| 摘要 |
PURPOSE:To achieve detection of focus automatically, by making a liquid crystal screen opaque through power application, through the detection of focusing, in the focusing screen using liquid crystal. CONSTITUTION:In a camera having a liquid crystal plate 1 as a focusing screen, a comparator circuit 52 is connected to an ammeter terminal A in a bridge circuit, a low-level output is obtained to a voltage input being a certain range (taking O voltage as a center) corresponding to a focusing state by means of reference voltages 53, 54 and comparators 55, 56, the level is converted into a high level by an inverter 57, a liquid crystal plate is driven via an AC square wave generating circuit 51 to be opaque. At nonfocusing, no power is applied and the crystal plate is transparent, and the user can see a bright finder. |
