频域OCT的背向散射率补偿

针对频域OCT中背向散射光的强度随探测深度加深而急剧减弱,从而导致最后的组织成像模糊不清的现象,提出了一种对不同探测深度图像灰度补偿的方法。该方法通过补偿样品每层析面的入射光功率与背向功率散射率,来得到样品每层析面图像的真实灰度,提高了OCT图像质量。以理想的、由多层均匀介质组成的组织模型为基础,深入剖析了影响深度图像灰度的主要因素。通过建立以多层盖玻片为被测物体的频域OCT系统,得到多层盖玻片的深度图像。在对以盖玻片为被测物体的前提下,得出逐层深度图像灰度补偿的公式。并将理论补偿和实验系统的复杂情况相结合,对深度灰度图像进行入射和出射光强的补偿。实验结果证明这种补偿法是一种有效可行的补偿方法。     

Compensation for the Influence of Fluctuations in the Distance to the Object During Noncontact Probing in Spectral Domain Optical Coherence Tomography

Radiophysics and Quantum Electronics - We propose and experimentally test a numerical method for correction of the influence of fluctuations in the distance to objects during noncontact probing in...     

光学腔内两正交偏振模振幅和相位的补偿

本文开展了光学腔内两正交偏振模振幅和相位补偿的实验研究。通过采用特殊腔型和两个λ/2波片,补偿腔内反射镜对水平偏振模和垂直偏振模的反射率差异,使两个偏振模的输出振幅相等。利用一组λ/4-λ/2-λ/4波片补偿光学腔内水平偏振模和垂直偏振模的相位差,使两个模的输出重合。通过上述的振幅和相位补偿方法,可实现任意偏振光经过环形腔后偏振不变,为任意偏振比特在腔内冷原子系综中的高效率高保真度存储提供了实验基础。     

样品散射对频域光学相干层析成像光谱形状和深度分辨率的影响

研究了样品散射性质对频域光学相干层析成像干涉谱信号和深度分辨率的影响。理论分析和模拟结果表明:样品散射使干涉谱信号的强度分布发生改变且向长波方向偏移,进而降低了成像的深度分辨率;样品的散射系数越大、深度越深,偏移越严重,深度分辨率降低越多;使用相应的校正函数可以提高深度分辨率。     

Measurement of Vibration Derivative′s Amplitude and Phase by Strobe and Optical Phase Shifting Shearography

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Full Bandwidth Measurement of Supercontinuum Spectral Phase Coherence in Long Pulse Regime

Abstract

This article reports that spectral phase coherence in the supercontinuum in long pulse regime can be measured simply and effectively by using an interference technique with the help of a Mach–Zehnder interferometer. It is also demonstrated that chromatic dispersion on the fringe visibility of interference spectral patterns is overcome in the setup. The technique is applied to characterize supercontinuum spectral phase coherence in a highly non-linear optical fiber with different input conditions: unseeded, coherent seeded, and incoherent seeded picosecond pumps. The results confirm the phase coherence characteristic predicted theoretically in previous studies.     

频域光学相干层析术系统中高准确度高灵敏度补偿色散法

将色散测量方法和快速扫描延迟线技术相结合,在谱域光学相干层析系统中实现了对群延迟色散的精确补偿.在该方法中,先在样品臂中放入平面反射镜,等间隔移动参考臂中快速扫描延迟线系统中光栅的位置,同时测量系统参考臂和样品臂之间的群延迟色散差值.当该值为零时,则表明系统色散匹配.将该方法与基于点扩散函数半高宽的方法进行比较,发现基于半高宽方法的测量误差为4.43%,而该方法的测量误差为0.76%;在色散补偿过程中,随着色散匹配点的靠近,半高宽方法的灵敏度由92.105 3fs2减小到1.344 7×103 fs2,而新方法的灵敏度则保持165.789 5fs2,表明本文提出的色散补偿法具有较高的色散补偿准确度和灵敏度.实验表明,色散补偿后的系统分辨率接近理论值;在补偿系统色散的同时,还可以根据测量所得色散值的符号来判定光栅的移动方向,从而更容易地完成补偿工作.     

Elimination of Artifacts Caused by the Nonidentity of Parallel Signal-Reception Channels in Spectral Domain Optical Coherence Tomography

Radiophysics and Quantum Electronics - We study the causes of artifact appearance in the images obtained by the method of spectral domain optical coherence tomography with parallel reception of the...     

利用变迹术和相干门相结合实现光学相干层析成像术轴向超分辨

光学相十层析成像（光学相干层析成像术）的轴向分辨力由光源带宽和探测光束的聚焦条件共同决定。提高光学相干层析成像术轴向分辨力的方法主要基于带宽光源技术。提出了一种将变迹术与光学相十层析成像术相干门有机结合的方法来提高其轴向分辨力。通过适当形式的光瞳滤波器．使光学相干层析成像术系统轴向响应的主瓣宽度缩小到相干门之内,而其旁瓣则处于相干门之外．不对相干成像产生有效贡献。这样．就能在光源带宽不变的条件下,有效提高光学相十层析成像术的轴向分辨力,避免了采用宽带光源所带来的费用昂贵和系统复杂等缺陷。     

Process Algorithms for Resolution Improvement and Contrast Enhancement in Optical Coherence Tomography

We proposed two process algorithms for resolution improvement and contrast enhancement in the images of optical coherence tomography (OCT). An OCT system with a non-Gaussian light source spectrum or dispersion mismatch usually results in sidelobes in the interference fringe envelope that may produce artifacts and reduce image contrast. Based on the concept of deconvolution, we proposed two different process algorithms and demonstrated their effectiveness in retrieving sample structures. The effects of the process algorithms were examined by numerical simulations and real OCT scanning images. After processing with the proposed procedures, the effects of sidelobes were tremendously suppressed and the image qualities were improved.     

内窥式扫频光源光学相干层析系统的探头设计

利用自聚焦透镜和单模光纤搭建了基于光纤旋转连接器的内窥式扫频光源光学相干层析成像系统.利用Zemax模拟了内窥探头的光学性能,分析了光纤到自聚焦透镜的距离和自聚焦透镜节距对探头性能参量的影响.在综合考虑元器件成本以及成像要求后,选择无需定制,节距为0.24Pitch的自聚焦透镜,确定光纤与自聚焦透镜之间的距离为0.7mm.经实验测得该系统的横向分辨率约为19.5μm,纵向分辨率约为9μm,工作距离约为7mm,成像深度为6.2mm(空气中),与理论值接近.为了验证该系统对生物组织的成像性能,利用该系统对猪食道进行离体成像,重建后的层析图中可以明显地观察到猪肠道的表皮层和固有层.测量系统的各项成像性能参量以及对生物组织的成像性能表明该探头在内窥成像中是可行的.     

基于超高分辨率光谱分析的周期光信号相对相位测量方法

提出了一种基于超高分辨率光谱分析实现周期性光信号频域中相位分布的测量方法.在已测得待测信号高分辨率光谱的情况下,利用马赫泽德调制器载波抑制效应调制激光器产生双泵浦,激发高非线性光纤中的受激布里渊散射效应形成有源双滤波器.用泵浦激光器在测量波长范围内进行连续扫描,得到包含待测信号相位信息的拍频信号,经数据采集和处理后得到待测信号频域上的相对相位信息.实验给出了速率为5Gb/s,字长为31bit的周期性光信号在频域上的相对相位分布信息,证明了这种有源双滤波器的频率响应特性可以满足相位测试的需要.     

紫外ICCD相对光谱响应度测量技术研究

光谱响应度是探测器的重要技术参数之一,随着紫外探测技术的发展,精确测量紫外探测器的光谱响应度变得越来越重要。文章分析了紫外ICCD(UV-ICCD)相对光谱响应度的测量原理,采用了直接比较法测定待测探测器的相对光谱响应度,并基于具有优异紫外响应能力的科研级光谱仪建立了UV-ICCD光谱响应的测量装置。实验获取了UV-ICCD的相对光谱响应度曲线,从曲线中可以看出,UV-ICCD光谱响应范围为220～300 nm,峰值响应在270 nm附近,表明该器件具有日盲特性。不确定度分析结果显示,UV-ICCD相对光谱响应度测量的最大不确定度约为7.79％,满足测量要求。     

杨氏实验中飞秒光脉冲的光谱移动和光谱开关

从惠更斯-菲涅耳衍射积分公式出发,对飞秒光脉冲在杨氏实验中的光谱移动和光谱开关做了研究和数值分析.结果表明,飞秒光脉冲在杨氏实验中也会出现光谱移动和光谱开关.一般情况下,光谱开关与脉冲宽度、载波频率、遮拦比和场点位置有关.光谱开关的数目随遮拦比的减小而减小,而发生光谱开关处的相对光谱移动随载波频率和脉冲宽度的减小而增加.因光谱开关极小值Smin=0,所以光谱开关属于奇点光学现象.可通过适当改变遮拦比来实现信息编码和信息传输.     

Effect of Amplitude and Phase Distortions on the Formation of Light Fields with Rotating Intensity Distribution

The results of numerical simulation and experiments on the effect of amplitude and phase distortions on the formation of the light fields with the rotation of intensity distribution during propagation are presented. Practically significant cases of amplitude and phase distortions with regular and random inhomogeneity types are considered.     

基于幅度相位联合校正算法的8-QAM自由空间相干光通信

提出了基于幅度相位联合校正算法的8阶正交幅度调制(8-QAM)自由空间相干光通信方案。与传统的自由空间光通信方案相比,本文提出的方案不仅无需信道状态信息(CSI)就可以实现对原信号的高精度还原,同时还具有较高的光谱效率。仿真实验表明,当接收端与发射端的频偏f₀=20 MHz、激光器联合线宽Δf=10 kHz、信噪比为20 dB时,该方案在归一化大气闪烁标准差σ=0.25、归一化相位噪声方差σ■=0.07的对数正态湍流信道条件下,其误码率(BER)与未采用联合校正算法的8-QAM系统相比低4个量级。     

Storage and Retrieval of a Weak Optical Signal Improved by Spontaneously Generated Coherence in an Atomic Assemble

We investigate the reversible storage of a weak single-mode light signal in a Λ-type three-level atomic system with spontaneously generated coherence (SGC) and pumped by an incoherent field.The scheme is phase-dependent.If the phase of the controlling field is set oppositely to that of the signal field,the combination of SGC with weak pump overcomes the drawback of incompletely retrieval in the conventional scheme,leading to 100% retrieval fidelity or even to the amplification of the retrieved signal with respect to its initial one.     

Design and Simulation of Broadband Beam Splitter on a Silicon Nitride Platform for Optical Coherence Tomography

ABSTRACT

Integrated photonics enables the miniaturization of bulk optical components for biosensing applications such as optical coherence tomography (OCT) and is therefore promising for future lab-on-chip solutions. Here, we report the design and simulation of a compact low loss broadband beam splitter with arbitrary coupling ratios on silicon nitride platform for OCT systems. The reported coupler uses asymmetric waveguide-based phase control section for 10:90, 20:80, 30:70, 40:60, and 50:50 splitting ratios and is broadband over 100 nm with the central wavelength of 850 nm. The couplers are realized for transverse electric, transverse magnetic, and fully vectorial modes, and maximum excess loss for all mode types is reported to be less than 0.19 dB. The design tolerance of waveguide width and thickness of the designed coupler is further calculated and is within fabrication limit.     

光学相干层析图像层状结构的增强与定量测量

光学相干层析(OCT)成像技术对于眼底等层状组织的定量测量有赖于光学相干层析图像中层状结构的提取。为了对原始光学相干层析图像进行预处理以有效地去除图像中的噪声及散斑、增强图中的层状结构,并更好地保护图像中的层状结构,进而更准确地定量测量图像中有重要意义的层状结构的光程信息,提出在相干增强各向异性扩散(CED)算法中引入二阶导数项以控制沿相干方向的扩散强度,并将引入二阶导数项的相干增强各向异性扩散算法应用于不同样品的光学相干层析图像。结合在预处理后图像中层状结构位置的查找结果与样品的折射率信息,实现了对光学相干层析图像中有重要意义的层状结构厚度的定量测量。实验结果表明,使用引入二阶导数项的相干增强各向异性扩散算法对光学相干层析图像预处理有利于对图中重要层状结构的更准确测量。