An optical member including: a Fresnel lens sheet for deflecting and emitting deflected light, A louver for restricting a direction of light rays, where the louver restricts the traveling direction of incident light from the deflecting element to a direction that is parallel to the optical path of the incident light, and emits the restricted light. The reporter constructs and recombinant cells are particularly well suited for high-throughput screening assays, and detection of interaction between a substance and a cell surface receptor can be performed visually, by FACS, or by luminometry. With this arrangement, it is possible to make the route of a reflection light that has been reflected from the light incident surface of the optical filter deviate large from the route of an incident light that has been incident to the optical filter.