How to perform Kohler Illumination with PDF Guide

PURPOSE

Kohler Illumination, developed by August Kohler, is the method used to adjust microscopic illumination to achieve optimum magnification, resolution and contrast. This method is also known as Double Diaphragm Illumination because it employs both a field and an aperture iris diaphragm to set up the illumination. (Your microscope must have both of these diaphragms to do this procedure)

If the light path is set up properly, you will have the advantage of:

1. An evenly illuminated field.
2. A bright image without glare.
3. Minimum heating of the specimen.

PROCEDURE (SEE PHOTOS BELOW)

1. Place the specimen on the microscope stage and turn on the light.
2. Set light source to a comfortable intensity
3. Using the Low Power (10x objective, focus on the specimen).
4. Remove the filter (if present).
5. Swing the condenser in and raise it to its highest position.
6. Close the field diaphragm on the base of the microscope – you should see a small circle light. (see photo)
7. Lower condenser until the edge of the bright circle is crisp. (see photo)
8. Open the field diagram slowly until the bright area covers about 80% of the field.
9. Use the 2 adjusting screws on the condenser to move the circle of light to the centre of the field and then adjust the condenser up or down until the edge of the circle is sharpest. (see photo)
10. Open the field diaphragm until the bright area fills the entire field. (see photo)
11. Remove one of the oculars and looking from a distance, open or close the condenser diaphragm and you should see a Q. Replace the ocular.
12. Replace the filter.
13. Increase the light source intensity until it is suitable for reading microscopic specimens.
14. Kohler Illumination is achieved.