红外导引头光学系统设计

根据红外导引头技术指标要求,选择光学系统的结构形式,初步确定光学系统的几何尺寸;以作用距离最大、系统双波段像差最小以及工艺要求最低为目标,利用开发的导引头光学系统通用设计软件进行光学系统参数优化。获得的光学系统在±20°的动态视场中弥散斑直径均小于0.15mm,导引头在给定条件下估算的作用距离达到39km。     

Freeform lens arrays for off-axis illumination in an optical lithography system

We propose a method of designing a freeform lens array for off-axis illumination (OAI) in optical lithography to produce desired OAI patterns and improve efficiency. Based on the Snell law and the conservation law of energy, a set of first-order partial differential equations are derived and the coordinate relations for each OAI pattern are established. The contours of the freeform lens unit are calculated numerically by solving the partial differential equations, and the freeform lens array is obtained by arraying the lens units. Moreover, the optical performance for each OAI pattern is simulated and analyzed by software. Simulation results show that the irradiance distribution of each OAI pattern can be well controlled with a maximum uniformity of 92.45% and a maximum efficiency of 99.35%. Also, analysis indicates that this method has the advantages of reducing the complexity of the exposure system and having good tolerance to the input intensity variations of the laser beam.     

超广角光学镜头畸变的约束最小二乘优化

在普通最小二乘算法的基础上,根据短焦距、超广角光学镜头的实际特性,在线性回归方程组中添加约束条件,并借助 MATLAB Optimization 工具箱求得拟合的结果。计算结果表明, 该方法减小了测量误差对计算结果的影响,改善了畸变随视场的分布,使计算结果更加合理。     

Computer-aided design,manufacturing and inspection system integration for optical lens production

The main objectives of this research are the development of an integrated manufacturing strategy and the construction of a database management system for the design, machining and inspection of sculptured surfaces. Specifically, the optical lens for colour display tube/colour picture tube is selected as an application example to show the effectiveness and efficiency of the developed manufacturing strategy and database construction methods. In the machining strategy, the total machining time reduction method is proposed for the rough cutting operation based on the optimum tool path planning. In the finish cutting operation, a modified cutter contact variable step method is employed, and optimal tool paths are generated by selecting the proper tool radius within the given tolerance of a designed model. In the inspection strategy, the shortest measuring path is calculated to reduce the inspection time in CMM. In addition, an efficient database management system, which conducts the process from the surface design stage to the inspection result analysis stage, is constructed for the optimization of the sculptured surface manufacturing process. Finally, the required simulation and experimental works are carried out to verify the proposed strategy.     

Use of a field lens for improving the overlap function of a lidar system employing an optical fiber in the receiver assembly

This paper presents a method to compute the overlap function of a lidar system in which a step-index optical fiber (or a bundle of such fibers) is used to carry the light collected by the telescope to the photoreceiver and a field lens is placed between the telescope and the optical fiber to increase the receiver field of view (FOV). The use of field lenses is a classical way to increase the FOV of radiometric systems (such as the receiving part of a lidar) when there is no numerical aperture (NA) limitation after the lens. However, when such a limitation exists, as in the case studied here, it will place a limit on the maximum attainable FOV. In the case of lidars, which have range-resolution capabilities, the limited FOV has an effect on the fraction of power coming from scattering volumes at different ranges that actually reaches the photodetector. This fraction is a function (the so-called overlap function) of the range of the scattering volume and its behavior has an impact on the accuracy of the retrievals. The application of the method developed in this paper shows that, in spite of the fiber NA limit, in practical situations the goal is attained of making the overlap function steeper and reaching higher values by using a field lens.     

Test and analysis of an electro-optic dynamic diverging lens for three-dimensional optical memories

We present the experimental results of a two-dimensional electro-optic dynamic diverging lens for dynamic imaging. The device is based on a lanthanum-modified lead zirconate titanate ceramic wafer. It produces a smooth phase-modulation distribution, which almost eliminates the diffraction loss of interdigital electrodes and the interference among different diffraction orders that exist in most of these types of devices. The continual change of focal length in this device is achieved by an applied control voltage. A dynamic-imaging system is demonstrated. It can be used to address three-dimensional optical memories. The aberration of the device as compared with an ideal lens is also numerically evaluated. With minor modification to the applied voltage distribution on the device, its performance is comparable with that of an ideal lens.     

Micromachined optical concentrators for IR negative luminescent devices

Negative luminescent (NL) devices, which to an IR observer appear colder than they actually are, have a wide range of possible applications, including use as thermal radiation shields in IR cameras, and as IR sources in gas-sensing systems. For many of these applications a large area (>1 cm²) device which displays as large as possible apparent temperature range is required. However, under reverse bias, significant currents are required to reduce the carrier concentrations to the levels needed for maximum possible absorption. We have therefore used a novel micromachining technique to fabricate integrated optical concentrators in InSb/InAlSb and HgCdTe NL devices. Smaller area diodes can then be used to achieve the same absorption (e.g. for InSb an area reduction of 16 is possible) and the required currents are thus reduced. To fabricate the concentrators, spherical resist masks are first produced, which are ～10 μm high and ～53 μm wide, by resist reflow at 120°C. Inductively coupled plasma (ICP) etching is then used to etch alternately the resist mask and the semiconductor, with oxygen and methane/hydrogen respectively, producing concentrators with almost parabolic profiles. Currently, the concentrators are typically 30 μm high, with a top diameter of ～15 μm. Continuing optimization of the process to reach the theoretical limits of optical gain is described.     

New coating materials for IR laser optical components

Concepts of reactive atmosphere processing are applied to the preparation, purification, and thermal characterization of three rare-earth fluorides (LaF₃, CeF₃, and PrF₃) and BiF₃, BiI₃, and KGaF₄. The rare-earth fluorides have optical absorption coefficients between 0.6 and 0.9 cm^?1 at 9.27 μm; of the rare-earth fluorides, only LaF₃ is a good coating material at 3.8 μm. BiF₃ and KGaF₄ appear to have low absorption at 9.27 μm and 3.8 μm. BiI₃ shows a flat response between 2.5 and 20 μm.     

Quasi-null lens optical system for the fabrication of an oblate convex ellipsoidal mirror: application to the Wide Angle Camera of the Rosetta space mission

The design of a quasi-null lens system for the fabrication of an aspheric oblate convex ellipsoidal mirror is presented. The Performance and tolerance of the system have been analyzed. The system has been applied successfully for the fabrication of the primary mirror of the Wide Angle Camera (WAC), the imaging system onboard the Rosetta, the European Space Agency cornerstone mission dedicated to the exploration of a comet. The WAC is based on an off-axis two-mirror configuration, in which the primary mirror is an oblate convex ellipsoid with a significant conic constant.     

Reconfigurable lens with an electro-optical learning system

An electro-optical system is proposed to control a reconfigurable lens that is a combination of a physical lens and a two-dimensional liquid-crystal phase modulator. The functions of an imaging system employing the reconfigurable lens can be controlled by a change in the phase distribution of the modulator. A computer changes the phase distribution and evaluates the image of an optical system. This process is iteratively performed on the basis of the simulated-annealing algorithm to optimize the phase distribution. We demonstrate control of a point-spread function and the correction of imaging properties degraded by defocusing or phase objects. The corrected imaging properties are even better than the original ones.     

Designing an optical disk lens without analytical definition of aspheric surfaces

We have developed a new method to design aspheric lenses. The conventional technique is usually based on analytic definition of optical surfaces; in the new method discretely defined aspheres are used, and the final design is attained point by point with an iterative algorithm. Simulation results are compared with results obtained with conventional optical design software to prove that this new method is more effective and reliable for designing aspheric lenses, especially when the aspheric order is high.     

行进间坦克火炮身管弯曲测量系统

针对坦克行进间火炮身管弯曲测量缺乏手段,评估其对射击准确度的影响缺乏数据的现状,在综合分析现有身管弯曲测量方法的基础上,提出炮尾安装高分辨率和高帧频线阵CCD、炮口固定指示标靶的基于计算机视觉的测量方案,论述系统组成、测量原理和测量准确度,分析测量距离、CCD成像系统姿态等装配问题对测量准确度的影响。结果表明:该方案在实现实时高准确度身管弯曲测量的同时,解决测量系统在进行高速高准确度测量时数据量大、存储和处理难的问题;实现系统的自标定,降低系统的装配准确度要求,提高系统的实用性,具有一定的创新性和现实意义。     

A super-oscillatory lens optical microscope for subwavelength imaging

The past decade has seen an intensive effort to achieve optical imaging resolution beyond the diffraction limit. Apart from the Pendry-Veselago negative index superlens, implementation of which in optics faces challenges of losses and as yet unattainable fabrication finesse, other super-resolution approaches necessitate the lens either to be in the near proximity of the object or manufactured on it, or work only for a narrow class of samples, such as intensely luminescent or sparse objects. Here we report a new super-resolution microscope for optical imaging that beats the diffraction limit of conventional instruments and the recently demonstrated near-field optical superlens and hyperlens. This non-invasive subwavelength imaging paradigm uses a binary amplitude mask for direct focusing of laser light into a subwavelength spot in the post-evanescent field by precisely tailoring the interference of a large number of beams diffracted from a nanostructured mask. The new technology, which--in principle--has no physical limits on resolution, could be universally used for imaging at any wavelength and does not depend on the luminescence of the object, which can be tens of micrometres away from the mask. It has been implemented as a straightforward modification of a conventional microscope showing resolution better than λ/6.     

Effect of heterophase inclusions on the optical losses in high-purity IR optical materials

Using a tungstate-tellurite glass and high-purity zinc sulfide—promising IR optical materials—as test systems, we have developed an approach for evaluating the limits of the sensitivity of optical losses to the presence of heterophase impurity inclusions and second-phase inclusions differing in chemical nature and size. We have calculated the volume fraction of disperse phases and concentration of inclusions which ensure optical losses in these materials below a predetermined level.     

Experimental demonstration of an automatic alignment system for optical interferometers

An automatic alignment system, based on a differential phase-sensing technique described in a companion paper [Appl. Opt.33, 0000, (1994)], has been experimentally demonstrated on the 10-m prototype laser interferometric gravitational wave detector in Glasgow. The alignment system developed was used to control the orientations of two mirrors in a 10-m-long suspended Fabry-Perot cavity with respect to the direction defined by the input laser beam. The results of the test and a discussion of the performance of the system are given.     

Technique of microball lens formation for efficient optical coupling

A batch-fabricated microball lens array not only provides accurate coupling distances but also replaces traditional components such as aspheric lenses and expensive graded-index lenses without sacrificing performance and reduces assembly cost. The results of extensive experiments show a critical aspect ratio of approximately 0.3. That is, when the aspect ratio is larger than 0.3, the final shape of a reflowed lens changes to that of a microball rather than of a mushroom. Using a laser with a 633-nm wavelength yields an optimum coupling distance of approximately 8 microm with an insertion loss below -1.3 dB (coupling efficiency, approximately 73%).     

Photorefractive real-time phase-coded optical correlation storage using a crossed cylindrical-collimating lens system

Phase-coded optical correlation storage in photorefractive crystals, using a crossed cylindrical-collimating lens system, has been realized. It possesses the advantages of both storage and correlator. It can perform real time and fast selection of the information correlated to the input information from a great amount of stored information. In Zn:Fe:LiNbO(3)(0.03 wt. % Fe, 3 mol. % Zn), combining this rotational phase-coded multiplexing with angular multiplexing, 36 holograms have been successfully multiplexed and exactly identified in the same crystal volume. The cross talk and angular selectivity of such phase-coded multiplexing are discussed.