Infrared Telephoto Design Used in Joint Transform Correlator

摘要

In order to meet the requirement of tank sight and improve the ability of Joint Transform Correlator(JTC) in target detection and recognition, the infrared telephoto system with high image quality and high performance-price ratio is designed for wavelength 8μ～12μm. Initial structure is composed of four refractive lenses. The focal length is 200 mm, the relative aperture is 1:2.6 and image field of view is 1 inch (CCD). Considering the fabrication process, production cost and other factors, the system structure is further improved. First the telephoto which is composed of four lenses is designed with normal spherical surface. Then on the basis of the original spherical structure, an aspheric surface is introduced. The optical system can be reduced into three lenses. The image quality of the whole system becomes much better. The optical system image quality is evaluated with ZEMAX optical design software. The result shows that MTF of each field is close to the diffraction-limited curve at the cut-off frequency 17lp/mm. The spot diagram RMS radiuses are smaller than the radius of Airy disk 25.35μm. The wave front aberrations for all the fields are less than 0.25λ. The telephoto can meet the requirement of target detection. Combining JTC with this infrared telephoto lens, the infrared target at longer distance can be detected and recognized.