A photocatalyst having superior properties of adsorption and decomposition with respect to various substances is provided. The array has a top layer and at least one low layer including other ones of the sensors. Entries in the ROI database are created by an image locator and ROI classifier that work in tandem to locate images within the repository and extract the relevant information that will be stored in the ROI database. With such a structure, variations in behavior of each memory element are reduced.