One aspect of the invention relates to a method of forming P-N junctions within a semiconductor substrate. A double ended, tipless filament tube or arc tube light source incorporates a drawn-down tubular body, and one piece foliated leads with spurs for process handling and for spudding into a filament with stretched-out legs. The advantage of the continuous production method described here is, further, that the active regions of the active semiconductor layer are not exposed to unprotected solvents andor solvent vapors at any time during the production process. A highly heat conductive material having a thermal conductivity higher than that of the light transmitting resin is loaded between the semiconductor light emitting element and the recess. The smoothing unit does not perform the smoothing when the scanning unit scans a light beam in accordance with image data representing a halftone image.