An optical waveguide element capable of being coupled with optical fibers at high coupling efficiency is to be provided. Next, when both primary-side voltage and secondary-side voltage become the rated voltage, a contactor is actuated to interconnect a home power system with the commercial power system. The other layer is a boundary layer made up of pixels exhibiting foreground colors, foreground disparities and alpha values associated with the correspondingly located pixels of the depth discontinuity areas. The upper surfaces and the lower surfaces of the connector are inwardly recessed to form upper locking slots and lower locking slots.