Every day we meet people who have been using their compound microscope for years and not realised it’s full potential.  If your microscope has an adjustable field iris diaphram (often referred to as an iris diaphragm or collector) and an aperture diaphram, follow the instructions below to set it up correctly for ‘Koehler Illumination’ and be prepared for a remarkably improved image!

Not sure what the above two parts are on your microscope?  Here’s a diagram listing the various parts:

So, let’s get started:

1. Position a specimen on the stage and focus with the 10X or 4X/5X objective.

1. Locate the field iris/collector diaphragm control.  Close the diaphragm right down while looking down the microscope – you will see a dark circle encroaching on the image.

1. The edge of the circle should be sharp; if not, focus the condenser until the circle edge is at its sharpest (usually just under the slide).

1. The circle should be in the centre of the image; if not, centre the condenser using the condenser adjustment lever(s).

1. Open up the diaphragm so that the circle is just outside of the field of view (making sure the circle stays centred).

1. Locate the aperture diaphragm ajustment lever; when you move this the image should appear lighter/darker.  Position the aperture diaphragm so that it is just before the image begins to appear darker.

1. Adjust the aperture diaphragm (only) accordingly each time you change the objective.

​Then admire and show off your new, improved image!  If you found this helpful then others will too so be sure to share this blog post with friends/colleagues/Facebook groups that might find this useful….thank you in advance and happy viewing!

Got a question?  Please phone us on 01284 789697, or email us sales@gtvision.co.uk