Long Depth of a Focus Optical Microscopy Based on Computer Image Processing

人们对微机电系统越来越感兴趣。光学显微镜用于微加工零件的装配操作。在光学显微镜下进行这些操作并不容易，因为光学显微镜的焦点深度太短。从这个角度出发，提出了一种利用计算机图像处理获得光学显微镜图像长焦深的新颖方法。显微镜物镜由PZT等作动器确定定位。在每个定位位置，通过CCD相机将数字图像输入计算机。计算机从这些图像中提取出图像有焦点的区域，然后组成整帧图像。合成图像的聚焦深度几乎等于物镜的运动阻力。在区分焦点区域和非焦点区域的方法上，提出了三种不同的方法。本文分别将其命名为亮度差法、亮度分布法和hadamard传递序列分布法。从加工时间和精度上看，hadamard传递法的序列分布是这三种方法中最好的。该方法已应用于标准表面粗糙度试件、金属沟槽表面等几种试样的观察，取得了良好的效果。通过将位移信息添加到CCD相机记录的图像中，该方法也适用于三维表面形貌的测量。

There is a growing interest in micro electro mechanical systems. For the assembly operation of micro machining partsoptical microscope is used. It is often experienced that these operation under optical microscope is not easy, because depth of a focus of optical microscope is too short. From this point of view, a original method to get long depth of focus of optical microscope image using computer image processing has been proposed. The microscope objective is determined positioning by actuator such as PZT.At each located position, digital picture image through CCD camera is taken into a computer. The computer extractes has area where the image is in focus from these pictures, then it composes whole frame image. The depth of focus of the composite picture image is nearly equal to the sistance of motion of objective lens. As for the methods that distinguish between in-focus-area and out-focus-area, three different methods have been proposed. They are named here as differnce of luminance method, distributiuon of luminance method, and distribution of sequence of hadamard transfer method respectively. Processing time and accuracy point of view, distribution of sequence of hadamard transfer method is the best within these three methods.This method has been applied to the observation of several specimens such as standard surface roughness test-piece, grooved metal surface and so on, with excellent results. By adding displacement information to the recorded CCD camera image, this method is also applicable to the three dimensional surface topography measurement.