基于红外图像边缘特性的自动对焦技术

与可见光图像相比,红外图像的分辨率较低,景物边缘较为粗糙,传统的自动调焦技术无法直接用于红外热成像系统。为了解决这一问题,采用基于红外图像边缘特性的自动对焦算法,建立快速有效的对焦评价函数,驱动高精度光机闭环控制单元,以实现快速、准确的红外自动对焦。系统包含数字处理单元和运动控制单元。其中数字图像处理单元主要进行红外数字图像的采集,利用Roberts梯度算子提取红外图像中的信息量,并统计边缘点数以评价图像的清晰度,实时计算序列红外图像中细节和信息量的变化量和趋势,从而提供运动控制单元所需的位置给定。运动控制单元则主要进行调焦电机的控制及驱动,完成自动聚焦的过程控制。最后,通过实验证明了该方案的有效性。

Auto-Focusing Technology Based on Edge Characteristics of Infrared Images

Since the resolution is low and the image edge is rough,the traditional auto-focusing technologies cannot be applied to the infrared images directly.To solve this problem,this article adopts the auto-focusing algorithm based on edge characteristics and designs an auto-focusing module which contains digital processing unit and motion control unit.The digital processing unit collects infrared images and extracts the edge information with Roberts operator.By accounting the number of edge pixel,the digital processing unit evaluates the image definition and calculates the changing trend of image details.In this way,it can provide position information to the motion control unit.Motion control unit shall drive the focusing motor to the expected position and complete the auto-focusing process.Finally,this design is verified via experiment on practical thermal imager.