How to Install a 6" to 4" Bayonet Adaptor on Your Interferometer

By Zygo | Published: 2026-10-30

Category: How-to Guides

Learn how to safely install a ZYGO 6" to 4" bayonet adaptor to reduce your interferometer's aperture size for smaller optics testing.

Quick answer

To install a 6" to 4" bayonet adaptor on your interferometer, first ensure the instrument is powered off and the optical path is clear, then align the adaptor's bayonet lugs with the receiver slots, press firmly, and rotate clockwise until locked.

Why use a 6" to 4" bayonet adaptor?

A 6" to 4" bayonet adaptor lets you test smaller optics without swapping the entire interferometer head. It reduces the effective aperture from 6" to 4", improving measurement accuracy for smaller components by eliminating edge effects and stray light.

Common mistakes to avoid

Forcing the adaptor when it does not slide on easily can damage the bayonet lugs. Always check the alignment marks before applying pressure. Also, never install the adaptor with the interferometer powered on—laser exposure can be hazardous.

Installation steps

Power off and clear the optical path: Turn off the interferometer and wait for the laser to cool down. Remove any test optics or fixtures from the measurement area. This prevents accidental damage and ensures safe handling.
Inspect the bayonet receiver: Examine the 6" bayonet receiver on the interferometer for debris, scratches, or bent lugs. Use a lint-free cloth and isopropyl alcohol to clean the mating surfaces if needed. A clean connection prevents misalignment and light loss. Check for bent lugs before proceeding—damaged lugs can cause the adaptor to jam.
Align the adaptor lugs with the receiver slots: Hold the adaptor with the 4" end facing away from the interferometer. Look for alignment marks (typically a dot or line) on both the adaptor and receiver. Rotate the adaptor until the marks align, then insert the lugs into the slots. If the adaptor does not slide in easily, rotate it slightly—do not force it.
Press and rotate clockwise to lock: Once the lugs are fully inserted, press the adaptor firmly against the receiver and rotate it clockwise (about 30 degrees) until you feel a positive stop. You may hear a click. The adaptor should be snug with no wobble. Do not overtighten—the locking mechanism is designed for a firm hand-tight fit only.
Verify the connection and test: Gently tug the adaptor to confirm it is locked. Power on the interferometer and check the alignment using a flat reference optic. If the image is clear and centered, the installation is successful. If not, repeat the alignment step. If the image is off-center, the adaptor may not be fully seated—remove and reinstall.

Product facts

6" to 4" bayonet adaptor: The ZYGO 6" to 4" bayonet adaptor (part number 6500-0132-01) is designed to connect a 6" bayonet fitting to a 4" bayonet fitting. This allows you to quickly change your interferometer's aperture size without tools, making it ideal for labs that test both large and small optics.
6" to 4" bayonet adaptor