| 摘要 |
<p>A first backlight light source (100) is energized either at full or reduced rated power, until such time as the brightness which can be produced has reduced by a predetermined amount (e.g. half of the original level). A second or backup source (102) is then switched on while the first is temporarily switched off. When the backup light source (102) has degraded to the point where the brightness which can be produced by this light source has reduced by a second predetermined amount (which is the same as the first predetermined amount, e.g. 50 %) the first light source (100) is switched back on so that both are simultaneously energized. When this measure fails to maintain the required level of brightness, the power with which the light sources (100, 102) are energized is increased.</p> |
