THz wave imaging through layered dielectric using correlating synthesis method

Abstract

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.

Terahertz wave imaging using time domain iterative shrink threshold method

“…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.…”

Terahertz reflection imaging using virtual arrays and MUSIC in a synthetic aperture array

“…[6][7][8][9][10][11][12][13][14] Synthetic aperture arrays (SAAs) using unfocused beams are promising candidates to increase the spatial resolution of terahertz images while reducing the restrictions on target placement. [15][16][17][18][19][20][21][22][23][24][25][26] SAAs can obtain a substantially large aperture by moving the transmitting and/or receiving antennas, making it possible to scan the beam and reduce the beamwidth by signal processing. SAA has been widely used in various applications, including radar and ultrasonic sensing.…”

“…21) Toh showed the effectiveness of correlating synthesis method proposed in ultrasonic field measurement for THz-TDS reflection imaging. [22][23][24] SAA is also needed for time reversal terahertz imaging. [18][19][20] Three-dimensional terahertz imaging using SAA has also been investigated.…”