Provided is an optical imaging pen configured to detect information encoded with infrared ink on a page. A main beam and sub-beams generated by the one-plane, two-wavelength diffraction grating and reflected from the surface of an optical disc are incident on corresponding light receiving elements among which the one to receive the main beam and those to receive the sub-beams are relatively shifted in a linear-speed direction of the optical disc. These steps are achieved by either rotating only a grill member in a first direction relative to the drop tube member, or by manipulating only the grill member. The content containers are filtered such that only the versions of the context-aware content that correspond to the output capabilities of the target output device are made accessible to the user. The second signal source circuit includes a second load therein establishing a voltage level at a second node when a second current flows through the second load.