A unifying theme of this thesis is the implementation and characterization of point probes for surface metrology. The implementations include two optical non-contact profiling methods; fiber-based Fabry-Perot interferometry and Confocal microscopy.
Even though Fiber-based Fabry-Perot interferometers are suitable for measuring surface texture in confined space, literature describing its implementation and limitations of this technique are scarce. To explore these knowledge gaps an experimental facility has been built and the feasibility for surface height measurements is validated by measuring two sinusoidal reference surfaces with heights of 1 μm and 1.5 μm and wavelengths of 100 μm and 50 μm respectively.
A second part of this thesis is to implement a flexure-based vertical scanning of an objective lens used for Confocal microscopy to increase the bandwidth of height detection and, therefore, surface scanning speeds. A sinusoidal reference sample is designed and manufactured, which is later measured using a confocal microscope prototype built using a 60X objective lens. A flexure to house the lens stack to provide a surface height scanning range of 10 μm is also designed and fabricated.
A third part of this thesis involves characterizing a stylus-based contact profiler for measuring areal form of freeform optics. Typically, for non-contact optical probes, the probe axis must be orthogonal to the curvature of the part being measured. This is not required for a stylus profiler. Reference objects such as optical flats, prisms, and spheres are measured using the stylus profiler and these measurements are compared with results from a Fizeau interferometer. From these measurements, vertical error of the X scanning carriage, side loading on the stylus probe due to the surface slope of the part being measured are estimated. A geometrical model of the profiler has been developed and used in a Monte Carlo simulation that predicts an uncertainty in the areal form measurements of less than 100 nm PV for a 100 mm measurement aperture.