Terahertz transmitting and receiving channel system and method based on optical ellipsometry principle

Abstract

The invention discloses a terahertz receiving and transmitting channel system and method based on an optical ellipsometry principle, and the system comprises a waveform generator which is configured to generate a modulation waveform changing with time; the terahertz emitter is configured to generate a terahertz radio-frequency signal, modulate the terahertz radio-frequency signal based on a modulation waveform, and then emit the terahertz radio-frequency signal to an object to be measured at a preset incident angle; the polarized light path is configured to perform polarization on the terahertz radio-frequency signal emitted by the terahertz emitter and perform polarization on the terahertz radio-frequency signal reflected by the object to be measured; and the terahertz detector is configured to receive the terahertz radio frequency signal which is reflected by the object to be measured and is polarized by the polarized light path so as to measure the thickness of the object to be measured. According to the invention, terahertz nondestructive testing imaging can be realized, faster and better imaging quality can be obtained, high-precision thickness measurement can be realized, and the method is especially suitable for in-situ nondestructive testing and thickness measurement systems for special coatings and structural members.

Description

Technical Field

[0001] The present invention relates to the field of terahertz radar detection technology, and in particular to a terahertz transceiver channel system and method based on the optical ellipsometry measurement principle. Background Art

[0002] Terahertz waves refer to electromagnetic waves with a frequency range of 100GHz to 10THz. They are between millimeter waves and infrared, called submillimeter waves or far-infrared light, and are in the transition zone from electronics to photonics. Compared with microwaves and millimeter waves, terahertz waves have shorter wavelengths, making it easier to achieve extremely large signal bandwidths and extremely narrow antenna beams, thereby obtaining fine target imaging.

[0003] Terahertz radar detection systems have good spatial resolution and angular resolution, and have good anti-interference capabilities. They are the key research topics of terahertz technology at home and abroad. Compared with infrared radar and laser radar, terahertz radar has good ability to penetrate smoke and dust, and can work all day long. In addition, terahertz radar can also remotely detect toxic biological particles or chemical gases propagating in the air. Terahertz radar is also a powerful weapon against stealth. Whether it is based on shape stealth, paint stealth, or even plasma stealth, terahertz radar can reveal its true form. This is exactly what most conventional detection methods cannot do at present. Terahertz technology can also be used for detection and imaging of dangerous goods and hidden objects. Because terahertz radiation is non-ionizing, it can penetrate materials that are opaque to other frequency ranges, such as packaging materials, clothes and even walls. These properties enable terahertz remote sensing to be used in non-destructive testing and safety inspections.

[0004] The current terahertz nondestructive testing technology mainly includes terahertz time-domain spectroscopy measurement technology (THz-TDS) and terahertz frequency-modulated continuous wave imaging technology (THz-FMCW). THz-TDS uses femtosecond laser excitation radiation sources and receivers to realize the detection of terahertz time-domain spectra. Currently, several companies at home and abroad have commercial products, which are mainly used to measure the terahertz spectrum of materials. In principle, this equipment can also be used for coating thickness measurement, but there are two major defects. First, because the terahertz radiation energy is too weak, the penetration distance is very short. Second, it is necessary to measure the thickness by point-by-point spectrum measurement, which makes the speed very slow. THz-FMCW uses frequency-modulated continuous terahertz waves in a scanning manner, based on the transmission characteristics of terahertz waves and the principle of radar ranging and imaging, and can effectively realize the detection and imaging of penetrating targets. Its advantage is that the imaging speed is very fast, and its disadvantage is that the thickness measurement accuracy is low.

[0005] Then, if in-situ non-destructive testing is performed on certain special coatings and structural parts, such as special coatings on aircraft surfaces or special structural parts such as wings, neither THz-TDS (the traditional distance is too short and the measurement speed is too slow) nor THz-FMCW (the thickness measurement accuracy is insufficient, at the millimeter level) can meet actual needs. Summary of the invention

[0006] In order to solve the above problems, the present invention proposes a terahertz transceiver channel system and method based on the optical ellipsometry measurement principle, which is suitable for constructing a terahertz thickness measurement system for in-situ non-destructive testing of special coatings and structural parts, thereby realizing accurate measurement of material thickness.

[0007] The technical solution adopted by the present invention is as follows:

[0008] A terahertz transceiver channel system based on the optical ellipsometry measurement principle, comprising:

[0009] a waveform generator configured to generate a time-varying modulated waveform;

[0010] A terahertz transmitter is configured to generate a terahertz radio frequency signal and modulate it based on a modulation waveform, and then transmit it to the object to be measured at a preset incident angle;

[0011] a polarization optical path configured to polarize a terahertz radio frequency signal emitted by the terahertz transmitter and to polarize a terahertz radio frequency signal reflected by the object to be measured;

[0012] The terahertz detector is configured to receive the terahertz radio frequency signal reflected by the object to be measured and polarized through the polarization light path, thereby realizing the thickness measurement of the object to be measured.

[0013] Furthermore, the waveform generator can change the output modulation waveform so that the waveforms of the received echo signal and the transmitted signal are inconsistent, that is, the frequency difference between the received echo signal and the transmitted signal changes with time, and multiple frequency differences, that is, difference frequency signals, correspond to a fixed distance, thereby realizing optical ellipsometric thickness measurement.

[0014] Furthermore, the polarization light path includes an incident light path and a reflected light path, the incident light path is configured to polarize and compensate the terahertz radio frequency signal emitted by the terahertz transmitter, thereby changing the polarization direction of the terahertz radio frequency signal; the reflected light path is configured to compensate and polarize the terahertz radio frequency signal reflected by the object to be measured.

[0015] Furthermore, the incident light path includes a polarizer and a first compensator, and the terahertz radio frequency signal emitted by the terahertz transmitter is incident on the object to be measured after passing through the polarizer and the first compensator in sequence.

[0016] Furthermore, the reflection optical path includes a polarizer and a second compensator, and the terahertz radio frequency signal reflected by the object to be measured is transmitted to the terahertz detector after passing through the second compensator and the polarizer in sequence.

[0017] A terahertz transceiver method based on the optical ellipsometric measurement principle, comprising:

[0018] A time-varying modulation waveform is generated by a waveform generator;

[0019] A terahertz radio frequency signal is generated by a terahertz transmitter and modulated based on a modulation waveform, and then transmitted to the object to be measured at a preset incident angle;

[0020] Polarize the terahertz radio frequency signal emitted by the terahertz transmitter through a polarization optical path, and polarize the terahertz radio frequency signal reflected by the object to be measured;

[0021] The terahertz radio frequency signal reflected by the object to be measured and polarized through the polarization light path is received by the terahertz detector, thereby realizing the thickness measurement of the object to be measured.

[0022] Furthermore, by changing the modulation waveform output by the waveform generator, the waveforms of the received echo signal and the transmitted signal are made inconsistent, that is, the frequency difference between the received echo signal and the transmitted signal changes with time, and multiple frequency differences, that is, difference frequency signals, correspond to a fixed distance, thereby realizing optical ellipsometric thickness measurement.

[0023] Furthermore, the polarization light path includes an incident light path and a reflected light path, the incident light path is configured to polarize and compensate the terahertz radio frequency signal emitted by the terahertz transmitter, thereby changing the polarization direction of the terahertz radio frequency signal; the reflected light path is configured to compensate and polarize the terahertz radio frequency signal reflected by the object to be measured.

[0024] Furthermore, the incident light path includes a polarizer and a first compensator, and the terahertz radio frequency signal emitted by the terahertz transmitter is incident on the object to be measured after passing through the polarizer and the first compensator in sequence.

[0025] Furthermore, the reflection optical path includes a polarizer and a second compensator, and the terahertz radio frequency signal reflected by the object to be measured is transmitted to the terahertz detector after passing through the second compensator and the polarizer in sequence.

[0026] The beneficial effects of the present invention are:

[0027] 1. Excellent performance, short measurement time and high precision. The present invention adopts the principle of optical ellipsometry thickness measurement, and can construct a terahertz thickness measurement system for in-situ non-destructive testing of special coatings and structural parts, so as to accurately measure the thickness of the object to be measured, which can reach the micron level; while the longitudinal measurement accuracy of the current common terahertz frequency modulated continuous wave ranging radar is generally at the millimeter level, so the present invention can achieve higher precision thickness measurement of the object to be measured.

[0028] 2. Simple structure, can meet multiple purposes. The present invention has two functional modes: terahertz frequency modulated continuous wave transceiver channel and terahertz high-precision ellipsometric thickness transceiver channel system. These two modes can be realized by adjusting the waveform generator. It has a simple structure and is easy to use. It can perform rapid imaging and high-precision thickness measurement on the object to be measured.

[0029] 3. The present invention can be better applied in multiple occasions to realize terahertz nondestructive testing imaging, obtain faster and better imaging quality, and realize high-precision thickness measurement. The present invention is particularly suitable for in-situ nondestructive testing and thickness measurement systems for special coatings and structural parts. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 It is a schematic diagram of a terahertz transceiver channel system based on the optical ellipsometry measurement principle of Example 1 of the present invention. DETAILED DESCRIPTION

[0031] In order to have a clearer understanding of the technical features, purposes and effects of the present invention, the specific implementation methods of the present invention are now described. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention, that is, the embodiments described are only part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without making creative work are within the scope of protection of the present invention.

[0032] Example 1

[0033] Current terahertz nondestructive testing technologies mainly include terahertz time-domain spectroscopy measurement technology (THz-TDS) and terahertz frequency-modulated continuous wave imaging technology (THz-FMCW). For in-situ nondestructive testing of certain special coatings and structural parts, such as special coatings on aircraft surfaces or special structural parts such as wings, neither THz-TDS (the traditional distance is too short and the measurement speed is too slow) nor THz-FMCW (the thickness measurement accuracy is insufficient, at the millimeter level) can meet actual needs.

[0034] According to the principle of optical ellipsometric thickness measurement, after the electromagnetic wave is emitted and transmitted through the object to be measured, the intermediate frequency signal received by the detector needs to provide multiple intermediate frequency points. The back end processes the strength of the intermediate frequency signal output amplitude and takes the average to obtain the accurate thickness of the object to be measured. For traditional frequency modulated continuous wave radar, when the modulation waveform is determined, a difference frequency signal (the frequency difference between the received echo signal and the transmitted signal) corresponds to a fixed distance. If the distance is fixed, the difference frequency will not change with time. Now it is necessary to generate multiple difference frequency signals corresponding to a fixed distance according to the requirements of optical ellipsometric thickness measurement, that is, the difference frequency will change with time.

[0035] Based on this, the present embodiment is a terahertz transceiver channel system based on the principle of optical ellipsometric measurement. By changing the modulation waveform of the external input, the waveform of the received echo signal is inconsistent with the waveform of the transmitted signal, so that the difference frequency changes with time to meet the needs of optical ellipsometric thickness measurement. The present embodiment changes the modulation waveform of the external input to realize a terahertz transceiver channel system based on the principle of optical ellipsometric measurement (the received echo signal and the transmitted modulation waveform are inconsistent), which can be used to construct a terahertz thickness measurement system for in-situ non-destructive testing of special coatings and structural parts, thereby realizing accurate measurement of material thickness.

[0036] like Figure 1 As shown, the terahertz transceiver channel system based on the optical ellipsometry measurement principle of this embodiment includes:

[0037] a waveform generator configured to generate a time-varying modulated waveform;

[0038] A terahertz transmitter is configured to generate a terahertz radio frequency signal and modulate it based on a modulation waveform, and then transmit it to the object to be measured at a preset incident angle;

[0039] a polarization optical path configured to polarize a terahertz radio frequency signal emitted by the terahertz transmitter and to polarize a terahertz radio frequency signal reflected by the object to be measured;

[0040] The terahertz detector is configured to receive the terahertz radio frequency signal reflected by the object to be measured and polarized through the polarization light path, thereby realizing the thickness measurement of the object to be measured.

[0041] In this embodiment, by making the terahertz transmitter and the terahertz detector form an angle, and placing a polarized light path between the terahertz transmitter and the terahertz detector; and then by changing the modulation waveform input by the waveform generator, according to the requirements of optical ellipsometric thickness measurement, multiple difference frequency signals are generated to correspond to a fixed distance, thereby realizing a terahertz transceiver channel system based on the optical ellipsometric measurement principle (the received echo signal is inconsistent with the transmitted modulation waveform). The waveform generator inputs different modulation waveforms to the terahertz transmitter, and the terahertz wave signal is emitted. The terahertz signal is polarized, compensated, and detected through the polarized light path, thereby changing the polarization direction of the terahertz signal, and then the surface of the object to be measured is emitted, and finally the radio frequency echo signal enters the terahertz detector for reception, so that the intermediate frequency signal that changes with time can be obtained.

[0042] It can be seen that this embodiment changes the modulation waveform output by the waveform generator so that the waveforms of the received echo signal and the transmitted signal are inconsistent, that is, the frequency difference between the received echo signal and the transmitted signal changes with time, and multiple frequency differences, that is, difference frequency signals, correspond to a fixed distance, thereby realizing optical ellipsometric thickness measurement.

[0043] Preferably, the polarization light path includes an incident light path and a reflected light path, the incident light path is configured to polarize and compensate the terahertz radio frequency signal emitted by the terahertz transmitter, thereby changing the polarization direction of the terahertz radio frequency signal; the reflected light path is configured to compensate and detect the terahertz radio frequency signal reflected by the object to be measured.

[0044] More preferably, the incident light path includes a polarizer and a first compensator, and the terahertz radio frequency signal emitted by the terahertz transmitter is incident on the object to be measured after passing through the polarizer and the first compensator in sequence.

[0045] More preferably, the reflected light path includes a polarizer and a second compensator, and the terahertz radio frequency signal reflected by the object to be measured is transmitted to the terahertz detector after passing through the second compensator and the polarizer in sequence.

[0046] Example 2

[0047] This embodiment provides a terahertz transceiver method based on the optical ellipsometry measurement principle, including:

[0048] A time-varying modulation waveform is generated by a waveform generator;

[0049] A terahertz radio frequency signal is generated by a terahertz transmitter and modulated based on a modulation waveform, and then transmitted to the object to be measured at a preset incident angle;

[0050] Polarize the terahertz radio frequency signal emitted by the terahertz transmitter through a polarization optical path, and polarize the terahertz radio frequency signal reflected by the object to be measured;

[0051] The terahertz radio frequency signal reflected by the object to be measured and polarized through the polarization light path is received by the terahertz detector, thereby realizing the thickness measurement of the object to be measured.

[0052] In this embodiment, by making the terahertz transmitter and the terahertz detector form an angle, and placing a polarized light path between the terahertz transmitter and the terahertz detector; and then by changing the modulation waveform input by the waveform generator, according to the requirements of optical ellipsometric thickness measurement, multiple difference frequency signals are generated to correspond to a fixed distance, thereby realizing a terahertz transceiver channel system based on the optical ellipsometric measurement principle (the received echo signal is inconsistent with the transmitted modulation waveform). The waveform generator inputs different modulation waveforms to the terahertz transmitter, and the terahertz wave signal is emitted. The terahertz signal is polarized, compensated, and detected through the polarized light path, thereby changing the polarization direction of the terahertz signal, and then the surface of the object to be measured is emitted, and finally the radio frequency echo signal enters the terahertz detector for reception, so that the intermediate frequency signal that changes with time can be obtained.

[0053] It can be seen that this embodiment changes the modulation waveform output by the waveform generator so that the waveforms of the received echo signal and the transmitted signal are inconsistent, that is, the frequency difference between the received echo signal and the transmitted signal changes with time, and multiple frequency differences, that is, difference frequency signals, correspond to a fixed distance, thereby realizing optical ellipsometric thickness measurement.

[0054] Preferably, the polarization light path includes an incident light path and a reflected light path, the incident light path is configured to polarize and compensate the terahertz radio frequency signal emitted by the terahertz transmitter, thereby changing the polarization direction of the terahertz radio frequency signal; the reflected light path is configured to compensate and detect the terahertz radio frequency signal reflected by the object to be measured.

[0055] More preferably, the incident light path includes a polarizer and a first compensator, and the terahertz radio frequency signal emitted by the terahertz transmitter is incident on the object to be measured after passing through the polarizer and the first compensator in sequence.

[0056] More preferably, the reflected light path includes a polarizer and a second compensator, and the terahertz radio frequency signal reflected by the object to be measured is transmitted to the terahertz detector after passing through the second compensator and the polarizer in sequence.

[0057] It should be noted that, for the above method embodiments, for the sake of simplicity of description, they are expressed as a series of action combinations, but those skilled in the art should be aware that the present application is not limited by the order of the actions described, because according to the present application, certain steps can be performed in other orders or simultaneously. Secondly, those skilled in the art should also be aware that the embodiments described in the specification are all preferred embodiments, and the actions and modules involved are not necessarily required by the present application.

Claims

1. A terahertz transceiver channel system based on the principle of optical ellipsometry, characterized in that: include: a waveform generator configured to generate a time-varying modulated waveform; A terahertz transmitter is configured to generate a terahertz radio frequency signal and modulate it based on a modulation waveform, and then transmit it to the object to be measured at a preset incident angle; a polarization optical path configured to polarize a terahertz radio frequency signal emitted by the terahertz transmitter and to polarize a terahertz radio frequency signal reflected by the object to be measured; The terahertz detector is configured to receive the terahertz radio frequency signal reflected by the object to be measured and polarized through the polarization light path, thereby realizing the thickness measurement of the object to be measured.

2. The terahertz transceiver channel system based on the optical ellipsometry measurement principle according to claim 1, characterized in that: The waveform generator can change the output modulation waveform so that the waveform of the received echo signal is inconsistent with that of the transmitted signal, that is, the frequency difference between the received echo signal and the transmitted signal changes with time, and multiple frequency differences, that is, difference frequency signals, correspond to a fixed distance, thereby realizing optical ellipsometric thickness measurement.

3. The terahertz transceiver channel system based on the optical ellipsometry measurement principle according to claim 1, characterized in that: The polarization optical path includes an incident optical path and a reflected optical path. The incident optical path is configured to polarize and compensate the terahertz radio frequency signal emitted by the terahertz transmitter, thereby changing the polarization direction of the terahertz radio frequency signal; the reflected optical path is configured to compensate and polarize the terahertz radio frequency signal reflected by the object to be measured.

4. The terahertz transceiver channel system based on the optical ellipsometry measurement principle according to claim 3, characterized in that: The incident light path includes a polarizer and a first compensator. The terahertz radio frequency signal emitted by the terahertz transmitter passes through the polarizer and the first compensator in sequence and then is incident on the object to be measured.

5. The terahertz transceiver channel system based on the optical ellipsometry measurement principle according to claim 3, characterized in that: The reflected light path includes a polarizer and a second compensator. The terahertz radio frequency signal reflected by the object to be measured is transmitted to the terahertz detector after passing through the second compensator and the polarizer in sequence.

6. A terahertz transceiver method based on the optical ellipsometry measurement principle, characterized in that: include: A time-varying modulation waveform is generated by a waveform generator; A terahertz radio frequency signal is generated by a terahertz transmitter and modulated based on a modulation waveform, and then transmitted to the object to be measured at a preset incident angle; Polarize the terahertz radio frequency signal emitted by the terahertz transmitter through a polarization optical path, and polarize the terahertz radio frequency signal reflected by the object to be measured; The terahertz radio frequency signal reflected by the object to be measured and polarized through the polarization light path is received by the terahertz detector, thereby realizing the thickness measurement of the object to be measured.

7. The terahertz transceiver method based on the optical ellipsometry measurement principle according to claim 6, characterized in that: By changing the modulation waveform output by the waveform generator, the waveforms of the received echo signal and the transmitted signal are made inconsistent, that is, the frequency difference between the received echo signal and the transmitted signal changes with time, and multiple frequency differences, i.e., difference frequency signals, correspond to a fixed distance, thereby realizing optical ellipsometric thickness measurement.

8. The terahertz transceiver method based on the optical ellipsometry measurement principle according to claim 6, characterized in that: The polarization optical path includes an incident optical path and a reflected optical path. The incident optical path is configured to polarize and compensate the terahertz radio frequency signal emitted by the terahertz transmitter, thereby changing the polarization direction of the terahertz radio frequency signal; the reflected optical path is configured to compensate and polarize the terahertz radio frequency signal reflected by the object to be measured.

9. The terahertz transceiver method based on the optical ellipsometry measurement principle according to claim 8, characterized in that: The incident light path includes a polarizer and a first compensator. The terahertz radio frequency signal emitted by the terahertz transmitter passes through the polarizer and the first compensator in sequence and then is incident on the object to be measured.

10. The terahertz transceiver method based on the optical ellipsometry measurement principle according to claim 8, characterized in that: The reflected light path includes a polarizer and a second compensator. The terahertz radio frequency signal reflected by the object to be measured is transmitted to the terahertz detector after passing through the second compensator and the polarizer in sequence.

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