IMAGE READING DEVICE AND FOCUS ADJUSTMENT METHOD FOR IT

摘要

An image reading device which enables accurate focusing by a simple transfer mechanism and a focus adjustment method for the device. A condensing lens and a line sensor can be transferred integrally. The output values obtained by reading manuscripts on AF lines by the line sensor are denoted by LS1, LS2, LS3, ... and a line graph whose horizontal line shows the reading positions of the manuscripts in a main scanning direction and whose vertical line shows the values of the output signals is produced and, the larger a total length LM1 + LM2 + ... of the distances of the lines is, the better it is judged focusing is obtained. That is, the square root of the sum of the square of the distance between the adjacent reading positions and the square of the difference between the values of the signals read at the adjacent positions is calculated and the larger the summation of the calculated values is, the better focusing is obtained.