On the Leica DMR series upright research stands (such as the DMRB, DMRE, and DMRD), the assembly built into the right-hand side of the stand’s base houses the transmitted light field and aperture diaphragms.

The designation "F1114" stamped or printed inside this assembly refers to an internal designator, mold number, or sub-assembly casting code utilized by Leica during the production of the DMR-series chassis in the 1990s. When sourcing replacement components, this is often found alongside the official catalog part number for the modular insert, which is 505-001 (often labeled as the Leica Diaphragm Module HC RF).

Here is a breakdown of how this double-diaphragm setup functions, how to locate it, and how to maintain it.

Optical Function & Role in Koehler Illumination

The DMRB features a dual-iris configuration aligned along the lower optical path before the light is redirected upward through the field lens to the condenser:

• The Field Diaphragm (Veldmanier): Controls the diameter of the light beam entering the condenser. Adjusting this allows you to match the illuminated field exactly to the field of view of the objective being used, eliminating extraneous stray light and maximizing image contrast.
• The Aperture Diaphragm (Apertuurmanier): Controls the angular aperture of the light cone. It is adjusted to match the numerical aperture (NA) of the active objective lens, balancing resolution and contrast depth.

Mechanical Access and the 505-001 Module

In the DMR chassis, this double-diaphragm system is built as a removable, self-contained mechanical cassette rather than being permanently machined directly into the cast frame.

• Location: It is positioned in the lower right flank of the microscope base. The controls are concentric or paired manual sliders/knobs that project from the side for ergonomic adjustments while viewing.
• Removability: Loosening the securing screws on the base casing allows the entire module to slide out. This modular design was chosen by Leica to facilitate easy cleaning or replacement without needing to strip down the entire stand framework.