Microscope Objective Lens, Reflective, 36x, Infinite BFL

The 50102-02 Reflective Microscope Objective is a 36x magnification Reflective Microscope Objective with a back focal length of infinity. Newport Reflective Microscope Objectives are reverse Cassegrains following the Schwarzschild design. Accordingly, they have zero chromatic aberration, and negligible coma, spherical, and astigmatic aberrations. It is broadband coated with aluminum and over coated with magnesium fluoride (MgF₂). They are usable from 200nm to 20μm. Special gold coatings for the visible to IR region are available upon request.

Broad Bandwidth

Reflective optics do not experience chromatic effects associated with refractive optics, where refractive index varies with wavelength. Consequently reflective objectives can have excellent optical performance across an extremely broad wavelength range limited only by mirror reflectance. The reflective surfaces are broadband coated with aluminum and over-coated with magnesium fluoride (MgF2). They are usable from 200 nm to 20 µm. Average reflection per surface of each mirror is 85% in the UV-VIS, and 90% in the IR (with a dip to 76% near 820nm). Special coatings are available upon request including Gold for the visible to IR region.

Reverse Cassegrain Design

In a typical focusing application, collimated light passes through the aperture hole in the primary mirror to the secondary mirror. The secondary mirror then reflects and diverges the beam to fill the primary mirror. Finally, the primary mirror focuses the beam to a small spot called the Object Plane or Focal Point. This dual mirror configuration is known as a reverse Cassegrain (primary mirror collects or focuses light from or to a point, and the secondary mirror interacts with collimated light, the opposite of a traditional Cassegrain telescope). These objectives follow the Schwarzschild design. Accordingly, they have zero chromatic aberration, and negligible coma, spherical, and astigmatic aberrations.

Reflective Objective Construction

Our reflective microscope objectives are fabricated from a single material providing a uniform thermal coefficient of expansion. Each objective contains two highly polished nickel spherical mirrors coated with aluminum and magnesium fluoride. 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 1 µm for the 36X objective are typical.