显微数字全息中物光波前重建方法研究和比较

根据全息理论和线性系统理论,采用离轴无透镜傅里叶变换全息记录光路,对利用菲涅耳近似法、基于瑞利—索末菲衍射积分的卷积法以及角谱理论方法数值重建全息图进行了比较研究,并做了计算机模拟验证.结果表明：菲涅耳近似法和角谱方法重建像质比较好,且菲涅耳方法重建速度快；在记录距离极小的情况下,尽管记录距离不满足通常的菲涅耳近似条件,菲涅耳近似公式仍然成立；自由空间脉冲响应的快速傅里叶变换的性质与距离有关,由卷积方法得到的再现像只在某一特定距离下比较理想；对于极小物场、大孔径显微数字全息来说,菲涅耳近似重建方法是较为有效的方法.     

可编程菲涅耳相位透镜应用于多平面全息投影

研究了基于菲涅耳相位透镜实现多平面全息投影的方法,采用硅基液晶相位调制器建立了多平面全息投影系统.首先,利用可编程菲涅耳相位透镜代替傅里叶透镜,将计算机生成的相位全息图与菲涅耳透镜的相位结合;其次,基于时分复用和空分复用原理提出了加载菲涅耳相位透镜与相位全息图到相位空间光调制器上的两种方法;最后,讨论了在多平面全息投影中每个单一平面实现旋转物体动态360°视角显示的方法.实验结果表明:在距离硅基液晶分别为500、800、1 100和1 400mm处的四个重构平面可以获得全息投影图像;通过动态地改变菲涅耳相位透镜的焦距,可以实现多平面全息投影.     

基于菲涅耳透镜色散的双波长荧光显微深度成像

提出一种非轴向扫描的细胞显微深度成像技术,在显微系统中加入菲涅耳透镜,利用菲涅耳透镜的色散将不同激发光波长聚焦到不同的轴向位置,以实现对两个或多个焦平面同时成像.基于405nm和532nm两种激发光波长,在传统的荧光显微镜的激发路径中加入对应的两个成像探测器来探测两个不同焦平面所对应像面的成像信息,搭建得到一个能够实现探测深度约为12μm的基于菲涅耳透镜的荧光显微深度成像系统,并与基于显微物镜色差无菲涅耳透镜的荧光显微深度成像系统的成像深度和轴向分辨率进行实验对比.实验结果表明:加入菲涅耳透镜能够实现系统对不同焦面的同时成像;对于同一荧光波段,保证系统横向分辨率的同时,扩大了成像景深.该系统可以实现荧光生物细胞内部不同深度处的多波段同时探测.     

数字显微全息中二次项相位误差的补偿

针对预放大式数字离轴显微全息技术中二次项相位误差,提出一种基于单幅全息再现的补偿方法.该方法是在显微物镜后焦平面处实现该相位误差的数学补偿,相位误差补偿过程具有调整参量单一化的优点.同时,利用显微物镜的后焦平面上物点特征实现了最佳再现距离的自动判断.该文以相位光栅为实验样本,对该方法进行了实验例证,实验结果验证了本文所提出二次项相位误差的补位误差的补偿方法的正确性和有效性.     

预成像数字全息测量大物体三维形貌

为了扩大数字全息三维形貌测量的视场,提出了一种预成像的方法.物体先被成像镜头成一缩小的实像,再使用离轴菲涅耳数字全息对此实像进行全息记录.采用倾斜照明光的方法使两次数字全息的再现像之间产生相位差,通过相位去噪和去包裹处理从相位差中提取物体的三维形貌数据.实验证明,预成像方法使测量视场的大小得到了至少一个数量级的提高,采用离轴菲涅耳数字全息降低了测量系统对环境稳定性的要求.     

预放大数字全息系统的成像分辨率分析

基于菲涅耳衍射理论,详细推导了预放大数字全息系统的点扩散函数表达式,并由此分析了该成像系统的分辨率.通过分别对整个系统、显微物镜以及CCD的点扩散函数幅值的计算机模拟,讨论了显微物镜与CCD分辨率之间的匹配问题.指明了现有文献中一些含糊说法.结果表明:恰当选择记录参量,使MO的成像分辨率接近于其极限分辨率,同时还要使CCD在满足抽样条件与再现像分离条件的情况下,再现像分辨率等于或略高于MO的分辨率.     

数字全息成像系统的景深和焦深分析

根据全息理论,分析了数字全息成像系统的景深和焦深.针对数字全息不同的记录光路结构,分别给出了焦深的近似表达式.结果表明：数字全息系统的景深和焦深不仅与记录波长以及记录时的数值孔径有关,还与记录时参考光波的偏置情况有关;在记录距离和CCD参量一定的条件下,离轴无透镜傅里叶变换全息对称偏置下的焦深比非对称偏置下的稍小;显微成像情况下离轴无透镜傅里叶变换全息系统的焦深大于同轴菲涅耳数字全息系统的焦深,计算机模拟表明了结果的正确性.     

菲涅耳数字全息成像系统的焦深

焦深是表征成像系统性能的重要参数.基于透镜相干成像的焦深判据,利用数值积分和计算机模拟的方法,分析和推导了菲涅耳数字全息成像系统的焦深,给出了相应的焦深表达式,并与利用理想成像四分之一波像差的判据得到的焦深进行了比较.结果表明:菲涅耳数字全息成像系统的焦深不同于透镜相干成像系统的焦深.在记录距离和CCD参数一定的条件下,离轴菲涅耳数字全息成像系统的焦深略大于同轴菲涅耳数字全息的焦深;离轴对称偏置情况下的焦深略大于非对称情况下的焦深.利用像强度判据得到的焦深,能够较好地表征数字全息成像系统的性能.     

会聚球面波曲率半径的精确测量

本文提出了一种特殊情况下的准菲涅耳衍射近似处理方法,报道了一种利用全息光栅精确测量会聚激光球面波曲率半径的新方法并分析了测量误差。这种方法具有精度高、测量方便、仪器设备简单等优点,从而为高精度全息透镜、凹面全息光栅的制造等提供了可靠的保证。     

基于菲涅耳双棱镜分波前干涉装置的全息光栅制作实验

不同于传统全息光栅制作教学实验中的分振幅干涉光路,提出了利用准平行相干光源照射菲涅耳双棱镜实现分波前干涉制作全息光栅的方法.利用菲涅耳双棱镜分波前光路分别演示了单个双棱镜制作一维全息光栅和2个棱脊正交菲涅耳双棱镜制作二维全息光栅.实验过程中可通过多种方法对干涉条纹间距和光栅常量进行估算,丰富了干涉实验内容和光栅制作实验内容.     

Study on aberration suppressing methods in digital micro-holography

This paper discusses methods to eliminate and/or suppress aberrations in digital micro-holography (DMH) with specific examples for post-magnification DMH and lens-less DMH along with a phase subtraction approach. In post-magnification DMH, the reference wave interferes with the object wave to form a hologram, which is then magnified by a microscope objective (MO) and recorded by CCD. This compensates for the quadratic phase error usually present in the pre-magnification DMH and also it is easier to isolate the useful information in pre-processing. In this paper differences between post-magnification and pre-magnification DMH are compared and analyzed with the specimen of a phase grating with period 30 lines/mm and height 0.3 μm. A lens-less DMH is also described that can eliminate the quadratic error and most of wave-front errors of the projecting light. Finally, a phase subtraction method is demonstrated which can eliminate most of the system aberrations.     

透过检测中的准直镜精度容限

在干涉检验过程中,被检元件的面形误差检测精度受到干涉仪系统结构的影响,从而降低测量结果的可靠性。为了得到较高的检测精度,必须对检测系统进行分析,建立测量误差和系统结构的关联度。根据菲涅耳衍射近似理论,就菲佐干涉仪中的准直镜和标准镜面形误差对透过检测的影响进行了研究。通过对波前相位传递情况的分析,得出波前误差和系统结构参量的相关性,去除空腔系统误差,优化结构参量,并建立准直镜误差容限表达式。经计算得出,当被检面形变误差为0.2λ时,测试误差可以达到0.02λ,而对准直镜的面形误差要求只需0.8λ。     

Wave-front curvature compensation of polarization phase-shifting digital holography

An on-axis polarization phase-shifting digital holographic microscope, based on a normal upright optical microscope, is constructed to quantitatively measure both the amplitude and phase distributions of specimen. The condenser lens and microscope objective employed in the object beam path enhance the illumination and magnification of the image, however, they induce additional phase aberration of the object wave. The physical formation of the phase aberration is theoretically analyzed, and a formula for the object wave front involving the phase aberration in the CCD plane is derived. The phase aberration can be eliminated in the reconstruction procedure by measuring a specimen-free hologram and then fitting the aberration phase with a least square ellipsoidal model to determine the parameters of the system. This phase aberration compensation procedure also reduces some of noises in the reconstructed phase of the specimen. The practicability of this method is demonstrated by a test experiment on microlenses.     

Diffraction mode selection in planar Bragg resonators of optical and microwave wavelength ranges

Using the coupled waves approach complemented by the time-domain quasi-optical approximation, we solve a 2D diffraction problem which allows to evaluate the eigenfrequencies, quality factors and spatial structures of eigenmodes in planar Bragg resonators with a finite length and width of the corrugated area. We find the values of the Fresnel parameter determined by the geometrical dimensions of the system which allows for efficient transverse mode discrimination due to the larger diffraction losses of the modes with higher transverse numbers.     

振幅型复合计算全息模式波前传感理论及验证

全息模式波前传感器是利用复合全息元件对待测波前中像差模式进行直接测量的一种新型波前传感器,其中的复合全息元件可编码设计多阶Zernike像差模式。提出一种有效方案以编码设计振幅型复合计算全息元件,该方案通过将多个编码有某阶Zernike像差模式的透过率调制扭曲光栅叠加产生振幅型计算全息元件。在小像差近似条件下推导了传感器输出信号与Zernike像差模式系数的解析关系。编码设计了振幅型复合全息图,并研究了其对单阶和多阶Zernike像差模式的探测性能。利用液晶光阀加载复合全息图进行了验证实验。所得实验结果与数值模拟结果基本一致。     

Effective Fresnel number and focal shifts for focused cylindrical spherical aberrated beams

We define the effective Fresnel number of a focused cylindrical spherical aberrated beam. Based on the effective Fresnel number, a simple analytical expression for evaluating the relative focal shift is presented. It is shown that the relative focal shift is determined by the effective Fresnel number, which is dependent on the spherical aberration and Fresnel number of the focused system. To illustrate the approach, a comparison between the results obtained by this new method and the numerical integral calculation is made. The results indicate that the relative focal shift can be simply and exactly evaluated using this new method. A special case is discussed, in which the effective Fresnel number turns out to be a pure imaginary number, and the corresponding relative focal shift is positive.     

Design and application of phase photon sieve

The imaging principle of Fresnel zone plate and photon sieve were analyzed in this paper. The design and fabrication of phase photon sieve were discussed. The feasibility of using phase photon sieve to realize nano-lithography was analyzed, a novel lithography experiment system based on phase photon sieve was presented, which not only has higher resolution and image contrast than the Fresnel zone plate lithography but also have higher diffractive efficiency than the amplitude photon sieve lithography.     

相位解码的时-空重建算法

基于相位映射的三维传感技术对几何形状和拓扑结构复杂或表面梯度很大的物体进行绝对相位测量及相位重建仍然是一个困难的问题。近年来国际上提出了一种时间维度相位重建算法可以对此提供一种解决方案。然而,该算法对结构光照明系统提出了很高的要求,当系统无法满足算法要求时,重建结果存在严重的噪声。针对这一问题,提出了一种利用分段函数构造的相位解码的时空重建算法。该算法在相位重建过程中同时考虑时间维度和空间维度相位的相对关系,使得空间频率非严格按指数增长的条纹序列可以得到正确的重建,消除了跳变边界的相位模糊问题,从而可以更加有效地解决深度表面不连续和存在相互孤立物表面拓扑结构的景物相位重建问题。实验结果证明了此算法的可行性和有效性。     

Efficiency and optical feedback of traveling-wave semiconductor laser amplifier to single-mode fiber coupling: Theory and experiment

This paper analyzes the coupling efficiency and optical feedback of the tapered fiber end with a high-index hemiellipsoidal microlens. Such a device has been used as a coupler of traveling-wave semiconductor laser amplifier (TW-SLA) to single mode fiber (SMF).

A theory of the calculation of coupling efficiency and optical feedback is presented including the effects of spherical aberration and Fresnel reflection of thick lens. In consideration of the large beam divergency of the TW-SLA chip, the finite transmission aperture is introduced.

The calculations are in agreement with experiment results and a group of optimum structure parameters of the coupler are given.