Abstract: A rear projection screen unit in a large-size picture display system, composed by combining a plurality of rear projection screen panels arranged in a lattice square with at least one ordinate and abscissa beams disposed between the adjacent screen panels, wherein each of said screen panels intersects with each of said beams which themselves intersect with each other to form the lattice square, and each of said screen panels and ordinate and abscissa beams are connected together by a multiple mortise-and-tenon joint. The lattice square is installed in a outer frame and stressed in the four directions by a resilient members provided on the outer frame. The disclosed structure has minimized the width of the non-effective area in the screen unit, and realized a high reliability in installing strength of the respective screen panels in an integral body suitable for the large-size picture display system.

Abstract: A projection tube projects in front a visible light image produced by irradiating a target having a fluorescent screen formed on one surface thereof with an electron beam emitted from an electron gun. The projection tube includes an X-ray shield disposed to cover the surface of the target excluding the fluorescent screen, whereby the X-ray generated by irradiating the fluorescent screen on the target with the electron beam are shielded to prevent the transmission of the X-rays to the front of the projection tube, and also the X-ray shield has the effect of dissipating the heat from the target and simplifying the target positioning operation in the manufacture of projection tubes.