Study On Multi-fousing Bionic Compound Eye Imaging System

With the continuous improvement and development of micromachining equipment and technology,the preparation and application of micron-size optical devices have become an important research field,and optical imaging systems are also heading toward miniaturization,integration and high performance.Inspired by the compound eye structure of natural arthropods,scholars at home and abroad focus on the bionic compound eye imaging system.Compound eye imaging system has the characteristics of small volume,multi-channel,wide field of view,which not only can observe various signal,and make quick response to a moving object,but also according to the received signal differences between each ocellus to calculate the target space position.This makes the compound eye system has a great application prospect in space navigation,monitoring,security,medical monitoring,information extraction,and other fields.In recent years,researchers have proposed many designs and fabrication schemes of bionic compound eye imaging systems,some of which can achieve excellent imaging performance but rely on complex fabrication techniques or large system volume.Adopting multi-focal compound eye and plane image sensor as the imaging system structure design,easy to realize miniaturization of integration,which greatly reduces the difficulty of the preparation of assembly system.It's still a problem achieving high accuracy and rapid preparation of compound eye,which makes the bionic compound eye imaging system hard to realize the practical application of miniaturized integration.In order to meet the practical requirements of miniaturization and integration of bionic compound eye imaging system and large field of view imaging,this paper studies the design of multi-focal length structure of the imaging system,the preparation of multi-focal microlenses,the technology of surface replication and transfer,and the stitching of multi-image with large field of view.In this paper,a design method of multifocal curved compound eye and a preparation method combining contactless and elastic mold transformation are proposed to complete the small-volume packaging and integration of the bionic compound eye imaging system,which meets the requirements of real-time target capturing and synchronous image stitching.The specific research work of this paper is as follows:1)It's difficult to make the the miniaturization in the integration of bionic compound eye imaging system with rapid preparation and small volume,this paper proposes a multi-focus compound eye structure design,on the basis of not adding other optical structure,multi-focal compound eye achieving the curved compound eye directly with commercial plane image sensor directly adapted.Constraint conditions of related parameters were set,and the key and difficult points of preparation were pointed out.Then the method to improve the imaging quality of the system and to evaluate its performance was studied,and a complete test platform for compound eye performance was built.2)This paper proposes a microlens array preparation method based on the contactless hot embossing to meet the requirement of compound eye design for curvature accurate controlled within a certain range,precise control of microlens curvature during hot embossing process is from the research of polymer rheological mechanism and non-contact hot pressing process,the effects of process parameters on lens shape.By setting the filling height of polymer,the problem that the curvature of high precision lens can not be obtained by using pressure difference and imprint time control lens forming is solved.Based on this method,a precise and controllable ocellus with a focal length of 0.16mm?6.25 mm was prepared,and the lens height of 15?m ?30?m was consistent in the diameter of 100-400 mm.It is suitable for the precise and rapid preparation of multi-focal compound eye.3)For multiple focal length compound eye in surface shape,surface curvature controllable and child eye morphology transfer molding replication precision requirements,proposed the elastic mold transfer model,the differential assisted molding surface transfer copy method,and through the experiment of curvature radius of controlled within the range 15 mm to 100 mm,and replication biggest child eye diameter deformation rate is less than 4.2%.The precise and controllable surface transfer and copying molding is realized.Based on this method,a multi-focal compound eye with a curved surface curvature of 16.5 and a sub-focal length of 0.23mm?2.09 mm was prepared,and a matching image sensor was selected to complete the preparation of a bionic compound eye imaging system.The maximum resolution of the system was14lp/mm,and the field of view angle reached nearly 110°.4)In view of the focal length of the bionic compound eye imaging system eye image stitching problems,research of the current mainstream of several kinds of feature points extraction algorithm,different algorithms are analyzed.Because the principle and characteristics of feature points are extracted from the feature points extraction is the optimal size,rotation invariance SIFT algorithm,and adopted the RANSAC algorithm to optimize key points matching accuracy.Fade in and out fusion methods is used to reduce gaps and color brightness differences between the images.The imaging system is also calibrated preliminarily,and the preliminary exploration is made for the realization of 3D target detection in the future.Finally,the structure packaging and program packaging of the bionic compound eye imaging system are completed,and the functions of real-time target shooting and synchronous image stitching are realized,but the volume is only 29.01mm×29.18mm×43.46 mm.