A data recording and reproducing apparatus capable of correctly recording or reproducing data groups by linking divided data within a hard disk is provided. In low light conditions, keys can be difficult to distinguish. Based on this image, brightness distributions of the discharge beam are estimated on a plurality of lines in a Z direction that are set in different positions in an X direction, and a discharge center of the beam is found from the plurality of brightness distributions. The cover member is of minimal size with respect to the electrical box to minimize the cost of construction. The protected structure may be derived from document templates, document forms, or from a set of training documents. The light exit surface has: a concave portion intersecting the optical axis; and a convex portion provided around the concave portion to extend continuously from the concave portion.