An optical disc system includes a photo detector circuit of an optical disc drive and a signal processing system. The photo detector circuit is configured to generate at least one information-carrying signal from an optical disc assembly. The signal processing system is coupled to the photo detector circuit to obtain from the at least one information-carrying signal both operational information used to operate the optical disc system and data indicative of presence and/or characteristics of an investigational feature associated with the optical disc assembly. Methods and discs for imaging a biological or medical investigational feature are also provided.