▎ 摘　　要

A simple method based on relative luminance is proposed for the rapid counting of layers in multilayer graphene. The number of graphene layers can be immediately identified by processing the acquired standard RGB images, once the one-time calibration of the entire optical system has been performed. The estimated number of layers was corroborated using the common counting methods of Raman spectroscopy and atomic force microscopy. The relative luminance method was successfully applied on both pristine and chemical vapor deposited graphene, regardless of the microscopes or even the substrates utilized, as long as there are some noticeable contrast differences. (C) 2015 Elsevier Ltd. All rights reserved.