超薄光学元件精密加工关键技术

针对超薄光学元件在加工过程中因重力和磨头产生应力形变的特点,提出了一种高效、先进的超薄光学元件综合加工方法。该方法综合运用了精密铣磨、精密抛光、离子束修形等先进技术进行面形控制。在铣磨阶段采用受力分析和误差补偿的方法降低了元件变形引入的面形误差;在抛光阶段通过气囊抛光和沥青抛光的迭代实现了面形快速收敛;在离子束加工阶段充分利用其非接触、无应力的加工特点实现了高精度面形修正。实验选择径厚比为34(边长152 mm,厚度6.35 mm)的方形融石英材料进行加工实验。结果表明:在铣磨、抛光、修形阶段的各项指标都达到了精密光学元件的加工水平,最终的面形精度为PV=25 nm,RMS=1.5 nm。该加工方法可以广泛应用于超薄光学元件的高精度加工。     

基于红外技术的气体浓度检测方法研究

依据Lambert-Beer定律,推导出检测气体浓度的数学模型,得出了测量和参考探测器输出电压与气体浓度的函数表达式,表达式中的二个常数的数值取决于气室长度、气体吸收系数、探测器的电压探测率,经零点和满量程标准气样的标定,可确定这二个常数的数值,实现对仪器的标定.根据仪器零点随温度变化的关系,得到零点与温度函数表达式,用于零点温度补偿以及对零点温度补偿系数的计算;量程温度补偿方法是通过引入量程温度补偿因子,对测量和参考探测器输出电压与气体浓度的函数表达式进行修正,修正后的函数表达式用于量程温度补偿,也能对量程温度补偿因子中的补偿系数进行计算.矿用红外甲烷传感器采用本文的标定方法和温度补偿方法,在不同的环境温度下,对标准气样进行检测,其检测结果符合红外甲烷传感器标准所规定的基本误差.     

Survival of molecular information under surfaced‐enhanced resonance Raman (SERRS) conditions

In the present paper, we discuss the molecular information that can be derived from surface‐enhanced resonance Raman Scattering (SERRS) experiments performed with different excitation wavenumbers, which are close to resonance with an excited electronic state of the molecule [surface‐enhanced Raman dispersion spectroscopy (SERADIS)]. We specifically consider the situation, where a molecule is physisorbed to a site characterized by a local electric field with a direction independent of the direction of the external, exciting field. The molecular information available in this experimental situation is compared with the information available in a corresponding Raman dispersion spectroscopy (RADIS) experiment performed on a free molecule or a molecule physisorbed to a site, where the local field is isotropic. The consequences for resonance Raman scattering (RRS) and RADIS, when the molecule is adsorbed in the highly anisotropic hot spot (HS), are discussed; here it is shown that only the molecular information originating from the symmetric part of the scattering tensor can survive in SERRS and in SERADIS. Besides, it is shown that the depolarization ratio can no longer be used to discriminate between totally and non‐totally symmetric modes in the polarized surface‐enhanced Raman scattering (SERS) spectra. These results have implications for the resonance Raman spectra, but even more important for the application of the resonance Raman effect in the investigation of excited vibronic molecular states, in general, and in the investigation of electronic states in larger bio‐molecules, such as the various metallo‐porphyrins. Copyright © 2009 John Wiley & Sons, Ltd.     

Experimental validation of closed-loop adaptive optics based on a self-referencing interferometer wavefront sensor and a liquid-crystal spatial light modulator

A closed-loop adaptive optics system based on a self-referencing interferometer wavefront sensor (SRI WFS) using phase-shifting point-diffraction technique and an electrically addressed phase-only liquid-crystal spatial light modulator (LC SLM) is built and validated experimentally. The wavefront aberration of incoming beam is directly measured by analyzing four frames phase-shifted interferograms captured by a single CCD camera in two camera shots, and then by loading the conjugate function onto the SLM the wavefront aberration is corrected. The proposed scheme does not rely on any complicated control algorithm or wavefront-reconstruction algorithm and can achieve high-resolution and high-accuracy correction. Closed-loop correction results of single order Zernike aberrations and a Kolmogorov turbulence phase screen show that considerable improvements in the Strehl ratio (of greater than 0.94) is achieved.     

Relative entropy functions for factor maps between subshifts

Let and be topological dynamical systems and a factor map. A function is a compensation function for if for all . For a factor code between subshifts of finite type, we analyze the associated relative entropy function and give a necessary condition for the existence of saturated compensation functions. Necessary and sufficient conditions for a map to be a saturated compensation function will be provided.

     

基于灰度投影法运动估计的成像CCD平移补偿法

为了提高成像质量,得到高分辨率的图像。提出了一种基于灰度投影法运动估计的成像CCD平移补偿法,并给出其系统结构图。然后验证了分辨率标板在各种运动情况下该系统的补偿效果,并给出了评价结果分析,最后拍摄了实物并给出了恢复后的图像及评价。结果:该补偿法可以有效地恢复图像,对慢速运动图像和随机振动图像具有较高的恢复能力。结论:使得系统的整体性能得到了很大的提升,成像的分辨率也大大提升。     

基于MAD2020E加速度的0°-360°倾角传感器设计

介绍了基于MAD2020E型加速度计的0°-360°倾角传感器的基本原理,并结合实际加速度传感的特性,采用双轴无温度补偿方法进行了硬件和软件的设计。实验验证该倾角加速度传感器实现了外形小巧、精度高、智能化。     

无功补偿综合实践平台的设计

无功补偿是电气工程及其自动化专业学生所必需掌握的知识点之一.本文介绍了一种无功动态补偿综合实践平台的实现方案,利用调压器、异步电动机、同步发电机及灯箱模拟可变的有功及无功负荷,通过90度接线方式利用一表法测量系统的无功需求量.该值的变化决定投入分组电容的组别,实现了无功功率的测量-无功补偿的基本原理和实现-无功补偿效果评价的综合实践体系.实践证明,学生可以将多门课程中的知识点融会贯通成知识面,加深理解的同时增强了分析问题和解决问题的能力,效果良好.     

A novel 2.95-3.65 GHz CMOS LC-VCO using tuning curve compensation

This paper presents a new CMOS LC-VCO with a 2.95-3.65 GHz tuning range. The large tuning range is achieved by tuning curve compensation using a novel varactor configuration, which is mainly composed of four accumulation-mode MOS varactors (A-MOS) and two bias voltages. The proposed varactor has the advantages of optimizing quality factor and tuning range simultaneously, linearizing the effective capacitance and thus greatly reducing the amplitude-to-phase modulation (AM-PM) conversion. The circuit is validated by simulations and fab-ricated in a standard 0.18 μm 1P6M CMOS process. Measured phase noise is lower than -91 dBc at 100 kHz offset from a 3.15 GHz carrier while measured tuning range is 21.5% as the control voltage varies from 0 to 1.8 V. The VCO including buffers consumes 2.8 mA current from a 1.8 V supply.     

一种2.8ppm/℃，高PSRR的BiCMOS电压带隙基准源

本文设计了一种新型的高阶补偿,高PSRR的带隙基准源。电路利用双极型晶体管反偏电流ISS和正向电流增益β的温度特性进行曲率补偿,极大简化了补偿电路的面积和功耗;引入滤波电容和电平位移结构等技术提高了电源抑制特性。基于0.6-µm BCD工艺,该基准源在典型电压3.6V下工作电流约为28µA,温度系数为2.8ppm/℃,PSRR在低频时高于80dB,电源电压从3.6V变化到5.5V时线性调整率约为50ppm/V,能广泛应用于高精度便携式设备中。