PURPOSE: To enhance an accuracy of deciding a coefficient by calculating an evaluation value based on an alignment coil value having a large change amount upon varying of a slit return coefficient.
CONSTITUTION: An electron beam radiated from an electron gun 4 is aligned at an optical axis by an alignment coil 5, passed through an aperture 6 opened in a rectangular shape, converged by a lens 7, deflected by a slit deflector 8a and a return deflector 8b, and an electron beam image of an aperture 67 is formed on an aperture 9. Here, an arbitrary slit return coefficient is set, and maximum current values of a large beam, a vertically long beam, and a laterally long beam are measured. In this case, the values of the coil 5 to apply the maximum current values of the beams are measured, a sum of square mean of differences of the values of the coil 5 at X and Y axes is calculated, evaluated by calculating means and set. Thus, an accuracy of deciding the coefficient is improved.
DAIKYO YOSHIHISA
YASUDA HIROSHI
