Disclosed is a clad material for an LED light-emitting element holding substrate in which a plurality of layers composed of different materials are stacked and bonded via a metal layer to a III-V group semiconductor crystal surface, the linear expansion coefficient being 14\xd710\u22126K or less and the thermal conductivity at a temperature of 25\xb0 C. The steering power converter converts electric power supplied from the DC power source, and provides the electric power converted to a steering assist motor. 0 times the nominal bit diameter. The retaining sheath may be made of a cold drawn plastic at least along the path of travel of the fold portion in retracting the retaining sheath from over the stent device. The reflected pulse is detected at one or more detectors and a pulse characteristic of the pulse and a second value representative of when the reflected pulse arrived at the detector are recorded. A foreground region relating to an imaged object is estimated, a background region relating to other than the imaged object is estimated, and by using the image, the estimated foreground region and the estimated background region, a transition region disposed between the foreground region and the background region is calculated.