Abstract: In a beam splitter for producing splitted light beams for each of first and second wavelength components of an incident light beam, first and second transparent blocks have first outgoing and second incident planar surfaces, respectively, which are bonded by an intermediate transparent layer with a band-pass layer and first and second subsidiary reflection layers interposed between the intermediate layer and the second incident planar surface and with the surfaces kept in parallel. Antireflection and primary reflection layers are formed on a first incident planar surface of the first transparent block that is parallel to the first outgoing surface. First and second semitransparent layers are formed on a second outgoing planar surface of the second transparent block that is parallel to the second incident planar surface. The incident light beam is directed from the antireflection layer towards the band-pass layer.

Abstract: In a beam splitter for splitting a single input light beam into a plurality of outgoing light beams, a transparent block has first and second planar surfaces substantially parallel to each other. Antireflection and reflection layers are laid on incident and reflection areas defined on the first planar surface while a plurality of partial semitransparent layers are attached to an outgoing area defined on the second planar surface. The incident light beam enters through the antireflection layer into the block and exits as the outgoing light beams through the partial semitransparent layers. At least one of the partial semitransparent layers has a width wide enough to at least two of the outgoing light beams. The partial semitransparent layers may be deposited on the first planar surface in the vicinity of the antireflection layer. In this event, the reflection layer is deposited on the second planar surface.