应用共焦显微镜原理测量倾斜工程表面

用基尔霍夫衍射公式分析反射式共焦光路 ,得到了被测件有一定倾斜角度表面的共焦轴向响应理论模型。由菲涅耳衍射近似公式得到的共焦轴向响应特性只是它的理论模型的一个特例。同时 ,对接收端采用差动连接的共焦测量的聚焦瞄准信号进行了分析 ,得到了表面倾斜角对聚焦瞄准信号影响的关系。应用共焦实验系统及差动测量系统对具有不同倾角的块规斜面的轴向响应信号进行了测量。理论模型的数值分析与实验结果相吻合。用差动共焦光学系统作为瞄准传感器、用电容传感器进行位移监测 ,对倾角为 10°的角规的斜面进行测量 ,得到分辨率小于 2 0nm的表面形貌图。     

光栅尺测长式激光差动共焦曲率半径测量系统

为了增强高精度曲率半径测量仪器的抗环境干扰能力,满足现场使用需求,研制了一套基于光栅尺测长的激光差动共焦曲率半径测量系统。该系统利用差动共焦轴向光强响应曲线的过零点对应系统物镜聚焦焦点这一特性,对被测样品的猫眼位置及共焦位置进行精确瞄准定位,并借助光栅尺测长得到透镜猫眼位置与共焦位置之间的距离,实现曲率半径的测量。实验表明,该系统相对测量精度优于510-6,满足高精度曲率半径测量的精度需求。     

共焦元件测量系统数据处理中的高斯滤波算法

为进一步提高共焦元件参数测量系统的定焦精度,提出了运用高斯滤波算法对由共焦系统采集的光斑图像和共焦轴向强度响应信号进行滤波处理,以降低系统光学噪声对测量光斑图像的影响,削弱外界环境扰动等因素对共焦轴向强度响应信号的干扰。经理论分析和实验验证,在对测量光斑图像和共焦轴向强度响应信号进行高斯滤波算法处理后,可有效地抑制图像噪声,降低高次谐波干扰,进而提高系统的定焦精度。     

基于虚拟双差动共焦的快速表面轮廓测量方法

针对传统共焦显微技术定焦过程中扫描速度和扫描精度无法兼顾的问题,提出了一种基于虚拟双差动共焦的快速表面轮廓测量方法。其将传统共焦响应曲线向前平移和向后平移指定量得到虚拟前焦和虚拟后焦信号;然后将虚拟前、后焦信号与原始共焦信号分别相减,并将相减结果做相加处理得到虚拟双差动曲线。虚拟双差动曲线具有大线性范围、高定焦灵敏度的特点,在大扫描间距情况下获取表面轮廓时,可实现样品表面轮廓的快速、高精度的定焦。仿真分析及实验结果表明,与传统差动共焦显微成像方法相比,虚拟双差动共焦表面轮廓测量方法可在保持高定焦精度的前提下,将几何形貌成像速度提高2倍以上。     

用于自由曲面表面测量的激光差动共焦传感器

针对自由曲面测量问题,构建了一套高精度大量程激光差动共焦传感器。该传感器基于激光差动共焦原理,利用归一化单点定焦模型减小被测表面倾斜角度、反射率的影响,结合非等距分数阶累加预测算法预判焦点位置,实现快速跟踪定焦。将气浮导轨与PZT结合拓展轴向扫描范围。实验表明,该传感器轴向分辨力优于3nm,可测量表面倾斜角度达22°,轴向扫描范围达50mm,差动曲线的过零点标准偏差为5.7nm,有良好的重复性。该传感器为自由曲面的面型轮廓测量提供了一种新的方法。     

共聚焦成像系统中探测器对分辨率的影响

基于点扩展函数,推导出共焦系统的成像公式,模拟了探测器尺寸对分辨率的影响,并提出最佳针孔半径.为验证理论分析,设计并建立了一套共焦系统,测量了不同针孔时的轴向响应,并得到了鉴别率板的共焦和离焦像.     

差动共焦显微成像高稳定三维扫描技术与系统

激光差动共焦显微镜具备高空间分辨率特点,但因其逐点扫描成像方式,扫描时间长,易受三维扫描系统不稳定和环境干扰等影响,产生系统漂移,影响仪器的空间分辨率。利用楔块机构高稳定特点,结合刹车机构的自由抱闸特性,设计了一种新型的轴向升降机构,由此构建了结构更具稳定特性的电动三维扫描系统。稳定性实验验证在搭建的激光差动共焦显微镜上进行,经过监测系统在90min内的轴向位置,轴向漂移小于50nm,与原三维扫描系统漂移140nm对比,漂移速度明显减慢,稳定性有显著提升,进而明显改善了差动共焦显微成像效果。     

具有抗漂移特性的激光共焦拉曼光谱成像技术与系统

共焦拉曼技术结合了共焦显微技术和拉曼光谱技术,具有高分辨率、高灵敏度、可层析成像的优势,广泛应用于物理、材料科学、生物医学、文物鉴定以及刑侦等领域。由于拉曼光谱成像需要较长时间,测量中系统易受环境等因素影响产生漂移,造成离焦,而现有商用共焦拉曼光谱仪并无定焦能力,容易影响测量结果。针对此问题,研制了一种具有抗漂移能力的激光共焦拉曼光谱探测系统。在不改变共焦拉曼探测基本原理的基础上,利用拉曼轴向响应曲线最大值对应显微物镜焦面这一特性,对每个探测点进行轴向扫描,采集一定数量的轴向信号,通过曲线拟合寻找光谱强度极值位置,保证扫描过程中样品始终处于系统的焦点位置处,抑制离焦影响,改善拉曼光谱成像效果。以单层石墨烯样品进行单点测试,证明仪器在5 μm离焦范围内可以实现实时定焦,定焦后采集到的拉曼光谱强度几乎不变,具有良好的抗漂移能力;对硅台阶样品进行成像测试,结果表明成像过程中,信号强度未发生明显变化,且横向分辨率有一定改善,效果明显优于普通共焦拉曼光谱探测系统。     

差动共焦式纳米级光聚焦探测系统的研究

为解决纳米级大范围的非接触测量问题 ,提出了基于差动式共焦显微技术的光聚焦探测系统。介绍了系统的工作原理和结构装置 ,对系统中的关键技术进行了优化设计 ,通过对共焦光路的差动设计 ,可以有效地抑制光源的噪声和漂移对测量结果的影响。初步实验结果表明 ,该系统的轴向分辨率可达 2 nm     

五维自动调整差动共焦间隙测量方法

为精确、快速测量镜组内各透镜间的轴向间隙,提出一种基于五维自动调整的差动共焦间隙测量方法。该方法根据CCD探测器实时获取的光斑信号检测被测镜组光轴的平移偏差与倾斜偏差,依据偏差信息、通过五维自动调整技术实现镜组高精度调整,再利用差动共焦高精度层析定焦和镜组内部光线追迹实现轴向间隙高精度测量。分析和实验表明,本方法可以有效提高姿态调整效率3.4倍,透镜间隙重复测量精度可达到0.53μm。该方法为实现镜组间隙的快速高精度测量提供了有效途径,同时还为透镜的中心厚度、焦距、半径等多种参数快速高精度测量提供了有效方法。     

Experimental research on a novel fiber-optic cantilever-type inclinometer

Experimental setup for tilt measurement and a novel signal detection method for demodulation of fiber Bragg grating (FBG) wavelength shift are proposed. Being attached, respectively, on the upper and lower surface of only one single pendulum-type cantilever element, only a couple of matched FBGs are used for both tilt angle sensing and wavelength shift signal demodulating. So the received light power will change due to the split of the two reflected spectra of FBGs, which corresponds to the tilt angle. In addition, the cross-sensitivity effect of FBG-based sensors will be solved automatically due to a differential signal process method. Experimental results indicate the measurement accuracy is about ± 0.03°, and measurement resolution is estimated to be about 0.002°.     

共焦扫描光学显微镜的高分辨率

讨论了共焦扫描光学显微镜的高分辨率性质,指出共焦扫描显微镜由于采用点探测器,因而视场大大减小,信噪比大大提高,同时每幅图像逐点扫描形成,在光学系统信息能力不变的前提下,系统的空间域通带宽度增加和时域通带宽度减小。因而可成高分辨率的像,特别是其独特的深度分辨率特性使得可以实现光学断层扫描成像。给出了所研制的共焦扫描荧光显微镜所获得光学断层扫描图像     

Strain and tilt measurement using multi-point diffraction strain sensor

A multi-point diffraction strain sensor (MDSS) was developed earlier by us for strain measurement with variable sensitivity and measurement range using a microlens array. The technique is now extended to measure both tilt and non-uniform strain with a sensitivity of 0.41 mε/pixel and 4.7 mrad/pixel. The validation was made through comparison of the strain measured using MDSS with that by a micro-Moiré interferometer incorporated with Gabor filtering method, while the tilt is compared with derivatives of the surface profile measured by a confocal microscope.     

Interfacial shape and contact-angle measurement of transparent samples with confocal interference microscopy

A model has been developed that predicts the effective optical path through a thick, refractive specimen on a reflective substrate, as measured with a scanning confocal interference microscope equipped with a high-numerical-aperture objective. Assuming that the effective pinhole of the confocal microscope has an infinitesimal diameter, only one ray in the illumination bundle (the magic ray) contributes to the differential optical path length (OPL). A pinhole with finite diameter, however, allows rays within a small angular cone centered on the magic ray to contribute to the OPL. The model was incorporated into an iterative algorithm that allows the measured phase to be corrected for refractive errors by use of an a priori estimate of the sample profile. The algorithm was validated with a reflected-light microscope equipped with a phase-shifting laser-feedback interferometer to measure the interface shape and the 68 degrees contact angle of a silicone-oil drop on a coated silicon wafer.     

A shaped annular beam tri-heterodyne confocal microscope with good anti-environmental interference capability

A shaped annular beam tri-heterodyne confocal microscope has been proposed to improve the anti-environmental interference capability and the resolution of a confocal microscope. It simultaneously detects far-, on-, and near-focus signals with given phase differences by dividing the measured light path of the confocal microscope into three sub-paths (signals). Pair-wise real-time heterodyne subtraction of the three signals is used to improve the anti-environmental interference capability, axial resolution, and linearity; and a shaped annular beam super-resolution technique is used to improve lateral resolution. Theoretical analyses and preliminary experiments indicate that an axial resolution of about 1 nm can be achieved with a shaped annular beam tri-heterodyne confocal microscope and its lateral resolution can be better than 0.2 $\mu $m for $\lambda =632.8$~nm, the numerical aperture of the lens of the microscope is NA $=0.85$, and the normalized radius $\varepsilon =0.5$.     

激光共焦球面元件姿态自动调整系统

为解决激光差动共焦元件参数测量系统中人工调整元件姿态效率低、重复性差的问题，研制了激光共焦球面元件姿态自动调整系统。基于共焦原理，建立了元件失调量与电动四维调整机构调整量关系的数学模型，并根据CCD探测器实时获取的光斑位置信号分析出被测件的姿态信息，结合闭环反馈控制算法实现姿态自动调整。利用电动四维调整机构搭建了自动调整实验装置，实验结果表明:研制的电动调整机构平移调整分辨力达到0.5 μm，倾斜调整分辨力达到8″；调整系统能够快速、稳定地将被测件姿态失调量调至误差范围内，有效提高调整重复性及效率，对激光差动共焦测量系统实现全自动球面元件参数检测格外重要。     

共焦扫描荧光显微镜的信噪比与信息量

在研制用于对厚的生物样品进行光学断层成像的共焦扫描荧光显微镜时，由于成像信号十分微弱及存在很强的多次散射作用，因此杂散光的抑制非常重要，而信噪比、信号背景比就成为决定能否获得高对比度、高分率图像的关键。运用光学信息量的概念，在已有的光学成像系统信息量计算、共焦扫描荧光显微镜信噪比及传递函数计算的基础上，详细分析了共焦扫描荧光显微镜信息量与信噪比等之间的定量关系。该关系表明，为了充分利用共焦扫描荧光显微镜的成像性能，必须选择适当的探测小孔。所得的结果对于共焦扫描荧光显微成像系统的研制有重要的实用价值。     

Deconvolution of local surface response from topography in nanometer profilometry with a dual-scan method

In profilometric measurements, by scanning the sample twice with a fixed vertical offset, one can separate the signal that comes from surface heterogeneity from the topographic signal. Using differential confocal microscopy, a newly developed open-loop nanometer profilometric technique, we demonstrated this dual-scan method on composite samples and obtained 10-nm depth resolution. This technique can also be applied to other profilometric techniques such as atomic force microscopy and scanning tunneling microscopy.