| 摘要 |
PROBLEM TO BE SOLVED: To provide a light bulb which can securely maintain a mark until replacement time. SOLUTION: A lamp base body 31 made of ceramics bonded to a bulb 21 with a filament 22 and a reflecting mirror 26 is heated with transition metal included in it. The transition metal produces a color oxidized by being heated, so a laser beam is irradiated on the lamp base body 31 to put on marks such as type number of a bulb, manufacturer's name, a serial number, and a standard, utilizing the color-producing function.
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