平面度测量中的选线原则

在平板的平面度测量中,最常用的、精度最高的方法,是利用光电准直光管或激光干涉仪测量一族直线在与平板垂直方向的直线度,然后根据直线度数据来确定平板的平面度。如何选择这一族直线是平面度测量中的一个重要问题。本文提出了绝对基准与浮动基准的概念。对于采用浮动基准的方法,例如准直光管法和激光干涉仪法,从理论上阐明了选线原则为:(1)线族的总自由度必须小于或等于三;(2)至少必须测量三种不同方向的线;(3)二条对角线是确定平面轮廓的最佳线;(4)平板平面度测量中应取四条周线与二条对角线为基本测量线。

THE PRINCIPLES OF PATTERN SELECTION IN SURFACE FLATNESS MEASUREMENT

The most popular and accurate method in flatness measurement of surface plate is based on measuring the straightness of a family of lines by an autocollimator or a laser interferometer in the direction perpendicular to the surface plate. The flatness of the surface plate is calculated from these straightness data. How to select this family of lines is an important problem in flatness measurement. The concept of absolute and floating reference s is proposed in this paper. It is proved theoretically for methods with floating reference, such as methods with autocollimators and laser interferometers, these principles are: (1) Degrees of freedom of the pattern must be less than or equal to three, (2) All lines to be measured have at least three different directions, (3) Two diagonals are the best lines for determining the profile of surface; (4) Four perimeter lines and two diagonals are the basic lines in flatness measurement of the surface plate.