Miyazaki Daisuke, Uegomori Kazuya
Graduate School of Information Sciences, Hiroshima City University, Hiroshima 731-3194, Japan.
J Imaging. 2022 Apr 11;8(4):107. doi: 10.3390/jimaging8040107.
A photometric stereo needs three images taken under three different light directions lit one by one, while a color photometric stereo needs only one image taken under three different lights lit at the same time with different light directions and different colors. As a result, a color photometric stereo can obtain the surface normal of a dynamically moving object from a single image. However, the conventional color photometric stereo cannot estimate a multicolored object due to the colored illumination. This paper uses an example-based photometric stereo to solve the problem of the color photometric stereo. The example-based photometric stereo searches the surface normal from the database of the images of known shapes. Color photometric stereos suffer from mathematical difficulty, and they add many assumptions and constraints; however, the example-based photometric stereo is free from such mathematical problems. The process of our method is pixelwise; thus, the estimated surface normal is not oversmoothed, unlike existing methods that use smoothness constraints. To demonstrate the effectiveness of this study, a measurement device that can realize the multispectral photometric stereo method with sixteen colors is employed instead of the classic color photometric stereo method with three colors.
光度立体法需要在三个不同光照方向下依次拍摄三张图像，而彩色光度立体法只需要在同一时间以不同光照方向和不同颜色照亮的情况下拍摄一张图像。因此，彩色光度立体法可以从单张图像中获取动态移动物体的表面法线。然而，传统的彩色光度立体法由于彩色照明而无法估计多色物体。本文使用基于示例的光度立体法来解决彩色光度立体法的问题。基于示例的光度立体法从已知形状图像的数据库中搜索表面法线。彩色光度立体法存在数学困难，并且添加了许多假设和约束；然而，基于示例的光度立体法不存在此类数学问题。我们方法的过程是逐像素的；因此，与使用平滑约束的现有方法不同，估计的表面法线不会过度平滑。为了证明本研究的有效性，采用了一种能够实现具有十六种颜色的多光谱光度立体法的测量装置，而不是具有三种颜色的经典彩色光度立体法。
