基于投影机-摄像机结构的光照补偿技术综述

Radiometric Compensation Techniques Based on Projector-Camera System

随着投影机性能的不断提升以及计算机图形图像技术的不断发展,投影技术被应用到各种场合中,越来越多的日常表面被用作投影表面.通过适当的补偿技术,投影系统可以在几何结构不规则、反射条件不理想的表面上投射出接近于目标图像的画面.文中综述了近年来出现的基于投影机-摄像机结构的光照补偿技术.基于颜色混合矩阵的补偿技术使用少量的校正图案即可计算出系统的光照及反射信息,对于反射情况相对简单的应用可以进行高效的补偿,使系统实时稳定地输出几何、颜色无偏差的目标图像;在此基础上,使用同轴投影机-摄像机结构或者内嵌编码图像的方法进一步缩短标定所需时间,使得光照补偿技术可以扩展到移动投影系统的应用中.基于对目标图像预处理的相关优化技术可以在保证光照补偿精度的同时最大化地利用投影机的能量,尽可能扩大系统的动态范围.基于光线传输矩阵的补偿技术考虑了投影机-摄像机结构中的所有光照效应,采用相关的优化算法可以快速求取出系统光线传输矩阵的广义逆矩阵,以实时计算补偿图像;在此基础上,使用多通道投影系统可以有效地增加系统的分辨率,提高系统的动态范围,使得光照补偿技术可以应用到更多反射条件不理想的表面上.

With the increasing capabilities of the projectors and the development of computer graphics, projection techniques have been widespread. More and more everyday surfaces could be used for projection. Using real-time correction, images projected onto textured surfaces with arbitrary geometry can be as good as those projected on the optimized canvases. In this paper, the radiometric compensation techniques based on projector-camera systems developed in recent years are reviewed. Compensations based on color mixing matrix use only a few cali- brating patterns for recovering the light properties of the system. For applications with simple light effects, the surfaces could be compensated efficiently. Using fixed co-axial alignment or embedded structure light would fur- ther reduce the calibration time and make real-time mobile projection systems practical. Researches on adaptive compensation make the best use of light projected by the system so as to extend the dynamic range while keeping the imagery compensated accurately. Light transport matrix based algorithm takes global illuminations into ac- count, compensating images are calculated in real-time after solving the inverse light-transport out using con- strained optimization. Tiled projections are used to extend the dynamic range and increase the resolution, which makes projections onto radiometrically complex surfaces possible.