THz影像系統---子計畫一：微小化THz CMOS影像系統之3D影像重建技術

Abstract

近年來，THz電磁波(300 GHz-3THz，T-射線)在科學與工程上之應用已引起廣泛之研究。相較於X-射線(X-ray)而言，T-射線為非離子化幅射光源(non-ionization radiation)，適合進行生物組織之非侵入式偵測而較無輻射疑慮。因此其被公認為下世代醫學影像系統之重大關鍵技術。此外，其具備穿透衣服及其他非金屬化材質之特性，因此可廣泛應用在安檢系統之影像監測、化學與生物物質偵測，腫瘤、蛀牙之醫學影像等。同時在短距離雷達及超高速無線資料安全傳輸等應用，也深具潛力。 然而，由於其THz波長遠大於X-ray波長，使得X-ray之成像方式不適用於THz系統，原因在於偵測物體之尺寸通常與波長相近，尤其是物體介電函數與周遭環境之介電值相差大時，繞射效應不可忽略，必須使用電磁逆散射法(Electromagnetic Inverse Scattering Method)THz波成像方式。而測量的方式可分為兩類，一為包含電場振幅與相位的量測法，另一種為只有電場振幅(或強度)的量測法。本子計畫(一)將根據其他子計畫提出之直線或平面陣列式THz波源(source)與偵測器(detector)設計架構，同時運用上述兩種量測法，搭配無關聯照射法(Unrelated Illumination)、梯度法(Gradient Method)、變形波爾迭代法(Distorted Born Iterative Method)與基因演算法(Genetic Algorithm)等演算法，建立最佳之成像方式，並整合建立運用CMOS技術之微小化THz近即時三維成像系統。 本三年期總計畫「微小化THz CMOS影像系統」具體目標為發展微小化THz CMOS影像系統建立3D影像重建技術，同時建構核心元件之自製能力及建立THz信號頻譜之量測能力，並應用於各種影像檢測。本總計畫延攬多方面領域之教授，涵蓋光學影像系統、電路與微機電封裝、到基礎物理研究等領域。其下統合四項子計畫，分別為：(一)微小化THz CMOS影像系統之3D影像重建技術、(二) THz CMOS 波束成形發射機、(三)微小化THz CMOS主動式射頻照影接收器陣列系統晶片、(四) THz CMOS被動式影像接收器。本子計畫(一)如上所述之「微小化THz CMOS影像系統之3D影像重建技術」第一年將對於二維的電磁逆散射問題，利用同時具相位與振幅的資訊或是只具振幅的資訊兩種量測方式，搭配無關聯照射法(Unrelated Illumination)、梯度法(Gradient Method)、變形波爾迭代法(Distorted Born Iterative Method)與基因演算法(Genetic Algorithm)等演算法，以建立最佳之二維成像方式；第二年則運用第一年度發展的二維成像電磁逆散射演算最佳方法，配合其他子計畫發展之二維陣列波源與偵測器，建構三維成像技術的演算法；第三年則配合發展其他子計畫之二維陣列波源與偵測器，加速三維成像技術演算法之計算速度，利用GPU或是CPU平行運算，達成近即時三維成像系統，以整合建立運用CMOS技術之微小化THz近即時三維成像系統。

THz wave (300GHz–3THz, T-ray) applications in scientific and engineering applications have drawn tremendous research efforts recently. In contrast to X-ray, it is a non-ionized light source for non-invasive detection of biological tissues without the concern of much radiation exposure. Thus it is believed as an emerging technology for next generation medical imaging system. Additionally, T-ray is capable to penetrate clothing and many (non-metallic) packaging materials. It opens up unique screening possibilities for detection of concealed weapons, chemicals and biological agents, tumors, cavities, and also opportunities for short range radars and secured high data rate wireless communications. Because the THz wavelength is much larger than the X-ray wavelength, the imaging method of X-ray isn't suitable for the THz imaging system. It is the fact that the THz wavelength is comparable to the size of the detected object, which results in the diffraction effect obviously, especially in a situation when the dielectric contrast between the detected object and circumstance is large. The possible way for THz imaging is to adopt the electromagnetic inverse scattering method. Based on the measurement method, it can be further classified into two categories, one is the measurement with amplitude and phase information, and the other is that with intensity only. The objective goal of this 3-year “Miniaturized THz CMOS Imaging System”joint project is to build up a small THz CMOS imaging system through the developing of THz core devices as well as establishing the measurement techniques for THz spectrum. This project leverages efforts and experts from aspects of optical imaging system, circuits and packaging design, to fundamental physics researchers. It incorporates 4 sub-projects (1) 3D Imaging Reconstruction Technology for a Miniaturized THz CMOS Imaging System, (2) THz CMOS Beam Forming Transmitter, (3) Miniaturized Terahertz CMOS Active RF imaging receiver array integrated system, (4) THz CMOS passive imaging receiver. For this sub-project (1) “3D Imaging Reconstruction Technology for a Miniaturized THz CMOS Imaging System”, two measurement methods described above will be used be used to develop 3D Imaging reconstruction technology with based on the design of source and detector arrays developed by other subjects. Several algorithms, such as the unrelated illumination method, the modified gradient method, the distorted Born iterative method, and the genetic algorithm will be investigated to optimize the imaging technology. The 2D imaging technology will be developed in the first year. In the second year, the 3D imaging technology will be developed. In the third year, the optimized 3D imaging technology will be developed and a prototype of a miniaturized THz CMOS imaging system will be built up.