Terahertz wave transmission system with fixed-point focusing function

Abstract

The invention discloses a fixed-point focusing terahertz wave transmission system, belongs to the field of terahertz near-field imaging, and mainly solves the problem that a signal cannot be focused at a specified point during existing terahertz wave transmission. A fixed-point focusing terahertz wave transmission system is composed of a terahertz radiation source, a terahertz detector, a sample table and a light path assembly. Wherein the light path assembly comprises a collimating lens, two terahertz focusing lenses, a silver-plated reflector, a semi-transparent and semi-reflective mirror and a parabolic mirror which are respectively arranged according to design positions and angles. According to the fixed-point focusing terahertz wave transmission system provided by the invention, fixed-point focusing of terahertz waves is effectively realized through displacement of the parabolic mirror in the horizontal and vertical directions.

Description

Technical Field

[0001] The present invention relates to the field of terahertz near-field imaging, and particularly to a terahertz wave transmission system with fixed-point focusing. Background Art

[0002] Terahertz near-field imaging is a technique for high-resolution imaging using terahertz waves (with a frequency range of approximately 0.1 THz to 10 THz and a wavelength between 0.03 and 3 millimeters). It combines the unique characteristics of terahertz waves and near-field imaging technology, and has important application potential in the fields of biomedicine, materials science, non-destructive testing, etc.

[0003] The principle of a terahertz near-field imaging system is to utilize the localization characteristics of electromagnetic waves in the near-field region, that is, when approaching the surface of an object, the spatial resolution of the electromagnetic waves is no longer limited by the wavelength, getting rid of the limitation of the diffraction limit, and achieving a spatial resolution of nanometers or even higher through a probe or nano-scale optical elements.

[0004] To improve the utilization efficiency of terahertz waves, reduce energy loss, and obtain high imaging resolution, it is usually necessary to focus the divergent terahertz waves onto a specified point to be measured through an optical path. Currently, terahertz near-field imaging systems use a fixed optical path structure, and it requires experienced technicians to repeatedly adjust to make the terahertz waves focus on the sample to be measured. The disadvantage of this structure is that it is time-consuming and laborious, and it cannot be flexibly adjusted when the optical path or the position of the sample changes during use, resulting in poor imaging quality. Summary of the Invention

[0005] The purpose of the present invention is to provide a terahertz wave transmission system with fixed-point focusing to solve the problem that the existing terahertz near-field imaging system cannot perform fixed-point focusing.

[0006] To achieve the above purpose, the technical solution adopted by the present invention is:

[0007] A terahertz wave transmission system with fixed-point focusing includes:

[0008] A terahertz radiation source for radiating continuous terahertz waves;

[0009] A terahertz collimating lens for collimating the incident terahertz waves. The terahertz collimating lens is placed close to the terahertz radiation source, the terahertz radiation source is located at the focus of the terahertz collimating lens, and the principal optical axis of the terahertz radiation source is parallel to the transmission direction of the incident terahertz waves;

[0010] An incident terahertz focusing lens for focusing the incident terahertz waves and the reflected terahertz waves. The incident terahertz wave focusing lens is placed behind the terahertz collimating lens, and the central height is the same as that of the terahertz collimating lens, ensuring that the principal optical axis of the incident terahertz wave focusing lens coincides with the principal optical axis of the terahertz collimating lens;

[0011] A silver-plated mirror, which is used to reflect terahertz waves, has a central height consistent with that of the incident terahertz focusing lens, is located on the principal optical axis of the terahertz wave reflecting lens, and the principal optical axis is parallel to the principal optical axis of the reflected terahertz wave;

[0012] The terahertz wave reflecting lens is placed on the side close to the terahertz detector, so that the central height of the terahertz detector is consistent with that of the terahertz wave reflecting lens;

[0013] A semi-transparent and semi-reflective mirror, which is used to transmit half of the incident wave and reflect half of the echo, is located between the terahertz wave reflecting lens and the silver-plated mirror, and the principal optical axis of the semi-transparent and semi-reflective mirror forms a 45° angle with the principal optical axis of the incident terahertz wave;

[0014] A parabolic mirror, which is used to adjust the terahertz wave to focus on a specified point, is located on the principal optical axis of the incident terahertz wave, on the extension line of the incident terahertz focusing lens and the semi-transparent and semi-reflective mirror, and is placed far from the terahertz radiation source;

[0015] A terahertz detector, which is used to detect and receive terahertz echoes;

[0016] A sample stage, which is used to hold a sample and is located below the parabolic mirror.

[0017] The beneficial effect of the present invention is that, without changing the vertical height of the sample to be measured, by changing the position and angle of the parabolic mirror, the terahertz wave is focused on the specified point, effectively reducing energy loss and improving the imaging quality of the terahertz near-field system. Description of the Drawings

[0018] Figure 1 It is a schematic diagram of the structure composition of a terahertz wave transmission system with fixed-point focusing;

[0019] Figure 2 It is a schematic diagram of the incident light path and the reflected light path.

[0020] Reference Signs:

[0021] Terahertz radiation source 1, terahertz collimating lens 2, incident terahertz focusing lens 3, silver-plated mirror 4, terahertz wave reflecting lens 5, semi-transparent and semi-reflective mirror 6, terahertz detector 7; parabolic mirror 8, sample stage 9. Detailed Embodiments

[0022] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the following will briefly introduce the drawings required to be used in the embodiments. It should be understood that the following drawings only show some embodiments of the present invention, and therefore should not be regarded as a limitation of the scope. For those of ordinary skill in the art, without creative efforts, other related drawings can also be obtained based on these drawings.

[0023] SeeFigure 1 As shown in the figure, a terahertz wave transmission system with fixed-point focusing includes:

[0024] A terahertz radiation source 1 for radiating continuous terahertz waves;

[0025] A terahertz collimating lens 2 for collimating the incident terahertz waves. The terahertz collimating lens 2 is placed close to the terahertz radiation source 1. The terahertz radiation source 1 is located at the focal point of the terahertz collimating lens 2, and the principal optical axis of the terahertz radiation source 1 is parallel to the transmission direction of the incident terahertz waves;

[0026] An incident terahertz focusing lens 3 for focusing the incident terahertz waves and the reflected terahertz waves. The incident terahertz focusing lens 3 is placed behind the terahertz collimating lens 2, and the central height is the same as that of the terahertz collimating lens 2, ensuring that the principal optical axis of the incident terahertz focusing lens 3 coincides with the principal optical axis of the terahertz collimating lens 2;

[0027] A silver-plated mirror 4 for reflecting terahertz waves. The central height is the same as that of the incident terahertz focusing lens 3. It is located on the principal optical axis of the reflected terahertz wave lens 5, and the principal optical axis is parallel to the principal optical axis of the reflected terahertz wave, used to adjust the optical path length so that the light emitted from the incident terahertz focusing lens 3 is focused on the semi-transparent and semi-reflective mirror 6;

[0028] The reflected terahertz wave lens 5 is placed close to the terahertz detector 7 side, making the central height of the terahertz detector 7 the same as that of the reflected terahertz wave lens 5;

[0029] A semi-transparent and semi-reflective mirror 6 for transmitting half of the incident wave and reflecting half of the echo. It is located between the reflected terahertz wave lens 5 and the silver-plated mirror 4, and the principal optical axis of the semi-transparent and semi-reflective mirror 6 forms a 45° angle with the principal optical axis of the incident terahertz waves;

[0030] A terahertz detector 7 for focusing the incident terahertz waves and the reflected terahertz waves;

[0031] A parabolic mirror 8 for adjusting the terahertz waves to focus on a specified point. It is located on the principal optical axis of the incident terahertz waves, on the extension line of the incident terahertz focusing lens 3 and the semi-transparent and semi-reflective mirror 6, and is placed far from the terahertz radiation source 1;

[0032] A sample stage 9 for holding the sample and is located below the parabolic mirror 8.

[0033] In one embodiment, the terahertz collimating lens 2 is a collimating lens that matches the band of the terahertz radiation source 1, and is mainly used to collimate the terahertz beam radiated by the terahertz radiation source 1 to improve its transmission performance in the optical path. The incident terahertz focusing lens 3 is a focusing lens that matches the band of the terahertz radiation source 1 and is made of the polymer material polymethylpentene polymer, and is mainly used to focus the terahertz beam transmitted by the terahertz collimating lens 2. The silver-plated mirror 4 is a lens made by depositing a silver film on the surface of a glass substrate, and is used to totally reflect the terahertz signal focused by the incident terahertz focusing lens 3. The reflected terahertz wave lens 5 is a focusing lens that matches the band of the terahertz radiation source 1 and is a plano-convex aspherical lens made of the polymer material polymethylpentene polymer. The semi-transmissive and semi-reflective mirror 6 is an optical element that coats a semi-reflective film on optical glass to change the original transmission and reflection ratios of the incident light beam. The parabolic mirror 8 is a coated parabolic mirror customized according to the frequency of the terahertz radiation source 1, and is used to reflect the terahertz signal and focus it onto the sample stage. The terahertz detector 7 is a detector that matches the band of the terahertz radiation source 1, and uses the electrical signal generated after electrons in the material absorb terahertz radiation to detect the terahertz signal.

[0034] In one embodiment, the parabolic mirror 8 can be moved three-dimensionally in the horizontal and vertical directions to adjust the focusing of the terahertz wave at a specified point.

[0035] In one embodiment, the sample to be measured is fixed on the sample stage 9 and can be moved horizontally through the sample stage 9.

[0036] Refer to the incident terahertz wave transmission path and the reflected terahertz wave transmission path Figure 2 as shown. The incident terahertz wave emitted from the terahertz wave radiation source 1 passes through the terahertz collimating lens 2, then passes through the incident terahertz focusing lens 3, and then reaches the semi-transmissive and semi-reflective mirror 6.

[0037] The semi-transmissive and semi-reflective mirror 6 divides the incident terahertz wave into two paths of reflection and transmission. The transmitted terahertz wave is focused onto the sample stage 9 through the parabolic mirror 8 and is reflected to generate an echo. The echo reaches the parabolic mirror 8 and is reflected again to reach the semi-transmissive and semi-reflective mirror 6, and is also divided into two paths of reflection and transmission. Among them, the reflected echo finally reaches the terahertz detector 7 through the reflected terahertz wave lens 5. The parabolic mirror 8 is fixed on an axis that can move in the horizontal and vertical directions, and the fixed-point focusing is achieved by moving its position.

[0038] Those skilled in the art can easily understand that the above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent replacements, and improvements made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. A fixed-point focused terahertz wave transmission system, characterized in that: include: A terahertz radiation source (1) for radiating continuous terahertz waves; A terahertz collimating lens (2) is used to collimate an incident terahertz wave, the terahertz collimating lens (2) is placed close to the terahertz radiation source (1), the terahertz radiation source (1) is located at the focus of the terahertz collimating lens (2), and the main optical axis of the terahertz radiation source (1) is parallel to the transmission direction of the incident terahertz wave; An incident terahertz focusing lens (3) is used to focus an incident terahertz wave. The incident terahertz focusing lens (3) is placed after the terahertz collimating lens (2). The center height is consistent with that of the terahertz collimating lens (2), so as to ensure that the main optical axis of the incident terahertz focusing lens (3) coincides with the main optical axis of the terahertz collimating lens (2); A silver-coated reflector (4) for reflecting terahertz waves, having a center height consistent with that of the incident terahertz focusing lens (3), located on the principal optical axis of the reflecting terahertz wave lens (5), the principal optical axis being parallel to the principal optical axis of the reflecting terahertz wave, and used for adjusting the optical path length so that light emitted from the incident terahertz focusing lens (3) is focused on the semi-transparent and semi-reflective mirror (6); A terahertz wave reflecting lens (5) is placed close to one side of the terahertz detector (7) so that the center heights of the terahertz detector (7) and the terahertz wave reflecting lens (5) are consistent; A semi-transparent and semi-reflective mirror (6) is used to transmit half of the incident wave and reflect half of the echo wave, and is located between the terahertz wave reflecting lens (5) and the silver-coated reflective mirror (4), and the main optical axis of the semi-transparent and semi-reflective mirror (6) forms an angle of 45° with the main optical axis of the incident terahertz wave; A parabolic mirror (8) is used to adjust the terahertz wave to focus on a specified point, and is located on the principal optical axis of the incident terahertz wave, on the extension line of the incident terahertz focusing lens (3) and the semi-transparent and semi-reflective mirror (6), and is placed away from the terahertz radiation source (1); A terahertz detector (7), used for detecting and receiving terahertz echoes; The sample stage (9) is used to hold the sample and is located below the parabolic mirror (8).

2. The fixed-point focused terahertz wave transmission system according to claim 1, characterized in that: The parabolic mirror (8) can be moved three-dimensionally in the horizontal and vertical directions to adjust the terahertz wave to focus on a specified point.

3. The fixed-point focused terahertz wave transmission system according to claim 1, characterized in that: The sample to be tested is fixed on a sample stage (9) and can be moved horizontally through the sample stage.

4. The fixed-point focused terahertz wave transmission system according to claim 1, characterized in that: The terahertz radiation source (1) is a terahertz band continuous wave source, capable of generating terahertz band electromagnetic radiation.

5. The fixed-point focused terahertz wave transmission system according to claim 1, characterized in that: The terahertz collimating lens (2) is a collimating lens that matches the wavelength band of the terahertz radiation source (1).

6. The fixed-point focused terahertz wave transmission system according to claim 1, characterized in that: The incident terahertz focusing lens (3) is a focusing lens that matches the wavelength of the terahertz radiation source (1) and is made of a polymer material, polymethylpentene polymer.

7. The fixed-point focused terahertz wave transmission system according to claim 1, characterized in that: The silver-coated reflector (4) is a high-reflectivity lens made by depositing a silver film on the surface of a glass substrate.

8. The fixed-point focused terahertz wave transmission system according to claim 1, characterized in that: The terahertz wave reflecting lens (5) is a focusing lens that matches the wavelength of the terahertz radiation source (1), and is a plano-convex aspheric lens made of a polymer material, polymethylpentene polymer.

9. The fixed-point focused terahertz wave transmission system according to claim 1, characterized in that: The semi-transparent and semi-reflective mirror (6) is an optical element which is formed by coating a semi-reflective film on optical glass to change the original transmission and reflection ratio of the incident light beam.

10. The fixed-point focused terahertz wave transmission system according to claim 1, characterized in that: The parabolic mirror (8) is a coated parabolic mirror customized according to the frequency of the terahertz radiation source (1).

11. The fixed-point focused terahertz wave transmission system according to claim 1, characterized in that: The terahertz detector (7) is a detector that matches the wavelength of the terahertz radiation source (1) and detects the terahertz signal by utilizing the electrical signal generated by the electrons in the material absorbing the terahertz radiation.

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