Belt meandering preventing device and image forming apparatus including the same

A belt meandering preventing device, comprising:

• a belt displacement detection unit detecting an amount of displacement in a belt width direction of an endless belt rotatably stretched over support parts;
• and
• a belt meandering correction unit correcting the displacement in the belt width direction of the endless belt based on the amount of displacement detected by the belt displacement detection unit, wherein
• the belt displacement detection unit includes
• a moving part moving in association with the displacement of the endless belt or an edge of the endless belt in the belt width direction, and
• optical sensors outputting signals with output levels corresponding to proportions of the moving part in optical paths of the optical sensors;
• the optical sensors are arranged such that the output levels of the optical sensors change as the endless belt is displaced in the belt width direction in a predetermined high-resolution detection range;
• and
• the belt displacement detection unit is configured to combine the output signals of the optical sensors such that a rate of change of an output level of the combined signal with respect to the amount of displacement in the belt width direction of the endless belt within the high-resolution detection range becomes greater than rates of change of the output levels of the respective optical sensors and to detect the amount of displacement based on the combined signal.