US Patent 7446920 Optical deflector and optical instrument using the same

An optical deflector arranged to be relatively stably driven regardless of any environmental disturbance such as temperature, includes an oscillating system 160 having plural natural oscillation modes of different frequencies, a driving unit for driving the oscillating unit, and a drive control unit for supplying a driving signal to the driving unit, the oscillating system 160 including a first oscillator movable element 11 with a light deflecting element 22, a first torsion spring 12, a second oscillator movable element 13, a second torsion spring 12 and a supporting member 15, the optical deflector further including a distortion detecting element 25a and 25b for detecting mechanical deformation of the first and/or second torsion spring and a heat generating element 19, for stabilizing the frequencies of the natural oscillation modes and the state of scan to ensure stable sinusoidal-wave combined drive.