In a device for optically scanning and measuring an environment, where the device is a laser scanner having a light emitter which, by a rotary mirror, emits an emission light beam, with a light receiver which receives a reception light beam, which, after passing the rotary mirror and a receiver lens which has an optical axis, is reflected from an object in the environment of the laser scanner. The laser scanner also includes a control and evaluation unit which, for a multitude of measuring points, determines the distance to the object. Also, a rear mirror is provided on the optical axis behind the receiver lens, where the rear mirror reflects towards the receiver lens the reception light beam which is refracted by the receiver lens.