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. Beamsplitters are optical components used to split incident light at a designated ratio into two separate beams. Polarizing cube beamslitters have better polarization separation, but would be. My light source is beamed onto a 50/50 beam splitter behind which sits my camera but I cannot seems to eliminate ghosting from the surface of the beamsplitter.