CMOS图像传感器成像系统

介绍 CMOS图像传感器的历史背景、发展现状、像素单元的结构、工作原理以及CMOS图像传感器芯片的整体结构 ,比较了 CMOS图像传感器和 CCD图像传感器的性能 ,详细阐述了整个 CMOS图像传感器成像系统     

基于CMOS图像传感器DCT算法的JPEG压缩研究

近年来,随着信息技术的快速发展,CMOS图像传感器迅速发展。但是,由于CMOS图像传感器传输的数据信息量巨大,严重影响了传感器系统的实时传输和存储。因此,结合CMOS图像传感器的结构、工作原理以及DCT图像压缩理论,基于JPEG压缩编码中的色彩空间转换、DCT变换、量化以及熵编码四个原理过程及其功能,实现将JPEG编码压缩方法融入到CMOS图像传感系统中。既能保证有较高的压缩比和良好的图像质量,又能极大地提高CMOS图像传感器的输出效率,促进CMOS图像传感器系统进一步发展。     

CMOS图像传感器与CCD的比较及发展现状

本文从读取方式、集成性等多角度对CMOS图像传感器和CCD作了比较,并介绍了CMOS图像传感器和CCD技术的发展现状,指出了CMOS图像传感器的发展趋势.     

利用CMOS图像传感器测试成像镜头MTF的实用方法

介绍了一种用CMOS图像传感器测量镜头MTF的实用方法及其实用实例。该方法通过引入参考空间频率,利用在CMOS图像传感器像面上,对被测空间频率与参考空间频率的像素灰度值的读取,能够便捷并且比较准确地测定镜头的MTF值。由于参考空间频率的引入,大体消除了CMOS图像传感器本身MTF对测量结果的影响,从而使测量结果更接近理论运算结果。     

CMOS图像传感器中卷帘式快门特性及其应用技术研究

为了研究CMOS图像传感器卷帘式快门的具体应用,结合具体的CMOS图像传感器进行研究。首先,本文介绍了卷帘式快门的特点和工作原理,对具有卷帘式快门的CMOS图像传感器成像特性进行了分析,并对采用卷帘式快门工作方式的CMOS图像传感器进行了成像实验研究。其次,本文还对一种利用卷帘式快门相机拍摄的单精度视图来计算高速物体在三维空间中的位移和速度的新方法进行了探讨,最后,提出了建立一个运动目标的透视投影模型,讨论了估计目标位姿和速度的方法。实验结果表明,具有卷帘式快门的CMOS图像传感器对运动物体成像时会产生一定程度的畸变,畸变的程度与积分时间等传感器参数的设置有关。经过实验可以在误差最小化的情况下得到运动物体的位姿和速度参数,经过计算误差在2.5%以内。对实验结果的分析已经证明了其可行性。这种计算方法能够使得低价格,低耗能的CMOS相机转化为一种新的速度传感器。     

CMOS——图像传感器的新宠

目前图像传感器主要有CCD和CMOS两种。过去CCD图像传感器占有绝对的优势，而CMOS只作为低端产品应用于摄像头和简易PC相机上。但随着大规模集成电路的发展，CMOS图像传感器性能有了极大提高，CMOS必将是未来图像传感器的发展方向。     

CMOS图像传感器中卷帘式快门特性及其应用

结合CMOS图像传感器研究了CMOS图像传感器卷帘式快门的具体应用.介绍了卷帘式快门的特点和工作原理,分析了具有卷帘式快门的CMOS图像传感器的成像特性,并对其进行了成像实验.探讨了一种利用卷帘式快门相机拍摄的单精度视图来计算高速物体在三维空间中的位姿和速度的新方法.最后,提出了一个运动目标的透视投影模型,讨论了估计目标位姿和速度的方法.实验结果表明:具有卷帘式快门的CMOS图像传感器对运动物体成像时会产生一定程度的畸变,畸变的程度与积分时间等传感器参数的设置有关.在误差最小化的情况下得到了运动物体的位姿和速度参数,计算误差在2.5%以内,测量精度为0.01 rad/s.对实验结果的分析证明了方法的可行性.这种计算方法能够使得低价格、低耗能的CMOS相机转化为一种新的速度传感器.     

双CMOS成像系统中运动模糊图像的复原

为获取高空间分辨率的清晰图像,设计了一种双CMOS成像系统.该系统的两片CMOS传感器可同时获取相同场景的图像.其中一片CMOS传感器获取高帧率、低空间分辨率的图像序列;另一片CMOS传感器获取低帧率、高空间分辨率的运动模糊图像.首先,通过光流法计算高帧率、低空间分辨率CMOS传感器获取图像序列的全局运动路径,在能量守恒和能量与积分时间成正比2个约束条件下估计运动模糊核初始值,通过贝叶斯准则交替迭代优化运动模糊核.最后,利用TV-L1方法从低帧率、高空间分辨率CMOS传感器获取的模糊图像中快速、有效地恢复出清晰图像.仿真和实验结果表明;有38％以上的仿真图像复原结果误差率小于2,且受噪声影响小,复原图像的振铃小.另外,能有效去除实拍图像的空间移不变运动模糊.     

CMOS图像传感器的γ射线电离辐照实验研究

为了研究核退役装备在核辐射环境下作业时图像监控设备的工作状态等数据,对用在核退役作业现场的某国产CMOS图像传感器进行γ辐照实验。采集得到辐照时的γ射线对CMOS图像传感器所输出的暗图像造成的干扰数据,并研究γ射线对CMOS图像传感器的性能参数影响。实验结果表明:辐射射线的总剂量效应使得传感器中暗电流增大,传感器输出的图像里脉冲颗粒噪声与平均灰度值会随着辐照剂量的变化而发生变化。     

我国成功研发世界最高分辨率CMOS传感器

正以色列全球晶圆代工厂Towerjazz与中国的长春长光辰芯光电技术有限公司(Gpixel)联合发布了宣称是世界上最高分辨率的1.5亿像素全画幅CMOS图像传感器GMAX3005,这是国产CMOS传感器的新高度。虽然宣称GMAX3005是全画幅图像传感器,不过其尺寸实际为167.6mm×30.1mm,和传统意义上定义的全画幅36mm×24mm相比,感光面积还是大出了很多,而且其宽高比相当奇特,是超宽幅的瘦长型传感器。一般用户不必     

基于数学形态学的气泡水平尺自动检测系统研究

针对气泡水平尺的自动检测问题,对机器视觉领域的边缘提取、轮廓跟踪等算法进行了研究,提出了一种基于数学形态学与轮廓跟踪的气泡水平尺自动检测方法。引入了快速中值滤波算法和多线程工具对工业相机拍摄的水平尺气泡图像进行了滤波处理,以提高中值滤波算法的运算效率,使用了模糊最小化形态学梯度对气泡图像进行处理,以得到气泡的边缘信息。同时针对该应用场合,分析了气泡边缘图像的灰度剖面特性得到左、右平行参考线的位置,结合目标邻域点法搜索气泡端点来对气泡位置进行了搜索,得到了气泡偏移距离,从而实现了高效率高准确度的气泡水平尺偏移实时检测。研究结果表明,该方法在保证结果准确的同时,能够极大提高计算速度,并且计算结果能极好地适应光照变化。     

基于Canny边缘检测和加权最小二乘法的气泡水平仪实时检测方法

针对气泡水平仪的自动标定问题,对机器视觉领域中的边缘提取算法、最小二乘法、轮廓跟踪算法等方面进行了研究。提出了一种基于Canny边缘检测和加权最小二乘法的气泡水平仪实时自动检测方法,以提高检测气泡水平仪的准确度和效率。引入了Canny边缘提取算法对工业摄像机所拍摄的水准柱侧面图像进行处理,以得到参考线和气泡的边缘信息。引入了一种自适应选取Canny边缘提取算法的阈值的方法,以克服工业现场光照变化的影响。同时针对本应用场合,采用了加权最小二乘法对左右平行参考线进行拟合,并结合二分搜索算法对水平尺上的气泡位置进行了搜索,从而实现了气泡水平仪的高准确度实时检测。研究结果表明,该方法能够准确、快速地对气泡进行定位,能够较好地适应光照变化。     

气液两相流中上升气泡体积的计算方法

通过高速摄像机拍摄气液两相流中上升气泡的运动过程,分别记录不同直径的气孔所产生的单个气泡上升过程的连续图像,结合数字图像处理技术,提取了气泡的面积、当量直径、几何中心、速度、加速度等特征参数.并在此基础上,应用两种计算气泡体积的方法:几何方法和受力分析法,实现了气泡体积的初步计算.几何方法计算气泡体积是根据图像中气泡的形状构造一个与气泡体积相当的椭球体,进而计算椭球体的体积;而受力分析的方法则是通过分析气泡在垂直方向上的受力情况,根据牛顿第二定律推导出气泡体积的计算公式.并对两种方法计算出的气泡体积值进行分析对比,阐明了这两种方法适用情况,计算出单个气泡上升情况下的气相体积含气率.     

多尺度气泡尺寸分布数字图像测量方法研究

鼓泡塔是一种广泛应用于能源和环境领域的多相流反应器,鼓泡塔中气泡的大小和浓度对于研究鼓泡塔中"三传一反"过程具有重要意义。采用高速摄像法和数字图像处理技术开展了鼓泡塔中内多尺度气泡尺寸分布测量研究,针对气泡识别过程中密集气泡易发生重叠的问题,提出基于曲率计算的凹点匹配与圆周拟合的重叠气泡分割与轮廓重构算法。搭建了鼓泡塔反应器实验装置,针对星型、均匀和方形3种不同进气孔形态的气泡分布器开展了实验研究,分析了不同尺度气泡的尺寸分布规律。试验结果表明:该算法不仅能够有效地从图像中提取轮廓清晰完整的气泡,而且能够对图像粘连重叠的气泡进行准确分割,从而可精确地获得多尺度气泡尺寸分布。随着气体流量的增加,小气泡的数量急剧增加,同时产生更大的气泡;气泡的最大直径和Sauter平均直径均随气体流量的增加而增大,且两者的比值基本保持不变,即分布器形式对气泡尺寸分布均匀性有影响,方形分布器产生气泡最均匀,气含率相对其他两种分布器更高。实验结果证明了图像分割与轮廓重构方法在气液两相流中气泡参数在线测量的可行性。     

Gas-liquid flow patterns visualization in a self-priming centrifugal pump

The self-priming pumps are ubiquitous in gas-liquid mixtures lift and transportation areas. The fast self-priming time is a vital evaluation index for a self-priming pump. However, the bubble movement path and the bubble size distribution characteristics during the self-priming process are still an open issue. This paper aims to obtain the gas-liquid flow patterns inside a centrifugal pump during the self-priming process and evaluate the effect of the rotational speed and the position of the back-flow hole on the self-priming time through experiments. A centrifugal pump with a double-blade was designed as a visualization prototype. The high-speed photography technology was used to capture the bubble motion and size in the pump during the self-priming process. The bubble image processing method was used to identify the bubble size distribution in the diffuser during the self-priming process. The bubble number and size distribution images were presented to understand the influence of the rotational speed and the position of the back-flow hole. The higher rotational speed accelerates the gas-liquid mixing rate and shortens the self-priming time. However, there is a limited value of the self-priming time as the speed goes up to a certain high level. Moreover, the position of the back-flow hole slightly affects the self-priming time.     

Estimation of bubble size distributions and shapes in two-phase bubble column using image analysis and optical probes

A precise estimation of bubble size distributions and shapes is required to characterize the bubble column fluid dynamics at the “bubble-scale”, and to evaluate the heat and mass transfer rate in bubble column reactors. Image analysis methods can be used to measure the bubble size distributions and shapes; unfortunately, these experimental techniques are limited to resolve bubble clusters and large void fractions, and can not be applied under relevant operating conditions (e.g., high temperature and pressure). On the other hand, needle probes (i.e, optical and conductive probes) can be used to measure bubble sizes in dense bubbly flows and under relevant operating conditions; however, needle probes measure chord length distributions, which should be converted into bubble size distributions by using statistical algorithms. These algorithms rely on correlations—generally obtained for single droplets/bubbles—that predicts the bubble shapes, by relating the bubble equivalent diameter to the bubble aspect ratio. In this paper, we contribute to the existing discussion through an experimental study regarding the bubble sizes and aspect ratio in a large air-water bubble column. The experimental investigation has consisted in gas holdup, image analysis and optical probe measurements. First, the gas holdup measurements have been used to identify the flow regime transition between the homogeneous flow regime and the transition flow regime. Secondly, the homogeneous flow regime has been described at the “bubble-scale”: chord length distributions and bubble size distributions have been obtained by using an optical probe and image analysis, respectively. Based on the experimental data from the image analysis, a correlation between the bubble equivalent diameter and the bubble aspect ratio has been proposed and has been compared with existing correlations. Finally, the chord length distributions have been converted into bubble size distributions using a statistical method, supported by the aspect ratio obtained through image analysis. The proposed approach has been able to estimate correctly the bubble size distributions at the center of the column then near the wall. We have also demonstrated that the correlations used to predicts the bubble shapes are the main point of improvement in the method.     

A note on spark bubble drop-on-demand droplet generation: simulation and experiment

The fluid dynamics of the spark bubble-generated droplet is studied both experimentally and numerically. The emphasis is especially on the droplet behavior after pinch-off. Commercial inkjet printers often produce satellite droplets along with parent droplets which are not desirable from the viewpoint of printing efficiency. Furthermore, standard drop-on-demand droplet generators are normally restricted to the generation of droplets with the same size as the nozzle diameter. In the spark bubble droplet generation method, a spark-generated bubble induces droplet formation through a hole in a solid surface separating the liquid and air interfaces. Immediately after ignition occurs, a bubble forms and creates pressure waves as it expands and contracts in a nonsymmetrical fashion. These pressure waves, depending on the geometries of the bubble location, plate, and hole may cause a single droplet smaller than the plate aperture to form and break up. In this article, a combined numerical and experimental study has been conducted to investigate the droplet behavior created in this manner. A high-speed camera is utilized to capture the droplet formation process. The numerical simulations have been carried out using the boundary integral spatial solution coupled with the time integration, i.e., a mixed Eulerian–Lagrangian approach. There is reasonable agreement between the simulations and experiment.     

平面图像里重叠微小气泡的分离及测量

目前，较准确地测量高密度、微米量级的微小气泡的方法为图像处理法，即利用CCD摄像机对其摄像来进行气泡测量。但在所获得平面图像里有部分气泡重叠，这会带来较大的测量误差。根据1台隔行CCD摄像机所摄得的平面图像里重叠气泡中各气泡像大多各自位于奇数扫描线和偶数扫描线上这一特征，分别对奇数和偶数扫描线上进行处理来分离重叠气泡，然后对同一物像进行识别和以物像的可见灰度像素对不可见像索进行校正来计算气泡的特征值，通过测量证明效果显著。     

Online monitoring of transit-time ultrasonic flowmeters based on fusion of optical observation

It is well-known that transit-time ultrasonic flowmeters (TTUF) are unsuitable for bubble-contained flows. This paper presents a new online monitoring method based on optical observation, which monitors the functionality of the TTUF in the presence of bubbles in the fluid. The method avoids the unnecessary Emergency Shutdowns (ESD) due to bubble presence in the fluid by bubble detection. The proposed method accomplishes bubble identification through a combination of image processing and wavelet analysis. In addition, a new method is proposed which estimates single bubble size in horizontal pipes using a data fusion approach.     

Bubble velocity measurement with a recursive cross correlation PIV technique

An image analysis method for measuring bubble velocity fields at high bubble number density is proposed. It is based on computing the cross correlation of bubble images with multiple spatial resolutions, i.e. a recursive cross correlation technique. Comparing several PTV and PIV schemes, it is confirmed that the recursive cross correlation leads to the best measurement results because of the robustness with respect to optical and dynamic characteristics of bubbles. The method is applied successfully to the measurement of bubble motion in bubble plumes accompanying a strong unsteadiness over a wide frequency range. The results reveal that the high frequency fluctuations of bubble velocities grow in the shear layer and near the top surface, while low frequency fluctuations dominate in the middle part of the tank. The characteristic frequency divides the frequency spectrum of the bubble fluctuation intensity into two regions: where there are turbulent behaviors and where there are macroscopic convection patterns in the bubble plumes.