Abstract: A measurement device (2) for measuring a collimated wave front through a lithographic lens includes a radiant energy source (4), a lens group (6) for collimating light emitted from said radiant energy source and directing said collimated light (7) toward a reference surface (10). A first binary optic (12) disposed in line with said collimated light and located adjacent to an input conjugate of a lens under test. A second binary optic (18) is arranged in a spaced relationship and in line with said first binary optic for retroreflecting light passing through a lithographic lens disposed between said first and second binary optics. A recording system (8,9) is provided for recording an interference with the light retroreflected-reflected back through said lens and through said reference surface.

Abstract: An improved system (30) for measuring surface aberrations of concave cylindrical surfaces. In the illustrative embodiment, the invention includes a transmission flat (20), an interferometer (32), and a surface to be measured (28). The transmission flat (20) is a transparent disc that is placed between the interferometer (32) and the surface (28) to be measured. An electromagnetic wave (33,34,36,37) is generated by the interferometer (32), and is directed through the transmission flat (20). The wave (41) bounces off the surface (28) to be measured and is retro-reflected off a first surface (26) of the transmission flat. The electromagnetic wave (42) returns to the opposite side of the surface (28) under test. The wave (43) then bounces off the surface (28) under test and passes through the transmission flat (20). The wave (43) interferes with light (39) that is reflected from a reference surface (26) of transmission flat (20) on a first bounce.