Patent ID: 7465936

Claim:
An exposure apparatus for illuminating a pattern of a mask with light from a light source and for exposing the pattern onto a plate, said exposure apparatus comprising: a photodiode for measuring an exposure dose on the plate; a controller for controlling the exposure dose based on a measurement result of said photodiode; a calibrator for calibrating said photodiode; a bandpass filter for transmitting the light having a predetermined wavelength among lights emitted from the light source; a measurement apparatus for measuring an absolute intensity of an incident light via the bandpass filter; a condenser mirror for condensing the light from the light source, the condenser mirror having a reflective surface with an opening that allows the light from the light source to pass through the opening; and an operating part configured to perform a measuring method that utilizes the bandpass filter and the measurement apparatus, wherein the measurement apparatus is arranged at a side opposite to the reflective surface, and at a position that ensures a detection of the light that has passed through the opening, and wherein the measuring method includes the steps of: measuring an output of the measurement apparatus continuously; stopping or starting an emission of the light source in the measuring step; calculating a first extreme value t→t 0 −0 and a second extreme value t→t 0 +0 in the output of the measurement apparatus at time t 0 where t is time in the measuring step, and t 0 is time when the emission of the light source stops; and calculating a difference between the first extreme value t→t 0 −0 and the second extreme value t→t 0 +0.