Uncertainty Evaluation Through Monte Carlo Simulation for Flatness Measurement of Optical Flats

In this investigation, the flatness error of an optical flat has been measured using Fizeau laser interferometer, followed by measurement uncertainty evaluation. Various contributing error sources such as laser interferometer resolution, environmental conditions, mechanical distortions and reference flat uncertainty have been identified, and the uncertainty evaluation for flatness error measurement has been conducted through two approaches: law of propagation of uncertainty (LPU) and Monte Carlo simulation (MCS). Measurement uncertainty through LPU approach has been ± 20.8 nm (k = 2), whereas measurement uncertainty using MCS has been ± 20.3 nm (k = 2). Measurement uncertainties evaluated through both the techniques have been observed to be in good agreement.