A housing assembly for use in a portable electronic device, includes base and a decorative element. The protective mask includes a mask body, a hoop mounted in the mask body, two angle adjustment members, and a head size adjustment device. Thus, the supporting plate is pressed against the photocathode plate, so that the photocathode plate is pressed against the light transparent plate by the supporting plate. A conductive pillar is located in the center of the contour in the second opening.