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.

Abstract: A method and apparatus for improving the quality of light emitted from an HMD lightsource. A backlight-type lightsource is disclosed that utilizes a reflective end-wall 17 to reflect light within the lightguide. Light emitted from an illumination source and reflected from the end-wall 17 combine within the lightguide to produce light with high contrast and homogeneity. A microprism array, consisting of microprisms of uniform height and equidistant spacing, is positioned along the bottom surface of the lightguide. A portion of the combined light incident upon the microprism array is reflected in a direction substantially perpendicular to the lightguide top surface, which comprises an aperture. Light having increased brightness and homogeneity passes through the aperture. Light incident upon the top surface outside of the aperture is reflected within the lightguide so that it may subsequently be transmitted through the aperture.