Reflective optics is used widely in optical systems for their achromatization, large aperture and lightweight compared with refractive systems. An infrared four-mirror optical system with large relative aperture working in the 7.7～10.3 micron long wavelength infrared band is designed by using four reflective mirrors. The design principle, design results are described in this paper. The system has a circinal wide field of view with 1.5°×1.5°. The MTF of the system is diffraction-limited and the distortion is less than 1.0%. The ratio of focal length to total length is about 1/1.04,so the structure of the system is compact. The image quality is evaluated for each field, which shows that the design makes a good system with high image quality.
Surface deformation is the crucial factor for the imaging performance of the lithographic object lens in the manufacturing process. Simulation of surface deformation can predict the degradation of the wavefront error caused by surface deformation, find the lens which is most sensitive to the surface deformation even in the design phase. We develop a method to simulate the surface deformation by Zernike polynomials in this paper. In fact, the surface deformation generated in the manufacturing process is random. However, it does not mean that they have no rules at all. We analysize the Zernike coefficients distribution of the interferential data, and build a model to simulate the surface deformation. The model can generate random-surface-deformation according to the input RMS/PV bound in the form of INT file type, which can be added to the lens surface directly in the optical design program CODEV. The results show that the surface deformation generated by our model can simulate the interferential data very well.