Research On Image Transmission Performance Of Spherical Fiber Bundle

The fiber optic plate(FOP)is a large area-array rigid passive optical fiber image transmission device composed of millions of optical fibers.Its most important advantage is that it can achieve one-to-one image transmission on input and output end faces of different shapes.The most representative application of the FOP is as a relay image transmission device of a monocentric optical camera to solve the problem that the hemispherical focal plane of the monocentric objective lens cannot be coupled with the planar image sensor.At the same time,multiple FOPs can realize large-format imaging with hundreds of millions or even billions of pixels through specific spatial layout.However,due to the loss of the FOP in the image transmission process and the discrete sampling characteristics of the FOP's own structure,the introduction of the FOP will inevitably cause the image quality of the monocentric optical camera to decrease.Therefore,in the context of space-based space target surveillance,this paper conducts a systematic theoretical derivation and simulation experiment research on the three FOP image transfer performances,including centroid positioning accuracy,modulation transfer function,and detection signal-to-noise ratio.Exploring the degree of influence of FOPs with different parameters on the above-mentioned image quality factors,by selecting appropriate FOP parameters,it will be possible to reduce the image quality loss caused by the addition of FOPs.The main research work is as follows:(1)A two-stage two-dimensional discrete sampling coupling model of "monocentric objective lens hemispherical focal surface-FOP-image sensor photosensitive surface" was established,and a centroid positioning accuracy based on fiber-coupled relay imaging system was proposed.It is concluded that by controlling the parameters of the FOP,the centroid positioning accuracy is maintained at the order of 0.03 pixel,and the loss of centroid positioning accuracy caused by the introduction of the FOP is reduced.The relative initial position between the FOP and the image sensor caused the decrease in centroid positioning accuracy to be almost the same and maintained within 0.01 pixel.(2)Established a modulation transfer function model based on FOP.The mechanism of the influence of fiber diameter,fiber core diameter ratio,fiber arrangement and spherical end face on the modulation transfer function of the FOP is explored.It is concluded that when the fiber diameter is smaller and the fiber core diameter ratio is smaller,the modulation transfer function of the FOP is higher,and it is mainly determined by the fiber diameter,and the influence of the fiber core diameter ratio is weaker.Under the same fiber parameters,the modulation transfer function of the FOP with the fibers arranged in a regular hexagon is better than the modulation transfer function of the FOP with the fibers arranged in a square.(3)Established a detection signal-to-noise ratio model based on optical fiber relay image transmission system.The mechanism of the influence of the FOP on the detection signal-to-noise ratio of the monocentric optical camera is explored,and the transmittance of the FOP is the main factor affecting the detection signal-to-noise ratio,and the specific degree of its influence on the detection signal-to-noise ratio is analyzed.It is concluded that increasing the transmittance of the FOP can slow down the decrease of the system detection signal-to-noise ratio and the increase of the threshold detection signal-to-noise ratio.When the transmittance of the FOP is greater than 0.5,the detection signal-to-noise ratio of the system is greater than 3 to meet the requirements of the project.This article aims to explore the influence mechanism of the FOP on the centroid positioning accuracy,modulation transfer function and detection signal-to-noise ratio of the three optical fiber panel image transmission performance,provides some guidance for the selection of the actual FOP,but also for monocentric optical cameras The overall performance improvement has laid a solid foundation.At the same time,the research in this article can also be used as a reference for other discrete image transmission devices.