成像式亮度测量数码相机色彩空间转换矩阵选择  

Selection of digital cameras' color space conversion matrix as an imaging luminance measurement device

作　　者：易斌[1] 甄江龙[1] 袁韬[1] 米红菊[1] 

机构地区：[1]后勤工程学院机械电气工程系,重庆401311

出　　处：《电子测量与仪器学报》2015年第3期427-432,共6页Journal of Electronic Measurement and Instrumentation

摘　　要：利用数码相机作为成像亮度测量装置获取亮度分布,较传统的点式亮度计更为便捷高效。分析数码相机成像流程数码相机成像流程及色彩空间转换算法,对比按不同输出图像色彩空间制式下的转换矩阵公式求得的计算亮度误差,证明了依据相机输出图像色彩空间制式选择色空间转换矩阵的必要性。为提高测量精度,提出利用D55标准照明体色度坐标作为参考白点,修正色空间转换矩阵。实测结果表明,采用色域更广的Adobe RGB色彩空间输出图像,较sRGB格式测量精度更高。将参考白点色坐标值以D55标准照明体,代替D65标准光源对转换矩阵计算式加以修正后的测量误差有所改善,实测亮度相对误差均方根值RMSE分别为6.65%(sRGB)和3.10%(AdobeRGB),样本最大相对误差值εmax分别为10.71%(sRGB)和5.01%(AdobeRGB)。其精度可满足工程测量要求。Using digital camera as an imaging luminance measurement device （ ILMD ） can obtain the luminance distribution in the field of view by once photographing, it is more convenient and efficiency than conventional spot sighting luminance meter.The calculated value of the Y tristimulus or gray scale was strongly related to color space conversion between RGB and XYZ , and the chromaticity coordinate of the primary colors and reference white point . The color workflow of the imaging luminance measurement device was examined with emphasis on which ‘standard’ RGB color spaces is appropriate.Four transformation matrix formula of RGB to Y, which were applied in common color spaces： sRGB, Adobe RGB 1998, PAL and NTSC, are compared.The experimental results show that formu-las applied in sRGB and Adobe RGB were preferred to those applied in PAL and NTSC color space , and the RMS and maximum error of the calculated luminance utilizing the HDR image synthesized with the wider gamut Adobe RGB images is 4.21% and 13.09%, compared with 7.76% and 10.47% of which synthesized with sRGB ima-ges.The measurement accuracy has improved when using the standard illuminants D 55 as the reference white point to calculated the color space conversion matrix instead of the standard illuminants D65.And the RMS and maxi-mum error was 6.65% and 10.71% （sRGB）, 3.10% and 5.01% （Adobe RGB） ,respectively.

关 键 词：成像式亮度测量 色彩空间转换 高动态范围图像 数码相机 

分 类 号：O432.2[机械工程—光学工程] TH741.4[理学—光学]