Stimulated Raman scattering microscopy with phase-controlled light focusing and aberration correction for rapid and label-free, volumetric deep tissue imaging

We report a novel stimulated Raman scattering(SRS)microscopy technique featuring phase-controlled light focusing and aberration corrections for rapid,deep tissue 3D chemical imaging with subcellular resolution.To accomplish phasecontrolled SRS(PC-SRS),we utilize a single spatial light modulator to electronically tune the axial positioning of both the shortened-length Bessel pump and the focused Gaussian Stokes beams,enabling z-scanning-free optical sectioning in the sample.By incorporating Zernike polynomials into the phase patterns,we simultaneously correct the system aberrations at two separate wavelengths(~240 nm difference),achieving a~3-fold enhancement in signal-to-noise ratio over the uncorrected imaging system.PC-SRS provides>2-fold improvement in imaging depth in various samples(e.g.,polystyrene bead phantoms,porcine brain tissue)as well as achieves SRS 3D imaging speed of~13 Hz per volume for real-time monitoring of Brownian motion of polymer beads in water,superior to conventional point-scanning SRS 3D imaging.We further utilize PC-SRS to observe the metabolic activities of the entire tumor liver in living zebrafish in cellsilent region,unraveling the upregulated metabolism in liver tumor compared to normal liver.This work shows that PCSRS provides unprecedented insights into morpho-chemistry,metabolic and dynamic functioning of live cells and tissue in real-time at the subcellular level.

Phase aberration correction in ultrasonic phased array non-destructive testing systems

Phase aberration correction for medical ultrasound systems has attracted a great deal of attention. Since phased array techniques are now widely employed for industrial non-destructive testing （NDT） applications in various fields, the problem of phase aberrations in the process of NDT testing is considered. The technique of cross-covariance for phase aberration correction is presented. The performance of the technique for phase aberration correction is tested by means of echo signals obtained in practical non-destructive testing experiment. The results show that the technique has the better accuracy of phase correction.

Conformal optical design with combination of static and dynamic aberration corrections

Conformal domes that are shaped to meet aerodynamic requirements can increase range and speed for the host platform. Because these domes typically deviate greatly from spherical surface descriptions, a variety of aberrations are induced which vary with the field-of-regard （FOR） angle. A system for correcting optical aberrations created by a conformal dome has an outer surface and an inner surface. Optimizing the inner surface is regard as static aberration correction. A deformable mirror is placed at the position of the secondary mirror in the two-mirror all reflective imaging system, which is the dynamic aberration correction. An ellipsoidal MgF2 conformal dome with a fineness ratio of 1.0 is designed as an example. The FOR angle is 0°-30°, and the design wavelength is 4μm. After the optimization at 7 zoom positions by using the design tools Code V, the root-mean-square （RMS） spot size is reduced to approximately 0.99 to 1.48 times the diffraction limit. The design results show that the performances of the conformal optical systems can be greatly improved by the combination of the static correction and the dynamic correction.

Derivative Form of Off-axis Aberration Correction Surface and Its Application in Solar Energy Concentration

By using the derivative method, we obtained the same result with that of the previous work of Chen et al. in 2006. Different from the integral form, the derivative form of the surface expression published in this paper is derived from differential equation and based on the theory of non-imaging focusing heliostat proposed by Chen et al. in 2001. The comparison of the derivative form of fixed aberration correction surface has been made with that of integral form surface as well as that of spherical surface in concentrating the solar ray.

Aberration-corrected scanning transmission electron microscopy for complex transition metal oxides

Lattice,charge,orbital,and spin are the four fundamental degrees of freedom in condensed matter,of which the interactive coupling derives tremendous novel physical phenomena,such as high-temperature superconductivity（high-T_c SC） and colossal magnetoresistance（CMR） in strongly correlated electronic system.Direct experimental observation of these freedoms is essential to understanding the structure-property relationship and the physics behind it,and also indispensable for designing new materials and devices.Scanning transmission electron microscopy（STEM） integrating multiple techniques of structure imaging and spectrum analysis,is a comprehensive platform for providing structural,chemical and electronic information of materials with a high spatial resolution.Benefiting from the development of aberration correctors,STEM has taken a big breakthrough towards sub-angstrom resolution in last decade and always steps forward to improve the capability of material characterization;many improvements have been achieved in recent years,thereby giving an indepth insight into material research.Here,we present a brief review of the recent advances of STEM by some representative examples of perovskite transition metal oxides;atomic-scale mapping of ferroelectric polarization,octahedral distortions and rotations,valence state,coordination and spin ordering are presented.We expect that this brief introduction about the current capability of STEM could facilitate the understanding of the relationship between functional properties and these fundamental degrees of freedom in complex oxides.

Two-photon polymerization of femtosecond high-order Bessel beams with aberration correction

In the femtosecond two-photon polymerization(2PP)experimental system,optical aberrations degrade the fabrication quality.To solve this issue,a multichannel interferometric wavefront sensing technique is adopted in the adaptive laser processing system with a single phase-only spatial light modulator.2PP fabrications using corrected high-order Bessel beams with the above solution have been conducted,and high-quality microstructure arrays of microtubes with 20μm diameter have been rapidly manufactured.The effectiveness of the proposed scheme is demonstrated by comparing the beam intensity distributions and 2PP results before and after aberration corrections.

Star Point Energy Center Correction of Star Simulator Based on Polar Coordinates

In this paper,various aberrations have been analyzed.Not only the effects of aberration on geometrical center position are taken into account,but also the deviation of displayed star position energy center caused by aberration is analyzed.These two aspects have been taken into comprehensive evaluation and star position correction.The correction method based on polar coordinates is proposed,and cumbersome partition correction and calculated quantity based on two-dimensional coordinates can be simplified.The experimental results show that the correction processing based on polar coordinates is simpler and easier compared with any other correction methods.In addition,the correction results are significantly more accurate.

光子多普勒测速仪多目标点探头光学设计

为了提升光子多普勒测速仪(Photon Doppler Velocimetry, PDV)对目标进行多点数的区域覆盖式或阵列式速度测量时的测量点数量,使用Zemax软件设计了像面直径10 mm的双远心光学系统,实现同时对平面靶5.6 mm范围内进行多点测速。该镜头由4片单透镜和4片双胶合透镜组成,工作波长为1 550 nm,工作物距为300 mm,系统总长250 mm,有效焦距500 mm,远心度小于0.01°,均方根半径在聚焦位置处最小为0.055μm,最大为0.920μm。均方根半径及全部弥散斑半径均在艾里斑范围内,调制传递函数曲线与衍射极限重合,线条平整,系统达到衍射极限。同时畸变小于0.025%,像差校正满足设计要求。

基于谱分析的红外成像模糊去除算法研究

针对红外成像中出现的像差和运动模糊问题,提出了一种基于谱分析的红外成像模糊去除算法。该方法通过对模糊问题的分析,利用红外图像频谱信息构建了模糊函数估计方法,通过数据拟合项和正则项的优化,实现红外图像的模糊去除。实验在运动模糊图像数据集和静态像差图像上进行测试,结果表明:在数据集模糊去除实验上,相比之前的方法,本文方法峰值信噪比(PSNR,peak signal-to-noise ratio)提升了2.01 dB,结果相似性(SSIM,structural similarity index)提升了0.06;静态像差图像在实验室条件下通过短波红外探测器采集,算法在主观上有较明显的复原效果,且针对高通量光学系统成像复原效果更为显著。

数字全息显微中相位像差校正技术综述

数字全息显微技术是数字全息技术与显微技术的结合,兼备两种技术的优点,为微纳领域的定量三维测量提供了一种无损、无标记、准确和近实时的测量手段。然而,由于元件缺陷和失调以及环境扰动等原因,会在数字全息显微测量结果中额外引入相位像差。为了获得准确的定量相位测量结果,必须对像差成因和主要成分进行分析,然后补偿和校正像差。这篇综述介绍了数字全息显微成像测量中主要的像差来源和影响,基于实现的方式对现有的像差校正方法进行了综述,并展望了未来像差校正领域的发展方向,为从事数字全息检测研究的研究者提供参考。

基于掩模光刻的液晶波前校正器设计与制备

液晶波前校正器通常基于液晶显示器的工艺制备而成,因此其研制成本高、定制难度大。本文基于掩模光刻法制备液晶波前校正器,以实现液晶波前校正器的专用化、低成本研制。基于掩模光刻技术设计并制备了91像素的无源液晶驱动电极,并封装成液晶光学校正单元。设计并制备了驱动连接电路板,实现了液晶光学驱动单元和驱动电路板的匹配对接。对液晶波前校正器响应特性进行检测。结果显示,其相位调制量为5.5个波长,响应时间为224 ms。利用Zygo干涉仪进行球面波的产生和静态倾斜像差的校正。结果显示,其可以产生正负离焦波前,且对水平倾斜像差校正后,Zernike多项式中第一项的值从1.18降至0.16,校正幅度达86%,实现了像差的有效校正。本文的研究工作可为液晶波前校正器的研制提供新思路,进而拓宽其应用领域和场景。

一种动态双模态线阵相机的联合标定方法

在实际工业应用中,线阵相机在被测物体运动速度快、拍摄视场范围广以及精度要求高的场景下比面阵相机更具优势,并且将二维图像数据与三维点云数据相结合能使信息量更丰富,能更好地还原真实场景。为提高在工业应用场景下的双模态数据的结合精度,提出一种动态双模态线阵相机的联合标定方法,该方法能实现简便快捷的2D线扫相机与3D线扫相机之间的联合标定。实验结果表明,该算法能以较小计算量实现高精度双模态双线扫相机的联合标定。

计算增强光学相干层析成像技术研究进展

光学相干层析成像(Optical coherence tomography,OCT)作为一种重要的无损断层三维成像技术,应用场景广泛。不断发展的场景需求对OCT技术的性能提出了新的要求,包括分辨率提升、焦深解耦、像差校正及分辨率各向异性改善等。在过去的十几年内,一系列基于计算成像的方法被证明能有效实现上述性能提升。本文围绕上述OCT成像4个性能提升需求,总结综述了代表性的计算成像方法。分析对比了相应计算成像方法之间的优劣,并对未来发展趋势进行展望,旨在为计算成像方法在OCT领域的进一步研究与应用提供参考。

深度学习颅骨重建和平面波经颅超声成像方法

为解决颅骨声阻抗失配导致平面波经颅超声成像质量下降的问题,提出一种基于深度学习的颅骨重建技术,结合快速行进法可实现平面波经颅成像的相位畸变校正。根据人类颅骨CT图像设置颅骨形状进行数值仿真,颅骨重建的时间开销为0.97 s,基于重建结果计算平面波的走时平均相对误差约为0.25%,单点目标散射波走时平均相对误差约为0.76%。经颅仿体实验中,强回声点目标图像经过校正之后,平均位置偏移从1.42 mm减少为0.28 mm,半峰全宽从1.82 mm减少为0.99 mm;圆形目标图像经过校正后对比度噪声比从7.5 dB提升为9.8 dB,偏心率从0.31降低为0.24。以上结果表明,该方法能够准确计算经颅超声的走时并且显著改善成像的质量,可用于经颅脑超声成像的相位畸变校正。

应用于高能激光器的XY离焦像差校正方法

针对高能激光器出光过程中出现的大量离焦和0°像散低阶像差现象,提出了基于哈特曼波前传感器和二维整形光路的XY离焦像差校正方法。首先,通过对Zernike多项式的离焦项和0°像散项进行线性组合得到XY离焦像差的表达式,该XY离焦像差系数的大小可直接表征X离焦和Y离焦的波前PV值。同时,通过微调高能激光器中二维整形光路中的镜子间距,可实现激光器输出光束XY离焦波面的补偿。因此,首先利用哈特曼波前传感器提取出光束的XY离焦像差系数大小,而后再根据XY离焦像差系数的大小实时闭环微调二维整形光路中的镜子间距,从而实现XY离焦像差的校正,改善输出光束的光束质量。实验结果表明,该方法可有效地将高能激光器输出光束XY离焦量的PV值由5.2μm和1.1μm校正到0.5μm以下,相应的光束质量β因子由3.1降到1.8,光束质量得到明显改善。

共光路红外双波段小型化光学镜头分析与设计

针对中长波共光路小型化光学系统设计需求,建立了基于高斯光学与初级像差理论且尺寸受限下的二次成像结构光学指标分配模型。主镜因其边缘光线高度高和承担的光焦度小,其球差、色差和二级光谱是该系统像差的主要来源,为矫正二级光谱,可使用“-、+、-”结构形式的高、中、低相对色散材料的透镜组合作为主镜结构,此时主镜的残余像差较小,采用场镜降低中继镜组光线高度以及非球面矫正球差等方法平衡主镜残余像差。最后开展实例设计,对提出的小型化设计思想进行验证,设计了中波波长3.7~4.8μm、长波波长7.7~9.5μm的共光路双波红外小型光学系统,总长不大于135 mm,结构小巧紧凑,光学传函接近衍射极限,工作温度范围-40~60℃,且对温度不敏感。实现了基于二次成像结构光学指标分配模型的中长波共光路小型化光学系统分析及设计,满足中长波共光路小型化光学系统需求。

高分辨率罗兰圆光学系统的色差校正方法研究

罗兰圆光学系统优点众多,但系统中因平凸透镜的使用,导致各特征波长色散后的成像点在罗兰圆附近产生了一定量的偏移量,使得各波长成像点依次排列在一条曲面上。由于目前新型采集器件线阵CMOS或CCD的使用,而这类传感器的感光面是一个平面,因此导致结果产生较严重的色差。提出了一种使用加权最小二乘法拟合像面的色差校正方法,并计算出系统像面的中心偏移距和偏移倾斜角这两个校正参数,将其引入原本罗兰圆光学系统进行色差校正,从而确定线阵光电传感器像面的最佳位置,实现高分辨率。此外在真空紫外光谱中C、P和S等元素非常重要,可使用本文提出的基于加权最小二乘法的色差校正方法,通过增加这类元素权值占比,实现最优分辨率。最后通过Zemax软件进行光学仿真,完成了罗兰圆光学系统的仿真以及优化。并给出170~410 nm波段点列图的成像宽度仿真以及各元素特征波长在CMOS传感器上所采集到的光谱图,推算出其实际应用中的分辨率,其照度光谱图显示其分辨率均可保持在0.02 nm,接近系统理论最佳分辨率。研究结果表明基于加权最小二乘法拟合像面的方法,可实现罗兰圆光学系统的色差校正,实现高分辨率。

基于多角度多光谱相机的相对辐射校正方法分析

多角度多光谱相机(Directional Multi-Spectral Camera,DMC)由5台相机组成,每台相机单独成像,这种成像方式导致其立体成像过程中多相机间辐射响应很难保持一致性。为实现各个视角相机及每片CCD的辐射响应一致,文章提出了多相机全局色差标定法,并与直方图在轨统计法和偏航定标法对DMC影像的辐射校正效果进行了对比。其中几种方法的相机间影像的辐射校正效果比较显示,多相机全局色差标定法校正的5个相机的影像颜色更接近,且均匀地物的相对辐射校正精度更高;CCD片间影像的校正效果比较显示,直方图统计法和多相机全局色差标定法校正的CCD片间影像都呈现颜色均衡,基本无色差,且相对辐射校正精度在3%以内。综上,说明多相机全局色差标定法更适用于校正DMC的辐射一致性问题。

A coherence-based phase aberration correction method in medical ultrasound

A coherence-based correction method was proposed in order to improve the lateral resolution and enhance the contrast of medical ultrasound imaging in the presence of phase aberration. The averaged coherence factor was proposed at first and used as a metric to evaluate phase aberration correction. By maximizing the averaged coherence factor, the time delay parameter of each channel was adjusted. A new set of coherence factors was calculated and the corrected data was optimized to form the final B-mode image. The simulations on point targets and a cyst phantom showed that the proposed method outperformed the nearest neighboring cross correlation method and conventional coherence-weighting method, and the lateral resolution and contrast ratio was improved by approximately 0.24mm and 18dB respectively. The proposed method combined the advantages of phase error correction and coherence-weighting, which could improve imaging qualities effectively in medical ultrasound.

Optical study on the vision correction and supernormal vision based on the wave-front aberrations of human eye

In this paper we present the recent research results in the field of vision correction and supernormal vision according to the actual measurements of the wave-front aberrations and the corneal surface topography,the clinical detection of the visual function and the laser corneal refractive surgery,and the optimization of the optical system. These include the features of the aberrations of human eye with different pupil sizes,different fields of view and temporal accommodation,the influence of the polychromatic illumination of the visible wavelength on the supernormal vision,and the effect of the existing laser corneal refractive surgery on the wave-front ab-errations of the eye. It is shown that the wave-front aberration of human eye is of temporal variation and of synthesis with multi impact factors. To achieve super-normal vision,an optimum engineering data for the customized laser corneal sur-gery should be firstly acquired,which may involve the dynamic free-form optical surface. Although the myopia can be corrected by the laser in situ keratomileusis(LASIK) in a certain degree,it brings about negative effects under scotopic condi-tions.