1. Research Center of Machine Vision Engineering of Hebei UniversityKey Laboratory of Digital Medical Engineering of Hebei ProvinceCollege of Electron and Information EngineeringHebei University Baoding 071002 P. R. China
2. Department of Materials Science and EngineeringNational University of Singapore Singapore 117576 Singapore
3. Key Laboratory of Microelectronic Devices & Integrated TechnologyInstitute of MicroelectronicsChinese Academy of Sciences Beijing 100029 P. R. China
4. State Key Laboratory of ASIC and System School of MicroelectronicsFudan University Shanghai 200433 China