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Method and system for measuring thickness of non-metallic materials using terahertz waves

A technology of non-metallic materials and terahertz waves, applied in the field of thickness measurement, can solve problems such as inability to measure materials and measurement errors, and achieve the effects of rigorous and accurate material measurement, simple system structure, and guaranteed accuracy

Active Publication Date: 2020-03-24
CHINA SPECIAL EQUIP INSPECTION & RES INST
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

[0003] At present, the traditional thickness measurement method based on the terahertz principle is usually based on the known refractive index of the sample, which measures the material once to obtain the receiving time difference between the two reflection signals, and then combines the receiving time difference and Known refractive index to calculate the thickness of the material, however, this method cannot measure the thickness of the material when the refractive index of the material is unknown
[0004] In order to overcome the above defects, there is a method using reverse calculation, which obtains the receiving time difference between two reflection signals by measuring a standard sample with known thickness, and then reversely calculates the Refractive index; then, the thickness of the material is obtained by the receiving time difference between the two reflection signals obtained by one measurement of the same sample material and the above-mentioned reverse calculated refractive index, however, this method has Measurement errors caused by factors such as differences

Method used

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  • Method and system for measuring thickness of non-metallic materials using terahertz waves
  • Method and system for measuring thickness of non-metallic materials using terahertz waves
  • Method and system for measuring thickness of non-metallic materials using terahertz waves

Examples

Experimental program
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Effect test

Embodiment 1

[0052] In this embodiment, polyethylene pipes (about 3 cm in thickness) with unknown refractive index and thickness are measured, and the specific method is as follows:

[0053] 1. First measurement

[0054] Make the terahertz wave perpendicular to the emission distance of 30cm (θ i =0°) incident on the surface of the polyethylene pipe, the terahertz wave is reflected by the surface of the polyethylene pipe (i.e., the outer wall of the pipe) to form the first reflected signal, and at the same time, the terahertz wave passes through the surface of the polyethylene pipe and is reflected on the bottom surface of the polyethylene pipe (that is, the inner wall of the pipe) reflection forms the second reflection signal.

[0055] Receive the first reflected signal and the second reflected signal above, and obtain the receiving time difference ΔT between the first reflected signal and the second reflected signal 1 .

[0056] 2. The second measurement

[0057] Make the same teraher...

Embodiment 2

[0068] In this embodiment, both the refractive index and the thickness are unknown to the glass fiber board (the thickness is about 2.5mm) and the specific method is as follows:

[0069] 1. First measurement

[0070] Make the terahertz wave perpendicular to the launch distance of 20cm (θ i =0°) incident on the surface of the above-mentioned glass fiber plate, the terahertz wave is reflected by the surface of the glass fiber plate to form a first reflection signal, and at the same time, the terahertz wave passes through the surface of the glass fiber plate and is reflected on its bottom surface to form a second reflection signal.

[0071] Receive the first reflected signal and the second reflected signal above, and obtain the receiving time difference ΔT between the first reflected signal and the second reflected signal 1 .

[0072] 2. The second measurement

[0073] Make the same terahertz wave with a launch distance of 20cm and an incident angle of 30°(θ i =30°) incident ...

Embodiment 3

[0084] In this embodiment, a silicon wafer (about 0.5mm in thickness) whose refractive index and thickness are unknown is measured, and the specific method is as follows:

[0085] 1. First measurement

[0086] Make the terahertz wave perpendicular to the launch distance of 10cm (θ i =0°) incident on the surface of the above-mentioned silicon wafer, the terahertz wave is reflected by the surface of the silicon wafer to form a first reflection signal, and at the same time, the terahertz wave passes through the surface of the silicon wafer and is reflected on the bottom surface to form a second reflection signal.

[0087] Receive the first reflected signal and the second reflected signal above, and obtain the receiving time difference ΔT between the first reflected signal and the second reflected signal 1 .

[0088] 2. The second measurement

[0089] Let the same terahertz wave be emitted at a distance of 10cm and an incident angle of 55°(θ i =55°) incident on the same positi...

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Abstract

The present invention provides a method and a system for measurement of thickness of non-metallic materials by employing Terahertz waves. The method comprises the steps of: Terahertz waves are vertically incident into the surface of non-metallic materials, the Terahertz waves are reflected by the surface and the bottom surface of the non-metallic materials to respectively form first reflection signals and second reflection signals, the first and second reflection signals are received, and a receiving time difference [Delta]T1 of the two reflection signals is obtained; the Terahertz waves are incident into the surface of the non-metallic materials at an angle of [Theta]i, the Terahertz waves are reflected by the surface and the bottom surface of the non-metallic materials to respectively form third reflection signals and fourth reflection signals, the third reflection signals and the fourth reflection signals are received, and a receiving time difference [Delta]T2 of the two reflectionsignals is obtained, wherein [Theta]i is larger than 0 degree and smaller than 90 degrees; a refractive index n of the non-metallic materials is obtained according to the receiving time difference [Delta]T1 and the receiving time difference [Delta]T2; and the thickness d of the non-metallic materials is obtained according to the refractive index n of the non-metallic materials. The method can directly measure the refractive index and the thickness of the non-metallic materials, and is small in measurement error and high in accuracy.

Description

technical field [0001] The invention relates to a thickness measurement method, in particular to a method and system for measuring the thickness of non-metallic materials by using terahertz waves. Background technique [0002] Terahertz wave is an electromagnetic wave with a frequency of 0.1THz to 10THz, its wavelength is roughly 0.03mm to 3mm, and the wave band is between microwave and infrared light. In recent years, the rapid development of ultrafast laser technology has provided a stable and reliable excitation source for the generation of terahertz pulses, which has made the mechanism research, detection technology and application technology of terahertz radiation flourish. [0003] At present, the traditional thickness measurement method based on the terahertz principle is usually based on the known refractive index of the sample, which measures the material once to obtain the receiving time difference between the two reflection signals, and then combines the receiving...

Claims

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Application Information

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Patent Type & Authority Patents(China)
IPC IPC(8): G01B11/06G01N21/41
CPCG01B11/06G01N21/41
Inventor 俞跃郝元王强
Owner CHINA SPECIAL EQUIP INSPECTION & RES INST