A detection apparatus, a detection method and an electron beam irradiation
apparatus for detecting deflection electrons in order to precisely focus
even if a vacuum seal valve is provided. An electron beam irradiation
apparatus including a vacuum seal valve mechanism which is provided in a
static pressure floating pad, and opens/closes an electron beam passage
with a piston so as to switch between an electron beam irradiation state
and a vacuum seal state, and a deflection electron detector which is
provided between the vacuum seal valve mechanism and a master disk and
detects a deflection electron signal generated from the master disk with
electron beam irradiation.