| 主权项 |
1. A surface light source device comprising:
a cavity surrounded by a bottom surface, side surfaces and a top surface, with a light emitting area being formed on the top surface; a plurality of light emitting devices, each having a light emitting element and a light flux controlling member that controls a distribution of light emitted from the light emitting element, the plurality of light emitting devices being arranged on a pair of side surfaces facing each other inside the cavity such that an optical axis of the light emitting element extends from one of the pair of side surfaces to the other; a reflection member that forms a part or all of the bottom surface; and a light-emitting planar member that has a light diffusing property and optical transparency and forms the light emitting area, wherein: the reflection member is protruded toward an inside of the cavity such that light emitted from the light emitting device is reflected toward the light emitting area, and has a ridge line that is parallel to the pair of side surfaces and the top surface, with an apex being formed with a curved surface including the ridge line; when an emission angle, increasing from the optical axis to the light-emitting planar member side, relative to the optical axis of a light beam emitted from the light emitting device, is set as θ, a distance between a position where a light beam having been emitted from the light emitting device at emission angle θ and having been specularly reflected once at the reflection member reaches the light-emitting planar member and an end part closest to the light emitting device, of the light emitting area in the light-emitting planar member, is set as L1, and an emission angle of a light beam, being emitted from the light emitting device to be tangential to the reflection member, relative to the optical axis is set as θ1, ΔL1 /Δθ is gradually decreased in association with a decrease in the θ within a certain range whose upper limit is θ1; and when a distance between a position where a light beam having been emitted from the light emitting device at emission angle θ and having been specularly reflected once at each of the light-emitting planar member and the reflection member reaches the light-emitting planar member again and an end part closest to the light emitting device, of the light emitting area in the light-emitting planar member, is set as L2, and an emission angle of a light beam, being emitted from the light emitting device to be reflected at the light-emitting planar member before reaching the ridge line of the reflection member, relative to the optical axis is set as θ2, ΔL2/Δθ is gradually increased together with a decrease in L2 in association with an increase in the θ within a certain range including the θ2. |
