长焦物镜折衍混合式平行光管设计

阐述了传统平行光管与折衍混合式平行光管的设计方法比较,给出了折衍混合式设计的优化结果。经分析,优化后的设计在点列图、光学传递函数和像差曲线等方面均明显好于传统设计方法,对其它大孔径平行光管的设计具有很强的参考价值。     

复消色物镜的波差法光学设计

采用波差法进行复消色物镜的光学设计。以球差与波差、色差与波色差的关系为基础,推导出了波差与结构参数之间的关系方程式。运用得到的方程式来计算初始结构,可以充分发挥用计算机编程处理复杂问题的优势,使复杂的计算问题能够快速解决。针对光学设计中的两大难点之一——复消色大口径长焦距平行光管物镜的设计,利用自行编写的光学设计程序,采用低价的国产玻璃成功地设计出高质量的复消色大口径长焦距平行光管物镜。同理,选取不同的玻璃组合,也能设计出高质量的复消色摄影物镜。最后给出多个设计实例对采用的设计方法进行了验证,结果表明,采用波差法进行复消色物镜的光学设计简单易行,且设计的物镜质量高,成本低。     

准直器插入损耗分析

降低准直器的插入损耗是生产准直器的难点，本文在几何光学和高斯光束传输理论的基础上，利用矩阵光学原理和高斯光束耦合理论对准直器的原理和损耗进行计算和分析，提出一种用自聚焦透镜与球面透镜进行匹配的方法，并通过实验证明该方法能有效降低准直器的插入损耗，在生产过程中将逐渐采用这种方法进行装配，以提高生产效率．     

基于可检测性的设计理念的保偏双光纤准直器精密封装技术

将确保装配和确保制造的设计理念引入到光通信产品开发和生产中,从能否方便地满足保偏双光纤准直器的低插入损耗和高回波损耗的检测指标出发,研究了保偏双光纤准直器的合理结构和装配工艺,提出了基于可检测性的设计理念的保偏双光纤准直器的精密封装技术。该方法已在批量生产实践中应用,提高了生产效率,保证了产品的合格率。     

基于LED的均匀照明投影光路设计

在方棒照明系统的基础上,根据LED的发光特性和独特的准直结构,设计了一款基于LED的均匀照明投影光路系统．其优点是结构简单、开发周期短、加工成本低．仿真结果表明,其均匀度能满足中等要求．     

一种新型的高性能近红外平行光管的研究

采用长焦距单透镜方案,研制了一种新型的高性能近红外平行光管。以单模光纤导出的近红外激光(λ=1053nm)为光源,设计了满足光强均匀性要求的准直物镜焦距,使用新型的近红外消光涂料消除了杂散光的影响,并运用双平板剪切干涉技术完成了平行光管的不可见光束调校。采用自制的1053nm近红外干涉系统测试了平行光管的光学质量,结果表明,准直后的出射光束波面峰谷值(PV)达到0.045λ,光强的均匀性达79.2%。     

校靶镜检定装置设计与图像处理技术研究

根据校靶镜的检定需求,研究了校靶镜检定装置,可完成不同口径的校靶镜检定,扩展了检定范围。采用外调焦平行光管提供20m、50m、100m以及无穷远四种模拟目标,以满足不同目标距离的校靶镜的检定需要。同时采用CCD摄像系统与图像判读程序替代人眼读数,由于数字化图像传感器克服了人眼分辨力的不足,因此简化了校靶过程,校靶精度得到提高,检定时间得到缩短。     

基于准直的X射线进行油间隙受激放电的定位

试验表明,在对Ｘ射线进行准直处理后,实现Ｘ射线激励下油间隙局部放电的定位是可能的,这一方法有望成为油纸绝缘系统局部放电定位的新手段。     

Approximation algorithms for minimizing segments in radiation therapy

Intensity modulated radiation therapy (IMRT) is one of the most effective modalities for modern cancer treatment. The key to successful IMRT treatment hinges on the delivery of a two-dimensional discrete radiation intensity matrix using a device called a multileaf collimator (MLC). Mathematically, the delivery of an intensity matrix using an MLC can be viewed as the problem of representing a non-negative integral matrix (i.e., the intensity matrix) by a linear combination of certain special non-negative integral matrices called segments, where each such segment corresponds to one of the allowed states of the MLC. The problem of representing the intensity matrix with the minimum number of segments is known to be NP-complete. In this paper, we present two approximation algorithms for this matrix representation problem. To the best of our knowledge, these are the first algorithms to achieve non-trivial performance guarantees for multi-row intensity matrices.     

Study of intensity suppression in a gantry beamline for SC200 proton therapy system

ABSTRACT

For proton therapy, a beam intensity of 0.4 nA to 4 nA is typically used with a beam transmission factor of 10. However, because of energy degrading, emittance matching, and energy spread selecting, the ratio of beamline transmission (I_Max/I_Min) for our SC200 proton therapy facility (200 MeV/500 nA) should be far more than 10. Therefore, a novel intensity suppression scheme, based on the installation of two new collimators placed symmetrically with respect to the gantry coupling point, is proposed and verified. First, the feasibility of delivering a beam with variable size at the gantry isocenter is demonstrated. The beam delivery method uses waist-to-waist imaging optics, a symmetric beam method, and the principle of beam line inversion. The relationship between energy and isocenter beam size (in air) is then verified using an empirical formula and a Monte Carlo method. The intensity suppression and subsequent optimization of the gantry beam optics were accomplished through simulations. The results indicate that increases in the entrance beam radius at a specific collimator results in significant changes in the beam optics and intensity behind the collimator. This passive scheme, which produces intentional losses at the gantry coupling point, is demonstrated to be viable.