A terahertz wave-based glass material detection device and method

Abstract

The application discloses a kind of glass material detection device and method based on terahertz wave, the detection device includes: terahertz signal generator, frequency doubler, first horn antenna of the terahertz wave after frequency doubler adjustment is emitted, first lens is converged to the terahertz wave emitted by first horn antenna, second lens is converged to the terahertz wave that penetrates detection sample, second horn antenna is received to the terahertz wave that passes through second lens, detector and terahertz power meter.The application can determine the thickness, material, thickness uniformity, material uniformity of the glass sample to be measured according to the detected terahertz power, which is high in detection efficiency, sensitive, low in size requirement for the sample to be measured, and low in detection cost.

Description

Technical Field

[0001] This invention relates to the technical field of terahertz wave-based material detection methods. Background Technology

[0002] Glass used in medical devices, laboratory equipment and other fields has high requirements for thickness, thickness uniformity, material purity and material uniformity, but existing testing methods are difficult to obtain quantitative test results for these parameters accurately and quickly.

[0003] In existing technologies, millimeter waves are used for glass sample testing. The thickness of the sample can be determined based on the penetration of the millimeter wave, and the thickness at different locations can be imaged based on the correlation between sample thickness and normalized energy to determine the sample's thickness uniformity. Although millimeter waves have a smaller beam width and higher spatial resolution than Gaussian beams, their longer wavelength results in insufficient sensitivity for thickness and uniformity detection. Furthermore, millimeter waves are prone to diffraction at sample edges, leading to measurement errors. To avoid such errors, the size of the sample being tested needs to be limited.

[0004] In addition, existing detection methods such as millimeter wave detection can only detect the thickness uniformity of a sample, but cannot detect the material uniformity, and their detection processes are costly and inefficient. Summary of the Invention

[0005] To address the shortcomings of existing technologies, the present invention aims to provide a glass material detection device and method based on terahertz waves. This device or method can detect the thickness, thickness uniformity, material properties, and material uniformity of glass materials. It has high sensitivity, low requirements on sample size, and can significantly improve the detection speed and reduce the detection cost of glass or similar substances.

[0006] The technical solution of the present invention is as follows:

[0007] A terahertz wave-based glass material detection device includes: a terahertz signal generator for generating terahertz waves; a frequency multiplier for adjusting the frequency of the terahertz waves generated by the terahertz signal generator; a first horn antenna for transmitting the terahertz waves adjusted by the frequency multiplier; a first lens for focusing the terahertz waves transmitted by the first horn antenna; a second lens for focusing the terahertz waves penetrating the test sample; a second horn antenna for receiving the terahertz waves passing through the second lens; a detector for detecting the received terahertz waves; and a terahertz power meter for measuring the power of the detected terahertz waves. The first lens and the second lens are arranged parallel to each other, the first horn antenna is located at the focal length of the first lens, and the second horn antenna is located at the focal length of the second lens.

[0008] The present invention further provides a method for testing glass materials using the above-mentioned testing device, comprising:

[0009] The glass sample to be tested is placed between the first lens and the second lens, and its placement position is such that the terahertz wave is incident perpendicularly on the sample;

[0010] Start the terahertz signal generator, set its transmission power, record the power value P2 measured by the terahertz power meter, and record the power value P1 measured after removing the glass sample to be tested.

[0011] The parameters to be measured for the glass sample are determined based on the obtained power values ​​P1 and P2.

[0012] The parameter to be measured is selected from one or more of thickness, thickness uniformity, material, and material uniformity.

[0013] According to some preferred embodiments of the present invention, the parameter to be measured is determined based on the terahertz wave transmittance Γ, where Γ = P2 - P1.

[0014] According to some preferred embodiments of the present invention, the parameter to be measured is thickness, which is determined by the following detection model:

[0015]

[0016] in,

[0017]

[0018]

[0019]

[0020] α+iβ

[0021]

[0022]

[0023] η0=120π

[0024] Where d represents the thickness of the sample being tested, τ represents the transmission coefficient, and τ 12 τ represents the transmission coefficient of terahertz waves from air to a glass medium. 21Γ represents the transmission coefficient of terahertz waves from the glass medium to the air, γ represents the propagation constant of terahertz waves, Γ represents the transmittance of terahertz waves, η1 represents the wave impedance in the air, η2 represents the wave impedance in the sample, α represents the attenuation constant, β represents the phase constant, η0 represents the wave impedance of electromagnetic waves in free space, ε′1 represents the real part of the relative permittivity of air, ε′2 represents the real part of the relative permittivity of the glass sample, and i represents the imaginary unit.

[0025] According to some preferred embodiments of the present invention, the parameter to be measured is thickness uniformity, and the determination process includes: changing the detection point of the glass sample to be measured, that is, the incident point of the incident terahertz wave on the glass sample to be measured, obtaining the detection thickness at different detection points according to the detection model, and determining the thickness uniformity according to the thickness at different detection points.

[0026] According to some preferred embodiments of the present invention, the parameter to be measured is the material, and the determination process includes: obtaining the relative permittivity-terahertz wave transmittance curves of various standard glass samples through the detection device, i.e., obtaining the standard relative permittivity-terahertz wave transmittance curve; determining the relative permittivity corresponding to the terahertz wave transmittance of the detected glass sample based on the standard relative permittivity-terahertz wave transmittance curve; and determining the material of the glass sample based on its relative permittivity.

[0027] According to some preferred embodiments of the present invention, the parameter to be measured is material uniformity, and the determination process includes: setting the transmission power of the terahertz signal generator to a power range that varies according to a certain scanning step size, setting the power value of the scanning step size, scanning the glass sample to be tested, plotting the transmission power-terahertz wave transmittance curve of the sample at each transmission power, and forming its power graph. If the power graph is a regular oscillation curve, it indicates that the sample material is uniform; otherwise, the sample material is not uniform.

[0028] The terahertz waves used in this invention for glass material detection have the characteristics of large bandwidth and high resolution, which can significantly improve detection sensitivity.

[0029] The detection method of the present invention is highly efficient and low in cost, and can be widely used. Attached Figure Description

[0030] Figure 1 This is a schematic diagram of the detection device in a specific embodiment.

[0031] Figure 2 The image shows the thickness-terahertz transmittance curve obtained in Example 1.

[0032] Figure 3 The graph shows the relative permittivity-terahertz transmittance obtained in Example 1.

[0033] Figure 4 The frequency-transmittance oscillation diagram obtained in Example 1 is shown.

[0034] Figure 5 This is a comparison chart of thickness-terahertz transmittance curves obtained by terahertz wave and millimeter wave detection in Example 1.

[0035] Figure 6 This is a comparison chart of the relative permittivity-terahertz transmittance curves obtained from terahertz wave and millimeter wave detection in Example 1. Detailed Implementation

[0036] The present invention will now be described in detail with reference to embodiments and accompanying drawings. However, it should be understood that the embodiments and drawings are for illustrative purposes only and do not constitute any limitation on the scope of protection of the present invention. All reasonable modifications and combinations included within the inventive spirit of the present invention fall within the scope of protection of the present invention.

[0037] See attached document Figure 1 In one specific embodiment, the terahertz wave-based glass material detection device of the present invention includes:

[0038] The system comprises: a terahertz signal generator 1 that generates terahertz waves; a frequency multiplier 2 that adjusts the frequency of the terahertz waves generated by the terahertz signal generator 1; a first horn antenna 3 that transmits the terahertz waves adjusted by the frequency multiplier 2; a first lens 4 that focuses the terahertz waves transmitted by the first horn antenna 3; a second lens 6 that focuses the terahertz waves penetrating the detection sample 5; a second horn antenna 7 that receives the terahertz waves passing through the second lens 2; a detector 8 that detects the received terahertz waves; and a terahertz power meter 9 that measures the power of the detected terahertz waves. The first lens 4 and the second lens 6 are arranged parallel to each other, the first horn antenna 3 is located at the focal length of the first lens 4, and the second horn antenna 7 is located at the focal length of the second lens 2.

[0039] Furthermore, in some specific embodiments, the method for detecting thickness uniformity using the above-described detection device includes the following steps:

[0040] (1) Set the transmission power of terahertz signal generator 1 to 220 GHz and the frequency multiplier to 18 times;

[0041] (2) Place the test sample 5 between the first lens 4 and the second lens 6, and make its placement position perpendicular to the line connecting the first horn antenna 3 and the second horn antenna 7. Start the terahertz signal generator 1 and record the power value P2 measured by the terahertz power meter 9.

[0042] (3) Keep the detection method of step (2), remove the test sample 5, and record the power value P1 measured by the terahertz power meter;

[0043] (4) Calculate the thickness of the sample based on the obtained power values ​​P1 and P2. The calculation model is as follows:

[0044]

[0045] in,

[0046]

[0047] Γ=P2-P1

[0048]

[0049]

[0050]

[0051]

[0052] η0=120π

[0053] γ=α+iβ

[0054] Where d represents the thickness of the sample being tested, τ represents the transmission coefficient, and τ 12 τ represents the transmission coefficient of terahertz waves from air to a glass medium. 21 Γ represents the transmission coefficient of terahertz waves from the glass medium to the air, γ represents the propagation constant of terahertz waves, Γ represents the transmittance of terahertz waves, η1 represents the wave impedance in the air, η2 represents the wave impedance in the sample, α represents the attenuation constant, β represents the phase constant, P1 represents the power value obtained when the sample is tested without glass, P2 represents the power obtained when the sample is tested with glass, η0 represents the wave impedance of electromagnetic waves in free space, ε′1 represents the real part of the relative permittivity of air, ε′2 represents the real part of the relative permittivity of the glass sample, and i represents the imaginary unit.

[0055] The relative permittivity can be obtained using a vector network analyzer.

[0056] The process of obtaining this computational model is as follows:

[0057] The reflection coefficient ρ of the glass sample under test can be obtained from the Fresnel formula for parallel polarized waves. h and transmission coefficient τ h :

[0058]

[0059]

[0060] Where θ1 represents the incident angle of the terahertz wave from the air into the glass sample, θ2 represents the refraction angle of the terahertz wave in the sample, η1 represents the wave impedance in the air, and η2 represents the wave impedance in the sample.

[0061] Under the condition of perpendicular incidence, the angle of incidence and the angle of refraction are 0, then the reflection coefficient and the transmission coefficient can be simplified to:

[0062]

[0063]

[0064] Furthermore, since multiple reflections and transmissions occur within the glass sample being tested, the transmission coefficient is calculated as follows:

[0065]

[0066]

[0067] Where d represents the sample thickness, α is the attenuation constant, β is the phase constant, λ is the wavelength of the terahertz wave, ε′ is the real part of the relative permittivity of the sample, and ε″ is the imaginary part of the relative permittivity of the sample.

[0068] Furthermore, based on the relationship between transmittance Γ and transmittance coefficient τ, it is as follows:

[0069] Γ=|τ| 2

[0070] The relationship between transmittance Γ and thickness can be calculated. The sample thickness is determined by the transmittance, and the thickness uniformity is determined based on the thickness at different locations of the sample.

[0071] Furthermore, according to the Huygens-Fresnel theorem, every point on the wavefront is a source of a spherical wave undergoing secondary radiation, and the radiation field at any point in space is the result of the superposition and interference of secondary wave sources at points on any closed surface surrounding the wavefront. If the transmittance oscillates at a specific power, it indicates that the sample material has good homogeneity. Therefore, the material homogeneity of the sample can be determined by observing whether there is oscillation on the power graph. The power graph can be obtained as follows: the transmission power of the terahertz signal generator 1 is set to 220-325 GHz, the scanning step size is set to 0.1 GHz, the sample is scanned and tested, the transmittance Γ obtained at each transmission power is recorded, and the power-transmittance curves at each transmission power are plotted to form the power graph.

[0072] The technical solution of the present invention will be further demonstrated below with reference to the embodiments.

[0073] Example 1

[0074] The thickness and thickness uniformity of the glass sample were tested using the detection device and method described in the above specific embodiments. The sample size was 18*18cm, and the sample material was ordinary white glass. During the test, the transmission power of the terahertz signal generator was set to 0dBm and the frequency of the terahertz signal was set to 220GHz. The power value measured by the terahertz power meter was recorded. The directional gain of the far-field beam pattern of the terahertz wave emitted by the first horn antenna was 34dBi, and the beam divergence angle was approximately 4°.

[0075] The relationship between the sample thickness and the transmittance of terahertz waves penetrating the sample (i.e., the transmittance shown in the figure, in dB) is as follows: Figure 2 As shown, the noise power of the terahertz antenna used is -38 dBm. It can be seen that, according to the attached... Figure 2 Once the transmittance of the sample is obtained, its thickness can be determined. Furthermore, once the thickness at different locations of the sample is obtained, its uniformity in thickness can be determined.

[0076] In this embodiment, the sample thickness, pre-measured by vernier calipers, was 1.20 cm (accurate to within 0.5 cm). The sample thickness, measured by a terahertz wave-based thickness detection device, was 1.22 cm, achieving millimeter-level accuracy. Another sample with a pre-measured thickness of 0.30 cm was tested; the thickness of this sample, measured by the terahertz wave-based thickness detection device, was 0.31 cm, also achieving millimeter-level accuracy. The detection results are shown in the table below:

[0077] Transmittance (dB) Measure thickness (cm) Actual thickness (cm) -3.71 0.31 0.30 -10.27 1.22cm 1.20

[0078] Furthermore, by plotting the relative permittivity of the sample on the x-axis and the transmittance of the terahertz wave penetrating the sample on the y-axis, the following result can be obtained: Figure 3 The relative permittivity-terahertz transmittance curve shown is from Figure 3 As can be seen, when the sample thickness and terahertz wave frequency remain constant, there is a certain correlation between terahertz wave transmittance and relative permittivity. Therefore, the material of different samples or different locations on the sample can be determined by the terahertz wave transmittance (different materials have different relative permittivity). Furthermore, the material properties at different locations can be used to determine whether the sample is materially uniform. In this embodiment, the thickness at multiple points was measured, and the difference between the maximum and minimum thickness was 0.02 cm, indicating that the glass sample has a relatively uniform thickness.

[0079] Furthermore, by setting the power range of the terahertz signal generator to 220GHz–325GHz for frequency sweeping, and measuring and recording the transmittance of the terahertz waves, the results are shown in the attached figure. Figure 4 The power (frequency)-transmittance oscillation plot shown is obtained by... Figure 4It can be seen that the uniformity of the material can be determined by observing whether the transmittance of electromagnetic waves of different frequencies oscillates, i.e., whether there is interference. In this embodiment, if the curve is a regular oscillation curve, it means that the terahertz wave is parallel light after passing through the sample, and the optical path difference of the parallel light is an integer multiple of the terahertz wavelength at some frequency points, resulting in interference. It can be inferred that the sample material is uniform. If the sample material is not uniform, the terahertz wave passing through the sample is not a parallel beam, cannot interfere, and will not show a regular oscillation curve.

[0080] Furthermore, using millimeter-wave test results for comparison, the millimeter-wave test method involved setting the millimeter-wave signal generator power to 30GHz, similar to the terahertz wave measurement method. The sample was placed between two lenses, and the millimeter-wave transmittance was measured. Curves were plotted comparing the transmittance of samples with different thicknesses. After the test, the sample thickness measured under both methods was plotted on the x-axis, and the sensitivity on the y-axis, to obtain a comparison of the thickness-sensitivity curves, as shown in the attached figure. Figure 5 As shown in the figure, sensitivity is obtained by differentiating the transmittance with respect to the thickness and taking the absolute value of the derivative. The relative permittivity of the sample under the two methods is plotted on the x-axis, and sensitivity on the y-axis, to obtain a comparison of the relative permittivity-sensitivity curves, as shown in the attached figure. Figure 6 As shown. From the appendix Figure 5 , 6 It can be seen that terahertz waves are significantly more sensitive than millimeter waves in terms of material thickness and material properties.

[0081] The above embodiments are merely preferred embodiments of the present invention, and the scope of protection of the present invention is not limited to the above embodiments. All technical solutions falling within the scope of the present invention's concept are within the scope of protection of the present invention. It should be noted that for those skilled in the art, improvements and modifications made without departing from the principles of the present invention should also be considered within the scope of protection of the present invention.

Claims

1. A method for detecting glass materials based on terahertz waves, characterized in that, The device performs glass material testing using a detection apparatus, which includes: a terahertz signal generator that generates terahertz waves; a frequency multiplier that adjusts the frequency of the terahertz waves generated by the terahertz signal generator; a first horn antenna that transmits the terahertz waves adjusted by the frequency multiplier; a first lens that converges the terahertz waves transmitted by the first horn antenna; a second lens that converges the terahertz waves that penetrate the test sample; a second horn antenna that receives the terahertz waves that have passed through the second lens; a detector that detects the received terahertz waves; and a terahertz power meter that measures the power of the detected terahertz waves. The first lens and the second lens are arranged parallel to each other, and the first horn antenna is located at the focal length of the first lens, while the second horn antenna is located at the focal length of the second lens. The detection method includes: The glass sample to be tested is placed between the first lens and the second lens, and its placement position is such that the terahertz wave is incident perpendicularly on the glass sample to be tested. Start the terahertz signal generator, set its transmission power, record the power value P2 measured by the terahertz power meter, and record the power value P1 measured after removing the glass sample to be tested. The parameters to be measured for the glass sample are determined based on the terahertz wave transmittance Γ, where Γ = P2 - P1. The parameter to be measured is selected from one or more of thickness, thickness uniformity, material, and material uniformity.

2. The method according to claim 1, characterized in that, The parameter to be measured is thickness, which is determined using the following detection model: ； in, ； ； ； ； ； ； ； Where d represents the thickness of the sample being tested. Indicates the transmission coefficient. This represents the transmission coefficient of terahertz waves from air to a glass medium. This represents the transmission coefficient of terahertz waves from a glass medium to air. This represents the propagation constant of terahertz waves. This indicates the transmittance of terahertz waves. This represents the wave impedance of electromagnetic waves in air. This represents the wave impedance of electromagnetic waves in a sample. Represents the attenuation constant. Represents the phase constant. This represents the wave impedance of an electromagnetic wave in free space. The real part of the relative permittivity of air is represented by . The real part of the relative permittivity of the glass sample is represented by , and i represents the imaginary unit.

3. The method according to claim 1, characterized in that, The parameter to be measured is thickness uniformity, and its determination process includes: changing the detection point of the glass sample to be measured, that is, the incident point of the incident terahertz wave on the glass sample to be measured, obtaining the detection thickness at different detection points according to the detection model, and determining its thickness uniformity based on the thickness at different detection points.

4. The method according to claim 1, characterized in that, The parameter to be tested is the material, and its determination process includes: obtaining the relative permittivity-terahertz wave transmittance curves of various standard glass samples through the detection device, that is, obtaining the standard relative permittivity-terahertz wave transmittance curve; determining the relative permittivity corresponding to the terahertz wave transmittance of the glass sample to be tested based on the standard relative permittivity-terahertz wave transmittance curve; and determining the material of the glass sample to be tested based on its relative permittivity.

5. The method according to claim 1, characterized in that, The parameter to be tested is the material uniformity. The determination process includes: setting the transmission power of the terahertz signal generator to a power range that varies according to a certain scanning step size, setting the power value of the scanning step size, scanning the glass sample to be tested, plotting the transmission power-terahertz wave transmittance curve of the sample at each transmission power, and forming its power graph. If the power graph is a regular oscillation curve, it indicates that the sample material is uniform; otherwise, the sample material is not uniform.

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