A method for calibrating a communication channel coupling first and second components includes transmitting a data signal from the first component to the second component on the communication channel, and sensing a characteristic, such as phase, of the data signal on the second component. The locking unit includes a locking member and a rotary member. This can reduce a thickness of resin between the upper polarizing plate and the cover plate, thereby reducing an extrusion of the resin in between the cover plate and the upper frame.