ABSTRACT
In this chapter, the authors give an overview of a wave description of the measurement of radiance, referring details to publications. They point out a physical interpretation of the instrument function that is similar to the van Cittert–Zernike theorem. It is useful to examine the pinhole radiometer and the formalism the people have presented in two limiting cases. However, the authors explain some notation regarding the correlation operator and function. They demonstrates a consistent approach to incorporating the diffraction properties of the instrument in optical measurements. The authors used a remarkable analogy between the result of measuring radiance and the van Cittert–Zernike theorem that exploits the symmetry between an incoherent source whose radiance is being measured and the detector whose signal represents the measurement. It is likely that entirely similar considerations may apply to other signal detection processes where diffraction effects are important.
