Abstract: Synthesis of arrays of chain molecules, such as oligonucleotides, in large quantities can be carried out utilizing projection onto an active substrate of a magnified image of a light emitting object array having selectable regions of light and dark areas forming a pattern. Projection optics formed entirely of mirrors are used to receive the light emitted from the object array and image the pattern of the array onto the active surface of the substrate. The mirrors in the projection optics include a first, concave mirror, a second, convex mirror, a third, concave mirror, and a fourth, convex mirror, each receiving the beam of light in turn, with the light reflected from the fourth mirror being imaged onto the active surface of the substrate with an image area greater than that of the original light emitting array.