Design Of Fresnel Aperture Imaging Based On Lensless Imaging Technology

Lensless imaging technology is a technology that directly uses photodetectors for imaging.He can replace the camera lens to a certain extent.The essence of lensless imaging is to use digital image processing to extract visualization from some optically encoded original images.Useful information.Without a lens,the image sensor only records the average light intensity of the scene,but the lensless imaging method can restore the image based on the sensor's measurement results.The advantage of lensless imaging is that it replaces the traditional optical lens,making the imaging system more compact,which is conducive to the miniaturization of the optical imaging system.This article is based on the Fresnel aperture imaging design of lensless imaging technology.The proposed Fresnel aperture imaging method can directly restore the image from the measured value of the photodetector with the help of the image reconstruction algorithm.The key to the Fresnel aperture imaging system is the design of the Fresnel aperture and the design of the image reconstruction algorithm.First,the light emitted by the object passes through the Fresnel aperture just a few millimeters in front of the detector,and the light encoded by the Fresnel aperture is projected onto the image sensor to form a shadow image that cannot be recognized by the human eye;The original image data is superimposed on a virtual Fresnel aperture with a specific angle deviation from the real Fresnel aperture during computer image processing to form moiré fringes;the moiré fringes can be separated using the fringe phase scanning method Signal component and noise component,at the same time,this paper also developed a secondary scanning method based on the fringe phase scanning method,the extracted signal component is more accurate;finally,the extracted signal component is subjected to two-dimensional discrete Fourier transform and zero Frequency adjustment,and then use the geometric mean filter to remove noise and histogram equalization can reconstruct the target image.In this paper,simulation analysis and system test of Fresnel aperture imaging system are carried out.According to the simulation of single point source and the simulation of pictures,the feasibility of Fresnel aperture to realize lensless imaging is analyzed,which provides theoretical and algorithm guarantee for the subsequent experiments.On the existing basis of the laboratory,a Fresnel aperture infrared imagingsystem was built,and its imaging characteristics were analyzed,such as Minimum imaging distance,imaging range,imaging effect,etc.,and factors affecting imaging were also discussed.On this basis It has been optimized to effectively improve the imaging quality of the system.The experimental results show that the lensless imaging using the Fresnel aperture imaging system has achieved certain results,and its infrared imaging effect is obvious,which provides a new reference for the miniaturization and integration of infrared detectors.This technology will have huge application potential in the fields of Internet of Things,astronomy,biomedicine and other fields in the future.