| 摘要 |
PURPOSE:To obtain an electro-optical lens-barrel which can adjust the beam without fusing beam forming aperture by first changing intensity of condenser lens in the side of weakening excitation and thereafter changing intensity of condenser lens in the side of enhancing excitation. CONSTITUTION:A crossover image 3 must be aligned with the center of deflection of deflection electrode 13 which changes a beam size. A beam current density can be changed by adjusting two condenser lenses 6, 7 and changing only the crossover magnification factor, without changing a crossover image position 3. The beam current density can be increased by enlarging a crossover image 3. For this purpose, it is necessary to weaken the excitation of condenser lens 6 and move the crossover image 2 in such a direction as becoming far from an electron gun 30. In this case, the crossover image 3 moves in the direction as becoming far from a molding aperture 11, a crossover image 4 also moves in the direction as becoming far from a molding aperture 12 and the perture is not fused. Excitation of condenser lens 7 is enhanced and thereby a crossover images 3-5 are returned to the normal positions. |
