CN109211837B - Complex refractive index measuring method of liquid absorption medium - Google Patents
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Abstract
The invention relates to a complex refractive index measuring method of a liquid absorption medium, which comprises the following steps of firstly providing a split absorption liquid medium sample; then, enabling the light source to select a proper incidence point to be incident on the medium interface, enabling the refracted light to finally reach a set point, and simultaneously recording the proper incidence point position; and finally, calculating the complex refractive index of the liquid absorption medium to be detected according to a time minimum principle and the established relation between the real refraction angle of the wedge-shaped absorption liquid medium and the real part and the imaginary part of the complex refractive index of the absorption liquid medium. The invention has simple measurement, few required components, simple optical path and low cost of the manufactured instrument.
Description
Technical Field
The invention relates to the field of complex refractive index measurement, in particular to a complex refractive index measurement method of a liquid absorption medium.
Background
For the refractive index of the absorption medium, its value is characterized by the complex refractive index. This change in form also changes the properties of the wave, particularly the imaginary refractive index, not only being a source of the absorption characteristics of the medium, but also affecting the polarization state of the reflected or transmitted light. The research on complex refractive index not only has theoretical significance, but also has practical application value, and the refractive index of some liquid is often required to be measured in industrial departments such as chemical industry, medicine, food, petroleum and the like and in the teaching and experiments of colleges and universities, and the liquid is not a transparent medium in many cases. Therefore, the method can accurately measure the refractive index of the absorptive liquid medium, and has very important practical significance.
The existing measuring method of complex refractive index is mainly a polarization technology, incident linearly polarized light is changed into elliptically polarized light after being reflected by an absorptive medium, and the real part and the imaginary part of the complex refractive index are measured by measuring the phase and the amplitude of the reflected light, so that the principle is complex, more components are needed for completing the measurement, the optical path is complex, and the price of the existing instrument is high.
Disclosure of Invention
In view of this, the present invention provides a method for measuring complex refractive index of a liquid absorption medium, which has the advantages of simple measurement, few required components, simple optical path and low cost of the instrument.
The invention is realized by adopting the following scheme: a method of measuring the complex refractive index of a liquid absorbing medium comprising the steps of:
step S1: providing a cleaved sample of the liquid absorbing medium;
step S2: enabling a light source to select a proper incidence point to be incident on a medium interface, enabling refracted light to finally reach a set point, and recording the proper incidence point position;
step S3: and calculating the complex refractive index of the liquid absorption medium to be measured according to the time minimum principle and the established relation between the real refraction angle of the wedge-shaped absorption liquid medium and the real part and the imaginary part of the complex refractive index of the absorption liquid medium.
Further, in step S1, the cleaved absorption liquid medium sample is placed in a rectangular transparent container, wherein an inclined plane having an included angle α with the horizontal plane is disposed inside the rectangular transparent container, and the inclined plane and the peripheral wall of the container form a cleaved cavity for holding the absorption liquid medium sample, so that the upper surface of the absorption liquid is a right-angle edge of the cleaved shape.
Further, step S2 is specifically: selecting laser as a light source, vertically irradiating the right-angle side of a split absorption liquid medium sample with the laser, moving the light source left and right, selecting a proper incident point O point on a liquid absorption medium interface to be measured, enabling the refracted light to finally reach a set point B point through a point C on the wall of the cavity, measuring the distance L from the incident point O point to one wall of the container, wherein the distance from the wall to the point B is H, the distance from the wall to the other wall parallel to the wall is m, and the distance from the bottom of the container to the plane of the incident point is S.
Further, the step S3 is specifically:
step S31: establishing the relationship between the real refraction angle and the complex refractive index of the absorption liquid medium:
wherein n represents the real part of the complex refractive index of the absorption liquid medium to be measured, κ represents the imaginary part of the complex refractive index of the absorption liquid medium to be measured, and niWhich represents the refractive index of the container,
represents the real angle of refraction to air;
step S32: according to the minimum time principle, a calculation formula of the real part of the refractive index of the absorption liquid medium to be detected is established:
step S33: and combining the relation between the real refraction angle and the complex refractive index of the absorption liquid medium to obtain the imaginary part of the complex refractive index of the absorption liquid medium to be detected as follows:
compared with the prior art, the invention has the following beneficial effects: the method only needs to make the light incident from the known point, selects the proper incident point on the medium interface, makes the refracted light finally reach the set point, only needs to measure the position of the human-irradiated point, and can calculate the refractive index of the medium according to the relation between the real refraction angle of the light passing through the wedge-shaped liquid absorption medium and the real part and the imaginary part of the complex refractive index of the absorption liquid medium, the measurement is simple, the needed components are few, the optical path is simple, and the cost of the instrument is low.
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FIG. 1 is a complex refractive index measurement optical path diagram of a liquid absorbing medium according to an embodiment of the present invention.
Fig. 2 is a schematic diagram of the light path of light through an absorbing medium according to an embodiment of the present invention.
Detailed Description
The invention is further explained below with reference to the drawings and the embodiments.
It should be noted that the following detailed description is exemplary and is intended to provide further explanation of the disclosure. Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs.
It is noted that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of example embodiments according to the present application. As used herein, the singular forms "a", "an" and "the" are intended to include the plural forms as well, and it should be understood that when the terms "comprises" and/or "comprising" are used in this specification, they specify the presence of stated features, steps, operations, devices, components, and/or combinations thereof, unless the context clearly indicates otherwise.
The embodiment provides a complex refractive index measuring method of a liquid absorption medium, which comprises the following steps:
step S1: providing a cleaved sample of the liquid absorbing medium;
step S2: enabling a light source to select a proper incidence point to be incident on a medium interface, enabling refracted light to finally reach a set point, and recording the proper incidence point position;
step S3: and calculating the complex refractive index of the liquid absorption medium to be measured according to the time minimum principle and the established relation between the real refraction angle of the wedge-shaped absorption liquid medium and the real part and the imaginary part of the complex refractive index of the absorption liquid medium.
In this embodiment, in step S1, the cleaved absorption liquid medium sample is placed in a rectangular transparent container, wherein an inclined plane having an included angle α with a horizontal plane is disposed inside the rectangular transparent container, and the inclined plane and the peripheral wall of the container form a cleaved cavity for containing the absorption liquid medium sample, so that the upper surface of the absorption liquid is a right-angle edge of the cleaved shape.
In this embodiment, step S2 specifically includes: selecting laser as a light source, vertically irradiating the right-angle side of a split absorption liquid medium sample with the laser, moving the light source left and right, selecting a proper incident point O point on a liquid absorption medium interface to be measured, enabling the refracted light to finally reach a set point B point through a point C on the wall of the cavity, measuring the distance L from the incident point O point to one wall of the container, wherein the distance from the wall to the point B is H, the distance from the wall to the other wall parallel to the wall is m, and the distance from the bottom of the container to the plane of the incident point is S.
In this embodiment, the step S3 specifically includes:
step S31: establishing the relationship between the real refraction angle and the complex refractive index of the absorption liquid medium:
wherein n represents the real part of the complex refractive index of the absorption liquid medium to be measured, κ represents the imaginary part of the complex refractive index of the absorption liquid medium to be measured, and niWhich represents the refractive index of the container,
represents the real angle of refraction to air;
step S32: according to the minimum time principle, a calculation formula of the real part of the refractive index of the absorption liquid medium to be detected is established:
step S33: and combining the relation between the real refraction angle and the complex refractive index of the absorption liquid medium to obtain the imaginary part of the complex refractive index of the absorption liquid medium to be detected as follows:
as shown in fig. 1, in this embodiment, a laser is vertically incident on a right-angle side of a cleft-shaped absorption liquid medium sample, a light source is moved left and right, a suitable incident point O is selected on a liquid absorption medium interface to be measured, finally, refracted light passes through a point C and finally reaches a set point B, and a distance L from the point O to a container wall is measured. A. O, C, B, the container has a bottom QW distance m, a liquid level QU distance S, a liquid level QB distance H, and an inclined surface with an angle α inside the container, as shown in fig. 1. According to the minimum time principle and the established relation between the real refraction angle of the wedge-shaped liquid absorption medium and the real part and the imaginary part of the complex refractive index of the absorption liquid medium, the complex refractive index of the liquid absorption medium to be detected can be calculated.
In the present embodiment, the relationship between the real refraction angle and the complex refractive index of the absorbing medium is specifically obtained as follows:
converting light wave E (r, t) to E (r) E-iωt，H(r,t)＝H(r)e-iωtThe following equation of the light wave in the absorption medium can be obtained instead of the Maxwell equation:
in the formula (I), the compound is shown in the specification,
is equivalent complex permittivity, is permittivity, mu is permeability, sigma is conductivity,
is the complex refractive index of the absorbing medium, n, k are the real and imaginary parts of the absorbing medium, respectively0Is a wave vector in the vacuum and,
the unit vectors of the isoamplitude and the isophase plane are q and s respectively as complex wave vectors in the absorptive medium, and the included angle between the two unit vectors is xi to cos-1(q.s)，ksAnd kqRespectively, the phase constant of the wave (reflecting the propagation of the wave) and the attenuation constant (reflecting the amplitude variation of the wave).
The relationship between the phase constant and the attenuation constant in the absorbing medium and the real part and the imaginary part of the complex refractive index is as follows:
since n and k are not zero, it can be seen from the above formula that ξ ≠ π/2, i.e., the two unit vectors are not perpendicular.
Parameter Ns，NqThey are regarded as effective refractive indices for light to propagate and attenuate in an absorbing medium, their magnitude being related not only to the complex refractive index but also to the angle between the iso-surface and the iso-surface.
When light is vertically incident from the air to the right-angle side of the wedge-shaped absorptive medium with the vertical angle α, as shown in fig. 2, at the interface 1, because light is vertically incident, the light wave after entering the absorptive medium is known according to the boundary conditions:
the absorption medium is refracted into the container medium at the interface 2, so that the refractive index of the container is niThe real angle of refraction to air is
From the boundary conditions, it is found that the phase vector and the attenuation vector of the wave in the absorptive medium have tangential components at the interface, and therefore the phase constant k 'of the refracted wave'sAttenuation constant k'qThe relationship between them is as follows:
meanwhile, according to the boundary conditions, it is possible to obtain:
from the above four equations, the relationship of the real angle of refraction to the real and imaginary parts of the complex refractive index of the absorbing liquid medium can be obtained as follows:
preferably, in this embodiment, the calculation relationship of the refractive index of the medium to be measured is established according to the minimum time principle as follows:
from the point O to the point B, the time required for the light to go from the point O to the point B can be obtained by the relationship given in fig. 1:
let the distance of DC be x, which is derived from the geometric relationship:
substituting this formula into the preceding formula yields:
according to the minimum time principle, if the time is used for the minimum time, the following conditions are met:
substituting the formula into the formula can obtain:
referring to fig. 2 again, the light passes through point C from point O to point B, and it can be seen that:
x＝Lsinαtanα；
substituting the formula into the formula can obtain a real part expression of the complex refractive index as follows;
meanwhile, according to the geometrical relationship, the real refraction angle is as follows:
finally, the imaginary part of the complex refractive index of the medium to be measured is obtained as follows:
the above description is only a preferred embodiment of the present invention, and all equivalent changes and modifications made in accordance with the claims of the present invention should be covered by the present invention.
Claims (1)
1. A complex refractive index measurement method of a liquid absorption medium is characterized in that: the method comprises the following steps:
step S1: providing a cleaved sample of the liquid absorbing medium;
step S2: enabling a light source to select a proper incidence point to be incident on a medium interface, enabling refracted light to finally reach a set point, and recording the proper incidence point position;
step S3: calculating the complex refractive index of the liquid absorption medium to be detected according to a time minimum principle and the established relation between the real refraction angle of the wedge-shaped absorption liquid medium and the real part and the imaginary part of the complex refractive index of the absorption liquid medium;
in step S1, the cleaved absorption liquid medium sample is placed in a rectangular transparent container, wherein an inclined plane having an angle α with the horizontal plane is disposed inside the rectangular transparent container, and the inclined plane and the peripheral wall of the container form a cleaved cavity for holding the absorption liquid medium sample, so that the upper surface of the absorption liquid is a cleaved right-angle side;
wherein, step S2 specifically includes: selecting laser as a light source, vertically irradiating the right-angle side of a split absorption liquid medium sample with the laser, moving the light source left and right, selecting a proper incident point O point on a liquid absorption medium interface to be detected, enabling the refracted light to pass through a point C on the wall of the cavity and finally reach a set point B, measuring the distance L from the incident point O point to one wall of the container, wherein the distance from the wall to the point B is H, the distance from the wall to the other wall parallel to the wall is m, and the distance from the bottom of the container to the plane of the incident point is S;
wherein, the step S3 specifically includes:
step S31: establishing the relationship between the real refraction angle and the complex refractive index of the absorption liquid medium:
wherein n represents the real part of the complex refractive index of the absorption liquid medium to be measured, κ represents the imaginary part of the complex refractive index of the absorption liquid medium to be measured, and niWhich represents the refractive index of the container,
represents the real angle of refraction to air;
step S32: according to the minimum time principle, a calculation formula of the real part of the refractive index of the absorption liquid medium to be detected is established:
step S33: and combining the relation between the real refraction angle and the complex refractive index of the absorption liquid medium to obtain the imaginary part of the complex refractive index of the absorption liquid medium to be detected as follows:
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