Research On Human Eyeball Multi-parameter Measurement Technology Based On Laser Self-mixing Interference

The eye is the most important sensory organs of the human body,and the cornea and anterior chamber are very important components.In surgery such as vision correction,it is necessary to accurately know the corneal thickness and anterior chamber depth of the human eye.Therefore,its accurate measurement can not only provide a reference for doctors,but also provide a strong guarantee for the surgical results.In order to achieve high-precision measurement of human corneal thickness and anterior chamber depth,an equivalent human-eye optical system and measurement method of the thickness were studied.The research content of this article is as follows:Firstly,this paper studies the theory of self-mixing interference analyses the working principle of it by researching the three-mirror cavity model.Laser irradiates externally reflecting objects and the reflected light returns to the laser cavity and the original light self-mixing interference,photo-detector collect interference signals and process them to obtain the referring information of surface of the object.At the same time,various modulation methods of laser are also studied in this paper.Secondly,by studying the optical structure of the cornea and the anterior chamber,this paper designs two equivalent model including equivalent cornea system and equivalent double membrane system in order to simulate the optical structure of human eye.Then,a method that measuring the thickness of cornea and the depth of anterior chamber has been studies based on self-mixing interference theory.By analyzing the power peak of the self-mixing interference signal,the final measurement result is obtained.Modulating sine wave signal for laser constant current power supply,and counting the statistics of the number of saw-tooth waves in the self-mixing waveform after modulation,the absolute distance from the laser to the surface of the human eye is obtained.Finally,building the experience system,and modulating the optical status by using optical lens group.Through the measurement of different lens groups,the correctness of the laser self-mixing interfering method for measuring human eye parameters is verified,and the measurement accuracy can reach the micron level.