Correction is accomplished by using two spatial light modulators in series. The second SLM restores the original, or desired phase relationship between pixels. The content covers various types of SLMs, including liquid. The spatial light modulators developed at Fraunhofer IPMS consist of arrays of micromirrors on semiconductor chips, with the number of mirrors varying from a few hundred to several million depending on the application. A simple example is an overhead projector transparency.