Corrections of size-of-source effect and distance effect in radiometric measurements of radiance

Many optical instruments used in quality control of the optical radiation emission level of several devices are limited by the so-called size-of-source effect (SSE) as well as the distance effect (DE) when we are dealing with very accurate measurements. Different authors have studied the SSE and DE and have proposed experimental methods that provide corrections for them. We describe a general method based on the partial coherence theory that allows us to describe and calculate the SSE and DE in any radiometric system with circular apertures. We show some experimental results that verify our proposal. Additionally, as a practical example, we present the corresponding DE and SSE correction factors for a particular geometry.