Near-infrared Fundus Camera Design

Fundus camera has the characteristics of simple structure, visual images taken with a strong objectivity and a high reliability, so it has become one of the main instruments for the clinical testing on the fundus of eyes now. With the development of modern science, the fundus camera has been given a new application and mission, as the Ophthalmology & Optometry requesting higher standards on the fundus imaging.In this paper, the near infrared light source is selected for illumination and imaging of the fundus of eyes, on the basis of understanding the basic principle of fundus camera and combining with the structure and optical properties of human eyes. Then, it is established the model of the paraxial optics path for fundus imaging, by using of the theory of Optics about the ideal object-image relationship, and calculated the movement of the zoom lens when imaging the different diopter eyes(-10D～+10D) in the internal zoom manner. From the varying-focus curve, it can be seen that the movement of the zoom lens is nearly linear. Finally, the imaging path of the fundus camera is simulated in ZEMAX with the LIOU eyes. It meets the imaging requirements basically, with the depth of field is 120μm, and the resolution is nearly about 7μm.It is analyzed and solved the factors that can affect imaging quality in illumination path, and obtained the paraxial optics path of the illumination path by calculating. Then, the illumination path of fundus camera is built in ZEMAX.At last, on the basis of the design about the fundus camera completed, it is tested plates and analyzed tolerances for all of the lenses, then drawn the optical elements according to national standards for processing.