Optical device, control method of optical device, and image forming apparatus

A control method of an optical device, the method comprising:

• extracting, by an irradiation unit, a scan beam and a monitor beam used to monitor a light amount of the scan beam from laser beams output from a light source;
• irradiating, by the irradiation unit, the scan beam onto an irradiation target;
• measuring, by a measurement unit, a light amount of the monitor beam;
• predicting, by a prediction unit, the light amount of the monitor beam relative to a reference light amount of the laser beam based on two or more light amounts stored in a storage unit that stores a plurality of measurement results obtained from a plurality of measurement units when the laser beams are output in a plurality of different light amounts, in association with and the plurality of light amounts, each measurement result being associated with each of the two or more light amounts;
• and
• controlling, by a control unit, the irradiating of the scan beam such that the light amount of the monitor beam relative to the reference light amount of the laser beams is equal to a light amount of the predicted monitor beam.

An image forming apparatus comprising:

• an optical device;
• and
• an image forming unit that forms an image using a scan beam output from the optical device,
• the optical device comprises:
• an irradiation unit that outputs a part of laser beams output from a light source as the scan beam to the image forming unit and outputs the remaining part of the laser beams as a monitor beam used to monitor a light amount of the laser beams;
• a measurement unit that measures a light amount of the monitor beam;
• a storage unit that stores a plurality of measurement results obtained by the measurement unit when the laser beams are output in a plurality of different light amounts, by associating the plurality of the measurement results with the plurality of the different light amounts, respectively;
• a prediction unit that predicts the light amount of the monitor beam relative to a reference light amount of the laser beam using a plurality of the light amounts stored in the storage unit and the measurement results corresponding to the plurality of the light amounts;
• and
• a control unit that controls the irradiation unit such that the light amount of the monitor beam relative to the reference light amount of the laser beam is equal to the light amount of the monitor beam predicted by the prediction unit.