| 摘要 |
PURPOSE:To obtain an inexpensive automatic focusing lens barrel, by placing a half mirror on a fixed optical system in a lens barrel, providing a focusing point face on the side corresponding to said half mirror, and fitting a focusing point detector on said face so as to be attachable and detachable. CONSTITUTION:In a lens barrel 1 containing an objective lens 2, variable magnification lenses 3, 4, a fixed lens 5 and an aperture device 6, a prism 7 having a half mirror part 8 is placed, and on the side, a focusing lens 9 and a detecting focal face 14 are provided. Through a screw 21 with a control, a focusing point detector 11 is fitted. Image light is reflected by the half mirror part 8 through the objective lens 2, and forms an image on a focal face 10 by the lens 9. By the focusing point detector 11, its image forming light is detected, and by its signal, a motor 13, a speed reducer 14, a pinion 16, a gear 17 and a helicoid 18 are turned through a focus controlling and operating circuit 12, by which automatic focus control is executed. In this way, an inexpensive automatic focusing lens barrel is obtained. |
