In order to improve the remote target detection ability of infrared (IR) images effectively, an infrared telephoto objective for 3μm~5μm and 8μm~12μm dual wave-band is designed for 640 pixel×512 pixel infrared CCD detector. The effects of the surrounding environmental temperature are analyzed and the refractive diffractive hybrid thermal compensation is discussed. The focal length of the system is 200mm, the relative aperture is 1:2.2 and the field of view is 7°. The infrared dual band telephoto system with small volume and compact structure is designed in a large range of temperature. The system is composed of four lenses with only three materials of zinc sulfide, zinc selenide and germanium to compensate for the temperature. The image quality of the system is evaluated by ZEMAX optical design software. The results show that the modulation transfer function (MTF) for each field of view at cut-off frequency of 17 lp/mm are respectively greater than 0.6 and 0.4 which approaches the diffraction limit. The telephoto objective has favorable performance at the working temperature of -40°C~+60°C. The relative aperture, field of view, and focal length are same for both spectral regions. The system meets the requirements of technical specification.
Ultraviolet warning technology is one of the important methods for missile warning. “Solar blind region” provides a very effective way to detect the target for missile approaching alarm. In order to find the target by detecting the ultraviolet radiation of missile efflux plasma, ultraviolet optical system design of large field of view and large relative aperture is the key for the technology of ultraviolet detection. From the academic point of view, the structure parameters are determined for 2048×2048 ultraviolet CCD detector according to the requirements of ultraviolet warning system. The refractive ultraviolet warning optical system is designed for 0.24μm ~0.28μm wave band with ZEMAX optical design software. The focal length is 41mm, the field of view is 46°and the relative aperture is 1:3.5. In order to ensure the detected energy, aspherical and binary surface are adopted to reduce the aberration and spot size of the system. Within the 0.8 field of view RMS of spot diagram is less than 13μm. It is smaller than the pixel size 13.5μm of ultraviolet CCD. The energy concentration is more than 80%. This optical system has long focal length and large relative aperture that meet the energy requirements of warning system. Large field of view can satisfy the range of searching targets. The spot diagram RMS of each field of view is so small that can meet the requirement of image quality. In addition, the system is composed of six lenses. The structure of it is simple, the volume is small and the application is very convenient.
On the basis of optical correlation detection, photoelectric hybrid joint transform correlator(JTC) is widely used in military, aviation and intelligentization, etc. It has the advantages of great flexibility and high precision of recognition. However, the optical system which is in front of joint transform correlator(JTC) is applied to receive the infrared radiation of the target. It also has a certain influence on JTC’s detecting precision and tracking ability. Dual band infrared imaging system can receive different wave band of infrared radiation. Therefore, the image quality of optical system plays an important role in the joint transform correlator(JTC). According to the requirements of the joint transform correlator (JTC), the processes of optical design including the allocation of parameters and the selection of initial structure are presented. The infrared dual band coaxial telephoto system is designed for target detection. The system which is composed of four lenses can image in both 3μm~5μm and 8μm~12μm wavebands. The focal length is 200 mm and the relative aperture is 1:3. The system has the characteristics of small volume and compact structure. The optical system image quality is evaluated with ZEMAX optical design software. The results have shown that MTFs of the system are 0.62 and 0.35 for both wavebands respectively at 17lp/mm of spatial frequency which are closed to the diffraction limited curve. The relative aperture, field of view, and focal length are same for both spectral regions. The system meets the requirements of technical specification and improves the ability of JTC in target tracking and recognition.