| 摘要 |
PURPOSE:To prevent the difference of the deterioration between the middle part and the peripheral part of a display screen by arranging a polarized plate and a liquid crystal panel on a display screen and providing an effective pattern control means to be masked in matching with the aspect ratio of a displayed video signal. CONSTITUTION:In the case of displaying a high definition TV signal, changeover switches 103, 113, 123 are thrown respectively to the position of the high definition TV and a changeover switch 244 is opened. In this case, the entire screen of a CRT 130 is scanned. Moreover, since no voltage is applied to the liquid crystal, the light is transmitted through in the entire screen. In the case of displaying an NTSC video signal, the changeover switches 103, 113, 123 are thrown respectively to the position of the NTSC and the changeover switch 244 is closed. In this case, the entire screen of the CRT 130 is scanned but the video image is displayed on the middle part. A halftone picture is displayed at both edges of the CRT 130 and since an AC voltage is applied to the liquid crystal at both edges, no light is transmitted through. Plural video signals with different aspect ratio are displayed without causing the difference of the deterioration between the middle part and the peripheral part of the display pattern. |
