An inkjet image forming apparatus and a high resolution printing method for the same. In some embodiments, clusters of consumers with fit characteristics similar to the subject consumer are identified, using one or more data clustering algorithms, based on any of numerous consumer attributes ). A purge medium is used to reduce or eliminate optical distortions and to reduce, andor eliminate oxidation of the target specimen. A protective cap is disposed over the turning handle and provides access to the at least one released locking opening, a shape of the protective cap being such that the protective cap conforms to a shape of the turning handle and is fixed to the housing via a positive connection. The invention provides a light source device that can be made thin and is capable of increasing the directivity of emitted light in two dimensions.