| 摘要 |
PURPOSE:To automatically obtain the in-focus state for every magnification in a microreader or the like by detecting distance information between a projection lens to be used and a projection original picture in the in-focus state of this projection lens from a peculiar signal by a detector. CONSTITUTION:When a projection lens A is set or moved to the use position, a peculiar signal B provided for the lens A is given to a detector D. The detector D detects distance information between the lens and a projection original picture C in the in-focus state of the lens A from the signal B. Meanwhile, the distance between the lens A and the original picture C is actually measured by a range finder F. The detection signal from the detector D and the measured signal from the finder F are given to a controller G and are compared with each other. As the result, they coincide with each other if the lens A is in the in-focus projection state for the original picture C, but they do not coincide with each other if the lens A is not in said state. Thus, the controller G discriminates the in-focus state or not to automatically adjust the microreader or the like to the in-focus state. |
