CN115468915A - Demodulation method of optical path modulation method of absorption cell - Google Patents

Demodulation method of optical path modulation method of absorption cell Download PDF

Info

Publication number
CN115468915A
CN115468915A CN202211112229.5A CN202211112229A CN115468915A CN 115468915 A CN115468915 A CN 115468915A CN 202211112229 A CN202211112229 A CN 202211112229A CN 115468915 A CN115468915 A CN 115468915A
Authority
CN
China
Prior art keywords
absorption
absorption cell
concentration
optical path
light
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Pending
Application number
CN202211112229.5A
Other languages
Chinese (zh)
Inventor
尉士民
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Individual
Original Assignee
Individual
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Individual filed Critical Individual
Priority to CN202211112229.5A priority Critical patent/CN115468915A/en
Publication of CN115468915A publication Critical patent/CN115468915A/en
Pending legal-status Critical Current

Links

Images

Classifications

    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N21/00—Investigating or analysing materials by the use of optical means, i.e. using sub-millimetre waves, infrared, visible or ultraviolet light
    • G01N21/01—Arrangements or apparatus for facilitating the optical investigation
    • G01N21/03—Cuvette constructions
    • G01N21/0303—Optical path conditioning in cuvettes, e.g. windows; adapted optical elements or systems; path modifying or adjustment
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N21/00—Investigating or analysing materials by the use of optical means, i.e. using sub-millimetre waves, infrared, visible or ultraviolet light
    • G01N21/17—Systems in which incident light is modified in accordance with the properties of the material investigated
    • G01N21/25—Colour; Spectral properties, i.e. comparison of effect of material on the light at two or more different wavelengths or wavelength bands
    • G01N21/31—Investigating relative effect of material at wavelengths characteristic of specific elements or molecules, e.g. atomic absorption spectrometry

Landscapes

  • Physics & Mathematics (AREA)
  • Spectroscopy & Molecular Physics (AREA)
  • Health & Medical Sciences (AREA)
  • Life Sciences & Earth Sciences (AREA)
  • Chemical & Material Sciences (AREA)
  • Analytical Chemistry (AREA)
  • Biochemistry (AREA)
  • General Health & Medical Sciences (AREA)
  • General Physics & Mathematics (AREA)
  • Immunology (AREA)
  • Pathology (AREA)
  • Investigating Or Analysing Materials By Optical Means (AREA)

Abstract

The invention provides a demodulation method of an optical path modulation method of an absorption cell, which comprises the following steps: the light enters an absorption cell containing an absorption medium and is received by a sensor; acquiring the light intensity change before and after the light enters the absorption cell; and calculating the concentration of the absorption medium based on the change of the light intensity and the basic parameters of the light ray and the absorption cell. According to the invention, through optical path modulation, medium absorption of short optical path and multiple reflection long optical path also contributes to a resolving result; the effect of a longer absorption cell can be achieved in the absorption cell with a smaller size through the process of optical path modulation and filtering; the stability of the signal is greatly improved through the optical path modulation technology, the anti-interference capability is enhanced, and the signal to noise ratio of the signal is improved.

Description

Demodulation method of optical path modulation method of absorption cell
Technical Field
The invention relates to the technical field of data processing, in particular to a demodulation method of an optical path modulation method of an absorption cell.
Background
In various aspects of industrial or social life, it is often necessary to measure the content or concentration of one or more components in a gaseous or liquid medium, and some are detected by two-phase flow in which one phase is dispersed in the other, and in such detection, a broad category of measures for the absorption are implemented by absorption or attenuation of electromagnetic waves or light in a specific spectrum band;
in principle, the attenuation of electromagnetic waves (light waves) through an absorption medium satisfies the lambert beer law:
I/I0＝EXP(-KCL)
in the formula, I0 is the intensity of incident light, I is the light intensity after being attenuated by a section of L optical path with the concentration of an absorption medium C, wherein K is an attenuation coefficient which is a constant related to the absorption section and the scattering section of the absorption medium, and by utilizing the principle, when the optical path is known and the extinction coefficient can be obtained by measuring the medium with known concentration, the concentration of the absorption medium is obtained by measuring the intensity of the incident light and the light intensity after being absorbed and attenuated;
various types of absorption cell structures are developed according to the principle to measure the concentration of the medium entering the absorption cell;
taking an infrared gas analyzer and an ultraviolet gas analyzer as examples, the gas to be measured is introduced into an absorption cell, light with a specific wavelength or a specific spectrum band passes through the gas to be measured, the concentration of the gas to be measured is inverted or calculated according to the absorption capacity of the specific wavelength or the specific wave band, in various application occasions, very high measurement resolution and sensitivity are required, the absorption cell cannot be too long, so that a multi-reflection optical path structure is adopted to increase the optical path of a light beam passing through the gas to be measured, thereby achieving the purpose of improving the signal-to-noise ratio or the overall resolution, along with the fact that laser is used as a light source, the collimation performance is good, the light beam is reflected in the absorption cell even for many times for dozens of times to hundreds of times, and White cells, herriott cell and the like are optical path systems designed for increasing the optical path for many times;
in all of these absorption cells at present, the optical path of a light beam through the absorption cell after one or more reflections is constant;
in the detection instrument using these types of absorption cells, calibration measurement for the zero point generally introduces gas which is not absorbed in the detected spectrum section, such as air, N2 gas and the like, into the absorption cell, and introduces measurement gas with known concentration for calibration of the full point and the span point;
the stability and accuracy of the method in the prior art are all required to be improved;
therefore, it is desirable to provide a new method for solving the above problems.
Disclosure of Invention
Aiming at the problems in the prior art, the invention provides a demodulation method of an optical path modulation method of an absorption cell.
In order to achieve the purpose, the invention adopts the following specific scheme:
the optical path in the absorption cell changes at a high speed according to a known rule, namely the optical path is modulated, the signal processing only considers the part of the optical path change, the instrument can be greatly improved from zero point or stability, and no report or realization is made on the method and concept of the optical path modulation of the absorption cell;
the above optical path configuration realizes optical path modulation of a signal, but a demodulation method is not described in detail, and such an optical path modulated signal is demodulated in the present invention.
Therefore, the temperature of the molten metal is controlled,
the invention provides a demodulation method of an optical path modulation method of an absorption cell, which comprises the following steps:
s1, receiving light rays by a sensor after the light rays enter an absorption pool containing an absorption medium;
s2, acquiring the light intensity change before and after the light enters the absorption cell;
and S3, calculating the concentration of the absorption medium based on the change of the light intensity and the basic parameters of the light and the absorption cell.
Further, step S1 specifically includes:
s11, injecting an absorption medium into an absorption pool;
s12, allowing light rays emitted by the light source to enter an absorption pool;
and S13, reflecting the light rays, and then leaving the absorption cell to be received by the sensor.
Further, step S12 includes: the light is rotated at an angular velocity.
Further, in step S13, the number of times the light is reflected in the absorption cell varies according to the angle of rotation of the light source.
Further, in step S13, the light is filtered before being received by the sensor.
Further, in step 3, the concentration of the absorption medium can be calculated by the following formula:
Figure BDA0003843967720000031
wherein:
c is the concentration of the gas to be detected;
Figure BDA0003843967720000032
is the structural constant of the instrument;
K f : the absorption coefficient;
k: the reflection coefficient of the mirror in the absorption cell;
I n : the intensity of the light beam after being reflected by the reflecting plate, wherein n is an integer;
establishing the concentration C and the measurement I n In relation between, by I n The value of C can be obtained from the measurement of (2).
Further, in step 3, the concentration of the absorption medium can be calculated by the following formula:
Figure BDA0003843967720000033
(3) In the formula (I), the compound is shown in the specification,
Figure BDA0003843967720000034
are all structural constants of the instrument, and the concentration and the measurement quantity I are established n The relationship between, by I n The value of C can be obtained by measuring;
wherein:
c is the concentration of the gas to be detected;
Figure BDA0003843967720000041
is the structural constant of the instrument;
K f : coefficient of absorption；
K: the reflection coefficient of the mirror in the absorption cell;
I n : the intensity of the light beam after being reflected by the reflecting plate, and n is an integer.
Further, in step 3,
when W/H is small, L n ≈H
The concentration of the absorption medium can be calculated by the following formula:
Figure BDA0003843967720000042
wherein:
w is the width of the absorption cell;
h is the height of the absorption cell.
Further, the absorption medium concentration is calculated in step 3 by the following formula:
Figure BDA0003843967720000043
wherein:
c (t) is the concentration of the absorption medium;
n is a positive integer, and ω t is a discrete sequence of values, the In value is measured.
Further, the absorption medium concentration is calculated in step 3 by the following formula:
Figure BDA0003843967720000044
wherein:
A. b is a test constant obtained by a standard sample with known medium concentration;
c (t): the concentration of the absorption medium;
K f : the absorption coefficient;
k: the reflection coefficient of the mirror in the absorption cell;
ω: an angular velocity;
h: the height of the absorption cell;
w: the width of the absorption cell;
I n : the intensity of the light beam after being reflected by the reflecting plate, wherein n is an integer;
the right side of the formula is the measurement parameter and the structural parameter, and the light intensity I is passed n C (t), i.e. the absorption medium concentration, can be calculated.
By adopting the technical scheme of the invention, the invention has the following beneficial effects:
1. medium absorption of short optical path and multiple reflection long optical path also contributes to a resolving result through optical path modulation;
2. the effect of a longer absorption cell can be achieved in the absorption cell with a smaller size through the processes of optical path modulation and filtering;
3. the stability of the signal is greatly improved through the optical path modulation technology, the anti-interference capability is enhanced, and the signal to noise ratio of the signal is improved.
Drawings
FIG. 1 is a schematic structural view of the present invention;
FIG. 2 is a flow chart of the present invention;
fig. 3 shows a specific step of step S1.
In the figure: 1. rotating the reflector; 2. a photoelectric receiver; 3. a window; 4. a left reflector; 5. a light source; 6. an absorption tank; 7. a right reflector.
Detailed Description
The present invention will be described in further detail with reference to the accompanying drawings and examples. It is to be understood that the specific embodiments described herein are merely illustrative of the invention and are not limiting of the invention. It should be further noted that, for the convenience of description, only some but not all of the elements associated with the present invention are shown in the drawings.
As shown in fig. 1 to 3, the present invention provides a demodulation method of an optical path modulation method of an absorption cell, comprising the following steps:
s1, receiving light rays by a sensor after the light rays enter an absorption pool containing an absorption medium;
s2, acquiring the light intensity change before and after the light enters the absorption cell;
and S3, calculating the concentration of the absorption medium based on the change of the light intensity and the basic parameters of the light and the absorption cell.
The step S1 specifically includes:
s11, injecting an absorption medium into the absorption pool;
s12, allowing light rays emitted by a light source to enter an absorption pool;
and S13, reflecting the light rays, then leaving the absorption cell, and receiving the light rays by the sensor.
Step S12 includes: the light is rotated at an angular velocity.
In step S13, the number of times the light is reflected in the absorption cell varies according to the angle of rotation of the light source.
In step S13, the light is filtered before being received by the sensor.
FIG. 1 is analyzed as a basic structure;
in the figure: 1. rotating the reflector; 2. a photoelectric receiver; 3. a window; 4. a left reflector; 5. a light source; 6. an absorption tank; 7. a right reflector;
the rotating mirror 1 may be a prism with multiple reflecting surfaces, when the rotating mirror 1 rotates at an angular velocity ω, the light beam is reflected between the left mirror 4 and the right mirror 7 multiple times due to the change of the incident angle, and when each reflecting surface rotates, the light beam is reflected once, from 2 times to N times alternately due to the change of the incident angle and is received by the photoelectric receiver 2 to form an alternate periodic signal, in and Jn (N =1,2, 8230;) marked In fig. 1 are intensities of the light beam after reflection and medium absorption.
When the concentration of an absorption medium in the absorption cell is C, the absorption coefficient Kf is obtained; the reflection coefficients of the left and right reflectors are K, the generality is not lost, the absorption of the window is neglected, and the reflection coefficients of the reflectors are assumed to be the same in the process, so that the reflection coefficients can be obtained according to the Lambert beer law and the reflection law:
wherein:
I n : the intensity of the beam after reflection (of a corresponding number of times);
J n : the intensity after absorption by the medium (corresponding to the number of times);
n =1,2, \8230; (number of reflections n);
when in the absorption tank:
c: the concentration of the absorption medium;
K f : the absorption coefficient;
k: the reflection coefficients of the left and right mirrors;
then from the lambert beer law and the reflection law:
when the rotating mirror is just rotated to be reflected once:
Figure BDA0003843967720000071
when the rotating mirror is just rotated to be reflected 2 times:
Figure BDA0003843967720000072
when the rotating mirror is just rotated and reflected n times:
Figure BDA0003843967720000073
Figure BDA0003843967720000074
(2) In the formula (I), the compound is shown in the specification,
Figure BDA0003843967720000075
is a structural constant of the instrument and is,
in this way, the concentration C and the measured quantity I are established n The relationship between, by I n The value of C can be obtained from the measurement of (2).
When the value of n is smaller in a rotation period, the measurement of higher concentration can be corresponded, when the value of n is larger, the measurement of lower concentration can be corresponded, and after the absorption light intensity of different gases is measured by adopting the filtering wheel, the measurement of high concentration, low concentration and different gas concentrations can be realized in the same chamber.
By:
Figure BDA0003843967720000081
obtaining by taking logarithm sorting:
Figure BDA0003843967720000082
(3) In the formula (I), the compound is shown in the specification,
Figure BDA0003843967720000083
are all structural constants of the instrument, the concentration and the measured quantity I are established n The relationship between, by I n The value of C can be obtained from the measurement of (2).
When the reflection times in a rotation period are smaller than the value of n, the measurement of higher concentration can be corresponded, when the value of n is larger, the measurement of lower concentration can be corresponded, and after the absorption light intensity of different gases is measured by adopting the filtering wheel, the measurement of high concentration, low concentration and different gas concentrations can be realized in the same chamber.
Of course, by
Figure BDA0003843967720000084
Wherein m is an integer less than n and represents different reflection times
It is possible to obtain:
Figure BDA0003843967720000085
for the variant of equation (2):
Figure BDA0003843967720000091
taking an accumulated value:
Figure BDA0003843967720000092
then:
Figure BDA0003843967720000093
when W/H is small, L n H, then equation 4 can be simplified as:
Figure BDA0003843967720000094
also the accumulated value can be obtained by the formula 3 deformation:
Figure BDA0003843967720000095
when W/H is small, L n H, then equation 6 can be simplified as:
Figure BDA0003843967720000096
in the above formulas 2 to 8, the left side is the concentration to be measured, and the right term includes two values, namely, the light intensity of the light source beam and the light intensity value after multiple reflections and absorptions of the measurement chamber, and the structural physical property parameter; the former is a value to be measured, and the concentration of the measured medium can be obtained by measuring the light intensity of the light beam.
Alternatively, when the angular velocity of the rotating mirror is ω (not generally, the initial angular angle is zero):
W 0 ＝tan(ωt)*H (9)
Figure BDA0003843967720000097
when n is an integer, or when W is an integer multiple of W0, the photoelectric sensor can receive the light intensity signal
Figure BDA0003843967720000098
Substituting the formulas 9, 10 and 11 into the formula 2, and finishing:
Figure BDA0003843967720000101
wherein:
c (t) is the concentration of the absorption medium;
in equation (12), n is defined as an integer, meaning that ω t can only take a discrete sequence of values, at which time the In value can be measured.
This produces a sequence of I0, I1, \8230in, corresponding to each cycle of the rotating mirror.
Although practically impossible to measure, the values between the sequences can be obtained by difference, fitting, or even signal retention methods, and the intermediate values obtained by this method can introduce some deviation when applied to equation (12), but can be limited to a certain range by calibration, noise reduction, and other measures in engineering practice. In this way, the equation (6) can provide a continuous functional relationship in the engineering sense. When the formula (12) is examined, the concentration of the medium is represented on the left side, kf on the right side is the physical property parameter of the medium, K is the reflectivity of the mirror, and the angular velocity ω is the design value, I0, I1, \ 8230, in is the measured value or the intermediate value obtained by calculation from the measured value. From this equation, the concentration value of the medium can be derived from the measured values.
In equation (12), the two terms on the right can be regarded as the superposition of two signals modulated by cos (ω t) and sin (ω t), with fundamental frequencies of
Figure BDA0003843967720000102
Left side of formula (6)The side C (t) is generally a time-varying value, which in practice is itself a relatively slowly varying signal, which in construction can be such that
Figure BDA0003843967720000103
Is much larger than the fundamental frequency of the C (t) signal, so that the noise part on the right side of the equation (6) is filtered out by low-pass filtering while the C (t) on the left side is kept unchanged, and of course, the engineering filtering process will cause the attenuation of the value on the right side of the equation (12), which can be corrected by the calibration correction method.
If the sign LP { } is used to denote such filtering, then equation (6) can be rewritten as:
Figure BDA0003843967720000104
in the formula (7), the compound represented by the formula,
Figure BDA0003843967720000111
after low-pass filtering, constants associated with the media properties, reflectivity, and structural parameters, then equation (12) can be written as follows:
Figure BDA0003843967720000112
(14) In the formula, A and B are test constants and can be obtained by a standard sample with known medium concentration, and the right side of the formula is a measurement parameter and a structural parameter, so that the medium concentration can also be obtained by the above formula.
The above description is only a preferred embodiment of the present invention, and is not intended to limit the scope of the present invention, and all modifications and equivalents of the present invention, which are made by the contents of the present specification and the accompanying drawings, or directly/indirectly applied to other related technical fields, are included in the scope of the present invention.

Claims (10)

1. A demodulation method of an optical path modulation method of an absorption cell is characterized by comprising the following steps:
s1, receiving light rays by a sensor after the light rays enter an absorption pool containing an absorption medium;
s2, acquiring the light intensity change before and after the light enters the absorption cell;
and S3, calculating the concentration of the absorption medium based on the change of the light intensity and the basic parameters of the light and the absorption cell.
2. The method for demodulating the optical path length modulation method of the absorption cell according to claim 1, wherein the step S1 specifically includes:
s11, injecting an absorption medium into the absorption pool;
s12, allowing light rays emitted by the light source to enter an absorption pool;
and S13, reflecting the light rays, then leaving the absorption cell, and receiving the light rays by the sensor.
3. The demodulation method of the optical path modulation method of the absorption cell according to claim 2, wherein the step S12 includes: the light is rotated at an angular velocity.
4. The method for demodulating an optical path length modulation method for an absorption cell according to claim 2, wherein in step S13, the number of times the light is reflected in the absorption cell changes according to the angle of rotation of the light source.
5. The method for demodulating an optical path length modulation method of an absorption cell according to claim 1, wherein in step S13, the light is filtered before being received by the sensor.
6. The demodulation method of the optical path modulation method of an absorption cell according to claim 1, wherein the concentration of the absorption medium is calculated in step 3 by the following formula:
Figure FDA0003843967710000011
wherein:
c is the concentration of the gas to be detected;
Figure FDA0003843967710000021
is the structural constant of the instrument;
K f : the absorption coefficient;
k: the reflection coefficient of the mirror in the absorption cell;
I n : the intensity of the light beam after being reflected by the reflecting plate, n is an integer;
establishing the concentration C and the measurement I n In relation between, by I n The measurement of (2) gives the value of C.
7. The demodulation method of the optical path modulation method of an absorption cell according to claim 1, wherein the concentration of the absorption medium is calculated in step 3 by the following formula:
Figure FDA0003843967710000022
(3) In the formula
Figure FDA0003843967710000023
Are all structural constants of the instrument, the concentration and the measured quantity I are established n In relation between, by I n The measurement of (2) yields the value of C;
wherein:
c is the concentration of the gas to be detected;
Figure FDA0003843967710000024
is the structural constant of the instrument;
K f : the absorption coefficient;
k: the reflection coefficient of the mirror in the absorption cell;
I n : the intensity of the light beam after being reflected by the reflecting plateThe degree of the magnetic field is measured, n is an integer.
8. The demodulation method of the optical path modulation method of an absorption cell according to claim 1, wherein, in step 3,
when W/H is small, L n ≈H
The concentration of the absorption medium is calculated by the following formula:
Figure FDA0003843967710000025
wherein:
w is the width of the absorption cell;
h is the height of the absorption cell.
9. The demodulation method for the optical path length modulation method of an absorption cell according to claim 1, wherein the concentration of the absorption medium is calculated in step 3 by the following formula:
Figure FDA0003843967710000031
wherein:
c (t) is the concentration of the absorption medium;
n is a positive integer, and ω t is a discrete sequence of values, the In value is measured.
10. The demodulation method for the optical path length modulation method of an absorption cell according to claim 1, wherein the concentration of the absorption medium is calculated in step 3 by the following formula:
Figure FDA0003843967710000032
wherein:
A. b is a test constant obtained by a standard sample with known medium concentration;
c (t): the concentration of the absorption medium;
K f : the absorption coefficient;
k: the reflection coefficient of the mirror in the absorption cell;
ω: an angular velocity;
h: the height of the absorption cell;
w: the width of the absorption cell;
I n : the intensity of the light beam after being reflected by the reflecting plate, n is an integer;
the right side of the formula is the measurement parameter and the structural parameter, and the light intensity I is passed n C (t) is calculated as the concentration of the absorption medium.
CN202211112229.5A 2022-09-13 2022-09-13 Demodulation method of optical path modulation method of absorption cell Pending CN115468915A (en)

Priority Applications (1)

Application Number Priority Date Filing Date Title
CN202211112229.5A CN115468915A (en) 2022-09-13 2022-09-13 Demodulation method of optical path modulation method of absorption cell

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
CN202211112229.5A CN115468915A (en) 2022-09-13 2022-09-13 Demodulation method of optical path modulation method of absorption cell

Publications (1)

Publication Number Publication Date
CN115468915A true CN115468915A (en) 2022-12-13

Family

ID=84333922

Family Applications (1)

Application Number Title Priority Date Filing Date
CN202211112229.5A Pending CN115468915A (en) 2022-09-13 2022-09-13 Demodulation method of optical path modulation method of absorption cell

Country Status (1)

Country Link
CN (1) CN115468915A (en)

Similar Documents

Publication Publication Date Title
US6603555B1 (en) Gas detecting apparatus using laser absorption spectroscopy
Schiff et al. Tunable diode laser systems for measuring trace gases in tropospheric air
Nylander et al. Gas detection by means of surface plasmon resonance
US8842282B2 (en) Optical reflectors for spectrometer gas cells
US5445964A (en) Dynamic engine oil and fuel consumption measurements using tunable diode laser spectroscopy
CN100561192C (en) Multicomponent gas concentration quantitative analysis method based on the realization of AOTF near infrared spectrometer
US6639678B1 (en) Apparatus and method for nondestructive monitoring of gases in sealed containers
CA3025935A1 (en) Photothermal interferometry apparatus and method
CN103398964A (en) Gas detection method based on cavity enhancement technique
US5387971A (en) Method and apparatus for measuring concentration of a solution using pathlength complementally modulated cells
US10488258B2 (en) Optical reflectors for spectrometer gas cells
Janssen et al. Multi-spectral investigation of ozone: Part I. Setup & uncertainty budget
Li et al. Mid-infrared telemetry sensor based calibration gas cell for CO detection using a laser wavelength locking technique
CN204359673U (en) The regulating device that laser gas analyzer device collimates
CN115468915A (en) Demodulation method of optical path modulation method of absorption cell
CN105158184A (en) Gas online analysis device based on optical integrating sphere
WO2020173048A1 (en) Laser spectrum analysis apparatus and method for fluid
Evans et al. Experimental and theoretical model of refractive index artifacts in absorbance detection
CN113758877B (en) Frequency domain quantum weak measurement biomolecular sensor and measurement method thereof
Dewey Design of optoacoustic systems
US7126685B1 (en) Optical absorbance sensitivity and reliability improvement via rotation of sample container
JPH07502344A (en) Reflection-free polarimetry system for small volume sample cells
JP4685915B2 (en) NDIR photometer for measuring multiple components
CN115436291A (en) Optical path modulation absorption pool
JPH0585020B2 (en)

Legal Events

Date Code Title Description
PB01 Publication
PB01 Publication
SE01 Entry into force of request for substantive examination
SE01 Entry into force of request for substantive examination