An umbrella frame includes a hub, a center pole coupled to the hub for supporting the hub, and a plurality of ribs disposable into the hub. According to the present invention, messages indicating the connection state, the power state and the sleep mode of the external device are displayed on a screen of the display apparatus to which a USB is applied. Additionally, the sliding bearing has a surface roughness Ra of not larger than 0. The image forming apparatus of the present invention adopts the optical multi-beam scanning device of the present invention. A switching sheet is located above the flexible circuit board, and capable of actuating the flexible circuit board to produce electrical signal.