JPH02105048A - Method for measuring infrared radiation temperature, method for measuring space sensitivity distribution for this method, instrument for measurement and method for measuring thermal diffusivity - Google Patents

Abstract

PURPOSE:To make measurement with high resolution by first measuring the space sensitivity distribution characteristic to an IR detecting system and correcting the actually measured temp. distribution of an object surface by using this distribution at the time of measuring the surface temp. of an object having a temp. distribution by using the detecting system without contact. CONSTITUTION:A slit 34 is first inserted into an optical path in order to form a slender wire-shaped laser beam 32 at the tie of using, for example, a slender thin film-like sample 30 as an object and measuring this surface temp. distribution. The width of the sample 30 is set shorter than the longitudinal size of the beam 32 in order to attain a one-dimensional heat conduction state and further, carbon powder of the extent of not giving influence to the temp. distribution is previously applied on the rear surface of the sample 30 in order to increase the SN at the time of setting a temp. response curve. The temp. of the sample 30 is thereafter changed by using liquid nitrogen and the laser is focused to the prescribed position of the sample by a silicon lens 14. This position is detected by an InSb IR detector 16. The detector 16 is moved to change its position at this time by which the desired temp. distribution is obtd.

Description

[Detailed description of the invention]

[Industrial Application Field 1] The present invention relates to an infrared radiation temperature measurement method for non-contactly measuring the surface temperature of an object having a temperature distribution using an infrared detection system, and a method for measuring a spatial sensitivity distribution characteristic of the infrared detection system. The present invention relates to a method for measuring spatial sensitivity distribution, a measuring device for the measurement, and a method for measuring thermal diffusivity using the infrared radiation temperature measuring method, particularly for non-contact measurement of thermophysical properties of thin film materials using a laser flash method. Suitable for use when
The present invention relates to an infrared radiation temperature measuring method capable of measuring the surface temperature of an object having a temperature distribution with high spatial resolution, a spatial sensitivity distribution measuring method therefor, a measuring device, and a thermal diffusivity measuring method.

[Prior art 1] Measuring the temperature of the surface of an object is an important technology in all industries. For example, it is essential to measure the surface temperature of an object in process control of a manufacturing process or quality control performed by measuring the thermophysical properties of a product. Methods for measuring the surface temperature of an object can be roughly divided into contact methods and non-contact methods. In the former contact type, a temperature sensor such as a thermocouple is brought into direct contact with the object to be measured, and the temperature of the surface of the object is measured. However, with this method, a stable temperature may not be measured and displayed due to the contact surface or contact pressure between the temperature sensor and the surface to be measured. In addition, when measuring the temperature of a minute object, bringing the temperature sensor into contact with it may cause changes in the heat distribution of the object to be measured, making it impossible to accurately measure the temperature of the object. It had some problems. On the other hand, the latter non-contact type, for example,
As disclosed in No. 2, it is intended to capture and measure radiation in the infrared region with a detection element, for example, without bringing a measuring device or a measuring sensor into direct contact with the object to be measured. Compared to the former contact method, this method installs the measuring device near the object, and is used in cases where it is difficult to bring the sensor into contact with the object, or to prevent the sensor itself from disturbing the temperature of the object. It is excellent in that respect. However, when measuring the surface temperature of an object without contact using an infrared detection system, there are the following problems. That is, when emitted light from the surface of an object is focused using a lens and guided to an infrared detector, the spatial resolution of the object to be measured becomes a large value of at least several u, and
．． In a measurement target having a minute temperature distribution on the order of 1 to 0.01 nm, the temperature distribution cannot be accurately measured. For example, as shown in FIG. 7(A), when there is a very narrow high temperature area 12 on the flat plate 10 to be measured, the flat plate 1
When the emitted light from the zero surface is focused using the lens 14 and guided to the infrared detector 16, the actual temperature distribution is as shown in FIG. The temperature distribution measured by the device 16 is as shown in FIG. 7(C), and the detected waveform is blunted, resulting in an inaccurate spatial distribution. In particular, when the high-temperature parts 12 are lined up at a narrower interval than a certain distance, the measured temperature distributions overlap, making it impossible to separate and detect the two, making it difficult to obtain sufficient spatial resolution. could not. (Problem to be achieved by the invention 1) The present invention has been made in order to solve the above-mentioned conventional problems. The first object of the present invention is to provide a measurement method.Furthermore, the present invention is capable of measuring a spatial sensitivity distribution characteristic of an infrared detection system, which is necessary when implementing the infrared radiation temperature measurement method. A second object of the present invention is to provide a spatial sensitivity distribution measuring method.A third object of the present invention is to provide an apparatus for measuring the spatial sensitivity distribution. The fourth object of the present invention is to provide a highly accurate thermal diffusivity measurement method using the infrared radiation temperature measurement method. (Means for achieving the vR problem) The present invention uses an infrared detection system When measuring the surface temperature of an object with a temperature distribution without contact, the spatial sensitivity distribution characteristic of the detection system is measured, and the spatial sensitivity distribution is used to determine the actual temperature of the object surface measured by the detection system. The first object of the present invention is achieved by correcting the distribution to determine the actual temperature distribution on the surface of the object.Furthermore, the present invention also measures the spatial sensitivity distribution characteristic of infrared detection systems. In doing so, a measurement surface is created in which the intensity distribution of the emitted infrared rays changes stepwise, and using the detection system,
A spatial sensitivity distribution of the detection system is determined by measuring a temperature distribution along a direction perpendicular to the boundary line of the measurement surface and differentiating the temperature distribution with a distance from the boundary line of the detection system, This achieves the second problem. Further, the present invention provides a device for measuring the spatial sensitivity distribution characteristic of an infrared detection system, which includes a measurement surface in which the intensity distribution of emitted infrared rays changes in a stepwise manner, and other surfaces surrounding the device. and a temperature adjusting means for maintaining the inside of the constant temperature chamber formed by the measurement surface and the heat insulation surface at a predetermined constant temperature, the third The task has been accomplished. Furthermore, the present invention provides a method for determining the thermal diffusivity of a sample by instantaneously irradiating a thin film sample with a laser beam having a predetermined cross-sectional shape and measuring the temperature rise curve of the sample with an infrared detector. The temperature distribution function due to the temperature rise caused by the irradiation of the laser beam is measured with an infrared detector, including its spatial sensitivity distribution, and the device constants, which are directly related to the thermal diffusivity of the sample, are calculated based on the distance from the laser beam irradiation position. As a function, it is determined by calculating a theoretical temperature distribution function, and from the distance r and the time from the start of laser beam irradiation until the temperature rise reaches half of its maximum value,
The fourth problem has been achieved by determining the thermal diffusivity of the sample. [Function and Effect 1] As shown in Figure 7, the actual temperature distribution is shown in Figure 7 (B).
), the detection system (
If you find the sensitivity corresponding to the distance from the measurement target point (distance between object and lens, lens and detector, lens, detector, etc.) from another measurement target and correct the measured temperature using the sensitivity characteristics, good. That is, for example, as shown in FIG.
0, and using an infrared detection system including a lens 14 and an infrared detector 16, the boundary line 2OA(r-
Temperature distribution function U along the direction (X direction) perpendicular to 0)
(r) is measured. The measured temperature distribution function U (r
) is as shown in FIG. 1(B), for example, and this temperature distribution function U (r ) is as shown in the following equation, assuming that the spatial sensitivity distribution of the detection system is S<×). U(r)=f--1(X)S(x-r)dx
-(1) Here, r is the distance from the boundary line 2OA to the focal point of the measuring optical system in the X direction. In this equation (1), the infrared intensity distribution I(X) is in principle a step function, and can be expressed as, for example, the following equation. Therefore, when formula (1) is differentiated by the distance r, it becomes as shown in the following formula. (aU(r))/(ar)-(a-b)S(+1...
(3) Here, a and b are set temperatures, which can be experimentally set to predetermined temperatures. Furthermore, since U (r ) is known from the measured temperature distribution, the spatial sensitivity distribution S(x) of the detection system can be determined from this equation (3). The spatial sensitivity distribution S (x) of the detection system determined in this way, for example, as shown in FIG.
By substituting the temperature distribution function U D ) as shown in Figure (B) again into the above equation (1), the actual infrared intensity distribution [(X), that is, the temperature distribution, on the surface of the object can be determined. Therefore, the spatial sensitivity distribution 5(X) characteristic of the detection system is measured in advance, and using the spatial sensitivity distribution S (x),
By correcting the actually measured temperature distribution U'(r) on the surface of the object by the detection system, it is possible to obtain the temperature distribution 1-(X) on the surface of the object as shown in FIG. 1(D), for example. The intensity distribution of infrared rays I(X) (FIG. 1(A)) is similar to that of FIG. Therefore, even if the spatial resolution of a single detector is low, it is possible to improve the spatial resolution and accurately measure the temperature distribution even for a measurement target with a temperature distribution. The spatial sensitivity distribution S(×) characteristic of the surface infrared detection system is
For example, it can be measured using an apparatus as shown in FIG. This device consists of a measuring surface 20 in which the intensity distribution of emitted infrared rays changes in a stepwise manner, a heat insulating surface 22 for insulating other surfaces from the surroundings, and the measuring surface 20 and the heat insulating surface 22. A temperature adjusting means for maintaining the inside of the constant temperature bath 24 at a predetermined constant temperature.
and a thermometer 28. The measurement surface 20 is formed of a brass plate with a thickness Q, for example, about 3n, and half of it (the front side in the figure) is uniformly coated with carbon to form the carbon-coated surface 20G of the measurement surface 20. Between the bare brass surfaces 20B, the intensity distribution 1 (X) of the emitted infrared rays changes stepwise, as shown in equation (2) above. This measurement surface 20 is kept at -constant temperature by 126 in the constant temperature bath 24 during the measurement of the temperature distribution function U (r'). The insulating surface 22 can also be made of, for example, foamed plastic to reduce heat leakage. Using such an apparatus, as shown in FIG. 2, a measurement surface 20 is placed in the focal plane of the detection system instead of the sample, and the detection system including the infrared detector 16 and the lens 14 detects the measurement surface 20. The temperature distribution function U (') along the x direction perpendicular to the boundary line 20A (r=o) is measured, and the temperature distribution function U
(r) is the distance r from the boundary line 2OA of the detection system.
By differentiating with , the spatial sensitivity distribution S (
X) can be easily obtained. In addition, by instantaneously irradiating a thin film sample with a laser beam with a predetermined cross-sectional shape and measuring the temperature upper bound curve of the sample with an infrared detector, it is possible to determine the thermal diffusivity of the sample by irradiating it with a laser beam. The temperature distribution function U(αt1r) due to the resulting temperature rise T is measured with an infrared detector while including its spatial sensitivity distribution S(X), and the device constant K(r) is directly related to the thermal diffusivity α of the sample. (3α・t+/
z) is determined by calculating the theoretical temperature distribution function U(αt, r) as a function of the distance r from the laser beam irradiation position, and the distance r and from the start of the laser beam irradiation are The thermal diffusivity α of the sample can be measured with high precision from the time t1/2 until the temperature rise T reaches half of its maximum value. [Example] Hereinafter, an example of the present invention applied to the measurement of the thermal diffusivity of a thin film will be described in detail with reference to the drawings. FIG. 3 shows the principle of a method of measuring the thermal diffusivity of a thin film sample 30 using laser pulse technology according to the present invention. In this measurement method, one pulse of the laser beam 32 is instantaneously irradiated onto the surface of the sample 30. The slit 34 inserted in the middle of the optical path of the laser beam 32 limits the beam shape to linear light that is perpendicular to the longitudinal direction of the sample 30 and in the width direction of the sample 30. It is assumed that the sample 30 is sufficiently thin so that one-dimensional heat conduction occurs in the longitudinal direction. If the measurement time is short, the leakage of heat from the sample 30 can be almost ignored. Therefore, the equation for thermal diffusion is as shown in the following equation. (c)T/c)t) = (x (c)'T/ax
2)-<4) The initial conditions are as shown in the following equation.・・・・・・・・・(5) To=Q/(ρCpd) −−(6) Here,
T is the temperature rise from the initial temperature, α is the thermal diffusivity, °C is the width of the laser beam 32, Q is the amount of heat absorbed by the sample 30 per unit area from the laser beam 32, CP and ρ are the specific heat and density, and d is the Thickness of sample 30, X is laser beam 3
This is distance learning from the center of 2. Assuming that the length of the sample 30 is infinite, the following equation (7) can be found as a solution from equation (4). ψ(crt, x)=1/ET −β′ f−0ψo (0,X+2[happy β)e dβ...
(7) In measuring the thermal diffusivity α by the laser flash method using an infrared detector, the temperature rise T is usually very small compared to the sample temperature itself. Therefore, the signal intensity detected by the infrared detector 16 is approximately proportional to the temperature rise T. On the other hand, the measured temperature distribution function U(αt1r) including the spatial sensitivity distribution S(x) of the infrared detector 16 is as shown in the following equation. U (α(,r) −f−= ψ(αt, x) S (x−r
) dx-<8) The so-called device constant K(r) (3α・j+/2), which is directly related to the thermal diffusivity α of the sample 30, is
Using the following procedure, equation (8) can be converted to laser beam 32
It is determined by numerical calculation as a function of the distance Wir from the irradiation position. That is, the theoretical temperature distribution function U(
α[, r) is calculated for various r as a function of αt. Then, from this curve, for various values of r,
The time t1/2 from the start of pulse irradiation until the temperature rise T reaches half of its maximum value is determined. Then, as a function of the distance r, the device constant K<r) is determined by the following equation. α−K (r) / t+/z −−−(9)
This device constant K(r) is the spatial sensitivity distribution 5 of the detection system.
(x). In this way, the thermal diffusivity α can be easily determined from the detector position (r) and time [1/2] using equation (9). An example of the experimental results will be described below. The experiment was conducted using a thin film sample 30 with a length of 50 mm and a width of 10 n, and in order to form a thin linear laser beam 32, a slit 34 with a width of A -2u was inserted into the laser beam 3.
It was inserted into the optical path of 2. In order to realize a -dimensional heat conduction state, the width (10n) of the sample 30 was set shorter than the length of the laser beam 32 (in the direction perpendicular to the paper plane of FIG. 3). Furthermore, in order to increase the signal-to-noise ratio when measuring the temperature response curve, carbon powder was applied to the back surface of the sample 30 (the lower surface in FIG. 3) to the extent that it did not affect the temperature distribution of the sample 30. The temperature change of such a sample 30 was measured by a 1nsb infrared detector 16 cooled by liquid nitrogen and focused on a predetermined position of the sample 30 by a silicon lens 14. In for infrared detection
Since the diameter of the Sb crystal was approximately 111, the diameter of the detection area on the sample 30 was 0.7 to 0.7 from the geometrical relationship of the optical path.
It was calculated to be in the range of 1.2H. Infrared detector 16
was movable along the X direction parallel to the sample 3o, and its exact position was read with a micrometer. The sample 30 only needs to be at a predetermined position within the focal plane of the detector 16, so there is no need to apply stress or strain to the sample 30. This is particularly useful for fragile samples. First, in order to find the device constant K (r ) in equation (9) above, use the device shown in FIG.
For a temperature range of °C, the temperature distribution function U (r )
When measured, results as shown in FIG. 4(A) were obtained. The spatial sensitivity distribution 5(x) of the detection system numerically calculated from this temperature distribution function U(r) was as shown in FIG. 4(B). FIG. 5 shows the device constant KD) determined from the spatial sensitivity distribution S (x) given by FIG. 4(B). In this example, in order to calculate the thermal diffusivity α of the sample 30, the spatial sensitivity distribution 5 (
Only the relative value of X) is needed. However, in order to evaluate the maximum temperature increase of the entire sample 30, the absolute value of the spatial sensitivity distribution 5(X) is convenient. An example of the measurement results of the temperature response curve of a platinum thin film (thickness: 25 μm) according to this example is shown in FIG. As a result, we obtain a measured value of thermal diffusivity α = 0.210 to 0.293 (on average when the absolute value of distance @r from the laser beam irradiation position is less than 2.8 mm (X = 0.249 cm2/5eC) In addition, a copper thin film (thickness 18 μl 1
), a similar experiment was conducted for thermal diffusivity α=1.
13 to 1.41 (lr l<2.8u on average (X
=1. A measured value of 19 cm'/Sec) was obtained. These values are within the range of recommended values for bulk samples given in the literature (for platinum, 0.239-
0.265. Copper is within 1.12-1.22>. Note that the accuracy decreases as the distance r increases, which is thought to be mainly due to the collapse of the temperature rise curve. In this example, the influence of the spatial sensitivity distribution of the detector is fully included in the device constant K (r ). Therefore, regarding the value of this device constant K (r), it is possible to determine whether the spatial sensitivity distribution is taken into account or if the sensitivity of the detector is 1 in space.
By performing calculations for the case where only a single point is concentrated, it is possible to estimate how much the spatial sensitivity distribution of the detector affects the measurement. Specifically, when the sensitivity of the detector is concentrated only at one point in space, the device constant K (r
) changes by 10%, the value obtained without considering the spatial sensitivity distribution will have an error of 10%. The difference in the value of the device constant K(r) when considering the spatial sensitivity distribution and when the sensitivity is concentrated only at one point in space was calculated for several detector positions r, and the results are shown below. 1
The results shown in the table were obtained. Table 1 It is clear from Table 1 that the shorter the distance r from the center of the laser beam 32, the greater the influence of the spatial sensitivity distribution. In this way, generally speaking, as the distance r from the center of the laser beam 32 increases, the S/N ratio tends to decrease and the data dispersion increases; however, according to this embodiment, when the detector position is 1rl<2 High viscosity data is obtained between .8 and .8. When we examined the data for copper, we found that the recommended value in the literature for the thermal diffusivity α of copper is 1.12 to 1.22, and as shown in Table 2, when the spatial sensitivity distribution of the detector is taken into account, this It is clear that a value close to the recommended value is obtained, whereas an analysis that ignores the spatial sensitivity distribution results in a value larger than the recommended value. As shown in Table 2 and above, it is essential to take the spatial sensitivity distribution of the detector into consideration during measurement in order to perform accurate measurements. In the above examples, the present invention was applied to the measurement of the thermal diffusivity α of the thin film sample, but the scope of the present invention is not limited to this, and measurement from the back or front surface where r=Q is applied. It is obvious that the present invention can be similarly applied to temperature measurement and measurement of the surface temperature of an object having a general temperature distribution.

[Brief explanation of drawings]

FIG. 1 is a diagram for explaining the principle of the infrared radiation temperature measuring method and the spatial sensitivity distribution measuring method according to the present invention, and FIG. 2 is a diagram showing the configuration of the spatial sensitivity distribution measuring device according to the present invention. FIG. 3 is a diagram showing the principle of an embodiment of the method for measuring thermal diffusivity of a thin film sample according to the present invention; FIG. 4 is a diagram showing the temperature distribution function U(r) and spatial sensitivity in the embodiment. FIG. 5 is a diagram showing an example of the measurement result of the distribution S(x), FIG. 5 is a diagram showing an example of the measurement result of the device constant K (r ), and FIG. 6 is a diagram showing the measurement result of the temperature response curve. Diagram showing an example FIG. 7 is a diagram comparing and showing an example of the temperature measurement state by the infrared detector, the actual temperature distribution, and the measured temperature distribution. 14... Lens, 16... Infrared detector, 20... Measurement surface, 2OA... Boundary line, 20B... Brass surface, 20C... Carbon coated surface, 22... Heat insulation surface, 24 ... Constant temperature bath, 26 ... Hot water, 28 ... Thermometer, 1 (x) ... Infrared intensity distribution, U ('') ...
Measured temperature distribution function, S(x)...Spatial sensitivity distribution of detection system, 30...Sample, 32...Laser beam, 34...Slit, K(r)...Device constant, [1/2...Time until the temperature rise reaches half of its maximum value, α...Thermal diffusivity.

Claims (4)

[Claims] (1) When measuring the surface temperature of an object with a temperature distribution in a non-contact manner using an infrared detection system, a spatial sensitivity distribution characteristic of the detection system is measured, and the spatial sensitivity distribution is used for detection. An infrared radiation temperature measurement method characterized by determining the actual temperature distribution on the surface of an object by correcting the measured temperature distribution on the surface of the object using a system. (2) When measuring the spatial sensitivity distribution characteristic of an infrared detection system, create a measurement surface where the intensity distribution of the emitted infrared rays changes stepwise, and use the detection system to measure the boundary line of the measurement surface. Spatial sensitivity distribution measurement characterized by determining the spatial sensitivity distribution of the detection system by measuring the temperature distribution along orthogonal directions and differentiating the temperature distribution with respect to the distance from the boundary line of the detection system. Method. (3) A device for measuring the spatial sensitivity distribution characteristic of infrared detection systems, which includes a measurement surface in which the intensity distribution of emitted infrared rays changes in a step-like manner, and another surface from the surroundings. A spatial sensitivity distribution characterized by comprising: a heat insulating surface for heat insulation; and a temperature adjustment means for maintaining the inside of a constant temperature chamber formed by the measurement surface and the heat insulating surface at a predetermined constant temperature. Measuring equipment. (4) Thermal diffusivity measurement in which the thermal diffusivity of the sample is determined by instantaneously irradiating a thin film sample with a laser beam with a predetermined cross-sectional shape and measuring the temperature rise curve of the sample with an infrared detector. In this method, the temperature distribution function due to the temperature rise caused by laser beam irradiation is measured with an infrared detector, including its spatial sensitivity distribution, and the device constants directly related to the thermal diffusivity of the sample are determined by the laser beam irradiation. It is determined by calculating a theoretical temperature distribution function as a function of the distance from the irradiation position of A thermal diffusivity measuring method characterized by determining the thermal diffusivity of a sample from time.