<p><P>PROBLEM TO BE SOLVED: To provide an optical switch for accurately controlling the drive of a mirror device without being influenced by power variation of a signal of input light. <P>SOLUTION: A drive voltage determination part 6 gives perturbation (vibration) to a mirror 230 by supplying a cyclically changing drive voltage to micromirror devices 3a and 3b by a control device 7 in order to find the optimum drive voltage obtaining a rotation angle of the mirror 230 in which the intensity of output light is optimum. An output light measurement device 4 detects the intensity of the output light incident on an output port 1b and converts it into an electric signal. A filter 5 removes a signal frequency component of an optical signal from the electric signal. A drive voltage determination part 6 generates drive voltages for controlling the mirrors of the micromirror devices 3a and 3b to an accurate angle at each micromirror device 3a and 3b so that the intensity of the output light is the optimum value based on a signal where the signal frequency component is removed by the filter 5. <P>COPYRIGHT: (C)2008,JPO&INPIT</p>
