The simplest solution for a camera or microscope as well visually observing the image, for example a retinoscope, is to employ cross polarisation. Painting matte black or using soot surfaces or even felt fabric seldom achieve adequate cancellation. The problem is you are really asking for something that does not exist. Polarizing cube beamslitters have better polarization separation, but would be. A beam splitter or beamsplitter is an optical device that splits a beam of light into a transmitted and a reflected beam. It is a crucial part of many optical experimental and measurement systems, such as interferometers, also finding widespread application in fibre optic telecommunications.