| The biological compound eye is a compact and precise photoelectric system with the characteristics of small size,light weight,large field of view,low aberration,high time resolution and sensitivity to moving objects.Inspired by these characteristics of the biological compound eye,the artificial bionic compound eye system came into being,and has been used in panoramic imaging,UAV obstacle avoidance,medical endoscope,robot vision,ranging and speed measurement Unmanned driving and military navigation and many other fields have shown broad application prospects.Close 3D imaging plays an extraordinary significant part in the field of microscope and UAV,because these fields need to capture small targets at high speed.With the progress of the times and the rapid development of imaging technology,the requirements for optical imaging systems become higher and higher.Previously,single-aperture optical systems can not any more satisfy the increasingly needs of the various walks of life,such as military target tracking and interception,industrial detection,micro wide-angle surveillance systems and other fields.In addition,the influence of diffraction astriction and other elements cannot allow to give a cold shoulder,Because the miniaturization and integration of single-aperture optical system is relatively more difficult,it is very necessary to design a multi-aperture optical system with small volume,light quality,large field of vision and high sensibility.In this paper,by using femtosecond laser twophoton polymerization processing technology and soft lithography replication technology,a flexible bionic compound eye with high accuracy and repeatability is prepared,which has five small eyes,and a single small eye is composed of a Fresnel lens.It is proved that the bionic compound eye can obtain high-quality images and can be used to track moving objects.The major substances are as below:1.The planar bionic compound eye was prepared by femtosecond laser two-photon polymerization processing technology.The photosensitive material suitable for femtosecond laser processing was successfully prepared by adding cyclopentanone to SU-8 photoresist at the ratio of 1:3;The affect of three arguments of femtosecond laser machining(laser power,exposure time,scanning step)on the shape and structural reconfigurability of a single small eye is systematically analyzed,so as to find out the best processing parameters;Under the optimal parameters,the controllable preparation of the plane bionic compound eye is realized by femtosecond laser processing;Laser scanning confocal and field emission electron microscopy(SEM)were used to characterize the structure and morphology of the plane bionic compound eye;A focusing and imaging device composed of charge-coupled device(CCD),objective lens and mask was designed and successfully built.The focusing test of the plane bionic compound eye and the imaging test of the letter F were carried out using the built device.The results show that the plane bionic compound eye has good optical characteristics.2.Preparation of flexible bionic compound eyes using polydimethylsiloxane(PDMS)soft lithography technology.A flexible material suitable for soft lithography was successfully prepared by mixing PDMS(refractive index 1.47)and crosslinking agent at a ratio of 10:1,stirring evenly,and vacuuming for 20 minutes in a vacuum box to remove air bubbles;Firstly,the planar bionic compound eye obtained in the previous step is subjected to a first soft lithography to obtain a PDMS inverse structure;In order to prevent the PDMS film obtained by the second soft photolithography from being difficult to peel off,we conducted surface fluorinated silane treatment on the PDMS reverse structure obtained by the first soft photolithography.Two drops of fluorinated silane were dropped on the template obtained by the first soft photolithography,placed in a culture dish and wrapped with a fresh-keeping film dozens of times,and then placed in an oven,heated at 95℃ for 5 hours for subsequent use;Using the PDMS reverse structure as a template,perform soft lithography and copying again,the steps being the same as the first time.Finally,dry the PDMS and peel it off to obtain a PDMS flexible bionic compound eye structure.To investigate the structure and morphology of the flexible bionic compound eye,laser scanning confocal microscopy and field emission electron microscopy were used to characterize it;Focusing and imaging tests were performed on the flexible bionic compound eye using the constructed optical path.Finally,real-time imaging detection of moving objects was performed using the flexible bionic compound eye.The results indicate that the flexible biomimetic compound eye has morphology and optical properties that meet the expected requirements,and has the ability to perform preliminary motion detection. |
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