Imaging characteristics of ball lens

A proof-of-concept gigapixel computational camera consisting of a spherical lens shared by several small planar sensors has been reported recently. Because the resolution of spherical lens is fundamentally limited by geometric aberrations, the imaging characteristics of the ball lens are expressed by the geometrical aberrations, in which the general equations for the primary aberration of the ball lens are given. To achieve high quality imaging, the effects of lens shape, stop position, and glass material on the aberrations are discussed, respectively. The third-order and the fifth-order spherical aberration as a function of lens shape and the relative aperture are analyzed as well. The other imaging evaluation merits, such as the spot diagram, the modulation transfer function(MTF) and the encircled energy are also described.