| 摘要 |
PURPOSE:To eliminate an error in recognition without being affected by the density variation of a microfilm nor variation in the quantity of image light by calculating the appearance frequency distribution of output levels corresponding to the quantities of transmitted light in respective plurally divided areas of the microfilm. CONSTITUTION:A scanning mirror and optical sensors S1-Sn on a sensor base are exposed to an image on the microfilm by scanning and then image illuminance data obtained by the sensors S1-Sn are passed through an A/D converter 17, and stored in a RAM 19 at prescribed time intervals and at right angles to the axial direction through the microcomputer or divided by arrangement intervals of the sensors S1-Sn and digitized in the axial direction. The illuminance data on the microfilm which is written in the RAM 19 is read out to calculate the output level appearance frequency distribution of respective plurally divided areas of the microfilm by the computer 18. Then, it is decided that the film is a positive from the low illuminance of a character part, etc., and it is also decided similarly that the film is a negative.
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