| 摘要 |
PROBLEM TO BE SOLVED: To make it possible to obtain a thermal radiation source which can be electrically modulated at a high speed by covering an incandescent filament thoroughly with a thin, uniform layer made of oxidation resistant insulative material such as silicon nitride. SOLUTION: The total length of an incandescent filament 10 is covered with an insulative layer. A substrate wafer 13 is etched from its rear surface up to its upper surface so as to form an opening on the filament 10. Since the filament 10 is thoroughly covered with an insulative material, its service life depends on oxidization speed thereof. Further, the filament 10 is operated without being overlaid with a window, an organic contaminant dropping on the filament 10 is burned out. The maximum operable modulation speed of the radiation source depends on the rate of heat loss. The temperature of incandescent filament is an almost linear function of heating input electric power. In such a structure, a thermal time constant of about 10ms can be obtained, and electric mudulation can be also realized upto around 200Hz. |
