| 摘要 |
PURPOSE:To improve the contrast by attaching a lens element being in the nearest position to the video tube of a projection lens, via a spacer, and placing a sealing material with a bending part having an L-shaped section against the inside wall of the spacer, by contacting it to a front glass plate of the video tube and the projection lens. CONSTITUTION:A projection lens 14 is attached through a spacer 13, in front of the front glass plate 12 of a video tube 11. A gelations trnasparent substance 15 having a refractive index being roughly equal to both refractive indexes of the front glass plate 12 and the projection lens 14 is packed in a space surrounded by the front glass plate 12 of this video tube 11, the spacer 13 and the projection lens 14. Also, the sealing material 16 provided with a bending part 18 having an L-shaped section so as to form a prescribed space 17 against the inside wall of the spacer 13 is allowed to contact with the front glass plate 12 of the video tube 11 and the projection lens 14. In this way, the gel-shaped transparent substrate 15 which contacts to the respective surfaces of the front plate 12 of the video tube 11 and the projection lens 14 is hardly peeled off, and the contrast of a projected image is improved.
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