共查询到19条相似文献,搜索用时 93 毫秒
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手机跌落试验主要用于检验手机质量,有限元分析模拟仿真方法能够帮助厂家在产品开发阶段优化手机结构,但不能对成品实物进行质量检验。针对上述问题,该文提出一种基于光学测量的手机跌落试验方法,采用双目立体视觉原理,利用摄影测量技术,提高数字图像相关法匹配精度,使用高速相机对手机跌落过程进行连续采集,提高系统标定精度后通过图像数据计算分析获取手机跌落过程中的全场位移及应变值。该文用华为荣耀4A手机前壳进行试验,成功获取其跌落过程中的三维全场变形数据,证明基于数字图像相关法手机跌落试验方法具有高精度、试验过程简便等优点,满足成品手机质量检测的需求。 相似文献
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提出并实现了一种基于工业摄影测量和数字图像的相关法,通过多种工业相机拍摄的多幅二维序列图像,快速解算出被测物体的三维坐标、变形和应变数据的方法。该方法解决了大型复杂工件生产现场快速检测难题,达到国际先进水平,可用于中小型工件和微纳米尺度工件的相关检测,以及材料性能分析,也可满足低速到高速的振动冲击和模态分析要求。在机械、材料力学等多个行业和多个学科的应用表明,该方法具有适用面广、三维全场检测、快速灵活方便的优点,取得了显著的经济和社会效益。 相似文献
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基于散斑强度相关函数的表面粗糙度测量方法 总被引:9,自引:0,他引:9
激光经过被测表面反射和散射后,通过自由空间传播至观察面上形成散斑图像,其统计分布依赖于被测表面的微观形貌。分析此散斑图像的二阶统计特性,导出了强度变化的相关函数和表面粗糙度参数之间的关系。以表面粗糙平均值Ra分别为0.1靘, 0.2靘, 0.4靘和0.8靘的平磨标准金属样块形成的散斑图像为例,根据强度变化相关函数的离散化定义,计算得到该相关函数值。结果表明,表面越粗糙,散斑越分散,强度变化的相关函数波动越大。因此,该参数可以反映不同的粗糙面,用其作为表征表面粗糙度的特征参数,扩大了测量范围。该方法实验系统简单,对于实际测量环境要求不高,对震动不是非常敏感,适于在线测量。 相似文献
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在全面分析煤油燃气辐射特性的基础上,结合煤油燃气的具体特点,提出了适合于测量煤油燃气温度的辐射测量方法[4],并且建立了辐射测温系统,通过对煤油燃气温度的实际测量,验证了辐射测温法测量燃气温度的可行性。 相似文献
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An improved speckle projection profilometry that combines the projection of computer generated random speckle patterns using an ordinary LCD projector and the two-dimensional digital image correlation technique for in-plane displacements measurement is proposed for accurate out-of-plane shape and displacement measurements. The improved technique employs a simple yet effective calibration technique to determine the linear relationship between the out-of-plane height and the measured in-plane displacements. In addition, the iterative spatial domain cross-correlation algorithm, i.e., the improved Newton-Raphson algorithm using the zero-normalized sum of squared differences correlation criterion and the second-order shape function was employed in image correlation analysis for in-plane displacement determination of the projected speckle patterns, which provides more reliable and accurate matching with a higher correlation coefficient. Experimental results of both a regular cylinder and a human hand demonstrate that the proposed technique is easy to implement and can be applied to a practical out-of-plane shape and displacement measurement with high accuracy. 相似文献
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Self-mixing laser speckle velocimeter for blood flow measurement 总被引:4,自引:0,他引:4
Ozdemir S.K. Takamiya S. Ito S. Shinohara S. Yoshida H. 《IEEE transactions on instrumentation and measurement》2000,49(5):1029-1035
A velocimeter using speckle phenomena in self-mixing laser diodes (SM-LDs) is used to evaluate the blood flow noninvasively. The mean frequency of the speckle signal obtained from the self-mixing laser diode reflects the activity of the blood flow in a certain probing area. The experimental results show that this new type of speckle velocimeter can be useful for the relative evaluation of blood flow in human tissues 相似文献
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A laser speckle correlator with high optical magnification is presented, and its performance in the measurement of strain is demonstrated experimentally. Two separated areas on a test specimen are illuminated with laser beams, and displacements of each area are measured by performance of laser speckle correlation on successive magnified images. The interplay of magnification, lens aperture, surface roughness, pixel spacing on the CCD array sensor, and the attainable precision of correlation are investigated theoretically and experimentally. Resolutions that are usually considered accessible only to interferometric techniques are achieved: displacement resolutions of less than 50 nm and strain measurements of less than 10 mustrain across distances of the order of 10 mm are demonstrated. At high magnification, speckle decorrelation due to out-of-plane displacement becomes a stringent restriction, and surface height correlation effects may limit speckle contrast and broaden speckle correlation peaks. 相似文献
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运用散斑统计理论,结合数字图像处理技术,设计了一套激光散斑测量刚体面内微小位移的实验系统,再利用刚体位移前后的散斑图像的互相关性,实现了刚体面内的位移测量.测量结果表明,针对刚体面内小于300μm的微小位移,x轴和y轴的绝对位移误差为±14μm,相对误差为±6.25%左右. 相似文献
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Electronic speckle photography: measurement of in-plane strain fields through the use of defocused laser speckle 总被引:1,自引:0,他引:1
Sjödahl M 《Applied optics》1995,34(25):5799-5808
High-accuracy, noncontact measurements of in-plane strain fields have been performed through the use of an electronic-speckle-photography system. The strain fields are extracted from the displacement of defocused laser speckle in a telecentric imaging system. Two different illumination configurations have been suggested, both of which use four illumination directions. Both configurations produce results of an accuracy according to Me/ΔL, where M is the demagnification of the telecentric imaging system, e is the random error in the speckle-displacement fields, and ΔL is the magnitude of the defocusing distance. The maximum defocusing distance possible was found to be restricted by the spatial resolution, especially at high magnifications. In experiments on a semicircularly and a rectangularly notched aluminum sheet, the principal strain field around the notch was measured with a random error in the strain field of less than 10 μstrain (μm/m). 相似文献
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Ori Izhak Rosenberg 《Journal of Modern Optics》2020,67(13):1197-1209
This paper reports a straightforward technique for three-dimensional (3D) visualization of a flow profile by a hybrid algorithm combining Fourier transform orthogonal fringe projection and laser speckle imaging techniques. The use of orthogonal projection aims to suppress the zero order allowing surface reconstruction with high spatial resolution and accuracy while analyzing the intensity fluctuations of diffuse backscattered laser light providing 2D flow information. Once both are achieved, 3D flow visualization can be displayed. The method is experimentally validated first with a plastic tube filled with scattering liquid (milk) running at various controlled flow rates and then with the tube embedded under scattering layers (chicken breast) of varying thickness. The system includes a single, common camera, a commercial projector (profilometry channel), a laser light source (flow channel), and a computer station. In addition, orthogonal projection processing was combined with Hilbert transform, increasing the visualization and resolution of the measured flow profile. 相似文献
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Real-time laser speckle photography 总被引:1,自引:0,他引:1
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In spite of its obvious advantages over conventional contact and immersion techniques, laser interferometry has not yet become a practical tool in ultrasonic nondestructive evaluation since its sensitivity is insufficient in most practical applications. Part of the problem is that the maximum signal-to-noise ratio often cited in scientific publications and manufacturers' specifications cannot be maintained on ordinary diffusely reflecting surfaces. Although these surfaces reflect a fair amount (5–50%) of the incident laser light, this energy is randomly distributed among a large number of bright speckles. Unless the detector happens to see one of these bright speckles, the interferometer's signal-to-noise ratio will be much lower than the optimum. This adverse effect is almost completely eliminated by the suggested random speckle modulation technique. The conventional interferometric technique was modified to assure random occurrence of a few very bright speckles and to move the whole speckle pattern around at an appropriate speed. Random but frequent bright flashes detected from the surface of the specimen resulted. The bright periods are 0.1 ms or longer, sufficient to trigger the ultrasonic pulser and detect the transmitted signals before the flash subsides. As much as 5–10 times improvement of the optical sensitivity was achieved by this novel approach and close to maximum signal-to-noise ratio was maintained everywhere on the surface of a diffuse object. 相似文献