IN THIS CHAPTER
How to align the illumination according
to Köhler
Chapter 15
Ten Steps to Set up Köhler
Illumination
August Köhler introduces this concept in 1893. This process brings illumination
and imaging beam paths into a defined, aligned state, providing homogeneous
illumination without stray light.
Here’s how to set up Köhler illumination on your upright transmitted light
microscope:
1. Choose the 10× objective as it is the easiest to start with.
2. Set the condenser to brightfield position.
3. Move the condenser to its top position.
4. Fully open both the luminous field stop and aperture stop.
5. Bring your specimen into focus.
6. Close the luminous field stop until you see it in the field of view.
7. Focus the luminous field stop image by lowering the condenser.
8. Use the condenser centering screws to center the luminous field
stop image.
9. Open the luminous field stop until its image disappears, just outside the
field of view.
10. Remove an eyepiece and look into the tube. Close the condenser aperture
stop diaphragm until the visible objective opening is illuminated by at least
two-thirds of its diameter,
then replace the eyepiece.