Calibration and optimization of the effective resolution of an optical profiler using the white-noise method and a median filter

Abstract

Scattering effects from residual optical fabrication errors at mid-spatial frequencies limit the resolution of optical systems. An optical profiler is a useful tool for characterizing residual surface roughness in mid-spatial frequencies. The calibration of an optical profiler's resolution is critical for accurate optical metrology. Empirical methods are restricted to a traceable measurement tool or many calibration artifacts, which are complicated, incompatible and time-consuming. In past work, we used the fractal method to obtain the calibration results for the effective resolution and demonstrated a good transmission capacity within the effective spatial frequency range of the optical profiler. However, this method also requires another instrument, and it does not address the areas of ineffective parts. In this context, this paper proposes a fast, simple and universal method to solve these problems. This paper makes two main contributions to the literature. First, it calibrates the effective resolution of the optical profiler using only a common ultra-smooth surface. The calibration method is based on the primary spectral characteristics of white noise and the fractal surface. Second, it uses a median filter to extend the ranges of the effective spatial frequency, which optimizes the capability and utilization of the optical profiler.