Improvement of birefringent filters. 2:achromatic waveplates

By use of Jones' matrix techniques, nine-element achromatic waveplates are developed. These combination plates are achromatic to within 1 degrees throughout the visible (3,500-10,000 A). In addition, a two-section general retarder rotator is demonstrated. The retardation of the combination is twice the complement of the angle between the halves, while the rotation is equal to the angle between the halves. For a 90 degrees retardation, the dual five-element combination is also achromatic to within 1 degrees throughout the visible.