To solve the problems of low and non-uniform resolution in catadioptric omnidirectional imaging, a novel omnidirectional sensor of complementary imaging structure is designed, by using two reflecting mirrors. Each spatial object has two imaging positions, respectively in the inner and the outer ring of captured omnidirectional images. The uniformity of resolution distribution is obviously improved due to complementary double imaging, and higher spatial resolution is achieved by limiting the vertical field of vision in a narrow range for some specific applications, such as military remote surveillance. Computational methods of the shape parameters and sizes of two mirrors are described in detail, and the mapping relations between omnidirectional image plane and cylindrical panoramic space are accurately derived based on ray tracing. Experimental results show that remarkable complementarities exist between the inner and outer ring of omnidirectional images, and detailed analysis of resolution distribution is presented. Moreover, sub-pixel sampling displacement between two image positions provides essential preconditions and foundations for further research on super-resolution reconstruction of cylindrical panoramic space.