Patent ID: 8773616

Claim:
An illuminating lens for spreading light from a light source in at least one direction perpendicular to a direction of an optical axis so that a surface to be illuminated is illuminated by the spread light, the lens comprising: a light entrance surface through which the light from the light source enters the lens; a light exit surface through which the light that has entered the lens exits the lens; and a bottom surface formed outside the light entrance surface and facing opposite to the light exit surface, wherein the light entrance surface has a first light entrance surface and a second light entrance surface, the first light entrance surface being a curved surface convex toward the light exit surface and perpendicularly intersecting the optical axis, and the second light entrance surface extending outwardly from an edge of the first light entrance surface and being connected obliquely to an inner edge of the bottom surface, in a cross section including the optical axis and taken along the one direction, θ1 has a negative value at the first light entrance surface and a positive value at the second light entrance surface, where θ1 is a refraction angle at which virtual light reaching the light entrance surface directly from a starting point on the optical axis corresponding to a position of the light source passes through the light entrance surface, and θ1 is defined as negative when θ1 is on the side of the optical axis with respect to a normal to the light entrance surface and as positive when θ1 is on the opposite side, and the following inequality holds: 0.5<sagY 60 /sagY 0 <0.8 where in the cross section including the optical axis and taken along the one direction, when θi is an angle between the optical axis and a straight line connecting an arbitrary point on the light exit surface and the starting point on the optical axis, sagY is a distance along the optical axis between the starting point on the optical axis and the arbitrary point on the light exit surface, sagY 0 is a sagY value at an angle θi of 0°, and sagY 60 is a sagY value at an angle θi of 60°.