| 摘要 |
PURPOSE:To attain an excellent gradation print regardless of the variable density of an original or the reflection factor by holding the background level of the original and converting each picture signal into the digital signal of plural bits based on the level. CONSTITUTION:In generating the start signal of read recording by a start timing generating circuit ST, an image sensor 16 is driven and the output of an amplifier AMP is stored in an original background level holding circuit 100. Four reference voltages Fref1-Vref4 are generated by referencing the level and used as the comparison voltage of comparators CMP1-4. The read signal of the image sensor 16 is converted into a 4-bit digital signal by a comparator 101 having the separate reference voltages Vref1-Vref2. The proper copy is obtained even with the dark background of the original or paper quality to which reflectance is deteriorated by taking also the variable density of the original and the reflectance due to the paper quality into account in this way. |
