Uncertainties in Small-Angle Measurement Systems Used to Calibrate Angle Artifacts

We have studied a number of effects that can give rise to errors in small-angle measurement systems when they are used to calibrate artifacts such as optical polygons. Of these sources of uncertainty, the most difficult to quantify are errors associated with the measurement of imperfect, non-flat faces of the artifact, causing the instrument to misinterpret the average orientation of the surface. In an attempt to shed some light on these errors, we have compared autocollimator measurements to angle measurements made with a Fizeau phase-shifting interferometer. These two instruments have very different operating principles and implement different definitions of the orientation of a surface, but (surprisingly) we have not yet seen any clear differences between results obtained with the autocollimator and with the interferometer. The interferometer is in some respects an attractive alternative to an autocollimator for small-angle measurement; it implements an unambiguous and robust definition of surface orientation in terms of the tilt of a best-fit plane, and it is easier to quantify likely errors of the interferometer measurements than to evaluate autocollimator uncertainty.     

Thermo-optical characterization of CdZnS nanoparticle colloids

Thermo-optical properties of cadmium zinc sulfide (CdZnS) nanoparticle colloids are investigated by interferometry technique. The nanoparticle colloids are synthesized by an improved co-precipitation method. Transmission electron microscopy, UV–vis spectrometry and X-ray diffraction analysis are used to characterize the CdZnS nanocrystals. The thermo-optic coefficient of the colloids has been determined using a Fizeau interferometer. For this purpose, the interference patterns are deformed by a photothermal phase shift which is locally induced in the sample by the focused pump laser beam. The change in the refractive index at this region imposes a shift on the phase of the fringe patterns. Fourier analysis performed on the interference patterns allows us to estimate the values of the thermo-optic coefficient and nonlinear refractive index of the sample. It is shown that the CdZnS nanoparticle colloids enhance the absorption of the laser light and induce high rise in the temperature of the sample, which leads to the nonlinear phase shift.     

拼接镜主动光学共相实验

考虑拼接望远镜子镜之间保持共相位可使拼接镜达到衍射极限,本文建立了一套主动光学实验系统来测量和调整拼接镜子镜之间的相位差和精度以实现子镜之间的共相位。拼接镜由3块正六边形球面子镜组成,子镜对边长为300mm,曲率半径为2000mm。首先,使用Shack-Hartmann传感器和高精度微位移平移台使子镜之间精确共焦,使用球径仪调整子镜之间的高度差到微米量级;然后,运用白光斐索干涉原理对子镜高度差进行调整;最后,运用子孔径衍射原理测量子镜之间的高度差,并调整使其共相位。为了验证标定效果,对光纤光束进行了成像实验,受光纤直径的限制,拼接镜上用于成像的口径为100mm。实验结果显示,白光斐索干涉的测量精度优于100nm,子孔径衍射的测量精度优于16nm,共相位标定后,系统能够实现衍射极限成像,表明提出的方法适用于拼接望远镜的共相位标定。     

基于光强自标定移相算法检测光学面形

考虑菲佐型波长移相干涉仪中波长可调谐激光器光强与调节电压之间的关系会对相位计算精度造成影响,本文提出了一种基于光强自标定的波长移相算法。首先,分析了波长可调谐激光器调节电压与输出光强之间的关系,建立了数学模型;然后,依据最小二乘判据,推导出了波长移相干涉仪的光强自标定移相算法。最后,实施了仿真实验,通过计算机生成背景光强具有一定变化的12幅干涉图,利用所提出的算法进行了相位恢复。结果表明,提出的算法可以很好地免疫激光器的光强变化,实现高精度的相位恢复。对口径为100mm的平面镜的测量结果显示RMS为0.005λ,PV为0.073λ。与ZYGO干涉仪测量结果的比较显示,两次测量面形的偏差RMS为0.0014λ,PV为0.022λ。得到的结果证明了算法的可行性及在菲佐型波长移相干涉仪中的实用性。     

Absolute Measurement Fiber—optic Sensors in Large Structural Monitoring

The security of civil engineering is an important task due to the economic,social and evironmental significance.Compared with conventional sensors.the optical fiber sensors have their unique characteristics.Beijing durable,stable and insensitive to external perturbations,they are particular interesting for the long-term monitoring of civil structures.Focus is on absolute measurement optical fiber sensors,which are emerging from the monitoring large structural,including SOFO system,F-P optical fiber sensors,and fiber Bragg grating sensors.The principle,characteristic and application of these three kinds of optical fiber sensors are described together with their future prospects.     

费索激光波长计的温度补偿

论文概述了费索干涉仪型激光波长计的原理和标定。详细分析了环境温度变化使仪器参数发生微小变化；论述了ＳＩＯＭ－０１激光波长计以一种新颖的将标准激光引入测量光路的方法，随时对仪器参数实行单点标定，克服了由环境温度变化引进的测量误差。     

影响Fizeau波长计精度因素的分析

本文分析了影响Fizeau波长计测量精度的几种因素,给出了对测量环境温度、电磁干扰以及光束模式应控制的范围。     

Determination of the Spectral Dispersion Curves of Highly Oriented Fibers Using Multiple-Beam Microinterferometry

ABSTRACT

A method is suggested with its mathematical analysis to determine the spectral dispersion curves of highly oriented fibers using multiple-beam Fizeau fringes in transmission. This method depends on the use of the well-known Caushy's dispersion formula for determining the initial interference order of the deviated fringes inside the fibers. The suggested method overcomes the difficulties of measuring large optical path length differences that are produced by highly oriented fibers. The spectral dispersion curves obtained using this method are in good agreement with those obtained using conventional variable wavelength interferometry (VAWI) technique. Microinterferograms are given for illustration.     

Absolute interferometric test for high numerical-aperture spherical concave surfaces: Gravitational effect

Spherical concave surfaces with high numerical apertures are required in industry for lithography optics at ultraviolet and X-ray wavelengths. Among the systematic errors in these spherical-surface test, the gravitational deformation has not been separated from the other optical aberrations. We utilized a two-surface comparison method to quantify the gravitational deformation in a vertical Fizeau interferometer. Certain aberrations vary with rotation around the optical axis. We averaged the ordinary aberrations and isolated the aberration caused by gravitational deformation. Experimental results show that a 4-in concave surface with an F-number 0.75 reveals to have a gravitational deformation of 7 nm peak-to-valley.