Research On Muti-aperture Imaging System Based On Freeform Surface

Multi-aperture imaging system is a new imaging system based on natural compound eyes and micro-lens array as the main imaging component.Due to its unique imaging principle,the multi-aperture imaging system has a wide field of view,small size and compact structure,and has wide applications prospects in medical imaging,motion detection,and miniature cameras.In a multi-aperture imaging system,different imaging channels are responsible for imaging different fields of view,and channels responsible for edge field of view imaging often face problems that aberrations are difficult to control.Due to its complex and variable surface shape,freeform surfaces are easy to achieve deflection and clear imaging of beams incident at large angles.At the same time,with the maturity of ultra-precision fabrication of complex surface,such as ultra-precision turning and replication technology,it has become possible to batch-process microlens arrays based on freeform surfaces.In this paper,based on the design requirements of large field of view,the multiaperture imaging system with non-overlapping field of view between different channels is taken as the research object.The introduction of freeform surfaces into the design and optimization of microlens arrays is proposed to improve the imaging performance of multi-aperture imaging systems.And the processing of the multi-aperture system according to the design results is completed to verify the actual imaging performance of the system.The main work of this paper is as follows:(1)Based on the design requirements and in order to reduce the processing and assembly difficulty of the system,a multi-channel imaging system with single-layer freeform surface lens array,three-dimensional stop array and detector as the main structure is proposed.(2)The design of the multi-aperture imaging system with the channel number of 3×3,the field of view of 48°×48°,the working band of 8-11μm and the sub-channel F number of 2.5 is completed.The optimized MTF curve for each imaging channel is close to the diffraction limit.According to the size of the beam of the imaging beam at the specified position,the specific size of the three-dimensional stop array is determined.(3)The imaging simulation of the multi-aperture imaging system including freeform surface lens array,three-dimensional stop array and detector is realized by ray tracing.(4)Finally,the mold of the freeform lens array was machined using a single point diamond turning method,followed by final processing of the lens array using compression molding techniques.A stop array was fabricated using a 3D printing method.According to the imaging principle of multi-aperture imaging system,an imaging test platform was built,and the imaging test and image quality evaluation of the system were completed.