Sheet feeding device and image forming apparatus

A sheet feeding device comprising:

• a mounting portion capable of accommodating a stack of sheets placed in a predetermined direction;
• a blowing device configured to blow air onto the stack of sheets placed in the mounting portion, thereby floating at least a top sheet from the stack of sheets;
• a suction/transportation mechanism including a suction belt provided above the mounting portion, the suction/transportation mechanism being configured to attract the top sheet floated by the blowing device to transport the attracted sheet toward a transportation path;
• an illuminating device configured to emit light toward an area to be captured by an image pickup device in a plane formed by an end surface of the stack of sheets which is closest to the image pickup device, the illuminating device being disposed so as to emit the light in a direction substantially normal to the plane at a position of the floated top sheet;
• the image pickup device disposed so as to be capable of capturing an image of light reflected by an edge of the floated top sheet and an edge of a next sheet therebelow;
• and
• a controller configured to:
• obtain a gap distance value between the floated top sheet and the next sheet based on the image captured by the image pickup device;
• and
• adjust an amount of the air blown by the blowing device based on the obtained gap distance value.