Research On Digital Detection Method Of Corneal Curvature And Pupil Diameter

The cornea and pupil are one of the most important structures of the human eye.According to the size of corneal curvature,not only the refractive power of human eye can be determined,the astigmatism of human eye can be determined,and some guiding suggestions can be provided for wearing contact lenses.In addition to being the basis for discriminating eye diseases,the size of the pupil diameter can also indirectly reflect the physiological and psychological changes of the human body.Therefore,accurate detection of two parameters of human eye is of great significance.Aiming at the measurement error caused by the design defects of the existing corneal curvature and pupil diameter measuring device in the projection objective and the determination of the distance from the apex of the cornea to the target ring,this paper proposes a digital detection method.The method is based on the principle of imaging detection,the projection objective is designed as a double telecentric light path to ensure the stability of the magnification,and an interference ranging technique is introduced to measure the distance from the apex of the cornea to the target ring in real time.combined with digital image processing technology enables accurate measurement of corneal curvature and pupil diameter simultaneously.According to the overall scheme,we had designed and simulated a target loop device and a double telecentric projection lens.And we had completed the overall design,key device selection and the construction of the experimental platform of interferometry ranging.By using the image processing technology we had extracted the coordinates of the target ring on the human eye image and recognized pupil edges.The developed prototype was calibrated with standard eyes and standard circles,then the prototype was tested and the theoretical accuracy of the test method was estimated.The results show that the measurement range of the radius of curvature of the cornea is 5.5-11 mm,and measurement accuracy reached ±0.017 mm,the measurement range of the pupil diameter is 2-8mm,and measurement accuracy reached ±0.05 mm,which better than the measurement standards of the AQSIQ.