Patent ID: 7095699

Claim:
A detection apparatus including an electron beam irradiation head for permitting electron beam irradiation upon maintaining a position having a microscopic gap facing a recording medium; a securing and disposing means for securing and disposing said electron beam irradiation head emitting the electron beam by rendering said recording medium under partial vacuum; a movement means for moving said recording medium in a radial direction, a rotation means for rotating said recording medium when mounted on said movement means; a support means for horizontally mounting and supporting said recording medium when mounted on a rotating shaft of said rotation means; a focus table provided on a side of said support means for focusing said electron beam; a focus adjusting means for making a focus of said electron beam adjustable against said recording medium with said electron beam irradiation head opposing said focus table; and a static pressure floating pad provided in an electron beam passage on an end of said electron beam irradiation head; said detection apparatus detecting a signal for focusing according to a change of shape or material of a surface of said recording medium caused by electron beam irradiation upon using said focus adjusting means, when linearly recording information on said recording medium supported to be movable in a rotational direction and in a radial direction; wherein said detection apparatus comprises: a vacuum seal switching means for switching between an electron beam irradiation state and a vacuum seal state by opening/closing said electron beam passage with a piston, said switching means provided in said static pressure floating pad; and a deflection electron detection means for detecting a deflection electron signal generated from said recording medium due to said electron beam irradiation, said detection means provided between said vacuum seal switching means and said recording medium.