| 摘要 |
PROBLEM TO BE SOLVED: To stably correct the luminance, that transiently changes immediately after a power supply is turned on, while maintaining a simple and low cost constitution. SOLUTION: A cathode ray tube has an electronic gun 1 which incorporates a heater 7 to heat up a cathode 8 to an operating temperature. The cathode ray tube provided with a heater voltage detecting circuit 10 which detects voltage applied tot he heater 7, an integrating circuit 11 which integrates the heater voltage detected by the circuit 10, and a cutoff compensating circuit 12 which compensates each of electrode driving voltages of the gun 1 so as to follow the cutoff level that is a shutoff threshold of a cathode current to make the phosphor surface 6 of the cathode ray tube emit light using the output of the circuit 11. Moreover, a correcting device is provided to correct the luminance change of the tube based on the header voltage.
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