Patent ID: 8434911

Claim:
A lighting device, comprising: a light emitting diode for emitting light; and an illuminating lens for spreading light emitted from the light emitting diode so that a surface to be irradiated is irradiated with the spread light, wherein the light emitting diode and the illuminating lens satisfy the following inequality (8): 0.3 <D/t< 0.9 (8) where D is a maximum width of a light emitting surface of the light emitting diode, and t is a center thickness of the illuminating lens, the illuminating lens including: a light entrance surface through which the light emitted from the light emitting diode enters the illuminating lens; and a light exit surface through which the light that has entered the illuminating lens exits the illuminating lens, the light exit surface being rotationally symmetric with respect to an optical axis, wherein the light exit surface has a concave portion and a convex portion, the concave portion intersecting the optical axis, and the convex portion being provided around the concave portion to extend continuously from the concave portion, the light exit surface is formed in a shape such that when the light exit surface is divided into micro-segments in a cross section that includes the optical axis, wherein the micro-segments have respective curvatures C, a maximum curvature Cm among curvatures C is positioned outward from a midpoint of the convex portion, and the light exit surface satisfies the following inequality (4): 0.9 <Cm ×( n− 1)× d< 1.5 (4) where n is a refractive index of the illuminating lens, and d is a distance from a position of the light emitting diode on the optical axis to a center of a micro-segment with the maximum curvature Cm, and the midpoint of the convex portion being defined by a point that bisects a curve between one end of the convex portion and other end of the convex portion in the cross section.