An optical element includes a dichroic surface formed by a multilayer dielectric film or the like and a polarized beam splitter surface formed by a multilayer dielectric film or the like. As one example, a method for controlling access to a storage medium is disclosed that includes calculating a point to point error amount, and generating a incremental error value based at least in part on the point to point error amount. Also preferably, the catalyst will be combined with a material selected from an acidic crystalline zeolite, an acidic silica molecular sieve and an acidic alumina. This causes the first and second component liquids to form the chemiluminescent compound and resulting light. The clock control circuit turns on both the first activation transistor and the second transistor for the predetermined period starting from the edge timing of the clock signal, and turns off at least one of the first activation transistor and the second activation transistor for a period other than the predetermined period. The method includes manipulating at least one of the streams to reduce the temporal difference until the temporal difference is less than a predetermined threshold and enabling a viewer of the first stream to interact with a viewer of the second stream regarding the program.