Micromachined infrared pneumatic detector for gas sensor

We present a micromachined IR detector based on the principle of a pneumatic cell and suited as an IR detector in a miniaturised gas sensor. The detector basically consists of a sealed cavity, in which the heat generated by absorbed IR light results in an increased gas pressure. This pressure rise is detected capacitively. The theoretical performance of a 1 mm² micromachined device is calculated, and it is shown that a detectivity of 3.6·10⁹ cm. Hz^1/2/W can be expected. Moreover, a pneumatic gas leak is proposed to avoid thermal drift. Using conventional Silicon micromachining techniques, a prototype was fabricated which confirmed the principle of operation., The experimental results are compared to the theory.     

Uncooled IR imaging array based on quartz microresonators

A quartz crystal resonator's resonance frequency is sensitive to temperature. This sensitivity has been exploited in the past in thermometers made of single, macroscopic quartz resonators that can accurately detect temperature changes of μK. Using semiconductor microfabrication techniques, it is now possible to fabricate a large number of microresonators from a single quartz wafer. It is shown that combining the small thermal mass and high thermal isolation capability of such microresonators, the steep frequency versus temperature characteristics of resonators made of certain cuts of quartz and the low-noise characteristics of quartz crystal oscillators can result in high-performance infrared (IR) sensors and sensor arrays. In a microresonator sensor, the temperature change produced by the absorption of IR energy results in a frequency change that can be measured with a resolution that corresponds to a change in the resonator's temperature of less than a μK. Calculation shows that an array of microresonators in the 200 MHz-1 GHz range can be the basis of an uncooled IR imaging system with a noise equivalent temperature difference, NETD, of <0.01 K. The design and fabrication problems to be overcome before such microresonator arrays can be realized are discussed     

CMOS X-rays detector array based on scintillating light guides

This paper describes a pixel imaging array consisting in 400 μm×400 μm photodiodes fabricated in CMOS technology. An array of scintillating CsI:Tl crystals is placed above the photodiodes. These crystals are encapsulated in aluminum walls, forming a light path that guides the visible light produced by the scintillating crystal into the photodiodes. In this way, the X-ray energy is first converted into visible light which is then detected by the photodiode at the end of each light guide. The scintillator is 800 μm thick, absorbing almost all 20 keV X-ray photons. Usually, the spatial resolution of the scintillating X-ray detectors is identical to the scintillator thickness. By using the light guides, the scintillator thickness can be increased without decreasing the spatial resolution. The increase of the scintillator thickness is desirable in order to increase the X-rays absorption efficiency. Tests carried out on the system show very promising results near 20 keV.     

基于六电极石英晶体谐振器的姿态检测转换结构设计

根据石英晶体压电效应及各向异性的特点,基于Comsol Multiphysics软件进行有限元仿真分析得到径向力作用时AT切石英晶体薄圆片内各点的应力分布特点。通过应力分布特点设计制作了在同一晶片上的集成式六电极石英谐振器,并基于此谐振器设计制作了水平姿态传感器的转换结构初样。根据共模抑制原理,通过差频处理来抑制温度以及其他相关因素的干扰。室温下,样品放置在倾斜台并连接至谐振电路,旋转倾斜台并测量样品在不同倾斜角度时谐振器的谐振频率。实验结果表明:样品在-90°～90°之间谐振频率变化稳定,输入—输出关系线性良好,可用于姿态检测的敏感元件。     

基于红外面阵传感器的图像拼接算法

对大面阵红外传感器图像的拼接算法进行了研究.针对红外图像中噪声过多的问题,采用基于Harris角点的图像拼接算法进行噪声抑制并对Harris算法进行改进.首先根据图像像素响应函数值的特性,将Harris检测人工阈值改进为自适应阈值.然后在相似测度归一化互相关(NCC)粗匹配的基础上,根据图像间正确匹配角点对各自构成的四边形应满足四角相等的几何关系,采用有约束的随机抽样一致性(RANSAC)方法.实验结果表明:该算法避免了噪声的影响,使图像拼接具有适应性,对大面阵红外图像具有良好的拼接效果.     

微机械Golay腔型红外探测器的研究

通过分析微机械Golay腔型红外探测器设计中影响性能的关键因素:温致压变系数、红外吸收层、阻尼噪声,提出了一种采用硅和玻璃阳极键合技术实现的新型Golay腔型红外探测器。计算其灵敏度为2 700 pF/W、噪声等效功率为8.4×10-8W/Hz1/2和响应时间为0.5m s。利用光学测量变形,可以实现探测器无电化设计,使得测量不受强电磁场和湿度的影响。     

Uncooled infrared detector based on silicon diode Wheatstone bridge

In this paper, uncooled infrared detector based on silicon diode Wheatstone bridge is studied. Four identical temperature sensing elements made of several diodes in series are designed and fabricated with 2 μm feature size, among which two of them are suspended over the substrate through supporting legs, while the other two are on the substrate. By connecting these four temperature sensing elements in Wheatstone bridge’s form, we expect to reduce output noise of the infrared detector for differential output. The tested noise of the infrared detector is 1.24 μV, which is reduced by 58 % comparing to the detector constructed by one suspended temperature sensing element of the Wheatstone bridge. The measured sensitivity and noise equivalent temperature difference (NETD) of the infrared detector are 7.90 μV/K and 0.16 K, respectively. This infrared detector has potential of reaching a NETD in the milli-Kelvin range by using CMOS process with better feature size and pixels containing two supporting legs instead of four supporting legs.

     

石英晶体谐振器预应力条件下的模态分析

针对石英晶体谐振器在受到外力后其振动模态如何变化的问题,基于 Mindlin 的振动理论通过ANSYS 有限元仿真得出横向力引起石英晶体谐振器的振动模态形状.结果表明:在外力的作用下石英晶体的振动位移大小和振动方向都发生了改变.该结果对于压力传感器和石英微天平的开发应用具有重要意义.     

基于红外面阵传感器的小目标检测算法

研究了红外面阵传感器图像中小目标的特征,针对目标低信噪比的问题,提出了一种新的单帧红外图像小目标的检测方法。首先用改进的中值滤波对图像进行处理,抑制孤立噪声,然后对图像进行基于提升小波的分解,并用形态学对图像进行背景抑制,最后通过自适应阈值进行二值化分割检测出小目标。实验结果表明：该方法对面阵传感器红外弱小目标有良好的检测效果。     

石英谐振器力-频特性与结构参数的关系

用绝热水套悬挂装置测试了石英晶体的力-频特性。实验表明,沿厚度方向剪切振动的AT切石英晶体谐振器的力-频特性与激励电平及电极大小无关;泛音振动下谐振器的力敏系数的增加与泛音次数的增加不成严格的倍数关系;晶体的活力与晶体外形、振动频率、电极面积及受力无关。     

新型水晶体波谐振式膜厚传感器

介绍一种利用B模式厚度切变体波工作的新型水晶谐振式膜厚传感器。它采用修正式SC切型 ,以同线场电极激励。它可以在 10～ 2 80℃范围内工作 ,其测量范围为 0 .1～ 80nm ,准确度为 0 .0 2nm。     

基于RS-485总线的红外报警器设计

介绍了一种基于RS-485总线的新型红外报警器——"一线通"系统,该系统不仅可以及时准确发现报警目标,而且还可以避免线材的大量消耗,同时还具有良好的人机交互接口,因而在家居、工厂、仓库、商店以及金融等部门的安防设备市场极具发展前景.分析了该新型红外报警器的硬件组成,阐述了系统工作原理,介绍了软件的设计思想,并给出了主程序的流程图.     

非致冷双材料红外探测器模拟分析

非制冷双材料红外探测器具有高响应率和低噪声的特点,噪声等效温差接近理论极限。其灵敏度高的基本原理是基于一个比较大的双层材料热膨胀系数和杨氏模量差,通过双材料悬臂结构可以把热转换成机械运动。经过采用ANSYS软件进行有限元模拟,得出材料厚度比与灵敏度、极板位移与电容变化的关系曲线。同时,模拟分析了不同悬臂尺寸的几何模型,得出了相应的优化结构。     

微机械热电堆红外探测器的设计

阐述了微机械热电堆的设计原理、所用材料及主要结构,并研究了3×3阵列的微机械制造工艺,该热电堆结构支撑结构为氮化硅—氧化硅—氮化硅的复合介质膜。热电偶材料采用多晶硅和铝,热电偶采用并列排布的结构,对冷端覆盖了绝热层,用以提高热电堆的探测率。由于该制作工艺与标准IC工艺兼容,使得硅基热电堆红外探测器得到了越来越广泛的应用。     

基于自适应脉冲压缩-Capon滤波器的MIMO阵列雷达CFAR检测器

针对强杂波背景和有限训练样本数量条件下采用脉内编码压缩波形的MIMO阵列雷达目标检测问题,借鉴自适应波束形成技术中Capon最小功率估计器的相干源信号对消思想,提出了自适应脉冲压缩—Capon滤波器(简记为APC-Capon滤波器),并基于此滤波器的输出设计了一种CFAR检测器.理论分析和数值仿真均表明,该滤波器能够在执行非迭代自适应脉冲压缩并抑制各发射波形自相关距离旁瓣和互相关干扰的同时,实现杂波信号对消,即杂波抑制功能.检测性能仿真表明,尽管相同尺寸参数(包括发射阵元数、接收阵元数、脉冲编码位数、相参脉冲个数)条件下,所设计的基于APC-Capon滤波技术的CFAR检测器的性能不如训练样本数量充足时基于匹配滤波+样本矩阵求逆(SMI)技术的AMF检测器,但是随着尺寸参数的适当增大,前者的检测性能将逐渐超过后者在较小尺寸参数时的检测性能,且不显著增加计算复杂度和训练样本数量,而后者则因大尺寸参数时对计算复杂度和训练样本数量的需求过高而在实际中难以实现.仿真还表明,APC-Capon滤波器及其相应的CFAR检测器对发射波形的相关性(包括自相关性能和互相关性能)有一定的依赖性,但随着发射波形数量的增加,这种依赖...     

A CFAR detector for MIMO array radar based on adaptive pulse compression-Capon filter

Under the condition of strong clutter and finite training samples,a novel CFAR detector based on the proposed adaptive pulse compression-Capon filter (APC-Capon filter) is presented for MIMO array radar which transmits intrapulse coded waveforms.Both theoretical analysis and numerical simulations show that the proposed APC-Capon filter can utilize the non-reiterative adaptive pulse compression technique to alleviate both range sidelobes and mutual interference;at the same time it also can borrows ideas from the coherent signals cancellation of adaptive beamforming to perform clutter suppression.The detection performance simulations show that,with the same size parameters (including code length and the numbers of transmitter elements,receiver elements as well as pulses),the proposed CFAR detector is inferior to the adaptive matched filter (AMF) detector.But as the size parameters increase,the proposed CFAR detector will gradually outperform the AMF detector with smaller size parameters,and more importantly,unlike the AMF detector which has a lot of difficulties in performing due to the inordinate demands for the computational complexity and training sample size,this demands of the proposed CFAR detector will not significantly increase.The simulations also show that,the correlation properties of these intrapulse coded waveforms have certain effect on the APC-Capon filter and its corresponding CFAR detector.But fortunately,the effect will decrease as the number of intrapulse coded waveforms increases.     

MEMS based vacuum packaging method of optically readable infrared focal plane array

A MEMS based vacuum packaging method is developed for uncooled optically readable infrared focal plane array (OR-IRFPA). The vacuum packaging structure is made up of three layers: a glass visible window, a silicon spacer, and a silicon infrared window. The silicon spacer is bonded with the glass visible window to form two cavities: one cavity for getter and another one for OR-IRFPA. The isolation wall with micrometer scale pores is designed to ensure air’s free flow between two cavities and prevent getter powder from harming pixels of OR-IRFPA. The infrared window is used as cover board and selectively transmitting 8–14 μm infrared radiation. Infrared images of human body are gotten by using the vacuum packaged OR-IRFPA, which shows the vacuum packaging method is feasible and useful for OR-IRFPA.

     

Bidirectional microphone array with adaptation controlled by voice activity detector based on multiple beamformers

Multimedia Tools and Applications - Ambient noise suppression in a reverberant room is usually performed by the microphone array. The adaptive beamforming, whose typical representative is minimum...     

基于线阵光电探测器的FBG传感解调算法分析

采用线阵光电探测器光谱采集系统,对光纤Bragg光栅（ FBG）传感器反射谱进行数据采集。由于线阵光电探测器采样点数有限,为了研究不同数据个数对FBG反射谱寻峰精度的影响,基于LabVIEW开发平台,对比分析了FBG传感解调系统中常用的三种寻峰算法：质心法、高斯拟合法和多项式拟合法;比较了不同数据个数下各种算法的性能。实验结果表明：利用反射波峰上7个采样点数据拟合精度最高,并且高斯拟合算法的精度和稳定性能较好。