Yang Chao1, Zhang Haibo1,Takaoka Akio 2
(1.School of Electronics and Information Engineering, Xi'an Jiaotong University, Xi'an 710049, China; 2 Research Center
for Ultra High Voltage Electron Microscopy, Osaka University, Osaka 565 0871, Japan)
Abstract:A method to quantitatively evaluate the TEM (transmission electron microscopy) image quality is proposed by calculating the point spread function equivalent area (the area of independent variable region whose normalized point spread function value is not less than 0 7071). The tilt series of practical ultrahigh voltage TEM images for three dimensional reconstruction is analyzed and the quantitative relationship between TEM image quality and specimen tilt angle is acquired. Followed the single axis tilting projection collection, the image quality is worsened with the increase of the specimen tilt angle and especially for the tilt angle larger that 60กใ the quality declines acutely. The point spread function equivalent area at 30กใ, 60กใ and 70กใ is 2 5,4 5 and 11 7 times as wider as that at 0กใ,respectively. This effect restricts to improve the three dimensional reconstruction resolution by increasing the specimen tilt range and suggests an optimum tilt range for the specimen in the three dimensional reconstruction form TEM images.
Keywords:transmission electron microscopy;image quality;point spread function;three dimensional reconstruction