These notes are written to help the user
understanding the metrology problems associated with measuring the reflectivity
and the scattering of a surface. They sometimes correct approximate or
misleading ideas about mirror s coating maintenance propagated by people who
take their bad habits for competence. For that purpose, they give precise
definition of terms and notions in accordance with scientific knowledge in
physics and radiometry. The author has more than 40 years experience in applied
physics, optics and metrology; he received is PhD in astrophysics in Liege, has
been Harvard and Smithsonian fellow and has been teaching in Liege and Paris
before founding and managing companies dedicated to optics.
Analysis of DiVittorio paper on reflectometry
and Walton published in 2004 as a symposium paper on Telescope maintenance
a comparison of the performance of three commercially available
reflectometers. This paper is a tissue of errors and shows clearly that
the authors have not the level required to understand metrology. This is
shown in details in the following analysis.
Application note #4
note has been written to introduce the user of IRIS scatterometer to the
basic of stray light definition and measurements. It contains some theory
and useful definition of terms. The main part of the note deals with
practical matters related to scattering measurement.
Application note #5
note is a general discussion of telescope’s coatings maintenance.
Scientific, technical and practical rationales are given and amply
developed that should kill some current ‘believes’ and confusions
about the subject. The notions of ‘specular reflectivity’ and ‘Total
integrated scattering (TIS)’ are scrutinized. All arguments are grounded
on actual measurements on mirrors and on extensive modelization.
Application note #6
||This note examines the
problem of measuring the Total Integrated Scattering (TIS) of an exposed
Application note #7
||This note analyses the
influence of the mirror 's curvature on the accuracy of specular
Application note #8
||This note analyses the process of "absolute" measurements of specular reflectance.