CN113075132A - Reflection type terahertz microscopic imaging system and method based on electro-optic effect - Google Patents
Reflection type terahertz microscopic imaging system and method based on electro-optic effect Download PDFInfo
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- G01N21/00—Investigating or analysing materials by the use of optical means, i.e. using sub-millimetre waves, infrared, visible or ultraviolet light
- G01N21/17—Systems in which incident light is modified in accordance with the properties of the material investigated
- G01N21/21—Polarisation-affecting properties
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- G—PHYSICS
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- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N21/00—Investigating or analysing materials by the use of optical means, i.e. using sub-millimetre waves, infrared, visible or ultraviolet light
- G01N21/17—Systems in which incident light is modified in accordance with the properties of the material investigated
- G01N21/55—Specular reflectivity
- G01N21/552—Attenuated total reflection
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- G01N21/00—Investigating or analysing materials by the use of optical means, i.e. using sub-millimetre waves, infrared, visible or ultraviolet light
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Abstract
The application discloses reflection-type terahertz microscopic imaging system and method based on electro-optic effect, after terahertz wave and a sample to be imaged are coupled, the electro-optic effect is generated on an electro-optic crystal, so that the polarization field of probe light is changed, the probe light carries the modulation effect of the terahertz wave coupled with the sample to be imaged, and the image information of the sample to be imaged is obtained through an image imaging module according to the probe light. The polarization field of the detection light is changed through the electro-optic effect without adopting a probe scanning mode, the image information of the sample to be imaged can be obtained through the detection light, micron-sized real-time microscopic imaging can be realized, the microscopic imaging speed and the structural stability are improved, meanwhile, the attenuation total reflection module is adopted, imaging is carried out according to the detection light instead of imaging according to terahertz waves coupled with the sample to be imaged, and the technical problem that the microscopic imaging effect of a fresh sample containing more water is poor is solved.
Description
Technical Field
The application relates to the technical field of terahertz imaging, in particular to a reflection type terahertz microscopic imaging system and method based on an electro-optic effect.
Background
With the development of terahertz technology, terahertz real-time microscopic imaging has the irreplaceable advantage of visible light and infrared frequency bands in the aspects of defect detection of semiconductor wafer materials and nano materials and biomedical pathology analysis.
In the existing terahertz microscopic imaging products, regardless of whether an atomic force probe is adopted to realize nanoscale microscopy or a terahertz probe is adopted to realize micron-scale microscopy, a probe point-by-point scanning mode is generally adopted. The speed of microscopic imaging is very low, and meanwhile, the distance between the probe and the imaged medium is difficult to control, so that the risk of breaking the probe is high, and the speed and the structural stability of the probe microscopic imaging mode are difficult to meet the requirements of industrial online detection. Meanwhile, when the fresh sample containing more water is subjected to microscopic imaging, the absorption of terahertz waves is serious, and the effect of the microscopic imaging is poor.
Disclosure of Invention
The application provides a reflection type terahertz microscopic imaging system and method based on an electro-optic effect, which are used for solving the technical problems of low microscopic imaging speed, poor structural stability and poor microscopic imaging effect on fresh samples with more moisture.
In view of this, the present application provides, in a first aspect, a reflective terahertz microscopic imaging system based on an electro-optical effect, including: the terahertz wave detector comprises a terahertz wave source, a detection light source, an attenuated total reflection module, an electro-optic crystal, a polarizer, a beam splitter, an analyzer and an image imaging module;
the terahertz wave source is used for transmitting terahertz waves;
the outer surface of the attenuation total reflection module is attached to a sample to be imaged, the attenuation total reflection module is arranged on an optical outlet path of the terahertz wave source, and is used for receiving the terahertz wave emitted by the terahertz wave source, coupling the terahertz wave with the sample to be imaged and reflecting the coupled terahertz wave to the electro-optic crystal;
the detection light source is used for emitting detection light;
the polarizer is arranged on an optical path of the detection light source and is used for receiving the detection light and then enabling the detection light to be incident into the beam splitter;
the working surface of the beam splitter is at an angle of 45 degrees with respect to the working surface of the polarizer, and the beam splitter is used for receiving the detection light passing through the polarizer, so that the detection light is divided into two beams, and one beam of the detection light is incident into the electro-optic crystal;
the electro-optical crystal is arranged on a light path between the attenuated total reflection module and the beam splitter, and is used for respectively receiving the terahertz waves and the detection light reflected by the attenuated total reflection module and the beam splitter so as to generate an electro-optical effect to change the polarization field of the detection light, and is also used for reflecting the detection light after the polarization field is changed so as to return the detection light along the original light path and enter the image imaging module through the beam splitter and the analyzer;
the image imaging module is used for obtaining the image information of the sample to be imaged according to the detection light.
Preferably, the detection light source adopts a laser.
Preferably, the surface of the electro-optic crystal, which is far away from the beam splitter, is plated with an antireflection film for reflecting the detection light, and the surface of the electro-optic crystal, which is close to the beam splitter, is plated with an antireflection film for transmitting the detection light.
Preferably, the attenuated total reflection module is specifically an attenuated total reflection prism.
Preferably, a convex lens is arranged on the light-emitting path of the analyzer.
Preferably, the image imaging module comprises a CCD camera and a computer;
the CCD camera is used for receiving the detection light to obtain corresponding image information and transmitting the image information to the computer;
the computer is used for removing background noise of the image information based on pre-acquired initial image information without the sample to be imaged.
Preferably, the image imaging module comprises a spatial light modulator, a single-pixel detector and a computer, and the spatial light modulator and the single-pixel detector are electrically connected with the computer;
the spatial light modulator is arranged on a light path between the analyzer and the convex lens and is used for carrying out spatial coding modulation on the detection light to generate a coding matrix;
the single-pixel detector is arranged on the light-emitting path of the convex lens and used for receiving the detection light modulated by the spatial coding of the spatial light modulator so as to obtain corresponding total signal power;
and the computer is used for reconstructing the image matrix of the sample to be imaged by adopting a preset compressive sensing algorithm according to the total signal power and the coding matrix so as to obtain the image information of the sample to be imaged.
In a second aspect, the invention provides a reflective terahertz microscopic imaging method based on an electro-optic effect, which applies the reflective terahertz microscopic imaging system based on the electro-optic effect, and comprises the following steps:
transmitting a terahertz wave to the attenuated total reflection module through a terahertz wave source;
receiving the terahertz waves emitted by the terahertz wave source through the attenuated total reflection module, coupling the terahertz waves with a sample to be imaged, which is attached to the outer surface of the terahertz waves, and then reflecting the coupled terahertz waves into the electro-optic crystal;
emitting detection light to the polarizer through the detection light source and then entering the beam splitter;
receiving the detection light passing through the polarizer by the beam splitter, so that the detection light is split into two beams, and one beam of the detection light is incident into the electro-optic crystal;
after the terahertz waves and the detection light reflected by the attenuated total reflection module and the beam splitter are respectively received by the electro-optic crystal, an electro-optic effect is generated to change the polarization field of the detection light, then the detection light with the changed polarization field is reflected to return along the original light path, and the detection light is incident into an image imaging module through the beam splitter and an analyzer;
and obtaining the image information of the sample to be imaged according to the detection light through the image imaging module.
Preferably, the image imaging module comprises a CCD camera and a computer;
the step of obtaining the image information of the sample to be imaged according to the detection light by the image imaging module specifically includes:
the CCD camera receives the detection light to obtain corresponding image information, and the image information is transmitted to the computer;
removing background noise of the image information based on pre-acquired initial image information without the sample to be imaged, so as to obtain the image information of the sample to be imaged.
Preferably, the image imaging module comprises a spatial light modulator, a single-pixel detector and a computer, and the spatial light modulator and the single-pixel detector are electrically connected with the computer;
the step of obtaining the image information of the sample to be imaged according to the detection light by the image imaging module specifically includes:
performing spatial coding modulation on the detection light through the spatial light modulator to generate a coding matrix;
receiving the detection light subjected to spatial coding modulation by the spatial light modulator through the single-pixel detector so as to obtain corresponding total signal power;
and reconstructing an image matrix of the sample to be imaged by adopting a preset compressive sensing algorithm according to the total signal power and the coding matrix through the computer, so as to obtain the image information of the sample to be imaged.
According to the technical scheme, the embodiment of the application has the following advantages:
according to the reflection type terahertz microscopic imaging system and method based on the electro-optic effect, after the terahertz waves are coupled with the sample to be imaged, the electro-optic effect is generated on the electro-optic crystal, so that the polarization field of the detection light is changed, the detection light carries the modulation effect of the terahertz waves coupled with the sample to be imaged, and the image information of the sample to be imaged is obtained through the image imaging module according to the detection light. The polarization field of the detection light is changed through the electro-optic effect without adopting a probe scanning mode, the image information of the sample to be imaged can be obtained through the detection light, micron-sized real-time microscopic imaging can be realized, the microscopic imaging speed and the structural stability are improved, meanwhile, the attenuation total reflection module is adopted, imaging is carried out according to the detection light instead of imaging according to terahertz waves coupled with the sample to be imaged, and the technical problem that the microscopic imaging effect of a fresh sample containing more water is poor is solved.
Drawings
Fig. 1 is a schematic structural diagram of a reflective terahertz microscopic imaging system based on an electro-optic effect according to a first embodiment of the present application;
fig. 2 is a schematic structural diagram of a reflective terahertz microscopic imaging system based on an electro-optic effect according to a second embodiment of the present application;
fig. 3 is a schematic structural diagram of a reflective terahertz microscopic imaging system based on an electro-optic effect according to a third embodiment of the present application;
fig. 4 is a flowchart of a reflective terahertz microscopic imaging method based on an electro-optic effect according to a first embodiment of the present application.
Detailed Description
In order to make the technical solutions of the present application better understood, the technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the drawings in the embodiments of the present application, and it is obvious that the described embodiments are only a part of the embodiments of the present application, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present application.
For easy understanding, referring to fig. 1, the present invention provides a reflective terahertz microscopic imaging system based on an electro-optic effect, including: the terahertz wave detector comprises a terahertz wave source 1, a detection light source 2, an attenuated total reflection module 3, an electro-optic crystal 4, a polarizer 5, a beam splitter 6, an analyzer 7 and an image imaging module 8;
the terahertz wave source 1 is used for emitting terahertz waves;
the outer surface of the attenuated total reflection module 3 is attached to a sample 9 to be imaged, the attenuated total reflection module 3 is arranged on an optical outlet path of the terahertz wave source 1, and is used for receiving the terahertz waves emitted by the terahertz wave source 1, coupling the terahertz waves with the sample 9 to be imaged and reflecting the coupled terahertz waves to the electro-optic crystal 4;
in this embodiment, the attenuated total reflection module 3 is specifically an attenuated total reflection prism, which includes a parallelogram terahertz prism, a hyper-hemisphere terahertz lens and a dove prism, and the attenuated total reflection prism is generally made of a high-resistance silicon material.
It can be understood that the coupling effect between the terahertz wave and the high-absorptivity sample can be enhanced by adopting the attenuated total reflection prism.
The detection light source 2 is used for emitting detection light;
in this embodiment, the detection light source 2 is a laser, and the central wavelength of the emitted laser beam is generally 780nm or 1550nm, and meanwhile, the emission mode of the laser beam may be either pulsed or continuous. When an ultrafast process of the interaction of the terahertz waves and a tested sample needs to be detected, femtosecond pulse laser is adopted; when only imaging is required and no dynamic process detection is required, a continuous laser may be used.
The polarizer 5 is arranged on an optical path of the detection light source 2 and is used for receiving the detection light and then transmitting the detection light into the beam splitter 6;
the working surface of the beam splitter 6 and the working surface of the polarizer 5 form an angle of 45 degrees, and the beam splitter is used for receiving the detection light passing through the polarizer 5, so that the detection light is divided into two beams, and one beam of the detection light is incident into the electro-optic crystal 4;
the electro-optical crystal 4 is arranged on a light path between the attenuated total reflection module 3 and the beam splitter 6, and is used for respectively receiving the terahertz waves and the detection light reflected by the attenuated total reflection module 3 and the beam splitter 6 so as to generate an electro-optical effect to change the polarization field of the detection light, and is also used for reflecting the detection light after the polarization field is changed so as to return the detection light along the original light path, and the detection light is incident into the image imaging module 8 through the beam splitter 6 and the analyzer 7;
in this embodiment, the polarizer 5 screens the polarization of the probe light, and the beam splitter 6 is a polarization beam splitter whose energy reflectivity or transmittance is sensitive to the polarization. The beam splitter 6 has high reflectivity and low transmissivity to the detection light which is subjected to polarization screening by the oscillator, and the transmissivity and the reflectivity are selective to the polarization direction of the detection light, so that the polarization field of the detection light reflected back by the electro-optical crystal 4 is changed by the electro-optical effect, and the detection light can pass through the reflected detection light and enter the image imaging module 8 through the analyzer 7.
In this embodiment, the electro-optical crystal 4 is ZnTe or LiNbO3The electro-optical crystal is made of electro-optical crystal materials, and the electro-optical crystal 4 and the terahertz waves can generate interaction, so that the polarization field of the detection light can be changed, and the effect is also called as an electro-optical effect.
Meanwhile, in this embodiment, the surface of the electro-optical crystal 4 away from the beam splitter 6 is plated with an antireflection film for reflecting the detection light, and the surface of the electro-optical crystal 4 close to the beam splitter 6 is plated with an antireflection film for transmitting the detection light. Thereby, the reflection performance and the transmission performance of the detection light can be improved, and the image imaging quality and efficiency can be improved.
The image imaging module 8 is used for obtaining image information of the sample 9 to be imaged according to the detection light.
It should be noted that the working process of this embodiment is as follows:
the terahertz wave source 1 emits terahertz waves which are coupled with a sample 9 to be imaged through the attenuated total reflection module 3, the coupled terahertz waves are incident to the electro-optic crystal 4, meanwhile, the detection light emitted by the detection light source 2 is incident to the electro-optic crystal 4 through the polarizer 5 and the beam splitter 6 in sequence, so that a polarization field is changed by an electro-optic effect generated by the terahertz waves and the electro-optic crystal 4, and the terahertz waves are reflected by the electro-optic crystal 4 and then return to the original path to be incident to the image imaging module 8 through the beam splitter 6 and the analyzer 7 in sequence to be imaged. Because the detection light with the changed polarization field is modulated by the terahertz wave coupled with the sample 9 to be imaged, the detection light carries the modulation effect of the terahertz wave coupled with the sample 9 to be imaged, and the change of the polarization field of the detection light by the terahertz wave after coupling is different from the change of the polarization field of the detection light by the terahertz wave without the coupling effect of the sample to be imaged. The difference between the polarization fields of the probe light before and after the polarization field is caused by the sample 9 to be imaged, so that the image information of the sample 9 to be imaged can be obtained from the probe light in the image imaging module 8. The embodiment does not need to adopt a probe scanning mode, changes the polarization field of the probe light through the electro-optic effect, and can obtain the image information of the sample 9 to be imaged through the probe light, can realize micron-sized real-time microscopic imaging, and improves the microscopic imaging speed and the structural stability, and meanwhile, the embodiment performs imaging according to the probe light instead of performing imaging according to terahertz waves coupled with the sample 9 to be imaged, thereby solving the technical problem of poor microscopic imaging effect of a fresh sample with more moisture.
The above is a detailed description of a first embodiment of the reflective terahertz microscopic imaging system based on the electro-optic effect provided by the present invention, and the following is a detailed description of a second embodiment of the reflective terahertz microscopic imaging system based on the electro-optic effect provided by the present invention.
For convenience of understanding, referring to fig. 2, the present invention provides a reflective terahertz microscopic imaging system based on an electro-optic effect, including: the terahertz wave detector comprises a terahertz wave source 1, a detection light source 2, an attenuated total reflection module 3, an electro-optic crystal 4, a polarizer 5, a beam splitter 6, an analyzer 7, a CCD camera 81 and a computer, wherein a convex lens 10 is arranged on a light outlet path of the analyzer 7;
the terahertz wave source 1 is used for emitting terahertz waves;
the outer surface of the attenuated total reflection module 3 is attached to a sample 9 to be imaged, the attenuated total reflection module 3 is arranged on an optical outlet path of the terahertz wave source 1, and is used for receiving the terahertz waves emitted by the terahertz wave source 1, coupling the terahertz waves with the sample 9 to be imaged and reflecting the coupled terahertz waves to the electro-optic crystal 4;
in this embodiment, the attenuated total reflection module 3 is specifically an attenuated total reflection prism, which includes a parallelogram terahertz prism, a hyper-hemisphere terahertz lens and a dove prism, and the attenuated total reflection prism is generally made of a high-resistance silicon material.
It can be understood that the coupling effect between the terahertz wave and the high-absorptivity sample can be enhanced by adopting the attenuated total reflection prism.
The detection light source 2 is used for emitting detection light;
in this embodiment, the detection light source 2 is a laser, which is matched with the CCD camera 81, and the central wavelength of the emitted laser beam is generally 780nm or 1550nm, and meanwhile, the emission mode of the laser beam may be either pulsed or continuous. When an ultrafast process of the interaction of the terahertz waves and a tested sample needs to be detected, femtosecond pulse laser is adopted; when only imaging is required and no dynamic process detection is required, a continuous laser may be used.
The polarizer 5 is arranged on an optical path of the detection light source 2 and is used for receiving the detection light and then transmitting the detection light into the beam splitter 6;
the working surface of the beam splitter 6 and the working surface of the polarizer 5 form an angle of 45 degrees, and the beam splitter is used for receiving the detection light passing through the polarizer 5, so that the detection light is divided into two beams, and one beam of the detection light is incident into the electro-optic crystal 4;
the electro-optical crystal 4 is arranged on a light path between the attenuated total reflection module 3 and the beam splitter 6, and is used for respectively receiving the terahertz waves and the detection light reflected by the attenuated total reflection module 3 and the beam splitter 6 so as to generate an electro-optical effect to change the polarization field of the detection light, and is also used for reflecting the detection light after the polarization field is changed so as to return the detection light along the original light path, and the detection light is incident into the convex lens 10 through the beam splitter 6 and the analyzer 7;
in this embodiment, the polarizer 5 screens the polarization of the probe light, and the beam splitter 6 is a polarization beam splitter whose energy reflectivity or transmittance is sensitive to the polarization. The beam splitter 6 has high reflectivity and low transmissivity to the detection light which is subjected to polarization screening by the vibration generator, and the transmissivity and the reflectivity are selective to the polarization direction of the detection light, so that the polarization field of the detection light reflected back by the electro-optical crystal 4 is changed by the electro-optical effect, the detection light can be reflected back and is incident into the convex lens 10 through the analyzer 7, and the detection light is converged.
In this embodiment, the electro-optical crystal 4 is ZnTe or LiNbO3The electro-optical crystal is made of electro-optical crystal materials, and the electro-optical crystal 4 and the terahertz waves can generate interaction, so that the polarization field of the detection light can be changed, and the effect is also called as an electro-optical effect.
Meanwhile, in this embodiment, the surface of the electro-optical crystal 4 away from the beam splitter 6 is plated with an antireflection film for reflecting the detection light, and the surface of the electro-optical crystal 4 close to the beam splitter 6 is plated with an antireflection film for transmitting the detection light. Thereby, the reflection performance and the transmission performance of the detection light can be improved, and the image imaging quality and efficiency can be improved.
The CCD camera 81 is used for receiving the detection light and obtaining corresponding image information, and is also used for transmitting the image information to a computer;
in this embodiment, the CCD camera 81 can be an ultrafast camera, can record femtosecond ultrafast processes, and has a strong application value for recording the dynamic processes of semiconductor carriers.
The computer is used for removing the background noise of the image information based on the pre-acquired initial image information of the sample 9 not placed to be imaged.
It should be noted that, in the embodiment, after the CCD camera 81 receives the detection light, the computer compares the difference between the image information of the sample 9 to be imaged and the image information of the sample 9 not to be imaged, and the image information of the sample 9 not to be imaged is used as the reference background, so that the background noise influence of the image information of the sample 9 not to be imaged can be eliminated, and the imaging is more accurate.
The above is a detailed description of a second embodiment of the reflective terahertz microscopic imaging system based on the electro-optic effect provided by the present invention, and the following is a detailed description of a third embodiment of the reflective terahertz microscopic imaging system based on the electro-optic effect provided by the present invention.
For convenience of understanding, referring to fig. 3, the present invention provides a reflective terahertz microscopic imaging system based on an electro-optic effect, including: the terahertz wave polarization detector comprises a terahertz wave source 1, a detection light source 2, an attenuated total reflection module 3, an electro-optic crystal 4, a polarizer 5, a beam splitter 6, an analyzer 7, a spatial light modulator 82, a single-pixel detector 83 and a computer, wherein a convex lens 10 is arranged on a light outlet path of the analyzer 7;
the terahertz wave source 1 is used for emitting terahertz waves;
the outer surface of the attenuated total reflection module 3 is attached to a sample 9 to be imaged, the attenuated total reflection module 3 is arranged on an optical outlet path of the terahertz wave source 1, and is used for receiving the terahertz waves emitted by the terahertz wave source 1, coupling the terahertz waves with the sample 9 to be imaged and reflecting the coupled terahertz waves to the electro-optic crystal 4;
in this embodiment, the attenuated total reflection module 3 is specifically an attenuated total reflection prism, which includes a parallelogram terahertz prism, a hyper-hemisphere terahertz lens and a dove prism, and the attenuated total reflection prism is generally made of a high-resistance silicon material.
It can be understood that the coupling effect between the terahertz wave and the high-absorptivity sample can be enhanced by adopting the attenuated total reflection prism.
The detection light source 2 is used for emitting detection light;
in this embodiment, the detection light source 2 is a laser, and the central wavelength of the emitted laser beam is generally 780nm or 1550nm, and meanwhile, the emission mode of the laser beam may be either pulsed or continuous. When an ultrafast process of the interaction of the terahertz waves and a tested sample needs to be detected, femtosecond pulse laser is adopted; when only imaging is required and no dynamic process detection is required, a continuous laser may be used.
The polarizer 5 is arranged on an optical path of the detection light source 2 and is used for receiving the detection light and then transmitting the detection light into the beam splitter 6;
the working surface of the beam splitter 6 and the working surface of the polarizer 5 form an angle of 45 degrees, and the beam splitter is used for receiving the detection light passing through the polarizer 5, so that the detection light is divided into two beams, and one beam of the detection light is incident into the electro-optic crystal 4;
the electro-optical crystal 4 is arranged on a light path between the attenuated total reflection module 3 and the beam splitter 6, and is used for respectively receiving the terahertz waves and the detection light reflected by the attenuated total reflection module 3 and the beam splitter 6 so as to generate an electro-optical effect to change the polarization field of the detection light, and is also used for reflecting the detection light after the polarization field is changed so as to return the detection light along the original light path, and the detection light is incident into the convex lens 10 through the beam splitter 6 and the analyzer 7;
in this embodiment, the polarizer 5 screens the polarization of the probe light, and the beam splitter 6 is a polarization beam splitter whose energy reflectivity or transmittance is sensitive to the polarization. The beam splitter 6 has high reflectivity and low transmissivity to the detection light which is subjected to polarization screening by the vibration generator, and the transmissivity and the reflectivity are selective to the polarization direction of the detection light, so that the polarization field of the detection light reflected back by the electro-optical crystal 4 is changed by the electro-optical effect, the detection light can be reflected back and is incident into the convex lens 10 through the analyzer 7, and the detection light is converged.
In this embodiment, the electro-optical crystal 4 is ZnTe or LiNbO3The electro-optical crystal is made of electro-optical crystal materials, and the electro-optical crystal 4 and the terahertz waves can generate interaction, so that the polarization field of the detection light can be changed, and the effect is also called as an electro-optical effect.
Meanwhile, in this embodiment, the surface of the electro-optical crystal 4 away from the beam splitter 6 is plated with an antireflection film for reflecting the detection light, and the surface of the electro-optical crystal 4 close to the beam splitter 6 is plated with an antireflection film for transmitting the detection light. Thereby, the reflection performance and the transmission performance of the detection light can be improved, and the image imaging quality and efficiency can be improved.
The spatial light modulator 82 and the single-pixel detector 83 are both electrically connected to a computer;
the spatial light modulator 82 is arranged on the light path between the analyzer 7 and the convex lens 10, and is used for performing spatial coding modulation on the detection light to generate a coding matrix;
the single-pixel detector 83 is arranged on the light-emitting path of the convex lens 10 and is used for receiving the detection light after being spatially coded and modulated by the spatial light modulator 82, so as to obtain corresponding total signal power;
the computer is used for reconstructing an image matrix of the sample 9 to be imaged by adopting a preset compression sensing algorithm according to the total signal power and the coding matrix, so as to obtain image information of the sample 9 to be imaged.
It should be noted that the process of reconstructing the image matrix of the sample 9 to be imaged specifically includes:
setting the number of image pixels of the sample 9 to be imaged to be reconstructed as N, and setting the target image matrix as N14×N14Matrix array element, omegai,jRepresenting a coding matrix, namely on-off information of spatial distribution of the ith spatial coding mask, wherein 0 in the matrix is closed, 1 is connected, j represents the dictionary ordering of the coding matrix from 1 to N, psijAnd the distribution of a two-dimensional matrix of the detection light is shown, namely the jth array element ordered according to the dictionary sequence, and the two-dimensional matrix adopts a Hadamard matrix. Then for each measurement (ith), the total signal power phi received by the single-pixel detector 83iFor coding the matrix omegai,jWith the two-dimensional matrix ΨjThe scalar product of the one-dimensional vectors of (a), is noted as:
meanwhile, the Hadamard matrix satisfies the following relationship:
in the formula, H represents a Hadamard matrix, n represents the order of the matrix, I represents an identity matrix, and T is a transposed symbol;
then equation (2) can be converted to:
selecting an nth-order Hadamard matrix (N is N x N) unchanged, and constructing two matrices through an encoding matrix, wherein one matrix comprises all positive elements and is marked as a matrix V; and the other matrix comprises all negative elements, and the absolute value of all the negative elements is taken as the corresponding element value, and is recorded as a matrix G, so that the Hadamard matrix is recorded as:
H＝V-G (4)
wherein H satisfies formula (2);
by changing the irradiation conditions in the spatial light modulator 82, the single-pixel detector 83 is used for N times of measurement, and the relational expression of an N-order matrix Hadamard matrix is obtained as follows:
Φ＝WΨ (5)
where Φ is represented as a one-dimensional column vector, where each element is a measurement of a single pixel detector 83; w is expressed as an n-order Hadamard matrix; Ψ represents n dictionary orderings for the target image to be reconstructed;
when W is an nth-order Hadamard matrix and W is a reversible matrix, it is obtained according to equations (3) and (5):
and after n dictionary sequences psi of the target image to be reconstructed are obtained through solving, sequencing the target image matrix, thereby obtaining the image matrix of the sample 9 to be imaged.
It should be noted that, if multiple measurements are difficult to implement, an algorithm of compressive sensing and super-resolution reconstruction may be used to reconstruct an image, and two-dimensional distribution of a target image is obtained according to a least squares error rule, specifically:
the low-resolution array detector can adopt algorithms of compressive sensing and super-resolution reconstruction to perform area array receiving on coded and modulated detection light and perform m times of area array measurement (times m)<<N), defining a low-dimensional matrix of the low-resolution array detector as yiThe dictionary ordering of the target high resolution images needing to be reconstructed is xjThen, obtaining:
in the formula, ωiSelecting a transformation matrix for carrying out different permutation and combination on the row vectors of the Hadamard matrix; p is the average projection operator, i.e. the average is taken over the matrix blocks corresponding to the n-order matrix.
Obtaining the dictionary ordering x of the target high-resolution image to be reconstructed by solving the formula (7)jThen, the target image matrix is sorted, so that the image matrix of the sample 9 to be imaged is obtained.
The above is a detailed description of a third embodiment of the reflective terahertz microscopic imaging system based on the electro-optic effect provided by the present invention, and the following is a detailed description of a first embodiment of the reflective terahertz microscopic imaging method based on the electro-optic effect provided by the present invention.
In this embodiment, the reflective terahertz microscopic imaging system based on the electro-optic effect in the above embodiments is applied, and for convenience of understanding, referring to fig. 4, the present invention provides a reflective terahertz microscopic imaging method based on the electro-optic effect, including the following steps:
s101: transmitting a terahertz wave to the attenuated total reflection module through a terahertz wave source;
s102: receiving terahertz waves emitted by a terahertz wave source through an attenuated total reflection module, coupling the terahertz waves with a sample to be imaged, which is attached to the outer surface of the terahertz waves, and then reflecting the coupled terahertz waves into an electro-optic crystal;
s103: emitting detection light to the polarizer through the detection light source and then entering the beam splitter;
s104: receiving the detection light passing through the polarizer by a beam splitter, so that the detection light is divided into two beams, and one beam of the detection light is incident into an electro-optic crystal;
s105: after receiving the terahertz waves and the detection light reflected by the attenuated total reflection module and the beam splitter respectively through the electro-optic crystal, generating an electro-optic effect to change a polarization field of the detection light, then reflecting the detection light after changing the polarization field, returning the detection light along an original light path, and making the detection light incident into the image imaging module through the beam splitter and the analyzer;
s106: and obtaining image information of the sample to be imaged according to the detection light through an image imaging module.
It should be noted that, in this embodiment, after the terahertz wave is coupled with the sample to be imaged, an electro-optic effect is generated on the electro-optic crystal, so as to change the polarization field of the detection light, so that the detection light carries the modulation effect of the terahertz wave coupled with the sample to be imaged, and compared with the terahertz wave without the coupling effect of the sample to be imaged, the terahertz wave after coupling has a difference in the change of the polarization field of the detection light. The difference of the polarization fields of the detection light before and after the polarization field is caused by the sample to be imaged, so that the image information of the sample to be imaged can be obtained according to the detection light in the image imaging module. The embodiment does not need to adopt a probe scanning mode, changes the polarization field of the probe light through the electro-optic effect, and can obtain the image information of the sample to be imaged through the probe light, can realize the real-time microscopic imaging of micron order, and improve the microscopic imaging speed and structural stability.
The above is a detailed description of a first embodiment of the reflective terahertz microscopic imaging method based on the electro-optic effect provided by the present invention, and the following is a detailed description of a second embodiment of the reflective terahertz microscopic imaging method based on the electro-optic effect provided by the present invention.
The difference between the reflective terahertz microscopic imaging method based on the electro-optic effect provided by the present embodiment and the reflective terahertz microscopic imaging method based on the electro-optic effect provided by the first embodiment is characterized in that: the image imaging module comprises a CCD camera and a computer;
step S106 specifically includes:
s206: receiving the detection light through a CCD camera to obtain corresponding image information, and transmitting the image information to a computer;
s207: removing background noise of the image information based on the pre-acquired initial image information without the sample to be imaged, thereby obtaining the image information of the sample to be imaged.
It should be noted that, in this embodiment, after the CCD camera receives the detection light, the computer compares the difference between the image information of the sample to be imaged and the image information of the sample not to be imaged, and the image information of the sample not to be imaged is used as the reference background, so that the background noise influence of the image information of the sample not to be imaged can be eliminated, and the imaging is more accurate.
The above is a detailed description of the second embodiment of the reflective terahertz microscopic imaging method based on the electro-optic effect provided by the present invention, and the following is a detailed description of the third embodiment of the reflective terahertz microscopic imaging method based on the electro-optic effect provided by the present invention.
The difference between the reflective terahertz microscopic imaging method based on the electro-optic effect provided by the present embodiment and the reflective terahertz microscopic imaging method based on the electro-optic effect provided by the first embodiment is characterized in that: the image imaging module comprises a spatial light modulator, a single-pixel detector and a computer, wherein the spatial light modulator and the single-pixel detector are electrically connected with the computer;
step 106 specifically includes:
306: carrying out spatial coding modulation on the detection light through a spatial light modulator to generate a coding matrix;
307: receiving the detection light modulated by the spatial coding of the spatial light modulator through a single-pixel detector so as to obtain corresponding total signal power;
308: and the computer is used for reconstructing an image matrix of the sample to be imaged by adopting a preset compressive sensing algorithm according to the total signal power and the coding matrix, so that the image information of the sample to be imaged is obtained.
It should be noted that the process of reconstructing the image matrix of the sample to be imaged specifically includes:
setting the number of image pixels of a sample to be imaged needing to be reconstructed as N, wherein N is more than or equal to 2 and omegai,jRepresenting the coding matrix, i.e. the on-off information of the spatial distribution for the ith spatially coded reticleWhere 0 in the matrix is denoted as off, 1 is denoted as on, j denotes the coding matrix dictionary ordering, from 1 to N, ΨjAnd the distribution of a two-dimensional matrix of the detection light is shown, namely the jth array element ordered according to the dictionary sequence, and the two-dimensional matrix adopts a Hadamard matrix. The total signal power received by the single pixel detector is then phi for each measurement (ith time)iFor coding the matrix omegai,jWith the two-dimensional matrix ΨjThe scalar product of the one-dimensional vectors of (a), is noted as:
meanwhile, the Hadamard matrix satisfies the following relationship:
in the formula, H represents a Hadamard matrix, n represents the order of the matrix, I represents an identity matrix, and T is a transposed symbol;
then equation (2) can be converted to:
selecting an nth-order Hadamard matrix (N is N x N) unchanged, and constructing two matrices through an encoding matrix, wherein one matrix comprises all positive elements and is marked as a matrix V; and the other matrix comprises all negative elements, and the absolute value of all the negative elements is taken as the corresponding element value, and is recorded as a matrix G, so that the Hadamard matrix is recorded as:
H＝V-G (4)
wherein H satisfies formula (2);
by changing the irradiation condition in the spatial light modulator and using the single-pixel detector to perform N times of measurement, the relational expression of an N-order matrix Hadamard matrix is obtained as follows:
Φ＝WΨ (5)
in the formula, phi is expressed as a one-dimensional column vector, wherein each element is a primary measurement value of a single-pixel detector; w is expressed as an n-order Hadamard matrix; Ψ represents n dictionary orderings for the target image to be reconstructed;
when W is an nth-order Hadamard matrix and W is a reversible matrix, it is obtained according to equations (3) and (5):
and after n dictionary sequences psi of the target image to be reconstructed are obtained through solving, sequencing the target image matrix, and thus obtaining the image matrix of the sample to be imaged.
It should be noted that, if multiple measurements are difficult to implement, an algorithm of compressive sensing and super-resolution reconstruction may be used to reconstruct an image, and two-dimensional distribution of a target image is obtained according to a least squares error rule, specifically:
the low-resolution array detector can adopt algorithms of compressive sensing and super-resolution reconstruction to perform area array receiving on coded and modulated detection light and perform m times of area array measurement (times m)<<N), defining a low-dimensional matrix of the low-resolution array detector as yiThe dictionary ordering of the target high resolution images needing to be reconstructed is xjThen, obtaining:
in the formula, ωiSelecting a transformation matrix for carrying out different permutation and combination on the row vectors of the Hadamard matrix; p is the average projection operator, i.e. the average is taken over the matrix blocks corresponding to the n-order matrix.
Obtaining the dictionary ordering x of the target high-resolution image to be reconstructed by solving the formula (7)jAnd sequencing the target image matrix to obtain the image matrix of the sample to be imaged.
In the several embodiments provided in the present application, it should be understood that the disclosed apparatus and method may be implemented in other ways. For example, the above-described apparatus embodiments are merely illustrative, and for example, the division of the units is only one logical division, and other divisions may be realized in practice, for example, a plurality of units or components may be combined or integrated into another system, or some features may be omitted, or not executed. In addition, the shown or discussed mutual coupling or direct coupling or communication connection may be an indirect coupling or communication connection through some interfaces, devices or units, and may be in an electrical, mechanical or other form.
The units described as separate parts may or may not be physically separate, and parts displayed as units may or may not be physical units, may be located in one place, or may be distributed on a plurality of network units. Some or all of the units can be selected according to actual needs to achieve the purpose of the solution of the embodiment.
In addition, functional units in the embodiments of the present application may be integrated into one processing unit, or each unit may exist alone physically, or two or more units are integrated into one unit. The integrated unit can be realized in a form of hardware, and can also be realized in a form of a software functional unit.
The above embodiments are only used to illustrate the technical solutions of the present application, and not to limit the same; although the present application has been described in detail with reference to the foregoing embodiments, it should be understood by those of ordinary skill in the art that: the technical solutions described in the foregoing embodiments may still be modified, or some technical features may be equivalently replaced; and such modifications or substitutions do not depart from the spirit and scope of the corresponding technical solutions in the embodiments of the present application.
Claims (10)
1. A reflection-type terahertz microscopic imaging system based on an electro-optic effect is characterized by comprising: the terahertz wave detector comprises a terahertz wave source, a detection light source, an attenuated total reflection module, an electro-optic crystal, a polarizer, a beam splitter, an analyzer and an image imaging module;
the terahertz wave source is used for transmitting terahertz waves;
the outer surface of the attenuation total reflection module is attached to a sample to be imaged, the attenuation total reflection module is arranged on an optical outlet path of the terahertz wave source, and is used for receiving the terahertz wave emitted by the terahertz wave source, coupling the terahertz wave with the sample to be imaged and reflecting the coupled terahertz wave to the electro-optic crystal;
the detection light source is used for emitting detection light;
the polarizer is arranged on an optical path of the detection light source and is used for receiving the detection light and then enabling the detection light to be incident into the beam splitter;
the working surface of the beam splitter is at an angle of 45 degrees with respect to the working surface of the polarizer, and the beam splitter is used for receiving the detection light passing through the polarizer, so that the detection light is divided into two beams, and one beam of the detection light is incident into the electro-optic crystal;
the electro-optical crystal is arranged on a light path between the attenuated total reflection module and the beam splitter, and is used for respectively receiving the terahertz waves and the detection light reflected by the attenuated total reflection module and the beam splitter so as to generate an electro-optical effect to change the polarization field of the detection light, and is also used for reflecting the detection light after the polarization field is changed so as to return the detection light along the original light path and enter the image imaging module through the beam splitter and the analyzer;
the image imaging module is used for obtaining the image information of the sample to be imaged according to the detection light.
2. The electro-optic effect based reflective terahertz microscopic imaging system according to claim 1, wherein the detection light source adopts a laser.
3. The system according to claim 1, wherein a surface of the electro-optic crystal, which is far from the beam splitter, is coated with an antireflection film for reflecting the probe light, and a surface of the electro-optic crystal, which is close to the beam splitter, is coated with an antireflection film for transmitting the probe light.
4. The electro-optic effect based reflective terahertz microscopic imaging system according to claim 1, wherein the attenuated total reflection module is specifically an attenuated total reflection prism.
5. The electro-optic effect based reflective terahertz microscopic imaging system according to claim 1, wherein a convex lens is arranged on the light-emitting path of the analyzer.
6. The electro-optic effect based reflective terahertz microscopic imaging system according to claim 1 or 5, wherein the image imaging module comprises a CCD camera and a computer;
the CCD camera is used for receiving the detection light to obtain corresponding image information and transmitting the image information to the computer;
the computer is used for removing background noise of the image information based on pre-acquired initial image information without the sample to be imaged.
7. The electro-optic effect based reflective terahertz microscopic imaging system according to claim 5, wherein the image imaging module comprises a spatial light modulator, a single-pixel detector and a computer, wherein the spatial light modulator and the single-pixel detector are electrically connected with the computer;
the spatial light modulator is arranged on a light path between the analyzer and the convex lens and is used for carrying out spatial coding modulation on the detection light to generate a coding matrix;
the single-pixel detector is arranged on the light-emitting path of the convex lens and used for receiving the detection light modulated by the spatial coding of the spatial light modulator so as to obtain corresponding total signal power;
and the computer is used for reconstructing the image matrix of the sample to be imaged by adopting a preset compressive sensing algorithm according to the total signal power and the coding matrix so as to obtain the image information of the sample to be imaged.
8. The reflection type terahertz microscopic imaging method based on the electro-optic effect is applied to the reflection type terahertz microscopic imaging system based on the electro-optic effect, and is characterized by comprising the following steps:
transmitting a terahertz wave to the attenuated total reflection module through a terahertz wave source;
receiving the terahertz waves emitted by the terahertz wave source through the attenuated total reflection module, coupling the terahertz waves with a sample to be imaged, which is attached to the outer surface of the terahertz waves, and then reflecting the coupled terahertz waves into the electro-optic crystal;
emitting detection light to the polarizer through the detection light source and then entering the beam splitter;
receiving the detection light passing through the polarizer by the beam splitter, so that the detection light is split into two beams, and one beam of the detection light is incident into the electro-optic crystal;
after the terahertz waves and the detection light reflected by the attenuated total reflection module and the beam splitter are respectively received by the electro-optic crystal, an electro-optic effect is generated to change the polarization field of the detection light, then the detection light with the changed polarization field is reflected to return along the original light path, and the detection light is incident into an image imaging module through the beam splitter and an analyzer;
and obtaining the image information of the sample to be imaged according to the detection light through the image imaging module.
9. The electro-optic effect based reflective terahertz microscopic imaging method according to claim 8, wherein the image imaging module comprises a CCD camera and a computer;
the step of obtaining the image information of the sample to be imaged according to the detection light by the image imaging module specifically includes:
the CCD camera receives the detection light to obtain corresponding image information, and the image information is transmitted to the computer;
removing background noise of the image information based on pre-acquired initial image information without the sample to be imaged, so as to obtain the image information of the sample to be imaged.
10. The electro-optic effect based reflective terahertz microscopic imaging method according to claim 8, wherein the image imaging module comprises a spatial light modulator, a single-pixel detector and a computer, and the spatial light modulator and the single-pixel detector are electrically connected with the computer;
the step of obtaining the image information of the sample to be imaged according to the detection light by the image imaging module specifically includes:
performing spatial coding modulation on the detection light through the spatial light modulator to generate a coding matrix;
receiving the detection light subjected to spatial coding modulation by the spatial light modulator through the single-pixel detector so as to obtain corresponding total signal power;
and reconstructing an image matrix of the sample to be imaged by adopting a preset compressive sensing algorithm according to the total signal power and the coding matrix through the computer, so as to obtain the image information of the sample to be imaged.
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