| 摘要 |
PURPOSE:To prolong the service life of a light source and also to obtain stable luminous amounts by decreasing the extinguishing time to suppress the temperature drop of a filament and a tube in controlling the lighting of the light source and the scanning of an image pickup element in matching with the timing of subscanning. CONSTITUTION:When the next subscanning timing is inputted while a reading signal is outputted, the light source is lighted for a prescribed period t1 and then extinguished. Then, after the scanning period t2 and the lighting period t1 are both finished, the next scanning (period t3) is started. A signal of this scanning is an effective reading signal. If a subscanning timing does not come during a scanning period t5 when the effective reading signal is obtained, the light source is lighted when the scanning period t5 having the effective reading signal is obtained is elapsed and the scanning is finished. No restriction is given as to the scanning of an image pickup element 4 until the further subscanning. The scanning is started in the next subscanning timing. A signal in the scanning period t6 is an ineffective signal. The light source is extinguished for a prescribed period t4 (t4=t1) from the start of scanning. The next scanning is started after the end of scanning. A signal at this period t7 is stored between the scanning period t6 and the same period T2 and the light source is lighted for the period t4. |
