In an interference filter having a layer with an area consisting of a porous material extending from the surface of the layer to the interior, the dimensions of the porous layer area in a direction normal to the layer surface have different values to provide for varying reflection or, respectively, transmission characteristics. Transmitting endpoints include switching information in their transmitted media to indicate if temporal level switching at a decoder can occur at any frame of the transmitted encoded media. The methods of monitoring flow rates are also applied to methods and systems for continuously monitoring and controlling these flow rates in electroosmotically driven microfluidic systems. Each of the pin spacers is constructed of two pin-like protrusions, and a coupler which couples the two pin-like protrusions to each other at the parts of these pin-like protrusions as are remote from the end parts thereof on the side of the cross dichroic prism. By passing DC currents through the positive conductive plates and cathode conductive plates so as to flow in the opposite directions, effective inductance of the positive conductive plates becomes smaller than its self-inductance.