Design And Test Of Press-on Prisms For Micro-structures Of Children Strabismus Compensation

In recent years,press-on prisms which adopt Fresnel prism structure has been widely used during the adjuvant treatment process of children strabismus compensation.However,many challenges about domestic fabrication of press-on prisms still remain.In this paper,the so-called hard cover press-on prisms which made from polymethyl methacrylate(PMMA)material is chosen as the study subjects.And both theoretical and experimental research about hard cover Press-on prisms has been done in this thesis,including the design and simulation of the structure of the press-on prisms,dispersion compensation method for high degree press-on prisms and the testing system for the diopters of press-on prisms.The main works of this thesis can be summarized as follows:Firstly,the device structure of the hard cover press-on prisms was designed according to the binary optical diffraction method,and the influence of PMMA material and quantization order on the dispersion effect has been simulated and analyzed by MATLAB.Theoretical analysis results show that the light transmittance is about 95% when adopts PMMA material with refractive index of 1.492.In addition,the diffraction efficiency gets higher as the number of quantization order increases.The maximum quantization order can be 100 theoretically.Moreover,the geometrical optics design software ZEMAX is adopted to make simulations for evaluating the performance of micro-structural optics and the aberration results has been discussed in details.Secondly,a novel dispersion compensation method is developed by means of adopting the micro-structure prism array.This method is suitable for press-on prisms with high diopter.The main optical performance indexes such as dispersion,transmittance,ray fan,spot diagram and diffusion function graph of the proposed method are simulated by ZEMAX.Simulation result shows that 83% of the points are distributed inside the airy spot ring in the spot diagram which indicates that the micro-structure prism array has achieved significant dispersion compensation effect.In addition,the available width of the refraction unit is in the range between 600 um and 800 um,and the available unit width of micro-structure prism array is in the range between 15 um and 20 um.Thirdly,a photoelectric detection system which composed of helium-neon laser,photoelectric detector and large size vernier caliper is designed to make measurement about the press-on prisms diopter.Press-on prisms whose diopters range between 0.5 △ and 30 △ are divided into three groups named low diopter group,medium diopter group and high diopter group.Samples of press-on prisms with different diopters are tested in the system.Experimental results show that the tolerance of low diopter group is ± 0.05,and the tolerance of medium diopter group is ± 0.10,and the tolerance of high diopter group is ± 0.15.It is verified that the designed testing system for the diopter of press-on prisms achieves high accuracy and it meets the demands for testing diopter of press-on prisms in actual fabrication process.