Measuring instrument and method for operating a measuring instrument for optical inspection of an object

A measuring instrument for optical inspection of an object includes a light source for illuminating an object; a detector; an illuminating beam path extending from the light source to the object; a detection beam path extending from the object to the detector; an illuminating optics disposed in the illuminating beam path and/or an imaging optics disposed in the detection beam path for imaging the object onto the detector; a position evaluation device for determining a distance between two points of the object; and an optical device for imposing a profile of a continuously monotonic function on an intensity of light from the light source. The optical device is disposed in at least one of a pupil plane of the imaging optics, a pupil plane of the illuminating optics, and a plane in the illuminating or imaging beam path conjugate with the pupil plane of the imaging optics or the pupil plane of the illuminating optics.