新型眼底相机的设计与研制

	新型眼底相机的设计与研制
	李灿
学位类型	博士
导师	孙强
	2014-07
学位授予单位	中国科学院大学
学位专业	光学工程
摘要	眼底相机不仅可以针对常见的白内障、青光眼等眼科疾病检查，而且可早期诊断高血压、糖尿病等全身系统性疾病，已经成为临床医学和现代科学研究的热门对象，然而人眼像差、杂散光和鬼像以及光学系统结构是影响其成像质量的主要因素。本论文针对人眼像差的校正，基于模块化设计思想设计并研制一种三次成像光路的眼底相机；针对杂散光和鬼像以及光学系统结构，提出两种新型眼底相机光学系统结构；为扩展眼底的层析成像功能，设计并研制一款谱域OCT设备。研究内容包括： 1、为实现对不同屈光度人眼像差的同时校正，提出一种基于Gullstrand-Le Grand标准眼的离焦眼模型，模拟眼底相机真实使用环境，可同时保证各个调焦光路对人眼像差的校正。 2、为提高成像光路对人眼像差校正的成效性，采用分步、模块化的光学像差补偿方式，保持成像光学系统各部分的独立性，且压缩了系统的口径，降低系统的设计和装调难度；三次中继转像系统可满足不同放大倍率的调整，而且可以完成谱域OCT功能模块的切换；采用环形照明方式和黑点板的使用消除角膜和网膜物镜反射光带来的杂散光和鬼像；双光楔定位和调焦投影光路保证眼球的定位和人眼屈光度的补偿。基于这种模块化设计思想，设计并研制一款三次成像光路的新型眼底相机，工作距离为40mm，视场角为45°，调焦范围为－10D到+6D，物方各视场分辨率达到10~15μm，畸变小于6.5%。 3、为解决传统眼底相机杂光和鬼像的控制问题，基于离轴两反式自由曲面网膜物镜，设计一款折反式眼底相机光学系统，具有大视场和大工作距离。设计离轴反射式网膜物镜，可彻底避免网膜物镜带来的中间反射光，省掉照明光路中的黑点板，使系统不再存在中心遮拦和鬼像；成像物镜中采用两个自由曲面对网膜物镜的剩余像差进行校正；照明光路中使用三个相邻的环形光阑，以避免眼球屈光介质表面反射的杂散光。 4、相比传统眼底相机复杂的光学结构，提出一种紧凑型眼底相机光学系统，结构更加简单、紧凑。系统的成像和调焦投影光路共用调焦镜，调焦投影光路被完全嵌入到照明光路，调焦投影光路不再专设照明组件，而且避免了投影目标和调焦镜之间的机械联动结构；LED光源窄带宽的优势，可以近红外观察和可见光成像过程共用一个相机。 5、针对目前眼底成像检查的发展趋势，设计并研制一台谱域OCT设备，采用全光纤迈克尔逊干涉仪结构搭建谱域OCT系统，基于快速光谱仪并行探测得到光谱干涉信号，通过三次样条插值、数据拟合和傅里叶变换等信号处理方法重建样品的深度分布信息，并且利用平均光谱法提高OCT图像的信噪比。最终完成对珍珠、新鲜果肉和人体皮肤等典型的生物组织和散射样品进行成像研究。
其他摘要	The eye fundus examination is significant not only for diagnoses of eye diseases (such as cataract, glaucoma etc.)，but also for very early clinic diagnoses of diseases that influence the retina (such as hypertension, diabetes, nephropathy etc. ). It has become a hot study of clinical medicine and modern science. However, there are three main factors influencing the imaging quality, the eye’s aberrations, the undesirable scatter light and central ghost, and the complicated optical system. Based on the idea of the modular design, a new style of fundus with cubic imaging optical system to aid for the eye’s aberrations is designed and developed in this thesis. For the undesirable scatter light and the complicated optical system, two new optical systems of fundus camera are designed. Spectral domain OCT equipment is designed and developed to expand on tomography function of fundus. 1. In the optimization of the imaging system, a new eye model with varying defocus revised from Gullstrand-Le Grand standard eye model was introduced to eliminate the negative effect of eye’s aberrations as well as to accommodate the eye with different refractive error. 2. To improve the effectiveness of the correction of eye’s aberration in the imaging optical path and to keep the independence of each part of the imaging optical system, we choose the way of step-by-step and modular optical aberration compensation mode. Aperture of the system is compressed to reduce the system's difficulty in design and alignment. The cubic relay image system can meet the requirement of different magnification and complete switch of the spectral domain OCT function module. The backreflections of the cornea and ophthalmic lens can be avoided in the way of the annular illumination and the black pot. The location and diopter compensation of eye are completed by the double optical wedge positioning system and the focus target projection optical system. Based on the idea of the modular design, a new style of fundus camara with cubic imaging optical system is designed and developed, with the field of view of 45°, the free working distance of 40mm, the accommodation range between -10D and +6D, the resolution at the object plane of 10~15μm across the entire field of view and the maximum distortion less than 6.5%. 3. In order to eliminate the undesirable stray light such as scatter light and central ghost in a classical fundus camera, the optical system of a catadioptric fundus camera with an off-axial reflecting free-form-surface ophthalmic lens was designed, which is with a large field of view and a large working distance. The off-axial reflecting ophthalmic lens is introduced to avoid backreflections of refractive ophthalmic lens without black pot in the illumination pathways. Two free-form-surfaces were introduced in the imaging objective system to correct the residual off-axial aberrations of the reflective ophthalmic lens. Three adjacent illumination rings were introduced in the illumination part to avoid the undesirable stray light reflected by the eye’s optical system. 4. A new type of portable fundus camera was designed to make the optical system simpler and more compact as compared with the classical system. The photographing system and the focus target projection optical system are with a common focusing lens, so that the focus target projection optical system can be arranged completely in the illumination system. In the focus target projection system a special illumination system is not required any longer. In addition, a focus link mechanism between the projective target and the focusing lens is not required. The position of the focusing lens makes the space of the photographing system. Taking the advantage of narrow bandwidth of LED light source, the observation system and the photographing system are with a common camera. 5. In view of the current development trend of fundus imaging check, the spectral domain OCT equipment is designed and developed. SD-OCT system is built by use of all-fiber Michelson interferometer structure. The spectral interference signal is collected by a fast spectrometer; the reconstruction of depth information is completed by the signal processing method of cubic spline interpolation, the data fitting and Fourier transform, and the signal-to-noise ratio of OCT image is improved by the average spectrum method. Finally, the OCT images of biological tissue and scattering samples of pearl, fresh fruit and human skin have been obtained.
语种	中文
文献类型	学位论文
条目标识符	http://ir.ciomp.ac.cn/handle/181722/41422
专题	中科院长春光机所知识产出
推荐引用方式 GB/T 7714	李灿. 新型眼底相机的设计与研制[D]. 中国科学院大学,2014.

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