JP2010197310A - Optical chopper and optical analyzer - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a miniaturizable chopper heightening an S/N ratio of light received by a photodetector, and to provide a miniaturizable optical analyzer having high analysis accuracy. <P>SOLUTION: A THC measuring device 100 includes an infrared lamp 10 for generating light, a spectrometer 20 for fluctuating a wavelength of light periodically, a photodiode 30 for detecting intensity of light, a gas container storing measuring object gas 1 and transmissible by light generated from the infrared lamp 10, and an optical chopper 50. The optical chopper 50 includes; a MEMS chopper member 51 having a base part 51a on which an opening part 51c transmissible by light is formed, and a rotation part 51b for switching to either state of a light transmissible state and a light blocking state by being rotated corresponding to a voltage application state; and a slit member 56 on which a slit 56a for narrowing the light is formed. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to an optical chopper that is disposed in the middle of an optical path through which light generated from a light source passes, and periodically transmits and blocks the light, and an optical analyzer having such an optical chopper. .

  Conventionally, technologies for measuring the concentration of hydrocarbons contained in exhaust gases of automobiles and the like are classified according to the measurement principle. Typical ones are those using a flame ionization detector (FID), non-dispersive infrared rays. The thing using the analysis method (Non-Dispersive Infrared Analyzer) is known. As a technique using a non-dispersive infrared analysis method, a technique described in Patent Document 1 is known.

  However, the technique using the flame ionization method is to count the number of carbon atoms contained in the gas to be measured, and the measurement accuracy itself is high, but it is included in the gas to be measured. In other words, the composition of each hydrocarbon species cannot be measured, and it is unsuitable for real-time measurement.

In principle, the technology using non-dispersive infrared analysis can measure non-contact concentration of hydrocarbons in real time with no response delay. However, hydrocarbons have their own absorption wavelength band (absorption). Therefore, it is necessary to prepare a light source and a light receiving element that generate light in a wavelength band corresponding to each type of hydrocarbon contained in the gas to be measured.
In particular, since the types of hydrocarbons contained in the exhaust gas of automobiles and the like exceed 200 types in some cases, the apparatus becomes very large when light sources and light receiving elements corresponding to all types of hydrocarbons are prepared, In addition, there is a problem that the manufacturing cost of the device becomes enormous.

As a technique for solving the above-mentioned problem, the applicants stated that "irradiation of irradiating light having a wavelength band including an absorption region common to the one or more chemical species to a gas containing hydrocarbons of one or more chemical species. An absorbance of the common absorption region based on the light detected by the detection unit, a detection unit that detects the light irradiated to the gas by the irradiation unit, and the common based on the absorbance And a analyzer for calculating the sum of the concentrations of chemical species that absorb light in the wavelength band of the absorption region of “a hydrocarbon concentration measuring apparatus” (see Japanese Patent Application No. 2007-289766).
In this technique, for example, among hydrocarbons, (a) a group consisting of alkanes and alkenes, (b) a group consisting of aromatic hydrocarbons, and (c) a group consisting of alkynes absorb light in different wavelength bands. By detecting the absorption amount of light in the wavelength band corresponding to each group, the concentration (sum) of hydrocarbons belonging to each group can be detected, and the number of light sources and light receiving elements required for the device can be determined. This makes it possible to reduce the size of the device.

Further, as a specific configuration of the irradiation unit of the hydrocarbon concentration measuring device, a combination of a light source capable of generating light in a wide wavelength band and a spectroscope that varies the wavelength of light from the light source at a predetermined frequency Can be considered.
Further, as a specific configuration of the spectroscope, a combination of a MEMS mirror that changes a reflection angle of light from the light source at a predetermined frequency and a grating that further reflects light reflected by the MEMS mirror is considered. It is done.

  Paragraph 0022 of Patent Document 2 discloses an example in which a MEMS mirror is used as an optical path switching device that causes a light receiver to alternately receive light that has passed through a measurement target gas and light from a reference light source.

  However, one light source that generates light in a wavelength band that covers all the absorption wavelength bands of the groups (a) to (c), and a spectrometer that changes the wavelength of light from the light source over time (for example, When the technique proposed by the applicants is implemented by an optical analyzer that includes a combination of a grating and a MEMS mirror) and a light receiver that detects the intensity of light received from the spectroscope, the light receiver receives light. Since the light that has been previously split into a plurality of wavelength bands by the spectroscope, its light intensity is small, and the S / N ratio of the light received by the photoreceiver becomes small, so that the detection accuracy of the photoreceiver, and thus optical There is a problem that the analysis accuracy of the expression analyzer decreases.

  In Patent Document 3, the middle part of the optical path from the light source to the light receiver is branched into two of the optical path for measurement and the optical path for reference, and a container in which the measurement target gas is sealed is arranged in the middle part of the optical path for measurement, A gas analyzer that can measure the amount of absorption in a plurality of wavelength bands of a gas to be measured by light generated by one light source by arranging a spectroscope that combines a MEMS mirror and a grating in the middle of the reference optical path. It is disclosed.

  In Patent Document 4, a middle part of an optical path from a light source to a light receiver is branched into two parts, a measurement optical path and a reference optical path, and a container in which a measurement target gas is sealed in the middle part of the measurement optical path, a MEMS mirror, and A spectrometer combined with a grating is arranged, and a spectrometer combined with a MEMS mirror and a grating is arranged in the middle of the reference optical path, so that light generated by a single light source can be used for a plurality of wavelength bands of the measurement target gas. A gas analyzer capable of measuring absorption is disclosed.

  However, since the gas analyzers described in Patent Document 3 and Patent Document 4 also have a structure in which light generated from one light source is divided into a plurality of wavelength bands and incident on the detector, S of the light received by the light receiver. There arises a problem that the / N ratio becomes small.

As a general method for solving the decrease in the detection accuracy (decrease in the S / N ratio) of the light receiver, a method of chopping light received by the light receiver, that is, a method of turning on / off with time is known. Yes.
More specifically, the light intensity detected by the light receiver by using the difference between the light intensity detected by the light receiver when the light is ON and the light intensity detected by the light receiver when the light is OFF. The influence of the noise component contained in is eliminated, and the detection accuracy of the light receiver is improved.

  As a general method of chopping the light received by the light receiver, (A) a method in which a rotating disk type optical chopper is arranged in the middle of the optical path from the light source to the light receiver, and (B) the light source itself is blinked. A method of turning on / off power supply to a light source with time is known.

However, (A) the method of arranging a rotating disk type optical chopper in the middle of the optical path from the light source to the light receiver has the following problems.
The diameter of the rotating disk of a rotating disk type optical chopper currently on the market is about 10 cm, even if it is small, and a motor for rotating the rotating disk is required, so the rotating disk type optical chopper is considerably larger as a whole. End up.
In particular, when the size of the optical system (light source, optical chopper, spectroscope, and light receiver) of the optical analyzer is large, the optical system interferes with various parts, etc. There arises a problem that analysis cannot be performed with an optical analyzer.
In addition, when analyzing exhaust gas from automobiles, real-time analysis results are required, and it is important to shorten the period of wavelength fluctuation of light by the spectrometer (increase the fluctuation frequency). Along with this, it is required that the chopping cycle of the optical chopper (cycle for turning on / off the light) be further shorter than the cycle of the wavelength variation of the light by the spectrometer (the chopping frequency of the optical chopper is further increased).
As a method of shortening the chopping cycle of the optical chopper, there are a method of increasing the number of rotations of a motor for rotating the rotating disk and a method of increasing the diameter of the rotating disk to increase the number of slits formed in the rotating disk. However, both increase the size and cost of the rotating disk type optical chopper.

  (B) As a method of blinking the light source itself, a method of employing an LED as a light source, a method of employing an infrared element (infrared lamp) as a light source, and the like are known.

  The method of adopting the LED as the light source is superior in terms of shortening the blinking cycle of the light source (increasing the blinking frequency) since the LED can be switched at high speed, but the LED generally has a small output ( (About several tens of μW), the intensity of generated light is low.

  The method of using an infrared element as the light source can increase the output, but has a problem that the blinking cycle is long (about several tens of msec).

JP-A-4-225142 Special table 2008-510961 gazette JP 2005-315711 A JP 2006-138766 A

  The present invention has been made in view of the situation as described above. The chopper capable of increasing the S / N ratio of light received by the light receiver and reducing the size, and the analysis accuracy being high and small. Provided is an optical analyzer that can be configured.

  The problem to be solved by the present invention is as described above. Next, means for solving the problem will be described.

That is, in claim 1,
A light source that generates light;
A spectroscope for periodically changing the wavelength of the light generated by the light source;
A light receiver for detecting the intensity of light whose wavelength has been varied by the spectroscope;
The optical path formed by the light source, the spectroscope and the light receiver is disposed at a position sandwiched by the spectroscope and the light receiver or a position sandwiched by the light source and the spectroscope, and can accommodate a measurement target gas, and A gas container capable of transmitting light;
An optical chopper used in an optical analyzer comprising:
A base formed with an opening through which light generated by the light source can pass, and light generated by the light source by opening the opening by rotating with respect to the base corresponding to a voltage application state. A MEMS chopper member comprising a rotating portion that switches to either a passing state in which the light passes or a blocking state that blocks the light generated by the light source by closing the opening;
A slit member disposed at a position adjacent to the MEMS chopper member, and formed with a slit for narrowing light generated by the light source;
It comprises.

In claim 2,
The MEMS chopper member is
It is arranged upstream of the slit member in the optical path of the light.

In claim 3,
The spectrometer is
A grating that reflects the light generated by the light source at different reflection angles for each wavelength;
A MEMS mirror that reflects the light reflected by the grating in a predetermined direction;
It comprises.

In claim 4,
The chopping cycle of the MEMS chopper member is shorter than the spectral cycle of the spectrometer.

In claim 5,
A condensing lens that condenses the light generated by the light source and a collimator lens that collimates the light collected by the condensing lens at a position between the light source and the spectroscope in the optical path. Is to be placed.

In claim 6,
The opening of the MEMS chopper member and the slit of the slit member are
It is arranged at a position corresponding to the focal point of the light formed at a position sandwiched between the condenser lens and the collimating lens in the optical path.

In claim 7,
The opening of the MEMS chopper member and the slit of the slit member are
It is arranged at a position between the collimator lens and the spectroscope or a position between the spectroscope and the light receiver in the optical path.

In claim 8,
A light source that generates light;
A spectroscope for periodically changing the wavelength of the light generated by the light source;
A light receiver for detecting the intensity of light whose wavelength has been varied by the spectroscope;
The optical path formed by the light source, the spectroscope and the light receiver is disposed at a position sandwiched by the spectroscope and the light receiver or a position sandwiched by the light source and the spectroscope, and can accommodate a measurement target gas, and A gas container capable of transmitting light;
An optical chopper disposed in the middle of the optical path;
Comprising
The light chopper is
A base formed with an opening through which light generated by the light source can pass, and light generated by the light source by opening the opening by rotating with respect to the base corresponding to a voltage application state. A MEMS chopper member comprising a rotating portion that switches to either a passing state in which the light passes or a blocking state that blocks the light generated by the light source by closing the opening;
A slit member disposed at a position adjacent to the MEMS chopper member, and formed with a slit for narrowing light generated by the light source;
It comprises.

In claim 9,
The MEMS chopper member is
It is arranged upstream of the slit member in the optical path of the light.

In claim 10,
The spectrometer is
A grating that reflects the light generated by the light source at different reflection angles for each wavelength;
A MEMS mirror that reflects the light reflected by the grating in a predetermined direction;
It comprises.

In claim 11,
The chopping cycle of the MEMS chopper member is shorter than the spectral cycle of the spectrometer.

In claim 12,
A condensing lens that condenses the light generated by the light source and a collimator lens that collimates the light collected by the condensing lens at a position between the light source and the spectroscope in the optical path. Is to be placed.

In claim 13,
The opening of the MEMS chopper member and the slit of the slit member are
It is arranged at a position corresponding to the focal point of the light formed at a position sandwiched between the condenser lens and the collimating lens in the optical path.

In claim 14,
The opening of the MEMS chopper member and the slit of the slit member are
It is arranged at a position between the collimator lens and the spectroscope or a position between the spectroscope and the light receiver in the optical path.

In claim 15,
A data processing device is provided that calculates the concentration of the gas species contained in the measurement target gas based on the intensity of light received by the light receiver.

The invention described in claims 1 to 7 of the present application has an effect that the S / N ratio of the light received by the light receiver can be increased and the size can be reduced.
The invention according to claims 8 to 15 of the present application has an effect that the analysis accuracy is high and the size can be reduced.

The figure which shows 1st embodiment of the optical analyzer which concerns on this invention. The figure which shows the optical system of 1st embodiment of the optical analyzer which concerns on this invention. The figure which shows another embodiment of the optical system of the optical analyzer which concerns on this invention. The figure which shows another embodiment of the optical system of the optical analyzer which similarly concerns on this invention. The figure which shows 2nd embodiment of the optical analyzer which concerns on this invention.

  Below, the THC measuring apparatus 100 which is 1st embodiment of the optical analyzer which concerns on this invention using FIG. 1 and FIG. 2 is demonstrated.

A THC measurement device 100 shown in FIG. 1 is a device that measures the total concentration of hydrocarbons (Total Hydrocarbon) contained in the measurement target gas 1.
“Measurement gas” broadly refers to a gas containing hydrocarbons at least in part. Specific examples of “measurement target gas” include automobile exhaust gas.
The hydrocarbon contained in the measurement target gas is not necessarily vaporized at normal temperature (25 ° C.) and normal pressure (1 atm), and may be vaporized by heating, for example.
“Hydrocarbon” includes one or more chemical species which are compounds composed of carbon and hydrogen.
Chemical species contained in hydrocarbons are classified into alkanes, alkenes, alkynes, aromatic hydrocarbons and the like based on their structures.
“Alkane” refers to a chain saturated hydrocarbon represented by the general formula C _n H _{2n + 2} (n: an integer of 1 or more). In the present invention, cycloalkane is included in alkane.
“Cycloalkane” refers to a cyclic saturated hydrocarbon represented by the general formula C _n H _2n (n: an integer of 3 or more).
“Alkene” refers to a chain unsaturated hydrocarbon represented by the general formula C _n H _2n (n: an integer of 2 or more).
“Alkyne” refers to a chain unsaturated hydrocarbon represented by the general formula C _n H _2n-2 (n: an integer of 2 or more).
An “aromatic hydrocarbon” is a hydrocarbon having a single ring or a plurality of ring (fused ring) structures.

The THC measuring apparatus 100 of the present embodiment includes (a) a group consisting of alkanes and alkenes, (b) a group consisting of aromatic hydrocarbons, and (c) an alkyne among the hydrocarbons contained in the measurement target gas 1. By utilizing the property that the hydrocarbons belonging to each group absorb light in different wavelength bands and detecting the amount of light absorbed in the wavelength bands corresponding to each group, the concentration sum of the hydrocarbons belonging to each group is calculated. taking measurement.
Note that "alkane and waveband hydrocarbons belonging to the group consisting of alkenes absorb light" is the wavelength band 2800 cm ^-1 or 3000 cm ^-1 following in terms of wavenumber, carbide belonging to the group consisting of "aromatic hydrocarbon waveband hydrogen absorbs "is 3200 cm ^-1 or less in the wavelength range 3000 cm ^-1 or more, in terms of wavenumber," waveband hydrocarbons belonging to the group consisting of alkynes absorb light "is in terms of wavenumber 3200 cm ^- The wavelength band is ¹ or more and 3400 cm ⁻¹ or less.

  The THC measurement device 100 includes a frame 110, a light source side optical system unit 120, a gas container 40, a photodiode 30, a chopper / spectrometer control device 70, a lock-in amplifier 80, and a data processing device 90.

The frame 110 is a structure for holding the relative positions of other members of the THC measuring apparatus 100, particularly members constituting the optical system.
The frame 110 includes a base member 111, a unit support member 112, a container support member 113, and a photodiode support member 114.

  The base member 111 is a member that forms the main structure of the frame 110. Other members constituting the frame 110 are fixed to the base member 111.

  The unit support member 112 is a member that fixes the light source side optical system unit 120 to the base member 111. The lower end portion of the unit support member 112 is fixed to the base member 111, and the upper end portion of the unit support member 112 is fixed to the light source side optical system unit 120.

  The container support member 113 is a member that fixes the gas container 40 to the base member 111. The lower end portion of the container support member 113 is fixed to the base member 111, and the upper end portion of the container support member 113 is fixed to the gas container 40.

  The photodiode support member 114 is a member that fixes the photodiode 30 to the base member 111. The lower end portion of the photodiode support member 114 is fixed to the base member 111, and the upper end portion of the photodiode support member 114 is fixed to the photodiode 30.

The light source side optical system unit 120 is a group of members arranged closer to the infrared lamp 10 than the gas container 40 in the optical system of the THC measuring apparatus 100.
The light source side optical system unit 120 includes a case 121, an infrared lamp 10, a first condenser lens 61, a light chopper 50, a collimator lens 62, a spectrometer 20, and a second condenser lens 63.

The case 121 is a box-shaped member, and accommodates other members constituting the light source side optical system unit 120 and holds the relative positional relationship of the other members.
The case 121 is fixed to the base member 111 via the unit support member 112.
Details of each member housed in the light source side optical system unit 120 (members forming the optical system of the THC measuring apparatus 100) will be described later.

The gas container 40 is a container for storing the measurement target gas 1.
The gas container 40 of the present embodiment includes a body member 41, an inlet side window member 42, and an outlet side window member 43.

The body member 41 is a cylindrical member forming the main structure of the gas container 40.
The body member 41 is interposed, for example, in the middle of an exhaust gas exhaust path of an automobile, and the measurement target gas 1 (in this case, exhaust gas) passes through the inside of the body member 41. The body member 41 is fixed to the base member 111 via the container support member 113.

  The entrance side window member 42 and the exit side window member 43 are members made of glass or quartz fitted into two openings formed in the body member 41.

  The photodiode 30 is fixed to the base member 111 via the photodiode support member 114. Details of the photodiode 30 will be described later.

Hereinafter, the optical system of the THC measurement apparatus 100 will be described.
As shown in FIG. 2, the optical system of the THC measurement apparatus 100 includes an infrared lamp 10, a spectroscope 20, a photodiode 30, a first condenser lens 61, a collimator lens 62, a second condenser lens 63, and an optical chopper 50. Composed.

The infrared lamp 10 is an embodiment of a light source according to the present invention, and is a member that forms the most upstream part of the optical system of the THC measurement apparatus 100.
As shown in FIG. 1, the infrared lamp 10 is fixed at a predetermined position inside the case 121.
The infrared lamp 10 of the present embodiment generates infrared light, and the wavelength band of infrared light generated by the infrared lamp 10 is “wavelength band absorbed by hydrocarbons belonging to the group consisting of alkanes and alkenes”. ”,“ Wavelength band absorbed by hydrocarbons belonging to the group consisting of aromatic hydrocarbons ”, and“ wavelength band absorbed by hydrocarbons belonging to the group consisting of alkynes ”.

The infrared lamp 10 of the present embodiment generates infrared light, but the light source according to the present invention is not limited to this. This is because the light (wavelength) generated by the light source according to the present invention is appropriately selected according to the wavelength band absorbed by the measurement target gas.
That is, the light generated by the light source according to the present invention includes infrared light, visible light, and ultraviolet light.

The spectroscope 20 is an embodiment of the spectroscope according to the present invention, and periodically changes the wavelength of light generated by the infrared lamp 10.
As shown in FIG. 2, the spectroscope 20 includes a grating 21 and a MEMS mirror 26.

The grating 21 diffracts the light generated by the infrared lamp 10 to divide the light for each wavelength.
The grating 21 of the present embodiment is a diffraction grating in which a large number of grooves (several hundreds to thousands of grooves per 1 mm) are formed. The light incident on the grating 21 is diffracted and dispersed for each wavelength, and the dispersed light is reflected at different reflection angles (diffraction angles) depending on the wavelength.
As shown in FIG. 1, the grating 21 is fixed at a predetermined position inside the case 121.

The MEMS mirror 26 reflects the light reflected by the grating 21 in a predetermined direction. The MEMS mirror 26 is manufactured by a so-called MEMS (Micro Electro Mechanical Systems) technology.
As shown in FIG. 1, the MEMS mirror 26 is fixed at a predetermined position inside the case 121.
As shown in FIG. 2, the MEMS mirror 26 has a base portion 26a and a rotating portion 26b.

  The base 26a is a flat plate-like member, and an opening 26c is formed at the center.

The rotation part 26b is a flat plate-like member, is disposed at a position accommodated in the opening 26c, and is rotatably connected to and supported by the base part 26a. The rotating part 26b rotates with respect to the base part 26a by elastically twisting the connecting part with the base part 26a.
As shown in FIG. 2, when no force is applied to the rotating portion 26b, the connecting portion of the rotating portion 26b and the base portion 26a is not elastically twisted, and the rotating portion 26b is a pair of plates of the base portion 26a. The surface is held in a posture (reference posture) in which the plate surface of the rotating portion 26b is parallel.
A thin film made of gold, aluminum, or the like is formed on one plate surface of the rotating portion 26 b, and the thin film forms a reflective surface of the MEMS mirror 26.

The MEMS mirror 26 of this embodiment is a so-called electromagnetic force type mirror.
A pair of permanent magnets are embedded in the base portion 26a so as to sandwich the opening portion 26c and eventually the rotating portion 26b. Accordingly, the rotating portion 26b is disposed in a magnetic field formed by the pair of permanent magnets.
In addition, a wiring capable of applying a voltage from the outside is formed in the rotating portion 26b.

When a voltage is applied to the wiring formed in the rotating part 26b, Lorentz force acts on the rotating part 26b arranged in a magnetic field formed by a pair of permanent magnets. As a result, the rotation part 26b rotates with respect to the base part 26a, and the angle of the reflective surface formed in the rotation part 26b is changed.
The magnitude of the Lorentz force acting on the rotating part 26b has a magnitude corresponding to the voltage value applied to the wiring formed on the rotating part 26b, and consequently the current value.
Therefore, by adjusting the voltage value (current value) applied to the wiring formed in the rotating portion 26b, the rotating angle of the rotating portion 26b and consequently the reflection angle of the MEMS mirror 26 can be adjusted. is there.

When the reflection angle of the MEMS mirror 26 changes, the angle at which the light reflected by the MEMS mirror 26 in a predetermined direction (in this embodiment, the direction toward the photodiode 30) is incident from the grating 21 changes.
Therefore, by adjusting the reflection angle of the MEMS mirror 26, the wavelength of light reflected by the MEMS mirror 26 in a predetermined direction can be adjusted.

Further, when the application of voltage to the wiring formed in the rotating portion 26b is stopped, the rotating portion 26b rotates to eliminate the elastic torsional deformation of the connecting portion with the base portion 26a and returns to the reference posture.
Therefore, by applying a voltage at a predetermined frequency to the wiring formed in the rotation unit 26b, the rotation unit 26b swings at the predetermined frequency, and the light reflected in the predetermined direction by the MEMS mirror 26 is reflected. Wavelength fluctuates periodically (light wavelength fluctuates periodically).
Hereinafter, the period in which the rotating portion 26b of the MEMS mirror 26 swings is referred to as “spectral period of the spectroscope 20”.

The MEMS mirror 26 of the present embodiment is a so-called electromagnetic force type mirror, but the MEMS mirror according to the present invention is not limited to this, and may be of other driving types (for example, electrostatic type, piezoelectric type, thermal strain type). You may rotate a rotation part with respect to a base.
The MEMS mirror according to the present invention can be achieved by a commercially available MEMS mirror.

The photodiode 30 is an embodiment of a light receiver according to the present invention, and detects the intensity of light whose wavelength has been varied by the spectrometer 20.
The photodiode 30 of the present embodiment is composed of a semiconductor element that detects the intensity of received light, and outputs (transmits) an electrical signal corresponding to the intensity of the received light.

1 and 2, the optical system of the THC measurement device 100 forms an optical path A from the infrared lamp 10 to the photodiode 30 through the spectroscope 20 and the gas container 40.
As shown in FIG. 1, the gas container 40 is disposed at a position sandwiched between the spectroscope 20 and the photodiode 30 in the optical path A.
The light generated by the infrared lamp 10 passes through the entrance-side window member 42 and enters the body member 41 in a state where the wavelength is periodically changed by the spectrometer 20. The light that has entered the body member 41 passes through the measurement object accommodated in the body member 41, then passes through the exit-side window member 43, and enters the outside of the body member 41 (outside the gas container 40). Guided and received by the photodiode 30.

The first condenser lens 61 is an embodiment of the condenser lens according to the present invention, and is an optical element that condenses (converges) the light generated by the infrared lamp 10.
As shown in FIG. 1, the first condenser lens 61 is fixed at a predetermined position inside the case 121.
As shown in FIG. 2, the first condenser lens 61 is disposed at a position sandwiched between the infrared lamp 10 and the spectroscope 20 in the optical path A.

The collimating lens 62 is an embodiment of the collimating lens according to the present invention, and the light condensed by the first condensing lens 61 is converted into parallel light and applied to the spectrometer 20 (more specifically, the grating 21). It is an optical element.
As shown in FIG. 1, the collimating lens 62 is fixed at a predetermined position inside the case 121.
As shown in FIG. 2, the collimator lens 62 is sandwiched between the infrared lamp 10 and the spectroscope 20 in the optical path A, and is disposed at a position downstream of the first condenser lens 61.
Further, the collimator lens 62 is disposed at a position downstream of the focal point B (white circle in FIG. 2) of the light collected by the first condenser lens 61 in the optical path A.

The second condenser lens 63 is an optical element that condenses (converges) the light whose wavelength has been changed by the spectroscope 20 and irradiates (receives) light to the photodiode 30.
As shown in FIG. 1, the second condenser lens 63 is fitted in an opening formed in the case 121 at a position facing the inlet-side window member 42 of the gas container 40, and from the inside of the light source-side optical system unit 120 to the outside. Also serves as a window to irradiate light.

The optical chopper 50 is an embodiment of the optical chopper according to the present invention.
The optical chopper 50 includes a MEMS chopper member 51 and a slit member 56.
As shown in FIG. 1, the optical chopper 50 is fixed at a predetermined position inside the case 121.
As shown in FIG. 2, the optical chopper 50 is disposed at a position sandwiched between the infrared lamp 10 and the spectroscope 20 in the optical path A, more specifically at a position sandwiched between the first condenser lens 61 and the collimator lens 62.

The MEMS chopper member 51 is an embodiment of the MEMS chopper member according to the present invention, and is manufactured by so-called MEMS (Micro Electro Mechanical Systems) technology.
As shown in FIG. 2, the MEMS chopper member 51 has a base portion 51a and a rotating portion 51b.

  The base 51a is a flat plate member having a pair of plate surfaces, and an opening 51c penetrating the pair of plate surfaces of the base 51a is formed at the center of the base 51a.

The rotation part 51b is a flat plate-like member, is disposed at a position accommodated in the opening 51c, and is rotatably connected to and supported by the base 51a. The rotating part 51b rotates with respect to the base 51a by elastically twisting the connecting part with the base 51a.
As shown in FIG. 2, when no force is applied to the rotating portion 51b, the connecting portion of the rotating portion 51b and the base portion 51a is not elastically twisted, and the rotating portion 51b is a pair of plates of the base portion 51a. The surface is held in a posture (reference posture) in which the plate surface of the rotating portion 51b is parallel. As a result, the opening 51c is closed (closed) by the rotating portion 51b.

The MEMS chopper member 51 of this embodiment is a so-called electromagnetic force type actuator.
A pair of permanent magnets are embedded in the base 51a so as to sandwich the opening 51c, and thus the rotating part 51b. Therefore, the rotating part 51b is disposed in a magnetic field formed by the pair of permanent magnets.
In addition, a wiring capable of applying a voltage from the outside is formed in the rotating portion 51b.

The rotating part 51b rotates with respect to the base part 51a corresponding to the voltage application state.
That is, when a voltage is applied to the wiring formed in the rotating part 51b, Lorentz force acts on the rotating part 51b arranged in a magnetic field formed by a pair of permanent magnets. As a result, the rotating part 51b rotates with respect to the base part 51a, and the opening 51c (strictly, a part of the opening 51c) is opened.

Further, when the application of the voltage to the wiring formed in the rotating portion 51b is stopped, the rotating portion 51b rotates to eliminate the elastic twisting deformation of the connecting portion with the base 51a and returns to the reference posture.
Therefore, by applying a voltage at a predetermined frequency to the wiring formed in the rotating portion 51b, the rotating portion 51b swings at the predetermined frequency and opens and closes the opening 51c.

As shown by a solid line in FIG. 2, when the rotating unit 51 b is in the reference posture, the light collected by the first condenser lens 61 is blocked by the rotating unit 51 b and does not reach the photodiode 30. A state in which light is blocked by the light chopper 50 when the rotating unit 51b takes the reference posture is referred to as a “blocking state”.
As shown by a dotted line in FIG. 2, when the rotating part 51b is in a posture of rotating with respect to the base part 51a, the light collected by the first condenser lens 61 is not blocked by the rotating part 51b. It passes through the opening 51c and reaches the photodiode 30. A state in which light passes through the light chopper 50 when the rotating unit 51b is rotated with respect to the base 51a is referred to as a “passing state”.
Thus, the rotation part 51b of the MEMS chopper member 51 can be switched to either the “passing state” or the “cut-off state” by rotating.
Hereinafter, the cycle in which the rotating portion 51b of the MEMS chopper member 51 rotates (swings), more precisely, the cycle from the start of the passing state to the transition to the passing state through the transition to the blocking state is referred to as “optical chopper”. 50 chopping cycles.

The MEMS chopper member 51 of the present embodiment is a so-called electromagnetic force type actuator, but the MEMS chopper member according to the present invention is not limited to this, and other drive types (for example, electrostatic type, piezoelectric type, thermal strain type). ) May rotate the rotating portion relative to the base.
Further, a commercially available MEMS mirror or other MEMS actuator can be used as the MEMS chopper member according to the present invention.

The “chopping period of the optical chopper 50” is set to be shorter than the “spectral period of the spectrometer 20” (the chopping frequency of the optical chopper 50 is set to be higher than the spectral frequency of the spectrometer 20). )
When the MEMS chopper member 51 is configured by diverting an existing MEMS mirror, the chopping cycle of the optical chopper 50 can be set to about 10 μsec to 100 μsec (the chopping frequency of the optical chopper 50 is set to about 10 kHz to 100 kHz). Is possible).
Therefore, it is possible to shorten the “spectral period of the spectroscope 20” within a range that does not become shorter than the chopping period of the optical chopper 50, which contributes to the improvement of the high-speed response (real-time property) of the THC measurement apparatus 100. Here, the high-speed response means that it is possible to accurately detect the composition variation (in this embodiment, variation in hydrocarbon concentration) of the measurement target gas in a very short time.

As shown in FIG. 2, in this embodiment, the opening 51 c of the MEMS chopper member 51 is disposed at a position corresponding to the focal point B (a position near the focal point B).
With this configuration, the light generated by the infrared lamp 10 passes through the opening 51c in a state where the light is converged finely, and the “passing state” can be achieved even if the rotating portion 51b does not rotate significantly from the reference posture. "And" blocking state "can be switched, and the chopping cycle of the optical chopper 50 can be further shortened.
By this chopping, the light receiving intensity is increased (depending on the frequency region, the sensitivity of the light receiving element is higher as the frequency is higher), and thus the S / N ratio can be increased. Further, by combining a lock-in amplifier, it is possible to effectively remove noise components, and it is possible to further increase the S / N ratio.

  In the present embodiment, the opening 51c is closed by the turning portion 51b when the turning portion 51b is in the reference posture. The term “closed” here means that the opening 51c is completely closed by the turning portion 51b. It does not indicate that it is sealed (there is no gap between the end surface of the opening 51c and the rotating portion 51b), but indicates that the light is covered to the extent that it cannot pass through the opening 51c.

The slit member 56 is an embodiment of the slit member according to the present invention, and restricts the light generated by the infrared lamp 10 (excluding disturbance light from the optical path A to improve the wavelength resolution of the THC measurement apparatus 100). Is.
The slit member 56 is a plate-like member having a pair of plate surfaces, and the slit member 56 is formed with a slit 56 a that is a groove penetrating the pair of plate surfaces of the slit member 56.

The slit member 56 is disposed at a position adjacent to the MEMS chopper member 51. In the present embodiment, the slit member 56 is bonded to the rear plate surface of the MEMS chopper member 51 (the plate surface on the downstream side of the optical path A among the pair of plate surfaces of the base portion 51a of the MEMS chopper member 51). It is fixed with.
Therefore, the MEMS chopper member 51 is disposed upstream of the slit member 56 in the light optical path A (the slit member 56 is disposed downstream of the MEMS chopper member 51 in the light optical path A).
This configuration has the following advantages. That is, if the MEMS chopper member is disposed downstream of the slit member in the optical path of light, a part of the light blocked (reflected) by the rotating portion of the MEMS chopper member is further reflected by the slit member. In some cases, the light becomes disturbance light, passes through the opening of the base portion of the MEMS chopper member, reaches the spectroscope, and eventually the light receiver, and decreases the detection accuracy of the light intensity by the light receiver.
Therefore, when the MEMS chopper member is arranged downstream of the slit member in the optical path of the light, the shape, surface color, arrangement, etc. of the slit member are separately devised in order to eliminate the influence of such disturbance light. Although it is necessary, when the slit member 56 is arranged on the downstream side of the MEMS chopper member 51 in the optical path A of the light as in this embodiment, the light blocked (reflected) by the rotating portion 51b is caused by the slit member 56. Since it is not reflected again, it is possible to easily eliminate the influence of disturbance light, and it is possible to improve the wavelength resolution of the THC measurement apparatus 100.

The slit 56a of the slit member 56 fixed to the MEMS chopper member 51 is disposed at a position corresponding to the focal point B (a position near the focal point B).
With this configuration, the light generated by the infrared lamp 10 passes through the slit 56a in a state where the light is converged finely, and the slit 56a is made as thin as possible while ensuring the amount of light passing through the slit 56a. It is possible to eliminate the influence of disturbance light, and to improve both the S / N ratio of the THC measurement apparatus 100 and the wavelength resolution.

When the MEMS chopper member 51 is configured by diverting an existing MEMS mirror, the MEMS chopper member 51 can be suppressed to a size of, for example, about 20 mm long × 30 mm wide × 5 mm thick. Further, the thickness of the slit member 56 can be suppressed to about several mm.
Accordingly, the size of the MEMS chopper member 51 and the slit member 56, that is, the optical chopper 50 can be made compact as a whole, and the optical chopper 50 can be downsized.
Further, by reducing the size of the optical chopper 50, it is possible to reduce the size of the entire optical system of the THC measuring apparatus 100. Downsizing the THC measuring device 100 is particularly effective when the exhaust gas of a running vehicle is analyzed with the THC measuring device 100 attached to the vehicle.

Below, the setting method of the opening width of the slit 56a is demonstrated.
Assuming that the wavelength of light incident on the grating 21 is λ, the incident angle of light incident on the grating 21 is α, and the interval between grooves formed in the grating 21 is t, the dispersion dλ in the grating 21 is expressed by the following equation (1). The

  When ½ of the width of the infrared lamp 10 (the width of the light source) is h and the focal length of the collimating lens 62 is f, the deviation ξ from the parallel light of the collimating lens 62 is expressed by the following formula 2. The

As shown in Equation 2, the deviation ξ increases in proportion to the width of the infrared lamp 10.
The deviation ξ shown in Equation 2 is equal to the deviation of the incident angle α of light incident on the grating 21, that is, dα (ξ = dα). Therefore, the width (1/2) of the infrared lamp 10 is The following equation 3 holds between the wavelength dispersion dλ.

From Equation 3, it is necessary to make the width of the infrared lamp 10 (the width of the light source) as small as possible in order to suppress the wavelength dispersion dλ in the grating 21. The wavelength resolution required for the THC measurement apparatus 100 is equal to the wavelength dispersion dλ in the grating 21.
Both the actual width of the infrared lamp 10 (the width of the light source) and the width of the opening 51c of the base 51a of the MEMS chopper member 51 are “substituting the wavelength resolution required for the THC measuring device 100 into the right side of Equation 3. If the width of the light source is larger than “the width of the light source calculated by”, the effect of improving the wavelength resolution by providing the slit member 56 can be obtained.

Hereinafter, a control system of the THC measurement apparatus 100 will be described.
As shown in FIG. 1, the control system of the THC measurement device 100 is configured by a chopper / spectrometer control device 70, a lock-in amplifier 80, and a data processing device 90.

The chopper / spectrometer control device 70 is a device that controls the operation of the optical chopper 50 and the MEMS mirror 26 of the spectroscope 20.
The chopper / spectrometer control device 70 is connected to the optical chopper 50, more precisely, to the MEMS chopper member 51, and has a predetermined period (period corresponding to the chopping period) in the wiring formed in the rotating part 51b of the MEMS chopper member 51. It is possible to apply a voltage of
The chopper / spectrometer control device 70 is connected to the MEMS mirror 26, and can apply a voltage having a predetermined period (a period corresponding to the spectroscopic period) to the wiring formed in the rotating portion 26b of the MEMS mirror 26. .
The chopper / spectrometer control device 70 is an oscillation circuit for MEMS mirror drive control, and can be achieved by a general purpose device as long as the frequency can be set.

The lock-in amplifier 80 removes a noise component from an electrical signal (measurement signal) corresponding to the intensity of light received by the photodiode 30.
The lock-in amplifier 80 is connected to the photodiode 30 and can receive a measurement signal from the photodiode 30.
The lock-in amplifier 80 is connected to the chopper / spectrometer control device 70, and a signal (reference signal) indicating the timing of the voltage applied to the wiring formed in the rotating part 51 b of the MEMS chopper member 51 by the chopper / spectrometer control device 70. ), And a signal (spectral period signal) indicating the timing of the voltage applied to the wiring formed in the rotating portion 26b of the MEMS mirror 26 can be received from the chopper / spectrometer control device 70.
The lock-in amplifier 80 generates a measurement signal (corrected measurement signal) from which noise components have been removed based on the measurement signal and the reference signal.
The lock-in amplifier 80 is achieved by a known lock-in amplifier or a circuit that exhibits an equivalent function.

Based on the intensity of light received by the photodiode 30, the data processing device 90 includes (a) a group consisting of alkanes and alkenes, and (b) an aromatic hydrocarbon among the hydrocarbons contained in the measurement target gas 1. It is an apparatus that calculates the concentration sum of hydrocarbons belonging to a group and (c) a group consisting of alkynes for each group.
The data processing device 90 includes a processing unit 91, an input unit 92, and a display unit 93.

  The processing unit 91 stores various programs and the like, expands these programs and the like, performs predetermined calculations according to these programs and the like, and stores the calculation results and the like.

The processing unit 91 may actually be configured such that a CPU, ROM, RAM, HDD, or the like is connected by a bus, or may be configured by a one-chip LSI or the like.
The processing unit 91 of the present embodiment is a dedicated product, but it can also be achieved by storing the above-described program in a commercially available personal computer or workstation.

  The processing unit 91 is connected to the lock-in amplifier 80 and can acquire (receive) the corrected measurement signal and the spectral period signal from the lock-in amplifier 80.

The processing section 91 can store information used for various calculations performed in the processing section 91, calculation results, and the like.
The processing unit 91 stores a spectrum of a reference gas (hereinafter referred to as a reference gas).
The “reference gas” is a gas that is known in advance not to absorb light in the three absorption wavelength bands of hydrocarbons contained in the measurement target gas. A specific example of the reference gas is nitrogen gas.
The “reference gas spectrum” indicates the relationship between the wavelength and the light intensity when the reference gas is irradiated with light.
In this embodiment, the wavelength band of the spectrum of the reference gas is set in a range of 2000 cm ^-1 or 4000 cm ^-1 or less in terms of wavenumber. This is to set the range to include all the absorption wavelength bands of the three groups of hydrocarbons.

  Based on the corrected measurement signal and the spectroscopic periodic signal acquired from the lock-in amplifier 80, the processing unit 91 (a) a group consisting of an alkane and an alkene, (b) a group consisting of an aromatic hydrocarbon, and (c) The absorbance in the absorption wavelength band corresponding to each group of alkynes is calculated.

The processing unit 91 collates the corrected measurement signal and the spectral periodic signal so that the acquired corrected measurement signal is (a) a group consisting of alkane and alkene, (b) a group consisting of aromatic hydrocarbons, and (c ) Specify which group of alkynes indicates the intensity of light in the wavelength band corresponding to the group.
Next, the processing unit 91 calculates the absorbance of the corresponding wavelength band by calculating the difference between the corrected measurement signal and the intensity of the corresponding wavelength band in the reference gas spectrum based on the following Equation 4.

In Equation 4, An indicates the absorbance, In indicates the intensity of light transmitted through the absorption wavelength band that is the target when the measurement target gas is irradiated with light, and (In) ₀ irradiates the reference gas with light. It refers to the intensity of light that passes through the absorption wavelength band that is the target of the measurement.

The processing unit 91 calculates the “sum of the concentrations of hydrocarbons belonging to the group consisting of alkanes and alkenes” based on “absorbance in the absorption wavelength band of hydrocarbons belonging to the group consisting of alkanes and alkenes” calculated based on Equation 4. Based on the “absorbance in the absorption wavelength band of hydrocarbons belonging to the group consisting of aromatic hydrocarbons”, the “sum of the concentrations of hydrocarbons belonging to the group consisting of aromatic hydrocarbons” is calculated, and “from alkyne Based on the “absorbance in the absorption wavelength band of hydrocarbons belonging to a certain group”, “the sum of the concentrations of hydrocarbons belonging to the group consisting of alkynes” is calculated.
Specifically, the processing unit 91 includes the measurement target gas 1 as a product of the coefficient K1 stored in the processing unit 91 in advance and “absorbance in the absorption wavelength band of hydrocarbons belonging to the group consisting of alkane and alkene”. The “sum of the concentrations of hydrocarbons belonging to the group consisting of alkanes and alkenes” is calculated.
Similarly, the processing unit 91 is included in the measurement target gas 1 as the product of the coefficient K2 stored in advance in the processing unit 91 and “absorbance in the absorption wavelength band of hydrocarbons belonging to the group consisting of aromatic hydrocarbons”. The “sum of the concentrations of hydrocarbons belonging to the group consisting of aromatic hydrocarbons” is calculated.
Similarly, the processing unit 91 obtains “from alkyne as a product of the coefficient K3 stored in the processing unit 91 in advance and“ absorbance in the absorption wavelength band of hydrocarbons belonging to the group consisting of alkyne ”. The sum of the concentrations of hydrocarbons belonging to a certain group is calculated.

  The processing unit 91 calculates the above-mentioned “sum of the concentrations of hydrocarbons belonging to the group consisting of alkanes and alkenes”, “sum of the concentrations of hydrocarbons belonging to the groups consisting of aromatic hydrocarbons”, and “groups consisting of alkynes” As the sum of the “sum of the concentrations of hydrocarbons belonging to”, “the total hydrocarbon concentration of the measurement target gas 1” is calculated.

  The processing unit 91 calculates the “sum of the concentrations of hydrocarbons belonging to the group consisting of alkanes and alkenes”, “the sum of the concentrations of hydrocarbons belonging to the groups consisting of aromatic hydrocarbons”, and “belonging to the group consisting of alkynes” “Sum of hydrocarbon concentrations” and “total hydrocarbon concentration of measurement target gas 1” are stored as appropriate.

The coefficient K1, the coefficient K2, and the coefficient K3 are obtained by measuring the gas whose hydrocarbon composition is known in advance by the FID-GC or the like with the THC measuring device 100, and the carbonization belonging to the group consisting of alkane and alkene. Calculation result of “absorbance in absorption wavelength band of hydrogen”, calculation result of “absorbance in absorption wavelength band of hydrocarbon belonging to group consisting of aromatic hydrocarbons”, and “absorption wavelength band of hydrocarbon belonging to group consisting of alkyne” It is experimentally determined based on the calculation result of “absorbance”.
In the case of the present embodiment, the sum of the concentrations of hydrocarbons belonging to each group calculated by the processing unit 91 and the total hydrocarbon concentration are calculated in the form of methane equivalent concentration values (ppmC). However, the calculation may be performed in a form such as a volume ratio.

The input unit 92 is connected to the processing unit 91, and inputs various information / instructions related to the measurement of the hydrocarbon concentration by the THC measuring device 100 to the processing unit 91.
The processing unit 91 of this embodiment is a dedicated product, but the same effect can be achieved even by using a commercially available keyboard, mouse, pointing device, button, switch, or the like.

The display unit 93 displays the input content from the input unit 92 to the processing unit 91, the calculation result (measurement result of hydrocarbon concentration) by the processing unit 91, and the like.
The display unit 93 of this embodiment is a dedicated product, but the same effect can be achieved even if a commercially available monitor, liquid crystal display, or the like is used.

As described above, the THC measuring apparatus 100 is
An infrared lamp 10 for generating light;
A spectroscope 20 for periodically changing the wavelength of light generated by the infrared lamp 10, and
A photodiode 30 for detecting the intensity of light whose wavelength has been varied by the spectroscope 20;
The light generated by the infrared lamp 10 that can be accommodated in the measurement target gas 1 and is disposed at a position sandwiched by the spectrometer 20 and the photodiode 30 in the optical path A formed by the infrared lamp 10, the spectrometer 20, and the photodiode 30. Gas container 40 capable of passing through,
An optical chopper 50 disposed in the middle of the optical path A;
Comprising
The light chopper 50
A base 51a in which an opening 51c through which light generated by the infrared lamp 10 can pass is formed, and by rotating with respect to the base 51a in accordance with a voltage application state, the "opening 51c is opened and red There is provided a rotating portion 51b that switches to either a “passing state in which light generated by the outer lamp 10 passes” or a “blocking state in which the light generated by the infrared lamp 10 is blocked by closing the opening 51c”. A MEMS chopper member 51;
A slit member 56 disposed at a position adjacent to the MEMS chopper member 51 and formed with a slit 56a for narrowing the light generated by the infrared lamp 10;
It comprises.
This configuration has the following advantages.
That is, since the S / N ratio of light detected by the photodiode 30 can be increased by the optical chopper 50, the measurement accuracy (analysis accuracy) of the THC measurement device 100 can be increased.
In addition, since the optical chopper 50 is manufactured using the MEMS technology, the size of the optical chopper 50 can be reduced, which contributes to downsizing of the THC measuring apparatus 100.
Furthermore, since the optical chopper 50 is manufactured using the MEMS technology, the chopping cycle of the optical chopper 50 can be set to a (very short) cycle of about 10 μsec to 100 μsec even when the existing technology is used. (It is possible to set the chopping frequency of the optical chopper 50 to about 10 kHz to 100 kHz), which contributes to the improvement of the high-speed response (real-time property) of the measurement by the THC measurement apparatus 100.

The MEMS chopper member 51 of the optical chopper 50 is
The light path A is disposed upstream of the slit member 56 in the optical path A of light.
With this configuration, the light blocked (reflected) by the rotating portion 51b is not reflected again by the slit member 56 and returned to the optical path A, so that the influence of disturbance light can be easily eliminated. It is possible to improve the measurement accuracy (wavelength resolution) of the THC measurement apparatus 100.

The spectroscope 20 of the THC measuring device 100 is
A grating 21 that reflects light generated by the infrared lamp 10 at different reflection angles for each wavelength;
A MEMS mirror 26 that reflects the light reflected by the grating 21 in a predetermined direction (in this embodiment, a direction incident on the second condenser lens 63);
It comprises.
With this configuration, the spectroscope 20 can be downsized.
Further, the spectral period of the spectroscope 20 can be easily shortened, which contributes to an improvement in high-speed response (real-time property) of measurement by the THC measurement apparatus 100.

Further, the chopping cycle of the MEMS chopper member 51 of the optical chopper 50 is shorter than the spectral cycle of the spectrometer 20.
With this configuration, it is possible to obtain a difference in light intensity between a state where light is blocked by the light chopper 50 and a state where light is not blocked by the light chopper 50 for each of a plurality of frequency bands. is there.

Further, at the position between the infrared lamp 10 and the spectroscope 20 in the optical path A, the first condenser lens 61 that condenses the light generated by the infrared lamp 10 and the first condenser lens 61 condenses the light. A collimating lens 62 is arranged to make the emitted light parallel light.
With this configuration, even when the infrared lamp 10 is large to some extent (when it is difficult to handle it as a point light source), it is possible to prevent ambient light from being received by the photodiode 30 while securing the light amount. This contributes to the improvement of the measurement accuracy of the THC measuring apparatus 100.

The opening 51c of the MEMS chopper member 51 and the slit 56a of the slit member 56 are
It is arranged at a position corresponding to the focal point B of light formed at a position sandwiched between the first condenser lens 61 and the collimating lens 62 in the optical path A.
With this configuration, it is possible to prevent disturbance light from being received by the photodiode 30 while securing the amount of light, which contributes to improvement in measurement accuracy of the THC measurement apparatus 100.

In the THC measuring apparatus 100 shown in FIGS. 1 and 2, the light formed at the position where the opening 51 c of the MEMS chopper member 51 and the slit 56 a of the slit member 56 are sandwiched between the first condenser lens 61 and the collimator lens 62 in the optical path A. However, the present invention is not limited to this.
As another embodiment of the position at which the opening 51c of the MEMS chopper member 51 and the slit 56a of the slit member 56 are disposed, for example, as illustrated in FIG. 3, it is disposed at a position between the collimator lens 62 and the spectroscope 20 in the optical path A. Alternatively, as shown in FIG. 4, a position sandwiched between the spectroscope 20 and the photodiode 30 in the optical path A (more precisely, a position sandwiched between the spectroscope 20 and the second condenser lens 63 in the optical path A) can be mentioned.
The embodiment shown in FIGS. 3 and 4 is common in that the opening 51c of the MEMS chopper member 51 and the slit 56a of the slit member 56 are arranged in a portion where the light is parallel light in the optical path A.
The embodiment shown in FIGS. 3 and 4 can adjust the amount of light received by the photodiode 30 by adjusting the rotation angle of the rotation part 51b of the MEMS chopper member 51, and thus the wavelength resolution can be reduced. It is possible to adjust.
In the configuration of the THC measurement apparatus 100, a trade-off relationship is established between the amount of light that passes through the opening 51c and is received by the photodiode 30, and the wavelength resolution. It is possible to easily set an optimal combination of light quantity and wavelength resolution according to the above.

Further, the THC measuring apparatus 100 is
A data processing device 90 is provided that calculates the concentration of hydrocarbons contained in the measurement target gas 1 based on the intensity of light received by the photodiode 30.
With this configuration, it is possible to calculate the concentration of hydrocarbons contained in the measurement target gas 1 in parallel with the acquisition of the detection result of the intensity of light received by the photodiode 30, and the THC measurement device This contributes to speeding up 100 measurements.

  Below, the THC measuring apparatus 200 which is 2nd embodiment of the optical analyzer which concerns on this invention using FIG. 5 is demonstrated. Note that, among members constituting the THC measurement device 200, members having the same functions as those of the THC measurement device 100 shown in FIG. 1 are assigned the same member numbers as those in FIG.

  The THC measurement device 200 includes a frame 210, an infrared lamp 10, a light receiver side optical system unit 220, a gas container 40, a chopper / spectrometer control device 70, a lock-in amplifier 80, and a data processing device 90.

The frame 210 is a structure for holding the relative positions of other members of the THC measuring apparatus 200, particularly members constituting the optical system.
The frame 210 includes a base member 211, a lamp support member 212, a container support member 213, and a unit support member 214.

  The base member 211 is a member that forms a main structure of the frame 210. Other members constituting the frame 210 are fixed to the base member 211.

  The lamp support member 212 is a member that fixes the infrared lamp 10 to the base member 211. The lower end portion of the lamp support member 212 is fixed to the base member 211, and the upper end portion of the lamp support member 212 is fixed to the infrared lamp 10.

  The container support member 213 is a member that fixes the gas container 40 to the base member 211. The lower end portion of the container support member 213 is fixed to the base member 211, and the upper end portion of the container support member 213 is fixed to the gas container 40.

  The unit support member 214 is a member that fixes the light receiver side optical system unit 220 to the base member 211. The lower end portion of the unit support member 214 is fixed to the base member 211, and the upper end portion of the unit support member 214 is fixed to the light receiver side optical system unit 220.

The light receiver side optical system unit 220 is a group of members arranged closer to the photodiode 30 than the gas container 40 in the optical system of the THC measuring device 200.
The optical receiver unit 220 includes a case 221, a first condenser lens 61, an optical chopper 50, a collimator lens 62, a spectroscope 20, a second condenser lens 63, and a photodiode 30.

The case 221 is a box-shaped member, and other members (the first condenser lens 61, the optical chopper 50, the collimator lens 62, the spectroscope 20, the second condenser lens 63, and the like constituting the light receiver side optical system unit 220). The photodiode 30) is accommodated and the relative positional relationship of the other members is maintained.
The case 221 is fixed to the base member 211 via the unit support member 214.

The THC measuring apparatus 200 shown in FIG. 5 is such that the gas container 40 is disposed at a position sandwiched between the infrared lamp 10 and the spectroscope 20 in the optical path A formed by the infrared lamp 10, the spectroscope 20 and the photodiode 30. Different from the THC measuring apparatus 100 shown in FIG.
This configuration has the following advantages.
That is, in the THC measuring apparatus 200, the light after passing through the inside of the gas container 40 is chopped by the optical chopper 50 and split by the spectroscope 20, so that the data processing apparatus 90 acquires from the lock-in amplifier 80. The corrected measurement signal excludes disturbance elements (noise) related to the measurement object including the gas container 40, and is preferable to the THC measurement apparatus 100 shown in FIG. 1 from the viewpoint of eliminating the disturbance elements.

1 Gas to be measured 10 Infrared lamp (light source)
20 Spectrometer 30 Photodiode (receiver)
40 Gas container 50 Optical chopper 51 MEMS chopper member 51a Base 51b Rotating part 51c Opening 56 Slit member 56a Slit 100 THC measuring device (optical analyzer)

Claims (15)

A light source that generates light;
A spectroscope for periodically changing the wavelength of the light generated by the light source;
A light receiver for detecting the intensity of light whose wavelength has been varied by the spectroscope;
The optical path formed by the light source, the spectroscope and the light receiver is disposed at a position sandwiched by the spectroscope and the light receiver or a position sandwiched by the light source and the spectroscope, and can accommodate a measurement target gas, and A gas container capable of transmitting light;
An optical chopper used in an optical analyzer comprising:
A base formed with an opening through which light generated by the light source can pass, and light generated by the light source by opening the opening by rotating with respect to the base corresponding to a voltage application state. A MEMS chopper member comprising a rotating portion that switches to either a passing state in which the light passes or a blocking state that blocks the light generated by the light source by closing the opening;
A slit member disposed at a position adjacent to the MEMS chopper member, and formed with a slit for narrowing the light generated by the light source;
A light chopper comprising: The MEMS chopper member is
The optical chopper according to claim 1, wherein the optical chopper is disposed upstream of the slit member in the optical path of the light. The spectrometer is
A grating that reflects the light generated by the light source at different reflection angles for each wavelength;
A MEMS mirror that reflects the light reflected by the grating in a predetermined direction;
The optical chopper of Claim 1 or Claim 2 which comprises these.   The optical chopper according to any one of claims 1 to 3, wherein a chopping period of the MEMS chopper member is shorter than a spectral period of the spectroscope.   A condensing lens that condenses the light generated by the light source and a collimator lens that collimates the light collected by the condensing lens at a position between the light source and the spectroscope in the optical path. The optical chopper as described in any one of Claim 1 to 4 arrange | positioned. The opening of the MEMS chopper member and the slit of the slit member are
The optical chopper according to claim 5, wherein the optical chopper is disposed at a position corresponding to a focal point of the light formed at a position sandwiched between the condensing lens and the collimating lens in the optical path. The opening of the MEMS chopper member and the slit of the slit member are
The optical chopper according to claim 5, wherein the optical chopper is disposed at a position between the collimator lens and the spectroscope or at a position between the spectroscope and the light receiver in the optical path. A light source that generates light;
A spectroscope for periodically changing the wavelength of the light generated by the light source;
A light receiver for detecting the intensity of light whose wavelength has been varied by the spectroscope;
The optical path formed by the light source, the spectroscope and the light receiver is disposed at a position sandwiched by the spectroscope and the light receiver or a position sandwiched by the light source and the spectroscope, and can accommodate a measurement target gas, and A gas container capable of transmitting light;
An optical chopper disposed in the middle of the optical path;
Comprising
The light chopper is
A base formed with an opening through which light generated by the light source can pass, and light generated by the light source by opening the opening by rotating with respect to the base corresponding to a voltage application state. A MEMS chopper member comprising a rotating portion that switches to either a passing state in which the light passes or a blocking state that blocks the light generated by the light source by closing the opening;
A slit member disposed at a position adjacent to the MEMS chopper member, and formed with a slit for narrowing light generated by the light source;
An optical analyzer comprising: The MEMS chopper member is
The optical analyzer according to claim 8, wherein the optical analyzer is disposed upstream of the slit member in the optical path of the light. The spectrometer is
A grating that reflects the light generated by the light source at different reflection angles for each wavelength;
A MEMS mirror that reflects the light reflected by the grating in a predetermined direction;
An optical analyzer according to claim 8 or 9, comprising:   11. The optical analyzer according to claim 8, wherein a chopping period of the MEMS chopper member is shorter than a spectral period of the spectroscope.   A condensing lens that condenses the light generated by the light source and a collimator lens that collimates the light collected by the condensing lens at a position between the light source and the spectroscope in the optical path. The optical analyzer according to any one of claims 8 to 11, which is arranged. The opening of the MEMS chopper member and the slit of the slit member are
The optical analyzer according to claim 12, wherein the optical analyzer is disposed at a position corresponding to a focal point of the light formed at a position sandwiched between the condenser lens and the collimating lens in the optical path. The opening of the MEMS chopper member and the slit of the slit member are
The optical analyzer according to claim 12, wherein the optical analyzer is disposed at a position between the collimator lens and the spectroscope or at a position between the spectroscope and the light receiver in the optical path.   The optical device according to any one of claims 8 to 14, further comprising a data processing device that calculates a concentration of a gas species contained in the measurement target gas based on an intensity of light received by the light receiver. Formula analyzer.

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