眼科临床上所使用的简易头托限定医生与受试者的距离不能超过一臂之长，因此无法用于较为庞大的眼底自适应成像系统。为了达到眼底自适应成像系统与受试者瞳孔快速对准、稳定定位的要求，设计了一种可长距离控制的二自由度的头托。采用具有自锁能力的梯形丝杠驱动头托垂直运动，采用传动效率高的滚珠丝杠驱动头托水平运动，以步进电机提供动力。基于PIC16F877单片机，完成了头托移动控制的软硬件设计，并在MPLAB与Proteus环境下进行了联合仿真实验。仿真结果表明，所设计的头托可在竖直方向和水平方向以20 μm的精准度定位，能够实现长距离、快速准确的瞳孔对准和左右瞳孔切换过程，是眼底自适应成像系统的良好辅助工具。

Simple head props used in clinical ophthalmology limit the distance between the doctor and the patient to arm’s length, so that it cannot be utilized in adaptive optics retinal imaging system which is big and heavy.A two degree-of-freedom head prop is designed to support the subject’s jaw and to make the subject’s pupil align more quickly and comfortably in adaptive optics retinal imaging system. Self-locking trapezoidal screw in vertical movement and high transmission efficiency ball screw in horizontal movement were used with two stepper motors providing power.The electronics design of the control system based on PIC16F877A was completed.A MPLAB-Proteus co-simulation experiment was conducted and the result shows that the system can do the control in realtime to make the motor start, stop, turn and speed.The designed head prop can move in the vertical direction and the horizontal direction at a minimum of 100 μm/s and improve the positioning accuracy to 20 μm, meeting the requirements of the adaptive optics retinal imaging system.