JP2005291711A - Calibration method and calibration apparatus of radiation thermometer - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a calibration method and a calibration apparatus for obtaining the high calibration precision of a radiation thermometer at a high temperature of 1,000°C or higher. <P>SOLUTION: A first split light 18b and a second split light 18a divided into two portions by a half mirror 20 are applied to the focusing surface of a standard radiation thermometer 26 and a dichroic camera 16, namely a light detection surface 50, or the like. When each radiation intensity is measured, each pair of measurement values measured simultaneously (namely, a radiation intensity ratio R and a standard radiation thermometer output temperature T<SB>std</SB>) is stored. Therefore, light on one optical axis 18 is divided for vertically entering the standard radiation thermometer 26 and the dichroic camera 16, thus appropriately excluding an error caused by the difference in the bottom surface of a blackbody furnace 12 to be prescribed, and appropriately excluding the influence of fluctuation in time since measurement is made simultaneously by the standard radiation thermometer 26 and the dichroic camera 16. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a calibration method and a calibration apparatus for calibrating a radiation thermometer with high accuracy.

  Non-contact temperature measurement is widely used because it is industrially useful. In such a non-contact type temperature measurement, a radiation (radiation) thermometer using a one-color method, a radiation temperature by a multicolor method (for example, two-color method) obtained from a ratio of radiant energy intensities of two or more wavelengths (For example, refer to Patent Document 1). In the radiation thermometer using the former one-color method, the temperature is measured by comparing the value of the radiant energy from the member to be measured with respect to the radiation of the black body as a reference. Therefore, since it is necessary to set and input the emissivity, it is not suitable for measuring the temperature of the member to be measured whose emissivity changes, but there is an advantage that it can be easily measured. In contrast, radiation thermometers based on the multicolor method obtain the temperature from the ratio of the radiant energy of two or more wavelengths, so that the emissivity term is canceled and the temperature of the member to be measured whose emissivity is unknown is also measured. There are advantages you can do.

  By the way, when using a radiation thermometer, it is necessary to obtain the relationship between the measurement value of the standard thermometer and the measurement value of the radiation thermometer in advance and to determine the deviation of the radiation thermometer, that is, to perform calibration. is there. This calibration method is defined in “Appendix 1 (Regulation) Calibration Method” in “General Rules for Performance Tests of Radiation Thermometers” (see Non-Patent Document 1). According to this rule, the calibration of the radiation thermometer is measured by the radiation thermometer that is trying to calibrate the temperature of the black body cavity and the thermometer used as a standard (i.e., the standard thermometer), and the mutual readings are compared. Will be done. Black body furnaces for calibration are classified into standard black body furnaces and comparative black body furnaces, but the former is a low and medium temperature black body furnace that uses a glass thermometer or platinum resistance thermometer as the standard thermometer. The latter, which uses a radiation thermometer as the standard thermometer, is used for medium, high, and ultra-high temperature ranges exceeding 500 ° C.

  FIGS. 16 to 18 are calibration methods described in “4. Calibration method” in Appendix 1 above, and each of the three calibration methods in the case where the comparative black body furnace is used are at medium and high temperatures or more. It is a figure explaining. In the calibration method shown in FIG. 16, the radiation thermometer 100 and the standard thermometer 102 to be calibrated are arranged on the same optical axis. The radiation thermometer 100 is retractable up and down or left and right. When the radiation thermometer 100 is at a measurement position indicated by a solid line in the figure, the temperature is measured by the radiation thermometer 100 and when it is at a retraction position indicated by a one-dot chain line. A standard thermometer 102 measures the temperature. That is, calibration is performed by measuring the same position in the black body furnace 104 with the standard thermometer 102 and the radiation thermometer 100 and alternately measuring in a state where the temperature of the black body furnace 104 is stable.

Further, in the calibration method shown in FIG. 17, the radiation thermometer 100 and the standard thermometer 102 are arranged slightly inclined with respect to the black body furnace 104 in different directions. Therefore, calibration is performed at the temperature measured simultaneously by the radiation thermometer 100 and the standard thermometer 102. Further, in the calibration method shown in FIG. 18, the radiation thermometer 100 and the standard thermometer 102 are arranged opposite to each other with the black body furnace 106 configured symmetrically in the front and rear, and calibration is performed at the temperature measured at the same time. Done.
JP 2004-045268 A Japanese Industrial Standard JIS C 1612: 2000

  In order to obtain high accuracy by the calibration method shown in FIGS. 16 to 18, the temperature in the blackbody cavity of the blackbody furnaces 104 and 106 is constant and stable over the entire bottom surface (that is, It is necessary that the temperature does not change with time. However, since the black body furnace has a constant distribution of the bottom surface temperature and cannot completely eliminate temporal changes (hereinafter referred to as temporal temperature fluctuations), this prevents high calibration accuracy from being obtained. It was. In the currently available blackbody furnace, for example, at a temperature of 1000 (° C.) or higher, the guaranteed value of accuracy of about 1 (° C.) is the limit. For this reason, it has been desired that the radiation thermometer can be calibrated with a high accuracy of, for example, a repeatability of 0.1 (° C.) or higher even in such a high temperature range. For example, in a two-color temperature measurement device that can measure temperature independent of the physical properties of the object, high-accuracy thermal image measurement with the same or better luminance temperature method used in conventional thermography, for example, with a repeatability of 0.1 (° C) or more However, since there is no calibration method, the repeatability is only about 1 (° C.) and the request is not met.

  The present invention has been made in the background of the above circumstances, and its purpose is to provide a calibration method and a calibration apparatus capable of obtaining a high calibration accuracy of a radiation thermometer even at a high temperature of 1000 (° C.) or higher. It is to provide.

  In order to achieve such an object, the gist of the first invention is a standard thermometer and a radiant thermometer to calibrate the radiant energy radiated from the black body furnace while changing the temperature of the black body furnace. A method of calibrating the radiation thermometer by measuring each of the measured values based on the mutual measurement, wherein (a) light in a predetermined measurement wavelength region is radiated from the black body furnace. Is divided into two at a predetermined ratio between the first split light toward the standard thermometer and the second split light toward the radiation thermometer, and the focal points of the standard thermometer and the radiation thermometer with the same incident angle. (B) a measurement value pair for sequentially storing a pair of a measurement value of the standard thermometer and a measurement value of the radiation thermometer, which are simultaneously measured; Including a memory step There is.

  Further, the gist of the second invention is to measure the radiation energy radiated from the black body furnace while changing the temperature of the black body furnace with a standard thermometer and a radiation thermometer to be calibrated. A calibration device for calibrating the radiation thermometer on the basis of the correlation between the measured values, wherein (a) light in a predetermined measurement wavelength region is radiated from the black body furnace. A first split light directed to the standard thermometer with a predetermined incident angle with respect to the focal plane; a second split light directed to the radiation thermometer with the same incident angle as the first split light with respect to the focal plane; In addition, a light dividing device for dividing into two at a predetermined ratio is included.

  According to the first aspect of the invention, in the measurement step, the first split light and the second split light divided into two at a constant ratio are respectively incident on the focal planes of the standard thermometer and the radiation thermometer, and the respective radiation intensities. Are measured, a measured value pair storing step stores each measured value (ie, radiation intensity) pair measured simultaneously. Therefore, the light on one optical axis is divided and made incident on the standard thermometer and the radiation thermometer at the same incident angle, so errors due to different bottom surfaces of the black body furnace to be identified are preferably eliminated. In addition, since the measurement is performed simultaneously with the standard thermometer and the radiation thermometer, the influence of temporal fluctuation is preferably eliminated. Therefore, by calibrating based on the stored measurement value pairs, the temperature guarantee value of the black body furnace does not affect the calibration accuracy, so the radiation thermometer has a high calibration accuracy even at a high temperature of 1000 ° C or higher. Can be obtained.

  In addition, according to the present invention, since the influence of temporal fluctuation is eliminated as described above, it is not necessary that the temperature of the blackbody furnace is stable during calibration. This eliminates the waiting time until the temperature has been stabilized, which has been essential in the past, and enables quick calibration, as well as continuous calibration while raising the temperature. There is an advantage that makes it possible.

  According to the second aspect of the invention, the light splitting device causes the light emitted from the black body furnace to be incident on the first split light and the second split light that are incident on the standard thermometer and the radiation thermometer at the same incident angle, respectively. Since it is divided into two at a constant rate, the calibration method of the first invention can be suitably implemented. Therefore, a calibration device capable of obtaining high calibration accuracy of the radiation thermometer even at a high temperature of 1000 (° C.) or higher can be obtained.

  If the first split light and the second split light are those that divide the radiant energy of the black body furnace into two at a constant ratio in the measurement wavelength range of the standard thermometer and the radiation thermometer, the split ratio is It is not limited to 1: 1 and can be determined as appropriate. In particular, in a two-color radiation thermometer, only the intensity ratio of the two wavelengths to be measured becomes a problem. Therefore, if the first split light has a radiation intensity enough to obtain sufficient sensitivity, it will hinder calibration. There is no. Moreover, the division | segmentation ratio about wavelength ranges other than the said measurement wavelength range is arbitrary. That is, the light in the wavelength region that does not affect the measurement may be divided at any ratio.

  Here, the calibration method according to the first aspect of the present invention is preferably configured such that (c) a relative intensity of radiation at a plurality of predetermined adjacent points on one focal plane of the standard thermometer and the radiation thermometer. (D) each of the standard thermometer and the radiation thermometer so as to cancel the change in accordance with the change with time of the relative relationship. A moving step of moving the focal plane in the same direction and in the same direction in the same direction within a plane parallel to each other. In this way, in the relative relationship calculation step, the relative relationship between the radiation intensities adjacent to each other on the focal plane is calculated at predetermined time intervals, and in the movement step, the relative relationship changes over time. Accordingly, the focal planes of the standard thermometer and the radiation thermometer are displaced along the surface in the same direction by the same distance so as to cancel the change. Therefore, even if a spatial temperature fluctuation caused by the radiant energy of the blackbody furnace occurs, the change is canceled out by the displacement of the focal plane, so that higher calibration accuracy can be obtained. In other words, when the spatial temperature fluctuation occurs, the relative relationship of the radiation intensity at the calibration points adjacent to each other can change, so that the change can be canceled by moving the focal plane according to the amount of change. is there.

  The calibration apparatus according to the second aspect of the invention is preferably such that (b) a relative relationship between radiation intensities at predetermined points adjacent to each other on one focal plane of the standard thermometer and the radiation thermometer. (C) one of the standard thermometer and the radiation thermometer for canceling the change in accordance with the change with time of the relative relationship. A moving amount calculating means for calculating a moving direction and a moving distance of the focal plane in a plane parallel to the focal plane; and (d) the calculated movement of each focal plane of the standard thermometer and the radiation thermometer. And a synchronous movement device for synchronously moving the same position in the same direction by the same distance in a plane parallel to each other. In this way, the relative relationship calculation means calculates the relative relationship between the radiation intensities adjacent to each other on the focal plane at a predetermined time interval, and the movement amount calculation means changes the relative relationship over time. Therefore, if the focal planes of the standard thermometer and the radiation thermometer are moved by the amount of movement calculated by the synchronous moving device, the spatial temperature fluctuation is preferably canceled out. Therefore, higher calibration accuracy can be obtained.

  In the above aspect, “adjacent multiple points” is not limited to those that are strictly adjacent, but includes those that are located in the vicinity of an arbitrary calibration point. That is, the range for monitoring the change in the relative relationship may be appropriately determined according to the desired calibration accuracy. The “predetermined time” is appropriately determined according to the guaranteed value of the accuracy of the black body furnace and the desired calibration accuracy. The term “according to changes over time” does not necessarily mean that the movement amount is always calculated and moved when a change in relative relationship over time is recognized, but the calibration accuracy to be obtained If the change is small enough to be ignored, it means that the movement is not performed, that is, the movement amount is not calculated, the movement amount is zero, or the movement is not performed.

  Further, the moving step and the moving device are sufficient if the focal plane is moved relative to the optical axis. That is, the focal plane (or radiation thermometer and standard thermometer) may be moved, or the blackbody furnace may be moved.

  Preferably, the light is divided by a half mirror. In other words, the light splitting device is a half mirror provided at an angle of 45 degrees with respect to the optical axis between the black body furnace and the standard thermometer or the radiation thermometer. If it does in this way, the radiant energy radiated | emitted from the blackbody furnace will be reflected or permeate | transmitted and will reach | attain a radiation thermometer with the 1st division | segmentation light which permeate | transmits or reflects a half mirror, and arrives at a standard thermometer. The second split light is divided into approximately two equal parts over substantially the entire wavelength range. In the present invention, even if the light transmitted through the half mirror is configured to enter the standard thermometer, the light reflected thereby is configured to enter the standard thermometer. There is no problem.

  Preferably, the light splitting device includes the half mirror and a total reflection mirror for reflecting the light reflected thereby in a direction parallel to the transmitted light. In this way, since the first split light and the second split light become parallel light, the standard thermometer and the radiation thermometer can be installed side by side. Therefore, for example, if they are fixed on a common moving table, the focal planes can be synchronously moved in the same direction by the same distance by displacing the moving table by the moving amount. it can. That is, there is an advantage that the configuration and control of the moving device are simplified as compared with the case where the first split light and the second split light are not parallel lights.

  Preferably, the first split light and the second split light are incident perpendicularly to the focal planes of the standard thermometer and the radiation thermometer. The incident angles of the first split light and the second split light on the focal plane can be set to an appropriate angle as long as they are the same angle. This reduces the influence of the lens periphery dimming and the bandpass filter wavelength (center) shift.

  Preferably, the radiation thermometer is a multicolor radiation thermometer. Although the present invention can be applied to the calibration of various types of radiation thermometers, the multicolor radiation thermometer measures the temperature based on the ratio of the radiation intensities of mutually different wavelengths. The advantage that temperature measurement at high temperature is possible without being influenced by emissivity is utilized, and the temperature of various symmetrical objects can be measured with high accuracy.

  Hereinafter, an embodiment of the present invention will be described in detail with reference to the drawings. In the following embodiments, the drawings are appropriately simplified or modified, and the dimensional ratios, shapes, and the like of the respective parts are not necessarily drawn accurately.

  FIG. 1 is a diagram illustrating the overall configuration of a radiation thermometer calibration apparatus 10 according to an embodiment of the present invention. In FIG. 1, a blackbody furnace 12 is configured in the same manner as the blackbody furnace 106, has a substantially cylindrical shape, and is viewed from both sides in the longitudinal direction, that is, in the horizontal position in FIG. Possible bottom surface not shown. The blackbody furnace 12 is made of, for example, carbon as a whole and is provided in an inert gas atmosphere such as vacuum or argon. For example, a radiation thermometer such as a two-color thermometer (not shown) is used from the right end side. By measuring the temperature and performing feedback control, the temperature is controlled with an error of about ± 1 (° C.), for example.

  A precision movable stage 14 is provided on the left end side of the black body furnace 12, and a two-color camera, that is, a radiation thermometer 16, which is a calibration target, is fixed on the front position of the black body furnace 12. . Further, a half mirror 20 that forms an angle of 45 degrees with respect to the optical axis 18 is provided on the optical axis 18 from the black body furnace 12 toward the two-color camera 16, and is emitted from the black body furnace 12. The light is divided into two equal parts by the half mirror 20 into a first divided optical path 18a and a second divided optical path 18b perpendicular thereto. The transmitted light of the first divided optical path 18a is incident on the two-color camera 16 via the optical system 22 including a lens, a filter, and the like. On the other hand, the reflected light of the second divided optical path 18b is made incident on the standard radiation thermometer 26 via the optical system 24 similarly formed of a lens, a filter and the like. The standard radiation thermometer 26 has a guaranteed value of about 0.4 (° C.), for example. In the present embodiment, the half mirror 20 corresponds to a light splitting device. Note that the two-color camera 16 is a calibration target as described above and does not constitute the calibration device 10. Instead, a desired radiation thermometer to be calibrated is fixed at a position where the two-color camera 16 is fixed. In the present embodiment, as will be described later, the wavelength range of light incident on the two-color camera 16 corresponds to the measurement wavelength range, and the light emitted from the blackbody furnace 12 extends over substantially the entire wavelength range. Divided into two equal parts.

  The two-color camera 16 and the standard radiation thermometer 26 include focal plane detectors 28 and 30 for receiving radiant energy, respectively. The detector 28 is, for example, a CCD element including a light detection surface 50 (see FIG. 2) on which a large number of light detection elements are arranged. The detector 30 is made of, for example, a silicon photodiode. The detector 30 having the same sensitivity range as the detector 28 is selected. The incident angle of the incident light to the detectors 28 and 30 is perpendicular to the focal plane of both the two-color camera 16 and the standard radiation thermometer 26. Light incident on the two-color camera 16 and the standard radiation thermometer 26 is converted into an electrical signal, and the signal is sent to the control device 32 to perform various processes described later. The control device 32 is a so-called microcomputer having, for example, a CPU, a RAM, a ROM, an input / output interface, and the like. The CPU processes input signals in accordance with a program stored in the ROM in advance, thereby Perform calibration.

  FIG. 2 is a diagram for explaining an outline of an example of the configuration of the two-color camera 16 described above. The two-color camera 18 is used in, for example, a two-color temperature distribution measuring device 34, and emits light emitted from the surface of a member to be measured 36 heated in a furnace such as a firing furnace or a heating furnace. Are divided into a first optical path 40 and a second optical path 42 by a half mirror (beam splitter) 38. The first optical path 40 and the second optical path 42 are bent substantially at right angles by mirrors 44 and 46, and then combined by a half mirror 48. The focal plane detector, that is, the CCD element 28, and the light detection surface 50 have a member to be measured. It is made to enter an image detector 54 having a lens device 52 for forming 36 images.

The first optical path 40 and the second optical path 42 include a first filter 56 that transmits light having a first wavelength (band) λ _{1 having} a center wavelength of 600 (nm) and a half width of 10 (nm), for example. For example, second filters 58 that pass light having a second wavelength (band) λ _{2 having} a center wavelength of 650 (nm) and a half-value width of 10 (nm) are inserted. The first filter 56 and the second filter 58 are so-called interference filters that allow light in a predetermined wavelength band to pass through light wave interference.

The first wavelength λ ₁ and the first wavelength λ ₂ are determined as follows, for example. First, the relationship between the wavelength of the black body and the radiation (radiation) intensity at the lowest temperature in the measurement temperature range, that is, the curve L1 shown in FIG. 3, is obtained by the Planck equation, and then the background from the member to be measured 36 at room temperature. The radiant intensity E _BG is measured. Next, an arbitrary one point on the curve L1 exceeding the triple value of the background radiation intensity E _BG , that is, 3 × E _BG is determined as the first wavelength λ ₁ . This is because the measurement accuracy is increased by using an intensity greater than the detection error. Next, if the first wavelength λ ₁ is 600 (nm) by a wavelength Δλ equal to or less than 1/12 of the first wavelength λ ₁ , then 50 (nm) (= Δλ) above the first wavelength λ ₁ or A wavelength shifted downward, for example, 650 (nm) is determined as the second wavelength λ ₂ . This is to establish an approximate expression (Expression 1) showing the principle of the two-color thermometer described later. It should be noted that the first wavelength λ ₁ and the second wavelength λ ₂ are provided with a difference of at least twice the half-value width determined below so that the mutual wavelengths do not overlap in order to maintain the measurement accuracy of the radiation intensity. To. The first wavelength λ ₁ and the second wavelength λ ₂ have a half width of 1/20 or less, for example, about 20 (nm) or less of the center wavelength in order to maintain the properties of monochromatic light. The first filter 56 and the second filter 58 are configured such that the difference in transmittance is within 30%. When the difference in transmittance is greater than 30%, the sensitivity is lowered at the lower wavelength side, the S / N ratio is lowered, and the display temperature accuracy is lowered.

In the optical system of FIG. 2, for example, the first optical path 40 and the second optical path 42 are slightly shifted between the half mirror 48 and the image detector 54 by the mirrors 44 and 46, so that the light from the CCD element 28 can be obtained. Two images with different wavelengths are formed on the detection surface 50. That is, in the image detector 54, for example, as shown in FIG. 4, the member to be measured 36 having the first wavelength λ ₁ selected by the first filter 56 from the light emitted from the surface of the member to be measured 36. The first wavelength G ₁ is formed at the first position B ₁ on the light detection surface 50, and the second wavelength λ selected by the second filter 58 from the light emitted from the surface of the member to be measured 36. second image G ₂ of ₂ of the measured member 36 is adapted to be brought imaged on different second position B ₂ and the first position B ₁ on the photodetection surface 50. Thereby, the radiation intensity of each part of the first image G ₁ and the radiation intensity of each part of the second image G ₂ are detected in element units, that is, pixel units, by a large number of light detection elements arranged on the light detection surface 50. It has come to be. Signals output from these light detection elements are sent to the arithmetic and control unit 60. The arithmetic control device 60 is a microcomputer similar to the control device 32, and the CPU receives input signals according to a program stored in the ROM in advance, that is, from a large number of light detection elements arranged on the light detection surface 50. The signal is processed, and the image display 62 displays the surface temperature distribution of the member to be measured 36.

FIG. 5 is a flowchart for explaining a main part of the arithmetic control operation of the arithmetic control device 60. In step (hereinafter, step is omitted) S1, the radiation intensity E _1ij of each part of the first image G ₁ and the second image G ₂ are detected by signals from a large number of light detection elements arranged on the light detection surface 50. The radiation intensity E _{2ij of} each part is read in element units, that is, pixel units. Next, in S2, the position is located at the same part of the first image G ₁ imaged at the first position B ₁ and the second image G ₂ imaged at the second position B ₂ in the light detection surface 50. light detecting element pairs radiant intensity ratio R _ij of the first wavelength lambda ₁ of the radiation intensity E _1ij a second wavelength lambda ₂ of the radiation intensity E _2ij which detect (= E _1ij / E _2ij) is calculated.

Next, in S3, the temperature T _{ij for} each pixel constituting the image of the member to be measured 36 based on the actual radiation intensity ratio R _ij calculated for each pixel based on the relationship stored in advance in the arithmetic and control unit 60. Is derived. The relationship used for deriving the temperature T _ij is obtained from an approximate expression showing the measurement principle of the two-color thermometer shown in Expression 1, for example. Equation 1 is derived so that the surface temperature T of the member to be measured 36 can be obtained from the radiation intensity ratio R at _two different wavelengths λ ₁ and λ ₂ without using the emissivity. In the following equations, λ ₂ > λ ₁ , T is the absolute temperature, C ₁ is the _first radiant (Planck) constant, and C ₂ is the _second radiant (Planck) constant.

(Formula 1)
R = (λ ₂ / λ ₁ ) ⁵ exp [(C ₂ / T) · (1 / λ ₂ −1 / λ ₁ )]

The above equation 1 is obtained as follows. That is, it is known that the radiation intensity (energy) Eb and λ radiated from the black body per unit time and unit area at the wavelength λ follows Formula 2 which is a Planck formula. Further, when exp (C ₂ / λT) >> 1, it is known that Formula 3 which is an approximate formula of Wien holds. Since it can be considered that a normal object is gray, Equation 4 is derived by rewriting by substituting emissivity ε. When the ratio R of the radiant intensities E ₁ and E ₂ of the two wavelengths λ ₁ and λ ₂ is obtained using this equation 4, equation 5 is derived. When the two wavelengths λ ₁ and λ ₂ are close to each other, the dependence of the emissivity ε can be ignored, and can be approximated as ε ₁ = ε ₂ , so that the above Equation 1 is obtained. According to this, even if the object has a different emissivity ε, the temperature T can be obtained without being affected by it.

(Formula 2)
Eb = C ₁ / λ ⁵ [exp (C ₂ / λT) −1]
(Formula 3)
Eb = C ₁ exp (−C ₂ / λT) / λ ⁵
(Formula 4)
E = ε · C ₁ exp (−C ₂ / λT) / λ ⁵
(Formula 5)
R = (ε ₁ / ε ₂ ) · (λ ₂ / λ ₁ ) ⁵ exp [(C ₂ / T) · (1 / λ ₂ −1 / λ ₁ )]

As described above, when the temperature T _ij for each pixel constituting the image of the member to be measured 36 is calculated, the actual value calculated for each pixel from the relationship stored in advance in the arithmetic control device 60 in S4. Based on the temperature T _ij , the temperature distribution on the surface of the member to be measured 36 is displayed. For example, the temperature distribution on the surface of the member to be measured 36 is displayed in a predetermined temperature color.

  In the two-color camera 16 configured and used as described above, in order to measure temperature with high accuracy, it is necessary to perform calibration using the calibration device 10 in advance. FIG. 6 is a flowchart for explaining a main part of the control operation of the control device 32. When performing the calibration, the two-color camera 16 is fixed to the calibration device 10 as shown in FIG. 1 and the temperature of the black body furnace 12 is set to a temperature range to be measured using the two-color camera 16. Control. For example, the temperature of the black body furnace 12 is raised to the lowest temperature in the temperature range and held. After the temperature of the blackbody furnace 12 is stabilized, for example, calibration is started while gradually increasing the temperature at an appropriate temperature increase rate.

First, in step KS1, a two-wavelength radiation intensity ratio R measured by the two-color camera 16 is calculated for each pixel at predetermined time intervals. In step KS1, the radiation intensity ratio R is calculated by executing the same processing as in steps S1 and S2 of FIG. Next, in step KS2, the temperature (ie, standard radiation thermometer output temperature) T _std measured simultaneously with the two-color camera 16 by the standard radiation thermometer 26 is read. In this embodiment, these steps KS1 and KS2 correspond to the measurement process.

Next, in step KS3, a pair of the radiation intensity ratio R and the standard radiation thermometer output temperature _Tstd is stored. Since the light incident on the two-color camera 16 and the standard radiation thermometer 26 is light divided into two by the half mirror 20 as described above, the radiation intensity ratio R and the standard radiation thermometer output temperature T _std are Those acquired at the same time are paired. In the present embodiment, this step KS3 corresponds to a measured value pair storing step.

Each of the above steps KS1 to KS3 is repeatedly performed, for example, in the temperature rising process of the blackbody furnace 12. Thereby, many pairs of radiation intensity ratio R and standard radiation thermometer output temperature _Tstd are obtained, and are memorize | stored sequentially. However, each of the above steps may be performed at each temperature while intermittently increasing the temperature of the blackbody furnace 12 over a desired temperature range. Further, each pair of data is temporarily stored and may be discarded immediately after being output on an XY chart for creating a calibration curve as described later.

  FIG. 7 shows the change in the output value of the two-color camera 16, that is, the calibration camera thus obtained (that is, the radiant intensity ratio R), and the change in the output temperature of the standard radiation thermometer 26, that is, the reference black body furnace temperature. Time (seconds) is represented on the horizontal axis. As is clear when the calibration camera output value and the reference black body furnace temperature are compared at the same time, their changing tendency is substantially the same. That is, the radiation intensity ratio R changes immediately following the change in the reference blackbody furnace temperature. FIG. 7 includes the measured values before the temperature of the black body furnace 12 is stabilized, and the temperature of the black body furnace 12 has reached a steady state when 60 seconds have elapsed after the start of measurement. Even in this steady state, there is a temperature change of about ± 1 (° C.) as described above, and the temperature is not kept completely constant.

Returning to FIG. 6, when a preset measurement time elapses or the measurement is completed over the entire measurement temperature range, in step KS4, a calibration curve is connected to an image output device (not shown) such as a monitor or a printer. Is output. That is, a pair of the stored radiation intensity ratio R and standard radiation thermometer output temperature T _std is X− with the two-color thermometer output wavelength intensity ratio on the horizontal axis and the standard radiation thermometer output temperature on the vertical axis. The linear regression line obtained from the many data points is displayed on the Y chart. Note that the output of the data points may be performed sequentially. An example of an output figure in which data points are represented by black circles and primary regression lines are represented by thin lines is shown in FIG. In the illustrated example, the equation of the obtained straight line Y is (Equation 6) below, and the dispersion R is 0.99035. Further, FIG. 9 shows the difference distribution from the linear regression line (model function). As shown in FIGS. 8 and 9, according to the present embodiment, the variation of the calibration data is extremely small, and a repeatability of about 0.3 (° C.) is obtained. This repeatability corresponds to the theoretical limit value of hardware depending on the data depth of the two-color camera 16 used.

(Formula 6)
Y = -8.2756 + 806.8X R = 0.99035

  The data in FIGS. 7 to 9 represent the results of calibration for a temperature range of about 970 to 980 (° C.). The reason why the effect of reducing the variation in this embodiment is obtained is that As shown in FIG. 1, it is based on the fact that a pair of intensity ratio and temperature measured at the same time is obtained by dividing light by the half mirror 20. Therefore, according to the calibration device 10, excellent repeatability can be obtained over the entire temperature range including the temperature of 1000 (° C.) or higher that can be measured by the two-color camera 16 without being limited to the above temperature range.

In short, according to the present embodiment, in steps KS1 and KS2 corresponding to the measurement process, the first split light 18b and the second split light 18a divided by the half mirror 20 are converted into the standard radiation thermometer 26 and the two-color camera, respectively. When the radiation intensity is measured by being incident on the 16 focal planes, that is, the light detection surface 50 and the like, in step KS3 corresponding to the measured value vs. storage step, each measured value (that is, the radiation intensity ratio) measured simultaneously. A pair of R and the standard radiation thermometer output temperature T _std ) is stored. Therefore, since the light on one optical axis 18 is divided and made to enter perpendicularly to the standard radiation thermometer 26 and the two-color camera 16, there is an error caused by the difference in the bottom surface of the black body furnace 12 to be identified. In addition to being preferably eliminated, the influence of temporal fluctuation is preferably eliminated because the measurement is performed simultaneously with the standard radiation thermometer 26 and the two-color camera 16. Therefore, since the temperature guarantee value of the black body furnace 12 does not affect the calibration accuracy by calibrating based on the stored measurement value pair, the two-color camera 16 is highly calibrated even at a high temperature of 1000 (° C.) or higher. Accuracy can be obtained.

  Next, another embodiment of the present invention will be described. In the following embodiments, portions common to the above-described embodiments are denoted by the same reference numerals, and description thereof is omitted.

  In the radiation thermometer calibration device 64 shown in FIG. 10, the standard radiation thermometer 26 is fixed on the precision movable stage 14 in addition to the two-color camera 16. A mirror (total reflection mirror) 66 is provided in the path of the second split light 18b reflected by the half mirror 20, and reflects the incident light at a right angle so that it is parallel to the first split light 18a and is a standard radiation. The direction of travel toward the thermometer 26 is changed. That is, in this embodiment, the light incident on the two-color camera 16 and the standard radiation thermometer 26 is parallel to each other.

  Further, as shown in FIG. 10 and FIG. 11 shown in a front view thereof, the precision movable stage 14 has two directions perpendicular to the optical axis 18 and perpendicular to each other, that is, up and down in FIG. An X-direction drive device 68 and a Y-direction drive device 70 are provided for driving this along the vertical direction in FIG. These drive devices 68 and 70 can both control the movement amount with submicron accuracy. The control device 32 is based on, for example, a change with time of the temperature measured by the standard radiation thermometer 26, and when the change shows an abnormal value, that is, the focal plane detector 30 has a constant lattice pattern as shown in FIG. In the case where a large number of calibration points 72 are provided with a center interval P, when the temperatures detected by the calibration points 72 adjacent to each other are suddenly reversed, a temperature change due to a spatial fluctuation is not an actual temperature change. If it is determined that it has occurred, the driving devices 68 and 70 are driven so as to cancel them, and the photodetection surface 50 and the like are displaced in a plane parallel to the driving devices. The center interval P is an appropriate value corresponding to the calibration accuracy and measurement accuracy required for the two-color camera 16.

FIG. 13 is a flowchart for explaining a main part of the control operation of the control device 32. In step IS1 corresponding to the relative relationship calculation step, the relative relationship between the numerous calibration points 72 is repeatedly calculated at regular time intervals, and changes in the relative relationship are monitored. If a sudden change in the temperature difference between adjacent ones, for example, a reversal of the temperature, is recognized, it is determined that there has been a temperature change due to spatial fluctuations, and the process proceeds to step IS2. In step IS2 corresponding to the movement amount calculating step, based on the temperature change of each of the many calibration points 72 when it is determined that there is a spatial fluctuation, the light detection surface 50 (in this case, the focus point) is canceled. The relative movement amount in the direction perpendicular to the optical axis 18 with respect to the black body furnace 12 is calculated. For example, m, when the n and the coordinates of the calibration point 72, at time _{t 1 T (m, n)} > T (m-1, n), T (m, n)> T (m + 1, n), The relationship between T _{(m, n)} > T _{(m, n-1)} and T _{(m, n)} > T _{(m, n + 1)} is T _{(m, n)} < T _{(m-1, n)} , T _{(m, n)} > T _{(m + 1, n)} , T _{(m, n)} > T _{(m, n-1)} , T _{(m, n)} > T _{( m, n + 1)} , it is determined that the position is displaced by one calibration point in the negative direction of the X axis, and the precision moving stage 14 is moved by one calibration point in the negative direction of the X axis. The amount of movement is calculated. Note that step IS2 is always performed at regular intervals, and for example, a movement amount of 0 may be calculated while no spatial fluctuation is detected.

  Incidentally, the temperature of the bottom of the black body cavity of the black body furnace 12 shows a distribution as shown in FIG. 14, for example. In FIG. 14, it can be said that although the temperature is low at the peripheral portion, it is substantially constant within a diameter range of about 10 mm at the central portion. However, when this is expanded with respect to the temperature axis, even in a range that appears to be substantially constant, as shown in FIG. 15, the temperature still tends to increase toward the center with a fluctuation range of about 1 (° C.). I understand that.

  Therefore, if there is such spatial fluctuation as described above, the detection value of one element of the focal plane detector 30 is replaced with the detection value of another element that is adjacent or located in the vicinity. Correspondingly, a maximum temperature change of about 1 (° C.) can occur.

  However, in the present embodiment, when the spatial fluctuation as described above is detected, the movement amount for canceling this is calculated as described above, and then in step IS3 corresponding to the synchronous movement process, the calculated amount is calculated. The X direction driving device 68 and the Y direction driving device 70 are driven according to the amount of movement. As a result, the precision movable stage 14 is displaced along the X-axis and also along the Y-axis, so that the two-color camera 16 and the standard radiation thermometer 26 fixed thereto are moved to the optical axis 18. It is displaced in a vertical plane. That is, the detection planes of the focal plane detectors 28 and 30 are displaced in a plane parallel to the focal plane detectors 28 and 30, and the spatial fluctuation is corrected. The amount of movement can be calculated based on the radiation intensity detected by the standard radiation thermometer 26 instead of the temperature, and the radiation detected by the two-color camera 16 instead of the standard radiation thermometer 26. Intensity may be used.

  Therefore, according to the present embodiment, in step IS1, the relative relationships of the temperatures or radiant intensities of a large number of calibration points 72 are calculated at regular intervals, and if an abnormality occurs in the relative relationship, step IS2 The standard radiation thermometer 26 and the two-color camera 16 are displaced by the same distance in the same direction so as to cancel the change in accordance with the change in the relative relationship with time. Therefore, even if a spatial temperature fluctuation caused by the radiant energy of the blackbody furnace 12 occurs, the change is canceled out by displacing the calibration point 72, so that higher calibration accuracy can be obtained.

  As mentioned above, although this invention was demonstrated in detail with reference to drawings, this invention can be implemented also in another aspect, A various change can be added in the range which does not deviate from the main point.

It is a schematic diagram explaining the principal part of a structure of the calibration apparatus of one Example of this invention. It is a figure explaining the structure of the temperature distribution measuring apparatus calibrated by the calibration apparatus of FIG. It is a figure explaining the method of determining the wavelength of the 1st filter of FIG. 2, and the wavelength of a 2nd filter. It is a figure explaining the 1st image and 2nd image which were imaged on the light detection surface of the image detection apparatus of FIG. 3 is a flowchart for explaining a main part of a control operation of the temperature measurement arithmetic and control unit of FIG. 2. It is a flowchart explaining the principal part of control operation of the calculation control apparatus for calibration of FIG. It is a figure which shows the time change of the output value of the radiation thermometer to be calibrated measured with the calibration apparatus shown in FIG. 1, and the black body furnace temperature measured by the standard thermometer. It is a figure which shows the relationship between the output wavelength intensity ratio of the two-color thermometer obtained by the calibration apparatus shown in FIG. 1, and the output temperature of a standard radiation thermometer. It is a histogram showing the difference from the linear regression line shown by FIG. It is a schematic diagram explaining the principal part of a structure of the calibration apparatus of the other Example of this invention. It is a figure which shows the calibration apparatus shown by FIG. 10 by a front view. It is a figure explaining the calibration point provided on the focal plane detector of the calibration apparatus of FIG. It is a flowchart explaining the principal part of the control action of the calculation control apparatus for calibration of FIG. It is a figure explaining the temperature distribution of a blackbody furnace. It is a figure explaining the space fluctuation of a black body furnace by extracting the substantially center part in the X direction of FIG. 12, expanding a temperature scale. It is a figure for demonstrating the one aspect | mode of the conventional calibration method prescribed | regulated to JIS. It is a figure for demonstrating the other aspect of the conventional calibration method prescribed | regulated to JIS. It is a figure for demonstrating the further another aspect of the conventional calibration method prescribed | regulated to JIS.

Explanation of symbols

10: Radiation thermometer calibration device, 12: Blackbody furnace, 14: Precision movable stage, 16: Two-color camera, 18: Optical axis, 20: Half mirror, 26: Standard radiation thermometer, 28, 30: Focal plane detection , 32: Control device

Claims (4)

By measuring the radiant energy radiated from the black body furnace with the standard thermometer and the radiation thermometer to be calibrated, while changing the temperature of the black body furnace, the radiation based on the correlation between these measurements. A method for calibrating a thermometer, comprising:
Predetermined predetermined ratio of light in a predetermined measurement wavelength range in the radiant energy radiated from the black body furnace to a first divided light traveling toward the standard thermometer and a second divided light traveling toward the radiation thermometer A measurement step of measuring the intensity of each radiation by being incident on the focal planes of the standard thermometer and the radiation thermometer with the same incident angle.
A method for calibrating a radiation thermometer, comprising: a measurement value pair storage step for sequentially storing a pair of a measurement value of the standard thermometer and a measurement value of the radiation thermometer measured simultaneously. A relative relationship calculating step of calculating a relative relationship of radiation intensity at a plurality of predetermined adjacent points on one focal plane of the standard thermometer and the radiation thermometer at predetermined time intervals;
The focal planes of the standard thermometer and the radiation thermometer are set in the same direction in the same direction with respect to the current position in a plane parallel to the standard thermometer and the radiation thermometer so as to cancel the change according to the change of the relative relationship with time. The method for calibrating a radiation thermometer according to claim 1, further comprising: a moving step of moving in synchronization. By measuring the radiant energy radiated from the black body furnace with the standard thermometer and the radiation thermometer to be calibrated, while changing the temperature of the black body furnace, the radiation based on the correlation between these measurements. A calibration device for calibrating a thermometer,
Of the radiant energy radiated from the black body furnace, the light having a predetermined measurement wavelength range is divided into a first split light directed to the standard thermometer with a predetermined incident angle with respect to a focal plane thereof, and the radiation thermometer A radiation temperature characterized by including a light splitting device for dividing the light into the second split light having the same incident angle as that of the first split light with respect to the focal plane at a predetermined ratio. Meter calibration device. A relative relationship calculating means for calculating a relative relationship of radiation intensity at a plurality of predetermined adjacent points on one focal plane of the standard thermometer and the radiation thermometer at predetermined time intervals; ,
A movement for calculating a moving direction and a moving distance in a plane parallel to the focal plane of one of the standard thermometer and the radiation thermometer for canceling the change in accordance with a change in the relative relationship with time. A quantity calculating means;
A synchronous movement device for moving the focal plane of each of the standard thermometer and the radiation thermometer in the same direction and in the same direction in the same direction within a plane parallel to the calculated movement amount. The radiation thermometer calibration apparatus according to claim 3, comprising:

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