Design Of Key Components Of Compact Zoom System

Zoom system refers to the optical system and optical imaging by changing the focal length of the optical system to achieve continuous optical zoom,which can achieve continuous imaging of targets with different object distances.With the development of optical instruments,zoom lens has been widely used in many fields.Zoom system has wide application and development potential in video surveillance,electronic equipment and detection,such as: smart phones,virtual reality technology(VR),augmented reality technology(AR)and other new applications.At present,with the development trend of the optical system towards miniaturization and flattening becoming more and more obvious,the traditional zoom system is gradually unable to meet the actual demand,and the new compact zoom system will become the leading research hotspot.Based on the basic theoretical model of scalar diffraction,this paper introduces the common theoretical model of scalar diffraction and three common diffractive optical elements,such as zone plate,photon sieve and multi-step phase diffraction elements.According to the design characteristics and requirements of compact zoom key devices in this subject,scalar diffraction model can be selected to analyze the focusing light field of the key devices in the zoom system.Based on the basic principle of realizing continuous zoom with lateral displacement,a flat phase band plate with adjustable focus and a composite photonic screen diffraction element with adjustable focus are presented.The main research contents of this paper are as follows:The development and research status of optical zoom system are analyzed,and a detailed review is given.Starting from the traditional longitudinal zoom system,the basic principles and methods of optical zoom are summarized.Then,the advantages and disadvantages of active zoom,multi-camera zoom and transverse zoom are compared and analyzed,and it is concluded that the combination of transverse zoom mode and diffraction element is beneficial to the compact zoom system.A combination wave plate phase zoom diffraction element with transverse modulation is studied.At first,the design method of phase plate is introduced,and the simulation results show that the effective modulation of transverse zoom can be realized,and the ratio of 5 times to 5 times can be guaranteed.In this paper,based on the composite photonic screen,a kind of photonic screen diffraction device which can realize transverse modulation zoom is proposed.The zoom function of the device is proved by simulation results.In view of the focusing characteristic,it is compared with the phase band plate,and finally the phase band plate scheme is selected.In order to verify the focusing performance of the device,based on the spatial light modulator,a semi-physical simulation experiment device was built,and the zoom capability of the device was verified through the image acquisition results.In addition,the alignment error of zoom element in actual assembly is discussed in detail,and the allowable error range is obtained,which is instructive for the assembly of the device.The equivalent dispersion model is established and the position chromatic aberration of the zoom element is evaluated.