Multi-perspective digital image correlation method using a single color camera

A novel 3 D digital image correlation(DIC) system based on a single three charge-couple device(3 CCD) color camera is proposed in this paper. Images from three different perspectives are captured by a 3 CCD camera using a reflective-based pseudo-vision system. These images are then separated by the different CCD channels, and the correlation algorithm for the multi-camera DIC system is adopted to evaluate the images. Compared to the conventional multi-camera DIC system, the proposed system is much more compact. In addition, the proposed system has no loss of spatial resolution, compares to the traditional single camera DIC system. The complex surface measurement ability and the measurement accuracy is significantly improved through the use of the multi-camera DIC algorithm. The principle of the proposed system is described in detail as well as the experimental setup. A series of validation tests are performed, and the results are verified with the commercial 3 D-DIC system.

Observation and theoretic analysis of gas-bubble formation and growth in water-model

The behavior of bubbles is observed with high-speed digital camera in water-model. It is found that each bubble has three processes: bubble formation, bubble coalescence and bubble division. Bubble shape is spherical firstly, then elliptical and spherical crown after coalescence, and spherical again after division. These phenomena are explained theoretically. And the bubble size is defined newly. The so-defined bubble size is measured through digital camera and LECO graphical analyzer. And the measured results are compared with those in literatures.

Conventional digital cameras as a tool for assessing leaf area index and biomass for cereal breeding

Affordable and easy-to-use methods for assessing biomass and leaf area index （LAI） would be of interest in most breeding programs. Here, we describe the evaluation of a protocol for photographic sampling and image analysis aimed at providing low-labor yet robust indicators of biomass and LAI. In this trial, two genotypes of triticale, two of bread wheat, and four of tritordeum were studied. At six dates during the growing cycle, biomass and LAI were measured destructively, and digital photography was taken on the same dates. Several vegetation indices were calculated from each image. The results showed that repeatable and consistent values of the indices were obtained in consecutive photographic samplings on the same plots. The photographic indices were highly correlated with the destructive measure-ments, though the magnitude of the correlation was lower after anthesis. This work shows that photographic assess-ment of biomass and LAI can be fast, affordable, have good repeatability, and can be used under bright and overcast skies. A practical vegetation index derived from pictures is the fraction of green pixels over the total pixels of the image, and as it shows good correlations with all biomass variables, is the most robust to lighting conditions and has easy interpretation.

Calibration of digital camera integration accuracy for low-cost oblique aerial photogrammetry

This work describes a calibration process for inexpensive consumer cameras integrated into a low cost and compact aerial multi-view imager for remote sensing and photogrammetry.The main advantage of this design is to make the filming component lightweight and rapidly deployable,as well as reducing cost when compared with mainstream commercial oblique imagery.An in situ flight test was carried out in Guiyang.In that experiment,a meridian convergence-based approach was adopted to adjust preprocessing,the residue error and the captured images’exterior orientation linear and angular parameters were calculated by means of the direct geo-referencing approach yielding a favorable outcome for exterior orientation linear parameters of the camera,around 0.2–0.3 m deviation from the actual measured results at 1000 m flight above ground level.The camera’s exterior orientation angular parametersφ,ωwhose difference compared with the standard aerial aero triangulation approach reached a high accuracy level within the intended endurance of 0.005°.These results indicate that the compact implementation of the oblique aerial imager comprised of consumer level off-the-shelf digital cameras achieved competitive accuracy at a low cost and high versatility.

Portable device for the local three-dimensional deformation measurement using a single camera

The aim of this paper is to establish and validate a portable device for the local three dimensional deformation measurements using a single camera combined with a triangular prism mirror and two mirrors. The mirrors were utilized to convert a single camera into a stereo image system, which views a test object from two different directions and records the surface images of the test specimen on the two halves of the camera sensor in order to achieve a three-dimensional measurement. The proposed system consists of a single camera and the reflection system was integrated into a portable device to achieve a truly portable, low-cost, local three-dimensional deformation measurement, one-time calibration and easy implementation in situ. The optical design and measurement procedures to obtain the three-dimensional （3D） deformation measurements of the proposed system were described in detail. The efficiency and precision of the proposed system were verified by measuring the displacements of a translated fiat plate. As a practical application, the proposed system is used to measure the out-of-plane displacement of an aluminum circular plate with a central load. Moreover, the normal strain measurement of a plastic beam under symmetric four-point bending via an outer loading frame was also presented. The measurement results are in good accordance with the data obtained by strain gauges. The experimental results revealed that the proposed system was practicable and effective for the local three-dimensional deformation measurement. This system well-suited to both laboratory and field condition and will have significant application in the fields of engineering.

Diameter Measurements of the Upper Parts of Trees Using an Ultra-Telephoto Digital Photography System

We develop a new technique to measure the exact upper diameters of trees that is comparatively simple and inexpensive. We can measure the diameters of entire tree trunks efficiently and with high precision. The system uses a digital camera with a ~15 - 30× telephoto lens to take a photograph that can be used for measuring the diameter of the upper part of a comparatively slender tree trunk. Since this method requires a measuring distance and the height of the target point in the image, a range finder capable of measuring angles was combined with the main digiscoping system. A range finder sensor uses a laser and makes a 360 degree angle of observation possible. The diameter of a target position of the objective tree can be obtained by measuring the digital image using image editing software and calculations from spreadsheet software. We focus on the Japanese cedar species in the southwestern part of Japan. Photographic measurements were obtained prior to thinning. The estimates that we obtained largely agree with the true measurements of all trees. With regard to the estimated accuracy of all measured trees, the maximum error ratio was 7.0% (1.45 cm), with a ~2% - 4% error for most of the estimated results. Although the absolute value of the estimation error was 1.87 cm (5.3%) at the maximum (9.87 m in height and 35.5 cm in diameter), an estimation accuracy of <1 cm was reproduced in almost all measurements except for the extreme hypertrophy portion by butt swelling.

Imaging simulation and analysis of attitude jitter effect on topographic mapping for lunar orbiter stereo optical cameras

The geometric accuracy of topographic mapping with high-resolution remote sensing images is inevita-bly affected by the orbiter attitude jitter.Therefore,it is necessary to conduct preliminary research on the stereo mapping camera equipped on lunar orbiter before launching.In this work,an imaging simulation method consid-ering the attitude jitter is presented.The impact analysis of different attitude jitter on terrain undulation is conduct-ed by simulating jitter at three attitude angles,respectively.The proposed simulation method is based on the rigor-ous sensor model,using the lunar digital elevation model(DEM)and orthoimage as reference data.The orbit and attitude of the lunar stereo mapping camera are simulated while considering the attitude jitter.Two-dimensional simulated stereo images are generated according to the position and attitude of the orbiter in a given orbit.Experi-mental analyses were conducted by the DEM with the simulated stereo image.The simulation imaging results demonstrate that the proposed method can ensure imaging efficiency without losing the accuracy of topographic mapping.The effect of attitude jitter on the stereo mapping accuracy of the simulated images was analyzed through a DEM comparison.

基于异步FIFO的Camera Link数字图像光纤传输技术

为满足数字图像的远距离传输需求,设计用于传输Camera Link接口数字图像的光纤通讯系统。系统分为发送和接收两个部分,分别负责Camera Link数字图像到光信号的转化以及相应的逆变换过程。采用Cyclone I EP1C12 FPGA作为发送和接收板卡的逻辑控制核心。在发送板卡的FPGA内设计逻辑控制模块,操纵两个异步FIFO(先入先出队列),将接收到的数字图像缓存,用本地时钟读取后再进行串行化转换。在不改变数字图像时序关系的前提下,用本地时钟替换原有的像素时钟,消除像素时钟不稳定性对后续传输影响。实验表明,利用该技术可以有效提升光纤传输系统的适应性、稳定性,改善、消除由像素时钟抖动造成的传输图像抖动现象。

Rapid Texture Mapping from Image Sequences for Building Geometry Model

An effective approach, mapping the texture for building model based on the digital photogrammetric theory, is proposed. The easily-acquired image sequences from digital video camera on helicopter are used as texture resource, and the correspondence between the space edge in building geometry model and its line feature in image sequences is determined semi-automatically. The experimental results in production of three-dimensional data for car navigation show us an attractive future both in efficiency and effect.

Acquiring multi-spectral images by digital still cameras based on XYZLMS interim connection space

A method based on the XYZLMS interim connection space is proposed to accurately acquire the multi-spectral images by digital still cameras. The XYZLMS values are firstly predicted from RGB values by polynomial model with local training samples and then spectral reflectance is constructed from XYZLMS values by pseudo-inverse method. An experiment is implemented for multi-spectral image acquisition based on a commercial digital still camera. The results indicate that multi-spectral images can be accurately acquired except the very dark colors.

基于DIC的露天矿山微差爆破模型试验及数值模拟

随着电子雷管在露天矿山台阶爆破中的全面使用,微差爆破技术得到进一步发展,如何通过调整孔间延时提高炮孔之间相互作用力,成为矿山爆破技术的研究重点。基于混凝土模型模拟露天矿山微差爆破,建立高速摄影技术与数字图像相关(DIC)试验系统,基于全场微应变、高速摄影技术和数值模拟对不同孔间延时条件下的炮孔间裂纹发展过程进行了研究。结果表明:爆炸载荷下模型表面裂纹附近的应变持续时间约为3 ms,孔间延时为3 ms时下一个炮孔起爆能够提高炮孔之间的相互作用力;通过数值模拟展示了测点的压力分布特征,在孔间延时为3 ms时测点压力最大,验证了模型试验的准确性;利用MATLAB对数值模拟结果分析发现,孔间延时为3 ms时其破碎程度最佳,与模型试验结果具有较好的一致性;使用高速摄影技术结合DIC方法为研究炮孔之间的相互作用力及裂纹扩展提供了新思路。

高新技术格式数字电影摄影机性能测试及研究

为对高新技术电影格式进行创新探索和技术革新,中国电影行业提出自有数字电影高新技术格式标准,确保中国电影在画质清晰度、色彩表现力、视觉效果等方面能够达到甚至超越国际标准,为中国电影艺术的视觉表达开辟了新的维度,增强观众的沉浸感和情感共鸣。基于此,中影电影数字制作基地有限公司开展了高新技术格式数字摄影机选型测试工作,本次测试围绕不同画幅数字摄影机在拍摄高新技术格式时的画面分辨率、宽容度、亮暗部色彩还原与噪波表现,以及不同机型在完整拍摄流程上的表现进行了测试。本文为测试的前后期工作做了较为详尽的总结,同时也为中国自有数字电影高新技术格式标准在实拍器材部分标准的确定方面进行先期实践与科研。

基于单高速相机3D-DIC的涡轮叶片全场振动测量

采用成本较低、结构紧凑且使用便捷的单高速相机三维数字图像相关方法(single-camera high-speed three-dimensional digital image correlation,简称SCHS 3D-DIC)对涡轮叶片的振动特性进行试验研究。首先,介绍了测量装置和原理,以悬臂铝板为对象开展验证试验,结果证明了该测量系统的准确性与有效性;其次,开展了叶片的全场振动特性测量,得到了其三维形貌、模态特性、全场位移与应变分布,获得了叶片在振动载荷作用下的高应变区域位置及应变分布特点。研究表明,SCHS 3D-DIC方法相比常规双高速相机3D-DIC方法具有更高的视场利用率,适合于细长型的涡轮叶片的振动测量试验。

基于直方图的手机玉米冠层数字图像氮素诊断方法

【目的】便捷准确地诊断作物氮素营养状况是实现作物精准施肥和氮肥资源合理利用的关键。近年来应用数码相机等工具进行作物营养诊断的研究受到广泛关注。本研究采用智能手机相机获取玉米冠层图像,建立完善的基于手机相机的氮素营养诊断技术,并比较传统的图像均值方法和直方图方法对氮素营养诊断的可靠性,以探明夏玉米氮素营养诊断的最佳适用模型。【方法】基于田间氮肥用量试验,采用智能手机相机获取夏玉米拔节期冠层图像,提取夏玉米冠层图像的G/R、G/B、NRI[R/(R+G+B)]、NGI[G/(R+G+B)]、NBI[B/(R+G+B)]和(G-R)/(R+G+B)6种颜色指数均值及直方图敏感区间,分别建立冠层图像色彩参数均值模型与直方图模型,分析其与玉米叶片含氮量和产量的关系。利用决定系数(R^(2))、均方根误差(RMSE)、平均绝对百分比误差(MAPE)对比不同指数模型模拟估算玉米叶片含氮量和产量的稳定性和准确性,建立基于手机相机获取夏玉米冠层图像的氮素营养诊断模型。【结果】施氮量显著影响玉米叶片含氮量、产量及冠层图像色调和植被覆盖度。直方图波峰b随叶片含氮量的增加而发生变化,相较于冠层图像色彩参数指数均值方法,指数直方图法适用于不同品种的氮素诊断。色彩参数(G-R)/(R+G+B)直方图可以更好地反映作物覆盖率及整体颜色信息,指数直方图与玉米叶片含氮量和产量也呈现较好的相关性。基于神经网络模型验证数据集精度评价指标,指数直方图模型中玉米叶片含氮量和产量的MAPE值和RMSE值均低于指数均值模型,R^(2)达到0.753,大于指数均值模型。指数直方图模型验证结果MAPE值达到5.80%,RMSE值为0.07,估算精度高,泛化性强。结果表明,冠层图像色彩参数指数直方图在估算叶片含氮量和产量时具有更高精度和更强鲁棒性,能够有效利用玉米叶片覆盖度、颜色等特点,具有较好的稳定性。【结论】利用智能手机相机获取玉米冠层数字图像,结合冠层图像色彩参数直方图方法建立的神经网络模型具有较好的应用效果,提高了估测精度,作为一种新方法在玉米氮素营养快速无损诊断和精准施肥中具有较好的应用潜力。

基于机器视觉的数字图像处理系统设计与实现

图像技术在计算机技术的发展推动下,被广泛应用于各个领域,且呈现出良好的应用效果。基于机器视觉的数字图像处理系统,已经成为现代科学和技术中不可缺少的工具。该文以此为出发点,探究基于机器视觉的数字图像处理系统设计方案,并思考系统的实际应用价值。

用于材料变形测量的数字图像相关方法

为解决传统的三维数字图像相关方法在测量复杂材料变形上的局限性,介绍了二维、三维数字图像相关方法、连续布置的多相机数字图像相关方法及两种方式的相机布置。多个具有一定重叠视场的相机同时进行标定,形成一个测量连续全表面变形的整体三维测量系统。通过对有大曲率的钢筋套筒表面变形进行多相机全局测量,验证多相机数字图像相关方法的有效性。研究结果表明,连续布置的多相机数字图像相关方法在材料变形测量中是一种可靠的三维全场变形测量方法。

高速数字图像相关法在化学螺栓混凝土拉拔试验中的应用

提出了一种基于高速数字图像相关方法对混凝土中化学螺栓进行拉拔的试验方案,可用于捕捉和分析化学螺栓与混凝土间的变形发展和破坏形态。为实现直接观测化学螺栓与混凝土界面位移和应变场,采用半模试件进行试验研究。为证明其可行性,将半模试件与全模试件的粘结-滑移响应进行对比。结果证明,半模试件与全模试件具有一致的粘结-滑移响应,可以用来研究化学螺栓与混凝土界面的粘结机理。最后,利用高速摄像机捕捉混凝土破坏时刻的图像,通过数字图像相关法技术对采集的图像进行分析,直接测量了化学螺栓从混凝土中破坏时界面的位移和应变。

一种基于数字图像处理外螺纹参数校正技术

国内中低压阀门产品,螺纹为最常见的一种连接方式,传统的螺纹检测方法工作效率低下,测量的精度也不高,阀门批量生产过程中基本采用螺纹规进行快速检测螺纹中径来判断螺纹是否合格,所以数字图像处理技术应用到螺纹检测中也是一种趋势。本文基于CCD数字图像识别处理技术,依据外螺纹投影边界形成的空间位置关系,创造性地建立了投影边界方程来消除非接触式测量圆柱外螺纹牙型过程中产生的误差。本文对外圆柱螺纹参数(螺距、牙型角等)进行1次校正,其边界已逼近理想的圆柱外螺纹牙型,得到精度极高的圆柱外螺纹牙型边界,实现了对圆柱外螺纹几何尺寸的非接触测量。该方法测量速度快、精度高、成本低,非常适合用于阀门普通螺纹产品大批量生产过程中的在线螺纹检测。

面阵数字航测影像快速辐射校正方法与实现

随着计算机软硬件的发展,特别是可编程图形处理单元(GPU)框架计算统一设备架构(CUDA)的不断进步,使得利用CUDA开发影像快速处理应用的需求大幅增加。本文在分析国产大面阵航测相机DMZⅡ辐射特性的基础上,提出了基于C UDA的面阵数字航测相机全色子影像快速辐射校正方法,阐述了具体实现步骤和线程配置方法,并利用DMZⅡ相机在某试验区获得的影像数据,开展快速辐射校正算法性能测试。结果表明,相较于传统中央处理器(CPU)串行编程方法,本文提出的方法可提高超13倍的计算效率,且逻辑明确,实现简单,可为开发类似影像快速处理需求的相关应用提供技术参考。

利用数码相机和Photoshop软件非破坏性测定叶面积的简便方法

采用数码相机获取叶片的数字图像,用Photoshop图像处理软件计算叶面积,并与目前常用的剪纸法和叶面积仪测定法进行比较分析。结果表明,本方法和上述传统测定方法测定结果存在极显著线性相关;不同拍摄分辨率、单位叶面积存贮像素个数和拍摄角度对测定结果无显著影响。和其它方法相比,本方法具有准确、快速、成本低廉、适合非破坏性动态连续观测等优点,适用于植物生理生态学研究中叶面积的测定。