利用液晶顯示器之Fresnel電腦全像術; Fresnel Computer-Generated Hologram Using TFT Active Matrix Liquid Crystal Display

Please use this identifier to cite or link to this item: http://ir.lib.ncu.edu.tw/handle/987654321/6920

Title:	利用液晶顯示器之Fresnel電腦全像術;Fresnel Computer-Generated Hologram Using TFT Active Matrix Liquid Crystal Display
Authors:	王楨;Jane Wang
Contributors:	光電科學研究所
Keywords:	全像術;液晶;liquid crystal;hologram
Date:	2006-07-09
Issue Date:	2009-09-22 10:32:09 (UTC+8)
Publisher:	國立中央大學圖書館
Abstract:	液晶顯示器的操作原理為施加電壓後改變液晶傾斜角度，進而改變對非尋常光的折射率。本論文的研究即是利用此折射率的改變來控制入射光的相位，使穿過液晶的平行光因每一個像素的相位不同而呈現出能展現立體影像的資訊。因為各家出產的液晶顯示器不盡相同，所以每一片的液晶都有不同的參數(偏轉角度、快慢軸方位、傾斜角度)，一開始只能利用具有某些特別偏振方向、特別波長的入射光來一一求出每個不同的參數，之後再利用這些參數來完成灰階值對應相位變化的圖表，最後再利用這張圖表來設定不同的灰階來得到所需要的相位。本研究所使用的液晶顯示器對相位的控制只能180度左右，因此我們利用均方根誤差來選取適當的相位顯示範圍。又因為液晶顯示器控制了光波相位之後，振幅只能為固定的定值，因此我們採取一維同心迴光板(zone plate)的方式來展式立體影像。在論文的後半部我們也在全像片上顯示區域的切割設計上做出討論，以拉近了成像區與顯示器間的距離。在製作出一組特定旋轉角度的物體影像之後，我們又繼續利用視覺暫留，以每秒三十張全像片的更新速率展示不同旋轉角度的物體影像來製作出動畫。 Liquid crystal display (LCD) device utilizes the change of the tilted angle of individual liquid crystal molecules, controlled by the applied voltage, to change the shape of index ellipsoid. Our research uses this change to control the relative phase shift of the incident wavefront and then the phase-modulated light produces a 3-D Fresnel image. The characteristics of every liquid crystal display, such as direction of extraordinary axis, twisted angle and tilted angle of liquid crystal, are generally different. At first, we utilize several lights of particular polarizations and particular wavelengths to determine all the above parameters. Then, we use these parameters to establish a phase shift versus gray level table. Finally, base upon this table, we draw a picture of size 1024x768 pixels on the LCD to modulate the phase of the incident light. The LCD we use for our research is the type EPSON L3P10X, which can only produce relative phase change for incident wavefront up to 180 degree. Therefore, we use root-mean-square error to choose the proper range of phase modulation. Since our LCD can’t control the phase as well as the amplitude of incident wavefront simultaneously, we then adopt the method of one-dimensional zone plate to generate the desired 3-D image. By dividing the hologram plane into many sections and addressing proper information on each section, the distance of the 3-D image from the LCD device can be shortened. With a series of 3-D images of different viewing angles in hand, we then use “persistence of vision” to demonstrate the animation of a rotating cube.
Appears in Collections:	[Graduate Institute of Optics and Photonics] Electronic Thesis & Dissertation

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