A phosphor element includes an electron hole injection electrode and an electron injection electrode disposed opposite to each other, an electron hole transport layer, a phosphor layer, and an electron transport layer stacked in this order from the side of the electron hole injection electrode toward the side of the electron injection electrode. The membrane separation system consists of an absorption system containing semi-permeable hollow fiber membranes through which is circulated a liquid absorbent. The first point has a predetermined relation to the projection device, and the second point has a predetermined relation to the interaction region. The upper and lower portions may be separated after use by applying a separating force, and are separately stackable and therefore take up less space during storage and transport. The sensor includes a conductor connected to the internal or floating ground so that EMF and leakage current are detected, thus preventing the ground fault circuit interrupter from tripping due to signals caused only by EMF and leakage current in the load circuit. Heat conductivity of an adhesive face region of the insulating sheet is smaller than heat conductivity of an inner region, other than the adhesive face region of the insulating sheet.