In a projector optical system comprising a digital micromirror device for modulating illumination light, a device having a polarization separating surface is provided for separating a luminous flux incident on the digital micromirror device and a luminous flux emitted from the digital micromirror device from each other. The word compel is an acronym of the words \u201ccompressed air and electricity\u201d. The angler is interactively led through the user interface to provide known information and angler selections. The resulting reliability and accuracy is superior to prior art static feature detection systems and methods.