A mark object that serves as a marker for a guidance point on a set route is specified, and coloration information related to a coloration of the mark object is acquired. The AC light emitting device includes at least four substrates. The relative phases of the two radiation beams and other features of the beams are measured in a detector to provide information on the properties of the substrate surface. The controller monitors resistance of the internal resistor to determine continuity between the connector and the shorting element.