CN102621070B - Two-dimensional terahenz imaging system and imaging method thereof - Google Patents
Two-dimensional terahenz imaging system and imaging method thereof Download PDFInfo
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- CN102621070B CN102621070B CN 201210108140 CN201210108140A CN102621070B CN 102621070 B CN102621070 B CN 102621070B CN 201210108140 CN201210108140 CN 201210108140 CN 201210108140 A CN201210108140 A CN 201210108140A CN 102621070 B CN102621070 B CN 102621070B
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Abstract
The invention discloses a two-dimensional terahenz imaging system and an imaging method thereof. The two-dimensional terahenz imaging system comprises a femtosecond laser, a diffraction beam split device, a laser focusing lens, a terahenz light guide antenna array, a terahenz imaging lens, a terahenz focusing lens and a terahenz detector which are sequentially arranged. When the two-dimensional terahenz imaging system is used for obtaining imaging images, imaging objects are placed between the terahenz imaging lens and the terahenz focusing lens, and then laser emitted by the femtosecond laser triggers the terahenz light guide antenna array to generate a terahenz wave bundle group which is focused on a terahenz wave detector through the terahenz focusing lens to obtain two-dimensional terahenz images. The two-dimensional terahenz imaging system can directly obtain two-dimensional terahenz images and is greatly improved in imaging speed compared with traditional point by point scanningimaging methods, the imaging device requires no terahenz detecting arrays, so that complexity of the system is reduced, and cost is saved.
Description
Technical field
The present invention relates to the optical imagery detection range, specifically is a kind of two-dimentional terahertz imaging system and formation method thereof.
Background technology
THz wave typically refer to frequency range at 0.1 THz to 10 THz(1 THz=10
12Hz) Qu Jian electromagnetic wave is between microwave and infrared light.THz wave has a lot of characteristics, comprises the photon energy of THz wave far below visible light and X ray, only is the per mille of visible light, 1,000,000 of X ray/and, minimum to human body harm; The THz wave wavelength is grown (1 THz～300 μ m), and is less demanding to the sample surfaces roughness when being used for measuring, and is subjected to the material diffuse transmission influence little; THz wave has very strong penetrability to a lot of opaque medium materials as plastics, pottery, leather, semiconductor crystal wafer etc. in addition.These characteristics make the terahertz imaging technology in fields such as quality control and safety detection wide application prospect be arranged.
Traditional optical imaging method normally utilizes the light beam that sends from single source to be expanded the whole imaging object of back irradiation, light beam through imaging object projects (for example sensitive film, CCD camera etc.) on the detection array by an imaging len, because pass through the information that the light beam of target has carried object, on detection array, just can obtain the image of object like this.But this traditional optical imaging method is applied to the Terahertz field and is subject to many limitations.At first be to make the Terahertz detection array, particularly have the Terahertz detection array of enough pixels very difficult, price is very expensive; Secondly the sensitivity of Terahertz detection array is also very low, like this terahertz signal energy is sub-divided into whole detector array and lists the signal to noise ratio (S/N ratio) (Signal to Noise Ratio) that can greatly reduce system, has a strong impact on image quality.Because these reasons, the mode that the present terahertz imaging method that adopts all is based on point by point scanning obtains two dimensional image, obtains a width of cloth Terahertz image like this and need expend a large amount of time, has greatly limited the terahertz imaging The Application of Technology.
Summary of the invention
The technical problem to be solved in the present invention provides a kind of two-dimentional terahertz imaging system and formation method thereof, and it is consuming time long and lack efficient 2-d Terahertz detection array so that can't carry out the problem of two-dimentional Terahertz direct imaging efficiently to solve existing Terahertz point by point scanning formation method.
Technical scheme of the present invention is:
A kind of two-dimentional terahertz imaging system includes the femto-second laser, diffraction light-dividing device, laser focusing lens, terahertz light lead antenna array, terahertz imaging lens, Terahertz condenser lens and the terahertz detector that arrange in turn; Each antenna on the described terahertz light lead antenna array is applied in the AC bias voltage of different frequency respectively.
Described diffraction light-dividing device is selected spectro-grating for use.
Described terahertz detector is selected Terahertz power detector or Terahertz field detector for use.
The formation method of a kind of two-dimentional terahertz imaging system may further comprise the steps:
(1), earlier imaging object is positioned between terahertz imaging lens and the Terahertz condenser lens;
(2), the laser beam that sends of femto-second laser is divided into aplanatic, as to be equidistant array distribution sets of beams through the diffraction light-dividing device, sets of beams shines on the terahertz light lead antenna array terahertz wave beam group that produces isocandela, is array distribution through laser focusing lens;
(3), the terahertz wave beam group shines on the imaging object through behind the terahertz imaging lens, the terahertz wave beam group through imaging object is converged on the terahertz wave detector by the Terahertz condenser lens then, obtains two-dimentional Terahertz image.
The design concept of the present invention's two dimension terahertz imaging system is:
According to the light path principle of reversibility, if in imaging system, replace detection array with array of source, replace single source with single detector, the point of each on the array of source is equivalent to a pixel like this, each point on the corresponding imaging object; Carrier wave through imaging object converges on the single detector by condenser lens, as long as the signal that each point source sends on the array of source is distinguishable, just can obtain the information of the signal that each point source sends like this with single detector simultaneously, thereby obtain the two-dimensional image information of object.
The laser beam group correspondence on terahertz light lead antenna array that is produced by the diffraction light-dividing device excites generation terahertz wave beam group.Utilize the terahertz wave beam group to carry out two-dimensional imaging as light source, needing each bundle THz wave is distinguishable at the single terahertz detector of terminal.This can realize by the AC bias voltage that each antenna on the terahertz light lead antenna array is applied different frequency.When laser excitation terahertz light lead antenna produces THz wave, apply frequency at antenna and be
fAC bias voltage, be equivalent to THz wave is modulated, modulating frequency is
fAccordingly, apply AC bias voltage for each the photoconduction antenna on the photoconduction aerial array, and frequency has nothing in common with each other, each Terahertz wave source is modulated like this.In end of probe, utilize phase-locked detection technique, just can the signal (pixel) that each terahertz light lead antenna is sent be distinguished, thereby obtain two-dimentional Terahertz image.
Advantage of the present invention is:
The two-dimentional terahertz imaging device of employing diffraction light-dividing device of the present invention light splitting can directly obtain two-dimentional Terahertz image, and the more traditional point by point scanning formation method of image taking speed improves greatly.Each terahertz light lead antenna needs the exciting power of about 10 mW, and the femtosecond laser of a 1W output can be divided into the sets of beams of 10X10 by the diffraction light-dividing device, the photoconduction aerial array of deexcitation 10X10, and image taking speed can improve 100 times in theory like this.And this imaging device do not need to adopt the Terahertz detection array, and this has also reduced the complexity of system, has saved cost.
Description of drawings
Fig. 1 is the use structural representation of the present invention's two dimension terahertz imaging system.
Embodiment
See Fig. 1, a kind of two-dimentional terahertz imaging system includes the femto-second laser 1, diffraction light-dividing device 2, laser focusing lens 3, terahertz light lead antenna array 4, terahertz imaging lens 5, Terahertz condenser lens 7 and the terahertz detector 8 that arrange in turn; Diffraction light-dividing device 2 is selected spectro-grating for use; Terahertz detector 8 is selected Terahertz power detector or Terahertz field detector for use; Each antenna on the terahertz light lead antenna array 4 is applied in the AC bias voltage of different frequency respectively.
See Fig. 1, the formation method of a kind of two-dimentional terahertz imaging system may further comprise the steps:
(1), earlier imaging object 6 is positioned between terahertz imaging lens 5 and the Terahertz condenser lens 7;
(2), the laser beam that sends of femto-second laser 1 is divided into aplanatic, as to be equidistant array distribution sets of beams through diffraction light-dividing device 2, sets of beams shines on the terahertz light lead antenna array 4 the terahertz wave beam group that produces isocandela, is array distribution through laser focusing lens 3;
(3), the terahertz wave beam group shines on the imaging object 6 after through terahertz imaging lens 5, the terahertz wave beam group through imaging object 6 is converged on the terahertz wave detector 8 by Terahertz condenser lens 7 then, obtains two-dimentional Terahertz image.
Each antenna on the terahertz light lead antenna array 4 applies AC bias voltage, and the frequency of the alternating voltage on each antenna is all inequality, when the laser that sends when femto-second laser 1 causes terahertz light lead antenna array 4 and produces THz wave, apply frequency at antenna and be
fAC bias voltage, be equivalent to THz wave is modulated, modulating frequency is
fBecause the antenna that laser causes on the terahertz light lead antenna array 4 has all applied alternating voltage, every like this bundle THz wave is all modulated, and modulating frequency is all inequality.In end of probe, the output signal of terahertz detector 8 inserts lock-in amplifier, at this moment, with the reference signal of the AC signal identical with the modulating frequency of a certain antenna as lock-in amplifier, the signal that has only this antenna to send like this can be measured by lock-in amplifier, and the signal of other antenna is all filtered.Change the frequency of reference signal successively, just can obtain the signal that corresponding antenna sends.According to numbering and the corresponding signal that records of antenna, structure is painted two dimensional image again.Also can utilize a plurality of lock-in amplifier parallel measurements, to save the time that reference signal is measured that changes successively, improve image taking speed.
Present embodiment is to utilize the terahertz wave beam that sees through imaging object to come object is carried out imaging, also can be used to obtain the image information of imaging object in addition through the THz wave of the reflection of imaging object surface or scattering, the inventive method also can directly be used in both cases.
Claims (4)
1. a two-dimentional terahertz imaging system is characterized in that: include the femto-second laser, diffraction light-dividing device, laser focusing lens, terahertz light lead antenna array, terahertz imaging lens, Terahertz condenser lens and the terahertz detector that arrange in turn; Each antenna on the described terahertz light lead antenna array is applied in the AC bias voltage of different frequency respectively.
2. a kind of two-dimentional terahertz imaging according to claim 1 system, it is characterized in that: described diffraction light-dividing device is selected spectro-grating for use.
3. a kind of two-dimentional terahertz imaging according to claim 1 system, it is characterized in that: described terahertz detector is selected Terahertz power detector or Terahertz field detector for use.
4. the formation method of a kind of two-dimentional terahertz imaging according to claim 1 system is characterized in that: may further comprise the steps:
(1), earlier imaging object is positioned between terahertz imaging lens and the Terahertz condenser lens;
(2), the laser beam that sends of femto-second laser is divided into aplanatic, as to be equidistant array distribution sets of beams through the diffraction light-dividing device, sets of beams shines on the terahertz light lead antenna array terahertz wave beam group that produces isocandela, is array distribution through laser focusing lens;
(3), the terahertz wave beam group shines on the imaging object through behind the terahertz imaging lens, the terahertz wave beam group through imaging object is converged on the terahertz wave detector by the Terahertz condenser lens then, obtains two-dimentional Terahertz image.
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| CN103411891A (en) * | 2013-07-29 | 2013-11-27 | 南开大学 | Terahertz (THz) super-resolution imaging method and system |
| CN103454255B (en) * | 2013-09-02 | 2016-04-13 | 中国科学院上海微系统与信息技术研究所 | A kind of THz wave scanning imaging system and method |
| CN105548080B (en) * | 2016-01-15 | 2018-07-31 | 北京工业大学 | A kind of continuous THz wave spacescan coherent diffraction imaging system and method |
| CN107631995B (en) * | 2016-07-18 | 2020-02-14 | 华中科技大学 | Three-dimensional terahertz tomography system and scanning and image reconstruction method |
| CN106645015A (en) * | 2016-11-16 | 2017-05-10 | 上海理工大学 | TeraHertz wave super-resolution imaging system and method based on metal micro-nano structure |
| CN108303709A (en) * | 2018-01-17 | 2018-07-20 | 深圳翠博微系统有限公司 | A kind of Terahertz helmet-type imager |
| CN108680500A (en) * | 2018-03-30 | 2018-10-19 | 莆田学院 | A kind of the terahertz time-domain spectroscopy instrument device and analysis method of miniaturization |
| CN111879722B (en) * | 2020-08-03 | 2023-06-27 | 中电科思仪科技股份有限公司 | System and method for improving resolution of terahertz wave nondestructive detection |
| CN113008172B (en) * | 2021-03-03 | 2022-09-27 | 北京理工大学 | Terahertz wave-based ice and snow track inspection device and method |
| CN113267823A (en) * | 2021-05-14 | 2021-08-17 | 南开大学 | Large-depth-of-field imaging lens for terahertz frequency band |
| CN114486804B (en) * | 2021-12-29 | 2024-04-05 | 江南大学 | Broadband terahertz wave image reconstruction system |
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