Homogeneity is a test of the consistency of a material sample’s or optical component’s refractive index. When an optic is used in transmission, any variations in the material’s index will cause differences in the refraction of a wavefront passing through the material. These variations translate directly to errors in the wavefront passing through the optic.
In transmission, however, error is introduced through imperfections in the shape of the sample’s front and back surface as well as variability in index. Several measurements are required in order to separate out the variability caused by each surface and the material itself. The testing can be challenging as alignment between the various measurements must be absolute in order to avoid adding further error.
4D’s AccuFiz SIS Fizeau interferometer employs a short coherence source that isolates the surfaces of plane parallel optics and bulk samples. The source makes it possible to measure both optical faces independently, and to subtract them from the overall error to achieve high repeatability homogeneity assessment from three measurements, all acquired with a single setup.
Added Technical Resources
Measuring Homogeneity with the AccuFiz
A new technique simplifies measurement of homogeneity to decrease measurement time and improve repeatability.
Products for Homogeneity
AccuFiz with a Surface Isolation Source (SIS) uses short coherence to isolate the plane parallel optics, providing a capability to measure homogeneity with only three measurements.
Able to measure two plane parallel surfaces and the distance between them, FizCam is able to measure homogeneity in fewer steps, providing faster results and more repeatability.