Optical system design of dual band CCTV fish-eye lens

According to the use requirements of closed circuit television (CCTV) lens, a dual band CCTV fish-eye lens based on the principle of non-similar imaging was designed. This system works in the wavelength range of 480 nm~850 nm, with the dual band imaging of visible light and near-infrared light, which could realize day and night monitoring. The F-number is 1.8, the field angle is 180º, the focal length is 1 mm, and the total optical length is 7.76 mm. The lens has the characteristics of large relative aperture, large field angle and miniaturization. The system adopts 7 groups of 9-piece anti long distance structure, without special glass and aspheric surface, which greatly reduced the complexity of the system and the manufacturing cost. The optical design software Zemax was used to design its optical system, selecting the 1/3 inch CCD as the detector. When the Nyquist frequency is 120 lp/mm, the values of meridional modulation transfer function curves and the sagittal modulation transfer function curves of each field of view are more than 0.5, close to the diffraction limit, and the imaging quality is good. The field curvature of the whole field is less than 1 mm, the relative distortion is less than 25%, and the relative illumination is about 95%, which meet the use requirements of CCTV lens, and can be widely used in monitoring and reconnaissance fields.