Exposure apparatus and a method for controlling radiation from a lamp for exposing a photosensitive element

An exposure apparatus for exposing a photosensitive element to actinic radiation, comprising:

• an exposure bed for supporting the photosensitive element;
• a lamp assembly disposed adjacent the exposure bed comprising:
• at least two lamps that are adjacent to each other to expose the photosensitive element with the actinic radiation at a target irradiance;
• and
• an adjustable ballast connected to at least one lamp of the at least two lamps to adjust power received by the one lamp;
• a sensor disposed adjacent at least one lamp of the at least two lamps for measuring irradiance impinging the exposure bed;
• and
• a controller that adjusts the power to the adjustable ballast based upon comparison of the measured irradiance to the target irradiance to adjust the irradiance emitted from the at least one lamp to match the target irradiance,
• wherein the at least two lamps comprises a plurality of tubular lamps that are adjacent and parallel to each other, and further comprising means for moving the irradiance sensor to measure the irradiance emitting from the plurality of lamps at a first location and at a second location, or to measure irradiance emitting from each of the plurality of lamps.