To achieve crisp, clear phase contrast images, your microscope must be equipped with the proper phase contrast components — and more importantly, they must be precisely aligned and centered. Each phase objective must be matched to its corresponding phase annulus. If they’re misaligned, your image won’t have the contrast you’re expecting.
Follow these simple steps to properly center your phase contrast system:
✅ Step-by-Step: Centering for Phase Contrast
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Start with Köhler Illumination (if available)
Before anything else, align your microscope for Köhler illumination. This ensures even illumination across the field of view — the foundation for good contrast and image clarity. Helpful VIDEO on setting Köhler
2. Insert the Phase Contrast Centering Telescope
Remove one of your eyepieces and insert the phase contrast centering telescope in its place. Example of a phase telescope
3. Focus the Centering Telescope
Adjust the telescope focus until both the phase plate and the phase annulus appear sharp and clearly defined.
4. Begin with the Lowest Magnification Phase Objective
Start with your lowest magnification phase objective — usually a 10x PH1. Make sure the corresponding PH1 annulus is selected on the condenser.
5. Observe the Phase Ring Alignment
Look through the phase telescope. You should see an image similar to the examples below:
6. Adjust for Alignment
If your system is misaligned:
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Locate the centering screws on your condenser. These are often two silver knobs or plungers.
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If your system doesn’t have built-in adjusters, insert the provided centering tools.
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Gently adjust until the rings align perfectly.
7. Repeat for Each Objective
Switch to the next phase objective, select the matching annulus, and repeat the centering process. Most objectives have a PH1, PH2 or PH3 that match the marking on the condenser. Here is a helpful VIDEO to explain
8. Replace the Eyepiece
Once all objectives are centered, remove the phase centering telescope and reinsert the eyepiece.
🔁 How Often Should You Check?
Once centered, your system should stay in alignment unless it’s physically tampered with or moved. However, it's good practice to periodically verify alignment — especially if it’s part of your lab's protocol.