【作者】 杨柳；

【导师】 于撼江；

【作者基本信息】 辽宁大学 ， 光学， 2015， 硕士

【摘要】 关联成像又被称作“鬼”成像,它是一种通过二阶关联计算方法来获得物体相关信息的新成像技术。目前在光源方面已经可以使用纠缠量子光、赝热光以及真热光来完成关联成像实验。近年来由于高阶关联可以显著提高成像对比度,从而成为人们研究的热点问题。第一个热光N阶(Ν?2)无透镜鬼成像实验是基于两个探测器方案并结合强度关联函数实现的。但是该方法存在一个严重的缺点,在阶数N不变采样数一定的条件下,当探测臂数量减小,成像质量降低。要想得到同样的成像质量,就必须要更长的数据处理时间,也就是要更多的采样数量。本文基于两个探测器的实验方案和改进的?阶关联函数实现了赝热光源的无透镜高阶关联成像实验。实验重点分析了探测臂数量n?1情况下的成像,发现在采样数相同的情况下,基于改进的?阶关联函数的新算法能够有效降低热光源高阶关联成像的噪声,成像质量远远好于传统方法。验证了结论对于传统算法的高阶关联成像在采样数一定的条件下,阶数越高,成像质量越差。此外,通过对高阶成像的对比度和信噪比随着采样数的变化规律的研究发现,信噪比是随着采样数的增加而增加;对比度在采样数较少时快速减小,而后逐渐保持平稳。但是,在采样数相同且足够大时,成像的对比度是随着阶数的增加而增加,而信噪比是逐渐降低的。最后,分析了阶数不变时,关联函数的最大、最小值之差与之和随采样数的变化关系,发现采样数较少时,背景噪声很大导致对比度降低,若采样的数量增大关联函数的涨落噪声就会被抑制,对比度将趋于平稳。而阶数增大时对比度达到平稳所需的采样数也会增加。更多还原

【Abstract】 Correlated imaging, which is also called "ghost" imaging, is a novel imaging technique through second-order optical intensity correlation measurement to recover the information of objects. Until now various light sources have been employed in the ghost correlated imaging experiment, including quantum optical, pseudo-thermal, and even true thermal light. Recently studies on the higher-order intensity correlation effects of thermal light show that the visibility can be significantly enhanced as the increase of the order N. The first Nth-order(N ≥ 2) correlated experiment in a lensless scheme was performed by recording only the intensities in two optical paths. However, there was a serious drawback that the quality of the correlated images is much poor of)( Nng for the case of n<N-1 compared to that of n=N-1 for the same sampling number. here)( Nng is the Nth-order correlation function for GI, and n is the number of test(object) beams. Therefore, to obtain the same good image quality, a much longer measurement time(sampling number) is required.An Nth-order correlated imaging experiment with pseudo-thermal light is performed by recording only the intensities in two optical paths in a lensless setup, based on a modified Nth-order correlation function. The experiment focuses on analysing the case of the number of test beams n=1.It is found that this new algorithm can effectively remove the noise background encountered in high-order thermal light correlated imaging, so the quality of the reconstructed images in an Nth-order lensless correlated imaging setup has been greatly enhanced compared to former high-order schemes for the same sampling number. Verified the conclusion that with the same number of samples the quality of the image is worse with higher of the order for the traditional higher-order correlated imaging. In addition, the visibility and signal-to-noise ratio for different high-order images on the sampling number has been measured and compared. It is shown that the SNR increases quickly with increasing sampling number, while the visibility initially decrease rapidly and then gradually level off. It can be also found that, as the order increase, the visibility of the high-order image is increasing while the SNR reduces, when the sampling number is large enough. Finally, it analysed the sum and the gap between the maximum and minmum of correlation function when the order is certain. And found that with a few samples a great background will lead to the decrease of the visibility. When the number of samples is increasing, the fluctuation noise of correlation function will be inhibited, then the visibility tends to be smooth. If the number of the order is increasing, the number of samples needed will increase while the visibility to achieve steady.更多还原