Importance

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Abstract

Methods and apparatus are provided for equally aging a cathode ray tube (CRT). In the preferred embodiment, a standard CRT having a 4:3 aspect ratio is provided. An external video terminal is coupled to the CRT and receives any number of external video signals, one or more of which may be non-standard external video signals having a 16:9 aspect ratio. In response to a non-standard external video signal, the CRT is illuminated with a mismatched illumination ratio, i.e., a primary CRT region is illuminated and a secondary CRT region is not illuminated, resulting in an unequally aged CRT. A video pattern generator is coupled to the CRT and generates an internal video signal, such that the secondary CRT region is illuminated in response to the internal video signal. Control circuitry is provided for monitoring one or more CRT aging indicators, such as an amount of time and/or CRT luminous intensity, during receipt of the non-standard external video signal, and/or the luminous intensities at the primary CRT region and secondary CRT region, during the generation of a uniform internal video signal. The control circuitry also calculates a desired CRT age equalizing time based on the CRT aging indicators. The desired CRT age equalizing time represents the period of time the secondary CRT region should be illuminated to equalize the unequal CRT aging. The control circuitry is coupled to the video pattern generator to direct the video pattern generator to generate the internal video signal for a period of time equal to the desired CRT age equalizing time.

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First Claim