Double gratings lateral shearing interferometer for EUVL

At wavelength measurement is important for EUVL PO (Extreme Ultraviolet Lithograph Project Optics). Because the wavelength of EUVL is very short, it is difficult to use normal interferometers for this. We suggest a DLSI (Double grating lateral shearing interferometer) in which the influence of the light source can be canceled. Moreover, in DLSI, the interferogram is one-color.