Prof. Dr. Adolf Lohmann celebrates his 75th birthday in April 2001. This date not only marks a very special birthday but also 50 years of his stimulating and motivating work in unconventional optics. Starting his scientific life around 1953 at the Technische Hochschule Braunschweig, he moved to California in 1963 and returned as professor for applied optics to Erlangen/Germany in 1972. After retiring, he has been active as guest scientist in many optics laboratories worldwide. With his amazing style in presenting optical problems he has attracted many students and even today he impresses the audience in his presentations. Many honours have been presented to him including the honorary membership of the German society of applied optics. This issue of OPTIK is therefore dedicated to Prof. Adolf Lohmann with several special papers related to and influenced by his work. Our best wishes are connected with this issue for good health and many more interesting problems in optics.