KR100551232B1 - Measurement system for using diode laser - Google Patents

Abstract

The present invention provides a measurement system using a diode laser that can be measured without affecting the fluid or flame non-contact, an oscillator including a plurality of diode lasers each oscillating a beam of a specific wavelength; A light receiving unit which receives a laser beam and converts the laser beam into an electrical signal to measure an amount of light absorbed by the medium when the laser beams oscillated from the plurality of diode lasers pass through the medium; A collecting and analyzing unit collecting and analyzing and extracting an electrical signal emitted from the light receiving unit to distinguish the laser beams oscillated by the plurality of diode lasers; A controller for adjusting the temperature of the diode laser and the current scanned by the diode laser to control the wavelength of the oscillated laser beam; A laser beam passing through a medium is applied to the diode lasers and the collection and analysis unit by being connected to the collection and analysis unit and the control unit, and to distinguish the laser beams of the collection and analysis unit. A signal generator for modulating a wavelength; And a central operation unit connected to the signal generator and the controller to control data processing and the signal generator.

Diode Laser, Flame, Instrumentation, Control, Arithmetic

Description

Measurement system for using diode laser {Measurement system for using diode laser}

1 is a block diagram showing a measurement system using a diode laser according to the present invention,

2 to 5 are graphs shown for comparing the measured value and the analyzed value using the measurement system according to the present invention.

The present invention relates to a measurement system, and more particularly to a measurement system using a diode laser that can measure the concentration, temperature, flow rate, mass flow rate, etc. of each component of the fluid using a laser beam.

In general, a measurement system is a very important device that is the cornerstone for research and development of an object by collecting accurate information about an object, interpreting and studying the object, and suggesting a problem or improvement direction of the object. There is a contact method for determining the characteristics of an object through direct contact with an object and a non-contact method for identifying the characteristics of an object without directly contacting the object.

The contact method can obtain information about an object conveniently and safely through a simple tool, but its object is limited, and especially in the case of air fluid or flame whose results vary greatly even under minute external conditions, There is a limit in understanding the characteristics.

Therefore, in the case of measuring the components of an air fluid or flame, a non-contact method is adopted, and among the non-contact methods, a diode laser is a method of measuring an object by transmission of light through an optical fiber.

In accordance with such technical development, the present invention provides a measurement system using a diode laser capable of non-contact measurement of an air fluid or flame component without affecting the fluid or flame.

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The measurement system of the present invention comprises: an oscillator including a plurality of diode lasers each oscillating a beam of a specific wavelength; A light receiving unit which receives a laser beam and converts the laser beam into an electrical signal to measure an amount of light absorbed by the medium when the laser beams oscillated from the plurality of diode lasers pass through the medium; A collecting and analyzing unit collecting and analyzing and extracting an electrical signal emitted from the light receiving unit to distinguish the laser beams oscillated by the plurality of diode lasers; A controller for adjusting the temperature of the diode laser and the current scanned by the diode laser to control the wavelength of the oscillated laser beam; A laser beam passing through a medium is applied to the diode lasers and the collection and analysis unit by being connected to the collection and analysis unit and the control unit, and to distinguish the laser beams of the collection and analysis unit. A signal generator for modulating a wavelength; And a central operation unit connected to the signal generator and the controller to control data processing and the signal generator.
Another metrology system of the present invention comprises: an oscillator comprising a plurality of diode lasers forming a beam of a particular wavelength; A light receiving unit which receives a laser beam and converts the laser beam into an electrical signal to measure an amount of light absorbed by the medium when the laser beams oscillated from the plurality of diode lasers pass through the medium; In order to distinguish the laser beams oscillated from the plurality of diode laser, the collection and analysis unit for collecting and analyzing the electrical signal from the light-receiving unit, and detects the modulation frequency applied to increase the signal-to-noise ratio; A control unit including a temperature controller and a scan current controller for adjusting the temperature of the diode laser and the current scanned by the diode laser, respectively; It is connected to the collection and analysis unit and the control unit, in order to distinguish the laser beam of the collection and analysis unit, a different type of unique electrical signal is applied to the diode laser and the collection and analysis unit through the control unit, and passes through the medium A signal generator for modulating a wavelength of the laser beam; And a central operation unit connected to the signal generator and the controller to control data processing and the signal generator.
Another metrology system of the present invention comprises: an oscillator comprising a plurality of diode lasers forming a beam of a particular wavelength; A light receiving unit which receives a laser beam and converts the laser beam into an electrical signal to measure an amount of light absorbed by the medium when the laser beams oscillated from the plurality of diode lasers pass through the medium; In order to distinguish the laser beams oscillated from the plurality of diode laser, the collection and analysis unit for collecting and analyzing the electrical signal from the light-receiving unit, and detects the modulation frequency applied to increase the signal-to-noise ratio; A controller for adjusting a temperature of the diode laser and a current scanned by the diode laser to control a wavelength of a laser beam; It is connected to the collection and analysis unit and the control unit, in order to distinguish the laser beam of the collection and analysis unit, a different type of unique electrical signal is applied to the diode laser and the collection and analysis unit through the control unit, and passes through the medium A signal generator for modulating a wavelength of the laser beam; And a central processing unit connected to the signal generator and the controller to control data processing and the signal generator, wherein the plurality of diode lasers are connected to an optical splitter through an optical fiber, and the optical splitter is a parallel optical lens through an optical fiber. In the parallel optical lens, a laser beam having a straightness is scanned and passed through a medium, and the laser beam passing through the medium is absorbed by the light receiving unit through a condenser lens.

Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings.

1 is a block diagram showing a measurement system using a diode laser according to the present invention, Figures 2 to 5 are graphs for comparing the measured value and the analysis value using the measurement system according to the present invention.

The measurement system according to the present invention comprises a light emitting unit 10 including a plurality of diode lasers (1, 2, ..., n) for oscillating a laser beam of a specific wavelength, and a light receiving unit for detecting a laser beam passing through a medium. 20, a control unit 30 for controlling the temperature and wavelength of the laser beam oscillating from the diode lasers 1, 2, ..., n, a signal generator 40 for generating an electric signal, and a light receiving unit It is composed of a collection and analysis unit 50 for collecting and analyzing the electrical signal from the (20), and a central operation unit 60 for data processing and control.

Here, the diode lasers 1, 2..., N constituting the light emitting unit 10 are diode lasers having a specific wavelength depending on a target gas to be measured. The wavelengths emitted by the diode lasers (1, 2, ..., n) emit beams of different wavelengths depending on the components constituting the diode. However, in order to obtain a beam of a specific wavelength for concentration analysis or temperature analysis of the medium to be measured, the laser beam emitted from the diode lasers (1, 2, ..., n) must be fine tuned.

The wavelength of the laser beam oscillated by the diode lasers 1, 2, ..., n changes depending on the temperature of the diode lasers 1, 2, ..., n and the scanning current. That is, by adjusting the temperature of the diode laser and the scanning current scanned by the diode laser to obtain a laser beam having a wavelength necessary for measuring the medium, fine adjustment is possible to a desired wavelength, and the temperature controller and the scan included in the controller 30 are scanned. Finely adjusted by the current regulator.

A plurality of diode lasers (1, 2, ..., n) are connected to the optical splitter 12 through the optical fiber 11, as shown in Figure 1, the optical splitter 12 through the optical fiber 13 It is connected to the parallel light lens 14.

The laser beams oscillated from the plurality of diode lasers 1, 2, ..., n are distributed in the optical splitter 12 and sent through the optical fiber 13 to the parallel light lens 14, so that the parallel light lens ( 14, the laser beam has a straightness. The laser beam having the straightness by the parallel light lens 14 passes through the medium and is received by the light receiving unit 20 through the condenser lens 15.

The light receiving unit 20 receives a laser beam absorbed by the target medium while the laser beam emitted from the diode lasers 1, 2,..., N passes through the target medium, and receives the target from the light receiving unit 20. The amount of light absorbed by the medium is measured. The light receiving unit 20 includes a photodiode, and the intensity of the received laser beam is converted into an electrical signal in the light receiving unit 20 and sent to the signal collection and analysis unit 50 for signal processing.

The controller 30 adjusts the temperature and the scan current of the diode lasers 1, 2, ..., n so that the laser beam oscillated from the diode lasers 1, 2, ..., n is formed at a specific wavelength. Adjust

The controller 30 is largely divided into a temperature controller and a scan current controller as described above, and the temperature controller measures precision temperature in order to keep the temperature of the diode lasers 1, 2, ..., n constant at a desired temperature. The sensor measures the temperature of the diode lasers (1, 2, ..., n) and maintains the temperature of the diode lasers (1, 2, ..., n) at all times through the electric cooler and the electric heater. The temperature deviation of the diode lasers 1, 2, ..., n is maintained within several milli K (Kelvin temperature).

Also, the scan current controller finely adjusts the scan current supplied to the diode lasers 1, 2, ..., n so that a uniform current is supplied to the diode lasers 1, 2, ..., n.

The signal generator 40 applies an electrical signal of a constant frequency to the diode lasers 1, 2, ..., n and the signal collection and analysis unit 50 to modulate the gas concentration and temperature measurement accuracy. . Through such modulation, the wavelength of the laser beam oscillated by the diode lasers (1, 2, ..., n) also occurs at the same frequency as the modulation frequency. The wavelength of the laser beam is also changed in absorption of the modulation frequency, and the signal acquisition and analysis unit 50 modulates the modulation frequency through a lock-in amplifier included in the signal collection and analysis unit 50. Upon detection, the first derivative form of the amount of absorbed light depending on the wavelength can be extracted. By applying such a method, the signal-to-noise ratio can be greatly increased, and the measurement accuracy of the amount of absorbed light can be increased.

In addition, in order to simultaneously measure several target gases through one light receiving unit 20, laser beams oscillated by the respective diode lasers 1, 2,. In order to distinguish the laser beams, as described above, intrinsic electrical signals (Ramp Signals) of different types are transmitted by the signal generator 40 to the diode lasers 1, 2,..., N. ), The laser beam passing through the medium, and the laser beam passing through the medium are received by the light receiving unit 20, and the converted electrical signal is extracted and separated from the signal collection and analysis unit 50, whereby a plurality of target gases are included in one light receiving unit. Can be measured by 20. This unique electrical signal is also generated by the signal generator 40.

As described above, the signal collection and analysis unit 50 detects and analyzes and extracts a unique electric signal for distinguishing the laser beams oscillated from the plurality of diode lasers (1, 2, ..., n). It has the function of analyzing the absorbed light amount by detecting the applied modulation frequency to increase the noise ratio.

The signal collection and analysis unit 50 includes a concentration analyzer 51 for analyzing the concentration of the medium, a temperature analyzer 52 for analyzing the temperature of the medium gas, and a speed analyzer 53 for analyzing the molecular movement speed of the medium gas. And a mass flow rate analyzer 54 for analyzing the mass flow rate of the medium gas.

The concentration analyzer 51 analyzes the concentration of the medium gas through the following principle. That is, the gas absorbs the light of the laser beam passing through the medium, depending on the quantum mechanical properties of the constituent molecules. FIG. 4 shows the absorption intensity of each carbon dioxide gas in the medium, and as can be seen from FIG. 4, the absorption proceeds over almost the entire wavelength of the carbon dioxide gas. However, in the vicinity of a specific wavelength of carbon dioxide gas, the absorption intensity is greater than that of other wavelengths. This all depends on the quantum mechanical properties of the gas. In this way, the gas has a unique optical absorption wavelength band, and when the laser beam passes through the gas, the light absorption amount is measured by comparing the light intensity before and after the passage, and the central computing device 60 calculates the molecular number density through the gas. As a result, the concentration of the gas in the medium is measured.

When the laser beam passes through the medium, the temperature analyzer 52 detects a temperature change of the laser beam before and after the medium and measures the temperature change.

과 같은 식을 기초로 한 도플러 효과에 의해 분자의 이동 속도에 따라 파장이 변하게 된다. 이를 이용하여 분자의 이동 속도를 계측할 수 있으며 분자의 속도와 동일하다고 가정할 수 있으므로 이를 통하여 유체의 속도를 계측하는 것이다.The speed analyzer 53 measures the speed by detecting scattering when the laser beam passes through the molecular gas. In general, the wavelength of the laser beam scattered by the molecule is scattered by the laser beam of the same wavelength as the irradiated wavelength, but for moving molecules,

The wavelength is changed according to the moving speed of the molecule by the Doppler effect based on the equation. By using this, it is possible to measure the moving speed of the molecule and can be assumed to be the same as the speed of the molecule, thereby measuring the speed of the fluid.

The mass flow rate analyzer 54 is defined as the product of the fluid mass, the density, and the inspection area through which the fluid passes. Therefore, as mentioned above, the mass flow rate of the fluid can be obtained by measuring the fluid velocity and the molecular number density. have.

Measurement of the mole fraction of carbon monoxide (CO) in flue gas according to the mass flow rate of gas, the equivalent ratio of propane-air flame, the absorption rate of laser beam of carbon dioxide (CO ₂ ), and the temperature for hydrogen-air flame The measurement was performed.

In Figure 2 is a graph measuring the mass flow rate of the gas, the mass flow rate and LDV (Laser Doppler Velocimeter) measured using a measurement system using a diode laser (1, 2, ..., n) according to the present invention One mass flow rate is compared.

3 is a result of measuring the mole fraction of carbon monoxide in the exhaust gas according to the equivalent ratio change when the flame is formed by mixing propane-air. It can be seen that comparing the measured and interpreted values shows very similar results.

In FIG. 4, the laser beam absorption rate according to the concentration of carbon dioxide is shown. The straight line is an analytical value and the square box is an actual value. From this graph, it can be seen that the measured value does not deviate significantly from the straight line, which is the analyzed value.

In FIG. 5, the temperature of the hydrogen-air flame is measured and shown in a graph. The solid line in the graph shows the measured thermocouple, the dotted line shows the equilibrium state, and the dot shows the measured temperature. From this graph, it can be seen that the temperature measured by the thermocouple, which is the actual temperature, is very close to the temperature measured by the diode laser, and the temperature of the flame can be accurately measured by the diode laser measuring device.

As described above, according to the present invention, by irradiating the laser beam toward the fluid or flame and obtaining the desired information by using the detection data obtained from the light receiving unit, since the laser beam does not have any influence while passing through the fluid or flame, Measurement becomes possible.

Claims (4)

An oscillator including a plurality of diode lasers each oscillating a beam having a specific wavelength; A light receiving unit which receives a laser beam and converts the laser beam into an electrical signal to measure an amount of light absorbed by the medium when the laser beams oscillated from the plurality of diode lasers pass through the medium; A collecting and analyzing unit collecting and analyzing and extracting an electrical signal emitted from the light receiving unit to distinguish the laser beams oscillated by the plurality of diode lasers; A controller for adjusting the temperature of the diode laser and the current scanned by the diode laser to control the wavelength of the oscillated laser beam; A laser beam passing through a medium is applied to the diode lasers and the collection and analysis unit by being connected to the collection and analysis unit and the control unit, and to distinguish the laser beams of the collection and analysis unit. A signal generator for modulating a wavelength; And A measurement system using a diode laser connected to the signal generation unit and the control unit and including a central processing unit to control data processing and the signal generation unit. An oscillator including a plurality of diode lasers forming a beam of a specific wavelength; A light receiving unit which receives a laser beam and converts the laser beam into an electrical signal to measure an amount of light absorbed by the medium when the laser beams oscillated from the plurality of diode lasers pass through the medium; In order to distinguish the laser beams oscillated from the plurality of diode laser, the collection and analysis unit for collecting and analyzing the electrical signal from the light-receiving unit, and detects the modulation frequency applied to increase the signal-to-noise ratio; A control unit including a temperature controller and a scan current controller for adjusting the temperature of the diode laser and the current scanned by the diode laser, respectively; It is connected to the collection and analysis unit and the control unit, in order to distinguish the laser beam of the collection and analysis unit, a different type of unique electrical signal is applied to the diode laser and the collection and analysis unit through the control unit, and passes through the medium A signal generator for modulating a wavelength of the laser beam; And Measurement system using a diode laser connected to the signal generator and the control unit including a central processing unit for controlling the data processing and the signal generator. An oscillator including a plurality of diode lasers forming a beam of a specific wavelength; A light receiving unit which receives a laser beam and converts the laser beam into an electrical signal to measure an amount of light absorbed by the medium when the laser beams oscillated from the plurality of diode lasers pass through the medium; In order to distinguish the laser beams oscillated from the plurality of diode laser, the collection and analysis unit for collecting and analyzing the electrical signal from the light-receiving unit, and detects the modulation frequency applied to increase the signal-to-noise ratio; A controller for adjusting a temperature of the diode laser and a current scanned by the diode laser to control a wavelength of a laser beam; It is connected to the collection and analysis unit and the control unit, in order to distinguish the laser beam of the collection and analysis unit, a different type of unique electrical signal is applied to the diode laser and the collection and analysis unit through the control unit, and passes through the medium A signal generator for modulating a wavelength of the laser beam; And A central computing device connected to the signal generator and a controller to control data processing and the signal generator; The plurality of diode lasers are connected to an optical splitter through an optical fiber, and the optical splitter is connected to a parallel light lens through an optical fiber, in which the laser beam having a straightness is scanned and passes through the medium, and passes through the medium. A measurement system using a diode laser that absorbs a laser beam through the light collecting lens. The measurement system according to any one of claims 1 to 3, wherein the collecting and analyzing unit measures a concentration of a gas, a change in temperature, a velocity of a gas, and a mass flow rate.

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