面向对象的光学系统自动对焦方法

基于光学系统的焦深及其与工件的相对位置关系等硬件因素,提出光学系统面向对象的快速对焦运动控制方法。该方法采用灰度差分法来构造聚焦特征值评价函数,并使成像系统的运动轨迹尽量短。将对焦过程分为纯线性运动、粗调焦和细调焦三个阶段,每个阶段控制参数的确定方法不同,但总的原则是尽量减少运动和缩短图像处理中的运动距离,尽量增大最小运动步长,利用变步长的浮动阈值搜索方式,克服局部聚焦和完全不能聚焦的情况。实例证明,该方法可以提高对焦效率和可靠性,35mm的对焦距离大约耗时10s左右。

Object-oriented automatic focusing of an optical system

On the basis of hardware factors such as focal depth of an optical system and the relative position relationship of workpiece with the optical system, a fast and precision focusing moving method is proposed. This method adopts grey gradient to constitute the function of focusing characteristic value, makes the moving length of the imaging system as short as possible, and divides the focusing process into three phases with different control parameters, namely: pure linear movement, coarse focusing and fine focusing phases. The general principle is to reduce movement and shorten the moving distance during image processing, enlarge the minimum movement step length as possible. Partial focusing and entirely un-focusing can be prevented by float threshold search mode with step length variation. Practical examples demonstrate that the focusing efficiency and reliability can be improved with time consumption of 10 seconds for 35mm focusing.