The Design And Evaluation Of Space Dual-band Tri-focus Optical System

With the development of science and technology, Leo satellites are widely used in resource exploration, weather forecasting, topographical mapping, military reconnaissance. In observations to the ground, observing different objectives requires different optical systems, which need to design a variety of different optical systems, not only a waste of resources, but also taking up a lot of space.Visible system can work only in environment with external lighting. In the absence of light or weak light, it is very hard to achieve the desired target information, while infrared imaging systems can work as usual in night. Visible light systems and infrared optical systems have their own advantages and disadvantages. The complement of each other will get a better result, which means viewing a good condition with visible systems, observing with an infrared system in night work. Effective cooperation can improve the speed and efficiency of observation.To solve these problems, a space dual-band Tri-focus optics is designed in this paper by sharing primary mirror. For visible light system with long focal length and short focal length, in the whole field of view, at the Nyquist frequency(42 lp / mm), all MTFs are larger than 0.5. For LWIR system, the MTF reaches the diffraction limit. The imaging quality satisfies the design requirements. The suppression of stray light in the visible long focal length subsystem, the visible short focal length subsystem and the LWIR subsystem is good enough, and satisfies the requirements. Analysis proves that the LWIR subsystem’s own heat radiation can be ignored. Compared with conventional dual-band systems, the design of this system has smaller size and lighter weight, and can realize the space observation in 400~850nm å'Œ 8~12μm spectra.Stray light can affect a system’s color reduction ability, causing the fall of colorful images’ saturation. The suppression of stray light and coating proper optical reflection reducing films can help to improve the system’s color reduction ablity.