Patent ID: 8139215

Claim:
A measurement method for measuring polarization characteristics of light on an image plane where an image of a mask pattern is projected, the method comprising: illuminating the mask with light from a light source and projecting an image of the mask pattern onto the image plane; detecting light passing through a first slit while displacing the first slit having a width less than or equal to the wavelength of the light source on the image plane, and acquiring a first light intensity distribution with respect to the direction of displacement of the first slit; detecting light passing through a second slit while displacing the second slit having a width less than or equal to the wavelength of the light source on the image plane, and acquiring a second light intensity distribution with respect to the direction of displacement of the second slit; determining respectively positions where a maximum value and a minimum value of the first light intensity distribution are obtained and using the light intensities at positions corresponding to the determined positions in the second light intensity distribution to calculate an index value; and obtaining the polarization characteristics corresponding to the calculated index value by using information expressing a relationship between the index value and the polarization characteristics.