CN117664920A - Terahertz wave-based glass material detection device and method - Google Patents
Terahertz wave-based glass material detection device and method Download PDFInfo
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- CN117664920A CN117664920A CN202311655664.7A CN202311655664A CN117664920A CN 117664920 A CN117664920 A CN 117664920A CN 202311655664 A CN202311655664 A CN 202311655664A CN 117664920 A CN117664920 A CN 117664920A
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- 238000001514 detection method Methods 0.000 title claims abstract description 55
- 239000011521 glass Substances 0.000 title claims abstract description 53
- 239000000463 material Substances 0.000 title claims abstract description 43
- 238000000034 method Methods 0.000 title claims abstract description 18
- 230000000149 penetrating effect Effects 0.000 claims abstract description 6
- 238000002834 transmittance Methods 0.000 claims description 38
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- 239000000523 sample Substances 0.000 description 70
- 238000004364 calculation method Methods 0.000 description 2
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Abstract
The invention discloses a device and a method for detecting glass materials based on terahertz waves, wherein the device comprises the following components: the terahertz power meter comprises a terahertz signal generator, a frequency multiplier, a first horn antenna for transmitting terahertz waves regulated by the frequency multiplier, a first lens for converging the terahertz waves transmitted by the first horn antenna, a second lens for converging the terahertz waves penetrating through a detection sample, a second horn antenna for receiving the terahertz waves passing through the second lens, a detector and a terahertz power meter. According to the terahertz power detection method, the thickness, the material, the thickness uniformity and the material uniformity of the glass sample to be detected can be determined according to the terahertz power obtained by detection, and the method has the advantages of high detection efficiency, high sensitivity, low size requirement on the sample to be detected and low detection cost.
Description
Technical Field
The invention relates to the technical field of material detection methods based on terahertz waves.
Background
The glass applied to the fields of medical equipment, experimental equipment and the like has higher requirements on thickness, thickness uniformity, material purity and material uniformity, but the existing detection means are difficult to accurately and rapidly obtain quantitative test results of the parameters.
In the prior art, millimeter waves are adopted to detect glass samples, thickness information of the samples can be determined according to penetration conditions of the millimeter waves on the samples, and the thicknesses of the samples at different positions are imaged according to correlation between the thicknesses of the samples and normalized energy to determine thickness uniformity of the samples. Although millimeter waves have smaller widths and higher spatial resolutions than Gaussian beams, the millimeter waves have larger wavelengths, have insufficient detection sensitivity to thickness and uniformity, and meanwhile, millimeter waves are easy to diffract at the edges of samples, so that errors occur in measurement results, and in order to avoid the errors, the size of the sample to be measured needs to be limited.
In addition, the existing detection means such as millimeter wave detection can only detect the thickness uniformity of a sample, the material uniformity of the sample cannot be detected, and the detection process is high in cost and low in efficiency.
Disclosure of Invention
Aiming at the defects of the prior art, the invention aims to provide a terahertz wave-based glass material detection device and a terahertz wave-based glass material detection method, which can detect thickness, thickness uniformity, material quality, material uniformity and the like of a glass material, have high sensitivity and low size requirements on a sample, and can remarkably improve the detection speed of glass or similar substances and reduce the detection cost of the glass or similar substances.
The technical scheme of the invention is as follows:
a terahertz wave-based glass material detection apparatus, comprising: the terahertz wave detector comprises 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 after the frequency multiplier is adjusted, a first lens for converging the terahertz waves transmitted by the first horn antenna, a second lens for converging the terahertz waves penetrating through a detection 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, wherein the first lens is arranged in parallel with the second lens, 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.
The invention further provides a method for detecting glass materials by using the detection device, which comprises the following steps:
placing a glass sample to be tested between the first lens and the second lens, and enabling the placing position to enable terahertz waves to vertically enter the sample;
starting a terahertz signal generator, setting the transmitting power of the terahertz signal generator, recording a power value P2 measured by a terahertz power meter, and recording a power value P1 measured after a glass sample to be detected is removed;
determining parameters to be measured of a glass sample to be measured according to the obtained power values P1 and P2;
the parameters to be measured are selected from one or more of thickness, thickness uniformity, material quality and material uniformity.
According to some preferred embodiments of the invention, the parameter to be measured is determined according to the terahertz wave transmittance Γ, Γ=p2-P1.
According to some preferred embodiments of the invention, the parameter to be measured is thickness, which is determined by the following detection model:
wherein,
α+iβ
η 0 ＝120π
wherein d represents the thickness of the sample to be measured, τ represents the transmission coefficient, τ 12 Representing the transmission coefficient of terahertz waves from air to a glass medium, τ 21 Representing the transmission coefficient of terahertz waves from a glass medium to air, γ representing the propagation constant of terahertz waves, Γ representing the transmittance of terahertz waves, η 1 Representing wave impedance, eta in air 2 Represents the wave impedance in the sample, alpha represents the decay constant, beta represents the phase constant, eta 0 Representing the wave impedance of electromagnetic waves in free space, ε' 1 Representing the real part of the relative permittivity of air, ε' 2 The real part of the relative permittivity of the glass sample is represented, i representing the imaginary unit.
According to some preferred embodiments of the present invention, the parameter to be measured is thickness uniformity, and the determining process includes: changing detection points of the glass sample to be detected, namely, incidence points of incident terahertz waves on the glass sample to be detected, obtaining detection thicknesses at different detection points according to the detection model, and determining thickness uniformity according to the thicknesses at different detection points.
According to some preferred embodiments of the present invention, the parameter to be measured is a material, and the determining process includes: obtaining relative dielectric constant-terahertz wave transmittance curves of various standard glass samples through the detection device, obtaining the standard relative dielectric constant-terahertz wave transmittance curves, determining the relative dielectric constant corresponding to the terahertz wave transmittance of the detected glass sample according to the standard relative dielectric constant-terahertz wave transmittance curves, and determining the material of the detected glass sample according to the relative dielectric constant.
According to some preferred embodiments of the present invention, the parameter to be measured is material uniformity, and the determining process includes: setting the transmitting power of the terahertz signal generator to a power range which changes according to a certain scanning step length, setting a power value of the scanning step length, carrying out scanning test on a glass sample to be tested, drawing a transmitting power-terahertz wave transmittance curve of the sample under each transmitting power, and forming a power diagram of the sample, wherein if the power diagram is a regular oscillation curve, the sample is uniform in material quality, otherwise, the sample is nonuniform in material quality.
The terahertz wave for detecting the glass material has the characteristics of large bandwidth and high resolution, and can remarkably improve the detection sensitivity.
The detection method has high efficiency and low cost, and can be widely applied.
Drawings
Fig. 1 is a schematic structural diagram of a detection device in an embodiment.
Fig. 2 is a graph of thickness-terahertz transmittance obtained in example 1.
FIG. 3 is a graph showing the relative dielectric constant-terahertz transmittance obtained in example 1.
Fig. 4 is a frequency-transmittance oscillation chart obtained in example 1.
Fig. 5 is a graph showing the thickness-terahertz transmittance curve obtained by terahertz wave and millimeter wave detection in example 1.
Fig. 6 is a graph showing the contrast of the relative dielectric constant-terahertz transmittance curve obtained by terahertz wave and millimeter wave detection in example 1.
Detailed Description
The present invention will be described in detail with reference to the following examples and drawings, but it should be understood that the examples and drawings are only for illustrative purposes and are not intended to limit the scope of the present invention in any way. All reasonable variations and combinations that are included within the scope of the inventive concept fall within the scope of the present invention.
Referring to fig. 1, in one embodiment, the terahertz wave-based glass material detection apparatus of the present invention includes:
the terahertz wave power measuring device comprises a terahertz signal generator 1 for generating terahertz waves, a frequency multiplier 2 for adjusting the frequency of the terahertz waves generated by the terahertz signal generator 1, a first horn antenna 3 for transmitting the terahertz waves after the frequency multiplier 2 is adjusted, a first lens 4 for converging the terahertz waves transmitted by the first horn antenna 3, a second lens 6 for converging the terahertz waves penetrating through a detection sample 5, a second horn antenna 7 for receiving the terahertz waves passing through the second lens 2, a detector 8 for detecting the received terahertz waves, and a terahertz power meter 9 for measuring the power of the detected terahertz waves; the first lens 4 and the second lens 6 are disposed in parallel, 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.
Further, in some embodiments, the method for detecting thickness uniformity according to the above detection device includes the following steps:
(1) Setting the transmitting power of the terahertz signal generator 1 to be 220GHz and the frequency multiplier to be 18 times;
(2) Placing a detection sample 5 between the first lens 4 and the second lens 6, enabling the placement position of the detection sample to be perpendicular to the connecting line of the first horn antenna 3 and the second horn antenna 7, starting the terahertz signal generator 1, and recording the power value P2 measured by the terahertz power meter 9;
(3) Maintaining the detection mode of the step (2), removing the detection sample 5, and recording the power value P1 measured by the terahertz power meter;
(4) And calculating the thickness of the detection sample according to the obtained power values P1 and P2, wherein a calculation model is as follows:
wherein,
Γ＝P2-P1
η 0 ＝120π
γ＝α+iβ
wherein d represents the thickness of the sample to be measured, τ represents the transmission coefficient, τ 12 Representing the transmission coefficient of terahertz waves from air to a glass medium, τ 21 Representing the transmission coefficient of terahertz waves from a glass medium to air, γ representing the propagation constant of terahertz waves, Γ representing the transmittance of terahertz waves, η 1 Representing wave impedance, eta in air 2 Represents the wave impedance in the sample, alpha represents the decay constant, beta represents the phase constant, P1 represents the power value obtained without glass detection sample, P2 represents the power obtained with glass detection sample, eta 0 Representing the wave impedance of electromagnetic waves in free space, ε' 1 Representing the real part of the relative permittivity of air, ε' 2 The real part of the relative permittivity of the glass sample is represented, i representing the imaginary unit.
The relative dielectric constant can be obtained by a vector network analyzer.
The process of obtaining the calculation model is as follows:
obtaining the reflection coefficient rho of the glass sample to be tested by using a Fresnel formula of parallel polarized waves h And transmission coefficient tau h ：
Wherein θ 1 Representing the incident angle of terahertz wave from air into glass sample, θ 2 Representing the refraction angle eta of terahertz waves in a sample 1 Representing wave impedance, eta in air 2 Representing the wave impedance in the sample.
Under normal incidence, the incidence and refraction angles are 0, and the reflection and transmission coefficients can be reduced to:
further, since multiple reflections and transmissions occur within the glass sample under test, the transmission coefficient is calculated as follows:
where d represents the thickness of the sample, 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, ε "is the imaginary part of the relative permittivity of the sample.
Further, according to the relation between the transmittance Γ and the transmittance τ, the following is adopted:
Γ＝|τ| 2
the calculated relation between the transmissivity gamma and the thickness can be obtained, the thickness of the sample is determined according to the transmissivity, and the thickness uniformity is determined according to the thicknesses of different positions of the sample.
In addition, according to the huyghen-fresnel theorem, each point on the wavefront is a source of spherical waves that perform secondary radiation, and the radiation field at any point in space is the result of the superposition and interference of the secondary sources at each point on any closed curved surface surrounding the wave surface. If the transmissivity oscillates at a specific power, it is indicated that the uniformity of the material of the sample is good, and therefore, by observing whether the oscillation exists on a power map, the uniformity of the material of the sample can be determined, and the power map can be obtained by the following ways: setting the transmitting power of the terahertz signal generator 1 to 220-325GHz, setting the scanning step length to 0.1GHz, carrying out scanning test on a sample, recording the transmittance gamma obtained under each transmitting power, and drawing a power-transmittance curve under each transmitting power to form the power graph.
The technical scheme of the invention is further shown below by combining examples.
Example 1
According to the detection device and the detection method in the specific embodiment, the thickness and the thickness uniformity of the glass sample are tested, wherein the size of the used sample is 18 x 18cm, the sample is made of common white glass, the transmission power of the terahertz signal generator is set to be 0dBm and the frequency of the terahertz signal is set to be 220GHz in the test, the power value measured by the terahertz power meter is recorded, the directional gain of the terahertz wave far-field beam pattern transmitted by the first horn antenna is 34dBi, and the beam divergence angle is about 4 degrees.
The relation between the thickness of the sample obtained by the test and the transmittance (namely, the illustrated transmittance, in dB) of the terahertz wave penetrating through the sample is shown in fig. 2, and the noise power of the terahertz antenna is-38 dBm. It can be seen that according to fig. 2, the thickness of the sample can be determined after the transmittance of the sample is obtained, and further, the uniformity of the thickness of the sample can be determined after the thickness of the sample at different positions is obtained.
In this embodiment, the thickness of the sample measured in advance by the vernier caliper is 1.20cm (accurate to within 0.5 cm), and the thickness of the sample measured by the terahertz wave-based thickness detecting device is 1.22cm, with an accuracy of the order of millimeters. Another sample with the thickness of 0.30cm measured in advance is taken for testing, and the thickness of the sample is measured to be 0.31cm by a thickness detection device based on terahertz waves, so that the accuracy can reach the millimeter level. The detection results of the two are shown in the following table:
| transmittance (dB) | Measuring thickness (cm) | Actual thickness (cm) |
| -3.71 | 0.31 | 0.30 |
| -10.27 | 1.22cm | 1.20 |
Further, the relative dielectric constant of the sample is taken as an abscissa, the transmittance of the terahertz wave penetrating through the sample is taken as an ordinate, a relative dielectric constant-terahertz transmittance curve shown in fig. 3 can be obtained, and as can be seen from fig. 3, under the condition that the thickness of the sample and the frequency of the terahertz wave are unchanged, the transmittance of the terahertz wave has a certain corresponding relation with the relative dielectric constant, so that materials of different samples or different positions of the sample (different relative dielectric constants of different materials) can be determined through the transmittance of the terahertz wave, and further, whether the materials of the sample are uniform or not can be determined according to the material conditions of the different positions of the sample. In this example, the thickness of the plurality of spots was measured with a difference of 0.02cm between the maximum and minimum, indicating that the glass sample was of relatively uniform thickness.
Further, the power range of the terahertz signal generator is set to 220 GHz-325 GHz to sweep, the transmittance of the terahertz wave is measured and recorded, a power (frequency) -transmittance oscillation diagram shown in fig. 4 can be obtained, and as can be seen from fig. 4, the uniformity of the material can be judged by observing whether the transmittance of electromagnetic waves with different frequencies oscillates, namely whether interference exists. In this embodiment, if the curve is a regular oscillation curve, it is indicated 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 the individual frequency point, so that it can be inferred that the sample material is uniform, and if the sample material is not uniform, the terahertz wave passing through the sample is not a parallel beam, no interference can occur, and no regular oscillation curve will occur.
Further, the millimeter wave test result is used as a comparison, the millimeter wave test mode is that the power of a millimeter wave signal generator is set to be 30GHz, the same as the terahertz wave test mode, a sample is placed between two lenses, the transmittance of millimeter waves is measured, curves of the samples with different thicknesses and the transmittance of the millimeter waves are drawn, the thicknesses of the samples measured in two modes are respectively used as abscissa and the sensitivity is used as ordinate after the test, the comparison condition of the thickness-sensitivity curve is obtained, and the comparison condition is shown in a figure 5, wherein the sensitivity is obtained by deriving the transmittance from the thickness, and obtaining the absolute value of the derivative; the relative permittivity of the sample is on the abscissa and the sensitivity is on the ordinate in two ways, and the comparison of the relative permittivity-sensitivity curve is obtained, as shown in fig. 6. As can be seen from the figures 5 and 6, the sensitivity of the terahertz wave in the material thickness and the material measurement is obviously higher than that of the millimeter wave.
The above examples are only preferred embodiments of the present invention, and the scope of the present invention is not limited to the above examples. All technical schemes belonging to the concept of the invention belong to the protection scope of the invention. It should be noted that modifications and adaptations to the present invention may occur to one skilled in the art without departing from the principles of the present invention and are intended to be within the scope of the present invention.
Claims (7)
1. A terahertz wave-based glass material detection apparatus, comprising: the terahertz wave detector comprises a terahertz signal generator for generating terahertz waves, a frequency multiplier for carrying out frequency adjustment on the terahertz waves generated by the terahertz signal generator, a first horn antenna for transmitting the terahertz waves after the frequency multiplier is adjusted, a first lens for converging the terahertz waves transmitted by the first horn antenna, a second lens for converging the terahertz waves penetrating through a detection 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 carrying out power measurement on the detected terahertz waves, wherein the first lens and the second lens are arranged in parallel, 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.
2. A method for detecting glass material using the detecting device according to claim 1, comprising:
placing a glass sample to be tested between the first lens and the second lens, and enabling terahertz waves to vertically enter the glass sample to be tested at the placing position;
starting a terahertz signal generator, setting the transmitting power of the terahertz signal generator, recording a power value P2 measured by a terahertz power meter, and recording a power value P1 measured after a glass sample to be detected is removed;
determining parameters to be measured of a glass sample to be measured according to the obtained power values P1 and P2;
the parameters to be measured are selected from one or more of thickness, thickness uniformity, material quality and material uniformity.
3. The method according to claim 2, wherein the parameter to be measured is determined from the terahertz wave transmittance Γ, Γ = P2-P1.
4. A method according to claim 3, wherein the parameter to be measured is thickness, which is determined by the following detection model:
wherein,
γ＝α+β
η 0 ＝120π
wherein d represents the thickness of the sample to be measured, τ represents the transmission coefficient, τ 12 Representing the transmission coefficient of terahertz waves from air to a glass medium, τ 21 Representing the transmission coefficient of terahertz waves from a glass medium to air, γ representing the propagation constant of terahertz waves, Γ representing the transmittance of terahertz waves, η 1 Representing the wave impedance, eta, of an electromagnetic wave in air 2 Represents the wave impedance of electromagnetic waves in a sample, alpha represents the attenuation constant, beta represents the phase constant, eta 0 Representing the wave impedance of electromagnetic waves in free space, ε' 1 Representing the real part of the relative permittivity of air, ε' 2 The real part of the relative permittivity of the glass sample is represented, i representing the imaginary unit.
5. A method according to claim 3, wherein the parameter to be measured is thickness uniformity, and the determining process comprises: changing detection points of the glass sample to be detected, namely, incidence points of incident terahertz waves on the glass sample to be detected, obtaining detection thicknesses at different detection points according to the detection model, and determining thickness uniformity according to the thicknesses at different detection points.
6. A method according to claim 3, wherein the parameter to be measured is a material, and the determining comprises: obtaining relative dielectric constant-terahertz wave transmittance curves of various standard glass samples through the detection device, obtaining the standard relative dielectric constant-terahertz wave transmittance curves, determining the relative dielectric constant corresponding to the terahertz wave transmittance of the detected glass sample according to the standard relative dielectric constant-terahertz wave transmittance curves, and determining the material of the detected glass sample according to the relative dielectric constant.
7. A method according to claim 3, wherein the parameter to be measured is uniformity of material, and the determining comprises: setting the transmitting power of the terahertz signal generator to a power range which changes according to a certain scanning step length, setting a power value of the scanning step length, carrying out scanning test on a glass sample to be tested, drawing a transmitting power-terahertz wave transmittance curve of the sample under each transmitting power, and forming a power diagram of the sample, wherein if the power diagram is a regular oscillation curve, the sample is uniform in material quality, otherwise, the sample is nonuniform in material quality.
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