Design And Research Of Eccentric Photographic Vision Screening Instrument

Refractive dysfunction is an eye disease,which is a very common and serious hazard to visual function development.At present,the National Health and Family Planning Commission,the Ministry of Education and other departments attach great importance to the prevention and control of myopia in children and adolescents,and stipulates that should be included in the government performance appraisal indicators.Because of the requirement of existing refractometer needs the closed compliance of patient,it is not suitable for children and other groups with a low compliance.Besides,complicated optical path and large contour lead to low portability.In order to solve these problems,the design of a non-contact portable vision screening device is proposed,which presents the objective optometry accurately and quickly for human eyes at the distance about one meter away,which has the great significance in the application of national visual survey.The vision screening device designed in this paper is based on the principle of eccentric phototherapy to present the optometry of the patients' eyes.According to the overall design of the equipment,the optical imaging module,light source module and image processing module of the system are designed and studied.First of all,in order to solve the low contrast of the received image caused by the long-range optometry,which affects the accuracy of the photographic optometry,an imaging optical system for eccentric photographic vision screening instrument is designed by using ZEMAX optical software: According to the lens requirements and related parameters,an eccentric photographic imaging optical system with focal length of 47.6mm,a field of view of 9 degrees,relative aperture of 1/2.8,and the working band of 850 nm is designed,and its image quality analysis and tolerance analysis are carried out.The imaging effect match the usape requirements;Then,the light source module is designed,which includs selection of the light source type and the design of the light source array in the light source module according to the optometry theoretic calculation and the requirements of the optometry detection.The design theory results can measure the diopter of human eyes from-8D and +8D.Secondly,the measurement of diopter is realised by using image processing algorithm,which includes real-time tracking of the human eye's regions,the precise positioning of eye's pupils,the judgment of the direction of the human eyes.The refractive information of the human eyes obtaining through image processing technique.The optometry results include the spherical degree,the cylindrical degree,the astigmatic axial position,the strabismus degree of the human eyes,and the distance between the pupils of the human eye,etc.Finally,eccentric optometry experiments on standard model eyes with diopter between-6D and 0D is carried out in this thesis.The large amount of experimental data obtained approximately fit the optometry equation and verifies that the optometry error of the equation is less than ±0.5D through experiments.The future goal is to complete a non-contact portable eccentric photographic vision examination machine for the patients with a low compliance.