【作者】 祝振敏；

【导师】 曲兴华；

【作者基本信息】 天津大学 ， 测试计量技术及仪器， 2011， 博士

【摘要】 视觉测量作为一种非接触测量方法已经得到了广泛的应用,随着数字影像与光源设备硬件的进步和数学与计算机图像处理方法软件的发展,附有色彩信息的视觉测量技术开始受到更多的关注,相对于灰度视觉方式具有更丰富的信息,但是彩色视觉测量在工业应用上仍然较少。本文搭建了具有彩色照明光源和工业彩色相机的视觉测量系统,研究了视觉测量系统的正确显色方法,用于物体的颜色测量,研究了具有彩色信息的视觉测量理论和方法,用于提高检测目标的图像对比度。主要研究内容包括以下几方面:针对颜色测量与彩色图像采集对光源照明的要求:良好的多波段混光性,近距离照明的辐照均匀性。提出了一种间接照明的光源照明方式,利用多波段的LED阵列与高漫反射率的半球形内表面实现均匀照明,根据LED的朗伯体特性和高漫反射表面的双向分布函数构建了光源的数学模型,通过实测均匀度以及实拍的图像论证了理论模型的正确性与混光性的实现程度。搭建了一套基于此彩色照明光源和工业彩色相机的视觉测量系统,实现了彩色光源各个波段单独控制并且亮度256级数字可调。研究了彩色照明光源的色度学特性。通过与标准D65光源对比,三基色分量R:G:B=254:237:90时的色温和色度坐标最接近于D65光源,此时的颜色显现能力最好,光源的色彩饱和度更高,色彩表现更加丰富。相关色温变化范围宽泛,平均颜色复现误差也处于CIE规定的较优显示效果区域。针对采集到的彩色图片受相机的光谱响应函数和光源的影响,目标的颜色可能与物体真实的颜色存在一些差异,采用了多项式回归的方法分别在D65光源和LED阵列光源拍摄的图片进行校正,在不同颜色空间sRGB和CIEL*a*b*进行校正对比,分析了两种空间的图像显示、校正步骤以及校正精度等,选择了最为合适的颜色空间进行校正,并对一实际拍得的图片进行了颜色校正,效果良好。研究了最优波段光源照明方法用于提高目标的颜色对比度,借鉴彩色滤光方式,通过测量材料表面的反射函数,利用偏最小二乘法建立了数学模型,VIP得分为波段选择的最要依据,选取了能够提高检测表面对比度的三个波段间隔,实验结果证实了方法的有效性。利用光的偏振特性提高目标的颜色对比度,在工业电路板检测时,通过旋转线偏振片,获取0度、45度、90度不同相位图像,计算得到了偏振度和偏振相位图像后,与彩色视觉测量系统获取的彩色信息结合,分别在RGB和HSI空间进行了图像融合,相对于原来的图像,融合后图像中目标的颜色对比度显著提高,并且不受光照过暗、不均的影响。更多还原

【Abstract】 Currently vision measurement has been widely used as a non-contact measurement method. With the development of digitized video, illumination hardware equipment, mathematics and image processing software, the technology of vision measurement with color information has been given serious attention. Compared to grayscale vision, color vision measurement has abundant information, but it is still used less for industry application. The vision measurement system with color illumination and color CCD was constructed. The method of coloration for our vision measurement system was performed to measurement the color of object. The method of color vision measurement was studied for enhancing the contrast of detected object. The main research contents are shown as follows:For color measurement and image acquisition, well multiple-wavelength color mixing characteristic and illumination uniformity of near-field distance are needed. This paper presents an indirect method for vision measurement system. Multiple-wavelength LED arrays and sphere inner surface with high reflectance were used to realize the uniform illumination. Using the Lambertian characteristic and Bi-directional Reflectance Distribution Functions (BRDF) of the sphere’s inner surface, a mathematically simulated algorithm is developed. The uniformity of color illumination and the experiment images were used to verify the validity of simulated algorithm and the mixing results. Then the color vision measurement system was constructed by color illumination and color CCD. Each wavelength of LED intensity was independent controlled, and can be adjusted from 0 to 255.The colorimetric property of color illumination was studied. Compared to standard D65 illumination, chromaticity coordinates and correlated color temperature of white balance R:G:B=254:237:90 are close to D65 illumination. Color vision light source has a large range for adjusting the correlated color temperature and has better ability of color display. The ability of color reproduction reaches better result of color reproduction.The captured images of color vision system were influenced by spectral response functions of camera and the illumination. The color of object is different from the truth color. The method of polynomial regression was used for color correction of color illumination and D65illumination. The precision of correction, image display and correction procedure were compared in sRGB and CIEL*a*b* color space. Then the sRGB color space was selected. A real captured image was used for color correction, and the color of object is closed to the truth color.Wavelength intervals selection of illumination was used for enhancing the contrast of image. The reflectance functions of material surface were measured. The Partial least squares(PLS) was used for building the mathematic model, the VIP scores were used for selecting the effective wavelength intervals. Three wavelength intervals were used for color illumination. The experiment results show the usefullness of this method.The polarization property of light is useful for color vision measurement system. The fusion of polarization and color image was used for enhancing the contrast of image. For detecting the industry circuit wafer, the 0, 45, and 90 indicate the orientation of the polarizer in degrees when each specific image was taken. The Degree-of-polarization and Phase-polarization images were obtained. Then these two images and color image were fused into one image in RGB and HSI color space. Compared to original image, the fusion image contrast was enhanced, and was not influenced by the intensity, uniformity of illumination.更多还原