Abstract. We propose a method to estimate the surface normal of concave objects. The target object of our method has a specular surface without diffuse reflection. We solve the problem by analyzing the polarization state of the reflected light. The polarization analysis gives a constraint to the surface normal. However, polarization data from a single view has an ambiguity and cannot uniquely determine the surface normal. To solve this problem, the target object should be observed from two or more views. However, the polarization of the light should be analyzed at the same surface point through the different views. This means that both the camera parameters and the surface shape should be known. The camera parameters can be estimated a priori using known corresponding points. However, it is a contradiction that the shape should be known in order to estimate the shape. To resolve this problem, we assume that the target object is almost planar. Under this assumption, the surface normal of the object is uniquely determined. We show that the surface normal of the nonplanar part can also be estimated using the proposed method.

中文翻译：

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从多视偏振角度估计凹镜面物体的形状

摘要。我们提出了一种估计凹面物体表面法线的方法。我们方法的目标对象有一个没有漫反射的镜面。我们通过分析反射光的偏振态来解决这个问题。极化分析对表面法线施加约束。然而，来自单个视图的偏振数据具有模糊性，并且不能唯一地确定表面法线。为了解决这个问题，应该从两个或多个视图中观察目标对象。然而，光的偏振应该通过不同的视图在同一表面点进行分析。这意味着相机参数和表面形状都应该是已知的。可以使用已知的对应点先验地估计相机参数。然而，为了估计形状而应该知道形状是矛盾的。为了解决这个问题，我们假设目标对象几乎是平面的。在这个假设下，物体的表面法线是唯一确定的。我们表明，也可以使用所提出的方法估计非平面部分的表面法线。