Multibeam laser writing of diffractive optical elements

A new version of the method of direct multibeam laser writing of diffractive optical elements (DOE) is proposed and investigated. A writing area in the form of an array of focused light spots is formed by splitting the writing laser beam into multiple beams by using a Dammann grating and focusing of these beams in the plane of a moving carrier with a photosensitive material. Adjustment of the radial pitch of writing and correction of the uniformity of the beam intensity is carried out by tilting the Dammann grating and displacing it in the dispersion direction. In writing DOEs, the radial pitch of discrete displacement of the writing area with respect to the plane of the DOE is set equal to or multiple of the average radial distance between the radial projections of the centers of the focused light spots. This version provides improved performance and accuracy due to high-quality paralleling of the writing beam and the averaging effect in superimposed writing.     

大尺寸衍射光学元件的扫描离子束刻蚀

总结了大尺寸衍射光学元件离子束刻蚀技术的研究进展。针对自行研制的KZ-400离子束刻蚀装置,提出了组合石墨束阑结构和多位置分步刻蚀策略来提高离子束刻蚀深度的均匀性,目前在450mm尺寸内的刻蚀深度均匀性最高可达±1%。建立了针对多层介质膜光栅的衍射强度一维空间分布在线检测系统以及用于透射衍射光学元件离子束刻蚀深度的等厚干涉在线检测系统,实现了对大尺寸衍射光学元件离子束刻蚀终点的定量、科学控制,提高了元件离子束刻蚀工艺的成功率。利用上述技术,成功研制出一系列尺寸的多层介质膜光栅、光束采样光栅、色分离光栅以及同步辐射光栅等多种衍射光学元件。     

Ion beam etching of large aperture diffractive optical elements

总结了大尺寸衍射光学元件离子束刻蚀技术的研究进展.针对自行研制的KZ-400离子束刻蚀装置,提出了组合石墨束阑结构和多位置分步刻蚀策略来提高离子束刻蚀深度的均匀性,目前在450 mm尺寸内的刻蚀深度均匀性最高可达±1％.建立了针对多层介质膜光栅的衍射强度一维空间分布在线检测系统以及用于透射衍射光学元件离子束刻蚀深度的等厚干涉在线检测系统,实现了对大尺寸衍射光学元件离子束刻蚀终点的定量、科学控制,提高了元件离子束刻蚀工艺的成功率.利用上述技术,成功研制出一系列尺寸的多层介质膜光栅、光束采样光栅、色分离光栅以及同步辐射光栅等多种衍射光学元件.     

衍射双波段红外光学系统设计

基于定向光栅能对不同波长的不同级光谱闪耀的原理,从一种比较新颖的角度将衍射光学元件成功地应用于双波段红外光学系统设计,使系统在衍射效率达80%的中波红外波段3.8～4.2μm和长波红外波段8.8～11.5μm同时较好地完成像差校正,会聚到共同的焦点。最后以一个f/2单透镜衍射光学系统进行了验证。设计结果表明,此双波段光学系统结构紧凑、原理简单、不需要额外的机械设备,为双波段成像、探测提供了一条新的思路。     

Dynamic correction of the laser beam coordinate in fabrication of large-sized diffractive elements for testing aspherical mirrors

This paper presents a method of improving the accuracy of a circular laser system in fabrication of large-diameter diffractive optical elements by means of a polar coordinate system and the results of their use. An algorithm for correcting positioning errors of a circular laser writing system developed at the Institute of Automation and Electrometry, SB RAS, is proposed and tested. Highprecision synthesized holograms fabricated by this method and the results of using these elements for testing the 6.5 m diameter aspheric mirror of the James Webb space telescope (JWST) are described..     

投影光刻离轴照明用衍射光学元件设计

离轴照明（OAI：Off-axis Illumination）作为一种重要的分辨率增强技术（RET：Resolution Enhancement Technology）被广泛的应用于投影光刻系统。使用衍射光学元件（DOE：Diffractive Optical Element）作为光刻照明系统的光束整形器件,能够在保持较高照明效率的基础上精确控制离轴照明光束的形状及光强分布。本文利用基于傅立叶变换的分步迭代方法进行了该类DOE的优化设计。DOE采用了多台阶位相结构,设计所得8台阶DOE设计结果分别实现了偶极、四极、环形及Bulls-Eye等照明方式,其照明效率都达到了80%以上,与目标光强分布的均方根偏差均小于7％。     

Calibration of laser beam direction for optical coordinate measuring system

For the purpose of measuring free form surfaces of some key parts in the aviation field accurately and effectively, such as blades, a non-contact optical coordinate measuring system is set up in the paper. A laser displacement sensor is mounted on the Z axis of a CMM via a turntable and adjusted to the suitable orientation according to the shape of the target surface. The combination of optical sensor and CMM can reach the full potential of them both. To enable the laser sensor to perform measurement in every direction, a calibration method used to determine the laser beam direction based on a standard sphere is proposed, the principle of which is analyzed in detail in the paper. In the calibration procedure, the sensor moves at an equal step along X, Y and Z axes respectively and then equation sets are established to calculate the unit direction vector of the line which the laser beam is on. In the process of solving the unknown quantities, a new parameter substitution method is applied. Finally, a gauging block and a sphere with known size are used to verify the method. As the experimental results show, the measuring errors in several directions are all smaller than 0.05 mm, which manifests that the calibration method proposed can meet the requirements of reverse engineering.     

消旋检测系统像差校正衍射元件的加工分析

基于一种检测机载制冷型CCD消旋机构的红外光学系统,对非球面为基面的衍射元件进行系统像差校正。通过控制衍射元件非球面基面的方法得到衍射面面型,使用金刚石单点车削技术(SPDT)进行衍射元件的高精度加工,并对影响衍射元件加工精度及加工工艺因素进行了分析。     

Collimation testing of laser beam with holographic optical elements

The shear elements in the shear interferometers of collimation test are commonly plane parallel plates or wedge plates of a small wedge angle. A new holographic shear element that acts as the wedge plate is proposed. The interferometer composed of holographic shear lenses has the advantages of high contrast fringes and adjustable shear amount. It posses the flexibility of altering the measurement sensitivity in a broad range, has more suitability and can meet different measuring requirements. Detailed analysis for the experimental configuration of this system is presented.     

光学非球面三坐标测量中的像散补偿

利用三坐标测量仪在光学非球面镜研磨与粗抛阶段进行面形检测时,测量结果常由于补偿程序不完善而出现像散误差。本文分析了非球面三坐标测量得到的数据,指出测量结果中出现像散误差是测头半径补偿不准确所致。然后,提出了一种离线数据处理方法对测量数据进行补偿来消除像散误差。该方法通过计算网格排列的测头中心点行和列方向的切向量得出曲面上每个点的法向矢量;根据测头半径计算出测头球心到接触点的偏移量,从而实现三坐标测量仪的三维测头半径补偿。球面样板实验显示这种方法可以将该样板测量中的像散峰谷值(PV)由4.921 9μm减小到0.065 2μm,基本消除了测量结果中的像散误差,提高了三坐标测量结果的准确度。实验结果验证了提出的三维测头半径补偿程序的有效性。     

极坐标激光直写系统光轴和转轴对准的光栅反射对准法

提出一种光栅反射对准法:在极坐标激光直写系统中利用光栅反射聚焦光斑来校准光轴和工件台的转动轴;被光栅反射的聚焦光斑成像在CCD上。当聚焦透镜的光轴和工件台的转动轴存在对准误差时,如果转动光栅,激光光斑将在光栅上扫描出一个圆形轨迹。通过观测这个轨迹,能估算出光轴和转轴的对准误差并相应地做出调整减小对准误差。采用光栅反射法,现将光轴和转轴的对准误差减少到小于0.5μm。     

坐标系变换在多件联动加工中的应用

通过设定局部坐标系和镜像坐标系等坐标系变换手段,调用子程序来实现工件多件联动加工,以提高生产率和减少、简化编程量。     

X射线干涉光刻光束线关键光学元件热-结构耦合分析

为了保证上海光源X射线干涉光刻光束线的稳定性,减小热变形对实验结果的影响,对X射线干涉光刻光束线的3个关键光学元件——偏转镜、聚焦镜和精密四刀狭缝进行热-结构耦合分析。首先,计算偏转镜、聚焦镜和精密四刀狭缝所承载的功率密度;然后,建立其有限元模型;最后,获得光学元件的温度场和热变形的结果。结果表明,偏转镜和聚焦镜采用间接水冷方式可有效抑制热变形,冷却后的最大面形误差分别为7.2μrad和9.2μrad。精密四刀狭缝未冷却时,刀片组件温度介于271.56~273.27℃,刀口热变形为0.19 mm,直线导轨热变形为0.08 mm;经过铜辫子冷却后,刀片组件温度降至22.24~23.94℃,刀口热变形降至0.2μm,直线导轨热变形降至0.1μm;采用影像法和接触探头法测试后,刀口直线度、平行度和重复精度均满足技术要求。偏转镜、聚焦镜和精密四刀狭缝的热变形通过间接水冷和铜辫子的冷却方式可以得到很大程度的抑制,进而保证光斑质量。     

Compact high-aperture interferometer with a diffractive reference wave for high-precision referenceless aberration measurements of optical elements and systems

We present the optical layout and actual design of a compact high-aperture referenceless point diffraction interferometer with a diffraction reference wave. The basic concept of this interferometer is based on a single-mode optical fibre with a subwave output aperture, which is used as a source of spherical reference waves. The interferometer is designed for high-precision measurements of the surface shape and aberrations of optical elements. It makes use of a diffraction reference wave and is developed for mass industrial applications. The proposed design does not require the involvement of special external conditions, and reduces the need for calibrated reference surfaces. We evaluate the performance of our interferometer for highprecision measurements and demonstrate its use by presenting results obtained from measuring the shapes of spherical references from various manufacturers and the aberration of a five lens objective.     

基于坐标测量机的轴向立体视觉测量方法研究

为了解决双目立体视觉测量过程中图像匹配计算量大、算法复杂、误匹配率高的问题,提出了一种轴向立体视觉测量方法。该方法由单个摄像机沿坐标测量机轴向先后捕捉被测物表面,利用同轴摄像机外极线相互平行的特性进行同源相点的逐个匹配,并根据视差原理反求三维坐标。着重论述了该方法的原理、同源点匹配及具体实现过程,并通过实验进行了验证,测量了一个塑料盘的边缘并进行了重建。研究结果表明该方法能提高匹配效率,减小误匹配几率,实现快速高效的非接触式测量。     

坐标系旋转在加工圆锥面上孔系的应用

通过实例说明在数控加工中,通过工件坐标系旋转加工圆锥面上孔的方法。     

Laser technologies in micro-optics. Part 1. Fabrication of diffractive optical elements and photomasks with amplitude transmission

This paper is a review of studies carried out by the staff of the National Research University of Information Technologies, Mechanics and Optics (ITMO University, Saint-Petersburg) and the Institute of Automation and Electrometry of the Siberian Branch of the Russian Academy of Sciences (IAE SB RAS, Novosibirsk) in the field of development of laser engineering processes for the formation of the structure of diffractive optical elements (DOEs) and photomasks with amplitude binary and grayscale transmission. This paper also describes the results of the study of laser thermochemical technology for fabricating chrome DOEs and technologies for the fabrication of grayscale DOEs and photomasks based on the use of amorphous silicon and LDW glass.     

Sensitivity of an optimized contour mask technique to errors in fabricating piecewise continuous relief diffractive optical elements

This paper considers the effect of errors in the technological process using an optimized contour mask technique for fabricating piecewise continuous relief diffractive optical elements on the reduction in the backward slopes of diffraction zones and the increase in the diffraction efficiency of the elements. The process parameter tolerances necessary for the implementation of the method are within the parameters of the standard microelectronic processes and equipment. The proposed method can be useful for laser writing systems and projection lithography that form the relief in a photoresist with a backward slope width exceeding 1 µm since it provides a significant improvement in the performance of the fabricated diffraction structures.     

Study on the frame structure modeling of the beam element formulated by absolute Nodal coordinate approach

Accurate seismic analyses of large deformable moving structures are still unsolved problems in the field of earthquake engineering In order to analyze these problems, the nonlinear finite element method formulated by the absolute nodal coordinate approach is noticed Because, this formulation has several advantages over the standard procedures on mass matrix, elastic forces and damping forces in the case of large displacement problems But, it has not been fully studied to build frame structure models by using beam elements in the absolute nodal coordinate formulation In this paper, we propose the connecting method of the beam elements formulated by the absolute nodal coordinate The coordinate transformation matrix of this element is introduced into the frame structure This beam element has the characteristic that the mass matrix and bending stiffiness matrix are constant even if in the case of large displacement problems, and this characteristic is being kept after the transformation In order to verify the proposed method, we show the numerical simulation results of frame structures for a vibration problem and a large displacement problem     

红外3.2～4.5μm波段折射/衍射光学系统的减热差设计

研究了折射/衍射光学元件的温度效应及红外系统的设计理论及具体实例,给出了在红外3.2～4.5μm波段,5°视场范围,冷光栏效率100%,在-40～80℃温度变化范围情况下的红外混合减热差系统的设计结果.结果表明,使用折射/衍射光学系统的减热差设计方案,可令相应的传统光学系统减少一片元件,并且节省了昂贵的硒化锌红外材料.不仅能在较大视场内得到接近衍射极限的成像质量,较宽的温度工作范围,而且结构简单,体积小,重量轻.