| 摘要 |
PURPOSE:To correct an outside magnetic field automatically even when the magnetic field enters in any direction by arranging magnetic sensors around a CRT screen and detecting a level difference of output signals of the sensors when the output signals take place simultaneously and generating a correction current while a polarity data is added thereto. CONSTITUTION:Magnetic sensors 51-54 are fitted to four corners of a display screen and output signals are fed to a comparison discrimination circuit 12 via amplifiers(AMP) 101-104 and A/D converters 111-114. Then a signal fed to the comparison discrimination circuit 12 compares and discriminates detection times and levels of the magnetic sensors 51-54. When outputs of the magnetic sensors 51-54 are changed simultaneously, the magnitude and the direction of the acting magnetic field are detected based on the change quantity, the polarity and the changing state and a correction current is generated based on the result of detection. Thus, when the CRT is used under a large outside magnetic field, the distortion of the display screen is automatically corrected. |
