Application of microcomputer in submicron level measurements and control of a positioning device

This article demonstrates an application of a microcomputer in the area of automated manufacturing, in particular to the measurement and control of a positioning device with the accuracy level of less than 1 μm. The positioning device is generally used for calibration or testing purposes to check the dimensional accuracy of manufactured parts. Here, however, it is utilized for calibration of artifacts like scales, grid plates, calipers, etc. The artifacts are widely used in industry as a referencing device to determine whether the manufactured product meets dimensional quality requirements whilst maintaining high reliability and speeding up quality control operations. The critical challenge here is to develop an automated two-dimensional precision grid plate testing system which measures an array of grid points premarked on a grid plate. The grid plates discussed in this paper are generally glass plates with some type of symmetric marks placed on the glass surface. The goal is to use off-the-shelf type of equipment such as laser interferometer, precision positioning stage, computer controlled machine vision system and a host microcomputer, and integrate them to build a low-cost, practical system usable for the grid plate calibration services. This requires the development of compatible hardware and software protocols. The initial assessment of the test setup indicates that the present system can measure locations of grid points with an accuracy of 0.5 μm. Further improvements to the system are also suggested.