Patent ID: 8120844

Claim:
An image measuring apparatus for measuring a specimen comprising: an image-formation optical system which includes a zoom optical system and an objective lens which is placed between the specimen and the zoom optical system, the image-formation optical system being configured to form an image of the specimen; and an illumination optical system which includes a light source and a fly-eye integrator which is placed between the light source and the objective lens, the illumination optical system being configured to illuminate a region, which is imaged by the image-formation optical system, on the specimen, wherein the fly-eye integrator satisfies an expression (1): A×Φ/f>M×D L ×NA L (1) where A is the diameter of a circle inscribed in pseudo light sources of which light can pass the objective lens, and the pseudo light sources being formed on outgoing end face of fly-eye integrator, Φ is the diameter of a circle inscribed in end face of each lens element constituting fly-eye integrator, f is a focal distance of each lens element constituting fly-eye integrator, M is a zoom variable-power ratio of the image-formation optical system, D L is an effective field diameter of the image-formation optical system with minimum magnification, and NA L is a numerical aperture on the object side in the image-formation optical system with minimum magnification.