Light-receiving devices, shielding plate, traffic support program, traffic support method, traffic support device, a navigation device and a communication device

By realizing the position location of setting the optimum boundary position by an inexpensive and simple mechanism precise mobile, make effective use of existing equipment. Receiving device (300), the shield (402) to shield a portion of the incident angle ([alpha] 1) or ([alpha] 2) less than the optical signal to the light receiving portion (401), the incident angle ([alpha] 2) or more all optical signals shielding, the shielding plate (402) by shielding a portion of the incident angle (.beta.1) or (.beta.2) less than the optical signal to the light receiving portion (401), the incident angle (.beta.2) above all optical signals shields, the boundary position no longer receive the light signal can be accurately detected.