Single Multimode Fiber Imaging

The access aperture of conventional fiber bundle imaging is relatively large,and its imaging resolution is limited by the number of single-mode fibers.Single multimode fiber imaging uses the optical interference and diffraction for imaging,which can significantly improve the imaging resolution while greatly reducing the access aperture of the endoscope,enabling high-resolution imaging of tiny objects.So research on single multimode fiber imaging has important practical application significance.With a single multimode fiber for imaging,the transmitted image is distorted due to severe modal dispersion inside the multimode fiber.This paper focuses on the recovery of distorted images and the main research contents and results are as follows:(1)Theoretically,the imaging process of multimode fiber is deduced.It is proved that the multimode fiber imaging system is a linear but spatial displacement system.Then,a method for recovering image distortion by using projection algorithm is proposed by measuring the impulse response relationship between the input point and the output point of the multimode fiber,combined with the distorted image information of the multimode fiber output.In view of the speckle illumination problem existing in the multimode fiber endoscope system,it is proposed to eliminate the influence of speckle illumination by using the double exposure method and improve the quality of the restored image.(2)The key technology of multimode fiber imaging,holographic imaging,is introduced theoretically,simulation and experiment.The original light information can be recovered from the hologram,and the accuracy of the holographic algorithm is verified.(3)Multimode fiber imaging experiments were implemented.The impulse response relationship of a multimode fiber imaging system was measured.Combined with the system impulse response and distortion image information,the original object light information is restored by using the projection algorithm,which proves that it is feasible to realize multimode fiber imaging.Then,the speckle illumination imaging experiment was implemented,which eliminated the influence of speckle illumination and improved the quality of the restored image.