| 摘要 |
<p>The light control for a reprographic machine maintains the fluorescent lamps at reduced power whilst the machine is switched on, raising the power supply level whilst a copy is being made. When the machine is switched on, the lamps are lit at the nominal power level as specified by the manufacturers (eg 120 W/tube). At the same time a timing circuit is started. At the end of the timed interval a relay is changed, allowing the power to fall to a stand-by level. This stand-by level is approximately half the nominal power (65W/tube) and is just above the extinction power. A photosensitive detector senses the introduction of a document for copying, and in response to this the power supply is raised to a level higher than the nominal value (185W/tube). This maintained for the duration of the copying process. The technique increases lamp life by reducing electrode damage due to frequent turning on and off, and increases the useful light output intensity.</p> |
