Light source device and concentration measurement device

Abstract

To stabilize a forward voltage of a semiconductor light emitting element to accurately measure the concentration of solutes dissolved in various solutions such as aqueous solutions and of each gas in a mixed gas.SOLUTION: A light source device 2 has an LED 21 and the following parts. A constant current drive circuit 101 supplies a constant current toward the LED 21. A current correction circuit 102 sends a part of the constant current supplied from the constant current drive circuit 101 to a bypass circuit 124 as a bypass current, supplies the remaining current to the LED 21 as an LED current, reduces the bypass current when the LED current is smaller than a predetermined target current value, and corrects the bypass current to be increased when the LED current is larger than the predetermined target current value.SELECTED DRAWING: Figure 2

Description

Technical Field

[0001] The present invention relates to a light source device used for measuring the concentration of a measurement object such as a solution, and a concentration measurement device that performs the measurement.

Background Art

[0002] Conventionally, a technique for measuring the concentration of an aqueous solution such as a semiconductor etching solution or a cleaning solution using light has been known. As an example of such a technique, there is a technique of irradiating light from an LED (Light Emitting Diode), which is a semiconductor light emitting element, onto an aqueous solution, and measuring the concentration of the aqueous solution from the emission intensity and the intensity of the light received through the aqueous solution.

[0003] For example, a technique has been proposed in which the forward voltage (forward bias voltage) when a constant current is passed through an LED is acquired in advance, and the concentration of the measurement object is measured based on the correspondence information indicating the relationship with the emission intensity of light of a specific wavelength emitted by the LED, the forward voltage measured by the measurement unit, and the intensity of light of the specific wavelength spectrally analyzed by the spectroscopic unit. More specifically, there is a method of estimating the emission intensity from the forward voltage Vf of an LED, which is a light source, and calculating the concentration of the measurement object from the estimated emission intensity and the received light intensity of a specific wavelength detected by a spectroscope.

[0004] As the constant current drive circuit for an LED, a linear method capable of high-speed response and high-precision current control, and a switching method with low heat generation in the circuit, that is, low power consumption, are known.

[0005] When performing concentration measurement using the forward voltage of an LED, in order to accurately measure the concentration of a liquid, it is desirable to make the forward voltage of the LED as stable as possible. For example, if the change amount of the forward voltage is large or the reproducibility is poor, it becomes difficult to estimate the emission intensity. However, since the forward voltage changes depending on the drive current of the LED, in order to stabilize the forward voltage of the LED, it is desirable to make the drive current as highly accurate and stable as possible.

[0006] Also, since the forward voltage changes depending on the heat generation temperature of the LED itself, in order to stabilize the forward voltage of the LED, it is desirable to set the lighting time to the minimum required time. The minimum required lighting time is the shortest time required for measuring the received light intensity by the spectroscope. For this, it is desirable to make the LED dynamic lighting (intermittent lighting) and further make the rise response of the drive current from the off state to the on state as fast as possible.

[0007] For example, if the rise response is slow, it is necessary to lengthen the lighting time accordingly, which increases the amount of heat generated and affects the forward voltage. As a countermeasure, in order to suppress the overall heat generation amount, it is conceivable to lengthen the off time by the same amount as the lengthened lighting time and lengthen the blinking cycle (= PWM (Pulse Width Modulation) cycle). However, when the blinking cycle is lengthened, the detection cycle on the light-receiving side also becomes longer, so the response speed of the concentration measurement becomes slower, and as a result, the performance of the concentration measurement device is affected. For example, it is conceivable that it becomes difficult to detect bubbles. Therefore, it is possible to measure the concentration more accurately by making the rise response faster and suppressing the variation of the forward voltage rather than suppressing the variation of the forward voltage while keeping the rise response slow. In addition, since the luminous intensity of the LED gradually decreases with its lifespan, it is generally also practiced to extend the lifespan as a dynamic lighting method.

[0008] Furthermore, since the forward voltage also changes due to the influence of the ambient temperature, in order to stabilize the forward voltage of the LED, it is generally desirable that the heat generation of the components of the LED drive circuit arranged near the LED or within the same case be as small as possible.

Prior Art Documents

Patent Documents

[0009]

Patent Document 1

Patent Document 2

Patent Document 3

Patent Document 4

Summary of the Invention

Problems to be Solved by the Invention

[0010] Regarding the high-precision and high-stability of the drive current and the high-speed rise response of the drive current from the off state to the on state, it can be solved by using a linear constant-current drive circuit. However, in the case of a linear type, the current control transistor generates heat, so it is difficult to solve the minimization of component heat generation in the LED drive circuit.

[0011] Also, if a switching type constant-current drive circuit is used, the heat generation of the current control transistor is significantly reduced compared to the linear type, so the minimization of component heat generation in the LED drive circuit can be solved. However, in a switching type constant-current drive circuit, it has been difficult to solve the high-precision and high-stability of the drive current and the high-speed rise response of the drive current from the off state to the on state. That is, in the case of a switching type, a ripple current is generated in principle, and due to the capacitance of the smoothing capacitor for removing this ripple current, the rise of the LED current becomes slow. Also, if the capacitance of the smoothing capacitor is reduced to increase the rise speed of the LED current, it becomes difficult to completely remove the ripple current, a large ripple occurs in the LED current, and the stability of the emission intensity deteriorates. Furthermore, the ripple of the current detection signal due to the current detection resistor in the constant current control circuit also increases, making high-precision constant current control difficult. In addition, if the peak of the LED current due to this ripple exceeds the maximum rated current of the LED element, the LED element may deteriorate and the life may be significantly shortened.

[0012] As described above, in the conventional LED drive circuit, it has been difficult to solve all three problems: high-precision and high-stability of the drive current, high-speed rise response of the drive current from the off state to the on state, and minimization of component heat generation in the LED drive circuit. That is, in the conventional LED drive circuit, it has been difficult to stabilize the forward voltage of the LED and accurately measure the concentration.

[0013] This application is for solving such problems, and aims to stabilize the forward voltage of a semiconductor light-emitting element and accurately measure the concentration of a solute dissolved in various solutions such as an aqueous solution or each gas in a mixed gas.

Means for Solving the Problems

[0014] The light source device according to the present application includes a semiconductor light-emitting element, a constant current drive circuit that supplies a constant current to the semiconductor light-emitting element, and a part of the constant current supplied from the constant current drive circuit is sent to a bypass circuit as a bypass current, and the remaining current is supplied to the semiconductor light-emitting element as a semiconductor light-emitting element current. When the semiconductor light-emitting element current is smaller than a predetermined target current value, the bypass current is reduced, and when the semiconductor light-emitting element current is larger than the predetermined target current value, a current correction circuit that corrects to increase the bypass current is provided.

[0015] In the above light source device, the constant current drive circuit may have a switching element and a switching control circuit that controls the on / off of the switching element, and the constant current may be completely supplied according to the on / off operation of the switching element.

[0016] Also, in the above light source device, the current correction circuit may execute the correction operation of the bypass current faster than the on / off operation of the switching element of the constant current drive circuit.

[0017] Also, in the above light source device, the constant current drive circuit may control the switching element based on a timing signal given from the outside.

[0018] Also, in the above light source device, the switching control circuit may control the on / off interval of the switching element based on the detected value of the constant current output from the constant current drive circuit.

[0019] Further, in the above-described light source device, the current correction circuit may control the magnitude of the bypass current based on the forward voltage of the semiconductor light-emitting element detected by a semiconductor light-emitting element current detection resistor disposed on the output side of the semiconductor light-emitting element and a reference voltage.

[0020] Further, in the above-described light source device, the current correction circuit may have a differential amplification circuit, compare the voltage value of the voltage output from the differential amplification circuit with the reference voltage using the forward voltage as an input, and control the magnitude of the bypass current.

[0021] Further, in the above-described light source device, the constant current drive circuit may have a high-side current detection circuit that detects the current value of a constant current between the input terminal of the input voltage and the semiconductor light-emitting element, control the constant current based on the current value detected by the high-side current detection circuit, and the current correction circuit may control the magnitude of the bypass current based on the difference between the voltage value of the forward voltage and the voltage value of the reference voltage.

[0022] Further, in the above-described light source device, the current correction circuit may set the bypass current to 25% or less of the constant current.

Advantages of the Invention

[0023] According to the above-described light source device, among the output current smoothed by the smoothing capacitor output from the constant current drive circuit, the current exceeding the control target value of the semiconductor light-emitting element current flows as the bypass current through the bypass path. As a result, the capacitance of the smoothing capacitor can be set to the minimum necessary capacitance. And all three problems of high-precision and high-stability of the drive current, high-speed rise response of the drive current from the off state to the on state, and minimization of component heat generation in the semiconductor light-emitting element drive circuit can be solved. Therefore, it becomes possible to stabilize the forward voltage of the semiconductor light-emitting element and accurately measure the concentration of solutes dissolved in various solutions such as aqueous solutions and each gas in a mixed gas.

Brief Description of the Drawings

[0024]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

[0025] Next, embodiments will be described with reference to the drawings. In the following description, the same reference numerals are given to the common components in each embodiment, and repeated descriptions are omitted.

[0026] [Principle of Measurement Method] As cleaning liquids and etching liquids for semiconductors, aqueous solutions such as hydrochloric acid, nitric acid, phosphoric acid, ammonium hydroxide, and hydrogen peroxide are used, and a technique for measuring the concentration of an aqueous solution based on the absorbance of the aqueous solution is known. Simply, light is irradiated onto the aqueous solution, and the transmitted light is spectrally analyzed at two or more wavelengths of light, and the light intensity is measured to calculate the concentration. More specifically, the absorbance of the aqueous solution is calculated from the intensity of the light spectrally analyzed from the light emitted by the light source and the intensity of the light spectrally analyzed from the transmitted light, and the concentration is calculated based on the calculated absorbance. Here, an LED is used as the light source used for such concentration measurement.

[0027] FIG. 1 is a diagram for explaining the measurement method in the embodiment. The measurement method in the embodiment will be described with reference to FIG. 1.

[0028] For example, the concentration measuring device 1 includes a light source device 2, a flow cell 3, a spectroscopic device 4, and a measuring device 5.

[0029] The light source device 2 is a light source device capable of projecting light, and is realized with an LED 21, which is a semiconductor light-emitting element, as the light source. For example, the LED 21 emits light including a predetermined specific wavelength according to the control by the measuring device 5. The light emitted by the LED 2 in this way is transmitted along the optical path OP, through the flow cell 3, to the spectroscopic device 4.

[0030] Here, the LED 21 is a light source capable of emitting light in a wavelength band including a specific wavelength corresponding to each of the solutes whose concentrations are measured one by one or simultaneously. That is, the LED 21 is a light source capable of emitting light of a specific wavelength corresponding to the measurement object with an intensity (for example, illuminance) necessary and sufficient for the measurement of the measurement object. For example, the LED 21 is a light source having a center wavelength of about 1550 nanometers and a half-value width of about 100 nanometers. In this case, when the solutes are ammonia and hydrogen peroxide, the LED 21 is optimally a light source capable of outputting light in a wavelength band of at least 1500 nanometers to 1600 nanometers with sufficient intensity, but other wavelength bands may be used instead of this wavelength band. In this case, a light source whose center wavelength matches the used wavelength band is selected.

[0031] Note that the LED 21 only needs to use, as the specific wavelength, light of a wavelength that can be spectrally captured by the spectroscopic device 4, and can emit light in a wavelength width including such a specific wavelength. In other words, the LED 21 uses, as the specific wavelength, a wavelength capable of realizing the measurement of the absorbance (and thus the concentration) of the measurement object with a preset target accuracy, and emits light of a wavelength matching the specific wavelength.

[0032] The flow cell 3 is made of a material (for example, quartz glass, etc.) that is transparent to the light emitted by the light source device 2, and a sample such as an aqueous solution can flow inside. Note that the flow cell 3 may be realized by a test tube, a cell, etc., or may be the piping itself through which the chemical solution flows. Further, the flow cell 3 does not necessarily need to be entirely made of a transparent material, and it is sufficient that the incident portion where the light emitted from the light source device 2 is incident and the emission portion where the incident light is emitted through the sample are transparent to the specific wavelength.

[0033] The spectroscopic device 4 is a device that spectroscopically analyzes light of a specific wavelength from the light received through the flow cell 3 and measures the intensity of the spectroscopically analyzed light. For example, it is realized by a Fabry - Perot interferometer and a light - receiving element that measures the intensity of the light spectroscopically analyzed by the Fabry - Perot interferometer. However, the spectroscopic device 4 may use a spectroscope using another spectroscopic method such as a grating - type spectroscope.

[0034] For example, the spectroscopic device 4 includes a tunable filter 41 for Fabry - Perot spectroscopy and a light - receiving element 42. The tunable filter 41 for Fabry - Perot spectroscopy is a Fabry - Perot interferometer capable of changing the wavelength of the light that can pass through, and has two semi - transparent mirrors arranged in parallel. For example, the tunable filter 41 for Fabry - Perot spectroscopy has an upper mirror UM which is a semi - transparent mirror installed on the light - source device 2 side and a lower mirror DM which is a semi - transparent mirror arranged on the light - receiving element 42 side. Then, the tunable filter 41 for Fabry - Perot spectroscopy controls the distance between the upper mirror UM and the lower mirror DM, and transmits light of a wavelength corresponding to the distance between the upper mirror UM and the lower mirror DM from the light received through the flow cell 3. For example, the tunable filter 41 for Fabry - Perot spectroscopy transmits light of a specific wavelength corresponding to the solute from the light received through the sample according to the control from the measuring device 5.

[0035] When the light - receiving element 42 receives the light transmitted by the tunable filter 41 for Fabry - Perot spectroscopy, it is an element that measures the intensity of the received light, and is realized by, for example, a photoelectric element such as a photodiode. For example, when the light - receiving element 42 receives the transmitted light, it generates an electrical signal indicating the intensity of the received light and transmits the generated electrical signal to the measuring device 5.

[0036] The measuring device 5 measures the concentration of the solute contained in the sample based on the intensity of the light received by the spectroscopic device 4. The measuring device 5 includes a timing generation circuit 51, a generation unit 52, and a concentration measurement unit 53. The timing generation circuit 51 intermittently generates a constant current and intermittently drives the LED 21 by inputting a PWM signal to the LED drive circuit 100.

[0037] The generation unit 52 generates correspondence information of the LED 21. For example, the generation unit 52 acquires the value of the forward voltage from the forward voltage measurement circuit 22 when an LED current flows from the LED drive circuit 100 to the LED 21. Further, the generation unit 52 measures the intensity of the light of a specific wavelength received by the light receiving element 42 when an LED current flows from the LED drive circuit 100 to the LED 21. When generating the correspondence information, it is assumed that no sample is flowing through the flow cell 3.

[0038] Then, the generation unit 52 generates correspondence information indicating the relationship between the value of the forward voltage of the LED 21 when current flows and the intensity of the light of a specific wavelength received by the light receiving element 42. For example, the generation unit 52 generates correspondence information associating the value of the forward voltage with the intensity of the light of a specific wavelength.

[0039] When there are a plurality of specific wavelengths used for measurement, the generation unit 52 generates correspondence information for each specific wavelength. In such a case, for example, the LED drive circuit 100 may change the value of the current applied to the LED 21 each time the spectroscopic device 4 spectrally analyzes the light of each specific wavelength and measures the intensity of the spectrally analyzed light. Further, for example, the LED drive circuit 100 may flow a current that changes from a first current value to a second current value through the LED 21 a plurality of times. In such a case, the spectroscopic device 4 spectrally analyzes the light of different specific wavelengths each time current flows and measures the change in the intensity of the spectrally analyzed light.

[0040] The concentration measurement unit 53 measures the absorbance of the sample based on the correspondence information generated by the generation unit 52, the intensity of light of a specific wavelength measured by the light receiving element 42, and the forward voltage measured by the forward voltage measurement circuit 22, and estimates the concentration of the solute from the measured absorbance. For example, for each specific wavelength, the concentration measurement unit 53 specifies, as the intensity of the emitted light, the intensity of the light associated with the forward voltage measured by the forward voltage measurement circuit 22 in the correspondence information. Subsequently, the concentration measurement unit 53 calculates the absorbance of the sample from the intensity of the light of each specific wavelength received by the LED 42 and the intensity of the specified emitted light.

[0041] Then, the measuring device 5 calculates the absorbance at a specific wavelength and measures the concentration of the solute from the calculated absorbance. In this way, the measuring device 5 pre-generates correspondence information indicating the relationship between the forward voltage of the LED 21 and the intensity of the light emitted by the LED 21 when a current is passed. Further, the measuring device 5 measures the concentration of the measurement object from the pre-measured correspondence information, the forward voltage of the LED 21, and the intensity of the light of a specific wavelength received through the measurement object.

[0042] [First Embodiment] [LED Driving Circuit] Here, the concentration measuring device 1 estimates the emission intensity of the LED 21 from the value of the forward voltage Vf of the LED 21, and calculates the concentration from the estimated emission intensity and the received intensity detected by the spectroscopic device 4. Therefore, in order to stabilize the forward voltage, the LED driving circuit 100 supplies the LED 21 with a driving current of the LED 21 with high precision and high stability. FIG. 2 is a configuration diagram of the LED driving circuit according to the first embodiment. In FIG. 2, the path connected to the forward voltage measurement circuit 22 is omitted. Hereinafter, with reference to FIG. 2, the details of the LED driving circuit 100 according to the first embodiment will be described. As shown in FIG. 2, the LED driving circuit 100 has two circuit blocks such as a constant current driving circuit 101 and a current correction circuit 102.

[0043] [Constant Current Driving Circuit] The constant current drive circuit 101 is a circuit that outputs a constant current Iout to the LED 21 by applying an input voltage Vin. The constant current drive circuit 101 is composed of a constant current control IC (Integrated Circuit) 111, a switching element Q1, an inductor L1, a freewheeling diode D1, a smoothing capacitor C1, and an output current detection element R1. As the constant current control IC 111, a general switching type LED driver IC can be used.

[0044] The constant current control IC 111 compares the output current feedback signal detected by the output current detection element R1 with a reference voltage it has. Then, the constant current control IC 111 outputs the comparison result to the switching element Q1 as a switching signal. The constant current control IC 111 controls the on and off time ratios of the switching element Q1 by the switching signal output to the switching element Q1.

[0045] Also, when a PWM signal from the timing generation circuit 51 is input to the constant current control IC 111, the LED 21 can be intermittently driven with a constant current according to the PWM signal.

[0046] The switching element Q1 receives the input of the switching signal. Then, the switching element Q1 switches on or off according to the switching signal, and supplies the input voltage Vin to the inductor L1 in the on state.

[0047] The freewheeling diode D1 is a diode for freewheeling the output current when the switching element Q1 is off.

[0048] The inductor L1 accumulates energy when Vin is applied when the switching element Q1 is on. Then, the inductor L1 releases energy when the switching element Q1 is off.

[0049] The smoothing capacitor C1 is a capacitor for smoothing the ripple component of the output current Iout.

[0050] The output current detection element R1 is a resistor for detecting the output current. The detection signal by the output current detection element R1 is compared with the internal reference voltage of the constant current control IC111, and the time ratio of on and off of the switching element Q1 is controlled. Therefore, the output current detection element R1 is set to have an appropriate constant according to the control target current value of the output current Iout.

[0051] Here, for the smoothing capacitor C1, increasing its capacitance can reduce the ripple component of the output current. However, increasing the capacitance of the smoothing capacitor C1 will increase the current rise time during intermittent driving. Conversely, if the capacitance of the smoothing capacitor C1 is too small, there is a risk of deteriorating LED21 by exceeding the allowable current value of LED21, and there is also a risk that the unevenness of the light emission intensity of LED21 will affect the measurement on the light receiving side. Therefore, the smoothing capacitor C1 is set to the minimum necessary capacitance that does not exceed the allowable current value of LED21, and the rise time is made as fast as possible. Thereby, it is possible to realize the high-speedization of the rise response of the drive current from the off state to the on state. Note that the suppression of the unevenness of the light emission intensity due to the ripple current is realized by the current correction circuit 102 described later.

[0052] Here, the accuracy of the output current Iout of the constant current drive circuit 101 does not need to be very accurate, and the output current drift due to temperature is not much of a problem either. This is due to the operation of the current correction circuit 102 described later. Therefore, an inexpensive IC that is in circulation for general lighting LEDs can be used for the constant current control IC111.

[0053] [Current correction circuit] The current correction circuit 102 is a circuit for correcting the output current Iout from the constant current drive circuit 101 to the LED 21 by bypassing a part of it by the bypass current Ibyp to an appropriate LED current Iled. The current correction circuit 102 includes an LED current detection element R10, a differential amplifier circuit 121, a reference voltage Vref, an operation amplifier 123, a bypass current control FET (Field Effect Transistor) Q10, and a current limiting resistor R15. The differential amplifier circuit 121 includes resistors R11 to R14 and an operation amplifier 122. Also, the bypass current control FET Q10 and the current limiting resistor R15 form a bypass circuit 124.

[0054] The LED current detection element R10 is a detection resistor for the LED current Iled and is set to have an appropriate constant according to the target LED current value.

[0055] The differential amplifier circuit 121 is a differential amplifier circuit that amplifies the voltage across both ends of the LED current detection element R10. If all of the resistors R11 to R14 have the same constant, the amplification factor is 1. At this time, a part of the LED current Iout flows into the differential amplifier circuit 121, but by setting the resistors R11 to R14 to a sufficiently large constant, the current flowing into the differential amplifier circuit 121 can be ignored.

[0056] The operation amplifier 123, the bypass current control FET Q10, and the current limiting resistor R15 are circuits that control the bypass current Ibyp according to the voltage difference between the output voltage from the operation amplifier 122, which is the LED current detection signal, and the reference voltage Vref. The current limiting resistor R15 is a resistor for preventing overcurrent when the bypass current control FET Q10 is short-circuited. The current limiting resistor R15 may not be provided if overcurrent is not considered.

[0057] When the LED current Iled is smaller than the target current value, the operational amplifier 123 controls in the direction of reducing the bypass current Ibyp by restricting the current flowing through the bypass current control FET Q10. Conversely, when the LED current Iled is larger than the target current value, the operational amplifier 123 controls in the direction of increasing the bypass current Ibyp by increasing the current flowing through the bypass current control FET Q10.

[0058] Also, the relational expression among the output current Iout of the constant current drive circuit, the bypass current Ibyp, and the LED current Iled can be represented by the following mathematical formula (1). Iled = Iout - Ibyp ···(1)

[0059] That is, the LED drive circuit 100 sets the control target current value of the constant current drive circuit Iout to a value slightly higher than the target current value of the LED current Iled, and consumes this difference by the bypass current Ibyp of the current correction circuit 102. Thereby, even if a ripple component is included in the output current Iout of the constant current drive circuit 101, this can be suppressed and it becomes possible to make it more direct current.

[0060] Also, the current accuracy of the LED current Iled is determined by the reference voltage Vref and component accuracy in the current correction circuit 102. Therefore, the current accuracy of the output current Iout of the constant current drive circuit 101 does not have to be very accurate, and the temperature drift of the output current Iout does not pose much of a problem either. From the above, an inexpensive IC that is in circulation for general lighting LEDs can be used for the constant current control IC 111.

[0061] Note that the frequency characteristics of the operational amplifiers 122 and 123 are desirably sufficiently good with respect to the switching frequency of the constant current control IC 111, which is the switching IC of the constant current drive circuit 101. Specifically, for example, when the switching frequency of the constant current control IC 111 is 500 kHz, it is desirable that the unity gain frequency of the operational amplifiers 122 and 123 is 5 MHz or higher.

[0062] As a result, the ripple component of the output current Iout of the constant current drive circuit 101 can be sufficiently suppressed, and the LED current Iled can be made more direct current. Also, since the current control speed of the current correction circuit 102 is sufficiently faster than the current control speed of the constant current drive circuit 101, problems such as mutual control interference will not occur. As a result, high precision and high stability of the drive current can be achieved.

[0063] Also, as described above, the control target current value of the output current Iout of the constant current drive circuit 101 is set to a value slightly higher than the target current value of the LED current Iled, but this control target current value of the output current Iout is desirably set as the minimum necessary value. As a result, the bypass current Ibyp of the current correction circuit 102 also becomes the minimum necessary value, and the heat generation of the bypass current control FET Q10 and the current limiting resistor R15 can be minimized. As a result, it becomes possible to minimize the heat generation of the components of the LED drive circuit.

[0064] [Explanation of the operation waveform] FIG. 3 is a diagram showing the operation waveforms of each part of the LED drive circuit. Also, FIG. 4 is a diagram showing an enlarged waveform of the portion corresponding to the period when the LED current is rising. FIG. 4 represents an enlarged waveform of the portion of period T1 in FIG. 3. Here, the target current value of the LED current Iled will be described as 1000 mA.

[0065] Graphs 201, 202, 201, and 211 represent the passage of time on the horizontal axis and the voltage value on the vertical axis. Graphs 201 and 211 represent the switching waveforms of the switching element Q1 by the constant current control IC 111. Vswon represents the voltage value at which the switching element Q1 is turned on. Also, graphs 202 and 212 represent the waveforms of the PWM signals input from the timing generation circuit 51 of the measuring device 5. Vpwmon represents the voltage value when the PWM signal is on.

[0066] Graphs 203 to 205 and 213 to 215 all represent the passage of time on the horizontal axis and the current value on the vertical axis. Also, graphs 203 and 213 represent the waveform of the output current Iout of the constant current drive circuit 101 and include a ripple component. Further, graphs 204 and 214 are the bypass current waveforms by the current correction circuit 102. The scale on the vertical axis of graphs 204 and 214 is set to 110 mA, which is 1 / 10 of the output current Iout. Also, graphs 205 and 215 represent the waveforms of the corrected LED current Iled obtained by subtracting the bypass current Ibyp from the output current Iout. The scale on the vertical axis of graphs 205 and 215 is the same as that of Iout.

[0067] Graphs 206 and 216 represent the passage of time on the horizontal axis and the magnitude of the voltage on the vertical axis. Also, graphs 206 and 216 are the forward voltage waveforms of the LED 21.

[0068] When the PWM signals shown in graphs 202 and 212 are input, the switching element Q1 is switched repeatedly as shown in graphs 201 and 211. As a result, an output current Iout as shown in graphs 203 and 213 is output from the constant current drive circuit 101.

[0069] Here, since the smoothing capacitor C1 has the minimum necessary capacitance, the output current Iout shown in graphs 203 and 213 includes a ripple current. Also, the current value 221 in graph 213 represents the target current value of the LED current Iled, which is 1000 mA. That is, the constant current drive circuit 101 controls the output current Iout at a control target current value slightly higher than the target current value of the LED current Iled, which is 1000 mA, as shown in graphs 203 and 213. For example, the constant current drive circuit 101 controls the control target current of the output current Iout to be approximately 1050 mA. The correction circuit 102 bypasses the amount of current exceeding 1000 mA in the output current Iout as the bypass current Ibyp, as shown in graphs 204 and 214.

[0070] As a result, as shown in graph 215, the large delay in the rise of the LED current due to the smoothing capacitor C1 is reduced, and the current value 222 in graph 215 represents the target current value of 1000 mA of the LED current Iled. That is, as shown in graphs 205 and 215, the LED current Iled becomes 1000 mA of the target current, and the ripple component is also removed. Further, as shown in graphs 206 and 216, after the current rise, the forward voltage Vf of the LED 21 is stable, and the occurrence of light emission unevenness can be suppressed. Furthermore, since the bypass current Ibyp is about 1 / 10 or less of the LED current Iled, the heat generation of the FET Q10 for bypass current control can be significantly reduced compared to a conventional linear transistor.

[0071] In the embodiment, an example where the bypass current Ibyp is about 10% is shown, but even at about 25%, the heat reduction effect can be obtained compared to the linear type. As described above, the light source device 2 according to the first embodiment can realize a high-speed and stable forward voltage Vf and light emission intensity, and the concentration measuring device 1 can also perform measurement with high accuracy and reproducibility.

[0072] [Principle of the process for improving measurement accuracy using the forward voltage] Next, the principle of the process for improving measurement accuracy using the forward voltage will be described. As described above, the measuring device 5 calculates the absorbance of the sample using the intensity of light of a specific wavelength among the light emitted by the light source device 2 and the intensity of light of a specific wavelength spectrally analyzed by the spectroscopic device 4, and estimates the concentration of the sample from the calculated absorbance. However, the light spectrum of the light emitted by the LED 21 changes according to the temperature.

[0073] For example, the intensity of the light emitted by the LED 21 decreases as the temperature of the LED 21 increases. Also, in the light emitted by the LED 21, the wavelength with the highest intensity (the peak wavelength) shifts to the longer wavelength side as the temperature of the LED 21 increases. Thus, since the intensity of the light emitted by the LED 21 changes the temperature of the light emitting element due to the ambient temperature, there is a possibility that the estimation accuracy of the concentration may decrease.

[0074] In order to correct the change in the intensity of the light emitted from the LED 21 due to such a temperature change, when the value of the current flowing through the LED 21 is changed, a larger current must be passed as the ambient temperature rises, which shortens the lifespan of the light-emitting element. Also, since the correlation between the temperature of the LED 21 itself and its surroundings (hereinafter collectively referred to as the "ambient temperature") and the intensity of the light emitted from the light-emitting element varies for each LED 21, it is necessary to measure the correlation in advance for each LED 21. However, it takes a lot of time and effort to change the ambient temperature. Furthermore, depending on the installation location of the measuring device 5, it may be difficult to change the ambient temperature.

[0075] On the other hand, the LED 21 has the characteristic that the forward voltage (Vf) when a constant current is passed varies depending on the ambient temperature. In other words, when a current (forward current) flows from the anode to the cathode of the LED 21, the voltage drops by only the forward voltage, and such a forward voltage changes depending on the ambient temperature. Also, as described above, there is a correlation between the intensity of the light emitted by the LED 21 and the ambient temperature. For this reason, there is a correlation between the intensity of the light emitted by the LED 21 and the forward voltage of the light-emitting element.

[0076] Therefore, prior to the concentration measurement, the measuring device 5 measures the forward voltage when a current is passed through the LED 21 of the light source device 2 installed in the concentration measuring device 1 while changing the current value. Then, the measuring device 5 generates correspondence information indicating the relationship between the intensity of the light of a specific wavelength emitted by the light-emitting element when a current of a predetermined current value is passed and the forward voltage measured by the measuring step when a current of a predetermined current value is passed.

[0077] Further, the measuring device 5 lights up the LED 21 included in the light source device 2, spectrally separates light of a specific wavelength from the light received through the measurement target, and measures the forward voltage of the light-emitting element. Then, the measuring device 5 measures the concentration of the measurement target based on the pre-generated correspondence information, the measured forward voltage, and the intensity of the light of the specific wavelength. For example, the measuring device 5 estimates, from the correspondence information, the intensity of the light corresponding to the measured forward voltage as the intensity of the light emitted by the LED 21. Then, the measuring device 5 measures the concentration of the measurement target based on the estimated intensity of the light and the intensity of the spectrally separated light of the specific wavelength. For example, the measuring device 5 estimates the intensity of the light of the specific wavelength emitted by the LED 21, calculates the absorbance of the measurement target based on the estimated intensity of the light and the intensity of the spectrally separated light of the specific wavelength, and then the measuring device 5 measures the concentration of the measurement target based on the calculated absorbance.

[0078] Hereinafter, returning to FIG. 1, the principle of the measurement method for estimating the concentration of the sample using the relationship between the forward voltage and the intensity of the light emitted by the light-emitting element will be described. For example, as shown in FIG. 1, the light source device 2 includes an LED 21, a forward voltage measurement circuit 22, and an LED drive circuit 100.

[0079] The LED 21 is a semiconductor element that emits light when current is supplied. For example, the LED 21 emits light including light of a wavelength at which the measurement target is likely to absorb as the specific wavelength. In the following description, the light emitted from the LED 21 may be referred to as the emitted light.

[0080] Here, for example, when the current flowing through the LED 21 is constant, there is a substantially linear correlation between the ambient temperature of the light-emitting element 21 and the forward voltage Vf such that the value of the forward voltage Vf decreases as the ambient temperature rises. As a result, when the current flowing through the LED 21 is constant, there is a substantially linear correlation between the intensity of the emitted light of the LED 21 and the forward voltage Vf such that the intensity of the emitted light increases as the value of the forward voltage Vf increases.

[0081] Thus, when estimating the intensity of light with a specific wavelength emitted by LED 21 using the correlation between the forward voltage Vf and the intensity of the emitted light, it is considered that the intensity of the light emitted by LED 21 can be estimated without previously obtaining the correlation related to the temperature of LED 21. In other words, if the correlation between the forward voltage Vf and the intensity of the emitted light can be obtained in advance, it becomes possible to estimate the intensity of the light emitted by LED 21 at the time of concentration measurement without changing the ambient temperature of LED 21.

[0082] Here, it is known that when the value of the current flowing through LED 21 is changed, the forward voltage Vf of LED 21 changes. Therefore, in the concentration measurement device 1, by changing the value of the current flowing through LED 21, the correlation between the forward voltage Vf and the intensity of the emitted light of LED 21 is obtained in advance as correspondence information. Then, in the concentration measurement device 1, using the correspondence information, the intensity of the emitted light is estimated from the forward voltage Vf of LED 21 at the time of concentration measurement, and the concentration of the measurement target is measured from the estimated intensity of the emitted light and the intensity of the light received through the measurement target.

[0083] Note that the correspondence information may be parameters measured for each LED 21 or may be commonly used by each light source device 2. However, since the characteristics of LED 21 vary from product to product, it is desirable that they be determined for each individual.

[0084] In addition, such temperature characteristics of LED 21 change not only due to the ambient temperature but also due to self-heating of LED 21 itself. Also, although LED 21 has a longer lifespan than a halogen lamp, the longer the lighting time or the larger the current flowing through it, the more it deteriorates, resulting in a decrease in the conversion efficiency from electric power to light. As a result, the light emitted when the same value of current is passed becomes dimmer. To avoid such problems, the concentration measurement device 1 measures the value of the forward voltage of LED 21 using a weak current and measures the temperature of LED 21 from the measured value of the forward voltage. That is, the concentration measurement device 1 measures the temperature of LED 21 (i.e., the diode itself) based on the same principle as a so-called diode thermometer. Note that the concentration measurement device 1 may perform processes such as gain calibration in addition to the above-described processes.

[0085] The LED driving circuit 100 applies a voltage to the LED 21 to turn it on. Also, the LED driving circuit 100 generates a plurality of different currents respectively for measuring the correlation between the forward voltage of the LED 21 and the intensity of the emitted light of the LED 21. Further, the LED driving circuit 100 generates a current for measuring the value of the forward voltage of the LED 21 during the concentration measurement.

[0086] The forward voltage measurement circuit 22 is a circuit that measures the forward voltage of the LED 21. For example, when generating the correspondence information, the forward voltage measurement circuit 22 measures the forward voltage of the LED 21 when the current generated by the LED driving circuit 100 flows through the LED 21. That is, the forward voltage measurement circuit 22 measures the change in the forward voltage of the LED 21 when a current with a changed current value flows at a predetermined resolution. Then, the forward voltage measurement circuit 22 outputs the measured value of each forward voltage to the measuring device 5.

[0087] Also, during the concentration measurement, the forward voltage measurement circuit 22 measures the forward voltage of the light emitting element 21 using the current generated by the LED driving circuit 100. For example, the forward voltage measurement circuit 22 measures the voltage of the light emitting element 21 when a current flows as the forward voltage, and outputs the measured value of the forward voltage to the measuring device 5.

[0088] Note that the value of the forward voltage output by the forward voltage measurement circuit 22 is used for predicting the intensity of the emitted light. Therefore, the accuracy of the forward voltage output by the forward voltage measurement circuit 22 contributes to the accuracy of the measured concentration. For this reason, the forward voltage measurement circuit 22 measures the forward voltage with an accuracy considering the accuracy when measuring the concentration.

[0089] For example, in order to keep the estimation accuracy of the concentration within ±0.1 percent or less, the measurement accuracy of the forward voltage needs to be suppressed to ±20 microvolts or less. In order to maintain such measurement accuracy, for example, a forward voltage of 2 volts needs to be measured with an effective resolution of 100,000 or more. Therefore, the forward voltage measurement circuit 22 outputs the voltage value of the measured forward voltage using, for example, an AD (Analog-to-Digital) converter having an effective resolution of 17 bits or more. To give a more specific example, the forward voltage measurement circuit 22 will use a ΔΣ type AD converter with a long conversion time. Note that the above example is merely an example, and for example, a forward voltage of 1 volt or less may be measured. Thus, the effective resolution changes according to how much forward voltage is measured according to what accuracy, and the measurement of the forward voltage may be performed using a circuit that realizes such effective resolution.

[0090] On the other hand, the measuring device 5 includes a timing generation circuit 51, a generation unit 52, and a concentration measurement unit 53. The timing generation circuit 51 outputs a PWM signal to the LED drive circuit 100. Thereby, light is emitted from the LED 21, and the forward voltage measurement circuit 22 measures the value of the forward voltage Vf of the LED 21 when a current flows. Further, the emitted light is transmitted to the spectroscopic device 4 via the flow cell 3, and the spectroscopic device 4 spectroscopes light of a specific wavelength.

[0091] The generation unit 52 generates correspondence information of the LED 21. For example, the generation unit 52 acquires from the forward voltage measurement circuit 22 the value of each forward voltage when different currents are respectively supplied from the LED drive circuit 100 to the LED 21. Further, in the generation unit 52, when different currents are respectively supplied from the variable current generation circuit 22 to the LED 21, the intensity of the light of a specific wavelength received by the light receiving element 42 is measured. Note that when generating the correspondence information, no sample is flowing through the flow cell 3.

[0092] Then, the generation unit 52 generates correspondence information indicating the relationship between the forward voltage value of the LED 21 when each current with a different voltage value flows and the intensity of the light with a specific wavelength received by the light receiving element 42. For example, the generation unit 52 generates correspondence information associating the forward voltage value with the intensity of the light with a specific wavelength.

[0093] When there are a plurality of specific wavelengths used for measurement, the generation unit 52 generates correspondence information for each specific wavelength. In such a case, for example, the LED drive circuit 100 may change the value of the current applied to the light emitting element each time the spectroscopic device 4 spectroscopically analyzes the light of each specific wavelength and measures the intensity of the spectroscopically analyzed light. Also, for example, the LED drive circuit 100 may flow a variable current that changes from a first current value to a second current value through the LED 21 a plurality of times. In such a case, the spectroscopic device 4 spectroscopically analyzes the light of different specific wavelengths each time the variable current flows, and measures the change in the intensity of the spectroscopically analyzed light.

[0094] The concentration measurement unit 53 measures the absorbance of the sample based on the correspondence information generated by the generation unit 52, the intensity of the light with a specific wavelength measured by the light receiving element 42, and the forward voltage measured by the forward voltage measurement circuit 22, and estimates the concentration of the solute from the measured absorbance. For example, the concentration measurement unit 53 specifies, for each specific wavelength, the intensity of the light associated with the forward voltage measured by the forward voltage measurement circuit 22 in the correspondence information as the intensity of the emitted light. Subsequently, the concentration measurement unit 53 calculates the absorbance of the sample from the intensity of the light with each specific wavelength received by the light receiving element 42 and the intensity of the specified emitted light.

[0095] Then, the measuring device 5 calculates the absorbance at a specific wavelength and measures the concentration of the solute from the calculated absorbance. For example, the measuring device 5 calculates the absorbance at each specific wavelength and calculates the concentration of the solute contained in the sample from the calculated absorbance.

[0096] In this way, the measuring device 5 pre-generates correspondence information indicating the relationship between the forward voltage of the LED 21 and the intensity of the emitted light of the light-emitting element 21. Further, the measuring device 5 measures the concentration of the measurement target from the pre-measured correspondence information, the forward voltage of the LED 21, and the intensity of the light of a specific wavelength received through the measurement target. For this reason, the measuring device 5 can easily and accurately measure the concentration of the measurement target without changing the ambient temperature of the concentration measuring device 1.

[0097] [Effect in the First Embodiment] As described above, in the LED drive circuit 100 according to the present embodiment, among the output current Iout smoothed by the smoothing capacitor C1 output from the constant current drive circuit 100, the current exceeding the control target value of the LED current Iled is made to flow as a bypass current Ibyp through the bypass path. Further, the capacitance of the smoothing capacitor C1 can be set to the minimum necessary capacitance.

[0098] Thereby, it becomes possible to suppress the delay in the rise of the LED current Iled. Also, the LED current Iled can be set to the control target value. Further, the ripple component of the LED current Iled can also be removed. After the current rises, a stable forward voltage can be supplied to the LED 21, and uneven light emission can be suppressed. Furthermore, the bypass current Ibyp can be kept low compared to the LED current, and it is possible to significantly reduce the heat generation of the bypass current control FET Q10, which is a transistor for current control. Therefore, it is possible to achieve all of high-precision and high-stability of the drive current, high-speed rise response of the drive current from the off state to the on state, and minimization of component heat generation in the LED drive circuit.

[0099] [Second Embodiment] FIG. 5 is a configuration diagram of an LED drive circuit according to the second embodiment. In FIG. 5, the path connected to the forward voltage measurement circuit 22 is omitted. In the following description, the operations of the respective parts similar to those in the first embodiment will be omitted.

[0100] [Difference from the First Embodiment] For the LED drive circuit 100 according to this embodiment, as the constant current control IC 111, a high-side current detection type IC is used. And the output current detection resistor R1 is arranged on the high voltage side, that is, inside the constant current drive circuit 101.

[0101] The constant current control IC 111 compares the detection signal from the output current detection element R1 arranged in the constant current drive circuit 101 with the internal reference voltage, and controls the on / off time ratio of the switching element Q1. For this reason, the output current detection element R1 is set to have an appropriate constant according to the control target current value of the output current Iout.

[0102] By moving the output current detection resistor R1 to the high voltage side, it is not necessary to return the current path to the constant current control IC 111 for detecting the output current. Therefore, the other end of the LED current detection resistor R10 in the current correction circuit 102 is directly connected to the circuit GND (Ground) without passing through the output current detection resistor R1 or the like.

[0103] As a result, the non-inverting input terminal of the operational amplifier 123 that controls the bypass current Ibyp can be directly connected to the LED current detection resistor R10. Therefore, it is not necessary to provide the differential amplifier circuit 121 in the current correction circuit 102 of the LED drive circuit 100 according to this embodiment. The operational amplifier 123 receives the input of the LED current Iled flowing through the LED 21, compares the LED current Iled with the reference voltage Vref, and uses the comparison result to control the bypass current control FET Q10 so that the difference between the LED current Iled and the output voltage Iout flows as the bypass current Ibyp.

[0104] [Effect in the Second Embodiment] As described above, since the LED drive circuit 100 according to this embodiment does not need to use the differential amplifier circuit 121, it is possible to eliminate the influence of variations in these component constants and temperature drift, and more accurate current control becomes possible.

[0105] [Other Embodiments] In the first and second embodiments, an example in which an LED is used as the semiconductor light-emitting element has been shown, but the present invention is not limited thereto, and for example, an LD (Laser Diode) may be used. Further, although the case of using one semiconductor light-emitting element has been described, a plurality of semiconductor light-emitting elements may be used.

[0106] In addition, although an example in which a buck-type circuit is used as the constant current control IC 111 of the constant current control circuit 101 has been shown, the constant current control IC 111 may be a boost-type circuit or a buck-boost type circuit.

[0107] Since the operating voltage of one LED 21 is about 2V, it is preferable to use a buck-type circuit for the constant current control IC 111. On the other hand, when there are a plurality of LEDs 21, a boost-type circuit may be used for the constant current control IC 111, or a buck-boost type circuit may be used in consideration of the reduction of the battery.

[0108] In the above embodiment, an example of a diode rectification type circuit using the reflux diode D1 has been shown, but this part may be replaced with a switching element such as an FET to form a synchronous rectification type. Thereby, the output efficiency of the output current Iout is further improved, and a constant current drive circuit with lower heat generation can be obtained.

[0109] [Regarding the sample] In addition, the concentration measuring device 1 may use, as a sample, not only an aqueous solution in which various solutes are dissolved but also, for example, a solution such as an organic solvent in which various solutes are dissolved. Further, in such a case, the concentration measuring device 1 may adopt an absorbance calculated from the ratio of the absorbance of the solvent and the absorbance of the solute. Further, the concentration measuring device 1 may use, as a sample, various gases such as a mixed gas, and measure the concentration of any gas among the gases contained in the sample. Further, the concentration measuring device 1 may measure the concentration of a substance serving as a solvent instead of a solute.

[0110] [Regarding the measurement] Note that, in the above example, the concentration measurement device 1 estimated the concentration of the solute dissolved in various solutions and the concentration of the gas. However, the embodiment is not limited to this. For example, the concentration measurement device 1 may determine whether a predetermined solute or gas is contained in the sample according to the above-described configuration. For example, when the absorbance at a certain wavelength exceeds a predetermined threshold, the concentration measurement device 1 may determine that the solute or gas corresponding to that wavelength is contained in the sample. That is, the measurement process executed by the concentration measurement device 1 is a concept including a process of detecting any detection target such as a solute or a gas.

[0111] [Regarding the device configuration] Note that the device configuration of the concentration measurement device 1 is not limited to the above description. For example, the light source device 2, the spectroscopic device 4, and the measurement device 5 may form an integrated measurement device.

[0112] Although an example of the embodiment has been described above, these are merely examples, and the present embodiment is not limited to the above description. Based on the knowledge of those skilled in the art, the configuration and details of the embodiment can be implemented in other forms with various modifications and improvements starting from the aspects described in the column of the disclosure of the invention. Also, each embodiment can be arbitrarily combined and implemented within a non-contradictory range.

Explanation of reference numerals

[0113] 1 Concentration measurement device 2 Light source device 3 Flow cell 4 Spectroscopic device 5 Measurement device 21 LED 22 Forward voltage measurement circuit 41 Tunable filter for Fabry - Perot spectroscopy 42 Light - receiving element 51 Timing generation circuit 52 Generation unit 53 Concentration measurement unit 100 LED drive circuit 101 Constant - current drive circuit 102 Current correction circuit IC for constant current control system Differential amplifier circuit Operational amplifiers 122 and 123 Bypass circuit Switching element Q1 FET for bypass current control Q10 Output current detection element R1 Resistor R10 for LED current detection Resistors R11 to R14 Current limiting resistor R15 Smoothing capacitor C1 Inductor L1

Claims

1. A semiconductor light-emitting element, A constant-current drive circuit that supplies a constant current to the semiconductor light-emitting element, A part of the constant current supplied from the constant-current drive circuit is sent to a bypass circuit as a bypass current, and the remaining current is supplied to the semiconductor light-emitting element as a semiconductor light-emitting element current. When the semiconductor light-emitting element current is smaller than a predetermined target current value, the bypass current is reduced. When the semiconductor light-emitting element current is larger than the predetermined target current value, a current correction circuit that corrects by increasing the bypass current A light source device characterized by comprising.

2. The constant-current drive circuit has a switching element and a switching control circuit that controls on / off of the switching element, and supplies the constant current according to the on / off operation of the switching element. The light source device according to claim 1.

3. The light source device according to claim 2, wherein the current correction circuit executes the correction operation of the bypass current at a higher speed than the on / off operation of the switching element of the switching control circuit.

4. The light source device according to claim 2 or 3, wherein the constant-current drive circuit controls the switching element based on a timing signal given from the outside to intermittently supply the constant current.

5. The light source device according to any one of claims 2 to 4, wherein the switching control circuit controls the on / off interval of the switching element based on a detection value of the constant current output from the constant-current drive circuit.

6. The light source device according to any one of claims 1 to 5, wherein the current correction circuit controls the magnitude of the bypass current based on the forward voltage of the semiconductor light-emitting element detected by a semiconductor light-emitting element current detection resistor disposed on the output side of the semiconductor light-emitting element and a reference voltage.

7. The light source device according to claim 6, wherein the current correction circuit has a differential amplifier circuit, compares the voltage value of the voltage output from the differential amplifier circuit with the reference voltage using the forward voltage as an input, and controls the magnitude of the bypass current.

8. The constant-current drive circuit has a high-side current detection circuit that detects the current value of the constant current between the input terminal of the input voltage and the semiconductor light-emitting element, and controls the constant current based on the current value detected by the high-side current detection circuit. The light source device according to claim 6, wherein the current correction circuit controls the magnitude of the bypass current based on the difference between the voltage value of the forward voltage and the voltage value of the reference voltage.

9. The light source device according to any one of claims 1 to 8, wherein the current correction circuit makes the bypass current 25% or less of the constant current.

10. A semiconductor light emitting element capable of emitting a specific wavelength corresponding to a measurement target of concentration, A constant current drive circuit that supplies a constant current to the semiconductor light emitting element, A part of the constant current supplied from the constant current drive circuit is sent to a bypass circuit as a bypass current, and the remaining current is supplied to the semiconductor light emitting element as a semiconductor light emitting element current. When the semiconductor light emitting element current is smaller than a predetermined target current value, the bypass current is reduced. When the semiconductor light emitting element current is larger than the predetermined target current value, a light source unit including a current correction circuit that corrects to increase the bypass current, A spectroscopic unit that spectroscopically analyzes the light received through the measurement target, A measurement unit that measures the forward voltage of the semiconductor light emitting element, Based on the correspondence information indicating the relationship between the forward voltage of the semiconductor light emitting element acquired in advance and the emission intensity of the light of the specific wavelength emitted by the semiconductor light emitting element, the forward voltage measured by the measurement unit, and the intensity of the light of the specific wavelength spectroscopically analyzed by the spectroscopic unit, a concentration measurement unit that measures the concentration of the measurement target A concentration measuring device, characterized by comprising.

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