OPTICAL SCANNER, IMAGE FORMING APPARATUS, IMAGE PROJECTION DEVICE, AND READING DEVICE

摘要

PROBLEM TO BE SOLVED: To provide an optical scanner that extends an effective scan angle while controlling the rate of change in the moving speed within a certain range, and makes the beam waist of scanning light easily maintained on a projection surface.SOLUTION: A vibration element 11 includes a first torsion beam 101 that rotatably supports a mirror part 21, a first vibration part 31 that holds the first torsion beam, and a second torsion beam 102 that rotatably supports the first vibration part. The vibration element 11 includes a first resonance frequency at which the mirror part 21 and first vibration part 31 rotate and vibrate at the same phase, and a second resonance frequency at which the mirror part 21 and first vibration part 31 rotate and vibrate at the reverse phase. The second resonance frequency is set to a frequency of four or five times the first resonance frequency. The mirror part 21 functioning also as a curvature variable mirror has its curvature controlled by a control signal in which a signal having a frequency of twice the first resonance frequency and a signal having a frequency of four times the first resonance frequency are overlapped with each other.