基于图像清晰度的自动聚焦算法

在数字监控和机器视觉中，摄像头的焦距可以由计算机根据图像的清晰度自动控制。本文针对监控系统在目标跟踪时对自动聚焦的速度和精度的要求，提出了两次定位、单向搜索的快速精确的聚焦算法。在聚焦精度方面首先针对全局图像进行第一次粗略的聚焦，图像的清晰度判断采用计算速度较快的相邻象素差分法的判断函数；然后再对图像中的目标区域进行第二次精确的聚焦，图像清晰度判断采用对清晰度变化敏感的基于Laplacian边缘检测的判断函数。调焦过程采用最佳焦距位置的单向搜索法，以提高聚焦的速度。实验证明该算法具有较好的实时性和精确性。

THE FAST AUTO-FOCUSING ALGORITHMS BASED ON IMAGE OBJECT

In the application related to the machine vision and the digital supervising,the auto-focus of the camera plays an important role.The research focuses on the auto-focusing algorthms based on the sharpness character of the image from CCD camera systems.The paper suggests a fast algorithm to focus on an object region of the image rapidly and accurately.An efficient and practical algorithm is presented in the paper.The algorithm adapts two steps to focus on the object region.Firstly,the camera focuses on the whole image according to the different of pixels as a sharpness function. Secondly,it focuses on the object region while the sharpness function is based on Laplacian edge detection.The algorithm is fast in real time and accurate in focusing degree.The experiment is made successfully in digital supervising system.