1. A real-time high-temperature field measuring method based on a logarithmic polynomial is characterized by comprising the following steps:

(1) shooting an original image: shooting a high-temperature object to be detected by using a common camera to obtain an original image;

(2) acquiring an RGB space image: deriving a color filter matrix from the original image obtained by shooting in the step (1), and performing Bayer interpolation to obtain an RGB space image of the high-temperature object to be detected;

(3) calculating the logarithm of the intensity of the primary color r: calculating the proportion of any two primary colors in the RGB space image and taking the logarithm to obtain the logarithm of the intensity ratio of any two primary colors, which is called as the logarithm r of the primary color intensity;

(4) calculating the temperature of the high-temperature object to be measured: according to the logarithm r of the intensity of the primary colors and the temperature of the high-temperature object to be measuredAnd calculating the temperature of the high-temperature object to be measured according to the functional relation.

2. The log-polynomial-based real-time high-temperature field measurement method according to claim 1, wherein in the step (3), the logarithm of the intensity of the primary color r is calculated as follows:

r＝ln(R/G)

or, R ═ ln (R/B)

Or, r ═ ln (B/G)

Wherein R, G, B represent the intensity data of the three primary colors, respectively.

3. The log-polynomial-based real-time high-temperature field measurement method according to claim 1 or 2, wherein in the step (3), the logarithm r of the intensity of the primary color is calculated by using the same two primary colors for different colors of the high-temperature object.

4. The log-polynomial-based real-time high-temperature field measurement method according to claim 1, wherein in the step (4), the logarithm r of the intensity of the primary colors and the temperature of the high-temperature object to be measuredThe function of (c) is as follows:

wherein n is the maximum degree of the polynomial, i represents the degree of the polynomial, k_iRepresenting the coefficients of an i-th order polynomial.

5. The log polynomial based real-time high temperature field measurement method of claim 4,characterized in that k is_iThe method for acquiring the coefficient comprises the following steps: shooting temperature fields with different temperatures by using a common camera to obtain a series of images with known temperatures, thereby determining the logarithm r of the intensity of the primary colors and the temperature T corresponding to r, and setting an n value according to the nonlinear degree between 1/T and r; after setting n, all k are determined according to the least squares principle_i。

6. The log polynomial based real-time high temperature field measurement method of claim 5, wherein the greater the degree of non-linearity between 1/T and r, the greater the value of n.

7. The method of claim 5, wherein n is 2.

8. The log polynomial based real-time hyperthermia temperature field measurement method of claim 4 or 5, wherein k is obtained_iThe specific formula of the coefficients is:

wherein K ═ K₀ k₁ ... k_i ... k_N]K denotes that i is 0,1, …, n_iA constructed vector;

representing a vector formed by the inverses of the temperatures of N samples, T_jRepresents the temperature of the jth sample;

a matrix of polynomials representing the logarithm r of the intensity of the primary colors in N samples,to representThe pseudo-inverse of the matrix.

9. The log-polynomial based real-time high-temperature field measurement method of claim 8, wherein,a vector of polynomials representing the logarithm of the intensity of the primary color r of the j-th sample,an i-th polynomial representing the r of the jth sample.

Background

In the industrial field, there are a very large number of industries that involve high temperature processes, such as thermal power generation, coal gasification, metallurgy, and the like. Taking a metallurgical process as an example, reliable and continuous metal surface temperature measurement is critical to effective operational control. Effective temperature control can improve the smelting rate, reduce the fuel consumption and prolong the service life of the refractory material. Other industrial processes are similar, and the process can be adjusted in a targeted manner only on the basis of reliably and continuously measuring the surface temperature field of the high-temperature object, so that cost reduction and efficiency improvement are realized.

High temperature objects typically spontaneously radiate visible light. Whereas the radiation intensity of visible light is directly related to the temperature of the light source. Many technologies for measuring the surface temperature of high-temperature objects based on optical methods have been developed at home and abroad. Patent publication No. CN 112556859A discloses a soot flame temperature measurement method, which needs to shoot the same high-temperature surface twice through two filters with similar wavelengths, and the problem is calculated by a colorimetric thermometry method. However, since a certain time is required for replacing the filter, flame stabilization is required. Therefore, the method is only suitable for scenes such as laboratories, has high requirements on environment, and can not continuously acquire temperature.

Patent publication No. CN 101403639A discloses a method for detecting temperature image and blackness image of hydrocarbon flame, which is a temperature measuring method using CCD camera, and by calibrating CCD detector in advance through black body furnace, the function relation between the polynomial of ratio of two primary colors and temperature is fitted. The flame temperature is measured on the basis of the known functional relationship. But since the data utilized by this method is an RGB24 bitmap, the base color values are stored in 8-bit bytes. The data is compressed, and there is some non-linear loss to the original data, which cannot directly reflect the radiation intensity of the flame, and therefore, a large numerical error will be generated to the temperature measurement. When the black body furnace is used for calibration, the ratio of the two primary colors and the temperature are directly regressed, and excessive nonlinearity is interacted with the data for fitting, so that the requirement on the quality of data acquisition is very high, and the model is possibly too complex and has low universality. The method is relatively large in numerical error in comprehensive consideration and is theoretically deficient.

Disclosure of Invention

The invention provides a real-time high-temperature field measuring method based on logarithmic transformation and reciprocal transformation based on the defects of flame temperature measurement in the prior art, the method not only can continuously measure in real time in an industrial scene, but also considers the loss in the image compression process, reduces the error caused by numerical calculation, and has high measuring precision, and the detection error can be lower than 2.2%.

In order to achieve the purpose, the invention adopts the technical scheme that:

a real-time high-temperature field measuring method based on a logarithmic polynomial comprises the following steps:

(1) shooting an original image: shooting a high-temperature object to be detected by using a common camera to obtain an original image;

(2) acquiring an RGB space image: deriving a color filter matrix from the original image obtained by shooting in the step (1), and performing Bayer interpolation to obtain an RGB space image of the high-temperature object to be detected;

(3) calculating the logarithm of the intensity of the primary color r: calculating the proportion of any two primary colors in the RGB space image of the high-temperature object to be detected and taking the logarithm to obtain the logarithm of the intensity ratio of any two primary colors, which is called as the logarithm r of the primary color intensity;

(4) calculating the flame temperature: according to the logarithm r of the intensity of the primary colors and the temperature of the high-temperature object to be measuredAnd calculating the temperature of the high-temperature object to be measured according to the functional relation.

In the step (3), the calculation formula of the logarithm of the intensity of the primary color r is as follows:

r＝ln(R/G)

or, R ═ ln (R/B)

Or, r ═ ln (B/G)

Wherein R, G, B represent the intensity data of the three primary colors, respectively.

Preferably, in the step (3), the same two primary colors are selected for different colors of the high-temperature object to be measured to calculate the logarithm r of the intensity of the primary colors. The stability and accuracy of subsequent temperature calculations can be improved, for example, R and G can be selected for red-yellow flame.

In the step (4), the logarithm r of the intensity of the primary color and the temperature of the high-temperature object to be measuredThe functional relationship of (a) is as follows:

wherein n is the maximum degree of the polynomial, i represents the degree of the polynomial, k_iRepresenting the coefficients of an i-th order polynomial.

Wherein k is_iThe method for acquiring the coefficient comprises the following steps: shooting temperature fields with different temperatures by using a common camera to obtain a series of images with known temperatures, thereby determining the logarithm r of the intensity of the primary colors and the temperature T corresponding to r, and setting an n value according to the nonlinear degree between 1/T and r; after setting n, all k are determined according to the least squares principle_i。

Preferably, n is set according to the degree of nonlinearity between 1/T and r, and the greater the degree of nonlinearity, the greater n is, and n can generally be 2.

Further, k is obtained_iThe specific formula of the coefficients is:

wherein K ═ K₀ k₁...k_i...k_N]K denotes that i is 0,1, …, n_iA constructed vector;

representing a vector formed by the inverses of the temperatures of N samples, T_jRepresents the temperature of the jth sample;

a matrix of polynomials representing the logarithm r of the intensity of the primary colors in N samples,to representThe pseudo-inverse of the matrix.

Wherein the content of the first and second substances,a vector of polynomials representing the logarithm of the intensity of the primary color r of the j-th sample,an i-th polynomial representing the r of the jth sample.

Compared with the prior art, the invention has the following beneficial effects:

compared with other methods, the method fully considers the relation between the data obtained by the optical sensor and the radiation intensity, and reduces systematic errors caused by data storage problems. Meanwhile, the numerical error problem in the calculation process is also considered. The detection error of the temperature can be less than 2.2%.

Drawings

Fig. 1 is a schematic structural diagram of an experimental apparatus of the present invention, in which 1 is a high-temperature object to be measured, 2 is a shooting camera, and 3 is a computer.

Fig. 2 is an original image captured by the camera in the embodiment.

Fig. 3 is an RGB space image obtained in the embodiment.

FIG. 4 is a fitting curve of the logarithm of the intensity of the primary colors r and the temperature T of the black body furnace in the embodiment.

Detailed Description

In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention is further described in detail with reference to the following embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention. Those skilled in the art should understand that they can make modifications and equivalents without departing from the spirit and scope of the present invention, and all such modifications and equivalents are intended to be included within the scope of the present invention.

The structural schematic diagram of the experimental device is shown in fig. 1, wherein 1 is a high-temperature object to be measured, a shooting camera 2 is used for shooting the high-temperature object, and an image of the shooting camera 2 is obtained and calculated through a computer 3.

Examples

In this embodiment, the high-temperature object to be measured is a blackbody furnace, and a digital camera is used to shoot the blackbody furnace, wherein the computer is a computing device integrated with the camera and having a certain computing function. The digital camera used was canon MARK III G7X, which had a color filter matrix arrangement of RGGB with a bayer filter distribution. First, camera parameters of the digital camera are set, a white balance mode is selected on a clear day, exposure compensation is set to 0, sensitivity and shutter speed are set to a manual mode, sensitivity is set to 1/125, and shutter time is set to 1/2000. After the blackbody furnace is shot by using the digital camera, the RAW format data generated by the camera is transmitted to the computer for calculation processing.

Setting the temperature of the black body furnace to rise from 850 ℃ to 1200 ℃ at intervals of 50 ℃, shooting an image at each temperature point, and performing the following steps for each shooting:

firstly, performing Bayer interpolation on RAW format data of an image of an original image shot by a camera to obtain an RGB space image shown in FIG. 3, wherein the RGB space is data of uint16, and the data is stored by double format data to calculate the logarithm r of the intensity of primary colors; in the present embodiment, R ═ ln (R/G) is selected, R, G are intensity data of red and green primary colors, respectively;

then the black body furnace temperature is adjustedIs converted into reciprocal according to the logarithm r of the intensity of the primary color and the temperature of the black body furnaceFunctional relationship of (a):where n is the maximum degree of the polynomial, in this embodiment, the maximum degree n of r is 2, i represents the degree of the polynomial, k_iCoefficients representing an i-th order polynomial;

least squares fitting is performed according to a polynomial of the logarithm of the intensity r of the primary colors, i.e. by a formulaIts parameters are determined. Wherein K ═ K₀ k₁...k_i...k_N]K denotes that i is 0,1, …, n_iA constructed vector;

representing a vector formed by the inverses of the temperatures of N samples, T_jRepresents the temperature of the jth sample;

a matrix of polynomials representing the logarithm r of the intensity of the primary colors in N samples,to representThe pseudo-inverse of the matrix.

Wherein the content of the first and second substances,a vector of polynomials representing the logarithm of the intensity of the primary color r of the j-th sample,an i-th polynomial representing the r of the jth sample.

Finally determining the logarithm r of the intensity of the primary color and the temperature of the black body furnaceThe fitted curve is shown in fig. 4 as follows:

that is to say that the first and second electrodes,

according to the function relation, the temperature of the black body furnace calculated according to the image is obtained, the result of calculation and measurement of the black body furnace is compared with the set value of the black body furnace in the table 1, and the error of the temperature of the black body furnace calculated by the method is less than 1.8 percent as can be seen from the table 1.

TABLE 1 set temperature, calculated temperature and error ratio of blackbody furnace