Patent ID: 7276702

Claim:
A light receiving device for a model for receiving signal light and outputting an electric signal according to the signal light, comprising: a sensor for receiving the signal light on a detection surface and outputting a signal correlating to the signal light; and an optical element disposed on a front surface of the detection surface for leading the signal light to the detection surface, wherein the optical element has a reflecting surface slanting to the detection surface with respect to a sectional surface orthogonal to the detection surface in order to cause the signal light from a lateral direction of the detection surface to be incident on the detection surface after reflected on the reflecting surface, wherein the optical element has a columnar portion, one end surface of the columnar portion confronts the detection surface, the reflecting surface is composed of a boundary surface formed by disposing a recessed portion to an other end surface of the columnar portion, the optical element reflects the signal light entering the columnar portion from a side surface thereof on the boundary surface, and emits the signal light from the one end surface to cause the signal light to enter the detection surface, and the boundary surface has at least one flat surface and at least one curved surface arranged next to each other in a circumferential direction on the boundary surface.