Convex Radius of Curvature

Overview

Verifying the radius of curvature of convex optics such as mirrors, lenses, and transparent domes is typically accomplished with either a Fizeau interferometer or a short coherence Fizeau interferometer.

Calculating Radius of Curvature requires two measurements: one at the confocal position (Location 1) and one at the cateye position (Location 2).

4D Technology Digital Radius Slides provide axial positioning resolution down to 10 nm. Vertical and horizontal slides work with 4D Technology’s 4Sight Analysis Software for easy, extremely accurate Radius of Curvature measurement.

With a traditional, phase-shifting interferometer, measurement data is acquired sequentially—a long enough process that vibration and air turbulence will degrade or even prevent measurement. The interferometer and all mounts must be situated on an air table to isolate the system from vibration.  Air isolation can be expensive—prohibitively expensive for very large optics or long measurement paths.

4D interferometers feature optional Dynamic Interferometry^®, which enables measurement data to be acquired simultaneously. Because acquisition speed is so fast, vibration is no longer an issue, and an isolation table is not needed.

The AccuFiz D short coherence Fizeau interferometer features an entirely on-axis design for excellent accuracy, particularly on highly curved surfaces. Dynamic Interferometry, standard on the AccuFiz D, enables measurement without vibration isolation over cavity lengths up to 2 meters.