本文關(guān)鍵詞： 衍射場(chǎng) 點(diǎn)云 全息圖 采樣 查找表 對(duì)稱性　出處：《安徽大學(xué)》2017年碩士論文　論文類型：學(xué)位論文

【摘要】：全息顯示能夠提供幾乎等同于真實(shí)世界的三維圖像,能充分地傳遞人類感知三維物體的所有深度刺激,將是三維成像和顯示的終極目標(biāo)。一個(gè)視頻成像系統(tǒng)包括若干功能性部分,包括獲取、壓縮、傳輸和顯示等。其中,獲取是非常重要的一步。與傳統(tǒng)光全息術(shù)中采用光干涉方法相比,面向數(shù)字全息的計(jì)算產(chǎn)生全息圖的方法顯然具備對(duì)環(huán)境要求低、靈活性高、可以對(duì)物光波的數(shù)學(xué)描述進(jìn)行直接編碼等優(yōu)點(diǎn)。但是,三維衍射場(chǎng)的計(jì)算涉及信號(hào)處理和光學(xué)理論等基礎(chǔ)性問(wèn)題,仍然面臨諸多挑戰(zhàn),探尋降低三維衍射場(chǎng)計(jì)算復(fù)雜度的方法以及探討相應(yīng)的離散化準(zhǔn)則仍是目前的研究熱點(diǎn)。計(jì)算全息涵蓋極其豐富的信號(hào)處理問(wèn)題,例如,Fresnel核既不是帶限也不是空間有限的,但它仍然能從它們有限的采樣中恢復(fù)完整的Fresnel衍射場(chǎng)。根據(jù)Wigner分布分析,信號(hào)的相干編碼比非相干編碼情況下包含更多重構(gòu)所需的主要信息。因此,一方面為了產(chǎn)生生動(dòng)真實(shí)的三維圖像,應(yīng)該計(jì)算標(biāo)量衍射形式二項(xiàng)級(jí)數(shù)展開的Fresnel(而不是遠(yuǎn)場(chǎng)Fraunhofer)全息圖,導(dǎo)致產(chǎn)生的高空間帶寬積和二項(xiàng)級(jí)數(shù)的復(fù)波衍射場(chǎng)給計(jì)算全息造成巨大的挑戰(zhàn),另一方面相干的Fresnel衍射場(chǎng)具有一些性質(zhì)可以用作加速計(jì)算方法的基礎(chǔ)。計(jì)算三維衍射場(chǎng)的方法有很多,本文以點(diǎn)云方法為基礎(chǔ),對(duì)Fresnel衍射場(chǎng)的加速計(jì)算方法進(jìn)行進(jìn)一步探究。首先,通過(guò)探究衍射場(chǎng)的采樣問(wèn)題并結(jié)合菲涅耳衍射傳播在傳播方向的可逆性給出一種間接計(jì)算方法;其次,通過(guò)對(duì)查找表方法的研究并結(jié)合Gabor波帶片或Gabor透鏡的條紋圖案具有的空間對(duì)稱性,對(duì)原有查找表方法進(jìn)行改進(jìn)進(jìn)而提高計(jì)算效率。論文的主要研究?jī)?nèi)容與創(chuàng)新情況如下:(1)根據(jù)點(diǎn)云算法的采樣標(biāo)準(zhǔn)并結(jié)合菲涅爾傳播的可逆性給出雙步計(jì)算方法,使用該方法可以獨(dú)立設(shè)定源場(chǎng)景與全息面的采樣間距。在實(shí)際計(jì)算過(guò)程中根據(jù)需要對(duì)全息面與源場(chǎng)景設(shè)定不同的采樣間距,從而在保證人眼觀察效果的前提下,有效增大源場(chǎng)景采樣間距,減少點(diǎn)云數(shù)量,提高計(jì)算效率。(2)在新型查找表方法的基礎(chǔ)上進(jìn)行改進(jìn),提出一種計(jì)算主要條紋圖案的新方法,新型查找表方法計(jì)算主要條紋圖案的過(guò)程中,一般設(shè)定為同軸全息計(jì)算,且樣本點(diǎn)與全息面的中心位置都在z軸,通過(guò)與全息圖的對(duì)稱性結(jié)合,則每次計(jì)算時(shí)只需計(jì)算一個(gè)對(duì)稱區(qū)域的全息圖,其它位置可以根據(jù)對(duì)稱性直接獲取。此方法可大大減少主要條紋圖案計(jì)算過(guò)程中的重復(fù)計(jì)算,從而進(jìn)一步提高效率。
[Abstract]:Holographic displays can provide three-dimensional images that are almost identical to the real world, fully transmitting all the depth stimuli of human perception of three-dimensional objects. It will be the ultimate goal of 3D imaging and display. A video imaging system includes several functional components, including acquisition, compression, transmission and display. Acquisition is a very important step. Compared with the traditional optical interferometry in optical holography, the method of generating holograms based on digital holography obviously has the advantages of low environmental requirements and high flexibility. The mathematical description of object light wave can be directly coded. However, the calculation of three-dimensional diffraction field involves some fundamental problems, such as signal processing and optical theory, which still face many challenges. Exploring methods to reduce the computational complexity of three-dimensional diffraction field and discussing the corresponding discretization criteria are still the hot topics. CGH covers a wealth of signal processing problems, such as the Fresnel kernel is neither a band limit nor a limited space. But it can still recover the complete Fresnel diffraction field from their limited sampling. According to the Wigner distribution analysis, the coherent coding of the signal contains more main information needed for reconstruction than in the case of non-coherent coding. On the one hand, in order to produce vivid and real 3D images, we should calculate the Fresnel holograms (not far field Fraunhofer) holograms in the form of scalar diffraction binomial series. The resulting high spatial bandwidth product and complex wave diffraction field of binomial series pose a great challenge to CGH. On the other hand, the coherent Fresnel diffraction field has some properties which can be used as the basis of the accelerated calculation method. There are many methods to calculate the three-dimensional diffraction field, which is based on the point cloud method. The accelerated calculation method of Fresnel diffraction field is further explored. Firstly, an indirect calculation method is proposed by exploring the sampling problem of diffraction field and combining the reversibility of Fresnel diffraction propagation in the propagation direction. By studying the method of lookup table and combining the spatial symmetry of the stripe pattern of Gabor band plate or Gabor lens, The main contents and innovations of this paper are as follows: 1) according to the sampling standard of point cloud algorithm and the reversibility of Fresnel propagation, a two-step calculation method is presented. By using this method, the sampling distance between source scene and holographic plane can be set independently. In the actual calculation process, different sampling spacing between holographic surface and source scene can be set according to the need, so as to ensure the effect of human eye observation. Effectively increasing the sampling distance of source scenes, reducing the number of point clouds and improving the calculation efficiency. (2) based on the new lookup table method, a new method for calculating the main stripe patterns is proposed. In the process of calculating the main stripe patterns by the new lookup table method, the holographic calculation is generally set as coaxial holography, and the center position of the sample point and the holographic plane are both in the z axis, which combines with the symmetry of the hologram. Then only a hologram of a symmetric region is calculated for each calculation, and the other positions can be obtained directly according to symmetry. This method can greatly reduce the repeated calculation in the calculation of the main stripe patterns, thus further improving the efficiency.
【學(xué)位授予單位】：安徽大學(xué)
【學(xué)位級(jí)別】：碩士
【學(xué)位授予年份】：2017
【分類號(hào)】：O436.1;TN27

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本文編號(hào)：1539544