Patent ID: 8569649

Claim:
An optical device comprising: an oscillator for emitting a laser beam; a branching mechanism by which the laser beam emitted from the oscillator is branched into two laser beams, wherein the branching mechanism includes a beam splitter by which the laser beam oscillated from the oscillator is branched into a first branch beam going ahead through transmission and a second branch beam going ahead through reflection; and a condenser for condensing the two laser beams going out of the branching mechanism, wherein the branching mechanism further includes: a first mirror by which the first branch beam going out of the beam splitter is reflected to go again toward the beam splitter, a second mirror by which the second branch beam going out of the beam splitter is reflected to go again toward the beam splitter, a rotating unit for integrally rotating the first mirror and the second mirror, with a laser beam branch point in the beam splitter as a center of rotation, and a control unit for rotating the rotating unit to change an angle of incidence of the first branch beam on the first mirror and an angle of incidence of the second branch beam on the second mirror so as thereby to control an angle formed between the first branch beam reflected by the beam splitter after being reflected by the first mirror and the second branch beam transmitted through the beam splitter after being reflected by the second mirror; and wherein the condenser is disposed on optical paths of the first branch beam which has been transmitted through the beam splitter, has thereafter been reflected by the first mirror to be again incident on the beam splitter, and has been reflected by the beam splitter to go out of the beam splitter, and the second branch beam which has been reflected by the beam splitter, has thereafter been reflected by the second mirror to be again incident on the beam splitter, and has been transmitted through the beam splitter to go out of the beam splitter.