Abstract: A method is proposed for producing three-dimensional structures, especially microlenses, in a substrate using an etching process, at least one original shape having a known original surface shape being present initially on the substrate in a plurality of places. The etching process has at least one first etching removal rate a1 and a second etching removal rate a2 which are material-dependent, and of which at least one is changeable as a function of time. The original shape is converted to a target shape by the etching process, the original surface shape of the original shape and the target surface shape of the target shape to be reached being known before the beginning of the etching process. In order to achieve the target surface shape, at least one of the etching rates a2 or a1 is set by a change of at least one etching parameter calculated before the beginning of the etching process as a function of the etching time.