| 摘要 |
There are provided an image reading apparatus and a focus adjusting method thereof in which focusing can be accurately conducted by a simple moving mechanism. A condenser lens and line sensor can be moved being integrated with each other. When output values obtained when a document on AF line is read by a line sensor are represented by LS1, LS2, LS3, . . . , and when a broken line graph is considered on which the horizontal axis represents a reading position in the horizontal scanning direction and the vertical axis represents an intensity of an output signal, it is judged that the larger the total distance LM1+LM2+ . . . of the broken lines is, the more accurately the image is in focus. A square root of the sum of the square of a distance between the adjacent reading positions and the square of a difference of intensities of the signals which have been read, is calculated, and it is judged that the larger the sum is, the more accurately the focus is adjusted.
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