用于透明平板平行度和均匀性测量的单元件干涉仪

提出了一种基于单元件干涉的用于检测透明介质平整度和均匀性的干涉仪.该干涉仪的核心元件是一个菱形分光棱镜.激光光源的平面波光束的一半光束透过待测样品,另一半光束直接透过空气,然后分别入射到菱形分光棱镜的两垂直面并在分光面相遇、相干.通过旋转待测样品改变相干的两束光光程差,从而使干涉条纹发生移动.形成的相干光被分光板分成两束,一束进入光电探测器用于探测干涉条纹移动数的整数部分,另一束则进入电荷耦合探测器用于采集干涉条纹图来计算干涉条纹移动数的小数部分.通过计算条纹移动数反推出光程差的变化量,再结合折射率或样品厚度信息则可以计算出样品厚度或折射率的分布,从而检测出透明介质的平行度和均匀性.模拟仿真和光学实验均证明了本方法的可行性、准确性和稳定性.     

四波混频实时光学检测

分析了利用掺铁铌酸锂晶体作介质的简并四波混频及其在干涉计量术中应用的原理,描述了被测透明样品的表面各光波及其干涉形成的透射条纹及反射条纹,利用光折变晶体的介电驰豫特性,求得透射条纹和反射条纹的对比度随时间变化的公式及各参数的相互关系。对由透射条纹及反射条纹计算被测透明物体样品折射率和厚度不均匀性的方法作了数学分析,提出一种新型四波混频实时测量透明物体的光学不均匀性的方法和实验光路,对相关参数对测量过程及测量结果的影响作了探讨,得到了平板玻璃样品的干涉条纹图像,计算出实验结果。     

基于PASCO平台的透明材料折射率的测量

将迈克耳孙干涉仪和PASCO实验平台相结合,设计了一种高精度、高效率测量透明材料折射率的方法.首先分析PASCO迈克耳孙干涉仪测量材料折射率的原理,然后利用高性能PASCO传感器和计算机对干涉条纹进行图像采集和数据处理,得到待测透明材料的折射率信息.最后对材料折射率的不确定度进行探究.实验结果表明,旋转角度θ对折射率的不确定度影响最大,厚度d次之,干涉条纹计数K影响最小.PASCO实验平台配合迈克耳孙干涉仪可以准确、高效的记录干涉条纹在"吞吐"时光强的变化,降低条纹计数测量的不确定度,从而提高透明材料折射率的计算精度.同时该方法还可用于和透明材料折射率相关的其他特性的测量.     

激光等密度等倾干涉条纹法测定透明介质的厚度和折射率

提出用迈克尔孙干涉仪等密度等倾干涉条纹法测定透明介质（玻璃、薄膜等）的厚度和折射率的方法。实验证明,这种方法是正确、有效和间便的。     

对白光干涉法测量透明介质折射率实验的探讨

在时域中求解得到,光路中存在色散介质的情况下,白光双光束干涉光强度.由此证明了:用白光干涉法测量得到的是白光在色散介质中的群折射率,而并非相关报道中认为的折射率;讨论了介质厚度及色散对于涉条纹的可见度和干涉条纹显现时动镜移动范围的影响.上述结论得到了实验验证.     

各向异性介质的平行平板干涉

提出了各向异性介质平行平板干涉中的相位差计算方法.证明了e光干涉产生的条纹为严格的椭圆曲线,椭圆长短轴的比值等于o光主折射率与e光主折射率之比,而与晶体厚度、干涉级等参数无关.拍摄了实验干涉图,并用最小二乘法对干涉条纹进行椭圆曲线拟合,结果与理论完全一致.本文提出的方法可用于晶体主折射率比值的精确简便测量.     

掠入射法测量液体折射率实验现象分析

掠入射法是基于全反射定律,采用几何光学原理来测量液体折射率的一种方法.文中对掠入射法测量透明液体折射率实验中出现的干涉条纹进行了定量分析,认为在分光计望远镜中观察到的干涉条纹是光线进入辅助透镜和直角棱镜间被测薄液膜干涉形成的,通过定义干涉条纹疏密度,对于薄膜引起的光程差与干涉明纹(或暗纹)间距两者间的关系进行讨论,其讨论的结果与实验结果一致.     

基于MATLAB的等厚干涉数值模拟

运用MATLAB软件平台设计了等厚干涉图样模拟的程序。使用者可通过命令窗口输入相关参数的值,运行程序得到等厚干涉图样。本文通过改变相关参数的值,分析薄膜夹角、介质折射率、入射光波长、入射角度对等厚干涉条纹间距的影响。此外,还研究了非单色光对等厚干涉条纹可见度的影响。     

色散及视觉函数对白光干涉测折射率影响的分析

对使用迈克耳孙干涉仪白光干涉测量透明介质折射率实验中出现的3种异常现象的原因进行了分析。在考虑介质色散并对人视觉函数作适当简化的情况下,求得了干涉条纹可见度、可见白光干涉条纹时动镜的移动范围和折射率的表达式,并由实验对其结果进行了验证。结果表明,运用此方法测量所得的平行板透明介质折射率并非通常由相速度所定义的相折射率,而是白光在介质中由群速度所定义的群折射率。此方法可以用测量到的群折射率和已知的相折射率求得介质在中心波长处的色散。     

用迈克尔逊干涉仪测薄膜厚度

在教材中,常可见到“把折射率为n的薄膜放在迈克尔逊干涉仪的一臂上,由此干涉条纹产生移动,测得共移动N条,若光源的波长为λ,求薄膜的厚度”的习题。实际上由于薄膜的引入,导致干涉条纹的移动是个突变过程,无法测出干涉条纹移动的条数N。但这并非说不能利用迈克尔逊干涉仪测量薄膜的厚度,利用迈克尔逊干涉仪不仅可以测量透明介质膜的厚度,而且还可测量金属膜的厚度,下面介绍利用迈克尔逊干涉仪测量非透明金属膜厚度的原理及方     

干涉法测量光学材料非线性折射率的方法研究

提出了一种基于楔形平板等厚干涉原理测量光学玻璃非线性折射率变化的方法。在理论分析的基础上,建立了变形的等厚干涉条纹变化△e／e与待测玻璃平片（K9玻璃）折射率变化量△nb之间的数学模型;在选取一定的实验条件下,获得等厚干涉实验测量干涉图样,并利用MATLAB对实验所得的干涉图进行图像数据处理分析计算,恢复出非线性变化光学玻璃材料的折射率变化量△nb该方法的测量精度可达10^-6。     

Group refractive index measurement by fringes of equal chromatic order

Fringes of equal chromatic order in transmission across a thin liquid or a thin solid sample inside a wedge interferometer, followed with a grating spectrograph, are produced. A single-shot interferogram of the air and sample regions is recorded. Locations of fringes maxima in the air region are fitted in a numerical procedure based on Cauchy's dispersion function. Then it is used for measuring the interferometric gap thickness. The order of interference in the sample region is represented by a third-order polynomial in the wavenumber for deducing the sample group refractive index. An error analysis of the measured group refractive index is given. The method is applied for measuring the group refractive index of water and mica samples across the visible spectrum. The method measures both the sample thickness and its group refractive index. It is static with no moving parts and suitable for thin liquid or solid samples without immersion liquids.     

Liquid refraction and dispersion measurements by multiple-beam white-light Newton's fringes

Multiple-beam white-light Newton's fringes in transmission are produced in a Newton's interferometer containing a liquid sample and followed with a grating spectrograph. An equation describing the shape of the formed interference fringes is derived. A simple procedure is introduced for analyzing the resulting interference fringes. This enables the determination of both: the liquid refractive index, the fringe order of interference and the thickness at the point of contact. Errors of the measured liquid refractive index are discussed. The method is used for measuring the refraction and dispersion of glycerin, dimethylformamide (DMF) and water across the visible spectrum. The method is a single-shot, static, material-economic and low-cost interferometric one.     

Interferometric determination of refraction and dispersion of human blood-serum, saliva, sweat and urine

Multiple-beam interference fringes of equal chromatic order are produced in air and liquid sample interferometric gaps. The two gaps are of the same thickness and simultaneously enclosed in a wedge interferometer. A single shot interferogram containing fringes in the two gaps is sufficient to deduce the needed experimental data. Locations of the fringe maxima, in the two gaps, are introduced in a non-numerical procedure for determining the gap thickness and the liquid-phase refractive indices across the visible spectrum. The method has been used for measuring the phase refractive indices of human blood-serum, saliva, sweat, urine and water liquids. A third-order polynomial dispersion relation is applied for fitting the measured phase indices. Group refractive indices have been derived and fitted to the same dispersion formula.     

Optical sensors based on Fabry–Perot resonator and fringes of equal thickness structure

We propose theoretically two optical sensor structures based on Fabry–Perot resonator and fringes of equal thickness structure. Different from the conventional slab waveguide sensors in which the sample interacts with the evanescent field in the cladding layer, the proposed sensors contain the sample in the core layer. The first proposed sensor comprises a piezoelectric material as a substrate with the driving potential difference as the sensing probe for refractive index changes of the sample. The second sensor comprises fringes of equal thickness structure with the number of fringes per unit length is the probe for changes in the index of the sample. The calculations reveal that the proposed sensors have high sensitivity to changes in the refractive index of the sample.     

电光材料调制误差对平行光束干涉投影的影响

为研究电光材料调制误差对干涉条纹质量的影响,建立了电光晶体对干涉条纹的成像模型,分析了晶体折射率、平面度与波前调制的关系及其非理想情况下的条纹成像特征。实验表明,晶体折射率的畸变会使干涉条纹变形,折射率离散化阶数直接造成投影条纹的高次谐波成分,甚至使投影条纹严重失真;在折射率线性增长的情况下,晶体平面度在0.1 μm的范围内也会引起干涉条纹畸变。     

高斯光束照射下的等倾双光束干涉

根据等倾干涉原理,对高斯光束经薄膜反射后的光强、可见度、条纹分布进行了理论分析,讨论了入射角对光强、可见度分布的影响,相位角对条纹可见度的影响.数值模拟计算表明：沿着垂直于光传播方向的平面,反射光束叠加区域为一圆斑,随着入射角的增大,可见度逐渐减小,光强分布偏离了高斯分布,光斑变大,峰值减小.干涉条纹在空间的分布类似于平面波的薄膜等倾干涉,主要由入射角及薄膜厚度决定.     

利用劈尖的等厚干涉测量液体的折射率

利用劈尖的等厚干涉测量了不同液体的折射率。在不改变劈尖夹角前提下,通过读数显微镜,分别得到劈尖在空气和液体中的干涉条纹间距ΔX_空、ΔX_液,从而运用n=ΔX_空/ΔX_液得到各液体的折射率。通过本实验,丰富了折射率测量的方式。     

LFI法测量半透明油的折射率

LFI方法曾被用来测量大直径光纤的折射率.用一半盛油一半为空气的毛细管代替光纤,并用聚焦的条形光束照射毛细管,空气与油的干涉条纹同时产生.根据空气的条纹可以确定参数b,根据一组已知折射率的标准样品可确定另一参数c,同时可以建立标准液体最外条纹的偏折角与折射率的标准曲线.对于未知折射率的样品,一旦测量出其最外条纹的偏折角,从标准曲线上就可以读出其折射率.实测了一组半透明油的折射率,其结果与阿贝折射仪测量结果接近.     

High precision refractometry based on Fresnel diffraction from phase plates

When a transparent plane-parallel plate is illuminated at a boundary region by a monochromatic parallel beam of light, Fresnel diffraction occurs because of the abrupt change in phase imposed by the finite change in refractive index at the plate boundary. The visibility of the diffraction fringes varies periodically with changes in incident angle. The visibility period depends on the plate thickness and the refractive indices of the plate and the surrounding medium. Plotting the phase change versus incident angle or counting the visibility repetition in an incident-angle interval provides, for a given plate thickness, the refractive index of the plate very accurately. It is shown here that the refractive index of a plate can be determined without knowing the plate thickness. Therefore, the technique can be utilized for measuring plate thickness with high precision. In addition, by installing a plate with known refractive index in a rectangular cell filled with a liquid and following the described procedures, the refractive index of the liquid is obtained. The technique is applied to measure the refractive indices of a glass slide, distilled water, and ethanol. The potential and merits of the technique are also discussed.