Abstract: A sensing method and device for sensing the position of an object are provided. The sensing device comprises a light source for generating a plane light, and a sensor unit disposed at one side of the light source. The sensing method comprises driving the light source to generate the plane light, forming a reflective light distribution by the object reflecting the plane light; and estimating a relative distance between the object and the light source according to the reflective light distribution.

Abstract: An electronic device includes a case having an opening, an electronic circuit and a dust cover. The electronic circuit is disposed in the case and includes a circuit board, a switch, and an expansion card slot. The switch and the expansion card slot are electrically connected at the circuit board. The opening exposes the switch and the expansion card slot. The expansion card slot includes an electrical connector used for electrical connection with an expansion card. The dust cover is detachably disposed at the opening The dust cover includes a cap portion, a press portion and an elastic portion. The cap portion closes the opening. The press portion faces the switch. The elastic portion is respectively connected to the cap portion and the press portion, so the press portion is capable of moving relative to the cap portion and hence has a trigger position and a release position.