Determination method for determining linear optical effect of soft substance through light transmittance

Abstract

The invention relates to the technical field of material property measurement, and discloses a method for measuring the linear optical effect of a soft substance through light transmittance, which comprises the following steps of: 1, irradiating a soft substance sample with optical anisotropy by using circularly polarized light; 2, the light transmittance change of the circularly polarized light penetrating through the sample is measured and recorded as a T-theta curve, and the T-theta curve reflects the optical axis orientation, the dichroism and the birefringence effect of the sample; and 3, directly determining the optical axis orientation angle phi of the sample by analyzing the T-theta curve, and further calculating the dichroism delta kappa and the birefringence effect delta n of the sample. The Si-photodiode detector subjected to nonlinear correction processing can ensure high accuracy of transmittance measurement, especially in a measurement environment with a high dynamic range, meanwhile, the ellipticity and angular distribution of circularly polarized light are adjusted through the light source correction module, the influence of light source inconsistency is eliminated, and the measurement accuracy is improved. Therefore, the consistency and repeatability of experimental data are improved.

Description

Technical Field

[0001] The invention relates to the technical field of material property measurement, and in particular to a method for measuring the linear optical effect of soft matter by light transmittance. Background Art

[0002] Soft matter is a substance between solid and ideal fluid, such as magnetic colloids and liquid crystals. The optical effect of a substance refers to its response to a light field. The measurement of the optical effect of anisotropic media can not only reveal the important macroscopic properties of the substance, but also is an important tool for revealing the structure of the substance. The so-called linear optical effect refers to the optical effect that is independent of the intensity of the incident light, mainly dichroism and birefringence effects. When light propagates in an anisotropic medium along a certain direction, if it propagates in an isotropic medium, this direction is called the optical axis. The optical axis of liquid crystal is the director of the liquid crystal molecule, and the optical axis of magnetic colloid is the direction of the external magnetic field.

[0003] Complex dielectric constant can be used To describe the optical properties of a medium. Dielectric constants parallel and perpendicular to the optical axis and Can be expressed as:

[0004]

[0005] The real number part n || and n ⊥ are the refractive indexes parallel to and perpendicular to the optical axis, respectively, and the imaginary part κ || and κ ⊥ are the extinction coefficients parallel to and perpendicular to the optical axis, respectively. When linearly polarized light passes through a medium perpendicular to the optical axis, the polarization vector (i.e., the electric vector of light) parallel to the optical axis is e-light (extraordinary light), and the polarization vector perpendicular to the optical axis is o-light (ordinary light). If the extinction coefficients of linearly polarized light parallel to and perpendicular to the optical axis of the medium are different, it is called dichroism, which can be expressed as:

[0006] Δκ=κ || -κ ⊥ =λ2α d l / 4πl (2)

[0007] Where λ is the wavelength of the incident light, l is the sample thickness, and α d =(α || -α ⊥ ) / 2,α || and α ⊥ are the absorption coefficients of incident light with polarization directions parallel and perpendicular to the optical axis of the medium passing through the sample, 2α d l is the absorbance difference, which is a measurable quantity.

[0008] If the refractive index of linear polarized light parallel to and perpendicular to the optical axis is different, it is called the birefringence effect, which can be expressed as:

[0009]

[0010] Where δ is the phase difference between the incident light with polarization directions perpendicular and parallel to the optical axis of the medium after passing through the medium.

[0011] Circularly polarized light can be regarded as having the same amplitude A (A) when the polarization direction is parallel to the medium optical axis and perpendicular to the medium optical axis. || =A ⊥ ) and the synthesis of two linearly polarized beams with a phase difference of ±π / 2, the electric vector E || and E ⊥ Can be expressed as:

[0012]

[0013] Where ω is the circular frequency, t is the time, a positive sign before π / 2 corresponds to right-handed (i.e., facing the direction of light propagation, the electric vector rotates clockwise) circularly polarized light, and a negative sign before π / 2 corresponds to left-handed (i.e., facing the direction of light propagation, the electric vector rotates counterclockwise) circularly polarized light. The distribution of the intensity of circularly polarized light with angle θ, I(θ), is a constant, namely, I0 is the total light intensity. When circularly polarized light passes through a medium, (1) due to dichroism, absorption anisotropy will occur, causing the amplitudes of the two perpendicular linear polarized lights to change, i.e., A || ≠A ⊥ ; (2) Due to the birefringence effect, the phase difference between the two linearly polarized lights changes. This change can be represented by the phase increase of the linearly polarized light vibrating in the direction perpendicular to the optical axis. Thus, the transmitted light becomes elliptically polarized light, which can be expressed as:

[0014]

[0015] In the formula, α || and α ⊥ are the absorption coefficients of linearly polarized light with polarization directions along the optical axis of the medium and perpendicular to the optical axis of the medium respectively; δ=(n || -n ⊥ )·2πl / λ,n || and n ⊥ are the refractive indices of the polarization direction along the optical axis of the medium and perpendicular to the optical axis of the medium. The distribution of the light intensity of elliptically polarized light with angle θ is I(θ), and there is a maximum value I max and minimum value I min , that is I min <I(θ)<I max .

[0016] Soft matter structures are temperature sensitive, and their optical axis orientation is usually difficult to accurately determine. In existing methods for measuring the linear optical effects of optical materials, the optical axis orientation of the material is required to be a known quantity, and the birefringence effect and dichroism are measured separately. In addition, for materials with very low absorption, it is difficult to measure their dichroism with existing methods. Summary of the invention

[0017] In view of the shortcomings of the prior art, the present invention provides a method for measuring the linear optical effect of soft matter by transmittance, which solves the problem that it is difficult to measure the dichroism of materials with very small absorption in the existing linear optical effect measurement methods of optical materials.

[0018] To achieve the above object, the present invention is implemented by the following technical scheme: A method for measuring the linear optical effect of soft matter by light transmittance, comprising the following steps:

[0019] Step 1: Irradiate the optically anisotropic soft matter sample with circularly polarized light;

[0020] Step 2, measuring the transmittance change of circularly polarized light passing through the sample and recording it as a T-θ curve, wherein the T-θ curve reflects the optical axis orientation, dichroism and birefringence effect of the sample;

[0021] Step 3, directly determine the optical axis orientation angle φ of the sample by analyzing the T-θ curve, and further calculate the dichroism Δκ and birefringence effect Δn of the sample;

[0022] Step 4, using a Si-photodiode detector that has been processed for nonlinear correction to measure the T-θ curve;

[0023] Step 5: Apply the reduced incident light source correction technology to optimize the quality of circularly polarized light and ensure measurement accuracy.

[0024] Preferably, the optical axis orientation angle φ of the sample is determined based on symmetry analysis of T-θ curves measured by left-handed and right-handed circular light, which symmetry analysis involves identifying two maxima and two minima on the curve to determine the optical axis orientation angle of the sample.

[0025] Preferably, the dichroism Δκ is the absorbance difference 2α obtained by calculating the T-θ curve d l is obtained, the absorbance difference is 2α d l reflects the absorption characteristics of the sample to polarized light in different directions.

[0026] Preferably, the birefringence effect Δn is determined by calculating the phase difference δ obtained by the T-θ curve, and the phase difference δ represents the difference in refractive index of the sample to different directions of polarized light.

[0027] Preferably, the circularly polarized light source is equipped with an adjustable power controller for adjusting the intensity of the incident light to adapt to samples with different absorption rates, thereby optimizing the dynamic range and precision of transmittance measurement.

[0028] A device for measuring the linear optical effect of soft matter by light transmittance, comprising:

[0029] A light source that produces circularly polarized light;

[0030] A Si-photodiode detector for receiving light transmitted through the soft matter sample and measuring its transmitted light intensity;

[0031] A nonlinear correction module, used to correct the data output by the Si-photodiode detector;

[0032] The light source correction module is used to optimize the quality of circularly polarized light and adjust the angular distribution of the light source through a reduction factor to eliminate measurement errors caused by the inconsistency of the light source ellipticity;

[0033] The data processing unit calculates the optical axis orientation angle φ, dichroism Δκ and birefringence effect Δn of the sample.

[0034] Preferably, the data processing unit further includes an algorithm for performing light source reduction correction, which automatically calculates and applies reduction factors to correct the influence of the light source based on the input angular distribution data of circularly polarized light, thereby ensuring the accuracy and consistency of transmittance measurement.

[0035] Preferably, the Si-photodiode detector has an automatic gain control function to adapt to measurement requirements at different transmittance levels and ensure signal stability and reliability under different conditions.

[0036] Preferably, it further comprises a spectral analysis module, which is used to analyze the wavelength distribution of light transmitted through the sample, allowing the optical response of the sample to light of different wavelengths to be measured simultaneously, thereby more comprehensively evaluating the optical properties of the material.

[0037] Preferably, the light source correction module includes a polarization state analyzer for real-time monitoring and adjusting the ellipticity of circularly polarized light to ensure the consistency and accuracy of the light source output.

[0038] The present invention provides a method for measuring the linear optical effect of soft matter by light transmittance, which has the following beneficial effects:

[0039] 1. The present invention can ensure high accuracy of transmittance measurement by using a Si-photodiode detector with nonlinear correction function, especially in a measurement environment with a high dynamic range. At the same time, the ellipticity and angular distribution of circularly polarized light are adjusted by a light source correction module, eliminating the influence of light source inconsistency, thereby improving the consistency and repeatability of experimental data.

[0040] 2. The present invention integrates multiple functions such as temperature effect, automatic rotation and spectral analysis. The device can not only study traditional optical properties, but also explore the response of materials to environmental factors such as temperature and spectral changes, providing an important tool for the development of new materials and in-depth research on existing materials. BRIEF DESCRIPTION OF THE DRAWINGS

[0041] Figure 1 It is a schematic diagram of the T-θ curve of the transmittance of circularly polarized light after passing through an anisotropic medium of the present invention;

[0042] Figure 2 It is a schematic diagram of the basic device of the present invention;

[0043] Figure 3 Schematic diagram of the relationship between the incident light power P (μW) and the Si-photodiode output voltage V (V) of the present invention;

[0044] Figure 4 It is a schematic diagram of an expansion device of the present invention;

[0045] Figure 5 It is a schematic diagram of the second expansion device of the present invention;

[0046] Figure 6 Schematic diagram of the expansion device of the present invention. DETAILED DESCRIPTION

[0047] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0048] Embodiment 1:

[0049] The embodiment of the present invention provides a method for measuring the linear optical effect of soft matter by light transmittance, comprising the following steps:

[0050] Step 1: Irradiate the optically anisotropic soft matter sample with circularly polarized light;

[0051] The polarized light source is equipped with an adjustable power controller to adjust the intensity of the incident light to accommodate samples with different absorbances, thereby optimizing the dynamic range and accuracy of transmittance measurements.

[0052] Step 2, measuring the transmittance change of circularly polarized light passing through the sample and recording it as a T-θ curve, wherein the T-θ curve reflects the optical axis orientation, dichroism and birefringence effect of the sample;

[0053] Please see attached Figure 1 Circularly polarized light can be regarded as a combination of two linearly polarized lights whose polarization directions are parallel and perpendicular to the optical axis of the sample. When a circularly polarized light with an intensity of I0 passes through an optically anisotropic medium, it will become elliptically polarized light due to the dichroism and birefringence effects. Its transmitted light intensity I t Angular distribution I t (θ), transmittance (also known as light transmittance, i.e., the intensity of transmitted light I t The ratio of the incident light intensity I0 to the incident light intensity I0) T also presents an angular distribution T(θ), when the incident light is left-handed circularly polarized light, and (b) when the incident light is right-handed circularly polarized light.

[0054] The optical axis and the dichroism and birefringence effects of the sample can be determined from the transmittance of circularly polarized light.

[0055] Step 3, directly determine the optical axis orientation angle φ of the sample by analyzing the T-θ curve, and further calculate the dichroism Δκ and birefringence effect Δn of the sample;

[0056] The optical axis orientation angle φ of the sample is determined based on the symmetry analysis of the T-θ curve measured by left-handed and right-handed circular light, which involves identifying two maxima and two minima on the curve to determine the optical axis orientation angle of the sample;

[0057] The dichroism Δκ is calculated from the T-θ curve to obtain the difference in absorbance 2α d l is obtained, the absorbance difference is 2α d l reflects the absorption characteristics of the sample to polarized light in different directions;

[0058] The birefringence effect Δn is determined by calculating the phase difference δ obtained from the T-θ curve, which represents the difference in refractive index of the sample for different directions of polarized light.

[0059] (1) Determination of the sample optical axis φ

[0060] The transmittance T-θ curve is dumbbell-shaped, with two maximum and minimum values ​​180° symmetrical. max The corresponding angle θ0 is:

[0061] For right-handed circularly polarized incident light,

[0062]

[0063] For left-handed circularly polarized incident light,

[0064]

[0065] 2α d The definitions of l and δ are shown in the explanations of equations (3) and (5). and are the angles between the long axis of the light intensity distribution of right-handed and left-handed circularly polarized incident light and the x-axis after passing through the sample, such as Figure 1 As shown. From formulas (1-1) and (1-2), we can get:

[0066]

[0067] Therefore, the optical axis orientation angle φ of the sample can be determined from the measured T(θ)-θ curve of the transmittance angular distribution after the right- and left-handed circularly polarized incident light passes through the sample.

[0068] (2) Derivation of dichroism Δκ

[0069] From the measured T(θ)-θ curve (such as Figure 1 As shown), we can get:

[0070]

[0071] 2α d l is the absorbance difference corresponding to the dichroic property. Equation (3) shows that the absorbance difference 2α can be derived from the optical axis orientation angle φ and the T(θ) values ​​of θ=φ and θ=φ+π / 2. d l.

[0072] The dichroism Δκ is the difference in extinction coefficients parallel and perpendicular to the sample optical axis and can be written as:

[0073]

[0074] Where λ is the wavelength of the incident light.

[0075] Therefore, the absorbance difference 2α can be derived from the sample optical axis orientation angle φ determined by the T(θ)-θ curve d l and the dichroism Δκ of the sample.

[0076] (3) Derivation of the birefringence effect Δn

[0077] From the measured T(θ)-θ curve (such as Figure 1 As shown), we can get:

[0078] If the incident light is right-handed circularly polarized, then

[0079]

[0080] δ is the phase delay corresponding to the birefringence effect.

[0081] If the incident light is left-handed circularly polarized, then

[0082]

[0083] Equations (5) and (6) show that the optical axis orientation angle φ, θ = φ + π / 4 and θ = φ + 3π / 4, and the T(θ) value and the absorbance difference 2α d l, the phase difference δ can be derived.

[0084] The birefringence effect Δn is the difference in refractive index parallel to and perpendicular to the sample optical axis and can be written as:

[0085]

[0086] Therefore, the optical axis orientation angle φ and the absorbance difference 2α determined by the T(θ)-θ curve d l, the phase difference δ and the birefringence effect Δn of the sample can be derived.

[0087] Step 4, using a Si-photodiode detector that has been processed for nonlinear correction to measure the T-θ curve;

[0088] Step 5: Apply the reduced incident light source correction technology to optimize the quality of circularly polarized light and ensure measurement accuracy.

[0089] Embodiment 2:

[0090] Please refer to the attached Figure 2-3 , an embodiment of the present invention provides a measuring device for measuring the linear optical effect of soft matter by light transmittance, comprising:

[0091] (1) Light source system:

[0092] The laser emitted by the He-Ne laser passes through a variable attenuator to obtain a beam of a certain power, and then the beam is divided into two beams through a beam splitter: one beam with an intensity of I0 as a reference light; the other beam with an intensity of I'0 as a probe light, I'0>I0. The probe light passes through a polarizer and a 1 / 4 wavelength wave plate to produce circularly polarized light. The angle between the polarization direction of the polarizer and the main axis of the 1 / 4 wavelength wave plate is 45° to produce right-handed circularly polarized light (or -45° to produce left-handed circularly polarized light). The circularly polarized light is adjusted to its light intensity of I0 through a variable aperture, and this aperture can also reduce the stray light irradiated on the sample.

[0093] (2) Samples to be tested:

[0094] The soft matter sample to be tested is encapsulated in a thin box, with the horizontal direction as the x-axis. The sample is thin enough to reduce the thermal effect caused by the accumulation of light energy (a temperature control table can be used in special cases) and to ensure a strong enough intensity of transmitted light. Usually, for liquid crystal samples, the thickness is on the order of 10 μm, and for magnetic colloid samples, the thickness is on the order of 10 μm. -1 mm level

[0095] (3) Detection system:

[0096] After circularly polarized light passes through a sample with optical anisotropy, the transmitted light will be converted into elliptically polarized light. The starting angle is set when the polarization orientation of the rotatable analyzer is along the x-axis, that is, θ = 0. The transmitted light intensity I with different polarization rotation angles θ can be obtained through the rotatable analyzer and Si-photodetector. t (θ), which is I t (θ)-θ curve. The analog electrical signal measured by the detector can be converted into a digital electrical signal by a data acquisition card. In addition, another light signal with an intensity of I0 obtained by the beam splitter can be converted into an analog electrical signal by the Si-photodetector, and then converted into a digital electrical signal by a data acquisition card. The digital signals from the detector and obtained by the data acquisition card are stored in the computer for processing, and finally the transmittance angle distribution curve is obtained, T(=I t (θ) / I0)-θ curve. The V obtained by the measurement light path and the reference light path passing through the detector and t (∝I t ) and V0(∝I0, which can eliminate the influence of laser emission fluctuations.

[0097] 3. Si-photodetector calibration

[0098] Transmittance is generally defined as: T = I t / I0,I0 and I t are the light intensity incident on the sample and transmitted through the sample respectively. The output voltage V(V) of the Si-photodiode is nonlinearly proportional to the power P(μW) of the detected light signal.

[0099] Embodiment three:

[0100] Please refer to the attached Figure 4 The embodiment of the present invention provides a measurement expansion device for measuring the linear optical effect of soft matter by transmittance, comprising:

[0101] The device is based on the device of the second embodiment and can measure linear optical effects under a magnetic field.

[0102] In this extended setup, the excitation power supply powers the Helmholtz coil, generating a magnetic field parallel to the sample surface (perpendicular to the light path). In addition, Figure 4 The Helmholtz coils in the microscope can be rotated 90° to generate a magnetic field perpendicular to the sample surface and along the optical path.

[0103] Embodiment 4:

[0104] Please refer to the attached Figure 5 The embodiment of the present invention provides a measurement expansion device for measuring the linear optical effect of soft matter by transmittance, comprising:

[0105] The device is based on the device of the second embodiment and can measure linear optical effects under an electric field.

[0106] In this extended device, the sample can be placed in a thin box made of conductive glass, and an electric field is applied to the box through a power amplifier to generate an electric field.

[0107] Embodiment five:

[0108] Please see attached Figure 6 The embodiment of the present invention provides a measurement expansion device for measuring the linear optical effect of soft matter by transmittance, comprising:

[0109] The device is based on the device of the second embodiment and can measure linear optical effects under magnetic and electric fields.

[0110] In this extended device, linear optical effects can be measured under the simultaneous action of magnetic and electric fields.

[0111] Although embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions and variations may be made to the embodiments without departing from the principles and spirit of the present invention, and that the scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A method for measuring the linear optical effect of soft matter by light transmittance, characterized in that: The following steps are involved: Step 1: Irradiate the optically anisotropic soft matter sample with circularly polarized light; Step 2, measuring the transmittance change of circularly polarized light passing through the sample and recording it as a T-θ curve, wherein the T-θ curve reflects the optical axis orientation, dichroism and birefringence effect of the sample; Step 3, directly determine the optical axis orientation angle φ of the sample by analyzing the T-θ curve, and further calculate the dichroism Δκ and birefringence effect Δn of the sample; Step 4, using a Si-photodiode detector that has been processed for nonlinear correction to measure the T-θ curve; Step 5: Use the reduced incident light source correction technology to optimize the quality of circularly polarized light and ensure measurement accuracy.

2. The method for measuring the linear optical effect of soft matter by light transmittance according to claim 1, characterized in that: The optical axis orientation angle φ of the sample is determined based on the symmetry analysis of the T-θ curves measured by left-handed and right-handed circular light, which involves identifying two maxima and two minima on the curve to determine the optical axis orientation angle of the sample.

3. The method for measuring the linear optical effect of soft matter by light transmittance according to claim 1, characterized in that: The dichroism Δκ is calculated from the T-θ curve to obtain the difference in absorbance 2α d l is obtained, the absorbance difference is 2α d l reflects the absorption characteristics of the sample to polarized light in different directions.

4. The method for measuring the linear optical effect of soft matter by light transmittance according to claim 1, characterized in that: The birefringence effect Δn is determined by calculating the phase difference δ obtained by the T-θ curve, and the phase difference δ represents the difference in refractive index of the sample for different directions of polarized light.

5. The method for measuring the linear optical effect of soft matter by light transmittance according to claim 1, characterized in that: The circularly polarized light source is equipped with an adjustable power controller to adjust the intensity of the incident light to adapt to samples with different absorption rates, thereby optimizing the dynamic range and accuracy of transmittance measurement.

6. A device for measuring the linear optical effect of soft matter by light transmittance, characterized in that: A method for measuring the linear optical effect of soft matter by light transmittance as claimed in any one of claims 1 to 5, comprising: A light source that produces circularly polarized light; Si-photodiode detector for receiving circularly polarized light transmitted through the soft matter sample and measuring its transmittance; A nonlinear correction module, used to correct the data output by the Si-photodiode detector; The light source correction module is used to optimize the quality of circularly polarized light and adjust the angular distribution of the light source through a reduction factor to eliminate measurement errors caused by the inconsistency of the light source ellipticity; The data processing unit is designed to analyze the data output by the Si-photodiode detector and calculate the optical axis orientation angle φ, dichroism Δκ and birefringence effect Δn of the sample.

7. The device for measuring the linear optical effect of soft matter by light transmittance according to claim 6, characterized in that: The data processing unit further includes an algorithm for performing light source reduction correction, which automatically calculates and applies reduction factors to correct the influence of the light source based on the input angular distribution data of circularly polarized light, thereby ensuring the accuracy and consistency of transmittance measurement.

8. The device for measuring the linear optical effect of soft matter by light transmittance according to claim 6, characterized in that: The Si-photodiode detector has an automatic gain control function to adapt to the measurement requirements at different transmittance levels and ensure the stability and reliability of the signal under different conditions.

9. The device for measuring the linear optical effect of soft matter by light transmittance according to claim 6, characterized in that: Further included is a spectrum analysis module for analyzing the wavelength distribution of light transmitted through the sample, allowing the optical response of the sample to light of different wavelengths to be measured simultaneously, thereby more comprehensively evaluating the optical properties of the material.

10. The device for measuring the linear optical effect of soft matter by transmittance according to claim 6, characterized in that: The light source correction module includes a polarization state analyzer, which is used to monitor and adjust the ellipticity of circularly polarized light in real time to ensure the consistency and accuracy of the light source output.

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