| 摘要 |
PURPOSE:To prevent production of uneven brightness caused due to a difference of a radiation quantity of an electron beam between a part of display screen and a blank part by controlling the brightness of the blank caused at the reception of the existing standard television signal in the opposite direction to the brightness of the existing television signal. CONSTITUTION:A timing signal WP is outputted from a system controller 4 corresponding to the blank caused when a received pattern of the existing standard television broadcast of the NTSC system is displayed on a picture tube 26 of high definition television, a switch circuit 36 is turned on and a signal having a level set by a variable resistor 37 is fed to adder circuits 21A-21C during the blank period via a brightness variable circuit 35. The level of the brightness variable circuit 35 is detected by a level detection circuit 33 and set by a detection level of a luminance signal Y inverted by an inversion circuit 34 and the brightness of the blank part is controlled in the opposite direction to the brightness of the video part. Thus, the deterioration in the secular change in the video part and the blank part is equal to each other and the production of uneven brightness and color unevenness is prevented. |
