| 摘要 |
PURPOSE:To read excellently a recording picture such as a microfilm by adjusting a focus by a film transmission light after the exposure is adjusted at application of power supply and deciding the threshold value of quantized picture information. CONSTITUTION:In turning on a power switch 140, a CPU 301 initializes each circuit, drives carrier equipments 123, 129 to rewind a film F, a lamp 32 is lighted at the end of rewinding, the luminous quantity is detected by an image sensor 36 and its exposure signal drives a light quantity control circuit 302. When the light quantity of the lamp 32 reaches a prescribed value, the film retrieval is applied, an automatic focus circuit 303 is operated to focus the picture frame set to the read position based on a picture read signal. While a sensor 36 is moved by a CCD sub scanner 12, the picture frame is read and a processing circuit 304 judges the picture density based on the picture signal to decide the threshold value in response to the density.
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