| 摘要 |
PROBLEM TO BE SOLVED: To keep an erasing light source at necessary illuminance in a short time and also effectively prolong the exchanging time of the erasing light source. SOLUTION: The erasing light sources 60a to 60b are arranged in an erasion part 34, and a temperature sensor 68 detecting the atmospheric temperature in the erasion part 34 is attached to a frame 62. When the atmospheric temperature detected by the sensor 68 is equal to or under 1st set temperature, the erasing light sources 60a to 60b are turned on, while the erasing light sources 60a to 60d are turned off when the atmospheric temperature reaches 2nd set temperature.
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