Critical Surface Quality Inspection And Analysis Of Precision Optical Components Fabricated Using CMP Methods

Optical prisms are common optical elements containing only optical quality surfaces with Angstrom dimensioned flatness. Prisms are used to disperse, displace, deviate or re-orientate light beams and images. Optical prisms are used in a variety of navigational units for beam deflection and beam control. The prism is a critical component that defines the performance of a navigational sensor. The optical prism is fabricated through CMP process. The planarity, surface finish, bulk and surface straie, voids, micro scratches etc., formed during grinding and polishing process affect the overall optical performance.In this manuscript, we study the optical component polishing process through qualitative and quantitative metrology methods to optimize the surface finish. The ultimate goal is to achieve a surface finish (over the area of illumination) that results in optical flatness to approximately few nanometers or a ratio of 1/20^th of a wavelength. The measurement includes non-contact optical profiling and surface area imaging using digital imaging methods and correlating the measurements between the two techniques. We present the analysis and results of digital image processing techniques to study the surface quality. The capabilities, limitations, opportunities and challenges of quality control techniques in optical polishing and CMP techniques are discussed.