Research On Optical Path Design Method Of Fundus Camera Stereo Imaging System

Fundus examination is of great significance in clinical diagnosis.Thus,various instruments for fundus examination have been invented and used.Among them,the fundus camera has the characteristics of simple structure,visual images taken with a strong objective and a high reliability,so it has become one of the main instruments for the clinical testing on the fundus now.The fundus camera can only get the two-dimensional images,however,it was hard to establish a three-dimensional structure only according to the two-dimensional images,and the image data was not intuitive and dimensional.So the clinical diagnosis was mostly made by the doctor's clinical experience,and it was easy to get the mistaken diagnosis.In order to improve the scientificity and accuracy of medical diagnosis and treatment,fundus stereo camera is becoming an important breakthrough and key technology.Based on the physiological and optical characteristics of the human eye,the Gullstrand-Le Grand eye model is introduced to simulate the human eye with normal diopter.The Schematic eye model is used to examine the influence of the ametropia eye.All the optical components of the two kinds of optical systems are common spherical glasses,which are easy to manufacture and can reduce the production costs effectively.The works have been done by this dissertation are listed as following:(1)An optical system design of a portable fundus camera without mydriatic is designed.This design realizes the highly clear image with three mega pixels.In the imaging system,the objective lens is firstly used to converge the light emitted by the pupil from the retina of the human eye,then it is imaged to the CCD receiver by the imaging objective lens.In case of the stray lights caused by the cornea,the illuminating system with an annular aperture and coaxial illumination is specially designed.The result shows that the field of view of this system is 30°,the resolution is more than 1201p/mm,the field curve value is less than 0.11mm,the distortion value is only-1.1%,the chromatic aberration of all fields of view is within the airy disk.It comes to a conclusion that this fundus camera has strong focusing abilities,and adapts to different eyes from-10D to +10D.(2)An optical path design of the fundus stereo camera imaging system is proposed and designed in this dissertation.The images of the same retinal region can be captured from two perspectives simultaneously,and then restore the 3D space structure of the fundus so as to improve the diagnostic accuracy.In the imaging path,the retina is first imaged after the omentum objective lens and then projected to the common objective lens.Then the principle of the stereomicroscope parallel optical system is used to design the splitting optical system.Finally,two CCDs are selected as the receivers.In the illumination path,the cornea reflected light and the stray light generated by the omentum objective lens is eliminated by adding the annular aperture and the black dot plate.The result shows that the field of view of this system is 30°,the resolution is more than 1001p/mm,the field curve value is less than 0.09mm,the distortion value is-2.9%,the chromatic aberration of all fields of view is within the airy disk.It comes to a conclusion that the stereo imaging system has strong focusing abilities,and adapts to different eyes from-10D to +10D.