06424492 is referenced by 3 patents.
A data storage disk having a latent illuminance discrimination marker for determining whether the data storage disk is suitable for use in a disk drive. A light source illuminates the marker and the marker emits illuminance, preferably as phosphorescence. A detector detects the emitted illuminance, and a predetermined characteristic of the marker in the frequency domain is determined. The frequency domain response may be either a phase response or an amplitude response, or both. The frequency domain response provides identification of different types or generations of data storage disks or provides a secure keying mechanism for authorized access to proprietary software.