Methods of placing computer equipment within a server room. The surface of the mounting stage to which the optical element is bonded is smoother than the bottom surface of the package to which the mounting stage is fixed. A method of blow molding is also described as well as articles made by the method. The gate turn-on voltage is determined based on a maximum value of the data voltage. Furthermore, to reduce a residual in-phase component of the obtained differential waveform, input gain adjusting circuits adjust an input gain of the first angular velocity sensing waveform J1 and an input gain of the second angular velocity sensing waveform J2 before these waveforms J1 and J2 are entered into the differential amplification circuit.