Wavelength Verification Standards

Holmium Oxide Filter (CAL-HOF)

The HOF wavelength standard is a glass filter doped with Holmium Oxide and provides a NIST-traceable absorption spectrum that can be used to accurately calibrate the spectral output of the tunable light source used with Axometrics measurement systems.

CAL-HOF wavelength reference

The CAL-HOF has a distinct set of absorption bands across the visible spectrum.  The figure below shows the measured transmission spectrum of the CAL-HOF when measured using the TVS-2 light source with a 7 nm FWHM bandwidth. The absorption minimum near 537.6 nm is typically used for setting the calibration on the TVS-2. 

CAL-HOB absorption spectrum