Terahertz Pulse Reflection Imaging Using the Time-Domain Correlating Synthesis Method

Self Cite

We have introduced a correlating synthesis (CS) method for high-resolution terahertz (THz) imaging. The efficiency of the CS method was verified by imaging experiment of metal cylinders using a pulse reflection mode terahertz time-domain-spectrometry system. In this paper, we study the influence of layered dielectric in the propagation path of THz wave. A method of propagation time correction by ray tracing in the dielectric layer is proposed. The efficiency on decreasing the distortion and artifact images is verified by imaging experiment with a dielectric substrate board. Moreover, it is noticed that the appropriate correlation interval used in CS processing depends on the shape of the target. We propose a method of synthesizing the images derived from a series of different correlation intervals, which ensures the robustness of parameter independent with the target. The efficiency of the proposed method is verified by comparison imaging experiments using samples of different targets on a substrate board.

Section: Experimental Imaging Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

THz wave imaging through layered dielectric using correlating synthesis method

Ishizaki

Toh

Suizu

2020

Self Cite

“…A THz time-domain spectrometer (THz-TDS) is employed for THz wave irradiating and detecting, which was described more detailed in Ref. 19. Figure 1 shows the geometric schematic of our experimental system.…”

Section: Experimental Systemmentioning

confidence: 99%

“…In previous works, we demonstrated a correlating synthesis (CS) method and its efficiency in improving imaging resolution. [15][16][17][18][19][20][21] Instead of linear summation of back projected signals shown in Eq. ( 3), the CS method emphasizes the correlations between back projections by introducing multiplications, as shown in Eq.…”

Section: Introductionmentioning

confidence: 99%

Terahertz wave imaging using time domain iterative shrink threshold method

Kaneoya,

Toh,

Suizu

2023

Self Cite

We propose a new linear imaging method that combines the iterative shrinkage thresholding algorithm (ISTA) with the synthetic aperture (SA) method to achieve high resolution. Unlike other ISTA methods that use a single frequency component of signals, we use time domain signals directly as measurement, which allows for simultaneous wide bandwidth calculation and potentially better imaging results. Additionally, we simplify the backward estimation process by using impulse back-projection based on the SA method, which reduces the computing cost compared to the ISTA method. Numerical simulation and experimental measurement results show that the image resolution is similar to that of our previous non linear imaging method, and two reflectors with different reflectivity are imaged linearly. These comparison results demonstrate the effectiveness of our proposed method in achieving high-resolution and maintaining the linearity of target reflectivity.

“…The methods of THz imaging can also be roughly divided into two categories, raster scanning of the sample with a focused THz-beam, [4][5][6][7][8][9][10][11] and synthetic processing of signals acquired from different positions with unfocused THz-beams. [12][13][14][15][16][17][18][19][20] The raster scanning methods usually use tightly focused THz beam to realize high spatial resolution, but the trade-off between the focus waist and the focus depth restrains their measurable depth ranges, and the sample needs to be located strictly in the tight beam spot area. Whereas, the synthetic processing methods achieve high resolution by processing signals of unfocused THz beam, and hence broader measurable three-dimensional (3D) area can be realized.…”

Section: Introductionmentioning

confidence: 99%

Terahertz imaging for multiple reflectors using time-domain correlating synthesis method

Sato

Toh

Suizu

2018

Self Cite

We had proposed a correlating synthesis method for terahertz imaging using a pulse reflection mode terahertz time-domain spectrometry system. The efficiency of the method for improving the resolution and eliminating fake images was verified by numerical simulations and experiments with two metal cylinders. However, an artifact image between the two reflectors is markedly shown. Moreover, the multi-reflection and the influence of echo distortion caused by the directivity of the terahertz beam have not been discussed. For application of imaging complicated target, this paper addresses following issues: 1) multi-reflection between reflectors, as well as the effect of the direction of polarization of terahertz wave; 2) distortion of echo signals from targets distributed in a broader area, as well as the effect of concave lenses. Finally, the efficiencies of these proposals are verified by an imaging experiment with five metal cylinders.