利用光纤和调制半导体激光的准直方法

本提出了一种新的激光光纤准直方法。利用光传播的平行性和直线性，光学准直技术被用于精密地建立几何参数的测量基准，在这些应用中，光束、处理电路的漂移、杂散光是影响测量精度的主要因素。为了消除这些影响，本利用调制半导体激光技术和光纤技术形成准直光束，四象限探测器进行探测，相敏检波技术对光电调制信号进行解调，所有的信号共享同一信号处理信道，且光束的调制频率远离杂散光的频率范围，激光光束漂移杂散光、电路漂移被抑制，在１ｍ范围获得了０．３μｍ的准直精度。     

Determination of Thermal-Diffusivity Dependence on Temperature of Transparent Samples by Thermal Wave Method

The use of a typical measuring cryostat with a standard temperature controller was proposed for investigation of the temperature dependence of the thermal diffusivity of transparent samples. The basic idea is to use the cryostat heater to control the mean sample temperature and to generate the thermal wave in it, simultaneously. Because of the relatively high thermal inertia of the system, the measurements are carried out at frequencies not exceeding 50 mHz. The periodic temperature disturbance in the sample was detected optically by the use of the mirage effect. The proposed method was used for determination of the thermal diffusivity of yttrium aluminum garnet single crystals in a temperature range from 20 °C to 200 °C.     

光学元件聚氨酯抛光特性研究

本文研究了应用于平面光学元件的快速抛光技术,从材料去除率、元件面形和表面粗糙度出发,对快速抛光技术应用于平面大口径元件的加工效果进行了探讨。研究了在快速抛光技术中压力和主轴转速对材料去除率的影响,验证了Preston公式在快速抛光中的适用性,快速抛光技术的去除效率可达10μm/h;其次,研究了聚氨酯抛光元件面形的精度,对于330mm×330mm元件可达～1.0λ（λ=632.8nm）;最后,对快速抛光系统中抛光粉颗粒大小及形态随使用时间的变化进行了观测,并测量了使用300目和500目抛光粉时快速抛光元件表面粗糙度以及其随抛光粉使用时间的变化。     

高性能大型金属构件激光增材制造技术研究现状与发展趋势

高性能大型金属构件激光增材制造技术,将"高性能金属激光熔化/快速凝固材料制备"与"大型构件近净成形制造"结合,为航空、航天、船舶、电力、石化、海洋工程等高端装备中大型难加工金属构件的制造提供了新途径。综述了北京航空航天大学大型金属构件增材制造国家工程实验室在钛合金等高性能大型关键承力构件激光熔化沉积增材制造技术方向的主要进展:突破以"凝固晶粒"、"内部缺陷"及"显微组织"为核心的钛合金大型关键主承力构件激光增材制造"质量性能"控制瓶颈难题;提出系列激光增材制造工艺新方法,揭示激光增材制造过程内应力形成机理与演化规律,初步建立"变形开裂"预防方法;研制出具有原创核心关键技术的系列化大型激光增材制造工程化成套装备;自主制定了整套应用技术标准体系。北航团队研究成果在国家大型运输机、舰载机、大型运载火箭等重大装备研制生产中的工程应用,为解决装备研制生产制造瓶颈难题、提升装备结构设计制造水平、促进装备快速研制等发挥了重要作用,同时使我国在此领域处于国际领先地位。     

激光照排技术与激光照排机

本文系统地阐述了激光照排技术的基本原理和发展概况，以及各种激光照排机的结构和性能特点。     

激光照排技术与激光照排机

本文系统地阐述了激光照排技术的基本原理和发展概况,以及各种激光照排机的结构和性能特点.     

飞秒激光及光钟

结合飞秒激光超强、超快、超稳、宽频、广谱、相干的特点,介绍了其相应的技术应用情况:应用超快特性的微观物理、生物、化学、信息、通信等;以超强应用为对象的材料加工、制备、电子对撞加速器、受控核聚变等;以超稳特性应用为对象的光频测量、长距离测量、光钟等,并简介了光钟。     

International Comparison on Thermal-Diffusivity Measurements for Iron and Isotropic Graphite Using the Laser Flash Method in CCT-WG9

The first international pilot study of thermal-diffusivity measurements using the laser flash (LF) method was organized by the working group 9 (WG9) of the Consultative Committee for Thermometry (CCT) of the Bureau International des Poids et Mesures (BIPM). Four National Metrology Institutes (NMIs) participated in this comparison. Thermal-diffusivity measurements on the Armco iron and the isotropic graphite IG-110 were carried out from room temperature to about 1200 K. The sample sets consist of five disk-shaped specimens of 10 mm in diameter and (1.0, 1.4, 2.0, 2.8, and 4.0) mm in thickness, each cut from the same block of material. These sample sets were specifically prepared for the comparison and sent to the participants. In the pilot comparison, the thermal diffusivity of each sample was estimated using the LF method with a specific extrapolating procedure. This procedure has the advantage of determining the inherent thermal diffusivity of the material. The extrapolated value in a plot of measured apparent thermal-diffusivity values versus the amplitude of the output signal corresponding to the temperature rise during each measurement is defined as the inherent thermal diffusivity. The overall results showed good agreement between independent laboratories, measurement equipment, and specimen thicknesses. The thermal diffusivities of the materials were determined using our measured results. A quantitative evaluation of the variability of the data obtained by the participants has been done, by evaluating the deviations from the reference value, the Z-value, and the En-number. Some data showed a large deviation from the reference value. It was concluded that these are caused by an insufficient time response of the measurement equipment and some difficulties with changing the pulsed heating energy. The effect of the thermal expansion on the thermal diffusivity was checked. It was found that the thermal-expansion effect was very small and negligible in this case.     

Thermal-Diffusivity Measurement of Ceramic Coatings at High Temperature using “Front-Face” and “Rear-Face” Laser Flash Methods

Thick ceramic coatings deposited by plasma spraying techniques are widely used as wear and corrosion resistant coatings at high temperature. To measure accurately the thermal diffusivity of such coatings, the diffusivimeter of LNE has been set up to allow multilayered material studies up to 1,400°C by rear-face and front-face laser flash methods. These two methods have been compared in a large temperature range by measuring the thermal diffusivity of homogeneous (Armco iron and Poco graphite) and multilayered materials (chromium oxide coating deposited on iron alloy substrate). The thermal-diffusivity values measured by using front-face and rear-face techniques are in good agreement, with a relative deviation of less than 5% depending on temperature and materials.     

同步辐射活化氧清洗光学元件研究

利用自行研制的真空清洗装置连接到同步辐射光束线上开展了同步辐射光活化氧清洗碳污染光学元件的研究.引入同步辐射光到冲入氧气的清洗真空室,使氧气电离而生成臭氧.臭氧具有很强的氧化性.光学元件表面的碳污染物在同步辐射光和臭氧的共同作用下,发生化学反应,生成CO2等气态物质.CO2等通过真空泵抽除,进而达到清洗的目的.文中给出了实验结果.     

微结构光学元件的应用与制造

介绍了微结构光学元件在很多领域的应用,比如军事、医药生物研究及其他民用行业等,这种微结构光学元件为光学设计者与制造者提供了更多的自由度,讨论了微结构光学元件的多种制造方法,包括光刻技术、LIGA技术、模压成型技术、注射成型技术、热压成型技术以及金刚石机械加工技术,每种方法在加工精度、效率以及是否适合加工大深宽比结构等方面都有其自身的优点与缺点,将各种复制技术与机械加工技术结合起来,是将来的发展方向。     

Conventional Simultaneous Measurement of Specific Heat Capacity and Thermal Conductivity by Thermal Radiation Calorimetry

Thermal radiation calorimetry has been applied to measure the thermal conductivity and the specific heat capacity of an isolated solid specimen simultaneously. The system, in which a disk-shaped specimen and a flat heater are mounted in a vacuum chamber with the specimen heated on one face by irradiation, is presented. A theoretical formulation of the simultaneous measurement at quasi-steady state is described in detail. Noncontact temperature measurement of both specimen surfaces has been performed using pyrometers and a thermocouple set in the gap between the heater and the specimen. Pyroceram 9609 specimens, whose surfaces were blackened with colloidal graphite, were used in the measurement. The largest error involved in the noncontact temperature measurement is ±2°C in the range from 450 to 650°C. The resultant values of the specific heat capacity and the thermal conductivity deviate by about 10% from the recommended values for the Pyroceram specimen.     

Determination of Particle Size Distribution of Zirconium Dioxide Powders by Static Laser Scattering and Optical Microscopy

Dispersing conditions of powdered zirconium dioxide with addition of 3 mol % yttrium oxide are determined. The particle size distribution of the powders is determined by static laser scattering and optical microscopy. The zeta potential of suspension of zirconium dioxide particles as a function of pH of medium is measured by electrophoresis with titration. The influence of acidity on suspension stability during measurements is studied. It is demonstrated that a stable suspension can be obtained by shift of pH to both the acid and alkaline regions as well as by addition of surfactants, such as Dolapix CE 64.     

Thermophysical and Thermal Optical Properties of Vanadium by Millisecond Calorimetry Between 300 and 1900 K

A variant of millisecond-resolution pulse calorimetry in use at the Institute of Nuclear Sciences Vina since 1983 involves measuring the specific heat and electrical resistivity of electrical conductors from room temperature to 2500 K and the hemispherical total emissivity and normal spectral emissivity from about 1300 K to the same maximum operating temperature. The method was applied successfully to different materials: pure metals, ferrous and nickel-base alloys, reactor materials, and refractory metals in thermal characterization of candidates for thermophysical property standard reference materials. This paper presents and discusses new data obtained in the study of thermophysical and thermal optical properties of vanadium.