High resolution middle infrared continuous zoom optical system with large zoom range

For advanced 640 512 cooled staring focal plane array (FPA) detector, a mechanical compensation continuous zoom optical system with greater than 30zoom range was presented based on the requirements of infrared thermal imager. The zoom system provided continuous changed in the field of view from the narrow field of view to the wide field of view. The largest constraint that used to exist developed a strategy that would allow the zoom focus to be continuous. The large zoom range created the condition of the zoom groups moving through the 1magnification case. Discontinuities about this 1magnification point was well documented in the paper. The spectral band of the system was 3.7-4.8 m, and F number was 4.0. It realized 15-550 mm continuous zoom with a smooth zoom path and provided high image quality within the whole zoom range. Moreover, detailed design and image quality were given by CODE V optical design software. By the virtue of secondary imaging structure and tow reflectors, it has 100% cold shield efficiency and can reduce the transverse and radial size of system. The design results prove that the zoom system has high resolution, large zoom range, small size and excellent image quality and has also been found to be capable of accommodating advanced infrared thermal imager.