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研究生:劉忠義
研究生(外文):Chung-Yi Liu
論文名稱:以空間光調變器取代動態擴散片於二階同調成像系統之應用與研究
論文名稱(外文):Study and Application of Spatial Light Modulator Used as the Dynamic Diffuser in Second-order Coherent Imaging System
指導教授:徐巍峰
指導教授(外文):Wei-Feng Hsu
口試委員:林晃巖陸儀斌林正峰
口試日期:2012-07-31
學位類別:碩士
校院名稱:國立臺北科技大學
系所名稱:光電工程系研究所
學門:工程學門
學類:電資工程學類
論文種類:學術論文
論文出版年:2012
畢業學年度:100
語文別:中文
論文頁數:42
中文關鍵詞:光斑光斑對比值光斑大小空間光調變器
外文關鍵詞:SpecklesSpeckle contrastSpeckle sizeSpatial light modulator
相關次數:
  • 被引用被引用:0
  • 點閱點閱:289
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  • 下載下載:22
  • 收藏至我的研究室書目清單書目收藏:0
使用同調光源(例如雷射)於光學成像系統時,可以投影出三維的立體影像或者是高解析的二維影像,然而,在同調的光學成像系統中無可避免地會出現光斑(Speckles),使得影像中的微小特徵被光斑雜訊干擾而無法擷取,導致影像品質的下降,一般解決的方法是使用移動的擴散片(Diffuser)來消除光斑,但此舉免不了也會降低影像的解析度。
近年來,以相位式空間光調變器(Spatial light modulator, SLM)來取代擴散片成為一熱門之研究課題,希望能達到以快速顯示隨機相位陣列的方法來取代擴散片的機械式移動,進而達到減低光斑的影響。但是目前的空間光調變器的解析度不足,像素比較大,導致模擬擴散片的效果有限。在論文中,我們採用一個二階同調光學成像系統來探討此一問題,藉著改變第一階光學成像架構的像距來改變光斑大小(Speckle size),也改變了光斑大小對放置在成像面上SLM像素大小的比值,因而在第二階的成像面上可以得知SLM上的隨機相位陣列對光斑現象的影響,進而發展有效的光斑消除方法。
實驗結果顯示,當第一階成像的光斑大小(繞射極限)大於空間光調變器的像素大小時,在第二階成像中的光斑的確被有效的降低。使用兩張光斑圖案疊加的光斑對比值(Speckle contrast)平均降幅約為0.71,這結果符合理論的預估。


Using a coherent light source such as laser in the optical imaging system, one can project three-dimensional stereoscopic images or high-resolution two-dimensional images. However, the coherent optical imaging system inevitably appear speckles, which make the small features in image unable to be retrieved, and thus reduce the image quality. The general solution is to use a moving diffuser to suppress the speckles.
Recently, using phase-mode spatial light modulator (SLM) to substitute the moving diffuser has been widely studied and successfully implemented. Taking advantage of fast display of multiple random phase patterns on the SLM, the mechanical moving device and the diffuser are replaced and the speckles are reduced. However, the poor resolution and large pixel size of the currently-available spatial light modulation are insufficient to fulfill the requirement of this application. It is the goal of the thesis to investigate the condition that a spatial light modulator can replace the diffuser and gain a significant result in reduction of speckles. In the thesis, we used a coherent optical imaging system with two stages of single-lens imaging systems to achieve the goal. By changing the magnification of the first-stage optical imaging system, the speckle size was changed and the ratio of speckle size to SLM''s pixel size in the imaging plane was changed as well. The influence of the random phase arrays displayed in the SLM on speckle phenomenon in the second-stage imaging plane was obtained. Based on the results of the thesis, we can develop a method of reduction of speckles.
The experiment results showed that when the speckle size (diffractive limit) of the first-stage imaging was two times larger than the pixel size of the spatial light modulator, the speckles of the second-stage imaging were effectively reduced. With superposition of two speckle patterns, the average of reduction of the speckle contrast was reduced to 0.71, which confirmed the theoretical estimation in most studies.


中文摘要.................................................i
英文摘要.................................................ii
誌謝.....................................................iv
目錄.....................................................v
表目錄...................................................vi
圖目錄...................................................vii
第一章 緒論.............................................1
1.1 前言............................................1
1.2 研究動機........................................3
1.3 論文架構........................................3
第二章 光斑.............................................5
2.1 光斑現象........................................5
2.1.1 光斑的背景................................5
2.1.2 光斑的形成原因............................6
2.1.3 數學表示式................................7
2.2 光斑的量測參數..................................9
2.3 光斑大小........................................10
2.4 光斑大小的分析方式 ..............................13
2.4.1 分析原理..................................13
2.4.2 以功率頻譜密度分析光斑大小................14
2.4.3 功率頻譜密度之能量分佈....................16
第三章 SLM取代擴散片之成像系統..........................17
3.1 二階光學成像....................................17
3.1.1 一階成像系統 ..............................17
3.1.2 二階同調光學成像系統......................19
3.2 SLM基本介紹.....................................21
3.2.1 液晶空間光調變器的種類....................21
3.2.2 反射式液晶空間光調變器LC-R 2500...........23
第四章 實驗結果.........................................25
4.1 第一階成像之光斑小於SLM像素 .....................25
4.2 第一階成像之光斑約等於SLM像素...................28
4.3 第一階成像之光斑大於SLM像素 .....................32
4.4 數據分析........................................36
第五章 結論.............................................39
參考文獻.................................................41


[1] J. I. Trisnadi, "Speckle contrast reduction in laser projection displays," Proc. SPIE, vol. 4657, 2002, pp. 131-137.
[2] M. L. Jakobsen, H. T. Yura, and S. G. Hanson, "Spatial filtering velocimetry of objective speckles for measuring out-of-plane motion," Applied Optics, vol. 51, no. 9, 2012, pp. 1396-1406.
[3] C. Zhou, J. Wang, C. Wang, and W. Yu, "Rapid processing for statistical properties of laser speckle with thermal spraying surface," Proc. SPIE, vol. 5642, 2005, pp. 592-598.
[4] W. Thomas, C. Middlebrook, and J. Smith, "Laser speckle contrast reduction Measurement using diffractive diffusers," Proc. SPIE, vol. 7232, 2009, p. 72320W.
[5] O. B. Thompson and M. K. Andrews, "Spatial and temporal effects in laser speckle perfusion measurement," Proc. SPIE, vol. 7176, 2009, p. 717604.
[6] Y. Kuratomi, K. Sekiya, H. Sato, T. Kawakami, B. Katagiri, Y. Suzuki, and T. Uchida, "Consideration on the principle of speckle noise observed on laser projection displays," IDW, vol. 2, 2009, pp. 1365-1368.
[7] J. W. Goodman, Speckle Phenomena in Optics: Theory and Applications, Roberts & Company, 2007.
[8] W. F. Hsu and I. L. Chu, "Speckle suppression by integrated sum of fully developed negatively correlated patterns in coherent imaging," Progress In Electromagnetics Research B, vol. 34, 2011, pp. 1-13.
[9] Y. Kuratomi, K. Sekiya, H. Satoh, T. Tomiyama, T. Kawakami, B. Katagiri, Y. Suzuki, and T. Uchida, "Speckle reduction mechanism in laser rear projection displays using a small moving diffuser," J. Opt. Soc. Am. A, vol. 27, no. 8, 2010, pp. 1812-1817.
[10] M. N. Akram, Z. Tong, G. Ouyang, X. Chen, and V. Kartashov, "Laser speckle reduction due to spatial and angular diversity introduced by fast scanning micromirror," Applied Optics, vol. 49, no. 17, 2010, pp. 3297-3304.
[11] M. Elbaum, M. Greenebaum, and M. King, "A wavelength diversity technique for reduction of speckle size," Optics Communications, vol. 5, no. 3, 1972, pp. 171-174.
[12] J. W. Goodman, "Some fundamental properties of speckle," J. Opt. Soc. Am., vol. 66, no. 11, 1976, pp. 1145-1150.
[13] 周民俊,被動式雷射光斑之模擬和量測分析,碩士論文,國立臺北科技大學光電工程所,台北,2011。
[14] 施嘉博,LC-R2500液晶空間光調變器之測定研究,碩士論文,國立臺北科技大學光電工程所,台北,2008。


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