A method for easily and quickly evaluating the wavelength variability properties of a wavelength-variable semiconductor laser is provided. Control current compensation data are stored in a programmable look-up table as a function of the physical parameter. The method and system are applicable to other consumable item systems employing various types of consumable items. The intermediate space is accessible through one or more openings to the intermediate space. A restoration step in which the used raw material is heated at a temperature that is not lower than \u2212100\xb0 C. The control circuit successively turns on the plurality of light-emitting panels, and controls the output currents of the DCDC converters in accordance with differences of the illuminance data acquired with the photosensor when the light-emitting panels are turned on.