CN209911223U

CN209911223U - Terahertz high-resolution rapid imaging device based on block compressed sensing

Info

Publication number: CN209911223U
Application number: CN201821632885.7U
Authority: CN
Inventors: 王与烨; 任宇琛; 徐德刚; 姚建铨
Original assignee: Tianjin University
Current assignee: Tianjin University
Priority date: 2018-10-09
Filing date: 2018-10-09
Publication date: 2020-01-07
Anticipated expiration: 2028-10-09

Abstract

The utility model discloses a terahertz high resolution quick imaging device now based on blocking compressed sensing, include: the size of a beam is limited by a terahertz wave generated by a terahertz radiation source through a square diaphragm, and the terahertz wave normally enters an imaging object at a vertical angle; the imaging object and the metal mask plate are placed in parallel in the light path; an imaging object is driven by a two-dimensional displacement platform to be sequentially arranged in a light path in a blocking mode, light waves with imaging object information are received and measured by a terahertz wave detector after being modulated by transmission of a metal mask plate, and the obtained data are input into a compressed sensing reconstruction program to obtain a reconstructed image of the part of the imaging object; after all the blocks of the imaging object are placed in the light path and imaged, the images of all the blocks are spliced according to the corresponding sequence of the images on the complete image to obtain an integral imaging result. The utility model discloses a wide light beam of matrix modulation will await measuring the object blocking formation of image and splice again and realize the image reconstruction, has avoided detector saturation problem and reconstruction algorithm calculation efficiency to descend.

Description

Terahertz high-resolution rapid imaging device based on block compressed sensing

Technical Field

The utility model relates to a terahertz wave imaging field especially relates to a terahertz high resolution quick imaging device now based on blocking compression perception.

Background

Terahertz waves are a general term for electromagnetic waves having a frequency in the range of 0.1-10THz, which have some unique properties. The high penetrability of the terahertz waves to nonpolar substances enables the terahertz waves to be applied to the relevant fields of security inspection, anti-terrorism and the like; the low photon energy of the terahertz wave causes the terahertz wave to have less damage to human tissues compared with X-rays, and the terahertz wave has wide application prospect in the field of biomedicine. The imaging technology is an important application field of terahertz waves, and the existing mature terahertz imaging technology comprises point-by-point scanning imaging and array imaging. Point-by-point scanning imaging generally uses a single-pixel detector to receive scanning signals point by point, and has higher imaging quality and sensitivity. However, the imaging speed of this method is limited by shannon's sampling theorem, and it is difficult to realize fast imaging. Array imaging generally uses different kinds of array detectors as receivers of signals, and although real-time imaging can be achieved by receiving array signals for imaging, compared with a single-pixel detector, the array imaging has poor sensitivity to the terahertz wave band and is relatively expensive.

In recent years, researchers have proposed an imaging method based on the compressed sensing theory. As a new imaging theory, the compressive sensing imaging can break through the restriction of the Shannon sampling theorem and accurately reconstruct an image under the condition of low sampling rate. By writing reconstruction algorithms and designing mask matrixes, the application field of compressive sensing imaging has been gradually expanded from the light and microwave bands to the terahertz band. Due to the fact that the theory has the undersampling characteristic, the theory is expected to be capable of making up for the defects of the current terahertz imaging technology. The single-pixel camera system proposed by the university of rice in 2006 is the most classical compressed sensing imaging system, which spatially modulates a visible light signal covering a complete imaged object by constructing a modulation matrix using a digital micromirror array (DMD), and receives and measures the modulated signal using a single-pixel detector.

Because the light intensity received by the single-pixel detector is the intensity superposition of all the modulated light-transmitting units, the imaging resolution is limited by the size of the mask matrix. In addition, when the number of the light-transmitting units is large, the detector may be saturated due to too large intensity, and when the data amount is too large, the calculation efficiency of the reconstruction algorithm is greatly reduced, thereby reducing the imaging speed. The existing single-pixel random sampling block compression imaging system needs to perform analog calculation on different imaging objects in advance, determines a sampling position in an experiment according to a calculation result, enables a terahertz focusing light spot to be incident to a specified position of a sample, and performs compression sensing imaging on acquired data. Therefore, a device and a method capable of realizing high-resolution and fast terahertz wave imaging based on a compressive sensing imaging theory are urgently needed at present.

SUMMERY OF THE UTILITY MODEL

The utility model provides a terahertz high resolution is quick imaging device now based on blocking compressed sensing, the utility model discloses when utilizing compressed sensing theory to carry out terahertz wave formation of image now, realize the image reconstruction of high resolution through the mode that the wide light beam of matrix modulation will await measuring object blocking formation of image was spliced again to avoided the problem that detector saturation problem and reconstruction algorithm computational efficiency descend to the at utmost, improved the imaging speed, see the following description for details:

a terahertz high-resolution fast imaging device based on block compressed sensing, the device comprising:

the size of a beam is limited by a terahertz wave generated by a terahertz radiation source through a square diaphragm, and the terahertz wave normally enters an imaging object at a vertical angle; the imaging object and the metal mask plate are placed in parallel in the light path;

an imaging object is driven by a two-dimensional displacement platform to be sequentially arranged in a light path in a blocking mode, light waves with imaging object information are received and measured by a terahertz wave detector after being modulated by transmission of a metal mask plate, and the obtained data are input into compressed sensing reconstruction to obtain a reconstructed image of the part of the imaging object;

after all the blocks of the imaging object are placed in the light path and imaged, the images of all the blocks are spliced according to the corresponding sequence of the images on the complete image to obtain an integral imaging result.

Further, a Bernoulli random matrix is selected as a modulation matrix in the transmission modulation.

The metal mask plate and the imaging object are driven to switch parts of the metal mask plate and the imaging object in the light path through the one-dimensional displacement platform and the two-dimensional displacement platform respectively.

The utility model provides a technical scheme's beneficial effect is:

1. the two-dimensional platform is adopted to drive the imaging object to move in a block form, and parts are imaged one by one, compared with the traditional imaging method that terahertz light spots cover the whole sample, the problem that the detector is saturated due to overlarge light wave intensity is solved, the problem that the calculation efficiency of a reconstruction algorithm is low due to overlarge data volume under the high-resolution condition is also solved, and then rapid imaging is realized.

2. Compared with the traditional whole sample image reconstruction, the number of modulation matrixes required under the same sampling rate is reduced by adopting a block compression reconstruction mode, so that the metal mask plate is more convenient and cheaper to manufacture, and the light path is easier to adjust and calibrate.

3. The Bernoulli random matrix is adopted to replace a Gaussian random matrix, so that the light modulation effect of the information of the imaging object is better, and higher imaging quality can be obtained.

4. The square diaphragm matched with the size of the object blocks is combined with the modulation matrix to realize the matrix modulation of the terahertz wave wide light beam, the existing focusing light beam single-pixel random point acquisition mode can be replaced, the simulation calculation process before the experiment is avoided, and the universality of the imaging object is stronger.

Drawings

FIG. 1 is a schematic structural diagram of a terahertz high-resolution rapid imaging device based on block compressed sensing;

fig. 2 shows an imaged object (a), and imaging effect diagrams (b), (c), and (d).

In the drawings, the list of component representations is as follows:

1: a terahertz radiation source; 2: a square diaphragm;

3: imaged objects (exemplified by the letter "H"); 4: a metal mask plate;

5: a one-dimensional displacement platform; 6: a two-dimensional displacement platform;

7: a parabolic mirror; 8: terahertz wave detector.

The imaging object 3 is driven by the two-dimensional displacement platform 6 to move transversely and longitudinally, different blocks of the imaging object 3 can be switched to enter a light path when the imaging object moves each time, and the number and the size of the blocks are set according to the imaging resolution and the sampling time to set the optimal parameters.

The hollowed-out part of the metal mask plate 4 is used for transmitting the terahertz waves, and the non-hollowed-out part is used for shielding the terahertz waves. The hollow parts are regarded as numerical values of '1', the non-hollow parts are regarded as numerical values of '0', and the hollow parts and the non-hollow parts are alternately arranged to form the Bernoulli random matrix.

The square diaphragm 2 limits the imaging beam size, which is matched in size to the block size of the imaging object 3 and each bernoulli random matrix size of the metal mask plate 4.

The parabolic mirror 7 converges the light beam carrying the imaging information, and the light beam is received and measured by the terahertz wave detector 8.

Detailed Description

In order to make the objects, technical solutions and advantages of the present invention clearer, embodiments of the present invention are described in further detail below.

Example 1

A terahertz high-resolution fast imaging device based on block compressed sensing, referring to fig. 1, the device comprises: the terahertz radiation source comprises a terahertz radiation source 1, a square diaphragm 2 for limiting light, an imaging object 3 driven by a two-dimensional displacement platform 6, a metal mask plate 4 driven by a one-dimensional displacement platform 5, a parabolic mirror 7 and a terahertz wave detector 8.

During specific implementation, the terahertz radiation source 1 generates terahertz waves to be output, the terahertz waves limit the size of light beams through the square diaphragm 2, the imaging object 3 and the metal mask plate 4 are driven to switch the parts of the imaging object and the metal mask plate in the light path through the one-dimensional displacement platform 5 and the two-dimensional displacement platform 6 respectively, and the terahertz waves are normally incident on the imaging object at a vertical angle.

The terahertz waves carrying the information of the imaging object pass through the metal mask plate 4 and are modulated, and the imaging object 3 and the metal mask plate 4 are placed in parallel in an optical path.

The terahertz waves modulated by the metal mask plate 4 are incident on the parabolic mirror 7 and converged to the focus of the parabolic mirror, and a terahertz wave detector 8 is used near the focus for receiving and measuring.

The metal mask plate 4 is used for realizing transmission modulation of terahertz waves, and a Bernoulli random matrix is selected as a modulation matrix to replace a Gaussian random matrix or a Toeplitz matrix.

The imaging object 3 is sequentially arranged in a light path in blocks under the drive of the two-dimensional displacement platform 6, the number and the size of the blocks are set according to the imaging resolution and the sampling time, the light wave with the imaging object information is received and measured by the terahertz wave detector 8 after being modulated by the metal mask plate 4, and the obtained data is input into the compressed sensing reconstruction to obtain the reconstructed image of the part of the imaging object 3.

After all the blocks of the imaging object 3 are placed in the light path and imaged, the images of all the blocks are spliced according to the corresponding sequence of the images on the complete image, and then the integral imaging result can be obtained. The imaging speed at high resolution is greatly improved.

The above mentioned transmission intensity array, block image stitching and compressed sensing reconstruction recovery algorithms are well known to those skilled in the art.

To sum up, the embodiment of the utility model provides a quick imaging device of terahertz wave high resolution based on blocking compression perception technique can reduce the influence that detector saturation and reconstruction algorithm efficiency reduce in the imaging phase, effectively improves the imaging speed under the high resolution.

Example 2

The feasibility of the device of example 1 was verified with reference to fig. 2, which is described in detail below:

this experiment has simulated the formation of image result that adopts traditional whole compressed sensing, and has adopted the embodiment of the utility model provides an in the imaging result of the compressed sensing of the piecemeal that mentions, as shown in figure 2.

Fig. 2(a) shows an image "phantom" of an object to be imaged with a resolution of 100 × 100. Fig. 2(b) shows the result of imaging by using the conventional global compressed sensing method, wherein the peak signal to noise ratio (PSNR) is 25.28, and the imaging time is 7.84 s. Fig. 2(c) shows the imaging result of the block compressed sensing mentioned in the embodiment of the present invention, the whole image is divided into 25 blocks on the basis of 20 × 20, and the blocks are respectively imaged and then spliced, the PSNR is 47.28, and the imaging time is 3.01 s. Under the condition of the same imaging resolution, on one hand, the PSNR value is increased after the block compression sensing is adopted, and the reconstruction quality of the image is obviously improved; on the other hand, the time required for image formation is reduced, and the image formation speed is faster.

Furthermore, under the condition that the imaging time allows, the resolution of the mask plate is improved to realize the high-resolution imaging of the object under the condition that the size of the imaged object and the number of the blocks are not changed. Fig. 2(d) shows the effect of reconstructing a 150 × 150 resolution "phantom" image with a block size of 30 × 30, a PSNR of 41.31, and a time taken for imaging of 4.97s, so that the present invention can realize high-resolution fast imaging. Through the aforesaid is experimental, verification that can be direct the embodiment of the utility model provides an in the feasibility of device, multiple needs among the practical application have been satisfied, have improved imaging speed.

To sum up, the embodiment of the utility model provides an use the blocking mode to replace traditional whole mode at terahertz compression perception imaging's sampling stage, adopt the mode of the wide light beam of matrix modulation to replace the mode of current single pixel random sampling point, improved terahertz wave high resolution imaging's speed.

The embodiment of the utility model provides a except that doing special explanation to the model of each device, the restriction is not done to the model of other devices, as long as can accomplish the device of above-mentioned function all can.

Those skilled in the art will appreciate that the drawings are only schematic illustrations of preferred embodiments, and the embodiments of the present invention are given the same reference numerals and are not intended to represent the merits of the embodiments.

The above description is only for the preferred embodiment of the present invention, and is not intended to limit the present invention, and any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present invention should be included within the protection scope of the present invention.

Claims

1. A terahertz high-resolution rapid imaging device based on block compressed sensing is characterized by comprising:

the imaging object is sequentially arranged in the light path in a blocking mode under the driving of the two-dimensional displacement platform, the light wave with the imaging object information is received and measured by the terahertz wave detector after being modulated by the transmission of the metal mask plate, and the obtained data is input into the compressed sensing reconstruction to obtain a reconstructed image of the part of the imaging object.

2. The terahertz high-resolution rapid imaging device based on block compressed sensing of claim 1, wherein the modulation matrix in the transmission modulation is a Bernoulli random matrix.

3. The terahertz high-resolution rapid imaging device based on blocking compressive sensing of claim 1, wherein the metal mask plate and the imaging object are driven to switch the portions of the metal mask plate and the imaging object in the optical path through a one-dimensional displacement platform and a two-dimensional displacement platform respectively.