The distance dependences and spatial uniformities of spectral irradiance standard lamps
Howard W. Yoon, Gary D. Graham, Robert D. Saunders, Yuqin Zong, Eric L. Shirley
We describe the characterization of a group of NIST spectral irradiance lamps at longer distances and larger angles than are typically issued by NIST. The spectral irradiances from the FEL lamps were measured from 50 cm to 150 cm at 8 different distances using a cosine-corrected filter radiometer to determine if the lamps adhere to the inverse square law. Using the filter radiometer, the spatial uniformities of the FEL lamps were also mapped over a 20 cm square area at 135 cm, 143 cm and 151 cm. In the NIST gonio-spectroradiometer facility, selected lamps were also mapped for the angular dependences of the spectral irradiances at a distance of 123 cm using a spectrograph which measures from 300 nm to 1100 nm for comparisons to the filter radiometer measurements. Using these measurements, an uncertainty budget for the distance and the angular uniformity correction of the FEL lamps was developed.