Chromadepth is a patented system from the company Chromatek (a subsidiary of American Paper Optics since 2002) that produces a stereoscopic effect based upon differences in the diffraction of color through a special prism-like holographic film fitted into glasses. Chromadepth glasses purposely exacerbate chromatic aberration and give the illusion of colors taking up different positions in space, with red being in front, and blue being in back. This works particularly well with the sky, sea or grass as a background, and redder objects in the foreground.