A device is provided, which includes at least one optical area sensor having an optical semiaxis and an entrance pupil. The device also includes an optical element including at least one pair of parallel surfaces. The device is characterized in that the optical element has a refractive index which decreases as the distance from the center increases at least along a direction in parallel to the surfaces at least between one edge of the optical element and a center of the optical element. The optical element is situated with respect to the area sensor in such a way that the surfaces are situated perpendicularly to the optical semiaxis. The increase of the refractive index perpendicular to the optical semiaxis makes it possible to situate the optical element having the parallel surfaces perpendicular to the optical semiaxis, so that the block requires minimal installation space.