KR100695224B1 - System and method for determining temperature of light source by measuring color temperature - Google Patents

Abstract

A system and a method for determining a temperature of an optical source using a color temperature are provided to efficiently detect a temperature of a furnace by efficiently measuring the temperature under a high temperature environment. A method for determining a temperature of an optical source using a color temperature including the steps of calculating a brightness level classified by images, and separating the images into an optical region and a background region by setting a pixel group of which the brightness level is larger than a threshold value to the optical region, and setting a pixel group of which the brightness level is smaller than the threshold value(S100), dividing the images into a predetermined number of sub blocks, and calculating red, green, and blue values of a reference white color of a part which is estimated as the optical region for each sub block, converting the red, green, and blue values into a chromaticity coordinate value of CIE chromaticity coordinates, and calculating the color temperature of the optical source for each sub block by using the chromaticity coordinate value.

Description

System and Method for Determining Temperature of Light Source by Measuring Color Temperature

1 is a flowchart illustrating a process of extracting a light source region in a method of determining a temperature of a light source using color temperature measurement according to a preferred embodiment of the present invention;

2 is a histogram showing the ratio of pixels for each brightness level derived from a result of calculating the brightness levels for each pixel;

3 is a flowchart illustrating a process of measuring a color temperature of a light source region in a method of determining a temperature of a light source using color temperature measurement according to a preferred embodiment of the present invention;

4 is a diagram illustrating an (x, y) chromaticity coordinate system;

5 is a view showing the configuration of a temperature determination system of a light source using color temperature measurement according to a preferred embodiment of the present invention.

<Description of Symbols for Main Parts of Drawings>

500: color image recording apparatus 510: image receiving unit

520: light source region extraction unit 530: block division unit

540: temperature measuring unit 542: reference white estimating unit

544: coordinate conversion unit 546: color temperature measurement unit

The present invention relates to a temperature determination system and method of a light source using color temperature measurement. More specifically, the image received from the color imaging apparatus installed where the light source emitting visible light is located is divided into a light source region and a background region, and the three primary colors of the reference white (red light, green light, blue light) of the portion estimated as the light source region. A system and method for determining a temperature of a light source using color temperature measurement after calculating a value and converting the calculated three primary color values of the reference white to chromaticity coordinates to determine the temperature or temperature distribution of the light source by measuring the color temperature or color temperature distribution of the light source. It is about.

An object that absorbs all incident electromagnetic waves is called a black body. The relationship between the color of the light emitted by the ideal blackbody and the temperature of the blackbody follows Planck's law of radiation, so knowing the color of the light that the blackbody emits reveals the temperature of the blackbody.

Color temperature is a numerical representation of the light of a light source using the properties of such a black body. When an object is shining with visible light, if the color looks like the color of a black body radiating at a certain temperature, The temperature of an object is said to be the same and the temperature is called the color temperature of the object.

Therefore, the color temperature can be used to measure the temperature in a furnace such as a power plant in which carbon or graphite having a black body-like property is used as a main light source.

Conventionally, the method of measuring the temperature by using the volume change according to the temperature of the chemically inert gas, the method of measuring the thermal couple using the generation of organic electromotive force according to the temperature difference of the contact point, A method using an optical thermometer to measure the temperature by comparing the brightness, a method using a change in the propagation speed of the sound according to the change in air density with temperature.

However, these temperature measurement methods have the following problems.

First, the method using the volume change of the gas has a large range of measurement error because the measurable range is narrow and the volume change according to the temperature change is not linear.

The thermocouple measurement method requires a sensor to be contacted with the object to be measured, which limits the use environment and is vulnerable to contamination.

The method using the optical pyrometer may cause an error according to the type of light source.

Finally, the method using the change of air density has a disadvantage that it is difficult to measure precisely in the unstable air flow part such as in the furnace and requires expensive equipment.

Due to these vulnerabilities, the existing temperature measurement methods have a problem in that they cannot perform precise temperature measurement when applied to a high temperature and harsh environment such as a furnace.

In order to solve this problem, the present invention divides an image received from a color imaging apparatus installed at a light source emitting visible light into a light source region and a background region, and uses three primary colors of reference white (red light) of a portion estimated as the light source region. , Green light, blue light) and then convert the calculated three primary color values of the reference white into chromaticity coordinates to measure the color temperature or color temperature distribution of the light source to determine the temperature or temperature distribution of the light source. It is an object to provide a temperature determination system and method.

In order to achieve the above object, the present invention provides a method for determining the temperature of the light source by measuring the color temperature of the image received from the color imaging apparatus mounted in the position where the light source emitting visible light is located (a) The brightness level is calculated for each pixel of the image, and the image is divided into the light source region and the background region using a set of pixels having a brightness level greater than a predetermined threshold as a light source region and a set of small pixels as a background region. step; (b) The image is divided into a predetermined number of subblocks, and reference white red light (hereinafter referred to as "R") and green light (hereinafter, "G") of a portion estimated as the light source region for each subblock. Calculating blue light (hereinafter referred to as "B") value; (c) converting R, G, and B values of the reference white into chromaticity coordinate values of a Commission Internationale de L'Eclairage (CIE) chromaticity coordinate system; And (d) calculating a color temperature of the light source for each of the sub-blocks using the chromaticity coordinate values converted in the step (c). .

In another aspect, the present invention, in the system for determining the temperature of the light source by measuring the color temperature of the image received from a color imaging apparatus mounted in the position where the light source emitting visible light is located, the color image capture An image receiving unit which receives the image from a device; When the image is received from the image receiving unit, the brightness level is calculated for each pixel of the image, and the brightness level is compared with a predetermined threshold value to extract a set of pixels whose brightness level is greater than the threshold value as a light source region. A light source region extraction unit; And when the image divided into the light source region and the background region is received from the light source region extracting unit, red light of a reference white of a portion estimated as the light source region (hereinafter referred to as "R"), and green light (hereinafter referred to as "G"). Color temperature of the light source by calculating a value of blue light (hereinafter referred to as "B") and converting the R, G, and B values of the reference white into chromaticity coordinates of a Commission Internationale de L'Eclairage (CIE) chromaticity coordinate system. It provides a temperature determination system of the light source using a color temperature measurement, characterized in that it comprises a temperature measuring unit for measuring.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings. First of all, in adding reference numerals to the components of each drawing, it should be noted that the same reference numerals are used as much as possible even if displayed on different drawings. In addition, in describing the present invention, when it is determined that the detailed description of the related well-known configuration or function is obvious to those skilled in the art or may obscure the gist of the present invention, the detailed description thereof will be omitted.

In addition, the following description will be limited to measuring the temperature in a furnace of a power plant that burns fuel such as carbon or graphite, but the present invention is not limited thereto, but the present invention is not limited thereto. The same applies to the case where the temperature of the light source is determined where the light source that emits light is located.

According to a preferred embodiment of the present invention, a method for determining a temperature of a light source using color temperature measurement may include extracting a light source region of an image received from a color imaging apparatus mounted in a furnace of a power plant, and extracting the light source region of the extracted light source region. It is divided into the process of measuring the color temperature.

1 is a flowchart illustrating a process of extracting a light source region in a method of determining a temperature of a light source using color temperature measurement according to a preferred embodiment of the present invention.

The method of extracting a light source region calculates a brightness level for each pixel, and sets a set of pixels having a brightness level greater than a predetermined threshold as a light source region, and a set of pixels having a brightness level equal to or less than a background region (non-light source region). ), The light source region is extracted.

In this case, setting of a threshold becomes an important problem. In a preferred embodiment of the present invention, an Otsu binarization method is used. Here, the binarization method of OS is applied in the present invention by using it to find an optimal threshold for separating two groups in separating a specific group into two groups.

First, when an image in a furnace is received from a color imaging apparatus, red light (hereinafter referred to as "R"), green light (hereinafter referred to as "G"), and blue light (hereinafter referred to as "B") that each pixel has for each pixel of the image. The brightness level is calculated using Equation 1 from the value S (S100).

(I는 명도 레벨)

(I is the brightness level)

When the brightness level is calculated for all the pixels, the ratio of the pixels having the corresponding brightness level for each brightness level is calculated (S102).

Then, an arbitrary t value is set between the upper limit value and the lower limit value of the brightness level, and the received image is divided into a set of pixels (region 1) having a brightness level less than or equal to the t value (region 1) and a pixel having a brightness level greater than the t value. It separates into a set (area 2) (S104).

The probability q ₁ (t) occupied by region 1 and the probability q ₂ (t) occupied by region 2 are calculated using the ratio of pixels for each brightness level calculated in operation S102 (S106). A variance of ₁ (σ ₁ ² (t)) and a dispersion of region 2 (σ ₂ ² (t)) are obtained (S108). This will be described later with reference to FIG. 2.

Subsequently, a weighted sum (σ _w ² (t)) of the variance of the region 1 and the variance of the region 2 is calculated using Equation 2 (S110).

Steps S104 to S110 are repeated for all t between the upper limit value and the lower limit value of the brightness level to obtain a value t that minimizes the calculated weighted sum and sets this value t as a threshold value (S112). The set of pixels having the brightness level is extracted as the light source region (S114). Here, t can be set to various values between the upper limit value and the lower limit value, and preferably set to an integer between the upper limit value and the lower limit value. That is, steps S104 to S110 are repeated for all integers t between the upper limit value and the lower limit value.

2 is a histogram showing the ratio of pixels for each brightness level derived from a result of calculating the brightness levels for each pixel.

As shown in FIG. 2, the horizontal axis (X axis) of the histogram represents a brightness level, and the vertical axis (Y axis) represents a ratio of pixels having each brightness level.

Using this, the probability q ₁ (t) occupied by region 1 and the probability q ₂ (t) occupied by region 2 with respect to a constant value t are expressed by Equation 3 below.

Here, P (i) means the ratio of the pixels whose brightness level is i, and L means the upper limit of the brightness level.

And dispersion (σ ₁ ² (t)) and the variance (σ _{² 2} (t)) of the second region of the region 1 is expressed as Equation (4).

Here, μ ₁ (t) means the average of the region 1, μ ₂ (t) means the average of the region 2, and can be obtained by using Equation 5, respectively.

Using the equations (3) to (5), the probability q ₁ (t) occupies the area 1, the probability q ₂ (t) occupies the area 2, and the variance of the region 1 (σ ₁ ² ) in steps S106 and S108. (t)) and the dispersion (σ ₂ ² (t)) of the region 2 can be obtained.

3 is a flowchart illustrating a process of measuring a color temperature of a light source region in a method of determining a temperature of a light source using color temperature measurement according to a preferred embodiment of the present invention.

First, an image received from the color image capturing apparatus is divided into a predetermined number of subblocks as shown in FIG. 1 (S300).

                    (Figure 1)

Here, when the predetermined number is set to 1, the average color temperature of the light source is measured, and when set to 2 or more, the distribution of the color temperature of the light source can be known. The predetermined number may be changed by the operator according to the resolution and color quality of the received image.

When the image is divided into a predetermined number of subblocks, upper N pixels having a high brightness level among the pixels estimated as the light source regions are extracted for each subblock (S302). At this time, in extracting the upper N pixels, when the brightness level of the pixel is 255, it is regarded as being clipped and excluded from extraction.

When all of the upper N pixels are extracted, the average of the R, G, and B values of the upper N pixels is obtained, and the respective averages are determined as the R, G, and B values of the reference white (S304).

,

,

를 구하게 된다.That is, the R, G, and B values of the upper N pixels for each subblock are divided into separate sets as shown in Equation 6, and the average for each of the R, G, and B values as shown in Equation 7.

,

,

Will be obtained.

Here, (i, j) _set means a subblock corresponding to the i th row and the j th column.

The average for each of the R, G, and B values is an estimated value of the R, G, and B values of the reference white.

Subsequently, the estimated R, G, and B values of the reference white are converted into chromaticity coordinate values of the Commission Internationale de L'Eclairage (CIE) chromaticity coordinate system. In a preferred embodiment of the present invention, the National Television Standards Committee (NTSC) It uses a reference coordinate transformation matrix and a two-dimensional (x, y) chromaticity coordinate system.

That is, the RGB value of the reference white is converted into tristimulus values X, Y, and Z values using the coordinate transformation matrix of the NTSC standard as shown in Equation 8 (S306).

Here, M denotes a coordinate transformation matrix based on NTSC, and is generally given as in Equation 9, but this can be corrected.

When the tristimulus values X, Y, and Z are calculated in step S306, the tristimulus values X, Y, and Z are converted into (x, y) chromaticity coordinates x _s and y _s using Equation 10 (S308).

In addition, it is determined whether (x _s , y _s ) is located on a specific isotemperature line (S310), and when it is located on a specific isothermal temperature line, the color temperature indicated by the specific isothermal temperature line is determined as the color temperature of the light source (S312). ).

However, when (x _s , y _s ) is not located on a specific isothermal temperature line, two isothermal temperature lines that exist at the closest distance from (x _s , y _s ) are extracted, and the light source is expressed using Equation 11 The correlation color temperature is calculated and the correlation color temperature is determined as the color temperature of the light source. Here, the correlated color temperature means the absolute temperature of the black body having the chromaticity closest to that of the light source. Therefore, when the light source does not have the same chromaticity as that of the black body, the color temperature of the light source may be estimated through the correlated color temperature.

Where T _c is the correlated color temperature, T _i is the color temperature of the isothermal temperature line with the lower color temperature among the extracted two isothermal temperature lines, and d _i is the vertical from the (x, y) chromaticity coordinate value to the isothermal temperature line with the lower color temperature. Distance, T _{i +1} is the color temperature of the orange color temperature line of the extracted two isothermal temperature lines, and d _{i +1} is the vertical distance from the (x, y) chromaticity coordinate value to the high color temperature it means.

Hereinafter, a method (steps S310 to S316) of calculating a color temperature using the (x, y) chromaticity coordinate values (x _s and y _s ) of the light source calculated in step S308 will be described in more detail with reference to FIG. 4. .

4 is a diagram illustrating a (x, y) chromaticity coordinate system.

As shown in FIG. 4, the chromaticity coordinate system shows a black body locus (Planckian Locus) indicating the trace of the black body according to the temperature change of the black body and an isothermal temperature line perpendicular to the black body locus. In the chromaticity coordinate system, 31 isotherm temperature lines are generally drawn, and all chromaticity points existing on the same isotherm temperature line have the same color temperature.

If the coordinate of the intersection point where the i th isotherm meets the blackbody trajectory is (x _i , y _i ) and the slope of the i th isotherm is m _i , the equations of the straight line (straight line 1) and i of the i th isotherm The equation of a straight line (straight line 2) perpendicular to the first isotherm temperature line and passes through (x _s , y _s ) is given by Equation 12.

직선 1: 직선 2:

Straight line 1: straight line 2:

The coordinates (x _e , y _e ) of the intersections of the straight line 1 and the straight line 2 are given by Equation 13.

Therefore, the vertical distance d _i from (x _s , y _s ) to the i-th isothermal temperature line can be obtained using Equation 14.

That is, the coordinate of the intersection is the i-th orange color temperature line of intersection with the black body locus (x _i, y _i) and the i th color matching temperature of the line slope know the m _i, using equation 13 and equation 14 (x _s, y _s ) is the vertical distance from the ith isothermal temperature line.

Therefore, when the chromaticity coordinate values (x _s , y _s ) of the light source are calculated, the distances from (x _s , y _s ) to all isothermal temperature lines are calculated using Equations 13 and 14, and the orange color having a distance of 0 is obtained. If a temperature line exists, (x _s , y _s ) exists on the orange temperature line, and the color temperature of the orange temperature line is determined as the color temperature of the light source.

However, when there is no orange temperature line having a distance of 0, two color temperature lines having the smallest value are extracted from the calculated distances, and the correlation color temperature is measured using Equation 11.

Hereinafter, a temperature determination system of a light source using color temperature measurement implemented using the above-described method will be described.

5 is a view showing the configuration of a temperature determination system of a light source using color temperature measurement according to a preferred embodiment of the present invention.

In the system for determining the temperature of a light source using color temperature measurement according to an exemplary embodiment of the present invention, a color image photographing apparatus 500, an image receiving unit 510, a light source region extracting unit 520, and a block dividing unit 530 installed in a furnace are provided. And a temperature measuring unit 540.

The color image capturing apparatus 500 captures an image in a furnace in which a light source exists and transmits the image to the image receiving unit. The image receiving unit 510 transmits an image received from the color image capturing apparatus 500 to a light source region extracting unit ( 520 and the block divider 530.

The light source region extractor 520 calculates a brightness level for each pixel of the image received from the image receiver 510, compares the brightness level with a predetermined threshold value, and sets a set of pixels having a brightness level greater than the threshold value. Performs the extraction function.

As described above, the threshold value is set using the binarization method of OS. For this purpose, the light source region extracting unit calculates a brightness level for each pixel of the image to calculate a ratio of pixels having the corresponding brightness level for each brightness level. Function, and set an arbitrary t value between an upper limit value and a lower limit value of the brightness level to separate the received image into a set of pixels (area 1) and a larger pixel (area 2) having a brightness level equal to or less than t. Then, the probability q ₁ (t) occupies the area 1 and the probability q ₂ (t) occupies the area 2 and the variance of the area 1 (σ ₁ ² ( t)) and the variance σ ₂ ² (t) of the region 2, and a weighted sum of the variance of the region 1 and the variance of the region 2 is calculated using Equation 2.

In addition, among the weighted sums derived when the second function is performed for all t between the upper limit value and the lower limit value, a value t is set as a threshold value to set a set of pixels having a brightness level larger than the threshold value. The third function of extracting the light source region is performed.

When the temperature measuring unit 540 receives an image separated from the light source region and the background region instead of the light source region from the light source region extraction unit 520, the temperature measuring unit 540 calculates R, G, and B values of the reference white of the portion estimated as the light source region. The reference white estimator 542, the coordinate converter 544, and the color temperature measurer 546 are means for converting the R, G, and B values of the reference white into chromaticity coordinates of the CIE chromaticity coordinate system to measure the light source color temperature. It is configured to include).

The reference white estimator 542 extracts the upper N pixels having a high brightness level among the pixels estimated as the light source region, obtains an average for each of the R, G, and B values of the upper N pixels, and calculates an average of each of the average values of R as the reference white. Performs the function of setting the values of G, B.

The coordinate conversion unit 544 converts the RGB values of the reference white into tristimulus values XYZ values using an NTSC coordinate transformation matrix, and calculates (x, y) chromaticity coordinate values of the light source using Equation 10. do.

The color temperature measuring unit 546 determines whether the (x, y) chromaticity coordinate value calculated by the coordinate converting unit 544 is located on a specific isothermal temperature line, and when the color temperature measurement line is positioned on a specific isothermal temperature line, the specific isothermal temperature line is determined. If the color temperature indicated is determined as the color temperature of the light source, and if it is not located on a specific isothermal temperature line, two isothermal temperature lines that are the closest to the (x, y) chromaticity coordinate value are extracted, and the correlation of the light source is expressed using Equation 11 Measures the color temperature and determines the correlated color temperature as the color temperature of the light source.

As described with reference to FIG. 4, the color temperature measuring unit 546 only needs to store intersection points of the blackbody trajectory and the isotherm temperature line and inclination values of the isothermal temperature line, respectively. Find the distance to, and if there is an isothermal temperature line with zero distance, determine that the (x, y) chromaticity coordinates are located on the isothermal temperature line, and if there is no isothermal temperature line with zero distance, Two orange temperature lines with a distance are extracted.

The temperature determination system of the light source using the color temperature measurement according to the preferred embodiment of the present invention may further include a block dividing unit 530. The block dividing unit 530 receives an input from an operator or has a predetermined number. Performs a function of dividing the image received from the image receiving unit 510. When the predetermined number is set to 1 in the block dividing unit 530, the temperature determiner 540 measures the average color temperature of the light source. When the number is set to 2 or more, the temperature distribution of the light source is measured by measuring the color temperature of the light source for each sub block. Will yield.

The above description is merely illustrative of the technical idea of the present invention, and those skilled in the art to which the present invention pertains may make various modifications and changes without departing from the essential characteristics of the present invention. Therefore, the embodiments disclosed in the present invention are not intended to limit the technical idea of the present invention but to describe the present invention, and the scope of the technical idea of the present invention is not limited by these embodiments. The protection scope of the present invention should be interpreted by the following claims, and all technical ideas within the equivalent scope should be interpreted as being included in the scope of the present invention.

As described above, according to the present invention, the temperature can be efficiently measured even in a high temperature environment where temperature is difficult to be measured, such as a furnace such as a power plant or a steel mill, so that the temperature of the furnace can be efficiently monitored.

In addition, it is possible to measure temperature reliably regardless of the change of measurement environment, compared to the existing temperature measurement method, in which the precision changes sensitively and the use range is limited according to the change of measurement environment, and the equipment required for temperature measurement at a lower cost. There is an advantage that can be installed.

Claims (12)

In the method of determining the temperature of the light source by measuring the color temperature of the image received from the color imaging apparatus mounted in the position where the light source emitting visible light is located, (a) The brightness level is calculated for each pixel of the image, and the image is displayed in the light source region and the background region with a set of pixels having a brightness level greater than a predetermined threshold as a light source region and a set of small pixels as a background region. Separating into; (b) The image is divided into a predetermined number of subblocks, and reference white red light (hereinafter referred to as "R") and green light (hereinafter, "G") of a portion estimated as the light source region for each subblock. Calculating blue light (hereinafter referred to as "B") value; (c) converting R, G, and B values of the reference white into chromaticity coordinate values of a Commission Internationale de L'Eclairage (CIE) chromaticity coordinate system; And (d) calculating a color temperature of the light source for each sub-block by using the chromaticity coordinate value converted in step (c) Including, but the step (a), (a1) calculating the brightness level for each pixel of the image using the following equation and calculating a ratio of pixels for each brightness level;

Where I is the brightness level (a2) An arbitrary value t between an upper limit value and a lower limit value of the brightness level is set, and the set of pixels having the brightness level smaller than or equal to the t (region 1) of the image having the brightness level greater than the t value is set. After separation into a set (area 2), the probability q ₁ (t) occupies the area 1 and the probability q ₂ (t) occupies the area 2 in the image using a ratio of pixels for each brightness level. And the dispersion (σ ₁ ² (t)) of the region 1 and the dispersion (σ ₂ ² (t)) of the region 2, and weighted sum of the dispersion of the region 1 and the dispersion of the region 2 using the following equation. Calculating Weighted Sum (σ _w ² (t)); And

(a3) setting a value of t that causes the weighted sum to be the minimum among the t values between the upper limit value and the lower limit value as the threshold value, and setting the set of pixels having the brightness level greater than the threshold value as the light source region. step Temperature determination method of the light source using a color temperature measurement, comprising a. delete delete The method of claim 1, In step (b), (b1) dividing the image into a predetermined number of subblocks; (b2) extracting the upper N pixels having the high brightness level among the pixels estimated as the light source regions for each of the subblocks; And (b3) obtaining the average of the extracted R, G, and B values of the upper N pixels, and setting the average of the R, G, and B values as the R, G, and B values of the reference white. Temperature determination method of the light source using a color temperature measurement, comprising a. The method of claim 4, wherein In the step (b2), the pixel having the brightness level of 255 is regarded as being clipped and excluded from extraction. The method of claim 1, In the step (b), the predetermined number is 1 or more and can be changed according to the resolution and color quality of the image received from the color image capturing apparatus. The method of claim 1, In step (c), (c1) converting R, G, and B values of the reference white into tristimulus values X, Y, and Z values using a coordinate transformation matrix of a National Television Standards Committee (NTSC) standard; And (c2) converting the converted tristimulus values X, Y, Z values into (x, y) chromaticity coordinate values using the following equation:

Temperature determination method of the light source using a color temperature measurement, comprising a. The method of claim 7, wherein In step (d), (d1) setting the color temperature indicated by the specific isotherm temperature line as the color temperature of the light source when the (x, y) chromaticity coordinate value is located on a specific isotemperature line; And (d2) If the (x, y) chromaticity coordinate value is not located in the specific isothermal temperature line, two isotemperature lines closest to the (x, y) chromaticity coordinate value are extracted, and the following equation is obtained. Calculating a correlation color temperature of the light source by using the correlation color temperature as a color temperature of the light source

(T _c : correlated color temperature, T _i : color temperature of the orange color temperature line having the lower color temperature among two extracted color temperature lines, d _i : (x, y) from the chromaticity coordinate value to the orange color temperature line having a lower color temperature Vertical distance, T _{i +1} : Color temperature of the orange color temperature line of the extracted two orange temperature lines, d _{i +1} : Vertical distance from (x, y) chromaticity coordinate value to orange color temperature line with high color temperature ) Temperature determination method of the light source using the color temperature measurement, characterized in that. In the system for determining the temperature of the light source by measuring the color temperature of the image received from the color imaging apparatus mounted in the place where the light source emitting visible light is located, An image receiving unit which receives the image from the color image photographing apparatus; When the image is received from the image receiver, the brightness level is calculated for each pixel of the image, and the light source is configured to extract a set of pixels having a brightness level greater than the threshold value to a light source area by comparing the brightness level with a predetermined threshold value. An area extractor; And When the image separated into the light source region and the background region is received from the light source region extracting unit, red light of a reference white (hereinafter referred to as "R") and green light (hereinafter referred to as "G") of a portion estimated as the light source region And blue light (hereinafter referred to as "B") values, and convert the R, G, and B values of the reference white into chromaticity coordinates of a Commission Internationale de L'Eclairage (CIE) chromaticity coordinate system. Temperature measuring unit to measure Including but not limited to: The light source region extraction unit, A first function of calculating a brightness level for each pixel of the image to calculate a ratio of pixels for each brightness level, an arbitrary value t between an upper limit value and a lower limit value of the brightness level, and setting the image to be less than or equal to the t After separating the set of pixels having the brightness level (region 1) and the set of pixels having the large brightness level (region 2), the probability that the region 1 occupies in the image using the ratio of the pixels for each brightness level (q ₁ (t)) and the probability occupied by the region 2 (q ₂ (t)), the variance of the region 1 (σ ₁ ² (t)) and the variance of the region 2 (σ ₂ ² (t)) Finding, Equation

A second function for calculating a weighted sum (σ _w ² (t)) of the variance of the area 1 and the variance of the area 2 by using and for all the t values between the upper limit and the lower limit And a third function of performing a second function to set the t value at which the weighted sum is minimum to the threshold value and extracting a set of pixels having a brightness level greater than the threshold value to the light source region. Temperature determination system of the light source using the color temperature measurement. The method of claim 9, The system further includes a block divider for dividing the image into the predetermined number of sub-blocks when a predetermined number is input from an operator, and the temperature measuring unit is configured for each of the sub-blocks divided by the block divider. Temperature determination system of the light source using the color temperature measurement, characterized in that for measuring the color temperature of the light source. delete The method of claim 9, The temperature measuring unit, The light source region extracting unit extracts the upper N pixels having the highest brightness level among the pixels estimated as the light source region, obtains an average for each of the R, G, and B values of the upper N pixels, and calculates an average for each of the R, G, and B values. A reference white estimator configured to determine R, G, and B values of the reference white; The R, G, and B values of the reference white calculated by the reference white estimator are converted into tristimulus values X, Y, and Z using a coordinate transformation matrix of NTSC, and

And

A coordinate conversion unit for converting the tristimulus values X, Y, and Z values into (x, y) chromaticity coordinate values by using; And When the (x, y) chromaticity coordinate value is located on a specific isothermal temperature line, the color temperature indicated by the specific isothermal temperature line is determined as the color temperature of the light source, and when it is not located on the specific isothermal temperature line, the (x, y) chromaticity is A color temperature measuring unit which extracts two isothermal temperature lines that exist at a closest distance from a coordinate value, measures a correlated color temperature of the light source using the following equation, and sets the correlated color temperature as the color temperature of the light source.

(T _c : correlated color temperature, T _i : color temperature of the orange color temperature line having the lower color temperature among two extracted color temperature lines, d _i : (x, y) from the chromaticity coordinate value to the orange color temperature line having a lower color temperature Vertical distance, T _{i +1} : Color temperature of the orange color temperature line of the extracted two orange temperature lines, d _{i +1} : Vertical distance from (x, y) chromaticity coordinate value to orange color temperature line with high color temperature ) Temperature determination system of the light source using the color temperature measurement, characterized in that it comprises a.

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