Optical system design of solar-blind UV target receiver with large FOV

Abstract

Ultraviolet (UV) radiation of 200nm-300nm waveband from the sun is absorbed by atmosphere, which is often referred to the solar-blind region of the solar spectrum. Solar-blind characteristics of this waveband have important application value in forest-fire prevention, UV security communication, UV corona detection and other aspects. Especially in military fields such as missile warning, the application of solar-blind waveband has developed very rapidly, which is receiving more and more attention recently. In this paper, ZEMAX software is used to design an optical system of solar-blind UV target receiver with waveband 240nm-280nm, with which UV target signal can be detected. The optional materials are very few for UV optical systems to choose from, in which only CaF2 and JGS1 are commonly used. Various aberrations are not easy to be corrected. So it is very difficult to design a good UV system. Besides, doublet or triplet cannot be used in UV optical system considering possible cracking for different thermal expansion coefficients of different materials. So the doublet in initial structure is separated for this reason. During the optimization process, an aspheric surface is used to correct the aberrations. But this surface is removed before the design is finished to save production cost and enhance the precision of fabrication and test, which still keeps the image quality meeting the usage requirements. What we care for is the converging condition for different field of view from the far object on image plane. So this is an energy system. Spot diagram is taken as the evaluation criterion of image quality. The system is composed of 6 lenses with field of view (FOV) 31 degrees. In the final design results, the root mean square (RMS) radius for marginal FOV is less than 6.3 microns, while the value is only 4 microns for zero FOV. Point Spread Function and diffraction encircled energy diagram within the maximum FOV confirms the good performance of system further.