High accurate measurement and calibration of the squareness on ultra

Nowadays, the functionality of products often requires that parts are manufactured with a very small error. The squareness of metrology equipment is an important qualification for the functionality. Traditional methods of measuring squareness of ultra-precision motion stage have many limitations, especially the errors caused by inaccuracy of standard specimens, such as bare L-square and optical pentaprism. And generally, the accuracy of squareness measurement is lower than the accuracy of interior angles of standard specimens. Based on the error separation, this article presents a novel method of squareness measurement with a polygon artifact on the ultra-precision metrology machine. The angles bounded with the guideways and the edges of polygon artifact are measured, and the squareness distraction is achieved by the principle that the sum of internal angles of a convex polygon artifact is (n？？？2)π. A squareness metrical experiment is carried out on the profilometer using an optical square brick with the squareness of interior angles at about 0.3° and 2.4″. The results show that the squareness between the X axis and Y axis of the profilometer is approximate, and the accuracy of the squareness is not affected by the value of interior angles. The accurate measurement is much higher than the accuracy of the interior angles of brick. Based on this method and the traditional method, the three terms of squareness are calibrated and improved from 19.71″, 21.37″ and 16.54″ to 3.28″, 7.83″ and 5.88″, respectively