目前数码显微镜中常用的自动对焦方法分为主动式自动对焦和被动式自动对焦。主动式自动对焦依赖特定的传感器或者测距设备,通过主动发出光波并且接收反射回来的光波判断物体与对焦装置的距离,从而达到对焦目的;被动式自动对焦通过分析每个位置图像信息来判断对焦方向以及对焦位置,以达到对焦目的。被动式自动对焦由于其对结构的要求简单、成本较低,是数码显微镜最常用的自动对焦方法。主要介绍了应用于数码显微镜的自动对焦算法,简述了主动式与被动式自动对焦的原理以及发展方向,重点介绍了被动式自动对焦方法中的对焦深度法,分析了对焦深度法的两大关键技术,即清晰度评价函数及其对焦搜索算法。

At present, the commonly used auto focusing methods for digital microscopes are divided into active auto focusing and passive auto focusing. Active auto focusing relies on a specific sensor or a distance measuring device, which automatically emits light and receives reflected light to determine the distance from the object to the focusing device and achieve focusing. Passive auto focusing can determine the focus direction and focus position by analyzing the image information of each position, therefore realizing focusing. Passive auto focusing is the most commonly used auto focusing method for digital microscopes due to its low structure requirements and low cost. This paper mainly introduces the auto focusing algorithm for digital microscopes, briefly describes the principle and development direction of active and passive auto focusing methods, focuses on the depth from focus method of passive auto focusing methods, and analyzes two key technologies of the depth from focus method, that is, the sharpness evaluation function and its focus search algorithm.