激光线扫描超广角共聚焦眼底成像

Ultrawide-Angle Confocal Laser Line Scanning Fundus Imaging

为了对眼底周边部区域进行成像检查,研究了激光线扫描眼底成像技术。搭建了激光线扫描超广角共聚焦眼底成像系统,进行了系统总体光路设计,以及超广角、高分辨双模式成像的参数设计。对探测成像部分进行了Zemax设计与像质评价,依据参数进行了元器件的选型并搭建了实验系统,利用面阵相机像素边界得到了虚拟共聚焦狭缝,实现了眼底线扫描双模式共聚焦成像。最后对系统的实际视场角、分辨率、成像效果进行了评估。经实际测量,所设计系统在超广角模式下成像单幅眼底图的视场角可达到136.3°,高分辨模式下的成像分辨率为8.5μm。所提出的激光线扫描眼底成像方法可以有效地实现眼底超广角成像,为相关仪器的研制提供了参考。

Objective In all blind eye diseases,fundus disease remains the primary cause of irreversible visual loss,significantly impacting visual acuity.In severe scenarios,this results in a higher prevalence of blind fundus disease.Many fundus diseases manifest in the eye periphery.If the lesion does not affect the macular area,patients often overlook early lesions since their visual acuity remains largely unchanged,presenting no symptoms.During examinations,standard fundus-imaging equipment fails to visualize the peripheral area of the fundus due to its limited imaging field of view.Once the lesion impacts the central macular area of the fundus,treatments become challenging,and outcomes are generally unfavorable.As such,early examinations play a crucial role in preventing and treating fundus diseases,underscoring the need to innovate instruments that image the retina,encompassing the fundus periphery.Traditional fundus photography has a field of view limited to 30°‒50°.Even utilizing multi-region fundus image stitching only marginally expands the fundus imaging area,concentrating the imaging on the posterior pole.Conversely,laser scanning confocal fundus imaging offers superior clarity and contrast,enabling non-mydriatic fundus imaging even in patients with constricted pupils and facilitating real-time dynamic observations of fundus image changes.Ultrawide-angle fundus imaging rooted in laser scanning confocal imaging emerges as a significant advancement in fundus imaging.We anticipate that our alignment method and study findings will inform the design of cutting-edge ophthalmic examination devices.Methods To thoroughly image the peripheral area of the fundus,we explore the fundus line-scanning imaging technology and construct an ultra-wide-field confocal laser line-scanning fundus imaging system.Initially,we devise a comprehensive optical pathway for the system.For achieving ultra-wide-angle,high-resolution dual-mode imaging,it is essential to design the geometrical optical parameters of the components within the respective mode,ensuring that the parameters satisfy the dual-mode imaging requirements simultaneously.We commence by establishing the overarching framework of the optical system,which incorporates the parameter design for ultra-wide-field,high-resolution dual-mode imaging.This is followed by Zemax simulations and image quality optimization for the system detection and imaging sections.Components are chosen based on these parameters,leading to the construction of the experimental system.By utilizing the pixel boundaries of the target surface in the area camera,we are able to achieve line scanning dual-mode confocal imaging of fundus through the creation of virtual slits.Once the theoretical design phase concludes,we employ Zemax software to simulate the system detection optical path,optimize this path,and validate the system design metrics and viability.The camera pixel boundary forms a virtual confocal slit,facilitating line scanning dual-mode confocal imaging of the fundus.We then assess the actual field of view of the system,resolution,and imaging capabilities.Results and Discussions The designed laser line-scanning ultrawide-angle confocal fundus imaging system in this study realizes ultrawide-angle,high-resolution dual-mode imaging by simply switching the eyepiece lens(Fig.1).After parameter design and simulation(Table 1),the commercially available lenses for scanning,lighting,and imaging objectives fully meet the system requirements,reducing the system design cost.In the ultrawide-angle mode,the system actual field of view reaches 136.3°,achieving ultrawide-angle imaging(Table 3).In the high-resolution mode,the system equivalent conversion fundus resolution stands at 8.5μm,accomplishing high-resolution imaging(Fig.9).We conduct ultrawide-angle mode imaging,ordinary fundus camera photography,and high-resolution mode imaging on the simulated eye,and the system dual-mode imaging effect proves significant(Fig.10).Conclusions This study offers a method for achieving ultrawide-angle confocal imaging of the fundus based on line scanning.The system employs a Powell prism in conjunction with a cylindrical lens to produce an ultra-long and ultra-fine laser line beam.It utilizes the pixel boundary of the camera target surface to establish virtual slits,achieving confocal fundus imaging.This effectively diminishes the interference of non-focal plane stray light on the fundus image.The system possesses both an ultra-wide-angle fundus imaging mode and a high-resolution imaging mode.Theoretical calculations and experiments indicate that the field of view in the ultrawideangle mode is 136.3°,and the actual resolution in the high-resolution mode is 8.5μm.Grounded on the experimental results,the proposed laser line-scanning fundus imaging method proves feasible.It effectively achieves ultrawide-angle fundus imaging and serves as a reference for the development of related instruments.