An image-reading lens is formed of a two lens elements of meniscus shape, one with its convex surface on the most object-side of the image-reading lens and one with its convex surface on the most image-side of the image-reading lens. An intermediate lens element of negative refractive power may be optionally...http://www.google.de/patents/US6147816?utm_source=gb-gplus-sharePatent US6147816 - Image-reading lens
