| 摘要 |
PURPOSE:To correct the distortion of the image at the circumferential section by arranging a concave frenel lens on the front face of a cathode ray tube while protect from the glare by reflecting to the direction different from the viewer. CONSTITUTION:The electron beam projected from the electron gun 1 in a cathode ray tube is deflected by a deflector yoke 2 then passes through a shadow mask 3 to reach to the phosphorous face applied on the back face of the panel to emit the light. At the central portion of the frenel lens 13 the focus distance is infinite to provide no lens effect thereby the real image 14 will match with the virtual image 15. When increasing the curvature of the lens as departing from the center, the focus distance will be shortened thereby the virtual image 15 is pushed to the front face and shown on one plane. Since the frenel lens is waved while facing the concave face toward the viewer, the amount of the external light 7 reflected toward the viewer 8 will decrease to prevent the glare of the conventional cathode ray tube and the deterioration of the contrast is prevented. |
