JPS6049853B2 - How to measure object surface temperature - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for radiometrically measuring the surface temperature of an object, particularly an object in a furnace.

The present applicant has already proposed a method of measuring the surface temperature of a steel plate being annealed by radiation as shown in FIG. 1 (Japanese Patent Application No. 55-27108).

In this figure, 10 is a steel plate, 12 is a development furnace, 16 is a radiometer, N is the normal line erected at the temperature measurement point PT, θ1, θ. is the angle formed by the straight line connecting the exfoliating furnace 12, the radiometer 16, and the temperature measurement point PT with the normal N, and is selected to be θ, = θ2. In this measurement system, the temperature of the steel plate 10 is Tl, the emissivity is E_), and the temperature of the extrusion furnace 12 is T. Then, the radiant energy E_, received by the radiometer 16 is E_, ■E_-E_b(Tl)+(
1-E_)E_b(T0) (1).

Here, E_b(T) is the radiant energy emitted by expansion at temperature T. If the temperature of the exhibition furnace 12 is set to T3, the radiant energy E_2 received by the radiometer 16 at that time is E_2■ε
・E_b(Ti) 10(1-E_)E_b(T3)...
...(2).

In these equations, the unknowns are ε and Tl, so (1), (2
) can be solved, E_, -E_2 E_■1-... (3) E_■T2) Upper b(T0) E_01-E_ E_b(T, )=----・E_b(T3 )・・・・・・
・(4) becomes.

If E_b(Tl) is known, Vienna's formula E_b(T)■
Temperature T from Clλ-゜exp(-Co/λ・T) etc.
is required. The above discussion is based on an ideal situation, and in reality various corrections are required.

For example, the second term on the right side of equation (2) assumes that the radiant energy from the development furnace is specularly reflected on the steel plate surface and input to the radiometer 16, but in reality, the steel plate surface is completely It is not a mirror surface, but produces some diffused reflection. This means that (1-E_) becomes smaller, and it is necessary to introduce a coefficient f such that 0<f<1 to correct it to f(1-ε). This coefficient f can be called the specular reflection coefficient. Also, if the steel plate surface is not a perfect mirror, it is necessary to take into account the amount of radiant energy from the furnace wall that is diffusely reflected on the steel plate surface and enters the radiometer.This amount is (1-E_)p)E_b(T0) It is expressed as Here, p is the diffuse reflection coefficient of the surface of the steel plate, and has a relationship with the coefficient f as f+p=1. T4 is the temperature of the furnace wall. When this is corrected, equations (1) to (4) become as follows.

This is the measurement principle of the above-mentioned application.
) can be configured or changed as appropriate. It is also possible to set Eb(T3)±0, which simplifies the equation. By the way, solving (5) and (6) above gives (7),
When calculating equation (8), the unknowns in the above application are ε and T1.
, and other values are known (measured values or set values).

However, the diffuse reflection coefficient p varies greatly in the range of 0 to 1 depending on the surface properties (roughness, etc.) of the object. Therefore, the use of estimated values may lead to large measurement errors in some cases. The present invention aims to improve this point by measuring the diffuse reflection coefficient on-line, and by knowing the accurate error coefficient of the fluctuating temperature measurement object, it is possible to measure the temperature with high accuracy.

That is, in the measurement method of the present invention, a radiometer and a blackbody furnace are connected to an object, and radiant energy from the object is directly incident on the radiometer, and radiant energy from the blackbody furnace is incident on the object surface after specular reflection. and radiant energy from the blackbody furnace. - is changed to two types: low and high temperature, the radiometer reception energy E1 at the low temperature and the radiometer reception energy E2 at the high temperature are measured, and the light is projected onto the object surface and reflected specularly. Find the ratio of the light 11 and the surrounding diffuse reflection light 12, find the diffuse reflection coefficient p of the surface of the object from this ratio U2/11, and calculate the ratio of the object from the received light energies El, E2 and the diffuse reflection coefficient p. This method is characterized by determining the surface temperature. Next, a method for measuring the diffuse reflection coefficient will be explained. Figure 2 shows the principle of this measurement method.

That is, in this measurement, as shown in figure a, light B is projected onto the surface of the object from the light projector A, and the reflected light B'' is measured by the light receiver C. At the light receiver, the specular reflection 11 and the surrounding diffusion are detected. Find the ratio 12/11 with the reflected light 12. This ratio corresponds to the diffuse reflection coefficient p as described below, and p The coefficient (1-p) necessary for calculating the above equations (5) and (6) is the ratio of the incident light L and the specularly reflected light 11.
/10.

That is, if the light that is diffusely reflected from the surface of an object (excluding specular reflection) is ΔI, then I. =11+Δ11 Therefore.

Since the light 12 to be measured at the light receiving part C is a part of ΔI, Δ
If we set I=I2+α, we can obtain the right-hand side of the above equation (1a),
As is clear from the right side of equation (10), p=12/1
The measurement method that assumes 1 has a slight error due to α, 12, but in a state close to specular reflection, α″.0,120 α′−11
Therefore, the above error is small. And I. 12 compared to
can be measured very easily as described below. (1-p)
When measuring directly, equation (9) can be modified as follows.

In the light projecting section A, the light B is transmitted as a narrow beam type as shown in Figure 3a, and as a thick beam type as shown in Figure 3b.
Alternatively, as shown in FIG. 3C, the light is projected onto the object 10 as a conical or pyramidal beam converging at one point at the temperature measurement point PT.

In case a, it is appropriate to use laser light, but normal visible light may also be illuminated with a lens or the like. In case b, eight large-diameter parallel beams are created using a laser beam, a beam expander, and a lens, or an incandescent lamp, a lens, or a mirror system.
In the case of c, the beam is shaped into a cone or the like using similar means. The light receiving section C is constructed as shown in FIG. Figure a shows a rotating sector mainly consisting of a disk with a hole h in the center, and a disk-shaped light receiver 2.
2 is used, and when the rotating sector 20 is placed in the position shown, only the specularly reflected light passes through the hole h (so that the hole diameter,
The other reflected light is blocked by the rotating sector 20 and reaches the light receiver 22 at the rear (determining the sector position).
2, and therefore the output of the light receiver 22 corresponds to the specularly reflected light component 11. Next, when the rotating sector 20 is rotated and removed from the front of the light receiver 22, the light receiver 22
The specular reflection component 11 and the reflected light around it, more specifically, the reflected light within the solid angle that the photoreceiver 22 extends to the temperature measurement point PT (this is referred to as 13), enter the photoreceiver 22, and the output of the photoreceiver is 13. It corresponds to Therefore, the ratio is 1. /11 is (L3-11
)/11, if the rotating sector is also used as a light receiving element, its output will be 12, so 12/11 can be immediately determined as the ratio of the outputs of the members 20 and 22. Since the diameter of the hole h is selected so that only specularly reflected light passes through it, it is small when the incident light is a small diameter beam, and becomes large when the incident light is a large diameter beam.

A lens may be placed at the position of the light receiver 22 to condense light and project it onto a small light receiver for measurement. Figure 4b shows a ratio of 12/11 due to the dotted light receiving elements 24 arranged in a cross shape.
Measure.

That is, since the intensity distribution of the reflected light is distributed in the X and Y directions as shown in Figures C and D, the specular reflection component 11 and the surrounding reflection component 12 are determined by integrating the light reception output of this light receiving element array. be able to. Instead of providing a large number of light-receiving elements 24, one element is used, and it is aligned in the array direction, that is, in the
Scanning may also be performed in the y direction. Fig. 4e shows a modification of Fig. 4a, in which lenses 26 and 28 are arranged before and after the movable sector 20,
A small light receiving element 30 is placed behind the lens 28.

A lens 20 converts the reflected light into a parallel light beam, a lens 28 collects the light, and projects it onto a light receiving element 30 . When the sector 20 is rotated or moved straight and inserted into the parallel beam as shown, the output of the light receiving element 30 is 11, and when it is removed, the output is 11+12, and from this, the ratio 12/11 can be determined. FIG. 4f shows an example of determining the ratio between total reflected light and specular reflected light using a concave reflecting mirror 32 having an aperture.

That is, when this reflecting mirror 32 is removed, only the specularly reflected light 11 enters the light receiving element 30 (the size of the light receiving surface of the light receiving element 30 is selected in advance), and when the reflecting mirror 32 is placed at the position shown in the figure, The reflected light that enters through the aperture h1 and is specularly reflected on the object surface enters the light receiver 30 through the aperture H2, and the incident light that is diffusely reflected in various directions on the object surface is reflected by the reflecting mirror 32 and reaches the object surface 10. The light is returned, where it is reflected again, and thus enters the light receiver 30 through the aperture H2 after multiple reflections. The output of the photoreceiver in this case is ~11+I2, but if the degree of diffuse reflection on the object surface is significant, 12 is larger than in cases such as those shown in FIGS. 4A and 4B. FIG. 4g shows an example in which infrared rays are used instead of visible light, and a silicon cell is used as the light receiving element and is made movable.

4 is a black body furnace, and 36 is a light receiver consisting of a silicon cell.

A conical infrared ray (radiant energy) is irradiated from the black body furnace 34 to the temperature measuring point PT of the object 10, and this specularly reflected light is received by the light receiver 36. For this purpose, only the specularly reflected light may be set within the solid angle Ω1 that the photoreceiver extends to the temperature measurement point PT at the illustrated photoreceiver position (the photoreceiver position etc. may be determined in this way). Next, the light receiver 36 is advanced to the dotted line position so that the solid angle Ω2 extending to the temperature measurement point becomes larger than Ω1. In this way, the aforementioned 11+I2 can be measured. In Figure 5, the reflection angle θ is 300, the wavelength λ of the infrared ray used is 0.9 μm1Ω1=0.001π [Sr],
The relationship between the diffuse reflection coefficient p and the intensity ratio 12/11 when Ω2=0.01π [Sr] is shown.

This is a specific example of FIG. 2b. FIG. 6 shows an embodiment of the invention.

40 is a continuous annealing furnace, and in this example, the steel plate 10, which is a strip, is continuously annealed.

42 is a furnace 40 equipped with the above-mentioned measuring device for the diffuse reflection coefficient p.
installed on the entrance side.

44 is the sensor section of the radiation thermometry device shown in Fig. 1, '46
calculates strip 1 by performing the calculations in equations (7) and (8) above.
There is a calculation device that produces the emissivity E and temperature T of 0.

The p-value measuring device 42 may be installed on the outlet side of the annealing furnace 40 in parallel with the sensor section 44 of the radiation temperature measuring device, and this allows for more accurate temperature measurement when the p-value changes rapidly. As explained above, according to the present invention, it is possible to accurately measure the temperature of an object using the radiation thermometry method shown in FIG. have

9 Brief description of the drawings Fig. 1 is a diagram explaining the principle of radiation temperature measurement that has already been proposed, Fig. 2 is a diagram explaining the measurement procedure of the present invention, and Fig. 3 is a diagram showing various examples of projected light. FIG. 4 is an explanatory diagram showing various examples of the light receiving section, FIG. 5 is a graph showing an example of P-12/11 characteristics, and FIG. 6 is an explanatory diagram showing an example of the present invention. be.

In the drawing, 16 is a radiometer, 12 is a blackbody furnace, 10 is an object, B is a projected light, and B'' is a reflected light.

Claims (1)

[Claims] 1. A radiometer and a blackbody furnace are arranged with respect to an object so that radiant energy from the object directly enters the radiometer, and radiant energy from the blackbody furnace enters the object after specular reflection on the surface of the object, And by changing the radiant energy from the blackbody furnace into two types: low and high temperature, the radiation energy received by the radiometer at the low temperature E
_1 and the radiometer received light energy E_2 at high temperature, and also calculate the ratio of the specularly reflected light I_1 by projecting light onto the surface of the object and the surrounding diffusely reflected light I_2, and calculate the ratio I_2/
A method for measuring the surface temperature of an object, characterized in that the diffuse reflection coefficient p of the surface of the object is determined from I_1, and the surface temperature of the object is determined from the received light energies E_1 and E_2 and the diffuse reflection coefficient p.