| 摘要 |
PURPOSE:To reduce the lock-in frequency by moving the first and second reflecting mirrors in a normal direction of an annular optical path in push-pull manner, and further moving any mirror in a tangential direction to alter the phase relation of representative scattered light of both mirrors. CONSTITUTION:A reflecting mirror 15 is controlled in a normal direction, the oscillating state due to the variation in the annular optical path length 22 is produced by the mirror 17, and the mirror 15 is set to the optimum optical path length. When actuators 24, 26 are driven synchronously in reverse phase by controllers 30, 31 in the optical path constant state and the mirrors 15, 16 are cooperated in reverse direction in the normal direction, the phase relationship of the representative scattered waves of the mirrors 15 and 17, 16 and 17 is altered to obtain the minimum lock-in frequency state. Then, the mirror 15 is slightly driven at 26 in the tangential direction, the mirrors 15, 16 are again vibrated in the normal direction to obtain the minimum lock-in frequency value. The minimum value of the minimum values at the positions of the tangential direction of the mirror 15 is repeatedly obtained as true minimum value, and the mirrors are controlled to the control state of this time. According to the construction, the lock- in frequency can be remarkably reduced with the present technique, and the performance of the light angle speedometer can be remarkably improved. |
