Suppression of primary chromatic aberration by genetic algorithm in an advanced telephoto lens

This paper proposes a new method for finding a suitable glass combination set for an advanced telephoto lens via a genetic algorithm (GA). Normally, glass properties, inclusive of index and Abbe number, play a significant role in the elimination of primary chromatic aberration. So many optical glasses (over 300 different refractive types) have been developed hitherto that it is difficult to choose a state-of-the-art glass combination quickly. According to the newly developed GA operations in this paper, however, several suitable glass combinations can be found quickly through a unique sequence of function selection, crossover and mutation. An advanced telephoto lens design is employed in this research, which has the characteristic of being more sensitive to axial aberrations than lateral chromatic aberrations. The GA operations are described in the macro of the optical software program, CODE V. The simulation results in this research show that the primary chromatic aberration is efficiently eliminated after the application of GA. The main goal of this research is that during optimization, error function could be minimized only if primary aberrations are well under control in our first step; in a telephoto lens, the secondary spectrum of longitudinal chromatic aberration and lateral chromatic aberration caused by distortion play a role in chromatic aberration control as well; however, optimization with a combination of both primary chromatic aberration and secondary chromatic aberration will complicate the process with a lot of working variables. The GA method introduced in this paper might efficiently eliminate the primary chromatic aberration first by finding the best glass combination and its trend and then simplifying the following optimization process for all optical systems.     

泛卡塞格林光学系统的色差研究

泛卡塞格林光学系统结构简单、像质优良,广泛应用于空间光学领域中。从对研制完成的谱段位于500～800nm的泛卡塞格林光学镜头的调制传递函数(MTF)的测量结果出发,结合泛卡塞格林光学系统的结构特点,分析表明光学设计的色差来源于其高次施密特非球面镜,提出了一种利用非球面镜的最小色差条件来改进光学系统的新方法。通过三级像差理论,分析了施密特非球面镜的面形方程,计算出最小色差条件及相应的中性带高度,进行光学设计的优化改进,取得了良好的效果。结果表明,改进后光学系统的色差由原来的31.4μm减少为4.25μm,且光学系统的MTF值达到0.6以上(40lp/mm),像质优良。该方法为类似光学系统的设计提供了一定的参考价值。     

Design of Plane-Symmetric Low <Emphasis Type="Italic">F</Emphasis>-number Reflective System Based on Perturbation Aberration Model

All-reflective optical systems have theoretically no chromatic aberration and are suitable for wide spectral application, but co-axial reflective systems are difficult to design as low F-number optical systems. In this paper, the aberration of plane-symmetric optical systems with low F-number is analyzed based on the wavefront derived from optical path length. Up to third-order aberrations are classified into three categories by their characteristics. The reduction method of the dominant aberration, astigmatism-like aberration, is proposed. In the method, the Gauss image plane is modeled by means of a simplified mirror surface with third-order approximation. Because the system is plane-symmetric, symmetric cross section and asymmetric cross section are modelled differently. The design example of a three-mirror system with F/2 is shown.     

Chromatic aberration elimination for digital rear projection television L-type lens by genetic algorithms

Following the development of a digitalized image optics system, chromatic aberration has become increasingly important especially in lateral color aberration. For rear projection television L-type lens, chromatic aberration plays the significant role because it is easily seen when facing bright screen. Basically, the elimination of axial chromatic and lateral color aberration for an optical lens depends on the choice of optical glass. DLS (damped least squares), a Ray-tracing-based method, is limited, owing to its inability to identify an enhanced optical system configuration. Genetic algorithms were applied to so-called global optimization but unfortunately so far the results show little success. Additionally, L-type optics with aspherical surface might complicate optimization due to being nonlinear response during optimization. As an alternative, this research proposes a new feasible chromatic aberration optimization process by using algorithms involving theories of geometric optics in a lens, real encoding, multiple dynamic crossover and random gene mutation techniques. In this research, rear projection television lens with aspherical surface and L-type lens are mainly discussed. Results and conclusions show that attempts to eliminate difficult axial and lateral color aberration are successful.     

Optimization of 350× optical zoom lens with diffractive optical element

Through researching and validating, a set of optical designs using a diffractive optical element (DOE) and optimization process has been derived in this paper. We put forward a set of theories to solve the numerous quality issues in imaging and applied it to an optical design. For an optical design to be successful, it must comply with the standards of the optical system. Optical designers must also take into consideration imaging quality, wherein the most influential aspects are chromatic aberration and monochromatic aberration. We complied with systemic standards such as effective focal length and total system length. Diffractive Optical Element, based on the theory of wave phase difference, takes advantage of negative Abbe number, which might significantly eliminate chromatic aberrations of optics. Following the advanced technology applied to micro lens and etching process, precisely made micro DOE element now is possible to be manufactured in a large number. A 350× zoom lens with DOE is demonstrated in the proposal. The results show that regardless of whether chromatic aberration is axial or longitudinal, issues concerning the optical lens's chromatic aberration could be significantly reduced.     

Design of a diffractive optical element for wide spectral bandwidth

A new method for eliminating the chromatic aberration of a diffractive optical element (DOE) for wideband wavelengths is presented. The wideband-wavelength diffractive optical element (WBDOE) consists of two aligned DOE's. The use of different dispersive materials for the two DOE's eliminates chromatic aberration. The design and simulation of a WBDOE for the visible spectrum are presented.     

激光靶心冲击波观测镜折反式光学系统设计

设计了一种激光靶心冲击波观测镜的光学系统.用反射式光学系统代替折射式光学系统,解决了普通玻璃在200 nm端透过率较低的问题.反射镜不引入色差,有利于系统在200~800 nm谱段消色差.为消系统轴外像差,反射系统选型为对称式.反射镜全部采用球面镜,为消反射镜以及平板玻璃窗带入的球差,引入校正镜(材料JGS1),在满足要求的条件下,控制折射镜的厚度,使系统色差满足瑞利判据的色差允差,得到了良好的成像质量.     

光学系统纵向色差的仿真及验证

现有的焦距检测方法通常由于检测仪器光源波长与光学系统不完全匹配从而产生纵向色差影响检测结果。针对这一问题,研究光学系统纵向色差的变化规律,并确定在400 nm～1 000 nm波段用于表示其函数关系的Conrady公式和复消色差特性公式。根据光学系统近焦位置的离焦量与位置呈线性关系的特性, 提出使用菲索干涉仪测量5种不同波长的焦距位置,获得单透镜和双胶合镜头的纵向色差曲线。实验结果表明: 在400 nm～1 000 nm波段单色系统和消色差系统的纵向色差的函数关系分别符合Conrady公式和复消色差特性公式,研究结果为焦距的理论计算和精确检测提供了新的思路和参考。     

Diffractive-Refractive Achromatic Lens for Optical Disk System by Glass Molding

An erasable optical disk system requires an objective lens having minimum chromatic aberration. We estimated the chromatic aberration of a conventional refractive singlet. At shorter wavelengths, the focus shift of an objective lens exceeds its depth of focus. A diffractive-refractive hybrid lens can compensate chromatic aberration perfectly. Diffraction efficiency, however, decreases with the degree of compensation. We simulated the relationship between chromatic aberration and diffraction efficiency. Fabrication of designed lenses by glass molding was achieved, and the results showed excellent agreement with the simulation.     

折衍混合单透镜的色球差校正研究

分析研究了小视场折射混合单透镜的设计中，当衍射面同时用于消色差和球差时光焦度分配的最优方案，得到了改进的光焦度分配公式，通过设计实例表明，由该改进公式可得到了较好的初始结构，能够有效地克服了衍射光学透镜校球差时产生的较大的色球差，验证了此改进公式的正确性和有效性，此改进公式对折衍混合系统的设计具有指导意义。     

Compensation for chromatic aberrations in acousto-optic systems used in spectral analysis of images

This paper considers novel optical schemes that are related to acousto-optic systems for the spectral analysis of images. The systems are characterized by a low level of transverse and longitudinal chromatic aberrations. Mathematical expressions that describe the magnitudes of the transverse aberration in various configurations of acousto-optic filters are derived. A decrease in longitudinal chromatic aberrations is examined in an optical scheme that is based on a single objective lens and an additional negative lens. A similar analysis is carried out for a confocal system that is formed of two objective lenses. The experimental investigations carried out in the visible range of the spectrum demonstrated a decrease in the longitudinal shifts of images by a factor of 2.5 and by as much as two orders of magnitude or more in the transverse image shifts.     

Designs for optimizing depth of focus and spot size for UV laser ablation

The proposed optical systems are designed for extending the depths of foci (DOF) of UV lasers, which can be exploited in the laser-ablation technologies, such as laser machining and lithography. The designed systems are commonly constructed by an optical module that has at least one aspherical surface. Two configurations of optical module, lens-only and lens-reflector, are presented with the designs of 2-lens and 1-lens-1-reflector demonstrated by commercially optical software. Compared with conventional DOF-enhanced systems, which required the chromatic aberration lenses and the light sources with multiple wavelengths, the proposed designs are adapted to the single-wavelength systems, leading to more economical and efficient systems.     

双视场红外变焦镜头的无热化研究

研究了双视场红外变焦系统的光学被动消热差技术,通过理论分析温度变化对变焦光学系统性能的影响,推导出被动消热差公式.将热离焦和热色差作为两种附加的初级像差引入像差平衡关系式,可通过常规光学系统消像差的 4 种途径:分配光焦度、有效匹配光学材料、改变透镜形状和引入非球面实现全被动补偿.在此基础上建立了一个通用模型,该系统有 6 片透镜、一个非球面,在-45℃～+55℃温度范围内的2个视场均具有较好的像质、冷反射和较宽松的公差特性.在该模型中适当引入衍射元件,可减少镜片,提高光学性能.     

Chromatic aberration of the gradient lens

Chromatic aberration of a thin solid gradient lens is analysed by means of the Hartmann dispersion relation. From the analysis it follows that it is possible to obtain optical elements with the opposite chromatic aberration to that of classical lenses. These elements may be utilised, for example, for the reduction of the chromatic aberration of classical lenses.     

基于S-L图的复消色差方法

建立了一组既消位置色差又消二级光谱的方程组,即复消色差方程组.同时引入了规化位置色差系数L和规化二级光谱系数S的概念,得到了对复消色差光学系统设计中的玻璃选择具有指导意义的S-L图.最后给出了应用这种方法进行的三片型透镜组和Petzval型透镜组的复消色差设计过程.     

二元光学器件实现含转像棱镜望远物镜像差补偿研究(英文)

以像差理论为指导分析了混合望远物镜中二元光学透镜与转像棱镜之间的像差补偿问题.计算了二元光学器件的相位系数,确定了含补偿棱镜望远物镜的初始结构.用CODE V光学设计软件对望远物镜初始结构优化后的像差结果表明:系统色差在0.9相对孔径高度得到了校正,纵向球差在容限范围0.5 mm之内,最大横向误差为-0.115 mm.     

折/衍混合单透镜在目镜中的应用研究

以传统凯涅尔目镜为基础，采用ZEMAX软件，设计了衍射面位于目镜系统中不同位置时的折／衍混合目镜系统，所有系统均仅采用最普遍的K9玻璃，设计结果与传统凯涅尔目镜的光学性能进行了分析和比较。结果表明折／衍混合目镜系统在校正目镜的像差，例如像散，垂轴色差、垂轴像差，轴向像差和轴向色差等方面优于传统的凯涅尔目镜，选择合适的衍射面位置，可以同时获得符合要求的畸变，衍射面的引入，极大地减小了系统的重量和尺寸。     

Chromatic aberration in petawatt-class lasers

In order to avoid optical damage and non-linear effects, high-power, high-energy lasers of the petawatt class like PHELIX (petawatt high-energy laser for heavy-ion experiments) use large-aperture optics. Usually, chromatic aberration associated with these optical elements is neglected. By means of numerical simulations, we show how the chromatic aberration affects the focal intensity pattern. In particular, we make quantitative predictions of how chromatic aberration decreases the focused peak intensity. Furthermore, we prove the feasibility of a new interferometer that measures the temporal pulse front distortions which arise from expansion telescopes. We also propose a scheme that pre-compensates these distortions. PACS 42.65.Re; 42.60.Jf     

Analysis of the Aberration in Directly-writing Atom Lithography

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Analysis of the Aberration in Directly-writing Atom Lithography

After deriving the approximation solution which describes the motion of neutral atoms in an optical standing wave field with large detuning, the spherical aberration and the chromatic aberration are analyzed and possible methods to reduce these aberrations are discussed.