Convergence correcting device capable of coma correction for use in a cathode ray tube having in-line electron guns

A convergence correcting device for a cathode ray tube having a plurality of coplanar in-line electron guns for emitting electron beams to a screen and operating to deflect the electron beams using a magnetic field produced by a deflection coil, said device comprising:

• pole piece means provided individually for the outermost ones of said electron beams and adapted to produce a magnetic field for imparting a horizontal deflection force to the electron beams;
• convergence yoke means disposed in close vicinity to said pole piece means and adaptped to apply a magnetic flux produces in said convergence yoke means to said pole piece means;
• first coil means wound on said convergence yoke means and adapted to produce a first magnetic flux in said convergence yoke in response to a supply current, said first magnetic flux being applied to said pole piece means so as to produce a first magnetic field which imparts a horizontal deflection force to the outermost electron beams;
• second coil means wound on said convergence yoke means and adapted to produce a second magnetic flux in said convergence yoke means in response to a supply current, said second magnetic flux being applied to said pole piece means so as to produce a second magnetic field between the outermost ones of said pole piece means so that the second magnetic field acts to cancel a third magnetic field created between the outermost pole piece means by a third magnetic flux from said deflection coil;
• and
• means for supplying the currents to said first and second coil means;
• said convergence yoke means including a magnetic member which functions to pass the second magnetic flux through a neck section of said cathode ray tube other than said pole piece means, said magnetic member having one end coupling to said convergence yoke means and another end supporting said neck section located apart from said pole piece means.