| Due to the unique transparent dioptric medium of the eyeball,the retina is the only tissue in the human body that can be observed in vivo.Microhemangiomas formed by early lesions of cerebral arteriosclerosis,diabetes and other diseases appear on capillaries with a diameter of about 5μm,and the resolution of the traditional fundus camera used in clinical practice is about 15μm～20μm,and doctors cannot use it to distinguish the early symptoms of fundus diseases.Balancing the requirements of high-resolution,large field of view,low cost and high universality,this paper designs a compact high-resolution retinal adaptive optical imaging system,and the corresponding imaging optical path map is built on the optical platform of the laboratory to realize high-resolution imaging of the simulated human eye.The details are as follows.First of all,the basic structure,transmittance spectrum,reflectance spectrum,and blood absorption spectrum of the human eye are investigated.Considering the safety of fundus lighting and the characteristics of light sources,and selecting asuitable light sources for detection,imaging and staring at the optogram,which lays the foundation for the design of fundus adaptive optical imaging system.Moreover,the Navarro eye model that can reflect the adjustment ability of the human eye was selected for subsequent design,the characteristics of human eye aberration are summarized and analyzed,and the ability of laboratory voice coil deformation mirror(DM-69)to correct human eye aberration is theoretically and experimentally analyzed,and the results confirmed that the voice coil deformation lens can be used to correct the low and high order aberrations of the human eye.Thirdly,based on the requirements of human eye aberration characteristics and its wavefront distortion range,the solution space of the Shack Hartmann detector wavefront parameters suitable for human eye aberration measurement are constructed according to six constraints,such as maximum spot size,spatial resolution and dynamic range.In the existing domestic microlens array,the appropriate microlens array parameters are selected,and Zemax and Matlab software are used for simulation,and the results show that the Shack Hartmann detector wavefront sensor parameters can detect human eye aberrations well,and the detection area is large enough.Finally,this paper designs a retinal imaging camera that can automatically adjust,which mainly consists of illumination subsystem,detection-imaging subsystem,optotype staring subsystem and pupil alignment subsystem.The detection-imaging subsystem proposes to replace the traditional annular diaphragm with an axial pyramid lens set,the annular beam produced by the axial pyramid lens group has no central obstacle,and the doctor can control the inner diameter of the annular beam by adjusting the distance of the axonoid lens to suit the corneal size of different human eyes.The introduction of Badal focusing system can initially correct the defocus caused by different eye diopters,which is convenient for the deformable mirror to better correct high-order aberrations and obtain clearer images.Zemax software is used to simulate the designed system,and the results show that the illumination distribution of the light source at the retina is uniform.The imaging subsystem can image vision cells of about 4μm with high resolution.The MTF value is stable,and in 90% cases,MTF@25lp/mm>0.21.The sight-beacon sighting subsystem uses the object-side telecentric optical path,which can theoretically reach the fundus imaging range of 18° through the imaging region guided by the sight-beacon.The AO fundus imaging system is built in the laboratory,and the pupil alignment subsystem could image the real pupil,which could verify whether the subject’s eyes are placed in the proper position and height.The PV and RMS detected by Hartmann decrease from 16.845μm and 8.135μm before correction to 1.43μm and0.225μm after correction,the resolution of the image branch is obviously improved. |
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