Patent ID: 7526155

Claim:
A rotary joint for transmitting optical signals, comprising: a stationary part; and a rotary part which is rotatable about an axis against the stationary part, wherein the rotary part includes a rotary base plate, a light transmissive cylindrical member formed with a predetermined thickness, the light transmissive cylindrical member being fixed on the rotary base plate coaxially with the axis, and a first optical unit arranged on a first end of the light transmissive cylindrical member in an axial direction thereof and fixed on the rotary base plate, and the stationary part includes a stationary base plate arranged closely to a second end of the light transmissive cylindrical member and a second optical unit fixed on the stationary base plate close to the second end of the light transmissive cylindrical member, the second optical unit pairing with the first optical unit of the rotary part, whereby the optical signals are transmitted between the first optical unit and the second optical unit through the light transmissive cylindrical member, wherein at the rotary part end, a first light emitting element and a first light receiving element, which are included in the first optical unit and arranged in opposite positions on a circumference, having a light emitting part and a light receiving part of those elements provided on a base plate of the rotary part, close to the first end of the cylindrical member; at the stationary part end, a second light emitting element and a second light receiving element, which are included in the second optical unit and arranged in opposite positions on a circumference, having a light emitting part and a light receiving part of these elements provided on a base plate of the stationary part, close to the second end of the cylindrical member; and the cylindrical member having an outside surface and an inside surface of a lateral side thereof reflecting light of signals to be transmitted between the first light emitting element and the second light receiving element and between the second light emitting element and the first light receiving element.