| 摘要 |
PURPOSE:To set the travel speed of a light shielding blade lower by driving a stepping motor on a single-phase or two-phase excitation basis when the light shielding blade travels at a low speed. CONSTITUTION:A switching circuit 10 outputs one exciting signal according to camera lens information, and selects a two-phase exciting signal D when the lens information indicates telescope photography or a single-phase exciting signal S when the lens information indicates wide-angle photography. The selected exciting signal is inputted to a motor driving circuit 11, which drives the stepping motor 12 on the two-phase or single-phase excitation basis according to the selected exciting signal. The stepping motor 12 is a multipolar type capable of rotating in two forward and reverse directions and performs reversible step rotation according to the polarity of the selected exciting signal to make the light shielding blade S travel, thereby opening and closing the lens. Consequently, the rotating speed of the stepping motor 12 can be reduced to cope with versatility of photographic conditions. |
