Patent ID: 7379176

Claim:
A mask defect inspection apparatus, comprising: an illumination optical system configured to illuminate a plurality of illumination areas different from each other of a mask on which a pattern is formed; an objective lens facing said mask; at least two detection optical systems each configured to receive illumination light from a corresponding one of the illumination areas different from each other of the mask through said objective lens, and each having a detection sensor configured to obtain an image of the pattern in the corresponding one of the illumination areas of the mask based on the illumination light from the corresponding one of the illumination areas of the mask received by the corresponding one of the at least two detection optical systems; and a focusing changing device configured to change a position of focusing between sites of the pattern in a film-thickness direction of said mask and the pattern image obtained by each of said detection sensors, such that pattern image obtained by each of said detection sensors are changed corresponding to the film-thickness direction of said mask, wherein one of said detection optical systems is a transmission-detection optical system configured to form the pattern image of one of the illumination areas illuminated by transmission-illumination light on said respective detection sensor, and the other of said detection optical systems is a reflection-detection optical system configured to form the pattern image of one of the illumination areas illuminated by reflection-illumination light on said respective detection sensor, and wherein said focusing changing device comprises a moving mechanism configured to move said detection sensors in a direction of an optical axis of said detection optical system while a distance between said mask and said objective lens is maintained constant.