Multi-mode, hybrid-type CRT and electron gun therefor with selectable different sized grid apertures

An electron gun for a multi-mode color cathode ray tube (CRT) including a display screen whereon a video image is formed by sweeping a plurality of horizontally aligned electron beams over a plurality of vertically spaced, horizontal scan lines in a raster-like manner, wherein each electron beam provides one of the three primary colors of red, green or blue of the video image, said electron gun comprising:

• cathode means for providing energetic electrons;
• a beam forming region (BFR) disposed adjacent to said cathode means and including:
• first beam forming means for forming said energetic electrons into a first plurality of horizontally aligned, spaced electron beams providing the three primary colors of red, green and blue, wherein each of said first plurality of electron beams has a cross-section A.sub.1 when the CRT is used as a television receiver;
• and
• second beam forming means for forming said energetic electrons into a second plurality of horizontally aligned, spaced electron beams providing the three primary colors of red, green and blue, wherein each of said second plurality of electron beams has a cross-section A.sub.2 when the CRT is used as a high resolution video monitor, where A.sub.1 >A.sub.2 ;
• said BFR further including a G1 control grid and first and second G2 screen grids, wherein said first and second G2 screen grids are separate and detached from one another and respectively include first upper and second lower pluralities of horizontally aligned beam passing apertures, wherein each of said first pluralities of upper apertures has a diameter D.sub.1 and each of said second pluralities of lower apertures has a diameter of D.sub.2, and wherein said first pluralities of upper apertures forms said first electron beams and said second pluralities of lower apertures forms said second electron beams, with D.sub.1 >D.sub.2, and wherein each first upper aperture is in vertical alignment with a respective second lower aperture;
• switch means coupled to said first and second G2 screen grids for allowing a user to select either said fast electron beams in a television receiver mode of operation or said second electron beams in a high resolution video monitor mode of operation;
• lens means disposed intermediate said BFR and the CRT's display screen for focusing the electron beams on the display screen;
• and
• convergence means disposed intermediate said lens means and the display screen for converging said first and second pluralities of horizontally aligned, spaced electron beams into first and second spots on the display screen.