| 摘要 |
PURPOSE:To grasp the automatic exposure of a microfilm camera effectively by a single sensor by making one turn of a lens device and measuring light from a negative entirely, and determining the quantity of exposure. CONSTITUTION:A lens device 20 is arranged on a vertical optical axis 11 for the negative 10 almost in its center part and the device 20 is rotated by a driving mechanism 30 in one direction. This device 20 has a cylindrical lens holding part 21 made of an opaque material through which the rays of light are not transmitted, a photodetection lens 22 is fitted at a position eccentric from the optical axis 11 in the center of the holding pat 21 by distance (d), and the sensor 14 is arranged at the image formation position of a lens 22. Then, image information on a light metering spot 10A on the negative 10 is inputted as the quantity of light to the lens 22 and sensor 14, so the device 20 is rotated by a mechanism 30 to rotate the spot 10A in the same direction as well. Consequently, the device 20 is rotated around the optical axis 11 by one turn and the negative 10 in a doughnut-shaped area 10B is detected as image information by the sensor 14. |
