Dual-band imaging system can effectively improve the detection and identification capability for airborne camera. To ensure the system with compact structure and without increasing the complication of the design, a catadioptric system is proposed as an alternative where the visible light and long-wave infrared (LWIR) share the mutual aperture and adding a dichroic beam splitter between the primary and secondary mirrors enables simultaneous imaging of the two bands. The common aperture is achieved by sharing a modified Cassegrain reflection structure in both bands. The entrance pupil diameter for the two bands is 148mm and their field of view (FOV) is 3°. The visible light works in the range of 0.5∼0.8μm and the focal length is 304.2mm with 2048×2048 detector, and the pixel size is 5.5μm. The LWIR works in the range of 8μm∼14μm and the focal length is 205.3mm with 1024×768 infrared detector, and the pixel size is 14μm. The system aberration is well corrected in two bands and for the performance analysis of the system in the temperature range of 20±5‡C, the design results can meet the requirements.
In this paper, a dual-band (visible light and SWIR) observation and imaging optical system is proposed. The system can acquire the optical characteristics of the target in the range of 900nm-1700nm by imaging. SWIR imaging not only can get the infrared characteristics of the target, but also has the ability of anti-camouflage and through-fog. It makes up for the deficiency of visible light imaging. The integrated system of visible light and SWIR can be widely used in military monitoring, forest fire prevention, geodesy and other fields, and has high practical values. The integrated system shares the front group of telescopic objective and shares the field of view. The visual observation system working in the visible band, the diameter of the entrance pupil is 24mm, the diameter of the exit pupil is 6mm, the distance of the exit pupil is more than 20mm, and the visual magnification is-4× . The SWIR imaging system working in 900nm-1700nm, and the diameter of the pupil is 24mm, and the focal length is 117.3mm. The field of view is for the two systems. The design and analysis results show that the system has dual-channel imaging of visible light and SWIR with common field of view, which can obtain clear visual images and digital images. The quality of the visual system and the imaging system meet the needs.
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