WO2015065024A1 - Sensing system using positive feedback - Google Patents

Sensing system using positive feedback Download PDF

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Publication number
WO2015065024A1
WO2015065024A1 PCT/KR2014/010209 KR2014010209W WO2015065024A1 WO 2015065024 A1 WO2015065024 A1 WO 2015065024A1 KR 2014010209 W KR2014010209 W KR 2014010209W WO 2015065024 A1 WO2015065024 A1 WO 2015065024A1
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Prior art keywords
optical
medium
voltage
current
optical detector
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PCT/KR2014/010209
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French (fr)
Korean (ko)
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박영준
최성욱
이상우
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서울대학교 산학협력단
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Publication of WO2015065024A1 publication Critical patent/WO2015065024A1/en

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    • H—ELECTRICITY
    • H03—ELECTRONIC CIRCUITRY
    • H03F—AMPLIFIERS
    • H03F3/00—Amplifiers with only discharge tubes or only semiconductor devices as amplifying elements
    • H03F3/04—Amplifiers with only discharge tubes or only semiconductor devices as amplifying elements with semiconductor devices only
    • H03F3/08—Amplifiers with only discharge tubes or only semiconductor devices as amplifying elements with semiconductor devices only controlled by light
    • H03F3/087—Amplifiers with only discharge tubes or only semiconductor devices as amplifying elements with semiconductor devices only controlled by light with IC amplifier blocks
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01D—MEASURING NOT SPECIALLY ADAPTED FOR A SPECIFIC VARIABLE; ARRANGEMENTS FOR MEASURING TWO OR MORE VARIABLES NOT COVERED IN A SINGLE OTHER SUBCLASS; TARIFF METERING APPARATUS; MEASURING OR TESTING NOT OTHERWISE PROVIDED FOR
    • G01D21/00—Measuring or testing not otherwise provided for
    • G—PHYSICS
    • G06—COMPUTING; CALCULATING OR COUNTING
    • G06F—ELECTRIC DIGITAL DATA PROCESSING
    • G06F3/00—Input arrangements for transferring data to be processed into a form capable of being handled by the computer; Output arrangements for transferring data from processing unit to output unit, e.g. interface arrangements
    • G06F3/01—Input arrangements or combined input and output arrangements for interaction between user and computer
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01K—MEASURING TEMPERATURE; MEASURING QUANTITY OF HEAT; THERMALLY-SENSITIVE ELEMENTS NOT OTHERWISE PROVIDED FOR
    • G01K11/00—Measuring temperature based upon physical or chemical changes not covered by groups G01K3/00, G01K5/00, G01K7/00 or G01K9/00
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01M—TESTING STATIC OR DYNAMIC BALANCE OF MACHINES OR STRUCTURES; TESTING OF STRUCTURES OR APPARATUS, NOT OTHERWISE PROVIDED FOR
    • G01M11/00—Testing of optical apparatus; Testing structures by optical methods not otherwise provided for
    • G01M11/02—Testing optical properties
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N15/00—Investigating characteristics of particles; Investigating permeability, pore-volume or surface-area of porous materials
    • G01N15/06—Investigating concentration of particle suspensions
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N27/00—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N29/00—Investigating or analysing materials by the use of ultrasonic, sonic or infrasonic waves; Visualisation of the interior of objects by transmitting ultrasonic or sonic waves through the object
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N9/00—Investigating density or specific gravity of materials; Analysing materials by determining density or specific gravity
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N9/00—Investigating density or specific gravity of materials; Analysing materials by determining density or specific gravity
    • G01N9/36—Analysing materials by measuring the density or specific gravity, e.g. determining quantity of moisture

Definitions

  • the present invention relates to a sensing system using positive feedback.
  • a sensing system using a conventional actuator and a sensor maintains a constant magnitude of an input signal generated from the actuator, so that the sensor detects a change in a medium formed by the actuator.
  • Sensing systems according to the prior art form actuators, media and sensors in a single stage, or form a sensing system in the form of negative feedback for a more stable configuration.
  • the turbidity sensor when the actuator irradiates a constant light to a medium containing a material to measure the concentration, the sensor senses the light transmitted through the medium, and converts the light into an electrical signal to determine the material contained in the medium. The concentration was measured.
  • LOD limit of detection
  • the present invention is to solve the problems of the sensing system according to the prior art described above, and to provide a sensing system that can detect with a higher sensitivity even if a smaller amount of substances are included with improved detection limit characteristics of the present invention.
  • the sensing system includes an optical actuator for applying an optical stimulus to a detection material; A non-photo detector for outputting an electrical signal having a snapback shape corresponding to the non-optical response formed according to the nature of the medium to which the optical stimulus is applied; An amplifier amplifying the electrical signal output by the non-optical detector and applying positive feedback to the optical actuator by applying positive feedback to the optical actuator; And an output unit configured to receive the electrical signal and detect the property of the medium.
  • the sensing system includes an optical actuator for applying an optical stimulus to the medium; A non-optical detector to which a bias current is applied and to which a non-optical response of the medium is input; And a positive feedback unit that increases the optical stimulus of the optical actuator as the bias current increases.
  • the sensing system according to the present embodiment provides an advantage of detecting a substance to be detected at a concentration low enough to be detected by a conventional sensor.
  • FIG. 1 is a block diagram showing an overview of a sensing system according to an embodiment of the present invention.
  • FIG. 2 is a circuit diagram illustrating an example in which an optical detector is used in the sensing system of FIG. 1.
  • FIG. 3 is a circuit diagram illustrating an example in which a non-optical detector is used in the sensing system of FIG. 1.
  • BSA Bovine Serum Albumin
  • FIG. 5 is a diagram illustrating a measurement result of current-voltage characteristics according to concentrations of materials included in a medium in a snapback period.
  • FIG. 6A is a diagram illustrating a result of BSA measurement measured by a sensor according to the prior art
  • FIG. 6B is a diagram of a result of BSA measurement measured according to an embodiment
  • 6C is a diagram summarizing the BSA detection capability of the sensing system according to an embodiment.
  • FIG. 7A to 7C are current-voltage characteristic curves of NADH measured using 270, 280, and 340 nm LEDs
  • FIG. 7D is a diagram illustrating NADH measurement capability of a sensing system according to an exemplary embodiment.
  • FIG. 9A to 9C are current-voltage curves obtained by measuring turbidity using 880 nm, 405 nm, and 280 nm infrared LEDs, respectively.
  • FIG. 9D is a diagram illustrating measurement limits using a sensing system according to an exemplary embodiment. .
  • FIG. 1 is a block diagram illustrating an overview of a sensing system according to an embodiment of the present invention.
  • FIG. 2 is a circuit diagram illustrating an example in which an optical detector is used in the sensing system of FIG. 1.
  • 3 is a circuit diagram illustrating an example in which a non-optical detector is used in the sensing system of FIG. 1.
  • the sensing system includes an optical actuator 100.
  • the optical actuator 100 applies an optical stimulus to the medium 200.
  • an actuator providing ultraviolet light, visible light, infrared light, and laser light is defined as an optical actuator.
  • the optical actuator 100 may be implemented as a light emitting diode (LED) that provides light, a laser diode (LD), or the like.
  • the light emitting diode may emit light in the visible, ultraviolet or infrared wavelength band
  • the laser diode may emit laser light having a specific band among the 270 nm to 3330 nm bands. It is preferable to provide the optical actuator 100 to irradiate light having a suitable band according to the property of the medium 200 to be detected by the sensing system.
  • the sensing system includes a medium 200.
  • the medium 200A receives an optical stimulus from the optical actuator 100 to form an optical response.
  • the degree of optical response of the medium 200A may vary depending on the properties of the medium.
  • the properties of the medium include, for example, the concentration of certain substances contained in the medium, the temperature of the medium, the refractive index of the medium, the turbidity of the medium, the density of the medium, and the like.
  • the material included in the medium 200A receives an optical stimulus from the optical actuator 100 to form an optical response.
  • BSA Bovine Serum Albumin
  • BSA Bovine Serum Albumin
  • the medium 200B receives an optical stimulus from the optical actuator 100 to form a non-optical response.
  • the degree of non-optical response of the medium 200B may vary depending on the properties of the medium.
  • the properties of the medium include, for example, the concentration of certain substances contained in the medium, the temperature of the medium, the refractive index of the medium, the turbidity of the medium, the density of the medium, and the like.
  • the medium 200B may be, for example, an inorganic material (eg, polyethylene terephtarate), and receives an optical stimulus from the optical actuator 100 to form an ultrasonic wave that is a non-optical response.
  • the optical actuator 100, the medium 200B and the non-optical detector 300B operate in a manner similar to photoacuostic spectroscopy.
  • the sensing system includes a detector 300.
  • the detector 300 may be an optical detector 300A, and the optical detector 300A detects an optical response generated by applying an optical stimulus to the medium 200A and outputs an electrical signal.
  • the optical response may vary according to the nature of the medium 200A, and accordingly, an electrical signal provided by the optical detector 300A may also vary.
  • an optical detector 300A may be implemented as a photo diode, and the photodiode detects a change in light due to an optical response generated by the medium 200A and provides a corresponding current.
  • the optical detector 300A may receive the driving current i pd from a PD bias providing a bias current, and the sensing system sweeps the driving current provided by the PD bias. While detecting the optical response provided by the medium (200A). As will be described later, as the driving current changes, the optical detector 300A outputs an electrical signal having a snapback shape.
  • the detector 300 may be a non-photo detector 300B, and the non-photo detector 300B may detect a non-optical response generated by applying an optical stimulus to the medium 200B, and may detect the non-optical response as an electrical signal.
  • Output The non-optical response may vary depending on the nature of the medium 200B, and thus the electrical signal provided by the non-optical detector 300B may also vary.
  • the non-optical detector 300B may be implemented using a piezo-electric converter 310B, first and second diodes 320B and 330B, and a low pass filter 340B.
  • the piezo-electric converter 310B provides an alternating current that corresponds to the change of the ultrasonic wave due to the non-optical reaction in which the medium 200B occurs.
  • the first diode 320B half-wave rectifies the alternating current generated by the piezo-electric converter 310B into a direct current.
  • the driving current i pd supplied from the power source PD bias is passed to the second diode 330B.
  • the non-optical detector 300B may receive the driving current i pd from a PD bias providing a bias current, and the sensing system sweeps the driving current provided by the PD bias. While detecting the non-optical response provided by medium 200B. As will be described later, as the driving current changes, the non-optical detector 300B outputs an electrical signal having a snapback shape.
  • the amplifier 400 amplifies and outputs an electrical signal provided by the detector 300, and the amplified electrical signal is fed back to the actuator 100.
  • the actuator 100, the medium 200, the detector 300, and the amplifier 400 form a positive feedback path.
  • the amplifier 400 may provide positive feedback so that the intensity of the optical stimulus provided by the actuator 100 increases.
  • the amplifier 400 increases the forward voltage of the LED included in the optical actuator 100 as the bias current (PD bias) provided by the power source increases.
  • the amplifier 400 may be implemented as a current-to-voltage converter (iv converter) that converts the current provided by the detector 300 into a voltage signal form, and the output voltage of the current-voltage converter circuit is positively fed back.
  • the current i pd provided by the detector 300 is converted into a voltage signal v fb by the amplifier 400. Since the voltage signal v fb has a negative potential, the potential of the other end connected to the amplifier 400 is lower than the potential of one end of the actuator 100 to which the reference potential is connected. Accordingly, as the voltage v fb of the amplifier increases, the bias applied to the actuator 100 increases, thereby applying a larger stimulus, whereby the medium 200 responds optically or non-optically to the applied stimulus.
  • the detector 300 which detects an optical or non-optical response, provides a larger current i pd . That is, it can be seen that the sensing system according to the present embodiment is configured with a positive feedback path.
  • the output unit 500 receives the electrical signal output from the detector 300 and analyzes the electrical signal to detect the property of the medium 200.
  • the output unit 500 includes a read-out circuit to detect the property of the medium 200 by analyzing the electrical signal OUTPUT provided by the detector 300.
  • the vertical axis is a value of a bias current (PD bias, i pd ) applied to the optical detector 300A of FIGS. 1 and 2, and the horizontal axis is a voltage value v pd formed across the optical detector 300A.
  • PD bias, i pd bias current
  • the amplifier 400 turns on the optical actuator 100 by applying a voltage higher than the turn-on voltage to the optical actuator 100.
  • the turned on optical actuator 100 applies an optical stimulus to the medium 200A, and when the medium 200A provides light in an optical response, the optical detector 300A detects such light and changes it into a current to output the light. do.
  • the voltage across the optical detector 300A to compensate for the current caused by the light emitted by the medium 200A by the optical reaction. Should be reduced.
  • the voltage moves in a decreasing direction. That is, even if the power source increases the current value applied to the optical detector, the voltage applied across the optical detector 300A has a characteristic of decreasing negative resistance.
  • the phenomenon in which the voltage across the optical detector 300A decreases as the current applied to the optical detector 300A increases is called a snapback phenomenon, and a starting point at which the snapback phenomenon occurs is a snapback point (SB point) or snapback.
  • the section in which the voltage decreases even though the current increases due to the phenomenon is called a snapback section.
  • Increasing the bias current of the optical detector 300A further reduces the voltage across the optical detector to near zero. This is called a saturation point (SAT point, saturation point), and after the saturation point is called a saturation interval.
  • Saturation provides light to the optical detector 300A with light due to more optical response in a medium that is more optically stimulated as a result of the positive feedback as a result of the bias current of the optical detector 300A increasing. Is found to occur because the voltage across it must be reduced to compensate for the current formed by the increased light, and as the bias current continues to increase, the voltage across the optical detector 300A remains near this point. Increasing the current, there is almost no change in voltage. However, as shown in FIG. 4, the voltage may increase by several V. However, referring to FIG. 5 in which the voltage across the photodetector 300A is extended to about 100 V, the voltage change with respect to the current change amount in the saturation period is illustrated. You can see that it is insignificant.
  • FIG. 5 is a graph illustrating measurement results of current-voltage characteristics for each concentration of a material included in a medium 200A in a snapback section, and each of 1ng, 10ng, BSA in deionized water (DI).
  • I a current-voltage curve obtained by the detection system according to the present embodiment for a medium to which 1 mg is added.
  • a current of approximately 2.1 ⁇ A to 2.15 ⁇ A is applied to the optical detector 300, a snapback phenomenon occurs, and it can be seen that the voltage is saturated to approximately 0V at a current of 2.17 ⁇ A to 2.21 ⁇ A.
  • the output unit 500 fixes the optical detector 300A bias current and reads the voltage across the optical detector 300A, or fixes the voltage across the optical detector 300A, and then adjusts the value of the optical detector 300A bias current.
  • the concentration of the substance can be determined by reading.
  • the output unit 500 may fix the bias current of the optical detector 300A to 2.15 ⁇ A, and then, when the voltage across the optical detector 300A is read at 66 V, the concentration of the material may be determined as 1 ng.
  • the output unit 500 may fix the voltage across the optical detector 300A to 40V, and then determine the concentration of the material as 100ng when the optical detector 300A bias current is read as 2.18 ⁇ A.
  • the concentration of the substance may be measured by measuring current and voltage values at the saturation point through the snapback period.
  • the sensing system shown in FIG. 2 including the optical detector 300A detects an optical response, and the sensing system shown in FIG. 3 only detects a non-optical response.
  • the sensing system of FIGS. 100) in common with positive feedback. Since the sensing system including the non-optical detector 300B also has a positive feedback structure, it has a current-voltage characteristic similar to the graphs shown in FIGS. 4 and 5, and also has a snapback characteristic. Therefore, the current-voltage characteristic of the sensing system including the non-optical detector 300B is omitted for convenience of description.
  • FIG. 2 is a circuit diagram of a sensing system implementation according to the present embodiment, wherein a power source for applying a bias current to an optical detector is Agilent's Model 4156, and an optical detector is an ultraviolet enhanced photodiode of Advanced Photonix. (UV Enhanced Silicon Photodiode) Model 100-13-23-222 was used, and the op amp used Burr Brown's high voltage, high current operational amplifier OPA544.
  • the feedback resistor included in the amplifier is 6.1Mohm.
  • the optical actuator uses an LED that emits light of a different wavelength for each target material to be measured.
  • BSA detection capability is summarized as shown in Figure 6c. As shown in Figure 6c, according to the sensing system according to this embodiment it can be seen that can measure the BSA protein having a concentration of 10 ⁇ 10 3 pM that could not be measured by the sensor according to the prior art.
  • NADH Nicotinamide Adenine Dinucleotide
  • NADH has a maximum absorption wavelength of 260 nm, which is the same as DNA because nucleotides are the basic skeleton. Since the wavelength of 340 nm absorbs only NADH well, the activity of dehydratase can be measured using a 340 nm LED. In the present experimental example, NADH was measured using 270, 280, and 340 nm LEDs, and the current-voltage characteristics for the wavelengths were as shown in FIGS. 7A, 7B, and 7C, respectively. In addition, based on the above measurement results NADH measurement capability is summarized as shown in Figure 7d. As shown in Figure 7d, using the sensing system according to this embodiment it was confirmed that the NADH up to 10nM can be measured.
  • Turbidity was measured using 880 nm, 405 nm, and 280 nm infrared LEDs, respectively, in order to check whether the suspended matter in water could be detected.
  • 9A, 9B, and 9C are enlarged views of snapback sections for respective wavelengths
  • FIG. 9D is a diagram illustrating measurement limits using a sensing system according to an exemplary embodiment. As shown in Figure 9a it can be seen that the measurement can be measured to the most accurate and low concentration in the 880nm wavelength band. Examining the detection limits based on the above measurement results, it can be seen that up to 0.01 NTU can be detected as shown in FIG. 9D.

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Abstract

According to the present embodiment, a sensing system comprises: an optical actuator for applying optical stimulation to a sensing material; a non-photo detector for outputting a snapback-type electrical signal corresponding to a non-photo reaction formed depending on the characteristics of a medium to which the optical stimulation is applied; an amplifier for amplifying the electrical signal output by the non-photo detector and for applying the amplified electrical signal to the optical actuator by employing positive feedback; and an output unit for receiving the electrical signal and detecting the characteristics of the medium.

Description

포지티브 피드백을 이용한 센싱 시스템Sensing System with Positive Feedback
본 발명은 포지티브 피드백을 이용한 센싱 시스템에 관한 것이다.The present invention relates to a sensing system using positive feedback.
종래 액츄에이터(actuator)와 센서(sensor)를 사용하는 센싱 시스템은 액츄에이터에서 발생하는 입력 신호의 크기를 일정하게 유지하여, 센서는 액추에이터에 의하여 형성되는 매질의 변화를 검출하였다. 종래 기술에 의한 센싱 시스템은 액츄에이터, 매질 및 센서를 단일단으로 형성하거나, 또는 보다 안정적인 구성을 위하여 네거티브 피드백(negative feedback) 형태로 센싱 시스템을 형성하였다.A sensing system using a conventional actuator and a sensor maintains a constant magnitude of an input signal generated from the actuator, so that the sensor detects a change in a medium formed by the actuator. Sensing systems according to the prior art form actuators, media and sensors in a single stage, or form a sensing system in the form of negative feedback for a more stable configuration.
일 예로, 탁도 센서의 경우 농도를 측정하고자 하는 물질을 포함하는 매질에 액츄에이터가 일정한 광을 조사하면, 센서는 매질을 투과한 광을 센싱하고, 광을 전기적 신호로 변환하여 매질에 포함된 물질의 농도를 측정하였다.For example, in the case of a turbidity sensor, when the actuator irradiates a constant light to a medium containing a material to measure the concentration, the sensor senses the light transmitted through the medium, and converts the light into an electrical signal to determine the material contained in the medium. The concentration was measured.
종래의 센싱 시스템은 제한된 검출한계(LOD, Limit Of Detection)를 가진다. 일 예로, 수질 센서로 사용되는 경우에 센싱 시스템의 검출한계 특성이 높아 물에 검출하고자 하는 물질이 검출한계 이하로 미량 포함된 경우에도 해당 물질이 포함되지 않은 것으로 파악할 수 밖에 없었다.Conventional sensing systems have a limit of detection (LOD). For example, when the sensor is used as a water quality sensor, the detection limit characteristic of the sensing system is high, and even if a small amount of the substance to be detected is below the detection limit, it was inevitable that the substance was not included.
본 발명은 상술한 종래 기술에 의한 센싱 시스템의 문제점을 해소하기 위한 것으로, 보다 향상된 검출 한계 특성을 가져서 보다 미량의 물질이 포함되어도 보다 높은 민감도로 검출할 수 있는 센싱 시스템을 제공하는 것이 본 발명의 목적 중 하나이다.The present invention is to solve the problems of the sensing system according to the prior art described above, and to provide a sensing system that can detect with a higher sensitivity even if a smaller amount of substances are included with improved detection limit characteristics of the present invention. One of the purposes.
본 실시예에 따른 센싱 시스템은 검출 물질에 광학적 자극을 인가하는 광학적 액츄에이터(optical actuator); 상기 광학적 자극이 인가된 매질의 성질에 따라 형성되는 비광학적 반응에 상응하여 스냅백(snapback) 형태를 가지는 전기적 신호를 출력하는 비광학적 검출기(non-photo detector); 상기 비광학적 검출기가 출력하는 상기 전기적 신호를 증폭하고, 증폭된 상기 전기적 신호를 상기 광학적 액츄에이터에 포지티브 피드백(positive feedback)하여 인가하는 증폭기(amplifier); 및 상기 전기적 신호를 인가받아 상기 매질의 상기 성질을 검출하는 출력부를 포함한다.The sensing system according to the present embodiment includes an optical actuator for applying an optical stimulus to a detection material; A non-photo detector for outputting an electrical signal having a snapback shape corresponding to the non-optical response formed according to the nature of the medium to which the optical stimulus is applied; An amplifier amplifying the electrical signal output by the non-optical detector and applying positive feedback to the optical actuator by applying positive feedback to the optical actuator; And an output unit configured to receive the electrical signal and detect the property of the medium.
또한, 본 실시예에 따른 센싱 시스템은 매질에 광학적 자극을 인가하는 광학적 액츄에이터; 바이어스 전류가 인가되며, 상기 매질의 비광학적 반응이 입력되는 비광학적 검출기; 및 상기 바이어스 전류가 증가함에 따라 상기 광학적 액츄에이터의 상기 광학적 자극을 증가시키는 포지티브 피드백 유닛을 포함한다. In addition, the sensing system according to the present embodiment includes an optical actuator for applying an optical stimulus to the medium; A non-optical detector to which a bias current is applied and to which a non-optical response of the medium is input; And a positive feedback unit that increases the optical stimulus of the optical actuator as the bias current increases.
본 실시예에 의한 센싱 시스템에 의하면 종래의 센서로 검출할 수 없었던 정도로 낮은 농도의 검출 대상 물질을 검출할 수 있다는 장점이 제공된다. The sensing system according to the present embodiment provides an advantage of detecting a substance to be detected at a concentration low enough to be detected by a conventional sensor.
도 1은 본 발명의 일 실시예에 의한 센싱 시스템의 개요를 도시한 블록도(block diagram)이다. 1 is a block diagram showing an overview of a sensing system according to an embodiment of the present invention.
도 2는 도 1의 센싱 시스템에 있어서, 광학적 검출기가 사용된 일례를 나타내는 회로도이다. FIG. 2 is a circuit diagram illustrating an example in which an optical detector is used in the sensing system of FIG. 1.
도 3은 도 1의 센싱 시스템에 있어서, 비광학적 검출기가 사용된 일례를 나타내는 회로도이다. 3 is a circuit diagram illustrating an example in which a non-optical detector is used in the sensing system of FIG. 1.
도 4는 일 실시예에 의한 센싱 시스템으로 매질에 포함된 물질인 BSA(Bovine Serum Albumin)을 검출할 때 광학적 검출기가 출력하는 전기적 신호의 전류-전압 특성 곡선이다. 4 is a current-voltage characteristic curve of an electrical signal output by an optical detector when detecting a BSA (Bovine Serum Albumin), which is a material included in a medium, using a sensing system according to an embodiment.
도 5는 스냅백 구간에서 매질에 포함된 물질의 농도별 전류-전압 특성의 측정 결과를 도시한 도면이다. FIG. 5 is a diagram illustrating a measurement result of current-voltage characteristics according to concentrations of materials included in a medium in a snapback period.
도 6a는 종래 기술에 따른 센서로 측정한 BSA 측정의 결과값을 도시한 도면이고, 도 6b는 일 실시예로 측정한 BSA 측정의 결과값을 도시한 도면이다. 도 6c는 일 실시예에 의한 센싱 시스템의 BSA 검출 능력을 정리한 도면이다.FIG. 6A is a diagram illustrating a result of BSA measurement measured by a sensor according to the prior art, and FIG. 6B is a diagram of a result of BSA measurement measured according to an embodiment. 6C is a diagram summarizing the BSA detection capability of the sensing system according to an embodiment.
도 7a 내지 도 7c는 270, 280, 340nm LED를 사용하여 NADH를 측정한 전류-전압 특성곡선이며, 도 7d는 일 실시예에 의한 센싱 시스템의 NADH측정 능력을 도시한 도면이다.7A to 7C are current-voltage characteristic curves of NADH measured using 270, 280, and 340 nm LEDs, and FIG. 7D is a diagram illustrating NADH measurement capability of a sensing system according to an exemplary embodiment.
도 8은 그라핀 산화물(Graphene Oxide)의 농도를 측정한 결과에 대한 전류-전압 특성 곡선이다.8 is a current-voltage characteristic curve for the result of measuring the concentration of graphene oxide (Graphene Oxide).
도 9a 내지 도 9c는 880nm, 405nm, 280nm 적외선 LED를 각각 사용하여 탁도(turbidity)를 측정하여 얻은 전류-전압 곡선이며, 도 9d는 일 실시예에 따른 센싱 시스템을 이용한 측정 한계를 도시한 도면이다.9A to 9C are current-voltage curves obtained by measuring turbidity using 880 nm, 405 nm, and 280 nm infrared LEDs, respectively. FIG. 9D is a diagram illustrating measurement limits using a sensing system according to an exemplary embodiment. .
본 발명에 관한 설명은 구조적 내지 기능적 설명을 위한 실시예에 불과하므로, 본 발명의 권리범위는 본문에 설명된 실시예에 의하여 제한되는 것으로 해석되어서는 아니 된다. 즉, 실시예는 다양한 변경이 가능하고 여러 가지 형태를 가질 수 있으므로 본 발명의 권리범위는 기술적 사상을 실현할 수 있는 균등물들을 포함하는 것으로 이해되어야 한다.Description of the present invention is only an embodiment for structural or functional description, the scope of the present invention should not be construed as limited by the embodiments described in the text. That is, since the embodiments may be variously modified and may have various forms, the scope of the present invention should be understood to include equivalents capable of realizing the technical idea.
한편, 본 출원에서 서술되는 용어의 의미는 다음과 같이 이해되어야 할 것이다.On the other hand, the meaning of the terms described in the present application should be understood as follows.
단수의 표현은 문맥상 명백하게 다르게 뜻하지 않는 한 복수의 표현을 포함하는 것으로 이해되어야 하고, "포함하다" 또는 "가지다" 등의 용어는 설시된 특징, 숫자, 단계, 동작, 구성요소, 부분품 또는 이들을 조합한 것이 존재함을 지정하려는 것이지, 하나 또는 그 이상의 다른 특징들이나 숫자, 단계, 동작, 구성요소, 부분품 또는 이들을 조합한 것들의 존재 또는 부가 가능성을 미리 배제하지 않는 것으로 이해되어야 한다.Singular expressions should be understood to include plural expressions unless the context clearly indicates otherwise, and terms such as "include" or "have" refer to features, numbers, steps, operations, components, parts, or parts thereof described. It is to be understood that the combination is intended to be present, but not to exclude in advance the possibility of the presence or addition of one or more other features or numbers, steps, operations, components, parts or combinations thereof.
본 개시의 실시예들을 설명하기 위하여 참조되는 도면은 설명의 편의 및 이해의 용이를 위하여 의도적으로 크기, 높이, 두께 등이 과장되어 표현되어 있으며, 비율에 따라 확대 또는 축소된 것이 아니다. 또한, 도면에 도시된 어느 구성요소는 의도적으로 축소되어 표현하고, 다른 구성요소는 의도적으로 확대되어 표현될 수 있다.The drawings referred to for describing the embodiments of the present disclosure are intentionally exaggerated in size, height, thickness, etc. for ease of explanation and easy understanding, and are not to be enlarged or reduced in proportion. In addition, any component illustrated in the drawings may be intentionally reduced in size, and other components may be intentionally enlarged in size.
여기서 사용되는 모든 용어들은 다르게 정의되지 않는 한, 본 발명이 속하는 분야에서 통상의 지식을 가진 자에 의해 일반적으로 이해되는 것과 동일한 의미를 가진다. 일반적으로 사용되는 사전에 정의되어 있는 것과 같은 용어들은 관련 기술의 문맥상 가지는 의미와 일치하는 것으로 해석되어야 하며, 본 출원에서 명백하게 정의하지 않는 한 이상적이거나 과도하게 형식적인 의미를 지니는 것으로 해석될 수 없다.All terms used herein have the same meaning as commonly understood by one of ordinary skill in the art unless otherwise defined. Terms such as those defined in the commonly used dictionaries should be construed to be consistent with the meanings in the context of the related art and should not be construed as having ideal or overly formal meanings unless expressly defined in this application. .
이하에서는 첨부된 도면을 참조하여 본 발명의 실시예를 설명한다. 도 1은 본 발명의 실시예에 의한 센싱 시스템의 개요를 도시한 블록도(block diagram)이다. 도 2는 도 1의 센싱 시스템에 있어서, 광학적 검출기가 사용된 일례를 나타내는 회로도이다. 도 3은 도 1의 센싱 시스템에 있어서, 비광학적 검출기가 사용된 일례를 나타내는 회로도이다. Hereinafter, with reference to the accompanying drawings will be described an embodiment of the present invention. 1 is a block diagram illustrating an overview of a sensing system according to an embodiment of the present invention. FIG. 2 is a circuit diagram illustrating an example in which an optical detector is used in the sensing system of FIG. 1. 3 is a circuit diagram illustrating an example in which a non-optical detector is used in the sensing system of FIG. 1.
도 1 내지 도 3을 참조하면, 센싱 시스템은 광학적 액추에이터(100)를 포함한다. 광학적 액추에이터(100)는 매질(200)에 광학적 자극을 인가한다. 이하에서는 자외광, 가시광, 적외광 및 레이저 광을 제공하는 액추에이터를 광학적 액추에이터라고 정의한다. 일 예로, 광학적 액추에이터(100)는 광을 제공하는 발광 다이오드(LED, Light Emitting Diode), 레이저 다이오드(LD, Laser Diode) 등으로 구현될 수 있다. 발광 다이오드는 가시광, 자외광 또는 적외광 파장 대역의 광을 조사할 수 있으며, 레이저 다이오드는 270nm 내지 3330nm 대역 중 특정 대역을 가지는 레이저 광을 조사할 수 있다. 센싱 시스템으로 검출하고자 하는 매질(200)의 성질(property)에 따라 적합한 대역을 가지는 광을 조사하도록 광학적 액추에이터(100)를 구비하는 것이 바람직하다.1 to 3, the sensing system includes an optical actuator 100. The optical actuator 100 applies an optical stimulus to the medium 200. Hereinafter, an actuator providing ultraviolet light, visible light, infrared light, and laser light is defined as an optical actuator. For example, the optical actuator 100 may be implemented as a light emitting diode (LED) that provides light, a laser diode (LD), or the like. The light emitting diode may emit light in the visible, ultraviolet or infrared wavelength band, and the laser diode may emit laser light having a specific band among the 270 nm to 3330 nm bands. It is preferable to provide the optical actuator 100 to irradiate light having a suitable band according to the property of the medium 200 to be detected by the sensing system.
센싱 시스템은 매질(200)을 포함한다. 일 예로, 매질(200A)은 광학적 액추에이터(100)로부터 광학적 자극을 인가받아 광학적 반응을 형성한다. 예로서 매질(200A)의 광학적 반응의 정도는 매질의 성질(property)에 따라 변경될 수 있다. 매질의 성질은 예로서 매질에 포함된 소정 물질의 농도, 매질의 온도, 매질의 굴절율, 매질의 탁도 및 매질의 밀도 등을 포함한다. 예로서, 매질(200A)에 포함된 물질은 광학적 액추에이터(100)로부터 광학적 자극을 인가받아 광학적 반응을 형성한다. 일 예로, BSA(Bovine Serum Albumin)는 270~280nm의 광을 흡수하는 특징을 가진다. 따라서 BSA를 포함하는 매질에 275nm 파장을 가지는 레이저를 조사하면 BSA는 인가된 광학적 자극에 대하여 인가된 광을 흡수하는 광학적 반응을 한다. The sensing system includes a medium 200. For example, the medium 200A receives an optical stimulus from the optical actuator 100 to form an optical response. By way of example, the degree of optical response of the medium 200A may vary depending on the properties of the medium. The properties of the medium include, for example, the concentration of certain substances contained in the medium, the temperature of the medium, the refractive index of the medium, the turbidity of the medium, the density of the medium, and the like. For example, the material included in the medium 200A receives an optical stimulus from the optical actuator 100 to form an optical response. For example, BSA (Bovine Serum Albumin) has a feature of absorbing light of 270 ~ 280nm. Therefore, when a laser having a wavelength of 275 nm is irradiated to a medium including BSA, the BSA reacts to the applied optical stimulus to absorb the applied light.
다른 예로, 매질(200B)은 광학적 액추에이터(100)로부터 광학적 자극을 인가받아 비광학적 반응을 형성한다. 예로서 매질(200B)의 비광학적 반응의 정도는 매질의 성질(property)에 따라 변경될 수 있다. 매질의 성질은 예로서 매질에 포함된 소정 물질의 농도, 매질의 온도, 매질의 굴절율, 매질의 탁도 및 매질의 밀도 등을 포함한다. 예로서, 매질(200B)은 일례로 무기물(예: polyethylene terephtarate)일 수 있으며, 광학적 액추에이터(100)로부터 광학적 자극을 인가받아 비광학적 반응인 초음파를 형성한다. 이 경우, 광학적 액추에이터(100), 매질(200B) 및 비광학적 검출기(300B)는 광음향 분광법(photoacuostic spectroscopy)와 유사한 방식으로 동작한다. As another example, the medium 200B receives an optical stimulus from the optical actuator 100 to form a non-optical response. By way of example, the degree of non-optical response of the medium 200B may vary depending on the properties of the medium. The properties of the medium include, for example, the concentration of certain substances contained in the medium, the temperature of the medium, the refractive index of the medium, the turbidity of the medium, the density of the medium, and the like. For example, the medium 200B may be, for example, an inorganic material (eg, polyethylene terephtarate), and receives an optical stimulus from the optical actuator 100 to form an ultrasonic wave that is a non-optical response. In this case, the optical actuator 100, the medium 200B and the non-optical detector 300B operate in a manner similar to photoacuostic spectroscopy.
센싱 시스템은 검출기(300)를 포함한다. 일례로 검출기(300)는 광학적 검출기(photo detector, 300A)일 수 있으며, 광학적 검출기(300A)는 매질(200A)에 광학적 자극이 인가되어 발생하는 광학적 반응을 검출하여 전기적 신호로 출력한다. 매질(200A)의 성질에 따라 광학적 반응이 달라질 수 있으며, 그에 따라 광학적 검출기(300A)가 제공하는 전기적 신호도 달라질 수 있다. The sensing system includes a detector 300. For example, the detector 300 may be an optical detector 300A, and the optical detector 300A detects an optical response generated by applying an optical stimulus to the medium 200A and outputs an electrical signal. The optical response may vary according to the nature of the medium 200A, and accordingly, an electrical signal provided by the optical detector 300A may also vary.
일 예로, 포토 다이오드(photo diode)로 광학적 검출기(300A)를 구현할 수 있으며, 포토 다이오드는 매질(200A)이 발생하는 광학적 반응으로 인한 광의 변화를 검출하고, 그에 상응하는 전류를 제공한다. 일 예로, 광학적 검출기(300A)는 바이어스 전류를 제공하는 전원(PD bias)로부터 구동 전류(ipd)를 제공받을 수 있으며, 센싱 시스템은 전원(PD bias)이 제공하는 구동 전류를 변화(sweep)시키면서 매질(200A)이 제공하는 광학적 반응을 검출한다. 후술할 바와 같이, 구동 전류가 변화함에 따라 광학적 검출기(300A)는 스냅백 형태를 가지는 전기적 신호를 출력한다.For example, an optical detector 300A may be implemented as a photo diode, and the photodiode detects a change in light due to an optical response generated by the medium 200A and provides a corresponding current. For example, the optical detector 300A may receive the driving current i pd from a PD bias providing a bias current, and the sensing system sweeps the driving current provided by the PD bias. While detecting the optical response provided by the medium (200A). As will be described later, as the driving current changes, the optical detector 300A outputs an electrical signal having a snapback shape.
다른 예로 검출기(300)는 비광학적 검출기(non-photo detector, 300B)일 수 있으며, 비광학적 검출기(300B)는 매질(200B)에 광학적 자극이 인가되어 발생하는 비광학적 반응을 검출하여 전기적 신호로 출력한다. 매질(200B)의 성질에 따라 비광학적 반응이 달라질 수 있으며, 그에 따라 비광학적 검출기(300B)가 제공하는 전기적 신호도 달라질 수 있다. As another example, the detector 300 may be a non-photo detector 300B, and the non-photo detector 300B may detect a non-optical response generated by applying an optical stimulus to the medium 200B, and may detect the non-optical response as an electrical signal. Output The non-optical response may vary depending on the nature of the medium 200B, and thus the electrical signal provided by the non-optical detector 300B may also vary.
일 예로, 피에조-일렉트릭 변환기(310B), 제1 및 제2 다이오드들(320B, 330B) 및 저대역 통과 필터(low pass filter, 340B)로 비광학적 검출기(300B)를 구현할 수 있다. 피에조-일렉트릭 변환기(310B)는 매질(200B)이 발생하는 비광학적 반응으로 인한 초음파의 변화에 대응하는 교류 전류를 제공한다. 제1 다이오드(320B)는 피에조-일렉트릭 변환기(310B)에서 생성된 교류 전류를 직류 전류로 반파 정류한다. 제2 다이오드(330B)로는 전원(PD bias)로부터 제공되는 구동 전류(ipd)가 지나간다. 피에조-일렉트릭 변환기(310B)가 전류를 생성하면, 구동 전류(ipd)에서 생성된 전류만큼 줄어든 전류가 제2 다이오드(330B)로 지나간다. 저대역 통과 필터(340B)는 제2 다이오드(330B)의 양단(N3, N4) 사이의 전압에서 고대역 성분을 제거한다. 일 예로, 비광학적 검출기(300B)는 바이어스 전류를 제공하는 전원(PD bias)로부터 구동 전류(ipd)를 제공받을 수 있으며, 센싱 시스템은 전원(PD bias)이 제공하는 구동 전류를 변화(sweep)시키면서 매질(200B)이 제공하는 비광학적 반응을 검출한다. 후술할 바와 같이, 구동 전류가 변화함에 따라 비광학적 검출기(300B)는 스냅백 형태를 가지는 전기적 신호를 출력한다.For example, the non-optical detector 300B may be implemented using a piezo-electric converter 310B, first and second diodes 320B and 330B, and a low pass filter 340B. The piezo-electric converter 310B provides an alternating current that corresponds to the change of the ultrasonic wave due to the non-optical reaction in which the medium 200B occurs. The first diode 320B half-wave rectifies the alternating current generated by the piezo-electric converter 310B into a direct current. The driving current i pd supplied from the power source PD bias is passed to the second diode 330B. When the piezo-electric converter 310B generates a current, a current reduced by the current generated by the driving current i pd passes to the second diode 330B. The low pass filter 340B removes the high band component from the voltage between the two ends N3 and N4 of the second diode 330B. For example, the non-optical detector 300B may receive the driving current i pd from a PD bias providing a bias current, and the sensing system sweeps the driving current provided by the PD bias. While detecting the non-optical response provided by medium 200B. As will be described later, as the driving current changes, the non-optical detector 300B outputs an electrical signal having a snapback shape.
증폭기(400)는 검출기(300)가 제공한 전기적 신호를 증폭하여 출력하며, 증폭된 전기적 신호는 액추에이터(100)로 피드백된다. 따라서, 액추에이터(100), 매질(200), 검출기(300) 및 증폭기(400)는 포지티브 피드백 경로(positive feedback path)를 형성한다. 일례로 검출기(300)가 제공하는 전류가 증가할수록 액추에이터(100)에서 제공하는 광학적 자극의 세기가 증가하도록 증폭기(400)가 포지티브 피드백을 제공할 수 있다. 예로서, 증폭기(400)는 전원이 제공하는 바이어스 전류(PD bias)가 증가함에 따라 광학적 액츄에이터(100)에 포함된 LED의 순방향 전압을 증가시킨다. The amplifier 400 amplifies and outputs an electrical signal provided by the detector 300, and the amplified electrical signal is fed back to the actuator 100. Thus, the actuator 100, the medium 200, the detector 300, and the amplifier 400 form a positive feedback path. For example, as the current provided by the detector 300 increases, the amplifier 400 may provide positive feedback so that the intensity of the optical stimulus provided by the actuator 100 increases. For example, the amplifier 400 increases the forward voltage of the LED included in the optical actuator 100 as the bias current (PD bias) provided by the power source increases.
일 예로, 증폭기(400)는 검출기(300)가 제공한 전류를 전압 신호 형태로 변환하는 전류-전압 컨버터(i-v converter)로 구현할 수 있으며, 전류-전압 컨버터 회로의 출력 전압은 포지티브 피드백된다. 검출기(300)가 제공하는 전류(ipd)는 증폭기(400)에 의하여 전압 신호(vfb)로 변환된다. 전압 신호(vfb)는 음전위를 가지므로, 기준 전위가 연결된 액추에이터(100)의 일단의 전위에 비하여 증폭기(400)와 연결된 타단의 전위가 더 낮아진다. 따라서, 증폭기의 전압(vfb)이 증가함에 따라 액추에이터(100)에 인가되는 바이어스는 커지므로 더 큰 자극을 인가하고, 그에 따라 매질(200)은 인가된 자극에 대하여 광학적 또는 비광학적으로 반응하며, 광학적 또는 비광학적 반응을 검출한 검출기(300)는 더 큰 전류(ipd)를 제공한다. 즉, 본 실시예에 의한 센싱 시스템은 포지티브 피드백 경로로 구성되어 있음을 알 수 있다. For example, the amplifier 400 may be implemented as a current-to-voltage converter (iv converter) that converts the current provided by the detector 300 into a voltage signal form, and the output voltage of the current-voltage converter circuit is positively fed back. The current i pd provided by the detector 300 is converted into a voltage signal v fb by the amplifier 400. Since the voltage signal v fb has a negative potential, the potential of the other end connected to the amplifier 400 is lower than the potential of one end of the actuator 100 to which the reference potential is connected. Accordingly, as the voltage v fb of the amplifier increases, the bias applied to the actuator 100 increases, thereby applying a larger stimulus, whereby the medium 200 responds optically or non-optically to the applied stimulus. The detector 300, which detects an optical or non-optical response, provides a larger current i pd . That is, it can be seen that the sensing system according to the present embodiment is configured with a positive feedback path.
출력부(500)는 검출기(300)가 출력한 전기적 신호를 제공받아 전기적 신호를 분석하여 매질(200)의 성질을 검출한다. 일 실시예로, 출력부(500)는 리드-아웃 회로를 구비하여 검출기(300)가 제공하는 전기적 신호(OUTPUT)를 분석하여 매질(200)의 성질을 검출한다.The output unit 500 receives the electrical signal output from the detector 300 and analyzes the electrical signal to detect the property of the medium 200. In one embodiment, the output unit 500 includes a read-out circuit to detect the property of the medium 200 by analyzing the electrical signal OUTPUT provided by the detector 300.
도 4는 본 실시예에 의한 센싱 시스템으로 매질(200A)에 포함된 물질인 BSA(Bovine Serum Albumin)을 검출할 때 광학적 검출기(300A)가 출력하는 전기적 신호의 전류-전압 특성 곡선이다. 수직축은 도 1 및 도 2의 광학적 검출기(300A)에 인가되는 바이어스 전류(PD bias, ipd)의 값이며, 수평축은 광학적 검출기(300A) 양단에 형성되는 전압값(vpd)이다. 4 is a current-voltage characteristic curve of an electrical signal output by the optical detector 300A when detecting a BSA (Bovine Serum Albumin), which is a material included in the medium 200A, by the sensing system according to the present embodiment. The vertical axis is a value of a bias current (PD bias, i pd ) applied to the optical detector 300A of FIGS. 1 and 2, and the horizontal axis is a voltage value v pd formed across the optical detector 300A.
도 1, 2 및 4를 참조하여 광학적 검출기(300A)에 제공되는 바이어스 전류를 0에서 증가시키면서 광학적 검출기(300A) 양단의 전압의 변화를 설명하도록 한다. 광학적 검출기(300A)에 제공되는 바이어스 전류(ipd)를 증가시키면 광학적 검출기(300A) 양단에 형성되는 전압(vpd)도 그에 상응하여 증가하며, 아직 광학적 액추에이터(100)는 턴 온(turn on)되지 않는다. 1, 2, and 4, the variation of the voltage across the optical detector 300A will be described while increasing the bias current provided to the optical detector 300A from zero. Increasing the bias current i pd provided to the optical detector 300A increases the voltage v pd formed across the optical detector 300A correspondingly, and yet the optical actuator 100 is turned on. Not)
광학적 검출기(300A)에 인가되는 전류가 증가함에 따라 증폭기(400)가 광학적 액추에이터(100)에 턴 온 전압 이상의 전압을 인가하여 광학적 액추에이터(100)를 턴 온 시킨다. 턴 온된 광학적 액추에이터(100)는 매질(200A)에 광학적 자극을 인가하며, 매질(200A)이 광학적 반응으로 광을 제공하는 경우에, 광학적 검출기(300A)는 이러한 광을 검출하여 전류로 변화하여 출력한다. 광학적 액추에이터(100)가 턴 온되는 시점에서, 광학적 검출기(300)가 일정한 전류를 흘리기 위해서는 광학적 반응에 의하여 매질(200A)이 발광하는 광에 의한 전류를 보상하기 위해 광학적 검출기(300A) 양단의 전압이 줄어들어야 한다. 따라서 전압은 감소하는 방향으로 이동한다. 즉, 전원이 광학적 검출기에 인가하는 전류값을 증가시켜도 광학적 검출기(300A) 양단에 인가되는 전압은 오히려 감소하는 음 저항(negative resistance)의 특징을 가진다. As the current applied to the optical detector 300A increases, the amplifier 400 turns on the optical actuator 100 by applying a voltage higher than the turn-on voltage to the optical actuator 100. The turned on optical actuator 100 applies an optical stimulus to the medium 200A, and when the medium 200A provides light in an optical response, the optical detector 300A detects such light and changes it into a current to output the light. do. At the time when the optical actuator 100 is turned on, in order for the optical detector 300 to flow a constant current, the voltage across the optical detector 300A to compensate for the current caused by the light emitted by the medium 200A by the optical reaction. Should be reduced. Thus, the voltage moves in a decreasing direction. That is, even if the power source increases the current value applied to the optical detector, the voltage applied across the optical detector 300A has a characteristic of decreasing negative resistance.
이와 같이 광학적 검출기(300A)로 인가되는 전류가 증가함에 따라 광학적 검출기(300A) 양단 전압이 감소하는 현상을 스냅백 현상이라 하고, 스냅백 현상이 일어나는 시작점을 스냅백 포인트(SB point), 스냅백 현상에 의하여 전류가 증가하여도 전압이 감소하는 구간을 스냅백 구간이라고 한다. The phenomenon in which the voltage across the optical detector 300A decreases as the current applied to the optical detector 300A increases is called a snapback phenomenon, and a starting point at which the snapback phenomenon occurs is a snapback point (SB point) or snapback. The section in which the voltage decreases even though the current increases due to the phenomenon is called a snapback section.
광학적 검출기(300A)의 바이어스 전류를 더욱 증가시키면 광학적 검출기 양단의 전압이 0에 근접하는 정도로 감소한다. 이때를 포화 포인트(SAT point, saturation point)이라 하고, 포화 포인트 이후를 포화 구간이라 한다. Increasing the bias current of the optical detector 300A further reduces the voltage across the optical detector to near zero. This is called a saturation point (SAT point, saturation point), and after the saturation point is called a saturation interval.
포화는 광학적 검출기(300A)의 바이어스 전류가 증가함에 따라 포지티브 피드백에 의하여 결과적으로 더 큰 광학적 자극을 받은 매질이 더 많은 광학적 반응에 의한 광을 광학적 검출기(300A)에 제공하는데, 광학적 검출기(300A)는 증가한 광에 의하여 형성되는 전류를 보상하기 위하여 그 양단 전압을 감소시켜야 하기 때문에 발생하는 것으로 파악되며, 계속적으로 바이어스 전류를 증가시킴에 따라 광학적 검출기(300A) 양단의 전압은 이 지점 부근에서 유지 되고, 전류를 올려도 전압의 변화가 거의 없다. 다만, 도 4에서 도시된 바와 같이 전압이 수 V 정도로 상승할 수 있으나, 광 검출(300A)기 양단 전압을 대략 100V 정도로 확장하여 도시한 도 5를 참조하면, 포화 구간에서 전류 변화량에 대한 전압 변화는 미미한 것을 확인할 수 있다.Saturation provides light to the optical detector 300A with light due to more optical response in a medium that is more optically stimulated as a result of the positive feedback as a result of the bias current of the optical detector 300A increasing. Is found to occur because the voltage across it must be reduced to compensate for the current formed by the increased light, and as the bias current continues to increase, the voltage across the optical detector 300A remains near this point. Increasing the current, there is almost no change in voltage. However, as shown in FIG. 4, the voltage may increase by several V. However, referring to FIG. 5 in which the voltage across the photodetector 300A is extended to about 100 V, the voltage change with respect to the current change amount in the saturation period is illustrated. You can see that it is insignificant.
또한, 도 4에서 점선으로 도시된 곡선은 포지티브 피드백 경로없이 개방 루프로 신호 경로가 이루어진 상태에서 얻어진 전류-전압 특성 곡선이다. 점선으로 도시된 곡선과 대비하여 보면, 광학적 액추에이터(100), 매질(200A), 광학적 검출기(300A) 및 증폭기(400)가 포지티브 피드백 하도록 연결되어 있어 스냅백 특성을 보이는 것을 확인할 수 있다.4 is a current-voltage characteristic curve obtained with a signal path in an open loop without a positive feedback path. In contrast to the curve shown by the dotted line, it can be seen that the optical actuator 100, the medium 200A, the optical detector 300A, and the amplifier 400 are connected to the positive feedback to show the snapback characteristics.
도 5는 스냅백 구간에서 매질(200A)에 포함된 물질의 농도별 전류-전압 특성의 측정 결과를 도시한 도면으로, 탈이온수(DeIonized water, DI)에 BSA를 각각 1ng, 10ng, ..., 1mg을 첨가한 매질에 대하여 본 실시예에 의한 센싱 시스템으로 검출하여 얻은 전류-전압 곡선이다. 도시된 바와 같이, 광학적 검출기(300)에 대략 2.1μA 내지 2.15μA의 전류를 인가하면 스냅백 현상이 발생하고, 2.17μA 내지 2.21μA의 전류에서 대략 0V의 전압으로 포화되는 것을 확인할 수 있다. FIG. 5 is a graph illustrating measurement results of current-voltage characteristics for each concentration of a material included in a medium 200A in a snapback section, and each of 1ng, 10ng, BSA in deionized water (DI). , Is a current-voltage curve obtained by the detection system according to the present embodiment for a medium to which 1 mg is added. As shown, when a current of approximately 2.1μA to 2.15μA is applied to the optical detector 300, a snapback phenomenon occurs, and it can be seen that the voltage is saturated to approximately 0V at a current of 2.17μA to 2.21μA.
매질(200A)에 포함된 물질의 농도에 따라 스냅백 구간에서의 전류 전압 특성이 변화하는 것을 알 수 있다. 따라서, 출력부(500)는 광학적 검출기(300A) 바이어스 전류를 고정하고 광학적 검출기(300A) 양단 전압을 읽거나, 광학적 검출기(300A) 양단 전압을 고정한 후, 광학적 검출기(300A) 바이어스 전류의 값을 읽어서 물질의 농도를 파악할 수 있다. 일 예로, 출력부(500)는 광학적 검출기(300A) 바이어스 전류를 2.15μA로 고정한 후, 광학적 검출기(300A) 양단의 전압이 66V로 읽히면 물질의 농도를 1ng으로 파악할 수 있다. 다른 예로, 출력부(500)는 광학적 검출기(300A) 양단 전압을 40V로 고정한 후, 광학적 검출기(300A) 바이어스 전류가 2.18μA로 읽히면 물질의 농도를 100ng으로 파악할 수 있다. 또한, 스냅백 구간을 지나 포화 포인트에서의 전류, 전압값을 측정하여 물질의 농도를 측정할 수도 있다.It can be seen that the current voltage characteristics in the snapback period change according to the concentration of the material contained in the medium 200A. Therefore, the output unit 500 fixes the optical detector 300A bias current and reads the voltage across the optical detector 300A, or fixes the voltage across the optical detector 300A, and then adjusts the value of the optical detector 300A bias current. The concentration of the substance can be determined by reading. For example, the output unit 500 may fix the bias current of the optical detector 300A to 2.15 μA, and then, when the voltage across the optical detector 300A is read at 66 V, the concentration of the material may be determined as 1 ng. As another example, the output unit 500 may fix the voltage across the optical detector 300A to 40V, and then determine the concentration of the material as 100ng when the optical detector 300A bias current is read as 2.18μA. In addition, the concentration of the substance may be measured by measuring current and voltage values at the saturation point through the snapback period.
도 4 및 5와 이에 대한 발명의 상세한 설명은 광학적 검출기(300A)를 포함한 도 2에 도시된 센싱 시스템의 전류-전압 특성을 설명하고 있다. 도 2에 도시된 센싱 시스템은 광학적 반응을 검출하고, 도 3에 도시된 센싱 시스템은 비광학적 반응을 검출할 따름으로, 도 2 및 3의 센싱 시스템은 검출기(300)가 제공하는 신호를 액추에이터(100)로 포지티브 피드백한다는 공통점을 가진다. 비광학적 검출기(300B)를 포함한 센싱 시스템도 포지티브 피드백 구조를 가지므로, 도 4 및 5에 표현된 그래프와 유사한 전류-전압 특성을 가지며, 스냅백 특성도 가진다. 따라서, 비광학적 검출기(300B)를 포함한 센싱 시스템의 전류-전압 특성은 설명의 편의를 위하여 생략한다. 4 and 5 and the detailed description of the invention describe the current-voltage characteristics of the sensing system shown in FIG. 2 including the optical detector 300A. The sensing system shown in FIG. 2 detects an optical response, and the sensing system shown in FIG. 3 only detects a non-optical response. Thus, the sensing system of FIGS. 100) in common with positive feedback. Since the sensing system including the non-optical detector 300B also has a positive feedback structure, it has a current-voltage characteristic similar to the graphs shown in FIGS. 4 and 5, and also has a snapback characteristic. Therefore, the current-voltage characteristic of the sensing system including the non-optical detector 300B is omitted for convenience of description.
구현예 및 실험결과Embodiment and Experiment Results
이하에서는, 일 실시예에 의한 센싱 시스템의 구현예와 구현예를 이용하여 매질에 포함된 물질을 검출한 결과를 설명하도록 한다. 도 2는 본 실시예에 의한 센싱 시스템 구현예의 회로도로, 광학적 검출기에 바이어스 전류를 인가하는 전원은 애질런트사(Agilent)의 모델 4156이며, 광학적 검출기로는 어드밴스드 포토닉스(Advanced Photonix) 사의 자외선 증강 포토 다이오드(UV Enhanced Silicon Photodiode) 모델 100-13-23-222를 사용하였고, 연산 증폭기는 버브라운(Burr Brown)사의 고전압 고전류용 연산 증폭기 OPA544를 사용하였다. 증폭기에 포함된 피드백 저항은 6.1Mohm 이다. 광학적 액추에이터는 측정하고자 하는 검출 대상 물질별로 상이한 파장의 광을 방출하는 LED를 사용하였다. Hereinafter, a result of detecting a material included in a medium by using an embodiment and implementation of a sensing system according to an embodiment will be described. 2 is a circuit diagram of a sensing system implementation according to the present embodiment, wherein a power source for applying a bias current to an optical detector is Agilent's Model 4156, and an optical detector is an ultraviolet enhanced photodiode of Advanced Photonix. (UV Enhanced Silicon Photodiode) Model 100-13-23-222 was used, and the op amp used Burr Brown's high voltage, high current operational amplifier OPA544. The feedback resistor included in the amplifier is 6.1Mohm. The optical actuator uses an LED that emits light of a different wavelength for each target material to be measured.
물 속의 단백질 검출 가능성을 테스트하기 위하여 10pM에서 100uM까지의 서로 다른 농도를 가지는 BSA를 측정하였다. 종래 기술에 따른 센서로 측정한 결과값은 도 6a와 같으며, 본 실시예로 측정한 결과 값은 도 6b와 같다. 위에서 설명한 바와 같이 포지티브 피드백에 의하여 스냅백 현상이 발생하는 것을 확인할 수 있다. 또한, 위 측정 결과를 토대로 BSA 검출 능력을 정리하면 도 6c과 같다. 도 6c에서 도시된 바와 같이, 본 실시예에 의한 센싱 시스템에 의하면 종래 기술에 의한 센서로 측정할 수 없었던 10~103pM 농도를 가지는 BSA 단백질을 측정할 수 있음을 확인할 수 있다.To test the detectability of proteins in water, BSAs with different concentrations ranging from 10 pM to 100 uM were measured. The result measured by the sensor according to the prior art is shown in Figure 6a, the result measured in this embodiment is shown in Figure 6b. As described above, it can be seen that a snapback phenomenon occurs due to positive feedback. In addition, based on the above measurement results BSA detection capability is summarized as shown in Figure 6c. As shown in Figure 6c, according to the sensing system according to this embodiment it can be seen that can measure the BSA protein having a concentration of 10 ~ 10 3 pM that could not be measured by the sensor according to the prior art.
수중 미생물의 존재를 검출하기 위하여 NADH의 농도를 측정하였다. Nicotinamide Adenine Dinucleotide (NAD)는 세포에서 발견되는 중요한 조효소로, NADH는 NAD의 환원 형태이고, 세포 대사 과정에서 아래와 같은 반응 식을 따라 발생하는 물질이다.The concentration of NADH was measured to detect the presence of microorganisms in water. Nicotinamide Adenine Dinucleotide (NAD) is an important coenzyme found in cells. NADH is a reduced form of NAD, and it occurs in the cell metabolism according to the following equation.
NAD+ + 환원 물질 (2e- + 2H+ ) ⇔ NADH + H+ + 산화물질NAD + + reducing substance (2e- + 2H +) ⇔ NADH + H + + oxide
따라서 NADH의 존재 여부를 측정하면 물 속의 미생물이 존재하는지 확인할 수 있다. NADH는 뉴클레오타이드가 기본 골격이기 때문에 흡수 극대파장이 260nm로 DNA와 같다. 340nm의 파장은 NADH만이 잘 흡수하기 때문에, 탈수조효소의 활성도를 340nm LED를 사용하여 측정할 수 있다. 본 실험예에서는 NADH를 270, 280, 340nm LED를 사용하여 측정하였고, 각각 파장에 대한 전류-전압 특성은 각각 도 7a, 7b 및 7c와 같다. 또한, 위 측정 결과를 토대로 NADH측정 능력을 정리하면 도 7d와 같다. 도 7d에 도시된 바와 같이, 본 실시예에 의한 센싱 시스템을 이용하면 10nM까지의 NADH를 측정할 수 있음을 확인하였다.Therefore, measuring the presence of NADH can determine whether the presence of microorganisms in the water. NADH has a maximum absorption wavelength of 260 nm, which is the same as DNA because nucleotides are the basic skeleton. Since the wavelength of 340 nm absorbs only NADH well, the activity of dehydratase can be measured using a 340 nm LED. In the present experimental example, NADH was measured using 270, 280, and 340 nm LEDs, and the current-voltage characteristics for the wavelengths were as shown in FIGS. 7A, 7B, and 7C, respectively. In addition, based on the above measurement results NADH measurement capability is summarized as shown in Figure 7d. As shown in Figure 7d, using the sensing system according to this embodiment it was confirmed that the NADH up to 10nM can be measured.
수중 독성 물질 중 하나인 그라핀 산화물(Graphene Oxide)의 농도를 측정하였으며, 그 측정 결과에 대한 전류-전압 특성 곡선은 도 8과 같다. 도 8에서 확인할 수 있는 바와 같이 4ng/ml 농도까지 검출이 가능함을 알 수 있으며, 종래의 기술에 의한 스펙트로미터(spectrometer)를 사용하면 수 ug/ml대의 농도를 측정할 수 있는 바, 본 실시예에 의한 센싱 시스템의 성능이 우월함을 확인할 수 있다.The concentration of graphene oxide (Graphene Oxide), one of the toxic substances in water, was measured, and the current-voltage characteristic curve of the measurement result is shown in FIG. 8. As can be seen in Figure 8 it can be seen that it can be detected up to 4ng / ml concentration, using a spectrometer according to the prior art (spectrometer) can measure the concentration of several ug / ml bar, this embodiment It can be seen that the performance of the sensing system is superior.
물 속 부유물을 검출할 수 있는지 확인하기 위하여 880nm, 405nm, 280nm 적외선 LED를 각각 사용하여 탁도(turbidity)를 측정하였다. 도 9a, 도 9b 및 도 9c는 각 파장별 스냅백 구간을 확대하여 도시한 도면이며, 도 9d는 일 실시예에 따른 센싱 시스템을 이용한 측정 한계를 도시한 도면이다. 도 9a에 도시된 바와 같이 880nm 파장대에서 가장 정밀하고 낮은 농도까지 측정을 할 수 있음을 확인할 수 있다. 위의 측정 결과를 토대로 검출 한계를 검토하면 도 9d에 도시된 바와 같이 0.01NTU까지 검출할 수 있는 것을 확인할 수 있다.Turbidity was measured using 880 nm, 405 nm, and 280 nm infrared LEDs, respectively, in order to check whether the suspended matter in water could be detected. 9A, 9B, and 9C are enlarged views of snapback sections for respective wavelengths, and FIG. 9D is a diagram illustrating measurement limits using a sensing system according to an exemplary embodiment. As shown in Figure 9a it can be seen that the measurement can be measured to the most accurate and low concentration in the 880nm wavelength band. Examining the detection limits based on the above measurement results, it can be seen that up to 0.01 NTU can be detected as shown in FIG. 9D.
본 발명에 대한 이해를 돕기 위하여 도면에 도시된 실시 예를 참고로 설명되었으나, 이는 실시를 위한 실시예로, 예시적인 것에 불과하며, 당해 분야에서 통상적 지식을 가진 자라면 이로부터 다양한 변형 및 균등한 타 실시 예가 가능하다는 점을 이해할 것이다. 따라서, 본 발명의 진정한 기술적 보호범위는 첨부된 특허청구범위에 의해 정해져야 할 것이다. Although described with reference to the embodiments shown in the drawings to aid the understanding of the present invention, this is an embodiment for the implementation, it is merely exemplary, those skilled in the art from various modifications and equivalents therefrom It will be appreciated that other embodiments are possible. Therefore, the true technical protection scope of the present invention will be defined by the appended claims.
[부호의 설명] [Description of the code]
100: 액츄에이터 200: 매질100: actuator 200: medium
300: 검출기 400: 증폭기300: detector 400: amplifier
500: 출력부500: output unit

Claims (20)

  1. 센싱 시스템에 있어서, In the sensing system,
    검출 물질에 광학적 자극을 인가하는 광학적 액츄에이터(optical actuator);An optical actuator for applying an optical stimulus to the detection material;
    상기 광학적 자극이 인가된 매질의 성질에 따라 형성되는 비광학적 반응에 상응하여 스냅백(snapback) 형태를 가지는 전기적 신호를 출력하는 비광학적 검출기(non-photo detector); A non-photo detector for outputting an electrical signal having a snapback shape corresponding to the non-optical response formed according to the nature of the medium to which the optical stimulus is applied;
    상기 비광학적 검출기가 출력하는 상기 전기적 신호를 증폭하고, 증폭된 상기 전기적 신호를 상기 광학적 액츄에이터에 포지티브 피드백(positive feedback)하여 인가하는 증폭기(amplifier); 및An amplifier amplifying the electrical signal output by the non-optical detector and applying positive feedback to the optical actuator by applying positive feedback to the optical actuator; And
    상기 전기적 신호를 인가받아 상기 매질의 상기 성질을 검출하는 출력부를 포함하는 센싱 시스템.And an output unit configured to receive the electrical signal and detect the property of the medium.
  2. 제1항에 있어서, The method of claim 1,
    상기 센싱 시스템은 상기 비광학적 검출기에 바이어스 전류를 인가하는 전원을 더 포함하는 센싱 시스템.The sensing system further comprises a power source for applying a bias current to the non-optical detector.
  3. 제1항에 있어서, The method of claim 1,
    상기 광학적 액추에이터는 발광 다이오드(LED, Light Emitting Diode), 레이저 다이오드(LD, Laser Diode) 중 적어도 어느 하나를 포함하는 센싱 시스템.The optical actuator includes at least one of a light emitting diode (LED) and a laser diode (LD).
  4. 제1항에 있어서, The method of claim 1,
    상기 비광학적 검출기는 음파, 초음파, 전기장 및 자기장 중 어느 하나를 검출하는 센싱 시스템.The non-optical detector detects any one of a sound wave, an ultrasonic wave, an electric field, and a magnetic field.
  5. 제1항에 있어서, The method of claim 1,
    상기 비광학적 검출기는 상기 광학적 액츄에이터가 인가한 상기 자극이 상기 매질에 인가되어 형성된 상기 비광학적 반응을 검출하여 그에 상응하는 상기 전기적 신호를 출력하는 센싱 시스템. And the non-optical detector detects the non-optical response formed by applying the stimulus applied by the optical actuator to the medium and outputs the corresponding electrical signal.
  6. 제1항에 있어서, The method of claim 1,
    상기 증폭기는 전류 신호를 인가받아 그에 상응하는 전압 신호로 변환하여 출력하는 전류-전압 변환 증폭기인 센싱 시스템.And the amplifier is a current-voltage conversion amplifier that receives a current signal and converts it into a corresponding voltage signal.
  7. 제1항에 있어서, The method of claim 1,
    상기 스냅백 형태를 가지는 전기적 신호는, The electrical signal having the snapback form,
    스냅백 포인트(smapback point)으로부터 상기 비광학적 검출기 양단 전압이 증가함에 따라 상기 전기적 신호가 감소하는 스냅백 구간과, 상기 비광학적 검출기 양단 전압이 증가함에 따라 상기 전기적 신호가 증가하는 포화 구간을 포함하며, 상기 스냅백 구간과 상기 포화 구간은 포화 포인트(saturation point)를 거쳐 연결되는 센싱 시스템. A snapback section in which the electrical signal decreases as the voltage across the non-optical detector increases from a snapback point, and a saturation section in which the electrical signal increases as the voltage across the non-optical detector increases. And the snapback section and the saturation section are connected via a saturation point.
  8. 제7항에 있어서, The method of claim 7, wherein
    상기 출력부는, The output unit,
    상기 스냅백 구간에서 상기 비광학적 검출기에 일정한 전류가 제공될 때 상기 비광학적 검출기의 양단 전압을 검출하여 상기 매질의 상기 성질을 검출하는 센싱 시스템.And a sensing current of the medium by detecting a voltage across the non-optical detector when a constant current is provided to the non-optical detector in the snapback period.
  9. 제7항에 있어서,The method of claim 7, wherein
    상기 출력부는, The output unit,
    상기 스냅백 구간에서 상기 비광학적 검출기에 일정한 전압이 제공될 때 상기 비광학적 검출기로 흐르는 전류를 검출하여 상기 매질의 상기 성질을 검출하는 센싱 시스템.And sensing the current of the medium by detecting a current flowing to the non-optical detector when a constant voltage is provided to the non-optical detector in the snapback period.
  10. 제7항에 있어서,The method of claim 7, wherein
    상기 출력부는, The output unit,
    상기 포화 포인트에서의 전류, 전압값을 검출하여 상기 매질의 상기 성질을 검출하는 센싱 시스템.And a sensing system for detecting the current and voltage values at the saturation point to detect the property of the medium.
  11. 제7항에 있어서,The method of claim 7, wherein
    상기 출력부는, The output unit,
    상기 포화 구간의 전류, 전압의 비를 검출하여 상기 매질의 상기 성질을 검출하는 센싱 시스템.Sensing system for detecting the property of the medium by detecting the ratio of the current, voltage of the saturation period.
  12. 제1항에 있어서, The method of claim 1,
    상기 매질의 상기 성질은 상기 매질에 포함된 소정 물질의 농도, 상기 매질의 온도, 상기 매질의 굴절율, 상기 매질의 탁도 및 상기 매질의 밀도 중 적어도 어느 하나를 포함하는 센싱 시스템.Wherein said property of said medium comprises at least one of a concentration of a predetermined material contained in said medium, a temperature of said medium, a refractive index of said medium, a haze of said medium, and a density of said medium.
  13. 매질에 광학적 자극을 인가하는 광학적 액츄에이터;An optical actuator for applying an optical stimulus to the medium;
    바이어스 전류가 인가되며, 상기 매질의 비광학적 반응이 입력되는 비광학적 검출기; 및A non-optical detector to which a bias current is applied and to which a non-optical response of the medium is input; And
    상기 바이어스 전류가 증가함에 따라 상기 광학적 액츄에이터의 상기 광학적 자극을 증가시키는 포지티브 피드백 유닛을 포함하는 센싱 시스템. And a positive feedback unit that increases the optical stimulus of the optical actuator as the bias current increases.
  14. 제13항에 있어서, The method of claim 13,
    상기 광학적 액츄에이터는 발광 다이오드(LED, Light Emitting Diode) 및 레이저 다이오드(LD, Laser Diode) 중 적어도 어느 하나를 포함하며, 상기 비광학적 검출기는 음파, 초음파, 전기장 및 자기장 중 적어도 어느 하나를 검출하는 센싱 시스템.The optical actuator includes at least one of a light emitting diode (LED) and a laser diode (LD), and the non-optical detector detects at least one of a sound wave, an ultrasonic wave, an electric field, and a magnetic field. system.
  15. 제13항에 있어서, The method of claim 13,
    상기 포지티브 피드백 유닛은 상기 바이어스 전류가 증가함에 따라 상기 광학적 액츄에이터가 인가하는 상기 광학적 자극의 세기를 증가시키는 센싱 시스템. And the positive feedback unit increases the intensity of the optical stimulus applied by the optical actuator as the bias current increases.
  16. 제13항에 있어서, The method of claim 13,
    상기 포지티브 피드백 유닛은 차동 증폭기를 포함하며, The positive feedback unit comprises a differential amplifier,
    상기 차동 증폭기의 제1 입력단에는 기준 전압이 인가되고, 상기 차동 증폭기의 제2 입력단에는 상기 바이어스 전류가 입력되고, 상기 제2 입력단과 상기 차동 증폭기의 출력단 사이에는 저항이 연결되고, 상기 출력단은 상기 광학적 액츄에이터에 연결되는 센싱 시스템. A reference voltage is applied to the first input terminal of the differential amplifier, the bias current is input to the second input terminal of the differential amplifier, a resistor is connected between the second input terminal and the output terminal of the differential amplifier, and the output terminal is the Sensing system connected to the optical actuator.
  17. 제13항에 있어서, The method of claim 13,
    상기 비광학적 검출기는 상기 바이어스 전류 및 상기 비광학적 반응에 대응하는 센싱 전압을 출력하는 센싱 시스템. And the non-optical detector outputs a sensing voltage corresponding to the bias current and the non-optical response.
  18. 제17항에 있어서,The method of claim 17,
    상기 비광학적 검출기는 상기 바이어스 전류가 증가함에 따라 상기 센싱 전압이 감소하는 스냅백 구간을 가지는 센싱 시스템.The non-optical detector has a snapback period in which the sensing voltage decreases as the bias current increases.
  19. 제18항에 있어서, The method of claim 18,
    상기 스냅백 구간에서 소정의 상기 바이어스 전류를 제공하면서 상기 센싱 전압을 측정함으로써 상기 매질의 성질을 측정하는 출력부를 더 포함하는 센싱 시스템. And an output unit configured to measure a property of the medium by measuring the sensing voltage while providing the predetermined bias current in the snapback period.
  20. 제19항에 있어서, The method of claim 19,
    상기 매질의 상기 성질은 상기 매질에 포함된 소정 물질의 농도, 상기 매질의 온도, 상기 매질의 굴절율, 상기 매질의 탁도 및 상기 매질의 밀도 중 적어도 어느 하나를 포함하는 센싱 시스템.Wherein said property of said medium comprises at least one of a concentration of a predetermined material contained in said medium, a temperature of said medium, a refractive index of said medium, a haze of said medium, and a density of said medium.
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