| 摘要 |
565,254. Electric light fittings. HOLOPHANE, Ltd. (Holophane Co., Inc.). June 9, 1943, No. 9268. [Class 75 (ii)] A luminaire especially suitable for long light sources comprises an inverted reflecting trough arranged above the light source and a prismatic plate arranged across the mouth of the trough provided with alternate surfaces arranged to refract direct light rays away from the nadir while the intermediate surfaces refract reflective rays to the other side of the nadir at angles similar to the refracted direct rays on that side. In Fig. 1, the luminaire comprises a substantially semi-elliptical specular reflector 12 having a light source LC at its focus and a prismatic plate 20 along its mirror axis, the plate 20 being provided along its upper surface with prismatic ribs 22. The direct rays 24, 25, 26 impinging on the rib surfaces D facing the axial plane emerge as parallel rays 24b, 25b, 26b and the reflected rays 14a, 15a, 16a imping- ing on the intermediate rib surfaces R emerge as parallel rays 14c, 15c, 16c at substantially the same angle, approximately 55 degrees, as the direct rays on the other side of the axial plane. If the conjugate focus of the reflector is nearer to or farther from the plate than the light source or is offset from vertical axis of symmetry of the reflector, the surfaces D, R would be at different angles to the vertical. The surfaces D, R may be at such angles that the angles a, b of the emergent rays are unequal. |
