A Novel Non-Contact Profilometer for Characterising Grey Surfaces Before Polishing

This thesis presents a novel design of a surface metrology instrument named Swinging Part Profilometer (SPP). Software design, components manufacture, instalment and whole system manipulation are included in this thesis. The motivation of designing a SPP is a critical jigsaw of the autonomous manufacturing for optical components. The SPP is designed to fill up the gap of surface metrology between grinding and polishing.

A detailed survey of current surface metrology methods which contained advantages and disadvantages was included in Chapter 2 of the thesis. The proposal of SPP was based on the short-comings of the current surface measurement techniques. The SPP technique also referenced and modified the principles of Swing Arm profilometer (SAP). It utilised the existing mechanical air-bearing rotary table and industrial robot can significantly reduce the total time of conducting a surface measurement process.

Initially, a basic surface measurement model was designed and all the SPP system components were drawn by Solidworks software based on this measurement model. Based on the Solidworks drawings all the SPP components were fabricated and installed. A Solartron pneumatic contact probe and two Armstrong@ Precitec probes with different vertical resolutions (300nm/20nm) were adopted in the SPP system. The SPP prototype was capable of measuring flat and concave spherical surfaces. The SPP prototype was tested by measuring a 300mm corner-to-corner hexagonal flat mirror and 400mm corner-to-corner hexagonal concave spherical mirror. The data stitching algorithm was also validated by Matlab programme.

The SPP was then utilised to test the mid-spatial frequency (MSF) errors on an off-axis parabolic aluminium mirror with the help of a high vertical resolution (20nm) chromatic probe. Finally, the performance of non-contact probe on a grey surface was tested in order to figure out the boundary of the probe’s data collection.