A data storage cartridge for a data storage disk drive has a latent illuminance marker. A reflective surface on the cartridge increases the intensity of the irradiance on the marker and illuminance from the marker. A light source illuminates the marker and the marker emits phosphorescence. A photosensor...http://www.google.ca/patents/US6201662?utm_source=gb-gplus-sharePatent US6201662 - Latent illuminance discrimination marker with reflective layer for data storage cartridges
