Optical scanning device

1. An optical scanning device, comprising:

a mirror configured to reflect laser light;

a mirror supporting part configured to support the mirror;

a pair of torsion beams configured to support the mirror supporting part on both sides in a direction of an axis thereof and to be twisted to swing the mirror supporting part around the axis; and

a rib provided on a back surface of the minor supporting part, the rib including a longitudinal part provided in a direction parallel to the axis.

2. The optical scanning device as claimed in claim 1 ,

wherein the rib further includes an arc part configured to connect edge portions of the longitudinal part.

3. The optical scanning device as claimed in claim 1 ,

wherein the rib includes a part provided in a direction orthogonal to the direction of the axis.

4. The optical scanning device as claimed in claim 1 ,

wherein the rib further includes a transverse part extending through a center of the mirror supporting part in a direction orthogonal to the direction of the axis.

5. An optical scanning device, comprising:

a mirror;

a mirror supporting part configured to support the mirror;

a pair of torsion beams configured to support the mirror supporting part on both sides in a direction of an axis thereof and to be twisted to swing the mirror supporting part around the axis;

a movable frame configured to surround the minor, the mirror supporting part and the pair of torsion beams;

a pair of first drive beams, the first drive beams having first edges connected to and supported by inside walls of the movable frame and being configured to generate a driving force to swing the mirror supporting part in a first direction; and

coupling beams to couple second edges of the first drive beams with the torsion beams and to transmit the driving force to the torsion beams,

wherein a planar shape of each first drive beam includes a curved shape part cut inward at a position on a side connecting the movable frame with each coupling beam and near the movable frame.

6. The optical scanning device as claimed in claim 5 ,

wherein the planar shape of each first drive beam includes a part cut most inward at a position on the side near the coupling beam.

7. An optical scanning device, comprising:

a mirror;

a mirror supporting part configured to support the mirror;

a pair of torsion beams configured to support the mirror supporting part on both sides in a direction of an axis thereof and to be twisted to swing the mirror supporting part around the axis;

a movable frame configured to surround the mirror, the mirror supporting part and the pair of torsion beams;

a pair of first drive beams configured to generate a driving force to swing the mirror supporting part around a first axis thereof;

second drive beams coupled to the movable frame from an outside thereof and configured to swing the mirror supporting part around a second axis through the movable frame; and

a rib crossing in a direction of the first axis and a direction of the second axis on a back surface of a coupling part between the movable frame and each second drive beam.

8. The optical scanning device as claimed in claim 7 ,

wherein the movable frame includes an outer wall extending in a direction different from the direction of the first axis and the direction of the second axis, and

wherein the outer wall and the rib form a triangular hollow.

9. The optical scanning device as claimed in claim 7 ,

wherein each first drive beam generates a driving force by resonant oscillation and each second drive beam generates a driving force by non-resonant oscillation.