A tray-positioning device comprises a driving unit and a positioning unit, wherein the positioning unit provides a plurality of sidewalls that correspond to a plurality of upper sidewalls of a tray. Polyareneazoles, filaments and yarns are also disclosed. A display frame SC displays a currently captured picture of an object, files P11 and P12, and the icon of the folder F1. A controller controls the output of a drive signal for causing operation of the light source, according to the electrical contact between the switch contacts and the angular velocity signal.