Addressing the issue of computer processing in the internal spherical screen projection, an internal spherical screen projection algorithm was proposed based on virtual spherical transform and virtual fisheye lens mapping. Concerning the spherical screen output distortion caused by irregular fisheye projection, a sextic polynomial of distortion correction algorithm based on the equal-solid-angle mapping function was presented to approximate any fisheye mapping function to eliminate the distortion. The six coefficients of the polynomial could be obtained via solving a linear algebra equation. The experimental results show this method is able to completely eradicate the spherical screen projection distortion. Addressing the illumination distribution modification stemming from the spherical screen projection, an illumination correction algorithm based on the cosine of the projecting angles was also proposed to eliminate the illumination distribution change. The experimental results show the illumination distribution correction method successfully recovers the originally severely modified illumination distribution into the illumination distribution almost identical to the original picture. This algorithm has theoretical instructive importance and significant practical application values for design and software development of the spherical projection systems.

%U http://www.joca.cn/EN/10.11772/j.issn.1001-9081.2014.03.0810