Patent ID: 7798679

Claim:
A light-emitting device, comprising: a light-emitting element and a light flux controlling member for controlling light emitted from the light-emitting element, the light flux controlling member having (i) a light-incoming surface from which the light from the light-emitting element enters the light flux controlling member and (ii) a light-outgoing surface from which the light being incident on the light-incoming surface is emitted from the light flux controlling member, the light-incoming surface having a concave curve part that is axisymmetrical with respect to a reference light axis of the light-emitting device, and the light-outgoing surface having (i) a convex curve part that is axisymmetrical with respect to the reference light axis and (ii) a recession continuing to the convex curve part, on a part encompassing an intersection of the reference light axis and the light-outgoing surface; R 1 monotonically decreasing as α 1 increases, at least in a range of α 1 <π/3, where an intersection of the reference light axis and an emission surface of the light-emitting element is a reference point; α 1 is an angle between the reference light axis and a straight line that passes through the reference point and an arbitrary point on the light-incoming surface; and R 1 is a distance between the reference point and the arbitrary point on the light-incoming surface; R 2 monotonically increasing as α 2 increases, at least in a range of α 2 <π/3, where α 2 is an angle between the reference light axis and a straight line that passes through the reference point and an arbitrary point on the light-outgoing surface; and R 2 is a distance between the reference point and the arbitrary point on the light-outgoing surface; and A 2 <1/√{square root over (n 2 −1)}, where n is a refraction index of a material forming the light flux controlling member; and A 2 =ΔR 2 /(R 2 Δα 2 ), where ΔR 2 is an increment of R 2 and Δα 2 is an increment of α 2 .