Newport Reflective Microscope Objectives are reverse Cassegrains following the Schwarzchild design. Accordingly, they have zero chromatic aberration, and negligible coma, spherical, and astigmatic aberrations. We offer 15X and 36X objectives, broadband coated with aluminum and over coated with magnesium fluoride (MgF2). They are usable from 200nm to 20µm.
Newport's reflective microscope objectives are fabricated from a single material providing a uniform thermal coefficient of expansion. Each objective contains two highly polished electroless nickel spherical mirrors. The mirrors are coated with aluminum and magnesium fluoride. Average reflection per surface of each mirror is 85% in the UV-VIS, and 90% in the IR (with a dip to 76% at 820nm). The primary mirror has a spherical concave surface with a center hole. The secondary mirror is a small convex spherical mirror that is machined into the spider assembly. The objectives are hand assembled in interferometric alignment fixtures allowing each pair of mirrors to be optimized as a set to achieve maximum resolution. Spot sizes of 2 µm for the 15X objective and 1µm for the 36X objective are typical.
In a typical focusing application, collimated light passes through the aperture hole in the primary mirror to the secondary mirror. The secondary mirror reflects and diverges the beam to fill the primary mirror. The primary mirror focuses the beam to a small spot called the Object Plane or Focal Point.