Self-Study Manual on Optical Radiation Measurements: Part I. Concepts, Chapter 10. Introduction to Coherence in Radiometry

摘要

This is the sixth in a series of Technical Notes (910- ) entitled 'Self-Study Manual on Optical Radiation Measurements'. It contains Chapter 10 of Part I of this Manual. In this chapter we introduce the reader to the basic field quantity of the theory of partial coherence, the cross-spectral density function, and show how it is used to describe radiation fields. We discuss the propagation of cross-spectral density along a beam and illustrate this propagation with calculations of diffraction effects in a number of simple aperturing and imaging examples. For instance, we treat in considerable detail one of the most common radiometric situations in which coherence effects can manifest themselves, the measurement of the slit-scattering function of a monochromator. Among other things, this treatment shows that laser illumination of a monochromator entrance slit must be nearly on-axis to avoid serious slit-scattering function distortions. Finally, we present the relationships between the cross-spectral density function and the classical radiometric quantities, such as spectral radiance.