Air filter device and video projector using air filter device

An air filter cleaning device comprising:

• a base including a frame that defines an opening through which air is drawn;
• a flat filter element coupled to the frame to capture dust from the air passing through the opening;
• a fastener that fastens the filter element to the frame;
• and
• a self-propelled cleaning unit that cleans an upstream side of the filter element, wherein the self-propelled cleaning unit is coupled to the base to be movable back and forth between a standby position and a return position located away from the standby position, the self-propelled cleaning unit is located at the standby position in a non-cleaning state, and the self-propelled cleaning unit includes
• a rotation brush that removes dust from the upstream side of the filter element,
• a dust box that collects dust removed by the rotation brush,
• a motor that moves the self-propelled cleaning unit, and
• an elongated and level housing that accommodates the rotation brush, the dust box, and the motor;
• wherein when the self-propelled cleaning unit is located at the standby position, the housing lies along only the frame and lies away from the entire upstream side of the filter element and the fastener.