Research On Refractive/Diffractive Hybrid Dual Field-of-view Optical System For Uncooled Infrared Thermal Imager

The infrared thermal imaging technique has been widely applied in military affairs and civilian engineering. Relaying on its advantages such as needless refrigeration, small volume ,lightweight, lower dissipation, high reliability and lower cost, the uncooled infrared thermal imager(UITI) plays an increasingly important role in the fields of the infrared thermal imaging system.Infrared optical system is an important component in UITI. The image of targets and background in field-of-view is imaged in infrared detector by optical system,then is switched corresponding electrical signal. After the signal processing by image recognition and image software, it is showed as hot image at the display. At the time of track, thermal imager hopes that with long focus length and little field for the track distance and precision, but at the time of capture and observe, it hopes that with short focus length and big filed. The fixed-focus lens system can not meet the request, and that the continuous zoom system has lots of difficulties, for example designing, lightweight, lower cost,cold shield matching, designing and machining of cam. So in this paper, a dual field-of-view optical system is adopted, it preferably accomplish the capture, track and the system's simple, practical and lightweight.Research on dual field-of-view optical system of UITI in this paper. Firstly, we introduce the development of infrared thermal imaging technique, the advantages and broad application prospects of UITI, analyse the research progress of uncooled dual field-of-view optical system and diffractive optical lens' application at home and abroad, expound the basic theory of infrared thermal imager. Secendly, we study the characteristics of monochromatic aberration, dispersion and temperature. we use diffractive optical element in fixed-focus infrared optical system,design an achromatized and lightweight optical system for UITI and a thermalized midwave infrared optical system in the working temperature range -50℃～100℃. Then we design exchange manner and axial motion manner dual field-of-view optical lenses for UITI with the help of ZEMAX optical design software. At last researched the three compensating methods of athermalization technology for infrared optical system, made a comparison of their advantages and disadvantages respectively and athermallize for two dual field-of-view optical lenses.