单片机在激光测径中的应用

本文介绍了８０９８单片机在激光测径系统中应用的情况，给出了这一系统的硬件、软件结构以及实验结果．     

Importance Sampling and Mean-Square Error in Neural Detector Training

This letter deals with the use of Importance Sampling (IS) techniques and the Mean-Square (MS) error in neural network training, for applications to detection in communication systems. Topics such as modifications of the MS objective function, optimal and suboptimal IS probability density functions, and adaptive importance sampling are presented. A genetic algorithm was used for the neural network training, having considered adaptive IS techniques for improving MS error estimations in each iteration of the training. Also, some experimental results of the training process are shown in this letter. Finally, we point out that the mean-square error (estimated by importance sampling) attains quasi-optimum training in the sense of minimum error probability (or minimum misclassification error).     

A laser sensor with multiple detectors for freeform surface digitization

In this paper, an integrated laser scanning sensor for freeform surface digitization is presented. The sensor consists of a diode laser light source and four position-sensitive device (PSD) detectors. The stand-off distance of the sensor is 180 mm and the measurable range is 90 mm. The Lambert model is applied to calculate the displacement between the sensor and the measured point on the object surface along the optical axis, under the assumption of a diffusive surface. The inclination angle of the measured point from the vertical plane of the laser beam is calculated by mathematical inference. Those data are used in error compensation to improve the system precision. The new design of multiple detectors could increase the measurable angle and could solve the dead-space problem in the single-point laser of triangulation measurement. The computer simulation and actual measurements show that the displacement resolution is around 50 μm, and the system performs well in terms of stability and repeatability. The sensor system could be mounted on the NC machine or on the X–Y platform for freeform surface digitization.     

高性能ZnS为基的紫外线检测器的技术回顾

对波长短于400 nm的紫外线有高灵敏度的探测器,在一些要求很高的可见光及红外线背景下作紫外线探测的应用是非常重要的.它们能在工业设备、科学研究以及消费产品开发新应用,例如火焰监控、光刻技术、 紫外线天文学、各种各样的先进医学和生物学仪器以及多种用于个人的紫外线监控产品.最近,我们已成功开发2种Ⅱ-Ⅵ族紫外线探测器：它们分别是以ZnSSe及ZnMgS为基的检测器.它们已经在商品化阶段.投产的商品包括紫外手表、个人紫外线监测器、新概念玩具和应用于教育部门的紫外线指数仪表及紫外线透射测试仪.这份报告会对这些新型器件作出详细的技术回顾.讨论集中于最近的研究成果：(1)萧特基(schottky)金属的问题、(2)防反射镀薄层以及(3)噪音和灵敏度检测.我们已制备并探讨了Au/Ni和Au/Cr双层萧特基接触.研究结果显示这些器件的光响应曲线相对于用纯Au作萧特基接触的器件,具有较低的抗可见光能力.利用二次离子质谱(SIMS)分析技术,发现Ni和Cr在Ⅰ～Ⅵ族材料中有严重的扩散以及它们在蒸镀过程中较易氧化.而且,也发现Au/Cr接触有金属合金现象.提出了一个考虑到由金属扩散及合金产生缺陷态的模型.相信这些缺陷态通过光激发及隧穿机制,严重地影响了在可见光频谱的光响应.我们的原本器件已经拥有高达60％的外部量子效率,但仍然受限于由于反射而导致的损失.在这项报告中,将讨论利用单层和多层防反射镀薄层的最新成果,也会探讨器件系统的灵敏度.我们已测量了器件的嗓音频谱密度、响应时间、频宽、光响应、在反向偏压下的暗电流及零偏压下的电阻.高达1014cm Hz1/2W-1的灵敏度已经达到.这些结果显示我们研制的新型紫外线探测器也适合于多种高档的应用,例如火焰传感器和紫外线照像机.     

Topographic and material contrast in low-voltage scanning electron microscopy

Two scintillation backscattered electron (BSE) detectors with a high voltage applied to scintillators were built and tested in a field emission scanning electron microscope (SEM) at low primary beam energies. One detector collects BSE emitted at low take-off angles, the second at high takeoff angles. The low take-off detector gives good topographic tilt contrast, stronger than in the case of the secondary electron (SE) detection and less sensitive to the presence of contamination layers on the surface. The high take-off detector is less sensitive to the topography and can be used for detection of material contrast, but the contrast becomes equivocal at the beam energy of 1 keV or lower.     

An Ultrahigh Responsivity (9.7 mA W−1) Self‐Powered Solar‐Blind Photodetector Based on Individual ZnO–Ga2O3 Heterostructures

Highly crystallized ZnO–Ga₂O₃ core–shell heterostructure microwire is synthesized by a simple one‐step chemical vapor deposition method, and constructed into a self‐powered solar‐blind (200–280 nm) photodetector with a sharp cutoff wavelength at 266 nm. The device shows an ultrahigh responsivity (9.7 mA W^?1) at 251 nm with a high UV/visible rejection ratio (R _{251 nm}/R _{400 nm}) of 6.9 × 10² under zero bias. The self‐powered device has a fast response speed with rise time shorter than 100 µs and decay time of 900 µs, respectively. The ultrahigh responsivity, high UV/visible rejection ratio, and fast response speed make it highly suitable in practical self‐powered solar‐blind detection. Additinoally, this microstructure heterojunction design method would provide a new approach to realize the high‐performance self‐powered photodetectors.     

632 nm激光对CCD干扰效果仿真与实验研究

为解释激光对CCD探测器的干扰机理,建立了激光辐照CCD探测器的有限元仿真模型。利用波长为632 nm的激光对CCD探测器进行干扰实验,通过图像处理的方法得到了光功率与饱和干扰面积的关系曲线。建立“水桶”模型以及利用半导体PN结电子、空穴扩散理论建立有限元仿真模型,将这两个模型分别进行激光对CCD探测器干扰效果的仿真计算,得到不同光功率下的饱和干扰面积,并与实验结果对比,结果表明:“水桶”模型并未能较好地解释实验现象,而有限元模型的仿真结果与实验结果更加接近。故可利用有限元仿真模型来预测实际激光对CCD探测器的干扰效果。     

微结构半导体中子探测器研制

微结构半导体中子探测器具备探测效率高、响应时间快、体积小等优点,性能相对传统平面型半导体中子探测器有本质提升。采用蒙卡方法分析了器件微结构参数对沟槽型微结构探测器的性能影响规律,并结合工艺条件制备出沟槽宽度26μm,沟槽间距13μm,沟槽深度22μm,灵敏区面积1.8×1.8 cm~2的微结构探测器。该探测器在10 V的反向偏压下,漏电流仅1.24×10~(-7)A/cm~2,优于国外研究组报道的漏电流特性。利用同位素α源开展了带电粒子探测性能测试,所制备微结构探测器可实现241Am源α粒子探测。在外加0 V偏压时,微结构探测器即可获得与电子学噪声区分明显的241Am源α粒子能谱。本工作证明了微结构探测器对带电粒子具有良好的探测性能。     

氡通过不同滤膜的扩散系数测量研究

基于气体透过滤膜的扩散原理,对应用于固体核径迹探测器累积测氡的三种滤膜在四种不同湿度下的氡扩散能力进行研究。实验结果表明:醋酸纤维滤膜和普通滤纸的扩散能力明显强于PE滤膜,更适用于固体核径迹测氡,且湿度对三种滤膜氡扩散能力的影响不明显。通过本次实验得到,醋酸纤维滤膜的扩散系数为1.46×10~(-9)m~2/s~2.59×10~(-9)m~2/s,普通滤纸的扩散系数为1.01×10~(-9)m~2/s~1.45×10~(-9)m~2/s。     

Design of current mirror integration ROIC for snapshot mode operation

Current mirror integration (CMI) read out integrated circuit (ROIC) topology provides a low input impedance to photo-detectors and provides large injection efficiency, large charge handling capacity and snapshot mode operation without in-pixel opamps. The ROIC described in this paper has been implemented with a modified current mirror circuit, with matched PMOS pairs for detector input stage and its biasing. The readout circuit has been designed for 30×30μm² pixel size, 4×4 array size, variable frame rate, 5 Mega pixel per second (Mpps). Experimental performance of the test chip has achieved 15 Me charge handling capacity, a high dynamic range of 83 dB, 99.8% linearity and 99.96% injection efficiency. The ROIC design has been fabricated in 3.3 V 1P6M UMC 180 nm CMOS process and tested up to 5 MHz pixel rate at room and at cryogenic temperature.