TWO-SPOT INTERFEROMETRIC OPTICAL DISK READOUT TECHNIQUE
Original Publication Date: 1985-Dec-31
Included in the Prior Art Database: 2004-Apr-04
Xerox Disclosure Journal
Feedback of diode laser produced light from the disk to the laser during readback is a major source of noice in magneto-optic storage systems. In order to use the same isolation scheme used in write-once technology; that is, and as shown in the drawing, a polarizing beam splitter and a quarterwave plate to produce circularly polarized light on the disk, this disclosure proposes a two-spot interferometric technique with the circularly polarized read spot and the circularly polarized reference spot both reflected off the disk. The read spot and the reference spot are provided by insertion of a small angle beam splitter between the quarterwave plate and the disk. The separation of the spots on the disk is such that the read spot falls on the data track and the reference spot falls on a portion of the disk not containing data.