Stray Light Analysis And Suppression Of Panoramic Annular Lens

Panoramic Annular Lens (PAL) is a special lens with super large Field of View (FOV). It projects a cylindrically panoramic view of360°around the optical axis to an annular area on a plane. Because of its miniature and convenience, PAL is applied to many areas, such as military, medical and monitoring.But, when there is a highlight source in the field of a panoramic annular lens, the image will be covered by stray light like mist. So it is important to suppress stray light in a PAL system.In this dissertation, firstly the basic principle of PAL system is introduced, then researched into the basic knowledge of stray lights in optical systems.After that, we give an overall stray light analysis of a PAL system. Stray lights can be divided into five categories, while the one caused by incomplete transmission of refractive surfaces is the main source of stray lights in a PAL system. A suppression method is proposed, based on which a new PAL system is designed. A comparison of stray light performance is conducted in ASAP between an ordinary PAL system and the new PAL system, in order to verify the feasibility of this method. The result indicates that in half field angle of50to85°, stray light caused by incomplete transmission of refractive surfaces reduces85%in the new PAL system, what’s more, stray lights caused by while incomplete transmission of refractive surfaces is no longer in the new PAL system,and stray light does not increase in other fields of view. That means the suppression method can effectively suppress stray light caused by incomplete transmission of refractive surfaces in a PAL system.