Image-reading device that reads images by using spread-spectrum clock

Abstract

In an image-reading device, a counting unit counts a number of clock cycles of a spread-spectrum clock as a counter value. A correcting unit corrects one of the counter value and a reference clock cycle number based on a phase detected by the phase detecting unit when the counting unit counts. A comparing unit compares the counter value and the reference clock cycle number and determines whether the counter value and the reference clock cycle number satisfy a prescribed relationship. A time length setting unit sets a length of at least one of a reading time and an irradiation time based on: a timing when the counting unit starts counting to set the time length; and a timing when the comparing unit determines that the compared values satisfy the prescribed relationship, such that the time length set by the time length setting unit remains constant.