Abstract: An illumination device for a microscope or an optical 3D surface measuring apparatus, more particularly according to the principle of focus variation. The illumination device includes LEDs arranged in a planar fashion, and an illumination optical unit for imaging the illumination spectrum onto an object to be examined. The illumination optical unit includes an arrangement of converging lenses and one Fresnel lens, and the light beams emitted by the LEDs firstly impinge on the converging lenses and then impinge in a parallel-directed manner on the Fresnel lens. The Fresnel lens is oriented in reflective arrangement such that lens vertices of a prism structure are arranged at a light exit side of the Fresnel lens, facing away from the converging lenses. The converging lenses are formed by annular segments, and adjacent annular segments adjoin one another in a planar fashion at a segment side surface.

Abstract: An illumination device for a microscope or an optical 3D surface measuring apparatus, more particularly according to the principle of focus variation. The illumination device includes LEDs arranged in a planar fashion, and an illumination optical unit for imaging the illumination spectrum onto an object to be examined. The illumination optical unit includes an arrangement of converging lenses and one Fresnel lens, and the light beams emitted by the LEDs firstly impinge on the converging lenses and then impinge in a parallel-directed manner on the Fresnel lens. The Fresnel lens is oriented in reflective arrangement such that lens vertices of a prism structure are arranged at a light exit side of the Fresnel lens, facing away from the converging lenses. The converging lenses are formed by annular segments, and adjacent annular segments adjoin one another in a planar fashion at a segment side surface.