Optical analysis device

Abstract

[Problem] To provide an optical analysis device capable of performing measurement at a shorter period of time with a higher accuracy. [Solution] An optical analysis device 1 comprises: a measurement cell 4 incorporated in a gas supply line; a semiconductor light source 2 disposed apart from the measurement cell 4; a distributor 7 that splits light emitted from the semiconductor light source 2 into transmission light 5 with which a measurement target substance in the measurement cell 4 is to be irradiated, and incoming light 6 that does not transmit through the measurement cell 4; a transmitted light detector 8 that detects transmitted light; an incoming light detector 9 that detects the incoming light; a temperature measurement element 10 that measures the state temperature of the semiconductor light source 2; a drive unit 15 that drives and turns on the semiconductor light source 2; and a control unit 17. The optical analysis device 1 stores a characteristic coefficient of the semiconductor light source in a memory 14 in advance, and, by means of a calculation unit 16, calculates the absorption coefficient of the measurement target substance at the time of measurement by using the temperature of the semiconductor light source 2 detected by the temperature measuring element 1 and calculates the concentration of the measurement target substance by absorptiometry.

Description

Cross-reference

[0001] This application claims priority based on Japanese Patent Application No. 2023-043392 filed in Japan on March 17, 2023, and all of the contents described in the application are incorporated herein by reference as they are.

Technical Field

[0002] The present invention relates to an optical analyzer that can accurately measure the concentration of a substance to be measured in a measurement cell by absorptiometry using a semiconductor light source. Specifically, it is an optical analyzer that flows a substance to be measured into a measurement cell, measures the absorption amount of the emitted light irradiated in the measurement cell to calculate the absorbance, calculates an appropriate absorption coefficient corresponding to the absorbance from the state temperature of the semiconductor light source, and improves the measurement accuracy.

Background Art

[0003] Conventionally, in this type of optical analyzer, the concentration is determined by using monochromatic light whose absorption coefficient can match the substance to be measured for the light irradiated on the substance to be measured (see Patent Document 1).

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] However, in measurements using a semiconductor light source, due to the nature of the semiconductor light source (different from a thermal radiation light source), even for the same type of light source, it has a wide emission wavelength range, and the emission wavelength changes due to self-heating and the influence of the ambient temperature. Therefore, in order to improve the measurement accuracy, it is necessary to calculate an appropriate absorption coefficient corresponding to the wavelength change. Here, the appropriate absorption coefficient is the absorption coefficient when a certain compound shows maximum absorption at a single wavelength and is obtained under standard measurement conditions.

[0006] Therefore, as a means of suppressing changes in emission wavelength, it is common to incorporate a temperature control mechanism, such as using a heating element to maintain the state temperature of the semiconductor light source at a constant temperature. However, this mechanism is undesirable for an optical analyzer due to its limitations in miniaturization, structural simplification, power consumption, and high structural costs. Furthermore, the temperature control mechanism does not provide the effect of suppressing the wide emission wavelength range of the semiconductor light source.

[0007] In in-line optical analyzers using semiconductor light sources directly piped into the main line during the manufacturing process, calibration is typically performed by removing the equipment from the piping and comparing concentrations at the manufacturer. This increases the time required for calibration.

[0008] Furthermore, semiconductor light sources exhibit significant variations in emission wavelength and temperature characteristics. To improve measurement accuracy, the light source must be mounted in conjunction with the optical analyzer and its concentration calibrated. However, concentration calibration of semiconductor light sources is difficult in manufacturing environments, and replacing the light source is also challenging. Consequently, variations in emission wavelength and temperature characteristics due to the use of semiconductor light sources negatively impact measurement accuracy.

[0009] Therefore, the present invention aims to provide an optical analysis device that can perform measurements with higher accuracy in a shorter amount of time. [Means for solving the problem]

[0010] (1) An optical analyzer according to one embodiment for achieving the above objective comprises a measuring cell having a channel through which the substance to be measured flows, a semiconductor light source that emits light at a wavelength suitable for the absorption coefficient of the substance to be measured, a transmission window through which the light from the semiconductor light source passes, a transmitted light detector that detects the transmitted light in the measuring cell as the light from the semiconductor light source passes through the transmission window, an incident light detector that detects the incident light that does not pass through the measuring cell, a distributor that splits the light into transmitted light and incident light, a thermometer that measures the state temperature of the semiconductor light source, a temperature sensor that measures the temperature of the substance to be measured, a pressure sensor that measures the pressure of the substance to be measured, and a drive unit that lights up the semiconductor light source. The characteristic coefficient of the semiconductor light source is stored in memory in advance, and the absorption coefficient of the substance to be measured at the time of measurement is calculated by a calculation unit using the temperature detected by the thermometer of the semiconductor light source, and the concentration of the substance to be measured is calculated by the absorbance photometric analysis method. (2) An optical analyzer according to another embodiment for achieving the above objective comprises a measuring cell having a channel through which the substance to be measured flows, a semiconductor light source that emits light at a wavelength suitable for the absorption coefficient of the substance to be measured, a transmission window through which the light from the semiconductor light source passes, a transmitted light detector that detects the transmitted light in the measuring cell as the light from the semiconductor light source passes through the transmission window, an incident light detector that detects the incident light that does not pass through the measuring cell, a distributor that splits the light into transmitted light and incident light, a temperature sensor that measures the temperature of the substance to be measured, a pressure sensor that measures the pressure of the substance to be measured, and a drive unit that lights up the semiconductor light source. The characteristic coefficient of the semiconductor light source is stored in memory in advance, and the absorption coefficient of the substance to be measured at the time of measurement is calculated in a calculation unit using the detected temperature of the semiconductor light source, and the concentration of the substance to be measured is calculated by the absorbance photometric analysis method. (3) In an optical analyzer according to another embodiment, the distributor used for splitting light from a semiconductor light source is preferably a beam splitter or a diffraction grating. (4) In an optical analyzer according to another embodiment, the transmission window is preferably made of sapphire glass or quartz glass. (5) In an optical analyzer according to another embodiment, preferably, the temperature measuring element of the semiconductor light source may use any of the following to detect the state temperature of the mounting pad of the semiconductor light source: a resistance thermometer, a thermistor, a thermocouple, a semiconductor temperature measuring element, or an infrared sensor. (6) In an optical analyzer according to another embodiment, preferably, the temperature measuring element of the semiconductor light source may be placed on the substrate on which the semiconductor light source is mounted to detect the state temperature. (7) In an optical analyzer according to another embodiment, preferably, the temperature measuring element of the semiconductor light source may be a resistance thermometer, a thermistor, a thermocouple, a semiconductor temperature measuring element, or an infrared sensor, which is placed adjacent to the mounting pad of the semiconductor light source and contacts it via heat transfer by radiant heat or a material with high thermal conductivity to detect the state temperature. (8) In an optical analyzer according to another embodiment, preferably, the temperature measuring element may be a resistance thermometer, a thermistor, a thermocouple, a semiconductor temperature measuring element, or an infrared sensor, and may be placed adjacent to a substrate on which a semiconductor light source is mounted, and may come into contact with the substrate via radiant heat or a material with high thermal conductivity to detect the state temperature. (9) In an optical analyzer according to another embodiment, the memory contains: a first characteristic coefficient of the semiconductor light source, which is the intrinsic peak wavelength when the semiconductor light source is measured at a reference temperature; an absorption sensitivity calibration ratio, which is the relative ratio of the absorption coefficient of the intrinsic peak wavelength calculated from the suitable peak wavelength and the intrinsic peak wavelength of the substance to be measured; a third characteristic coefficient of the semiconductor light source, which is the ratio of the absorption coefficient of the intrinsic peak wavelength calculated using the relationship between the standard peak wavelength at the reference temperature and the absorption coefficient of the substance to be measured; and a fourth characteristic coefficient of the semiconductor light source, which is the temperature coefficient of the standard peak wavelength at the reference temperature of the semiconductor light source and the absorption coefficient of the substance to be measured. It is preferable that at least one of the following characteristic coefficients is stored: the absorption temperature coefficient, which is a relative coefficient of the semiconductor light source; the peak wavelength temperature coefficient ratio, which is the relative coefficient between the temperature coefficient at the standard peak wavelength and the temperature coefficient at the intrinsic peak wavelength of the semi-luminescent light source, which is the fifth characteristic coefficient of the semiconductor light source; the appropriate absorption temperature coefficient, which is the temperature coefficient ratio calculated from the relationship between the absorption temperature coefficient ratio and the peak wavelength temperature coefficient ratio at the approved absorption coefficient, which is the authorized absorption coefficient at which the substance under test absorbs the most light; and the appropriate absorption sensitivity coefficient, which is the absorption sensitivity coefficient between the absorption coefficient of the substance under test at the intrinsic peak wavelength at the reference temperature and the approved absorption coefficient, which is the seventh characteristic coefficient of the semiconductor light source. (10) In an optical analyzer according to another embodiment, preferably the calculation unit calculates the appropriate absorption coefficient of the substance to be measured according to the emission wavelength at the time of measurement, using a thermometer that measures the state temperature of the semiconductor light source and the characteristic coefficient of the semiconductor light source. (11) In an optical analyzer according to another embodiment, the state temperature of the semiconductor light source may be arbitrarily changed by varying the current or voltage and frequency of the drive power supply for the semiconductor light source to control the emission wavelength, and the degree of contamination of the transmission window may be calculated based on the absorption coefficient of the substance to be measured corresponding to the emission wavelength to perform zero-point calibration. (12) In an optical analyzer according to another embodiment, preferably the semiconductor light source is detachable and configured to allow the attachment of different semiconductor light sources. [Effects of the Invention]

[0011] According to the present invention, it is possible to provide an optical analysis device that can perform measurements with higher accuracy in a shorter amount of time. [Brief explanation of the drawing]

[0012] [Figure 1] This figure shows the overall configuration of a concentration detection system, including an optical analyzer 1 used in an embodiment of the present invention. [Figure 2] This figure shows the configuration of the optical analyzer 1 used in an embodiment of the present invention. [Figure 3] This figure illustrates the effects in the embodiments of the present invention. [Explanation of symbols]

[0013] 1 Optical analyzer 2 Semiconductor light source 3. Semiconductor manufacturing equipment 4. Measurement cell 7 Distributor 8. Transmitted light detector 9. Incident light detector 10 Temperature measuring element 11. Temperature sensor 12 Pressure Sensor 13 Substrate for mounting light source 14, 34 memory (storage elements) 15. Drive unit (power supply) 16 Arithmetic section 17 Control Unit 20 Inlet 21 Outlet 22 Flow channels 23 Transparent window 24 Main gas line 25 Gas supply equipment [Modes for carrying out the invention]

[0014] Embodiments of the present invention will be described below with reference to the drawings. Note that the embodiments described below are not intended to limit the inventions covered by each claim. Furthermore, not all elements and combinations described in the embodiments are necessarily essential to the solutions of the present invention.

[0015] In this embodiment, Figure 1 shows the overall configuration of the concentration detection system, including the optical analyzer 1 used in the embodiment of the present invention. Figure 2 shows the configuration of the optical analyzer 1 used in the embodiment of the present invention. Figure 3 is a diagram illustrating the effects in the embodiment of the present invention.

[0016] The optical analyzer 1 is connected to the gas supply device 25 and the main gas line 24 of the semiconductor manufacturing apparatus 3. The analyzer 1 is configured such that the substance to be measured (the substance flowing in the direction of the arrow in Figure 1) flows inline into the measurement cell 4 (see Figure 2) from the inlet 20 and outlet 21 located at both ends of the measurement cell 4, which constitutes the optical analyzer 1, and its concentration can be measured.

[0017] [Optical analyzer] As shown in Figure 1, the optical analyzer 1 according to this embodiment includes a measuring cell 4 incorporated into a gas supply line, a semiconductor light source 2 positioned at a distance from the measuring cell 4, a drive unit (light source drive circuit) 15, a transmission window 23 through which light emitted from the semiconductor light source 2 passes through the measuring cell, a distributor 7 that splits the light emitted from the semiconductor light source 2 into transmitted light 5 that irradiates the substance to be measured in the measuring cell 4 and incident light 6 that does not pass through the measuring cell 4, a transmitted light detector 8 that detects the transmitted light, an incident light detector 9 that detects the incident light, a temperature measuring element 10 that measures the state temperature of the semiconductor light source 2, a temperature sensor 11 that measures the temperature of the substance to be measured, a pressure sensor 12 that measures the pressure of the substance to be measured, a drive unit (drive power supply) 15 that drives and lights up the semiconductor light source 2, and a control unit 17.

[0018] The distributor 7 is a beam splitter or diffraction grating used to split the light from the semiconductor light source 2. Sapphire is preferably used as the transmission window 23 because it has resistance and high transmittance to detection light used for density measurement such as ultraviolet light, and is mechanically and chemically stable, but other stable materials, such as quartz glass, can also be used.

[0019] The temperature measuring element 10 is configured to detect the state temperature of the mounting pad of the semiconductor light source 2 using a resistance thermometer, thermistor, thermocouple, semiconductor temperature measuring element, infrared sensor, etc. Alternatively, the temperature measuring element 10 may be configured to detect the state temperature by being placed on the substrate on which the semiconductor light source 2 is mounted. Furthermore, the temperature measuring element 10 may be configured to detect the state temperature by being placed adjacent to the mounting pad of the semiconductor light source 2 and making contact via radiant heat transfer or a material with high thermal conductivity, using a resistance thermometer, thermistor, thermocouple, semiconductor temperature measuring element, infrared sensor, etc. Alternatively, the temperature measuring element 10 may be configured to detect the state temperature by being placed adjacent to the substrate on which the semiconductor light source is mounted and making contact via radiant heat transfer or a material with high thermal conductivity. Alternatively, instead of providing a temperature-measuring element 10, the potential difference (forward voltage) between the anode and cathode electrodes of the diode constituting the semiconductor light source 2 may be detected, and the state temperature of the mounting pad of the semiconductor light source 2 may be detected based on the detected potential difference. In this case, the temperature information based on the potential difference between the anode and cathode electrodes of the diode is stored in the memory (storage element) 14. In this case, a temperature-measuring element is not required, so the configuration becomes simpler.

[0020] The control unit 17 includes a memory (storage element) 14 that stores detection signals from the transmitted light detector 8 and the incident light detector 9, temperature information acquired by the temperature measuring element 10 (including temperature information based on the potential difference between the anode and cathode electrodes in the diode described above), and the characteristic coefficients of the semiconductor light source 2, and a calculation unit 16 that calculates absorbance using the detection signals from the transmitted light detector 8 and the incident light detector 9, and calculates the absorption coefficient of the substance to be measured in the emission of light from the semiconductor light source 2 using the temperature detected by the temperature measuring element 10. The temperature sensor 11, pressure sensor 12, transmitted light detector 8, incident light detector 9, temperature measuring element 10, and drive unit 15 in the measurement cell 4 are electrically connected to the control unit 17, for example, by optical fiber and sensor cable. In this embodiment, a memory 34 having the same function as the memory 14 that stores multiple characteristic coefficients, which will be described later, is provided on the light source mounting substrate 13, but it goes without saying that it may be composed of only one of the memories.

[0021] The memory (memory element) 14 stores multiple characteristic coefficients of the semiconductor light source 2 used, and more specifically, at least one of the following is stored: intrinsic peak wavelength, absorbance sensitivity calibration ratio, standard sensitivity calibration ratio, absorbance temperature coefficient, peak wavelength-temperature coefficient ratio, appropriate absorbance temperature coefficient, and appropriate absorbance sensitivity coefficient. It also stores the various mathematical formulas (calculation processing programs) that appear in the concentration calculation process described later. In the optical analyzer 1, in order to compensate for differences in the optical path length of the measurement cell 4, it is necessary to perform concentration calibration during the manufacturing process and store the cell sensitivity coefficient in absorbance in the memory 14. The definitions of intrinsic peak wavelength, absorbance sensitivity calibration ratio, standard sensitivity calibration ratio, absorbance temperature coefficient, peak wavelength-temperature coefficient ratio, appropriate absorbance temperature coefficient, and appropriate absorbance sensitivity coefficient will be described later.

[0022] The drive unit 15 can arbitrarily change the state temperature of the semiconductor light source 2 by varying the current or voltage and frequency of the power supply for driving the semiconductor light source. Therefore, the emission wavelength of the light emitted from the semiconductor light source 2 can be arbitrarily controlled, and zero-point calibration can be performed by calculating the degree of contamination of the transmission window 23 in the calculation unit 16 based on the absorption coefficient of the substance being measured corresponding to the emission wavelength.

[0023] [Measurement cell] The measuring cell 4 has an inlet 20, an outlet 21, and a longitudinally extending channel 22 for the measuring gas. Translucent windows 23 are provided at both ends of the measuring cell 4 in the direction of transmitted light propagation. Sapphire is preferably used as the transmission window 23 because it has resistance and high transmittance to detection light used for concentration measurement, such as ultraviolet light, and is mechanically and chemically stable, but other stable materials, such as quartz glass, can also be used. In this specification, light includes not only ultraviolet light but also at least infrared light and visible light, and may include electromagnetic waves of any wavelength. Translucency means that the internal transmittance to the light irradiated onto the measuring cell 4 is sufficiently high to enable concentration measurement.

[0024] The pressure sensor 12 detects the pressure of the substance (gas) being measured flowing within the measurement cell 4, and the temperature sensor 11 measures the temperature of the substance being measured. The outputs of the pressure sensor 12 and the temperature sensor 11 are input to the calculation unit 16 of the control unit 17 via a sensor cable (not shown). Multiple temperature sensors 11 may be provided. In addition to resistance thermometers, thermistors and thermocouples can also be used as temperature sensors 11.

[0025] For example, photodiodes and phototransistors are preferably used as the light-receiving elements that constitute the transmitted light detector 8 and the incident light detector 9.

[0026] [Semiconductor light source] The semiconductor light source 2 comprises a light-emitting element (in this case, an LED) that emits ultraviolet light of a predetermined wavelength and a substrate 13 for mounting the light source. A predetermined current or voltage and frequency are output from the drive unit 15, and the intensity of light corresponding to each wavelength component can be measured from the detection signal detected by the transmitted light detector 8. Other light-emitting elements besides LEDs, such as LDs (laser diodes), can also be used as the light-emitting element. The semiconductor light source 2 may also be configured to be detachable. This makes it easier to replace different semiconductor light sources during maintenance. Furthermore, instead of a single-wavelength light source, a combined light source of multiple different wavelengths can be used. In this case, two or more light-emitting elements requiring a multiplexer or frequency analysis circuit may be provided, or the system may be configured to generate incident light using only selected light-emitting elements from among those provided. Moreover, the light emitted by the light-emitting elements is not limited to ultraviolet light; it may also be visible light or infrared light.

[0027] [Control Unit] The control unit 17 is composed of, for example, a processor (including internal memory) provided on a circuit board, and includes a computer program that performs predetermined calculations based on input signals, and can be realized by a combination of hardware and software. In the illustrated embodiment, the calculation unit 16 is configured as part of the control unit 17, but it goes without saying that part of the calculation unit (such as a CPU) or all of it may be provided in a device other than the device including the control unit 17 (for example, a drive device including a drive unit).

[0028] [Concentration measurement process] The calculation unit 16 calculates the absorbance using the detection signals from the transmitted light detector 8 and the incident light detector 9, and calculates the appropriate absorption coefficient α2 of the substance being measured in the emission of light from the semiconductor light source 2 using the detection temperature of the temperature measuring element 10. Specifically, with multiple characteristic coefficients (7) of the semiconductor light source 2 stored in the memory 14 in advance, the calculation unit 16 calculates the absorbance A2 using the detection signals from the transmitted light detector 8 and the incident light detector 9, and calculates the ratio α of the appropriate absorption coefficient α2 of the substance being measured at the time of measurement, which corresponds to the detection temperature Ta detected by the temperature measuring element 10 of the semiconductor light source 2, to the appropriate absorption coefficient α1. f This method involves calculating the concentration C using spectrophotometric analysis.

[0029] [Concentration calculation process] The calculation unit 16 calculates the absorbance A1 at the suitable absorption wavelength from the intensity I0 of the incident light that does not pass through the measurement cell 4 and the intensity I1 of the transmitted light that passes through the substance to be measured in the measurement cell 4, and calculates the concentration C of the substance to be measured according to the following formula (1) based on the Lambert-Beer law. In addition, α1 is the suitable absorption coefficient of the substance to be measured, and L is the optical path length of the measurement cell 4. The suitable absorption wavelength is the wavelength at which the substance to be measured absorbs light best, and the suitable absorption coefficient α1 is a coefficient that represents the characteristic of the substance to be measured to absorb light best at this wavelength. Note that "suitable" means necessary for the substance to be measured to be measurable, and the suitable absorption coefficient is the absorption coefficient derived, for example, with monochromatic light (assuming no wavelength shift), and refers to the absorption coefficient necessary for the substance to be measured to be measurable. A1 = -log 10 (I1 / I0)=α1LC···(1)

[0030] Since the suitable absorption coefficient α1 is determined by the substance to be measured and the suitable emission wavelength, when using the semiconductor light source 2, the emission wavelength also changes in accordance with the change in state temperature, and therefore the absorbance also changes to A2. In this case, the calculation unit 16 calculates the absorption coefficient α2 using the characteristic coefficient of the semiconductor light source 2 (described later) and the detection temperature of the temperature measuring element 10 of the semiconductor light source 2, and calculates the concentration C according to the following formula (2). At this time, the absorbance A2 is calculated from the intensity I2 of the transmitted light that has passed through the substance to be measured in the measurement cell 4 with the changed emission wavelength, according to the following formula (3). The incident light intensity at this time is assumed to be the same intensity as I0 described above. A2 = α2LC ···(2) A2 = -log 10 (I2 / I0) ···(3)

[0031] The appropriate absorption coefficient α2 is calculated using the characteristic coefficient of the semiconductor light source 2 and the detection temperature (Ta) of the temperature sensing element 10 of the semiconductor light source 2, according to the following formulas (4) and (5). In calculating the appropriate absorption coefficient α2, the ratio α2 to the suitable absorption coefficient α1 which forms the basis for concentration calculation is used. fThe appropriate absorption coefficient α1 and ratio α were calculated from the characteristic coefficients of the unique semiconductor light source 2. f Based on this, the appropriate absorption coefficient α2 is calculated. Ratio α f According to this embodiment, the following seven characteristic coefficients (the first to the seventh characteristic coefficients) are used to calculate the characteristic coefficients required. In the following explanation, it is assumed that the same semiconductor light source is used, and absorbance sensitivity is expressed as the magnitude of absorbance as the magnitude of absorbance ability. <First characteristic coefficient> Natural peak wavelength (default peakλ) This refers to the intrinsic peak wavelength of a semiconductor light source when measured at a reference temperature. Here, the reference temperature refers to a predetermined reference temperature within the range of room temperature. The same meaning as above will be used for the reference temperature in the following explanations. <Second characteristic coefficient> Absorption sensitivity calibration ratio (default abs ratio) This refers to the relative ratio between the absorption coefficient calculated from the fitted peak wavelength and the intrinsic peak wavelength of a substance being measured, using the substance's absorption spectrum. Here, the fitted peak wavelength is the wavelength used to calculate the fitted absorption coefficient. <Third characteristic coefficient> ABS standard ratio This refers to the ratio of the absorption coefficient of the intrinsic peak wavelength to the absorbance sensitivity calibration ratio, calculated using the relationship between the standard peak wavelength at a reference temperature (hereinafter referred to as the "standard peak wavelength") and the extinction coefficient of the substance being measured. <Fourth characteristic coefficient> Absorption temperature coefficient (abs temp para) This refers to the relative coefficient between the standard peak wavelength of a semiconductor light source, the temperature coefficient in the absorption coefficient of the substance being measured, and the temperature coefficient in the absorption sensitivity calibration ratio. <Fifth characteristic coefficient> Peak wavelength temperature coefficient ratio (peakλtemp para) This refers to the relative coefficient between the temperature coefficient at the standard peak wavelength and the temperature coefficient at the intrinsic peak wavelength of a hemispherical light source. <The sixth characteristic coefficient> Appropriate absorbance temperature coefficient (abs temp span para) Temperature coefficient ratio calculated based on the relationship between the absorbance temperature coefficient ratio (the fourth characteristic coefficient) and the peak wavelength temperature coefficient ratio (the fifth characteristic coefficient) in the suitable absorbance coefficient <The seventh characteristic coefficient> Appropriate absorbance sensitivity coefficient (conc span para) Refers to the absorbance sensitivity coefficient between the absorbance coefficient of the substance to be measured at the intrinsic peak wavelength at the reference temperature and the suitable absorbance coefficient

[0032] α2 = α1 / α f ······(4) Here, the suitable absorbance coefficient α1 is calculated by the above formula (1). Note that the ortho - optimized absorbance coefficient at which the substance to be measured absorbs most is called the suitable absorption coefficient. Regarding the calculation of the appropriate absorbance coefficient α2, when the temperature rises, the emission wavelength shifts to the long - wavelength side, and when the substance to be measured is irradiated with light of that wavelength, the sensitivity (energy amount) decreases. To correct for this decrease, the appropriate absorbance coefficient α2 is calculated using α f described later and the suitable absorbance coefficient α1. Since the appropriate absorbance coefficient α2 is a corrected absorbance coefficient, this value is applied to formula (2) to calculate the appropriate concentration C. The calculation method of α f is described below. α f = abs span ratio(Ta)×mes ratio(Ta)×conc ratio(Ta)×abs temp span ratio×default abs ratio×conc span para / abs standard ratio ·····(5) Here, the ratio α f is calculated by the above formula (5). Among each parameter, "abs span ratio(Ta)", "mes ratio(Ta)", "conc ratio(Ta)", "abs temp span ratio" are calculated according to the following formulas (5 - 1) to (5 - 10).

[0033] The following explains formulas (5-1) to (5-10) in order. (I) Abs span ratio (Ta): Ratio of intrinsic absorption coefficients at state temperature (a fluctuating value) abs span ratio(Ta)=((abs ratio(Ta)-1)×abs temp para / abs standard ratio+1)×abs standard ratio ····(5-1) Here, (A)abs ratio(Ta)=abs ratio a(Ta)×(real peakλ(Ta)) 4 +abs ratio b(Ta)×(real peakλ(Ta)) 3 +abs ratio c(Ta)×(real peakλ(Ta)) 2 +abs ratio d(Ta)×real peakλ(Ta)+abs ratio e(Ta) ····(5-2) Here, each parameter in formula (5-2) is calculated using the following formulas (5-2-1) to (5-2-5) and (5-3). Abs ratio a(Ta)=(ka1)×(Ta) 4 +(ka²)×(Ta) 3 +(ka3)×(Ta) 2 +(ka4)×(Ta)+(ka5) ·····(5-2-1) • Abs ratio b(Ta) = (kb1) × (Ta) 4 +(kb2)×(Ta) 3 +(kb3)×(Ta) 2 +(kb4)×(Ta)+(kb5) ·····(5-2-2) • Abs ratio c(Ta) = (kc1) × (Ta) 4 +(kc²)×(Ta) 3 +(kc3)×(Ta) 2 +(kc4)×(Ta)+(kc5) ·····(5-2-3) • Abs ratio d(Ta) = (kd1) × (Ta) 4 +(kd2)×(Ta) 3 +(kd3)×(Ta) 2 +(kd4)×(Ta)+(kd5) ·····(5-2-4) Abs ratio e(Ta) = (ke1) × (Ta) 4 +(ke2)×(Ta) 3 +(ke3)×(Ta) 2 +(ke4)×(Ta)+(ke5) ····(5-2-5) Note that ka1~ka5, kb1~kb5, kc1~kc5, kd1~kd5, and ke1~ke5 are constants.

[0034] (B)real peakλ(Ta)={{(real peakλa(Ta)×(peakλ(Ta)) 2 +real peakλb(Ta)×peakλ(Ta)+real peakλc(Ta))-1}×peakλtemp para+1}×default peakλ ····(5-3) Here, each parameter in formula (5-3) is calculated using the following formulas (5-3-1) to (5-3-5) and (5-4). ·real peakλa(Ta)=(wa1)×(Ta) 2 +(wa2)×Ta+(wa3) ...(5-3-1) ·real peakλb(Ta)=(wb1)×(Ta) 2 +(wb2)× Ta+(wb3) ...(5-3-2) ·real peakλc(Ta)=(wc1)×(Ta) 2 +(wc2)×Ta+(wc3) ...(5-3-3) Note that wa1~wa3, wb1~wb3, and wc1~wc3 are constants. (C)peakλ(Ta)={(z1)×(Ta) 2 +(z2)×(Ta)+(z3)}×(default peakλ) ····(5-4) Note that z1 to z3 are constants.

[0035] (II) mes ratio (Ta): Ratio of inherent extinction coefficients at reference temperature mes ratio(Ta)=mes ratio a(To)×(real peakλ(Ta)) 3 +mes ratio b(To)×(real peakλ(Ta)) 2 +mes ratio c(To)×real peakλ(Ta)+mes ratio d(To) ·········(5-5) Here, each parameter in equation (5-5) is calculated using the following equations (5-5-1) to (5-5-4). (A)mes ratio a(To)=(ma1)×(To) 3 +(ma2)×(To) 2 +(ma3)×(To)+(ma4) ····(5-5-1) (B)mes ratio b(To)=(mb1)×(To) 3 +(mb2)×(To) 2 +(mb3)×(To)+(mb4) ·····(5-5-2) (C)mes ratio c(To)=(mc1)×(To) 3 +(mc²)×(To) 2 +(mc3)×(To)+(mc4) ·····(5-5-3) (D)mes ratio d(To)=(md1)× (To) 3 +(md²)×(To) 2 +(md3)×(To)+(md4) ·····(5-5-4) Note that ma1~ma4, mb1~mb4, mc1~mc4, and md1~md4 are constants, and the real peakλ(Ta) is calculated from formula (5-3).

[0036] (III) Conc ratio (Ta): Suitable absorption coefficient ratio at reference temperature conc ratio(Ta)=conc ratio a(To)×(real peakλ(Ta)) 3 +conc ratio b(To)×(real peakλ(Ta)) 2 + conc ratio c(To)×real peakλ(Ta)+conc ratio d(To) ····(5-6) Here, each parameter in equation (5-6), excluding real peakλ(Ta), is calculated using the following equations (5-6-1) to (5-6-4), and real peakλ(Ta) is calculated from equation (5-3). (A)conc ratio a(To)=(na1)×(To) 3 +(na2)×(To) 2 +(na3)×(To)+(na4) ····(5-6-1) (B)conc ratio b(To)=(nb1)×(To) 3 +(nb2)×(To) 2 +(nb3)×(To)+(nb4) ·····(5-6-2) (C)conc ratio c(To)=(nc1)×(To) 3 +(nc2)×(To) 2 +(nc3)×(To)+(nc4) ····(5-6-3) (D)conc ratio d(To)=(nd1)×(To) 3 +(nd2)×(To) 2 +(nd3)×(To)+(nd4) ····(5-6-4) Note that na1~na4, nb1~nb4, nc1~nc4, and nd1~nd4 are constants, and the real peakλ(Ta) is calculated from formula (5-3).

[0037] (IV) Abs temp span ratio: Ratio of the inherent absorption coefficient at the state temperature to the reference temperature abs temp span ratio (Ta)=(((abs ratio (To)-1)×abs temp para / abs standard ratio +1) / ((abs ratio (Ta)-1)×abs temp para / abs standard ratio+1))-1)×abs temp span para+1 ······(5-7) The abs ratio (Ta) is calculated using formula (5-2), and the abs ratio (To) is calculated using the following formula (5-8). (A)abs raite(To)=abs ratio a(To)×(real peakλ(To)) 4 +abs ratio b(To)×(real peakλ(To)) 3 +abs ratio c(To)×(real peakλ(To)) 2 +abs ratio d(To)×real peakλ(To) + abs ratio e(To) ····(5-8) Here, each parameter in equation (5-8) is calculated using the following equations (5-8-1) to (5-8-5). (B)abs ratio a(To)=(ka1)×(To) 4 +(ka2)×(To) 3 +(ka3)×(To) 2 +(ka4)×(To)+(ka5) ····(5-8-1) (C)abs ratio b(To)=(kb1)×(To) 4 +(kb2)×(To) 3 +(kb3)×(To)2 +(kb4)×(To)+(kb5) ·····(5-8-2) (D)abs ratio c(To)=(kc1)×(To) 4 +(kc2)×(To) 3 +(kc3)×(To) 2 +(kc4)×(To)+(kc5) ·····(5-8-3) (E)abs ratio d(To)=(kd1)×(To) 4 +(kd2)×(To) 3 +(kd3)×(To) 2 +(kd4)×(To)+(kd5) ·····(5-8-4) (F)abs ratio e(To)=(ke1)×(To) 4 +(ke2)×(To) 3 +(ke3)×(To) 2 +(ke4)×(To)+(ke5) ·····(5-8-5) Note that ka1~ka5, kb1~kb5, kc1~kc5, kd1~kd5, and ke1~ke5 are constants.

[0038] (IV-1) Here, the real peakλ(To) is calculated using the following formula (5-9). (A)real peakλ(To)={{(real peakλa(To)×(peakλ(To)) 2 +real peakλb(To)×peakλ(To)+real peakλc(To))-1}×peakλtemp_para+1}×default peakλ ...(5-9) The real peakλa(To), real peakλb(To), and real peakλc(To) in formula (5-9) are calculated from the following formulas (5-9-1) to (5-9-3), respectively. (a1)real peakλa(To)=(wa1)×(To) 2 +(wa2)×To+(wa3) ...(5-9-1) (a2)real peakλb(To)=(wb1)×(To) 2 +(wb2)×To+(wb3) ...(5-9-2) (a3)real peakλc(To)=(wc1)×(To) 2 +(wc2)×To+(wc3) ...(5-9-3) Note that wa1~wa3, wb1~wb3, and wc1~wc3 are constants. Furthermore, peakλ(To) in equation (5-9) is calculated from the following equation (5-10). (a4) peakλ(To) = {(z1) × (To)} 2 +(z2)×(To)+(z3)}×(default peakλ) ...(5-10) Note that z1 to z3 are constants.

[0039] As explained above, the concentration C is calculated using equations (1) to (5). In the embodiment described above, the calculation unit 16 receives state temperature information from the temperature measuring element 10 in real time and performs calculations according to equations (1) to (5). However, it is also possible to store the calculation results of equations (1) to (5) for multiple state temperatures in memory as a table in advance, and automatically calculate the concentration when the actual detected state temperature is received.

[0040] When treating concentration C as the standard state concentration Co, the measurement temperature Tc (°C) and state pressure Pa (kPa) of the substance to be measured are detected by the temperature sensor 11 and pressure sensor 12, respectively, and the concentration is converted based on the following formula (6). Co=C×{(273.15+Tc) / 273.15}×{101.32 / (101.32+Pa)} ...(6)

[0041] [Examples] In this embodiment, the calculation unit 16 calculates the ratio α1 (ozone gas) to the appropriate absorption coefficient when the detected temperature (Ta) of the temperature measuring element 10 of the semiconductor light source 2 changes in four stages: 15°C, 25°C, 35°C, and 45°C. f This is calculated by performing the above formula (5) using the characteristic coefficient of the semiconductor light source 2 and the detection temperature of the temperature measuring element 10 of the semiconductor light source 2, and the suitable absorption coefficient α1 at the state temperature during measurement and the ratio α calculated above are obtained. f The appropriate absorption coefficient α2 was calculated by substituting these values ​​into equation (4). Then, based on the absorbance A2 at the time of measurement, the optical path length L of the measurement cell 4, and the appropriate absorption coefficient α2, the concentration C was calculated according to equation (2).

[0042] Figure 3(a) shows the characteristics showing the relationship between the concentration C, calculated using a semiconductor light source based on the concentration calculation method described above and converted to an ozone gas concentration value, and the detection temperature (Ta) of the thermometer 10. Figure 3(b) also shows the characteristics showing the relationship between the concentration C, calculated using a semiconductor light source and converted to an ozone gas concentration value, and the detection temperature (Ta) of the thermometer 10, under conditions where the first to seventh characteristic coefficients are not applied.

[0043] Characteristic graph (c) shows the characteristic graph when a mercury lamp is used as the light source, and monochromatic light that matches the absorption coefficient of the ozone gas being measured is used to calculate the absorbance A1 from the incident light intensity I0 that does not pass through the measurement cell 4 and the transmitted light intensity I1 that passes through the ozone gas inside the measurement cell 4. The concentration C of the substance being measured is then calculated according to formula (1) using the matching absorption coefficient α1, which forms the basis for concentration calculation based on the Lambert-Beer law.

[0044] Characteristic graph (c) is calculated using formula (1) assuming that absorbance A1 does not change in response to changes in light source temperature, and as the temperature detected by the light source's thermometer increases, the ozone gas concentration gradually increases. On the other hand, as shown in characteristic graph (b), when absorbance A1 changes to A2 in response to changes in light source temperature and the first to seventh characteristic coefficients are not applied, as the temperature detected by the light source's thermometer increases, the ozone gas concentration gradually decreases, and the measurement accuracy deteriorates.

[0045] Therefore, when the absorbance A1 changes to A2 in response to a change in the light source temperature, and the first to seventh characteristic coefficients are applied, as shown in (a) of the characteristic graph, as the temperature detected by the temperature sensing element of the light source increases, there is almost no increase in the ozone gas concentration, indicating high measurement accuracy.

[0046] [Effects of this embodiment] Therefore, with the optical analyzer according to this embodiment, it is possible to improve the accuracy of concentration measurement without performing temperature control to maintain a constant state temperature of the semiconductor light source using a heating element or the like. Furthermore, in conventional in-line optical analyzers that are directly piped into the main line in the manufacturing process, sensitivity calibration for concentration comparison is not possible, so calibration is generally performed by removing the analyzer from the piping and having it done at the manufacturer. However, with this embodiment, measurements can be taken without removing the analyzer described above, so measurements can be taken in a shorter time.

[0047] Furthermore, when the state temperature of the semiconductor light source rises during measurement, the emission wavelength shifts to the longer wavelength side, and when the material being measured is irradiated with light of that wavelength, the sensitivity (energy amount) decreases. To compensate for this decrease, the appropriate absorption coefficient α2 is set to the above α f By calculating the appropriate absorption coefficient α2 using the suitable absorption coefficient α1 and applying the corrected appropriate absorption coefficient α2 to the above formula (2), the appropriate concentration C can be calculated, thus enabling more accurate measurements.

[0048] Furthermore, in the above-described embodiment, more accurate measurements can be achieved by performing the following process. Using the optical analyzer according to this embodiment, the following measurements are performed on different substances to be measured (a first substance to be measured and a second substance to be measured). The concentration of the first substance to be measured is constant, and the state temperature of the semiconductor light source is arbitrarily changed by the power supply for the semiconductor light source (the emission wavelength changes and two emission wavelengths are identified). The concentration (Cx) is calculated from two or more absorption coefficients (αx) and absorbances (Ax) corresponding to each emission wavelength. The appropriate absorption coefficient (α2) and absorbance (A2) of the substance to be measured at each concentration are calculated based on the spectrophotometric analysis method, and the first concentration C1 corresponding to each emission wavelength is calculated from the respective appropriate absorption coefficients (α2) and absorbances (A2). The concentration of the second substance to be measured is kept constant, and the state temperature of the semiconductor light source is arbitrarily changed by the power supply driving the semiconductor light source (changing the emission wavelength and identifying two emission wavelengths). The concentration (Cx) is calculated from two or more absorption coefficients (αx) and absorbances (Ax) corresponding to each emission wavelength. The appropriate absorption coefficient (α2) and absorbance (A2) of the substance to be measured at each concentration are calculated based on the spectrophotometric analysis method, and the second concentration C2 corresponding to each emission wavelength is calculated from the appropriate absorption coefficient (α2) and absorbance (A2). As a result, different concentrations of the measured substance C1 and C2 are obtained. By calculating the degree of contamination from these different concentrations of the measured substance C1 and C2 and performing zero-point calibration, the measurement accuracy can be improved. Note that αx, Ax, Cx, α2, and A2 are as follows. αx: Any extinction coefficient corresponding to the emission wavelength. Ax: Any absorbance corresponding to the emission wavelength. Cx: Concentration determined from an arbitrary absorption coefficient and absorbance corresponding to the emission wavelength. α2: The appropriate absorption coefficient at that time A2: Absorbance at the appropriate absorption coefficient at that time [Industrial applicability]

[0049] [Applications in the field of measurement] By arbitrarily changing the emission wavelength using a semiconductor light source's power supply, in spectrophotometric analysis, concentration errors can be identified using the relationship between the absorption coefficient of the substance being measured and wavelengths that do not match. In fluorescence analysis, the intensity of reflected fluorescence obtained by scanning the irradiation wavelength can be used to identify concentration errors and apply to qualitative and quantitative analysis.

[0050] [Applications in the field of sterilization] In the field of sterilization and disinfection using ultraviolet wavelengths, it is known that the effect varies greatly depending on the wavelength range of the light. By arbitrarily controlling the emission wavelength with the power supply for the semiconductor light source and detecting the state temperature of the semiconductor light source with a thermometer (which detects the potential difference (forward voltage) between the anode and cathode electrodes of the diode constituting the semiconductor light source 2), the emission wavelength can be monitored and applied to appropriate wavelength control.

Claims

1. The device comprises a measuring cell having a channel through which the substance to be measured flows, a semiconductor light source that emits light at a wavelength suitable for the absorption coefficient of the substance to be measured, a transmission window through which the light from the semiconductor light source passes, a transmitted light detector that detects the transmitted light within the measuring cell as the light from the semiconductor light source passes through the transmission window, an incident light detector that detects incident light that does not pass through the measuring cell, a distributor that splits the light into transmitted light and incident light, a temperature measuring element that measures the state temperature of the semiconductor light source, and a drive unit that lights up the semiconductor light source. The characteristic coefficients of the semiconductor light source are stored in memory in advance, and the absorption coefficient of the substance to be measured at the time of measurement is calculated in the calculation unit using the detection temperature of the temperature sensing element of the semiconductor light source and the characteristic coefficients of the semiconductor light source determined by the change in temperature based on the detection temperature of the temperature sensing element, and the concentration of the substance to be measured is calculated by the absorbance photometric analysis method. An optical analysis apparatus characterized by the following features.

2. The system comprises a measuring cell having a channel through which the substance to be measured flows, a semiconductor light source emitting light at a wavelength suitable for the absorption coefficient of the substance to be measured, a transmission window through which the light from the semiconductor light source passes, a transmitted light detector that detects the transmitted light within the measuring cell as the light from the semiconductor light source passes through the transmission window, an incident light detector that detects incident light that does not pass through the measuring cell, a distributor that splits the light into transmitted and incident light, and a drive unit that lights up the semiconductor light source. The system stores the characteristic coefficient of the semiconductor light source in memory in advance, and uses the detection temperature of the semiconductor light source to calculate the absorption coefficient of the substance to be measured at the time of measurement using the characteristic coefficient of the semiconductor light source determined by the change in temperature based on the detection temperature of the semiconductor light source. The system then calculates the concentration of the substance to be measured by spectrophotometric analysis. An optical analysis apparatus characterized by the following features.

3. The distributor used for splitting light from the aforementioned semiconductor light source is a beam splitter or a diffraction grating. The optical analyzer according to feature 1.

4. The distributor used for splitting light from the aforementioned semiconductor light source is a beam splitter or a diffraction grating. The optical analyzer according to feature 2.

5. The aforementioned transparent window is made of sapphire glass or quartz glass. The optical analyzer according to feature 1.

6. The aforementioned transparent window is made of sapphire glass or quartz glass. The optical analyzer according to feature 2.

7. The temperature measuring element of the semiconductor light source detects the state temperature of the mounting pad of the semiconductor light source using one of the following: a resistance thermometer, a thermistor, a thermocouple, a semiconductor temperature measuring element, or an infrared sensor. The optical analyzer according to feature 1.

8. The temperature measuring element of the semiconductor light source is disposed on the substrate on which the semiconductor light source is mounted and detects the state temperature. The optical analyzer according to feature 1.

9. The temperature-measuring element of the semiconductor light source uses one of the following: a resistance thermometer, a thermistor, a thermocouple, a semiconductor temperature-measuring element, or an infrared sensor, and is positioned adjacent to the mounting pad of the semiconductor light source, making contact via heat transfer by radiant heat or through a material with high thermal conductivity, to detect the state temperature. The optical analyzer according to feature 1.

10. The temperature measuring element is configured to detect the state temperature by using one of the following: a resistance thermometer, a thermistor, a thermocouple, a semiconductor temperature measuring element, or an infrared sensor, and is positioned adjacent to the substrate on which the semiconductor light source is mounted, and making contact via heat transfer by radiant heat or through a material with high thermal conductivity. The optical analyzer according to feature 1.

11. In the aforementioned memory, The first characteristic coefficient of the semiconductor light source is the intrinsic peak wavelength when the semiconductor light source is measured at a reference temperature, The second characteristic coefficient of the semiconductor light source is the absorbance sensitivity calibration ratio, which is the relative ratio of the absorption coefficient calculated from the suitable peak wavelength and the intrinsic peak wavelength of the substance to be measured, The third characteristic coefficient of the semiconductor light source is the standard sensitivity calibration ratio, which is the ratio of the absorption coefficient of the intrinsic peak wavelength calculated using the relationship between the standard peak wavelength at a reference temperature and the absorption coefficient of the substance to be measured, to the absorption sensitivity calibration ratio. The fourth characteristic coefficient of the semiconductor light source is the absorption temperature coefficient, which is the relative coefficient between the standard peak wavelength at the reference temperature of the semiconductor light source and the temperature coefficient in the absorption coefficient of the substance being measured, The fifth characteristic coefficient of the semiconductor light source is the peak wavelength temperature coefficient ratio, which is the relative coefficient between the temperature coefficient at the standard peak wavelength of the semiconductor light source and the temperature coefficient at the intrinsic peak wavelength, The sixth characteristic coefficient of the semiconductor light source is the appropriate absorption temperature coefficient, which is the temperature coefficient ratio calculated from the relationship between the absorption temperature coefficient ratio of the approved absorption coefficient, which is the authorized absorption coefficient at which the substance under test absorbs the most light, and the peak wavelength temperature coefficient ratio. The semiconductor light source stores at least one characteristic coefficient among the appropriate absorbance sensitivity coefficients, which are the seventh characteristic coefficients of the semiconductor light source and are the absorbance sensitivity coefficients obtained by comparing the absorbance coefficient of the substance under test at the intrinsic peak wavelength at a reference temperature with the appropriate absorbance coefficient. The optical analyzer according to any one of the features 1 to 10.

12. The calculation unit calculates the absorption coefficient of the substance to be measured according to the emission wavelength at the time of measurement, using the state temperature of the semiconductor light source and the characteristic coefficient of the semiconductor light source described in claim 9. The optical analyzer according to feature 11.

13. By varying the power of the power supply for the semiconductor light source, the state temperature of the semiconductor light source is arbitrarily changed to control the emission wavelength, and zero-point calibration is performed by calculating different concentrations of measured substances and the degree of contamination of the transmission window from the absorption coefficient. The optical analyzer according to feature 1 or 2.

14. The semiconductor light source is detachable. The optical analyzer according to feature 1 or 2.

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