Corrections to classical radiometry and the brightness of stars

Abstract

By combining Fourier optics with classical radiometry, a simple, compact formula is derived for computing the absolute irradiance of diffracted and aberrated images in optical systems. Within appropriate limits, the formula reduces to the familiar equations of classical radiometry and of physical optics. It is argued that the approach presented is pedagogically appealing as it combines the principal results of geometrical optics, physical optics and radiometry into a single equation, thus, providing a convenient and simple means of describing imaging phenomena at the level of an advanced undergraduate or introductory graduate course on radiometry. A practical example concerning the image irradiance of stars is discussed.

Image irradiance in the absence of aplanatism and isoplanatism

“…In previous studies [18,19], the author derived a formula for image irradiance given by the convolution operation…”

“…Thus, this limiting condition of equation ( 3) is consistent with diffraction. Now, consider the condition of having a non-isoplanatic image, which had not been studied by the author previously [18,19]. In the case of non-isoplanatism, it is well-known that the relative image distribution is given by a superposition integral [21].…”