| 摘要 |
In a color television system having picture-in-picture (PIP) capability, apparatus is provided for automatically modifying the operation of a beam current limiting (BCL) section while the small picture is being displayed to prevent the visibility of the small picture from being adversely affected. In an embodiment, a contrast BCL control signal is decoupled from the contrast section, and a substitute control signal, at least approximating the user responsive contrast control signal, is substituted for it in response to a switching signal which causes the small picture to be inserted within the big gicture. however, the BCL section continues to be responsive to the beam current during the time interval in which the small picture is displayed so that the BCL contrast control signal accurately represents the contents of the entire image. In addition, the operation of an automatic contrast reduction section which is responsive to a peak-white representative video signal is also disabled during the time interval in which the small picture is displayed. In an alternate embodiment only the operation of the contrast BCL section is disabled, but the operation of the automatic contrast control is maintained. If desired, a brightness BCL control signal may also be decoupled from the brightness section. |
