Design Of Infrared Dual-waveband Coaxial Projector Objective Based On DMD

When the temperature is above absolute zero, all the objects produce infrared radiation. Detecting and reorganizing the target is based on the infrared radiation of the object. The main working mode of infrared system is passive. It accepts the infrared radiation of target itself emitting or reflecting from another source. The advantage is good for hiding and no electronic interference from enemy. Thus the infrared technology is widely used in military field. It provides a strong technical support for the warning, detection, air defense and guidance. With the development of infrared technology, the Image tracking guidance gradually replaces the point source tracking guidance. The technology of the Image tracking guidance gets the information of the target and background through optical mechanical scanning and infrared detector. Than processed and analyzed the information, it could automatically track and the attack targets.But currently the vast majority of infrared seeker only works for single-band. The infrared detectors received information obviously insufficient when environment is harsh and background is complex or a pseudo target existed.It affects the detected and reorganized the target. With the development of the infrared focal array plane, it could respond two wavebands at the same time have come out. It is possible to develop the dual-band infrared imaging guidance. The performance testing of dual-band seeker has also become a focus of research. The traditional flight test at outside not only needs a high cost and more time, but also has a low accuracy and gets the data difficultly. Therefore, the dual-band infrared scene generator is developed for dual-band infrared seeker has a great significance.According to the characteristics of dual-band seeker, the research of dual-band scene generator combined with the principle of infrared imaging is conducted. This paper completed the following work:(1)The basic knowledge of infrared optical system is studied. It includes the dual-band infrared imaging guidance technology, the development of scene generation technology, the structure and working principle based on DMD.DMD is the core device of the dual-band infrared scene generator.So it has been studied significantly. It is discussed and described the problem of DMD what needs improvement used in infrared dual-band scene generator.(2) The principles of zoom system are described. It is compared and analyzed the zoom system what has different ways of compensation mode. According to its characteristics and the system design requirements, the appropriate zoom compensation mode is selected. It is prepared for the zoom system design that discussed the zoom equations of mechanical compensation zoom system based on the Gaussian optical theory.(3) The structure of infrared optical system is described.Compared with the three structures; we can get the advantages and disadvantages. Then the design uses a refractive co-axial structure. The design difficulty of the infrared dual-band coaxial optical system is correct the dual-band aberration and get the prefect image quality of dual-band at the same time.This paper describes theprinciple of dual-band chromatic aberration and how to correct various aberrations of infrared optical system. Then we get the key of corrected the dual-band aberration.The principle of diffraction and the asphericalelement is discussed.lt provides theoretical support for simplified the system structure and correctedthe aberrations(4) The design parameters and indicators of Infrared Dual-band of optical projection lens is determined according to the requirements of infrared sense generation. The infrared dual-waveband coaxial projection lens is designed used the Zemax software. The working waveband is3-5μm and8-12μm. The focal length is200mm. The F-number is2.8. At cut-off frequency17cy/mm, the MTF of the infrared medium-wave is greater than0.7for each field of view, and MTF of the infrared long-wave is greater than0.4for each field of view. The root mean square radius of spot diagram for the each field of view is much smaller than airy disk radius. The wave-front aberration meets the Rayleigh criterion. The image quality of this projector objective is perfect and meets the design requirements. Finally, the design results were normalized to meet the processing requirements.(5)Based on the infrared dual-waveband coaxial projector objective, infrared dual-waveband coaxial two step zoom projector objective is designed in order to realize the requirements of simulated different sizes target. The working waveband is3-5μm and8-12μm. The focal length range is50-200mm. The F-number is3. At cut-off frequency17cy/mm, the MTF of the infrared dual-wave is greater than0.3for each field of view.The root mean square radius of spot diagram for the each field of view is much smaller than airy disk radius. The image quality of this projector objective is perfect and meets the design requirements. Finally, the design results were normalized to meet the processing requirements.(6) Finally, the tolerance analysis is conducted for all the results of design. It proved the result is feasible.