Design method of dual-band synchronous zoom optical system based on co-path zoom groups

•In this paper, we propose a design method of a dual-band simultaneous zoom optical system based on the co-path zoom groups, which has the advantages of synchronous zoom (During the process of synchronous zoom, the focal length of the dual bands is the same), compact structure, and high-precision fusion of dual-band images.•To solve the problem of difficulty in obtaining initial structure, we propose an optimization method for initial structure calculation of dual-band synchronous zoom optical systems. This method has guiding significance for optical system design and greatly improves the success rate of optical system design.•By using secondary imaging group to compensate for residual aberrations in the second band, a zoom ratio of approximately twice can be achieved, making the structure of the dual-band zoom optical system more compact and the zoom structure simpler and more reliable.