基于各向异性点光源的近场光度学三维重建问题研究

项目名称： 基于各向异性点光源的近场光度学三维重建问题研究

项目编号： No.61773363

项目类型： 面上项目

立项/批准年度： 2018

项目学科： 自动化技术、计算机技术

项目作者： 宋展

作者单位： 中国科学院深圳先进技术研究院

项目金额： 16万元

中文摘要： 现有的光度学三维重建方法为简化法向模型的求解问题，多采用平行光或远距离点光源假设，然而对于各向异性点光源条件下的近场光度学三维重建问题，目前尚缺乏系统而深入的研究。在本项目中，我们首先将光源自身发光模型引入到光度立体视觉框架中，通过综合考虑光源特性、入射光夹角、出射光线的角度及距离衰减等多种因素，对非标准点光源下的光照场进行精确建模。通过所提出的标定方法获取光源位置及主光轴方向等关键参数，根据光照场模型和系统标定参数建立任意场景点的光照条件数学模型，计算出每个点的初始入射光方向和强度。由于初始模型中包含未知距离参数，研究中拟基于初始三维重建结果采取迭代优化策略对相关参数进行优化，提高最终的法向场重建精度。通过本研究的开展，进一步完善了非标准点光源条件下的近场光度立体视觉方法理论框架，基于普通LED点光源组成的光度学系统实现高精度的三维重建，为低成本三维信息采集提供了一种新的方法和技术手段。

中文关键词： 光度立体；三维重建；光源标定；光照模型；法向恢复

英文摘要： Conventional Photometric Stereo (PS) methods usually adopt the assumption of parallel or distant point lighting conditions, so as to simplify the procedure of surface normal calculations. However, for the PS systems with nearfield non-isotropic point light sources, the reconstructed surface normal maps are usually lack of precision subject to the inhomogeneous lighting conditions. In this proposal, a novel PS framework is investigated for the accurate 3D reconstruction from nearfield non-isotropic point light sources. Major research contents and contributions are generalized as follows. The first research work is to establish an accurate lighting model for the adopted non-isotropic point source. Compared with conventional PS lighting models that only consider the incident light direction, the radiance model of light source is also considered in the proposed lighting model. To calculate the incident light intensity for each surface point more precisely, both the angular and distance attenuations are considered. The second research work is about the system calibration. Compared with conventional point light-based PS methods that only need to determine the position of light source, both light source position and principle optical axis of light source should be precisely calibrated in the proposed PS framework. To calculate the light source position, traditional multi-sphere-based method can be used. To determine the principle optical axis of light source, a reference plane-based method is proposed in this work. With the system calibration parameters and the proposed lighting model, for each surface point, its lighting condition can be fully determined. And the primary 3D model can be reconstructed via classical surface integration procedure. The last research work is to optimize the parameters in the primary lighting model. Based on the primary obtained 3D model, an iterative optimization procedure is introduced to improve the precision of lighting model with respect to the unknown distance factor. With above researches, a new framework for non-isotropic point light source-based PS systems can be established. And more accurate 3D model can be obtained based on a rather simple PS setup, which only consists of some single LED as light source and one camera. It provides an accurate and low-cost technical means for wide 3D acquisition applications.

英文关键词： Photometric stereo;3D reconstruction;Light source calibratino;Light model;Surface normal reconstruction