The review articles that are being presented in this volume cover a broad
range of topics and it is hoped that many optics workers will find in it
something of special interest to them. Three of the articles deal with radia-
tion theory or with the interaction of radiation and matter; more speci-
fically these articles are concerned with the question of validity of Kirch-
hoff s law of heat radiation under non-equilibrium conditions, yith pos-
sible alternatives to quantum electrodynamics and with self-focusing of
laser beams in plasmas and in semi-conductors. Readers interested in
physiological optics will find in the present volume a review of spherical
aberration measurements of the human eye. More traditional areas of
optics are represented by articles that deal with interferometric testing of
smooth surfaces and with aplanatism and isoplanatism