TWI465702B - Non-contact temperature measurung method - Google Patents

Description

Non-contact temperature measurement method

This application relates to a temperature measurement method, and more particularly to a non-contact temperature measurement method.

High-temperature industrial process systems, such as industrial steelmaking furnaces, thermal power plants, and combustion furnaces. In the production process, it is often necessary to monitor the distribution of production equipment and product temperature, such as furnace wall temperature and steel embryo temperature. The temperature of the furnace wall is measured to avoid damage to the structure of the furnace due to excessive temperature of the furnace wall, and the temperature of the steel preform can be measured to pre-determine the quality of the product, thereby changing the operation setting and improving the product yield.

The temperature measuring device is divided into two types of contact type and non-contact type. Among them, the traditional contact type temperature measurement method is mainly composed of high temperature thermocouple. However, contact-type high-temperature thermocouples have a slow temperature response and can only be measured at a single point, which has limited help in the adjustment and monitoring of high-temperature processes.

In addition, the non-contact measurement method often absorbs the radiant energy of the target object by the visible light camera, and then uses the algorithm to calculate the temperature field representing the temperature distribution of the entire image. However, during the measurement process, the visible light camera records all objects with visible wavelengths in the image, including non-quantity objects, such as moisture, light reflectors or other background light sources. In addition, objects that affect temperature calculations can interfere with or obscure high-temperature measurement targets. For example, in the steel industry, steel billets in the process will adhere to the surface of the steel in the form of Scaling. Once the scale is not finished Fully rinse off, when detecting the temperature of the steel embryo, the scale will shield the steel embryo from affecting the temperature measurement result, making the temperature information invalid or abnormal.

The present application provides a temperature measurement method capable of removing an erroneous temperature measurement point when calculating a target temperature to be measured by using a visible light camera to increase the accuracy and correctness of the measurement temperature.

The present application proposes a temperature measurement method, including photographing a target to be measured to obtain a visible light image. The visible light image includes a plurality of pixels, each of which has image data. The image data of each pixel includes brightness of a plurality of different wavelengths. Then, a plurality of effective pixels are captured in the pixels of the visible light image, and at least one luminance ratio between different wavelengths in the effective pixel is between a certain value ± a allowable fluctuation value. And, the temperature values of the plurality of positions corresponding to the effective pixels in the object to be tested are calculated according to the image data of the effective pixels.

Based on the above, the temperature measurement method of the present application obtains a visible light image by capturing a target to be tested, and extracts effective pixels by determining a luminance ratio of each pixel in different wavelengths in the visible light image. These effective pixels can be used to calculate temperature values of a plurality of locations corresponding to the plurality of effective pixels in the object to be tested. The temperature measurement method of the present application can avoid the pixels of the abnormal measurement points generated by water vapor, easy-reflecting objects or other background light sources in the calculation process when calculating the target temperature to be tested, thereby causing the target to be tested. The calculation result is too large with the actual temperature error.

The above-described features and advantages of the present application will become more apparent and understood.

1 is a flow chart of a temperature measurement method according to an embodiment of the present application. 2A is a schematic diagram of a visible light image capturing environment. 2B is a schematic view of the visible light image of FIG. 2A. In the present embodiment, the main flow of measuring the temperature distribution in the object 10 to be tested includes taking the object 10 to be measured to obtain the visible light image I in step S101, and the object 10 to be tested is, for example, the temperature field of the steel blank 12 for discharging. The visible light image I includes a plurality of pixels P, and each pixel P has image data, and the image data includes brightness of a plurality of different wavelengths, for example, brightness of the first wavelength B, brightness of the second wavelength G, and brightness of the third wavelength R. Next, in step S102, a plurality of effective pixels P1 are extracted from the plurality of pixels P of the visible light image I, and at least one luminance ratio between different wavelengths in the effective pixel P1 is between a certain value ± an allowable fluctuation value. Moreover, in step S104, the temperature values of the plurality of positions corresponding to the effective pixels P1 in the object to be tested 10 are calculated according to the image data of the effective pixels P1.

3 is a graph showing the relationship between the luminance ratio of the two-color wavelength and the temperature in the visible light image of the present embodiment. Referring to FIG. 1 , FIG. 2B and FIG. 3 , in the embodiment, each pixel P of the visible light image I has a first wavelength B such as blue light, a second wavelength G such as green light, and a third wavelength R is, for example, Red light. It can be seen from FIG. 3 that, with the increase or decrease of the temperature, the visible light image I captured by the visible light camera 100 has a luminance ratio of the third wavelength R to the first wavelength B which is substantially maintained at a certain value ± a permissible fluctuation value range. There is not much variation within, and the setting is, for example, a value between 0.5 and 1.5, and the allowable fluctuation value is, for example, 10% of the value. In addition, the luminance ratio of the third wavelength R to the second wavelength G decreases as the temperature increases. Less, the luminance ratio of the second wavelength G to the first wavelength B increases as the temperature increases.

The temperature measurement method of the embodiment can obtain a visible light image I by using the visible light camera 100, and capture the effective pixel P1 in the visible light image I, wherein the ratio of the brightness of the third wavelength R of the effective pixel P1 to the first wavelength B is substantially Maintain between 1 ± 10% (that is, the value is 1 and the allowable fluctuation value is 10% of the fixed value). Specifically, in this embodiment, the effective pixel P1 can be extracted from the plurality of pixels P of the visible light image I by maintaining at least one luminance ratio of the effective pixel P1 within a range of a certain value ± a allowable fluctuation value. The temperature distribution calculation of the object 10 to be tested is performed using these effective pixels P1. Therefore, in the embodiment, the effective pixel P1 may be a pixel in the visible light image I, and the luminance ratio of the third wavelength R to the first wavelength B ranges from 0.9 to 1.1. Selecting the effective pixel P1 of the specific brightness ratio range in the visible light image I can improve the accuracy of the temperature distribution calculation. Therefore, the temperature measurement method of the embodiment can avoid the invalid pixel P2 in the combustion process, such as water vapor, easy-reflecting object or other background light source, being included in the calculation when calculating the temperature distribution of the object 10 to be tested, resulting in waiting The temperature distribution calculation result of the measurement target 10 is too large with the actual temperature error.

In other words, when the target 10 to be tested is photographed, the pixels of the abnormal measurement points generated by water vapor, easy-reflecting objects or other background light sources in the production process are often recorded in the visible light image I, and the optical characteristics of the pixels are Does not match the optical characteristics of the ideal measurement point. In this embodiment, it is determined whether the luminance ratio of the third wavelength R and the first wavelength B of each pixel in the visible light image I conforms to the trend of FIG. 3 (for example, between 0.9 and 1.1). The pixel of the constant point. Specifically, when the luminance ratio of the third wavelength R to the first wavelength B in the pixel P does not conform to the trend shown in FIG. 3, it is regarded as an invalid pixel P2, and is excluded when the effective pixel P1 is captured. These invalid pixels P2 are used to improve the accuracy of the temperature calculation of the target 10 to be tested.

4 is a diagram showing the relationship between brightness and temperature of a specific wavelength in a visible light image of the present embodiment. Referring to FIG. 1 , FIG. 2B and FIG. 4 , after capturing the effective pixel P1 from the visible light image I by the luminance ratio, a step S103 is further included to reserve the first portion S1 of the effective pixel P1, and the second portion is filtered out. The effective pixel P1 of S2. The luminance of the specific wavelength of the effective pixel P1 of the first portion S1 is within a luminance range R1, and the luminance of the specific wavelength of the effective pixel P1 of the second portion S2 is outside the luminance range R1. In other words, in the present embodiment, step S103 is to exclude pixels in the visible light image I whose luminance is too saturated and whose luminance is small.

In this embodiment, the specific wavelength is, for example, the third wavelength R of the selected wavelength of red light, as viewed in FIG. 4, when the luminance of the red light is small (for example, the luminance is lower than 50) and the saturation is close to (for example, the luminance is greater than 240). When the linear relationship between brightness and temperature is less obvious, the deviation of temperature calculation will be larger. Conversely, when the luminance is between the luminance ranges R1, for example, between 50 and 240, the luminance and temperature changes are substantially linear. Generally, when sensing a high temperature target, the brightness of the third wavelength R emitted by the measurement target point is generally large, so the third wavelength R is suitable as a specific wavelength that is supersaturated or insufficiently bright. However, the application is not limited herein. In other embodiments, the specific wavelength may also be the second wavelength G of the green light or the first wavelength B of the blue light, and the filtering brightness may be supersaturated or A specific wavelength with insufficient brightness. When the specific wavelength is the second wavelength G (i.e., the green wavelength), the luminance ranges from 50 to 240. When the specific wavelength is the first wavelength B (ie, the blue wavelength), the luminance ranges from 50 to 240.

In the visible light image I, the visible light image I includes an erroneous pixel in addition to the above-mentioned invalid pixel P2, and these erroneous pixels still affect the calculation of the temperature of the target 10 to be tested. Taking the process of producing steel bars as an example, the process of heating the steel blank 12 in the heating furnace, the impurities on the steel blank 12 are attached to the surface of the steel blank 12 in the form of scale. These scales are often washed away in a high-pressure water column in the back-end process and then rolled. However, if the scale cannot be completely washed away, when the temperature of the steel blank 12 is detected, the scale will shield the steel embryo 12 from affecting the temperature measurement result, making the temperature information invalid or abnormal. Therefore, in this embodiment, the first portion S1 of the effective pixel P1 is selected by using the brightness range R1 of the specific wavelength in step S103, so as to filter the shadow point of the object to be tested that covers the high temperature object, thereby improving the measurement accuracy. .

In addition, the embodiment may further select to repeat the above steps at least once to further filter out effective pixels outside the brightness range of other specific wavelengths. In other words, after screening the first portion S1 of the effective pixel P1 that meets the luminance range R1 of the third wavelength R, the first portion S1 of the remaining effective pixels P1 may be similar to the second wavelength G or the first wavelength B. Filter to further filter the effective pixels P1. This embodiment does not limit the wavelength range selected for this screening step and the number of screenings.

Continuing to refer to FIG. 1 and FIG. 2A , in the embodiment, after the step S104 is performed to calculate the temperature values of the plurality of positions corresponding to the effective pixels P1 in the target 10 to be tested, the method further includes a step S105 of outputting the target 10 to be tested. Temperature distribution image. Step S105 is, for example, connecting the visible light camera 100 to a computer device 200. The computer device 200 can not only calculate the temperature values of the plurality of locations in the target 10 to be tested, but also construct a temperature distribution in the visible light image I according to the temperature values. To output a temperature distribution image of the target 10 to be tested.

The calculation method of the temperature distribution of the target 10 to be tested can be calculated by using the existing two-color method or the three-color method. An embodiment will be described below to describe the method of temperature calculation. The method for calculating the temperature in the present embodiment is a calculation formula improved by the two-color method as shown in the equation (1).

In the equation (1), λ ₁ is the above-described second wavelength G, and λ ₂ is the above-described third wavelength R. (T) is the brightness corresponding to the second wavelength G, (T) is the brightness corresponding to the third wavelength R, A is the correction coefficient, S ₁ is the shutter time when the visible light image I of the second wavelength G is captured, and S ₂ is the visible light image I when the third wavelength R is extracted The shutter time, C is a constant, and the constant C = hc / k, where h is the Planck constant, c is the speed of light, and k is the Boltzmann constant. In this embodiment, the reason why the second wavelength G and the third wavelength R are selected as the two colors calculated by the temperature is that, in a general high temperature object, the brightness of the first wavelength B is compared with the second wavelength G and the third The wavelength R is low, which is less suitable for measuring brightness and calculating. Further, in FIG. 3, the luminance ratios of the second wavelength G and the third wavelength R are linear with respect to temperature. It is therefore suitable to apply the two wavelengths required to calculate the target 10 to be measured in the two-color method. However, in other embodiments, any two wavelengths may be selected for the two-color method calculation, and is not limited thereto.

In addition, according to equation (1), the correction coefficient A is the only parameter to be determined. If the correction coefficient A is determined, the equation (1) can be used as the theoretical basis for the calculation of the target 10 to be tested. Because the correction coefficient A has the physical model of equation (1). Therefore, the method for obtaining the correction coefficient A includes: providing a plurality of correction points of a known temperature, respectively capturing images of the correction points, selecting a correction wavelength in the image to obtain a corrected brightness corresponding to the corrected wavelength, and corresponding Corrected brightness at an unknown wavelength. Then, the correction coefficient A can be obtained by the following equation (2).

Where T _ref is the correction point temperature, λ ₃ is the correction wavelength, λ ₄ is the unknown wavelength, S ₃ is the shutter time when the visible light image I of the correction wavelength is captured, and S ₄ is the visible light image I of the unknown wavelength Shutter time, (T _ref ) is the corrected brightness of the corrected wavelength, (T _ref ) is the corrected brightness of the unknown wavelength, C is a constant, the constant C=hc/k, where h is the Planck constant, c is the speed of light, and k is the Boltzmann constant. According to this, the temperature distribution of the target 10 to be tested can be calculated.

In summary, the temperature measurement method of the present application obtains a visible light image by capturing a target to be tested, and extracts effective pixels by determining a luminance ratio of each pixel in different wavelengths in the visible light image. These effective pixels can be used to calculate a plurality of positions in the object to be tested corresponding to the plurality of effective pixels Temperature value. The temperature measurement method of the present application can avoid the pixels of the abnormal measurement points generated by water vapor, easy-reflecting objects or other background light sources in the production process when calculating the target temperature to be tested, thereby causing the target to be tested. The calculation result is too large with the actual temperature error. In addition, the present application is capable of selecting a first portion of the effective pixels by using a luminance range of a specific wavelength to filter a shadow point of the object to be tested that covers the high temperature object, thereby improving measurement accuracy. In addition, it is more optional to repeat the foregoing steps at least once to further filter out effective pixels outside the brightness range of other specific wavelengths.

Although the present application has been disclosed in the above embodiments, it is not intended to limit the present application, and any person skilled in the art can make some changes and refinements without departing from the spirit and scope of the present application. The scope of protection of this application is subject to the definition of the scope of the patent application.

10‧‧‧ target to be tested

12‧‧‧ steel embryo

100‧‧‧ visible light camera

200‧‧‧Computer equipment

I‧‧·visible light image

P‧‧ ‧ pixels

P1‧‧‧ effective pixels

P2‧‧‧ invalid pixels

R1‧‧‧Brightness range

B‧‧‧First wavelength

G‧‧‧second wavelength

R‧‧‧ third wavelength

S1‧‧‧Part 1

S2‧‧‧ Part II

S101~S105‧‧‧Steps

1 is a flow chart of a temperature measurement method according to an embodiment of the present application.

2A is a schematic diagram of a visible light image capturing environment.

2B is a schematic view of the visible light image of FIG. 2A.

3 is a graph showing the relationship between the luminance ratio of the two-color wavelength and the temperature in the visible light image of the present embodiment.

4 is a diagram showing the relationship between brightness and temperature of a specific wavelength in a visible light image of the present embodiment.

S101~S105‧‧‧Steps

Claims (11)

A temperature measurement method includes: capturing a target to be measured to obtain a visible light image, the visible light image comprising a plurality of pixels, each of the pixels having an image data, the image data comprising brightness of a plurality of different wavelengths; Extracting a plurality of effective pixels from the pixels of the image, wherein at least one luminance ratio between the different wavelengths in the effective pixels is between a certain value ± an allowable fluctuation value; and the image according to the effective pixels The data is used to calculate temperature values of the plurality of locations corresponding to the effective pixels in the object to be tested. The temperature measurement method of claim 1, further comprising: after capturing the effective pixels, retaining a first portion of the effective pixels, and filtering out a second portion of the effective pixels, wherein The brightness of a specific wavelength of the effective pixels of the first portion is within a range of brightness, and the brightness of the specific wavelength of the effective pixels of the second portion is outside the brightness range, and the portions of the first portion are The effective pixels are used to calculate temperature values of the plurality of positions corresponding to the effective pixels in the object to be tested. The method for measuring temperature according to claim 2, further comprising the step of repeating the application of claim 2 at least once, filtering out the effective pixels outside the brightness range of other specific wavelengths. The temperature measuring method according to claim 2, wherein the specific wavelength is a blue light wavelength, and the brightness range is 50 to 240. The temperature measuring method according to claim 2, wherein the specific wavelength is a green light wavelength, and the brightness range is 50 to 240. The temperature measuring method according to claim 2, wherein the specific wavelength is a red wavelength, and the brightness ranges from 50 to 240. The temperature measuring method according to claim 1, wherein the value is a value between 0.5 and 1.5, and the allowable fluctuation value is 10% of the value. The temperature measurement method of claim 1, wherein the image data includes a first wavelength, a second wavelength, and a third wavelength, the first wavelength is blue light, and the second wavelength is green light, The third wavelength is red light, and the ratio of the brightness of the third wavelength to the first wavelength is between 0.9 and 1.1. The temperature measurement method of claim 1, further comprising outputting a temperature distribution image of the object to be tested after calculating the temperature values of the effective pixel positions. The temperature measurement method of claim 1, wherein the image data comprises a first wavelength, a second wavelength and a third wavelength, the first wavelength is blue light, and the second wavelength is green light, The third wavelength is red light, and the method for calculating the temperature value corresponding to the effective pixel positions in the object to be tested according to the image data of the effective pixels comprises: calculating the temperature of each effective pixel according to the following equation : Where λ _{1 is} the second wavelength and λ _{2 is} the third wavelength, (T) is a brightness corresponding to the second wavelength, (T) is the brightness corresponding to the third wavelength, A is a correction coefficient, S ₁ is the shutter time when the visible light image of the second wavelength is captured, and S ₂ is the time when the visible light image of the third wavelength is captured Shutter time, C is a constant, the constant C = hc / k, where h is the Planck constant, c is the speed of light, and k is the Boltzmann constant. The method for measuring temperature according to claim 10, wherein the method for obtaining the correction coefficient A comprises: providing a plurality of correction points of a known temperature; separately capturing images of the correction points, and selecting a correction in the image a wavelength to obtain a corrected brightness corresponding to the corrected wavelength and a corrected brightness corresponding to an unknown wavelength; and calculating a relationship between the correction coefficient A and the unknown wavelength according to the following equation: Where T _ref is the correction point temperature, λ _{3 is} the correction wavelength, λ _{4 is} the unknown wavelength, S ₃ is the shutter time when capturing the visible light image of the correction wavelength, and S ₄ is the visible light image capturing the unknown wavelength Shutter time, (T _ref ) is the corrected brightness of the corrected wavelength, (T _ref ) is the corrected brightness of the unknown wavelength.