放大镜头 meaning in English

magnification lens

But for some special medium materials , such as liquid crystal display controller pcb , magnifiers must be used to gather images to gain enough precision of inspection for the weak contrast between the basic board and the conductor . the images near the light axes are much cleared than that far away from the light axes , so the images can not be simply segmented by black and white and inspected with the methods of pcb which are based on the black white image
但对于一些特殊介质材料，如液晶显示控制电路板的检测，由于基板和导体之间对比度不大，而且为了达到检测精度，必须采用放大镜头进行图像采集，成像系统光轴附近的图像成像质量较好，而偏离光轴较远的图像质量较差。不能通过简单二值化来很好地分割图像，而已有的印刷电路板检测方法都是建立在二值图像进行分析的基础上。