Maskless exposure apparatus having measurement optical unit to measure depths of focus of a plurality of beams and control method thereof

A maskless exposure apparatus comprising:

• a projection optical unit configured to generate a plurality of beams;
• a reference pattern-free measurement optical unit configured to acquire intensity information, central position information, focus information, and shape information of the plurality of beams by measuring the plurality of beams generated from the projection optical unit;
• and
• a controller unit to generate or correct exposure data using at least one information of the intensity information, the central position information, and focus information, and the shape information, acquired by the measurement optical unit,
• wherein the controller unit is configured to acquire the depths of focus of the plurality of beams acquired by the measurement optical unit, to calculate a reference depth of focus by calculating a mean of the depths of focus information of the plurality of beams, to set an effective focus range based on the reference depth of focus, and to correct exposure data by switching on beams corresponding to exposure data present within the effective focus range and switching off beams corresponding to exposure data outside the effective focus range.