Image reading apparatus, image forming device, and method for controlling reading so frequency of pulse signal to stepper motor reduces vibration during quiet scanning mode

An image reading apparatus, comprising:

• a light source section for illuminating a document with light;
• an image sensor for receiving reflected light from the document, and outputting image signals in single-line units in a main scanning direction;
• an optical system member for directing the reflected light from the document to the image sensor;
• an operating section for accepting input of an enlargement factor at which to scan the document, and for accepting selection of a scanning mode for the document, including a normal mode and a quiet mode;
• an image processing section for generating image data of the document from pixels in a quantity according to the enlargement factor set from the operating section, doing so on the basis of the image signal outputted by the image sensor;
• a stepper motor for prompting movement by either the document or the light source section, or both;
• and
• a signal generating section for generating a pulse signal;
• inputting the generated pulse signal into the stepper motor;
• prompting the stepper motor to rotate at a speed in accordance with the frequency of the generated pulse signal;
• and, during scanning in the quiet mode, generating and inputting to the stepper motor a pulse signal of a frequency contained within a predetermined quiet mode frequency band, the quiet mode frequency band being a frequency band in which vibration based on rotation of the stepper motor is at or below a predetermined normal vibration level.