为满足对管道内壁快速检测的需求,设计了一种具有超半球视场的折衍混合环带式全景成像系统。该系统由环带全景成像(PAL)系统的头部单元和应用二元衍射面设计的中继透镜组成,各视场光线经PAL头部单元收束后再由中继透镜成像于电荷耦合器件上。二元衍射面的引入有利于改善成像效果、简化光学结构。对其衍射效率的进行理论分析,结果显示,二元衍射面的衍射效率在设计波段范围内不低于80%。设计的系统总长为97.836 mm,焦距为-4.537 mm,视场范围为360°×(45°~105°)。为保证弱光环境下的成像质量,取光圈数F为3,全视场调制传递函数在90 lp/mm处不低于0.5。设计结果表明系统具有良好的成像效果,可以满足管壁检测的需求。

To meet the demand for the rapid detection of the inner wall of a pipeline, a refractive-diffractive hybrid panoramic annular imaging system with a hyper-hemispherical field-of-view is designed. The system comprises a block and relay lens designed using the binary surface of the panoramic annular imaging (PAL) system. The light of each field-of-view is converged by a PAL block and subsequently imaged on CCD by the relay lens. The imaging quality can be improved, and the optical structure can be simplified by using the binary surface. The result of a theoretical analysis of the binary surface indicates that the diffraction efficiency of the binary surface is greater than 80% in design spectra. The total length is 97.836 mm, the focal length is -4.537 mm, and the field-of-view of the optical system is 360°×(45°-105°). Further, the F-number is 3, which ensures image quality in a low-illumination environment. The modulation transfer function of this system is no less than 0.5 at 90 lp/mm in all fields. The results demonstrate that the image quality is good. The optical system satisfies the requirements of the inner wall inspections of the pipeline.