使用通道等化技術之高品質太赫茲感測影像重建技術

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研究生：	邱笠瑄 Chiu, Li-Hsuan
論文名稱：	使用通道等化技術之高品質太赫茲感測影像重建技術 High-Quality Terahertz Compressed Sensing Image Reconstruction by Channel Equalization
指導教授：	黃元豪 Huang, Yuan-Hao
口試委員:	蔡佩芸 Tsai, Pei-Yun 陳喬恩 Chen, Chiao-En 沈中安 Shen, Chung-An
學位類別：	碩士 Master
系所名稱：	電機資訊學院 - 通訊工程研究所 Communications Engineering
論文出版年：	2021
畢業學年度：	109
語文別：	中文
論文頁數：	80
中文關鍵詞：	太赫茲、重建影像、壓縮感知、壓縮採樣、高斯光束效應
外文關鍵詞：	Channel Equalization, Gaussian Beam Effect, Modulation Depth Effect
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近年來，發現太赫茲波有強大穿透力與對生物體無害等等實用的特性。如果我們將太赫茲波用於成像的話，它可以應用於醫療診斷、系統檢測、藥物檢測等諸多領域，從而推動了太赫茲成像系統的發展。

本論文中的太赫茲成像系統需要使用半導體製成的空間濾波片。利用聚集在濾波片表面的電子形成一系列隨機濾波片來快速對物體取樣。然而，當濾波片表面聚集的電子因雷射能量不足而無法完全阻擋太赫茲波時，就會產生調製深度效應，對系統造成干擾。此外，太赫茲不均勻地照在空間濾波片上的狀況也降低了基於壓縮感知（CS）的重建性能。為了提高重建影像品質，我們提出了等化的通道來克服太赫茲成像系統上的不理想狀況。

模擬結果證明，使用等化的通道重建影像會有更好的均方誤差（MSE）和結構相似性（SSIM）。與原始通道相比，使用等化的通道可以分別減少兩張不同影像的均方誤差63％及76％，提升兩張影像的結構相似性1464％及2342％

本文重建影像的處理器是為影像大小為N=1024,稀疏性為K=100和測量數據 M=768所設計的。該架構時脈頻率為28.57MHz，吞吐量為46.23幀/秒。

In recent years, terahertz has been used for imaging due to its strong ability to penetrate and its harmlessness to the human body. In this way, it can be applied to many fields, such as medical diagnosis, system testing, drug testing, etc., thus promoting the development of terahertz imaging systems.

The terahertz imaging system in this thesis requires the spatial mask made of semiconductors that use electrons gathered on the surface to form a series of random masks to quickly sample images.
However, when the collective electrons on the surface cannot completely block the terahertz radiation because of insufficient power intensity of the laser, the modulation depth effect occurs and cause interference in the system.
In addition, the uneven illumination of the terahertz Gaussian beam on the spatial mask also reduces the reconstruction performance based on the compressed sensing (CS) method.

To improve the quality of reconstruction, we propose a channel equalizer to recover the non-ideal effects in the terahertz imaging system.
The simulation results demonstrate that using equalized channel has better performance of mean square error (MSE) and structural similarity (SSIM). The results of MSE and SSIM are improved respectively 63%, 1464% for image1 and 76%, 2342% for image2.

The reconstruction processor is designed for the image data N=1024 with sparsity K=100 and the measurement data M=768. The architecture is implemented by TSMC 130um technology and the clock frequency is 28.57 MHz and the throughput is 46.23 frame/sec.

Introduction . . . . . . . . . . . . . . 1
1 Terahertz Compressed Sensing Imaging System . . . . . . . . . . . . . . 1
2 Research Motivation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3
Terahertz Single-Pixel Imaging and Compressed Sensing . . . . . . . . . . . . . .5
1 Terahertz Single-Pixel Imaging Systems . . . . . . . . . . . . . . . . . . . 5
1.1 Model of Terahertz Single-Pixel Imaging Systems . . . . . . . . . 6
2 Compressed Sensing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8
2.1 Model of Compressed Sensing . . . . . . . . . . . . . . . . . . . . 9
3 Reconstruction Algorithms for Compressed Sensing . . . . . . . . . . . . 11
3.1 Orthogonal Matching Pursuit Algorithm . . . . . . . . . . . . . . 11
3.2 Orthogonal Matching Pursuit via Matrix Inversion Bypass Algorithm . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13
Proposed Terahertz CS Imaging Model and Reconstruction Method . . . . . . . . . . . . . . 19
1 Non-ideal Effects in the THz Imaging System . . . . . . . . . . . . . . . 19
2 Modeling of Non-ideal Effects . . . . . . . . . . . . . . . . . . . . . . . . 21
Simulation Results . . . . . . . . . . . . . .29
1 Experiment Sets . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29
1.1 Bronzing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 30
1.2 All Non-ideal Effects in the THz Imaging System . . . . . . . . . 30
1.3 System with Noise . . . . . . . . . . . . . . . . . . . . . . . . . . 32
2 Performance Metrics of Reconstruction . . . . . . . . . . . . . . . . . . . 32
3 Simulation Results . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 34
3.1 Bronzing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 35
3.2 Gaussian Beam effect . . . . . . . . . . . . . . . . . . . . . . . . . 39
3.3 Modulation Depth Effect . . . . . . . . . . . . . . . . . . . . . . . 42
3.4 All Non-ideal Effects . . . . . . . . . . . . . . . . . . . . . . . . . 45
3.5 Simulation with Different σT Hz and σDMD . . . . . . . . . . . . . 51
3.6 Noise in THz Imaging System . . . . . . . . . . . . . . . . . . . . 57
Hardware Design . . . . . . . . . . . . . . 65
1 System Architecture . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 66
1.1 Architecture of Index Selection Unit . . . . . . . . . . . . . . . . 68
1.2 Architecture of Reconstruction Unit . . . . . . . . . . . . . . . . . 70
2 Fixed-point Simulation . . . . . . . . . . . . . . . . . . . . . . . . . . . 70
3 Timing Schedule . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 73
4 Synthesis Result .. . . . . . . . . . . . . . . . . . . 74
Conclusion . . . . . . . . . . . . . .77
References . . . . . . . . . . . . . .79
                                

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