| 摘要 |
PURPOSE:To obtain the excellent picture without convergence error by providing two magnetic field control elements comprising annular and tongue portions, which are opposedly arranged on the bottom of a shield magnetic pole disposed in an electron passing region which is subjected to the effect of the deflected magnetic field of an electron gun rear end portion in an electromagnetic deflection device. CONSTITUTION:A magnetic field control element 80 comprises an annular portion 81, made of high permeability magnetic material, perfectly surrounding external electron beam apertures 16R and 16 B located on the bottom of a shield magnetic pole 16 and a tongue portion 82 continously extending to the annular portion 81 on the central electron beam aperture 16G side. The annular 81 controls the horizontal and vertical deflection magnetic fields 5H and 5V on the external electron beam passage to be sided and the tongue portion 82 controls the vertical deflection magnetic field 5V to be forcused in the vicinity of the central electron beam aperture 16G. Therefore, the grasp area of the annular portion 81 in the magnetic field is made to be suitable so that the horizontal component of the scanning screens 34R and 34B formed by both electron beams is made to coincide with a scanning screen 34G and also coincide with the vertical width of the scanning screens 34R and 34B by adjusting the grasp area of the vertical field in the tongue portion 82.
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