Patent ID: 8029954

Claim:
A method of exposing a substrate via a projection optical system by illuminating an original with an illumination optical system, the method comprising: setting a tentative value of an exposure condition for determining an exposure condition value; setting a simplified evaluation condition for evaluating a degree of intensity of a light intensity distribution in an image plane of the projection optical system, and a line width evaluation condition for evaluating a line width of an image formed on the image plane; computing a light intensity distribution in the image plane using the tentative value and computing a simplified evaluation value by evaluating the computed light intensity distribution with the simplified evaluation condition; computing a line width of the image formed on the image plane and computing a line width evaluation value by evaluating the computed line width with the line width evaluation condition, if the simplified evaluation value satisfies a first allowable value; and determining the exposure condition value if the line width evaluation value satisfies a second allowable value; wherein the tentative value of the exposure condition is changed and the computing the light intensity distribution is performed again using the changed tentative value of the exposure condition, without performing the computing the line width if the simplified evaluation value does not satisfy the first allowable value, wherein the tentative value of exposure condition is changed if the simplified evaluation value satisfy the first allowable value but the line width evaluation value does not satisfy the second allowable value, and wherein in the determining the exposure condition value, the latest changed tentative value of the exposure condition is determined as the exposure condition value.