Weight optimization here stands for optic design, i.e. creation of a new optical system, on the assumption that weight should be a minimum! This will be done only by means of traditional design methods, that is excluding the use of aspherical surfaces, plastic materials, mirrors, diffractive or similar elements! This demand for lowest possible weight is important with systems, that must be transported for example into space, as well as with handheld systems, for instance binoculars, riflescopes, but also with photographic lenses. Up to now, no theory exists which describes how this problem can be solved. Here, the essay begins with the fundamentals, after that the basic facts related to the weight of a lens are discussed, as well as references made to publications. At the end, two design examples are given, the first being a binocular. The second example shows, that even in hopeless cases sometimes a solution can be found.
The Glasgow Lens Design Problem is ofcurrent interest in a special field of optics: Microlithography. This field is accompanied by high economic interests. Companies often do not allow their employees to publish their work. And the problem perhaps was too special: a lens consisting only ofinirrors was asked. This reasons (and probably additional ones) led to the situation, that only 6 solutions were received. Nevertheless, this few solutions show the range ofpossibilities given by this statement of the problem.
The Berlin Lens Design Problem, the first problem posed at a European conference, differs slightly from the problems posed at the large international lens design conferences held in the USA. The problem: Decentered Center Element, created by Hannfried Zugge and myself, stresses the practical aspect of lens design. It is well known by experienced lens designers: image degradation is mainly due to decentering tolerances. Therefore, the knowledge of what happens if a lens-element is decentered is essential for the practical success of a lens which is to be manufactured. Of course, such a problem is handled today by a tolerancing program. But tolerancing an existing design is a post-process which doesn't change the design. On the other hand, up to today, no design procedure is known (at least in the literature) which makes sure that the design-process will create a lens, which can be manufactured easily. Also the Berlin Lens Design Problem doesn't change this state of the art. But dealing with the problem indeed may increase the knowledge about a decentered system, either reoptimized or not. The solutions received show that there is a practical value as well as a scientific one. In addition, we really hope that every contributor was, and hopefully every reader of this paper is, fascinated by this unusual problem.