Optical scanning device and image forming apparatus including the optical scanning device

An optical scanning device comprising:

• a light source emitting a light beam;
• a rotary polygonal mirror reflecting the light beam emitted from the light source to deflect and scan the light beam;
• an optical housing that houses the rotary polygonal mirror therein;
• a motor mounted on a bottom wall of the optical housing and driving the rotary polygonal mirror;
• an image forming lens housed in the optical housing and forming an image of the light beam reflected by the rotary polygonal mirror;
• and
• a Helmholtz resonator absorbing sound caused by rotation of the rotary polygonal mirror, wherein
• the Helmholtz resonator comprising a coupled Helmholtz resonator having a first resonance space and a second resonance space arranged in series in the optical housing,
• the optical scanning device including a translucent partition wall, a first partition wall, and a second partition wall each extending from the bottom wall of the optical housing to a top wall of the optical housing,
• the translucent partition wall, the first partition wall, and the second partition wall being arranged in this order from an optical-path upstream side toward an optical-path downstream side on an optical path between the light source and the rotary polygonal mirror,
• the first partition wall and the second partition wall each having a light passage opening formed therein through which the light beam passes,
• the first partition wall and the second partition wall constituting a part of a wall forming the first resonance space,
• the translucent partition wall and the first partition wall constituting a part of a wall forming the second resonance space,
• one of the first and second resonance spaces being configured to resonate at a frequency of a rotational speed of the motor, and
• another one of the first and second resonance spaces being configured to resonate at a generated frequency of a wind noise generated by the rotary polygonal mirror.