A method of reducing variation in optical power levels across a group of light emitting diodes includes testing each respective one of the light emitting diodes to determine an optical power level produced by that light emitting diode when connected to an electrical power source. A drive force generationtransmission mechanism includes a generator that generates the electric power by utilizing the force applied from the manual operation means and motors driven by the electric power generated by the generator. The rear face side of the welding part is covered by a backing member having a thermal conductivity of 30 WmK or lower, and then a columnar probe of a rotary tool comprising an Ir alloy is inserted into the front face side of the welding part to weld the metallic materials together. A charged particle beam is selectively directed close by one of the rows of posts, causing them to resonate and produce radiation. The object shape data is correlated with the object texture data to construct the three-dimensional digital model stored in a memory of a computer system.