DIY Dark-Field Filters

October 31, 2025 · View on GitHub

DIY Dark-Field Filters

An open-source filter for a custom dark-field setup that can be adapted to any compound microscope. 🔬🔬

darkField

This 3D-printed / laser-cut design is created for contrast illumination techniques, aimed at microscopy enthusiasts and professionals.

Why Improve Contrast?

In microscopy, a lot of samples especially those that aren’t stained or are still alive have such low contrast that even with a good microscope lens, important details are hard to see. improving contrast is key to making these details visible without messing up or damaging the sample.

How to use it for 3D printing?

Simply download the correct STL file for your prints.

video1

Want to customize the design for your own specific objective or microscope?

Alternatively: You can download the OpenScad file (1 file for folder) and very easily edit each parameter of the filter.

  • Download and install OpenScad (Free an open sofware for CAD files)

  • Open the file using the program and look for parameters of the filter

    image

  • Simply edit to your needs

    • All measurement are in milimiters

  • Generate a new STL file, save it and you are ready to print.

How to use it for Laser cutting?

  • Import the STL file into your laser cutting software:

    • Most popular laser cutting software supports importing STL files directly

  • Scale and position the object:

    • Adjust the size and orientation of the object as needed

  • Set material properties:

    • Input the thickness and type of material you'll be cutting

  • Start the cutting

How to use a spider stop ?

Most microscopes have a way to add a filter in the optical path between the ilumination and the condenser.

image (Taken from Abramowitz, Olympus Corporation 1990)

The diameter of the opaque stop should be approximately 8mm for the 10X objective of N.A. 0.25 to approximately 15mm for objectives of N.A. 0.65.

image

MAKE SURE !

  1. Your condenser is as close to the sample as possible !
  2. The Field Diafragm is at least 90 % open !
  3. Beyond 0.65 NA Spider stop filters are harder to use and allign !

This is How it looks!

daph_Dark

Daphnia sp, 25x, Custume Dark Field

For the spanish version check the LEEME.md!

Recomended readings

  • Abramowitz, Mortimer; Microscope Basics and Beyond Vol, 2; Olympus Corporation 1990
  • Bradbury, Savile; An Introduction to Light Microscopy; Oxford University Press 1984
  • Hartley, W.G.; Hartley's Microscopy; Senecio Publishers Limited 1979
  • Hoffman, Robert; The Modulation Contrast Microscope; Journal of Microscopy Vol. 110 pt. 3 August 1977