Patent ID: 8665302

Claim:
An optical device comprising: an irradiation unit that irradiates a part of laser beams output from a light source as a scan beam onto an irradiation target and outputs a 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 each of the laser beams is 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 a light amount of the monitor beam relative to a reference light amount of a 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, wherein the prediction unit predicts the light amount of the monitor beam relative to a reference light amount of the laser beam using only the plurality of the light amounts corresponding to the laser beam and the measurement results corresponding to the plurality of the light amounts.