Effects of optical axis direction on optical path difference and lateral displacement of Savart polariscope

A simple method is applied to calculating the optical path difference （OPD） of a plane parallel uniaxial plate with an arbitrary optical axis direction. Then, the theoretical expressions of the OPD and lateral displacement （LD） of Savart polariscope under non-ideal conditions are obtained exactly. The variations of OPD and LD are simulated, and some important conclusions are obtained when the optical axis directions have an identical tolerance of ／pm 1^{{／circ}}. An application example is given that the tolerances of optical axis directions are gained according to the spectral resolution tolerances of the stationary polarization interference imaging spectrometer （SPIIS）. Several approximate formulae are obtained for explaining some conclusions above. The work provides a theoretical guidance for the optic design, crystal processing, installation and debugging, data analysis and spectral reconstruction of the SPIIS.

Optical Design for the Off-axis Reflective Optics with Wide Field

Reflective optics with wide field of view has been applied more and more widely in EUVL or space optics, and also plays an important role in promoting scientific and technological research. Among the reflective optics, the off-axis reflective optics is the most hopeful solution to the ever-highest demands of these applications. This paper gives the requirements of both the above mentioned applications and the similarities and differences between these two kinds of optical systems. Finally, a design example of off-axis reflective optics with wide field of view is presented and described.

Observation of tropospheric NO_2 by airborne multi-axis differential optical absorption spectroscopy in the Pearl River Delta region,south China

An airborne multi-axis differential optical absorption spectroscopic （AMAX-DOAS） instrument was developed and applied to measure tropospheric NO2 in the Pearl River Delta region in the south of China. By combining the measurements in nadir and zenith directions and analyzing the UV and visible spectral region using the DOAS method, information about tropospheric NO2 vertical columns was obtained. Strong tropospheric NO2 signals were detected when flying over heavilly polluted regions and point sources like plants. The AMAX-DOAS results were compared with ground-based MAX-DOAS observations in the southwest of Zhuhai city using the same parameters for radiative transport calculations. The difference in vertical column data between the two instruments is about 8%. Our data were also compared with those from OMI and fair agreement was obtained with a correlation coefficient R of 0.61. The difference between the two instruments can be attributed to the different spatial resolution and the temporal mismatch during the measurements.

Measurement of Optic Axis Direction Based on Interference Fringe Method

In order to conquer the defect in low precision and small range for measuring optic axial angle based on conoscopic interference method, interference fringe method is proposed. It is not the distance deviating from melatope but fringe numbers to decide optic axial angle. Fringe numbers are divided into integer portion and decimal fraction portion, the decimal fraction portion is calculated by non-linear interpolation method and integer portion is determined by the relative placement of interference fringes in the principal section. Extremum arithmetic of digit image is proposed and can be used to determine the interference fringes conveniently and precisely. After different niobate crystals were measured, the result shows that measurement range of optic axial angle is increased efficiently and measurement error is reduced to 0.1°.

A sensitive method of determining optic axis azimuth based on laser feedback

A sensitive method to determine the optic axis azimuth of the birefringence element is presented, which is based on laser feedback. The phase difference between the two intensities in birefringence feedback changes with the angle between the optic axis of the birefringence element and laser original polarization. The phase difference is highly sensitive to the relative position of the optic axis and the laser original polarization. This method is used to highly precisely determine the optic axis azimuth, and is able to distinguish between the fast axis and the slow axis of the birefringence element. Theoretical analysis and experimental results are both demonstrated.

Optical Design and Stray Light Analysis of the Space Infrared Optical System

This article describes a novel configuration design for a re-imaging off-axis catadioptric space infrared optical system,and in order to satisfy the signal noise ratio requirements of the system,the stray light of the system is necessary to analyze and restrain. The optical system with a focal length of 1 200 mm,an entrance pupil diameter of 600 mm,an F-number of 2,a field of view of 3°× 0. 15°,a working wave band of 8 μm-10 μm,and the image quality of the optical system almost approach to diffraction limits in all field of view.Then the mathematical models of stray light are built,and the suppressive structure is established to eliminate the effect of stray light. Finally,TraceP ro is used to analyze and simulate stray light with and without the suppressive structure,and also get the results of the PST curves. The results indicate that appropriate optical system and suppressive structure can highly reduce the stray light of the space infrared optical system.

A dual-axis, high-sensitivity atomic magnetometer

Atomic magnetometer （AM） operated in a spin-exchange relaxation-free （SERF） regime features superior sensitivity and non-cryogenic operation, and thus is competitive with the best superconducting quantum interference devices. Previously, SERF AM with fT/Hz1/2 level sensitivity commonly acted as a single-axis sensor. Here we demonstrate a dual-axis SERF AM capable of simultaneously and independently detecting x-and y-field components with a sensitivity of 20 fT/Hz1/2. As there is no necessity to worry about the cross-talk effects arising from field modulations, the dual-axis scheme proposed here is of particular interest to AM array and hence the biomagnetic applications.

Optical terminal analysis of a multigrating tiled compressor in a PW-class CPA-laser

In the highest-power chirped-pulse amplification lasers, the pulse must be stretched in time, amplified, compressed in a grating compressor and subsequently focused by off-axis parabola to obtain a high peak power. In the optical terminal, the temporal and spatial effects of mismatched multigrating tiled compressor on the far-field pulse are critical factors to be analysed. In this paper, a k-space raytracing model is proposed for the temporal and spatial analyses of possible errors in a four-grating single-pass tiled compressor. The results show that the last grating affects mainly the partial focal spot, while the middle two gratings affect the temporal waveform, and the partial focal spot needs much higher error control than that in the temporal domain in a picosecond pulse compression.

Geometrical principium of fewer-axis grinding for large complex optical mirrors

Ultraprecision grinding is an important approach to efficiently fabricate large complex optical mirrors, and five-axis grinding method is commonly used for ultraprecision grinding. However, this method can hardly meet the high stiffness requirement for grinding large mirror, especially with a diameter over 2 m. Meanwhile, the use of fewer-axis grinding solves this problem, as it reduces the number of the grinder's axes to improve the rigidity of the system and minimize deformation for hard and brittle materials. But its characteristic of unfixed grinding point which changes with workpiece surface curvature increases geometric complexity and requires a higher geometric shape accuracy of grinding wheel. This paper parameterizes grinding wheel's geometric shape, reveals the relationship between fewer-axis and five-axis grinding methods from the point of view of the differential geometry, and establishes virtual-axis equivalence principium of feweraxis grinding. A quantitative method to determine grinding wheel's geometric parameters and its shaft inclination angle is proposed based on the requirements of geometric properties of optical mirror, grinder features and grinding process. Moreover, according to the properties of Gauss curvature of curved surface, the wear law of the toric grinding wheel is found and the surface geometric error distribution due to wear is achieved for fewer-axis grinding. The correctness of the principium and method above are verified through simulations.

Definition and expression of non-symmetric physical properties in space for uniaxial crystals

The anisotropic physical property is the most noteworthy feature of crystals.In this paper,the subscript change method is used to analyze the sign changes of different tensors describing physical properties in uniaxial crystals.The distribution of some physical properties in special point groups exhibits non-symmetry in eight quadrants,which should attract the attention of crystal research.The difference between the crystallographic and physical coordinate systems and the lack of crystal symmetry operations are considered to be the origins of the non-symmetry.To avoid ambiguities and difficulties in characterizing and applying crystal physical properties,eight quadrants in space should be clarified.Hence,we proposed the use of piezoelectric properties to define the positive direction of the optical coordinate axis prior to the research and applications of optical properties.

Optic Axes and Elliptic Cone Equation in Coordinate-Invariant Treatment

We derive for crystal optics in coordinate-invariant way the cone approximation of refraction vectors in the neighborhood of optic axes and determine its invariants and eigenvectors. It proved to describe an elliptic cone. The second invariant of the operator of the wave equation with respect to similarity transformations determines the special cases of degeneration including the optic axes where the polarization of the waves due to self-intersection of the dispersion surface is not uniquely determined. This second invariant is included in all investigations and it is taken into account in the illustrations. It is biquadratic in the refraction vectors and the corresponding forth-order surface in three-dimensional space splits in two separate shells and a non-rational product decomposition describing this is found. We give also a more general classification of all possible solutions of an equation with an arbitrary three-dimensional operator.

星载激光雷达视轴监测系统设计

提出了一种针对星载激光雷达在轨高精度光轴监测与标定需求的多光轴监测方法,该方法基于主动激光光源。通过使用785 nm的激光,分束后分别照射到星敏感器的基准棱镜和接收望远镜的取光棱镜,反射信号被聚焦至监视相机的焦平面,实现了对接收光轴及星敏光轴的精确监测。此外,监视相机还同步采集发射激光的部分能量,用于测量监测发射光轴。文中详细描述了光学系统的设计流程及关键组件的优化方案,并通过地面真空环境试验及在轨监测数据进行了验证。设计结果表明,各监视通道的成像质量达到了衍射极限,收发光轴的设计精度分别为0.09μrad和2.28μrad,关键组件取光棱镜的温控精度达到了±0.2℃。地面的真空热光试验结果进一步验证了该方案的高精度光轴监视能力,收发光轴的监测精度均优于3μrad。最后通过分析激光雷达入轨后的测量数据,确认了视轴监测系统的工作稳定性,成功实现了在轨的高精度光轴监视。该研究成果为星载激光雷达提供了一种有效的在轨高精度光轴监测与标定解决方案。

新型旋转激光扫描系统轴系调整与误差标定

旋转激光扫描系统是一种基于精密转台结合多路激光的空间多目标并行角度传感系统。为改善系统光源性能,设计了一种采用光纤从外部导入光源的新型轴系结构。但是当激光以一定角度穿过中空的转轴进入镜组后,若倾斜入射柱镜,将导致出射的扫描光面型发生变化。针对此问题,研究了一种基于平行线的传递性的激光光轴姿态的调整方法,并借助激光跟踪仪测量平台,分别对光轴与转轴轴系进行拟合,建立了对光轴倾斜误差的标定方法。实验结果表明,调整后光轴与转轴轴线的空间夹角优于0.15°,完全满足扫描光截面中心直线度对激光入射柱镜的角度要求。该调整方案可用于系统的装配环节,使扫描光更加接近理想平面,有助于系统测量精度的提升。

一种可调焦离轴两反光学系统精密调校工艺技术研究

针对可调焦离轴两反光学系统的精密装调,提出了一种共基准调校方法,使导轨导向与主镜和次镜光轴均以同一基准进行精确调校,实现导轨运动轴线与主镜和次镜光轴平行。主镜、次镜系统光轴一致性调试采用初调整和精调整两步完成,初调整实现主镜和次镜基本位于理论安装位置,降低装调误差,然后进行计算机辅助装调,实现主镜和次镜光轴一致性精调整,使系统波像差满足要求。实验结果表明:无穷远处系统波像差RMS达到(1/15)λ(λ=632.8 nm),系统衍射分辨率达到0.64″,系统调焦至10 mm处,实测主镜、次镜系统所成焦距为1608 mm,系统分辨率为2.6″,达到设计要求。

高功率激光辐照下光学天线的像质研究

离轴两反光学天线在高功率激光系统中起到改变光束直径的作用,而高功率激光加载下所产生的热效应使光学天线的像质劣化,严重影响高功率激光系统的性能。为量化其影响效果,建立了离轴两反光学天线的有限元分析模型,模拟高功率激光作用环境,完成了激光加载下的瞬态热分析以及静力学分析,并得到离轴两反光学天线激光加载时间对波前劣化的影响关系。使用齐次坐标变换的方法求解离轴主次镜的刚体位移,具体分析了各项刚体位移随加载时间的变化情况。通过Zernike多项式拟合的方法完成了镜面的波面拟合,将拟合结果导入ZEMAX中,最终得到了该光学天线在平均功率为1 000 W,重频为0.2 Hz,入光直径为30 mm的激光加载300 s下的波前均方差为0.064 6λ。为了进一步验证模型的准确性,使用较低功率(10 W)激光进行原理等效实验,结果表明光学天线在激光加载下实际波像差与模型仿真结果基本相符,偏差小于7.93%,该方法可以有效评价离轴两反天线在高功率激光加载下的像质劣化情况。

基于笼屉结构的机载高能激光系统光学中舱温度适应性研究

相较于车载、舰载设备,机载设备受体积及工作环境的限制,发展较为缓慢。针对机载设备的轻小型化要求,系统采用“光路堆叠”思想,提出笼屉式分层结构,实现了系统体积的要求。因光学中舱中包含精跟踪及主激光支路,温度变化时各支路间的光轴一致性难以保证,导致跟踪目标发生偏移,主激光支路无法对目标进行精确打击,严重影响系统的工作。为解决上述问题,对光学中舱进行有限元仿真分析,研究光学中舱在20±5℃情况下各镜片的变形。对镜片变形中影响光轴偏折的刚体位移进行提取计算,计算出单个镜片的偏转角度。根据反射棱镜安装误差理论对各支路间的光轴偏移量进行计算,分析精跟踪支路与主激光支路光轴一致性偏差。经过仿真分析,系统精跟踪支路与主激光支路光轴方位偏差为109.634μrad,俯仰偏差为132.952μrad。在实验室中进行25℃温度实验,结果表明,系统精跟踪支路与主激光支路光轴方位偏差为104.019μrad,俯仰偏差为125.009μrad,与仿真结果误差分别为5.40%、6.35%,验证了仿真结果的合理性。

国外转塔式光电瞄准吊舱技术发展分析

对国外转塔式光电瞄准吊舱进行了划代,介绍了典型第三代吊舱的主要技术特点,定义了衡量光电吊舱集成度的四个评价标准:通光孔径与舱体直径之比、通光孔径的立方与系统重量之比,舱体直径的立方与系统重量之比以及有效载荷重量与系统重量之比,实现了从宏观层级对性能相近的光电瞄准吊舱功能密度或技术水平的定量评价。介绍了国外典型装备的发展状况,重点针对美国MTS-B吊舱、土耳其ASELFLIR350吊舱及之后的400/500、加拿大MX-15D吊舱、法国EUROFLIR410吊舱和德国ARGOS II HDT等典型产品进行了对比分析,介绍了各自的技术风格、特点和重要载荷;通过正向设计评估验证了MTS-B前置望远系统的性能指标和ASELFLIR350的光学有效载荷;总结了现代光电瞄准吊舱的几大趋同化技术特点:多波段共孔径折反式主系统+旁轴小口径次系统的光机架构正取得共识、多种波段的激光探测技术日益倾向主动光学方向、基于多轴多框平台和快反镜相结合的复合轴控制技术正在普及、详查探测更注重目标细节区域增强、多波段图像融合信息处理技术在显控中越发重要。

弱风条件下斜程海洋湍流中涡旋光束的传输特性

光束在海洋介质中传输会极大地受到海洋湍流的影响。此外,涡旋光束轨道角动量的复用会极大地提高系统容量,因此研究涡旋光束在海洋湍流中的传输具有重要意义。在水平海洋湍流理论基础上,创新性地构建了斜程路径上海洋湍流相位屏模型,以相位结构函数为依据验证了海洋湍流相位屏的准确性,根据多相位屏法搭建准直高斯涡旋光束在海洋湍流中的上行传输链路模型。数值模拟并分析了不同天顶角、海洋湍流内外尺度及拓扑荷数等其他海洋湍流参数对准直高斯涡旋光束经海洋湍流上行传输的光强及相位分布、光束漂移、轴上闪烁指数和长曝光光斑半径的影响。结果表明:涡旋光束的拓扑荷数越小、天顶角越小,光束受到湍流的影响越大;在海洋湍流上行传输链路中,准直高斯涡旋光束的光束漂移、轴上闪烁指数及长曝光光斑半径随海洋湍流外尺度的增大而增大,且主要受传输距离的影响;理想情况下,取海洋湍流外尺度为无穷大,会高估湍流对光束的影响;由于涡旋光束的本身特性,拓扑荷数对光强及相位分布和长曝光光斑半径的影响也较为显著。

基于改进遗传算法的飞行器光轴自动校准优化

飞行器光轴质量监控过程中,主要通过标准遗传算法完成光轴参数优化求解,易出现过早收敛和停滞现象的问题,导致校准优化后光轴偏移量依旧较大。为了降低飞行器光轴偏移量,提出基于改进遗传算法的飞行器光轴自动校准优化方法。以牛顿环干涉条纹为依据,采用正交实验方法实现光轴平行性自动校准处理,获取合理的光轴校准参数取值区间。针对飞行器光轴系统定义一个坐标系,在其中分析照准轴误差、经轴误差、纬轴误差和光轴指向误差,以最小光轴平行度综合误差为目标构建光轴自动校准优化目标函数。采用自适应交叉、变异概率改进遗传算法,对优化目标函数进行迭代求解,获取最佳光轴校准参数,实现飞行器光轴自动校准优化。实验结果表明,该方法优化处理后,飞行器高温光轴和低温光轴的偏移量仅为0.34 mrad、0.296 mrad,证明该方法降低了飞行器光轴偏移量,满足了飞行器光轴性能提升要求。

热像仪的光轴热稳定性仿真及拓扑优化研究

热成像仪由于工作环境较为恶劣,且自身发热量较大,容易导致热像仪光轴发生热偏移,严重影响其瞄准性能。为了提高红外热像仪的光轴热稳定性,以某型热像仪光轴敏感部件——折转镜为主要研究对象,研究其在不同环境温度条件下的光轴变化情况,并通过构建折转镜的有限元仿真模型以及试验测试系统,获得与试验数据一致性较好的有限元模型;以此为基础,采用基于变密度法的拓扑优化仿真技术,以刚度最大化为设计目标,以体积分数为约束,对折转镜座进行了拓扑优化设计。通过试验测试得出,优化设计的折转镜座的光轴高温偏移量由46.1″减小到25.5″,减小了44.7%,折转镜座的光轴低温偏移量由92.9″减小到51.0″,减小了45.1%,极大地提高了折转镜的光轴热稳定性。最后,将优化后的折转镜安装到某型热像仪中进行整机试验测试,热像仪整机的高温光轴偏移量由0.461 mrad减小到0.340 mrad,下降了26.2%,低温光轴偏移量由0.485 mrad减小到0.296 mrad,下降了39.0%,证明了仿真与拓扑优化模型的可行性与有效性,为后续红外热像仪整机的轻量化设计与性能提升奠定了基础。