This video is a tutorial on how to align the illumation optics in the microscope for Koehler illumation. Koehler illumination provides even illumination across the field of view, and is critical for obtaining high quality phase and DIC images.
A video on the role of condenser aperture diaphragm in transmitted light microscopy will be coming soon!
A nice review on Koehler illumination: https://doi.org/10.1002/0471143030.cb0401s00
0:00 Introduction
0:17 What is Koehler illumination?
1:29 Why should I care about Koehler illumination?
2:54 Optics 101
4:50 How does a lens form an image?
6:08 The critical parts & pieces
7:50 The parts you need to align
8:32 Uneven illumination
9:47 What are conjugate focal planes?
10:54 Conjugate illumination planes
12:32 Conjugate image planes
13:32 All the conjugate focal planes
14:50 Koehler illumination step-by-step
16:44 Finding the parts
17:59 What you should see when looking in the scope