Optical Measurement of Radiometric Aperture Areas

Published

September 1, 2026

Author(s)

Ulf Griesmann

Abstract

The National Institute of Standards and Technology (NIST) calibrates the areas of radiometric and photometric apertures using an optical coordinate measuring machine, which provides direct traceabililty of aperture areas to the length unit meter of the International System of Units (SI). This measurement system combines a two-dimensional motion stage with laser interferometers for position feedback, and a high-magnification optical transmission microscope. For area measurements, apertures are mounted on the motion stage in the focal plane of an illuminator. The microscope is then used to locate points on the edge of the apertures in the coordinate system of the motion stage. The aperture area is calculated from a set of aperture edge positions that have been measured along the full length of an aperture's edge. This publication describes the measurement instrument, provides a summary of the general measurement procedure, and it documents the software algorithms that are applied in the measurements. The traceability of aperture area measurements to the SI, and the components of measurement uncertainty that contribute to the total measurement uncertainty stated in the calibration reports are explained.

Citation

Special Publication (NIST SP) - 250-102

Report Number

250-102

NIST Pub Series

Special Publication (NIST SP)

Pub Type

NIST Pubs

Download Paper

https://doi.org/10.6028/NIST.SP.250-102

Local Download

Keywords

radiometric apertures, aperture area, laser interferometry, optical microscopy, optical coordinate measuring machine

Citation

Griesmann, U. (2026), Optical Measurement of Radiometric Aperture Areas, Special Publication (NIST SP), National Institute of Standards and Technology, Gaithersburg, MD, [online], https://doi.org/10.6028/NIST.SP.250-102, https://tsapps.nist.gov/publication/get_pdf.cfm?pub_id=961177 (Accessed September 2, 2026)

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