1. Apparatus for forming a two-dimensional image of a two-dimensional sample array, said apparatus comprising: a sample holder defining a planar sample area having a width and a length; a light source forming a line of light that spans said width of said sample area; means for moving either said sample holder or said light source along an axis parallel to said length of said sample holder to thereby expose said entire sample area to said line of light; a detector comprising a CCD camera in time delay integration mode, said detector arranged to collect light emerging from said sample area as said sample area is illuminated by said line of light; and means for computerized processing of data collected by said detector to assemble an image of said sample area as said means for moving exposes said entire sample area to said line of light.