Patent ID: 7929127

Claim:
A laser energy measuring unit comprising: a mask having a plurality of mask holes with different diameters, said mask being configured so that one of said mask holes is selectively positioned within an optical path of a laser beam; an attenuating member within the optical path of the laser beam downstream of said mask so as to attenuate energy of the laser beam having passed through said mask, said attenuating member having: a circular shading portion located so as to block a center part of the laser beam having passed through said mask from passing through said attenuating member at a position coincident with a center of the laser beam having passed through said mask; and a plurality of through holes arranged around said circular shading portion for attenuating the laser beam having passed through said mask, said through holes being formed in a formation area of said attenuating member wider than a spread area of said attenuating member through which energy of the laser beam having passed through said mask is distributed; a measuring device for measuring the energy of the laser beam having passed through said attenuating member such that a center part of an energy of the laser beam has been blocked by said circular shading portion of said attenuating member to thereby minimize the energy of the laser beam; and a condenser lens located at one side of said attenuating member, said condenser lens being configured to condense the laser beam having passed through said mask to said measuring device.