, it can be calculated as the ratio of the distance between the reference intersection and the light source intersection such that the sum of a and b is any natural number (eg, "1"). Here, the sum of a and b, for example, "1" means that the distance between the reference light sources is normalized. In other words, it means that a certain number of light sources are selected as reference light sources, and the difference in color temperature between two reference light sources is normalized and set to "1".

In this case, the MCU 140 may estimate the color temperature of the reference data by using the distance proportional relationship between the normalized reference node and the light source intersection. For example, assuming that the normalized distance between the reference intersection point and the light source intersection point in FIG. 5 is calculated that a is 0.7 and b is 0.3, the color temperature of the reference data is about 2650K (2300 + (2800-2300) × 0.7). It can simply be calculated.

Here, of course, the color temperature of the reference data detected by the above-described method is an approximated value. As can be seen from Figure 5, between the reference intersection (identification number 2 ') of the reference data and the light source intersection (identification number 1') of the 'HOR' and the reference intersection (identification number 2 ') and' INC 'of the reference data The ratio of each distance (i.e., a and b) between the light source intersections (identification number 3 ') is determined between identification number 2 "and identification number 1" on the color temperature discrimination line (identification number 40) and identification number 2 ". Is equal to the ratio of the distance between the identification number 3 "(i.e., a 'and b'). That is, in the above-described color temperature detection method, the approximate ratio points of the reference ratio points (identification number 2) and the actual ratio points (identification number 1 and identification number 3) of the reference light source are projected on the color temperature discrimination line. The color temperature is detected using a proportional relationship between (identification number 1 "through identification number 3").

The reason for using the proportional relationship between the approximate ratio points on the color temperature discrimination line is to reduce the computational burden on the MCU 140 in the color temperature detection by using the linearity of the color temperature discrimination line (ie, the straight line). For sake. That is, the proportional relationship between the approximate ratio points on the color temperature discrimination line based on the linearity may be represented by the one-dimensional distance proportional relationship between the reference intersection point and the light source intersection point on the R / G axis of the color coordinate system.

As a result, the MCU 140 may perform calculation only on the R / G axis (ie, one-dimensional space) of the color coordinate system, not on the two-dimensional space, and detect the color temperature of the reference data according to the proportional relationship. Operation in the one-dimensional space has the effect of reducing the computational burden of the MCU 140 more than four times than in the operation in the two-dimensional space, through which the color temperature in real time without a large error even in the low-performance MCU 140 Can be detected.

In addition, the color temperature detection method according to the present invention enables simple and efficient color temperature detection without adding additional hardware for color temperature detection, thereby reducing the overall manufacturing cost of the image signal processor. .

As described above, the method and apparatus for detecting color temperature according to the present invention has the effect of reducing the burden on the MCU by minimizing the amount of calculation according to the color temperature detection.

In addition, the present invention has the effect of detecting the color temperature in real time without a large error even in a low-performance MCU.

In addition, the present invention has the effect of reducing the manufacturing cost of the image signal processor by simply implementing in software in the image signal processor without adding a separate hardware for color temperature detection.

Although the above has been described with reference to a preferred embodiment of the present invention, those skilled in the art to which the present invention pertains without departing from the spirit and scope of the present invention as set forth in the claims below It will be appreciated that modifications and variations can be made.

Claims (13)

An area determination unit which receives pixel data interpolated from an electric image signal input from an image sensor and selectively outputs only pixel data included in a preset color temperature detection area; Data collection for outputting a channel-specific cumulative value obtained by accumulating and summing data values of each channel of red (R), green (B), and blue (B) of the pixel data input from the area determination unit in each image frame unit. part; And Each light source color ratio value is stored according to a color temperature of two or more preselected reference light sources, and an input color ratio value is calculated from the cumulative values for each channel of each image frame unit input from the data collection unit. The distance is proportional to the intersections where the straight lines passing through the input color ratio value and the respective light source color ratio values meet a predetermined color temperature discrimination line to form a constant angle with the reference line formed using the light source color ratio values of the two reference light sources. Including a micro control unit (MCU) for detecting a color temperature corresponding to the input image using the relationship, The light source color ratio value is an average ratio (R / G ratio) of red data values to green data values of the input image of the reference light source and an average ratio of blue data values to green data values (B / G image signal processor capable of detecting a color temperature, characterized in that the ratio; The method of claim 1, The area determining unit includes an achromatic pixel extraction filter, and the color temperature detection area corresponds to the achromatic pixel data. The method of claim 1, The reference line is a straight line connecting the light source color ratio value of the reference light source having the highest color temperature and the light source color ratio value of the reference light source having the lowest color temperature. Processor. The method of claim 1, The data collecting unit calculates the number of pixel data input from the area determining unit in each image frame unit, and the MCU divides the cumulative value for red data among the cumulative values for each channel by the cumulative value for green data. Calculate the second ratio by dividing the 1 ratio and the cumulative value for the blue data by the cumulative value for the green data, And the input color ratio value is an average value obtained by dividing the first ratio and the second ratio by the number of pixel data input from the area discriminator. The method of claim 1, When the color temperature discrimination line is the reference line, two intersection points corresponding to the input color ratio value and two intersection points corresponding to the input color ratio value among intersection points corresponding to the input color ratio value and each light source color ratio value are provided. An image signal processor capable of detecting a color temperature using a distance proportional relationship between intersections. The method of claim 5, And said constant angle is 90 [deg.]. The method of claim 1, And the distance proportional relationship is normalized and calculated by the MCU. The method of claim 1, When the color temperature determination line is a vertical line or a horizontal line in which the ratio of the blue data value to the green data value or the ratio of the red data value to the green data value is 0, the intersection point corresponding to the input color ratio value and the Image signal processor capable of color temperature detection, characterized in that it is calculated by using the distance proportional relationship between the intersection corresponding to the input color ratio value and the two intersection points existing at the shortest distance among the intersection points corresponding to each light source color ratio value . (a) storing respective light source color ratio values according to color temperatures of two or more preselected reference light sources; (b) receiving the interpolated pixel data of the electrical image signal input from the image sensor and selectively outputting only pixel data included in a preset color temperature detection area; (c) accumulating and summing data values of respective channels of red (R), green (B), and blue (B) with respect to the selectively output pixel data to generate a cumulative value for each channel in each image frame unit; ; (d) calculating an input color ratio value of each image frame unit from the cumulative value of each channel; (e) between intersection points where a straight line passing through the input color ratio value and the light source color ratio value meets a predetermined color temperature discrimination line at a predetermined angle with a reference line formed by using the light source color ratio values of two preset light sources; Detecting a color temperature corresponding to the input image using a distance proportional relationship of  The light source color ratio value is an average ratio (R / G ratio) of red data values to green data values of the input image of the reference light source and an average ratio of blue data values to green data values (B / G color temperature detection method in an image signal processor characterized by the above-mentioned. The method of claim 9, The reference line is a color temperature in the image signal processor, characterized in that the straight line connecting the light source color ratio value of the reference light source having the highest color temperature and the light source color ratio value of the reference light source having the lowest color temperature. Detection method. The method of claim 9, Prior to step (d) above (f) calculating the number of the selectively output pixel data for each image frame unit; And (g) calculating a first ratio of the cumulative value for the red data divided by the cumulative value for the green data and the second ratio of the cumulative value for the blue data divided by the cumulative value for the green data among the cumulative values for each channel; Include more, And the input color ratio value is an average value obtained by dividing the first ratio and the second ratio by the number of selectively output pixel data. The method of claim 9, When the color temperature discrimination line is the reference line, two intersection points corresponding to the input color ratio value and two intersection points corresponding to the input color ratio value among intersection points corresponding to the input color ratio value and each light source color ratio value are provided. A color temperature detection method in an image signal processor using a distance proportional relationship between intersections. The method of claim 9, When the color temperature determination line is a vertical line or a horizontal line in which the ratio of the blue data value to the green data value or the ratio of the red data value to the green data value is 0, the intersection point corresponding to the input color ratio value and the Color temperature in the image signal processor characterized in that the calculation using the distance proportional relationship between the intersection corresponding to the input color ratio value and the two intersection points existing in the shortest distance among the intersection points corresponding to each light source color ratio value Detection method.

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