1. Key Laboratory of Digital Medical Engineering of Hebei Province, Key Laboratory of Optoelectronic Information Materials of Hebei Province, Research & Development Center of Machine Vision Engineering of Hebei Province, College of Electron and Information Engineering, Hebei University, Baoding 071002, People's Republic of China
2. Electrical and Computer Engineering Department, Southern Illinois University Carbondale, Illinois, 1230 Lincoln Drive, Carbondale, Illinois 62901, USA
3. Department of Materials Science and Engineering, National University of Singapore, Singapore, Singapore 117576