Study Of Optical Design For An Infrared Detection System

In recent years, owing to the rapid development of science and technology, particularly due to the technical progress, appeareance of new materials and perfection of manufacturing methods of the infrared (IR) detectors, more and more IR systems have been applied in both military and civilian fields . In the military field, IR detection systems are widely used for early warning,reconnaissance,target tracking and aiming equipments etc, and are effective for battles in night and for low-detection targets, thus are unsubstitutable in morden war. In the civilian field, infrared detection systems are widely used in electric power supervision and management,medical diagnosis,safety protection in key areas etc. In the"SARS"period of 2003, IR detection equipments were used of monitoring and measuring body temperature, which may remain fresh in our memory.The IR optical system is an important part of an IR detection system. It's function is to collect IR radiation from both the target and the background, then accumulate and focus it on the photosensible surface of the detector in order to form images of the target and the background. With the keeping upgrading of IR detectors and requirements for IR detection systems based on a variety of applications getting higher. Higher requirements for IR optical systems have been put forward in terms of performance and designing optimization.In this paper, IR detection systems for early warning are summarized, and the theories of IR optical systems and diffractive optical elements are introduced. Designing methods of IR optical system are also studied. In the end, an IR optical system used for IR detection systems for early warning is designed and optimized with optical design software. Some important research works are as follows: (1) The effects of environment temperature on IR optical systems are analyzed. The principle and design method of employing diffractive optical element to athermalize and achromatize an optical system are expounded. The DOE is applied in athermal design for IR systems.(2) An IR optical system whose performance approaches the diffraction limit is designed, working at 8μm~12μm, and at normal temperature. Then the system is optimized to work at the temperature ranging from -20℃to 60℃.(3) The image quality of the optical system is evaluated making use of modulation transfer function(MTF). A performance comparison is done between conventional refractive optical system and hybrid optical system, showing that the hybrid optical system has obvious advantages in terms of image quality, volume, weight, environmental adaptability over the conventional refractive optical system.