Image scanning device, image forming apparatus, and light source failure detection method

A method of detecting light source failure for an image scanning device,

• the image scanning device comprising
• lighting circuits;
• a light source including light-emitting elements connected to the lighting circuits, the light-emitting elements being arranged in a line such that a group of the light-emitting elements connected in series to a same one of the lighting circuits are not positioned adjacent to each other;
• a reflecting part for shading correction extending in a main-scanning direction;
• a photoelectric conversion unit photoelectrically converting reflected light from the reflecting part;
• a lighting control unit;
• a memory storing an area information table containing information on main-scanning areas of the photoelectric conversion unit in association with identification information of the lighting circuits;
• and
• a failure determining unit,
• the method comprising the steps of:
• selectively turning on one of the lighting circuits by the lighting control unit;
• identifying, by the failure determining unit, the main-scanning areas of the photoelectric conversion unit corresponding to the identification information of the one of the lighting circuits turned on by the lighting control unit by referring to the area information table;
• and
• comparing, by the failure determining unit, intensities of the reflected light entering the identified main-scanning areas with a first threshold to determine whether the light-emitting elements connected to the one of the lighting circuits are at fault.