Objective design of dual-waveband endoscope with image fiber bundles

In order to meet the needs for circadian reconnaissance and target detection, a visible and near-infrared dual-waveband endoscope with image fiber bundles was designed . After analyzing basic principles, the telecentric optical system in image space with retrofocus type was selected as its initial structure. Through the optimization with ZEMAX, the results of wavelength, focal length, F number,field of view (FOV) and optical length were respectively 0.486 m～0.656 m/0.7 m～1.1 m,1.21 mm/1.22 mm,4, 80 and 8.45 mm/8.47 mm.As the filament diameter of image fiber bundles was 16 m, and it was arrayed as square, the optical system needed to be evaluated at 31 lp/mm. The results show the requirement of telecentric path in image space is satified completely. It has uniform illumination at image plane on axis and off-axis. The modulation transfer function (MTF) value of this system is greater than 0.81 at the spatial frequency of 31 lp/mm in visible part, which is 0.80 in near-infrared part. The design of this dual spectral endoscope makes the function of traditional endoscope realized, and also enhances the range of detection and amounts of information, which can achieve the measurement and observation in day and night.