JP2005003437A - Radiation thermometer - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To perform high-accuracy radiation temperature measurement with excellent stability and responsiveness by reducing fluctuation in indication due to the effect of water vapor in a measurement optical path with respect to a two-color radiation thermometer that is a radiation thermometer for finding the temperature of an object under measurement from a spectral luminance energy ratio between two measurement wavelengths different from each other. <P>SOLUTION: With respect to this two-color radiation thermometer using an In-Ga-As element as an infrared detection element, first and second wavelengths of two measured wavelengths different from each other are set to be 1.1 to 1.3 μm and 1.45 to 1.7 μm, respectively, within a detection wavelength band of the In-Ga-As element. The effect of an absorption band of water vapor in the measurement optical path is thus made slight to reduce the fluctuation in indication. As a result, the effect of the water vapor in the optical path can be removed, making it possible for the two-color thermometer to show a stable indication value even if an optical path length that is measurement distance varies. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

式（１）をウィーンの公式で近似すると式（３）となる。
【数２】

【数３】

ここで、α_１、α_２は係数で、ｃ_２は以下で表される物理定数である。
【数４】

ｃは真空中の光の速度、ｈはプランクの定数、ｋはボルツマンの定数である。
式（３）をＴで微分して、誤差率を調べると、
【数５】

ただし、ｎ_１とｎ_２は以下である。
【数６】

【数７】

光路中の水蒸気の影響で波長λ_１＝１．３５μｍのみ、透過率が２％減衰したときの指示誤差ΔＴは式（５）より、測定対象温度Ｔが５００℃のとき９℃、７００℃のとき１４℃と大きな誤差を発生させる。
【０００５】
この発明はかかる問題点を解決するためのもので、２色放射温度計における測定光路中の水蒸気の影響による指示変動を低減して、安定性、応答性に優れた高精度の放射測温が可能な２色放射温度計を提供することを目的とする。
【０００６】
【課題を解決するための手段】
この発明は、赤外線検出素子にＩｎＧａＡｓ素子を用いた２色放射温度計において、ＩｎＧａＡｓ素子の検出波長域である、０．９〜１．７μｍ間の水蒸気の吸収帯の影響を僅かにする為に、互いに異なる測定波長の第１の波長λ_１を１．１〜１．３μｍ、第２の波長λ_２を１．４５〜１．７μｍとした２色放射温度計である。
【０００７】
【発明の実施の形態】
図１はこの発明の実施の形態を示す構成説明図である。測定対象１からの光を集光する対物レンズ２、集光された光を第１の測定波長の検出素子５１と第２の測定波長の検出素子５２へ分割する波長分割ミラー３、分割された光を第１の測定波長域の１．１〜１．３μｍのみを透過させる第１のフィルター４１と、分割された光を第２の測定波長域の１．４５〜１．７μｍのみを透過させる第２のフィルター４２と、各検出素子からの信号を増幅するアンプ６１，６２、増幅されたアナログ信号をデジタル信号へ変換するアナログ／デジタル信号変換器８と、デジタル信号に基づいて所定の演算方法で、各波長の分光輝度エネルギーの比Ｒ（Ｔ）から、測定対象の温度を演算する演算手段９から構成される。アンプ６１，６２とアナログ／デジタル信号変換器８の間には、幾つかの入力信号を、各々の入力信号に再生できるような方法で一つの出力信号にするマルチプレクサ７が設けられている。
【０００８】
図３は、測定温度５００℃、周囲温度２６℃、相対湿度５０％ＲＨの条件下で、この発明の測定波長と他の測定波長での、光路長（測定距離）に対する指示変動を確認した結果である。この発明の測定波長域である、第１の測定波長を１．１〜１．３μｍ内の１．２μｍ、第２の測定波長を１．４５〜１．７μｍ内の１．５５μｍとした時の指示変動は、光路長を変化させても僅かである。
【０００９】
図１の実施の形態では波長分割ミラーにより２つの波長に分割し，所定の測定波長域のみを透過させる２つのフィルターを用いたが、図のように円板１０に２つのフィルターを装備して回転させる構成としても良い。円板１０はモータ１１により矢印方向に回転する。円板１０には第１の測定波長域の１．１〜１．３μｍのみを透過させる第１のフィルター４１と、分割された光を第２の測定波長域の１．４５〜１．７μｍのみを透過させる第２のフィルター４２が設けられる。一つの検出素子５１からの信号を増幅するアンプ６１、増幅されたアナログ信号をデジタル信号へ変換するアナログ／デジタル信号変換器８と、デジタル信号に基づいて所定の演算方法で、各波長の分光輝度エネルギーの比Ｒ（Ｔ）から、測定対象の温度を演算する演算手段９から構成される。
【００１０】
【発明の効果】
ＩｎＧａＡｓ赤外線検出素子を使用した２色温度計における、互いに異なる測定波長の第１の波長λ_１を１．１〜１．３μｍ、第２の波長λ_２を１．４５〜１．７μｍとしたので、光路中の水蒸気の影響を除去でき、光路長すなわち測定距離が変化した場合でも安定した指示値を示す２色温度計が可能となった。
【図面の簡単な説明】
【図１】この発明の実施の形態を示す構成説明図
【図２】水蒸気の透過率を示す図
【図３】指示変動値の比較グラフ
【図４】この発明の他の実施形態を示す構成説明図
【符号の説明】
１ 測定対象
２ 対物レンズ
３ 波長分割ミラー
４１，４２ フィルター
５１，５２ 検出素子
６１，６２ アンプ
７ マルチプレクサ
８ アナログ／デジタル信号変換器
９ 演算手段
１０ 円板
１１ モータ[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a two-color radiation thermometer using two wavelengths among radiation thermometers that measure the temperature of an object to be measured by applying a radiation temperature measurement technique.
[0002]
[Prior art]
The two-color radiation thermometer is a radiation thermometer that obtains the temperature T to be measured from the ratio R (T) of spectral luminance energy at two different measurement wavelengths. As the detection element, a PbS element, a silicon element, or a photomultiplier tube is used depending on the measurement temperature. As an infrared detecting element of a two-color radiation thermometer in a low and middle temperature range, a PbS element is generally used (for example, “New Temperature Measurement” edited by Society of Instrument and Control Engineers, pages 227 and 228).
[0003]
Also, InGaAs elements that have been developed for communication in recent years are more stable than conventional infrared detection elements, and have excellent characteristics as infrared detection elements for two-color radiation thermometers, with a response that is more than 100 times faster. Yes.
[0004]
[Problems to be solved by the invention]
However, the PbS element has problems of poor stability and slow response speed.
Further, in the detection wavelength range of 0.9 to 1.7 μm of an InGaAs element having excellent stability and response speed, there is a water vapor absorption band as shown in FIG. 2 (for example, “Infrared Engineering”, Modern Science Co., Ltd., page 61). ). Due to the absorption band, a large measurement error occurs depending on the measurement wavelength of the two-color radiation thermometer. In particular, when the measurement distance, that is, the optical path length fluctuates, the measurement error becomes significant. For example, the error when the first measurement wavelength is λ ₁ = 1.35 μm and the second measurement wavelength is λ ₂ = 1.55 μm is as follows. Let T be the temperature of the object to be measured, and the ratio R (T) of the spectral luminance energy of each wavelength is expressed by the following equation.
[Expression 1]

When equation (1) is approximated by the Vienna formula, equation (3) is obtained.
[Expression 2]

[Equation 3]

Here, α ₁ and α ₂ are coefficients, and c ₂ is a physical constant expressed as follows.
[Expression 4]

c is the speed of light in vacuum, h is Planck's constant, and k is Boltzmann's constant.
Differentiating equation (3) by T and examining the error rate,
[Equation 5]

However, _{n 1} and _{n 2} is as follows.
[Formula 6]

[Expression 7]

The indication error ΔT when the transmittance is attenuated by 2% only by the wavelength λ ₁ = 1.35 μm due to the influence of water vapor in the optical path is 9 ° C. and 700 ° C. when the measurement target temperature T is 500 ° C. Sometimes a large error of 14 ° C is generated.
[0005]
The present invention is for solving such problems, and reduces the fluctuation in indication due to the influence of water vapor in the measurement optical path in the two-color radiation thermometer, and the highly accurate radiation temperature measurement with excellent stability and responsiveness is achieved. An object is to provide a possible two-color radiation thermometer.
[0006]
[Means for Solving the Problems]
This invention is for a two-color radiation thermometer using an InGaAs element as an infrared detection element, in order to minimize the influence of the water vapor absorption band between 0.9 and 1.7 μm, which is the detection wavelength range of the InGaAs element. , A two-color radiation thermometer in which the first wavelength λ ₁ of different measurement wavelengths is 1.1 to 1.3 μm and the second wavelength λ ₂ is 1.45 to 1.7 μm.
[0007]
DETAILED DESCRIPTION OF THE INVENTION
FIG. 1 is an explanatory diagram showing the configuration of an embodiment of the present invention. The objective lens 2 that condenses the light from the measurement object 1, the wavelength division mirror 3 that divides the collected light into the detection element 51 having the first measurement wavelength and the detection element 52 having the second measurement wavelength. A first filter 41 that transmits light only in the first measurement wavelength range of 1.1 to 1.3 μm, and a split light that transmits only 1.45 to 1.7 μm of the second measurement wavelength range. Second filter 42, amplifiers 61 and 62 for amplifying signals from the respective detection elements, analog / digital signal converter 8 for converting the amplified analog signals into digital signals, and a predetermined calculation method based on the digital signals The calculation means 9 calculates the temperature of the measurement object from the ratio R (T) of the spectral luminance energy of each wavelength. Between the amplifiers 61 and 62 and the analog / digital signal converter 8, there is provided a multiplexer 7 for converting several input signals into one output signal in such a manner that each input signal can be reproduced.
[0008]
FIG. 3 shows the result of confirming the indication variation with respect to the optical path length (measurement distance) at the measurement wavelength of the present invention and other measurement wavelengths under the conditions of a measurement temperature of 500 ° C., an ambient temperature of 26 ° C., and a relative humidity of 50% RH. It is. When the first measurement wavelength is 1.2 μm within 1.1 to 1.3 μm and the second measurement wavelength is 1.55 μm within 1.45 to 1.7 μm, which is the measurement wavelength region of the present invention. The indication fluctuation is slight even if the optical path length is changed.
[0009]
In the embodiment of FIG. 1, two filters that divide into two wavelengths by a wavelength division mirror and transmit only a predetermined measurement wavelength range are used. However, as shown in the figure, the disk 10 is equipped with two filters. It is good also as a structure to rotate. The disk 10 is rotated in the direction of the arrow by the motor 11. The disk 10 has a first filter 41 that transmits only 1.1 to 1.3 μm of the first measurement wavelength range, and only 1.45 to 1.7 μm of the divided light in the second measurement wavelength range. The 2nd filter 42 which permeate | transmits is provided. An amplifier 61 that amplifies a signal from one detection element 51, an analog / digital signal converter 8 that converts the amplified analog signal into a digital signal, and a spectral luminance of each wavelength by a predetermined calculation method based on the digital signal It is comprised from the calculating means 9 which calculates the temperature of a measuring object from energy ratio R (T).
[0010]
【The invention's effect】
In the two-color thermometer using the InGaAs infrared detection element, the first wavelength λ ₁ of the different measurement wavelengths is 1.1 to 1.3 μm, and the second wavelength λ ₂ is 1.45 to 1.7 μm. Thus, the influence of water vapor in the optical path can be eliminated, and a two-color thermometer showing a stable indicated value even when the optical path length, that is, the measurement distance is changed, can be realized.
[Brief description of the drawings]
FIG. 1 is a diagram illustrating the configuration of an embodiment of the present invention. FIG. 2 is a diagram illustrating a water vapor transmission rate. FIG. 3 is a comparative graph of indicated variation values. Illustration [Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Measurement object 2 Objective lens 3 Wavelength division | segmentation mirror 41, 42 Filter 51, 52 Detection element 61, 62 Amplifier 7 Multiplexer 8 Analog / digital signal converter 9 Calculation means 10 Disc 11 Motor

Claims (1)

In a two-color radiation thermometer using an InGaAs element as an infrared detection element, the first measurement wavelength of the different measurement wavelengths is 1.1 to 1.3 μm, and the second measurement wavelength is 1.45 to 1.7 μm. A two-color radiation thermometer characterized by the above.

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