A convex mirror is provided on the front of the auxiliary mirror body.
The tracking is controlled by means of an auxiliary mirror (17) guiding an auxiliary beam (18) to a target (19).
An auxiliary turn signal lamp is provided on the lower surface of the front of the auxiliary mirror body.
Furthermore, a projection light path between the electronic projector and the polygonal mirror is formed by refracting light through an auxiliary mirror.
An auxiliary mirror body is placed in the holding space, is subjected to power transmitted from the motor through a chain, and is protruded from the holding space to a position under the guide groove by the motor.
The drifts for at least one surrogate mirror in a first mirror are measured.
The working mirror carries working light in a working path and the surrogate mirror carries test light in a calibration path.