A compact optical tracking system for magnetic tape is disclosed which is
independent of the magnetic format and head structure which can generate
a position error signal without encoding on the servo track. A plurality
of optical servo modules is arranged in a linear array. Each optical
servo module contains an optical beam source, preferably a laser, an
optical beam interference composite hologram for producing a
predetermined pattern on a target and at least one detector for detecting
an optical beam reflection. A position correction signal is generated by
one or all of the optical servo modules for re-positioning a magnetic
head, which reduces the error in the correction signal from tape
degradation and dimensional changes. Reference grating may be added to
provide further position calibration prior to the tape being positioned
over the head. Refinements to the tracking system include outboard heads
which are added for additional position references and which may include
index marks for initial positioning in association with a desired servo
track.