System and method for detecting the presence of a data-storage cartridge using phase-rotated polarized light

A disk drive comprising:

• a source of polarized light;
• a detector being in selective optical communication with said source of polarized light, said detector detecting polarized light having predetermined characteristics:
• a data-transducing head for interfacing with a data-storage cartridge inserted into said drive;
• a head-retraction system having an actuator for positioning said data-transducing head proximate said data-storage cartridge;
• and
• an electrical circuit for controlling the operation of said head-retraction system, wherein said data-storage cartridge comprises a reflective marker and said head-retraction system is activated by said electrical circuit when said data-storage cartridge is inserted into said disk drive so that said reflective marker optically couples said source of polarized light and said detector.

A method for detecting the presence of a data-storage cartridge in a disk drive, comprising the steps of:

• directing polarized light at a reflective marker disposed on said cartridge;
• measuring an amount of said polarized light that is reflected by said reflective marker;
• and
• determining whether said amount of said polarized light that is reflected by said reflective marker exceeds a predetermined threshold.