Surface Error of Large Concave Optics and Parabolas

Overview

Verifying the surface quality of large, concave optical surfaces such as meter-class mirrors, and ground- and space-based telescope optics has traditionally required a large aperture interferometer.

A Twyman-Green laser interferometer can do the job much more affordably. Built-in Dynamic Interferometry® enables measurement over long paths in <30 µs, without expensive vibration isolation. 

PhaseCam Twyman-Green interferometers feature a beam ratio adjustment to produce excellent fringe contrast from highly reflective surfaces. A pellicle is not required.

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 PhaseCam Twyman-Green interferometers include Dynamic Interferometry^®, which enables all measurement data to be acquired simultaneously. Vibration is no longer an issue, and an isolation is not needed— a huge cost savings for very large optics or long measurement paths.

A Fizeau laser interferometer is also well suited for verifying the surface quality of small to medium diameter concave optics.