Design method for zoom systems based on magnification ratio modulation of afocal off-axis three-mirror anastigmat systems

Achieving higher resolution and larger zoom ratio is one of the primary goals of zoom optical systems. To this end, we propose a new zoom configuration that combines a modulatable magnification off-axis three-mirror system with a zoom system to expand the zoom ratio of the system. Since the afocal reflective system can easily achieve large optical apertures, this approach is more conducive to meeting the long focal length and high-resolution performance requirements of zoom systems. In this study, through theoretical analysis of the zoom equation, guided by the need to adapt the pupil matching of the combined zoom system, we derived the configuration equations of the off-axis three-mirror afocal system with the exit pupil position as the boundary condition. We established a zoom optical system design method based on a modulatable magnification ratio off-axis three-mirror subsystem. According to the design concept, theoretical analysis, and design method, we provided two high-resolution long focal length zoom system design schemes with a zoom ratio of 12× by applying an off-axis three-mirror afocal system with zoom ratio modulation ranges of 4×-6×-8×, combined with a 1.5× mechanical compensation zoom system. The achieved zoom ranges are 399 mm-4896 mm and 399 mm-4893 mm, respectively. The results of this study provide a novel approach for achieving high-resolution, large zoom ratio systems.