Aberration athermal design for infrared search and trace optical system

To satisfy environment requirement of infrared search and trace optical system, an infrared diffractive/refractive hybrid optical system in 3.7–4.8 μm with 11.42° of field of view for passive athermalization is presented. The system is consisted of three lenses, including two aspheric surfaces and a diffraction surface, which has only two materials Ge and Si. The optical system has compact structure, small volume and light weight. The image quality of the system approaches the diffraction limit in the temperature range −80 °C to 160 °C. It is compatible with staring focal plane array which has a format of 320 × 240 and the pixel pitch of 30 μm. The system need not move the compensated lens repeatedly to obtain the best images from −80 °C to 160 °C and enhances the performance of target tracking and recognition.     

Design of midwave infrared athermalization optical system with a large focal plane array

Based on the most advanced staring focal plane array which had a format of 640 × 480 and the pixel pitch of 15 μm, a set of all-sphere midwave infrared ahermalization optical system was designed. The working wavelength was in 3–5 μm, the full field of view was 8.58°, the relative aperture was 1/2, the efficient focal length (EFL) was 80 m. The opticalsystem consisted of four lenses with three kinds of material – Ge, ZnSe and Si. All surfaces were sphere, which was easier to process test, making the cost inexpensive, and it could avoid using diffractive surface and aspheric surface. The image quality of the system approaches the diffraction limit in the temperature range −60 °C-180 °C. The design results proved that, the high resolution midwave infrared optical system had compact structure, small volume, high resolution and excellent image quality, meeting the design requirements, so that it could be used for photoelectric detection and tracking system.     

Aberrations of plane-symmetric multi-element optical systems

Based on a recently developed aberration theory of plane-symmetric grating systems, its aberration coefficients are firstly extended to be applicable to the plane-symmetric refractive optical surface. To justify the linear approximation of aperture ray in a multi-element system, the ray aberrations of double-element systems with the third-order accuracy of aperture ray are derived and expressed as the form of wave aberrations. The numerical comparisons are then made between the ray tracing, the aberration expressions with the linear and with third-order accuracy of the aperture ray. Moreover, the modifications of the wave and ray aberrations are discussed in the paper when the position of the principal ray changes.     

Study on the optical path difference of aero-optical window

To study the optical path difference (OPD) of optical widow in which light beams transmit under the aerodynamic thermal environment, a grid model is introduced. Based on it, the aero-optical effect of the side-mounted window is analyzed in detail combining the optical transmission theory and the numerical simulation method. Firstly, the temperature and stress of the window are simulated, and then the OPD is obtained through the refractive index. To demonstrate it, temperature field, deformation field and stress field of the window are calculated and analyzed. The influences of thermal shock and atmosphere pressure on the OPD are discussed.     

共形光学设计研究

符合空气动力学的导引头整流罩都是流线型的面型,由于这些面型破坏了光学系统的对称性,与导引头成像光学配合时会带来严重的像差,使成像质量下降。所谓共形光学设计就是在整流罩和成像光学系统之间加入校正系统,用校正系统校正整流罩所带来的像差,以便获得良好的成像质量。介绍了共形光学设计的概念,讨论了设计原理,分析了热变形的影响,并给出了一个设计实例。     

气动热环境下高速飞行器光学头罩特性分析

建立高速飞行器红外光学头罩在气动热环境下有限元分析模型,分析头罩在气动热环境下的物理特性和光学特性,对头罩在气动热环境下的温度场、应力场、应变场和位移场进行数值计算。计算结果表明头罩在气动热环境下温度场分布不均匀,因此头罩会产生热应力而发生形变。利用有限元分析结果,根据热光效应和弹光效应理论,对气动热环境下红外光学头罩的折射率场进行数值计算。以头罩外表面中心点折射率为例,在头罩工作时间内,通过计算得到头罩15s后由热光效应造成的折射率改变为0.011,而由弹光效应造成的x方向折射率改变为0.000107,即弹光效应造成的折射率改变量约为热光效应造成折射率改变量的0.97%,由此可知,在气动热环境下热光效应对头罩折射率的影响比较大,而弹光效应对头罩折射率的影响比较小。     

硫系玻璃在现代红外热成像系统中的应用

介绍了硫系红外玻璃的组成成分,分析了其独特的优势,建立了红外热成像系统中各个参数和温度之间关系的数学模型。基于硫系玻璃折射率温度系数小、成本低的优点,将硫系玻璃应用于红外热成像探测系统,并给出了一种折射式的中波红外热成像消热差探测系统实例,评价结果表明,该系统在低温-40 ℃、常温20 ℃、高温60 ℃都取得了良好的成像质量,适用于像元数为320 pixel×256 pixel,像元尺寸为30 μm×30 μm的中波红外凝视型焦平面阵列探测器。     

Correcting dynamic residual aberrations of conformal optical systems using AO technology

This paper analyses the dynamic residual aberrations of a conformal optical system and introduces adaptive optics (AO) correction technology to this system. The image sharpening AO system is chosen as the correction scheme. Communication between MATLAB and Code V is established via ActiveX technique in computer simulation. The SPGD algorithm is operated at seven zoom positions to calculate the optimized surface shape of the deformable mirror. After comparison of performance of the corrected system with the baseline system, AO technology is proved to be a good way of correcting the dynamic residual aberration in conformal optical design.     

自由热射流流场的光学不均匀性数值研究

 通过建立物理模型，求解层流N-S方程，用数值方法模拟了二维热射流流场的有序大涡结构，计算了流场不同流向位置的光程值，分析了射流流场混合层的光学特性，得出了气动光学流场由于流场中大尺度涡结构的存在所引起的光学不均匀性，大涡结构中奇点所导致的光学畸变最大，在一定条件下大涡结构有散焦作用。     

光学系统的等效变换

本文在普遍情况下使用矩阵方法详细讨论了光学系统的等效变换,证明光线变换矩阵为的光学系统当C≠0时可等效为一个薄透镜,当C=0时等效为一个薄透镜组。文中所得结果能用于分析光线或光束通过复杂光学系统的变换和多元件光腔的问题。     

用于接触式探测的多模光纤探针形状优化

对于进行接触式探测的多模光纤探针,信号光来自于附着于探针表面的待测物。基于几何光学,提出了一个物理模型,用以分析探头形状对所收集的信号光强度的影响。采用此模型,对抛物线型探头进行了仿真,给出了最优形状参数,并采用表面增强拉曼探针进行了初步实验验证。此分析可用于指导各种光纤传感器的设计,以确定其最佳的形状参数,适用于荧光传感器、表面等离子体共振传感器、表面增强拉曼传感器等。     

Alternating approach of implementing frequency encoded all-optical logic gates and flip-flop using semiconductor optical amplifier

In conduction of parallel logic, arithmetic and algebraic operations, optics has already proved its successful role. Since last few decades a number of established methods on optical data processing were proposed and to implement such processors different data encoding/decoding techniques have also been reported. Currently frequency encoding technique is found be a promising as well as a faithful mechanism for the conversion of all-optical processing as the frequency of light remains unaltered after refection, refraction, absorption, etc. during the transmission of light. There are already proposed some frequency encoded optical logic gates. In this communication the authors propose a new and different concept of frequency encoded optical logic gates and optical flip-flop using the non-linear function of semiconductor optical amplifier.     

Two-dimensional optical micro-scanner on silicon technology

A two-dimensional optical micro-scanner, which main components are two mobile flat and a concave micro-mirrors, is designed such that, all optical components can be fabricated on the same substratum. The optical parameters, which physical dimensions are between 50 and 500 μm, are obtained within the geometrical optics. The optical performance is evaluated by means of the MTF and Rayleigh resolution criteria, given 80% of modulation for a frequency of 8 cycles/mm with a Gaussian source, the resolution limit is 30 μm.     

Robust optical systems for nondestructive testing based on laser diodes and diffractiveoptical elements

Two robust systems for vibration measurements are presented. Both systems are based on low-cost laser diodes. The stability of the optical systems is achieved by implementing the optical system as a holographic optical element (HOE) while using a common-path interferometer concept for the measurement scheme. The former system facilitates real-time simultaneous tracking of vibrations about two axes perpendicular to the optical axis. The latter system is an electronic speckle interferometer working in a differential mode providing whole-field information on the angular deformation about one axis between two states of the object. It will be argued that these concepts will provide compact, self-aligning systems for industrial use due to the inherent possibility of mass fabrication.     

A new alternative approach of all optical frequency encoded clocked S-R flip-flop exploiting the non-linear character of semiconductor optical amplifiers

In all optical networking and computing system, the role of all-optical flip-flops is very much essential. For signal synchronization with a reference clock and for storage of digital bits the flip-flop has no alternative. In this communication the authors propose a method of developing an all optical frequency encoded clocked R-S flip-flop using the non-linear character of semiconductor optical amplifiers. Frequency is the basic character of light and several encoding/decoding problems in computations and communications can be solved using the frequency encoding principle of optical data. The proposed system is all-optical and therefore it can extend a super fast speed of operation (far above THz limit).     

基于共焦法透镜中心厚度检测的光学系统设计

光学透镜的中心厚度是光学系统中的一个重要参数,其加工质量的好坏对光学系统的成像质量具有很大的影响。提出了一种基于共焦原理的非接触在线检测技术。系统的测量范围可达到9.8mm,测量精度可达到14.7μm。     

Exploring fabrication tolerances of optical systems by solving inequalities

A scheme to study fabrication tolerances of optical components and systems is presented. By solving a set of non-linear inequalities an optimal set of lens parameters is found. Then, by selecting another, but strict, set of boundaries to the non-linear inequalities system, a new set of lens parameters is found. The fabrication tolerances are determined by the intersection domain of each lens parameters obtained by solving the set of non-linear equations, with a condition that one solution should come from a strict set on boundaries of the non-linear equation system. This scheme is applied to a classical triplet lens system, used as starting point, and is compacted in effective and back focuses lengths, showing the versatility to study the fabrication tolerances.     

Optical wave breaking of high-intensity femtosecond pulses in silicon optical waveguides

We have investigated numerically the propagation of high-intensity femtosecond optical pulses with pulsewidth of 100 fs (half width at 1/e maximum) on the silicon-on-insulator (SOI) optical waveguide when the central wavelength of the pulse locates in the normal dispersion region. Results show that the combined effects of group-velocity dispersion (GVD), third-order dispersion (TOD), self-phase modulation (SPM), and free-carrier dispersion (FCD) can lead to the phenomenon of optical wave breaking that manifests as an asymmetric profile and oscillation near the trailing edge of the pulse. Moreover, the optical wave breaking will be experienced from generation to disappearance during propagation.     

Infrared radiative properties of two-dimensional square optical black holes

Optical black hole (OBH) is a special optical structure, in which the dielectric function or refractive index of media becomes gradually larger from the outside to the core. The circular optical black holes (COBH) have been proved remarkably useful for broadband omnidirectional light absorption. The main goal of this paper is to propose an alternative square structure of OBH due to fabrication consideration. The infrared radiative properties of two-dimensional SOBHs are numerically studied with geometric optics approximation (GOA) and the finite-difference time-domain (FDTD) method. A critical wavelength is found in this paper: when the wavelength is smaller than half of the inner core side length, the Poynting vectors obtained by the FDTD method agree well with the ray trajectories calculated by the GOA, and the absorptance is nearly 100% with a proper refractive index gradient. While the wavelength is increasing, the net energy flows do not agree with the ray trajectories and the absorptance will be decreased. The reason is attributed to the diffraction effect, which is discussed in detail in this paper.     

Analysis of materials selected for multilayer diffractive optical elements

An analysis model to optimize the materials selected for multilayer diffractive elements (MLDOEs) is presented with approximate Cauchy dispersion formula of refractive index and the maximum polychromatic integral diffraction efficiency (PIDE). The analysis model presents that the maximum PIDE of MLDOEs consisting of two materials with large Abbe number difference and small partial dispersion difference can be generated. The scope of application and the relationship between diffraction efficiencies of MLDOEs with different material pairs and different design wavelength pairs are presented and simulated with the analysis model of MLDOEs.