Design Of2Degree-of-freedom Head Prop In Adaptive Optics Retinal Imaging System

Adaptive fundus imaging system is used to obtain high-resolution imaging ofhuman retina. The system requires quickly alignment of the subject’s pupil andstably maintenance for a period of time. Simple head prop used in clinicalophthalmology limited the distance between the doctor and the patient to the arm’slength so that it cannot be utilized in the extensive adaptive optics retinal imagingsystem. Abroad, the subject does not move while the instrument moves in mostcases. This way makes it stable but expensive. No relevant reports in the domestic..A2degree-of-freedom head prop driven by step motors is designed to support thesubject’s jaw and to make the subject’s pupil align more quickly and comfortably.By4direction buttons and3speed buttons, the moving dirction and speed of thehead prop can be easily controlled to achieve quickly and accurate alignment.Positioning accuracy is100μm, which meets the requirements of the adaptive opticsretinal imaging system.The main contents are as follows:(1) Depending on the requirements of adaptive fundus imaging system, thetechnical parameter of the head crop was determined: static load20kg; stroke100mm (horizontal)/80mm (vertical); precision100μm; speed100μm/s,1mm/s,10mm/s.(2) The mechanical structure of the head crop was designed. Apply self-lockingtrapezoidal screw in vertical movement and high transmission efficiency ball screw in horizontal movement, with two stepper motors providing power.(3) Three-dimensional solid models of each component was designed inSolidworks and an assmebly of the head crop virtual prototype is completed. Ainterference checking was conducted to confirm the location of the each componentdoes not interfere. A simulation exercise using Solidworks/motion module wasconducted which shows that the virtual prototype can work as expected.(4) The electronics design of the control system was completed. The systemtakes PIC16F877A as the core and ULN2003A as the drive chip. The overall circuitwas drawn in Proteus and the picc program was compiled in MPLAB. AMPLAB-Proteus co-simulation experiment was conducted and the real-time controlof the head prop motion state was achieved by4direction buttons and3speedbuttons.The innovation of this paper is completely independent design of twodegree-of-freedom head prop, which matches the high-end testing equipment inadaptive optics retinal imaging system and a solution to the limit of clinical headprop in romote operation. The design of the head prop is simple, economical andreliable, and will play a role in the promotion of urgent clinical endocrine diseasediagnostic equipment--adaptive fundus imaging systems.