A NEW TRACKING METHOD FOR HELICAL SCANNING OPTICAL TAPE-RECORDER

Using a new tracking method, high track density recording on an optica l tape has been achieved with a helical-scanning optical tape recorder (HS-OTR). In this recorder, the tape is wrapped around a drum, which has a high numerical-aperture objective lens of 0.50, without contact with the rotating part by means of air pressure. In both optical desig n, moving parts, both focus and tracking actuators, light source and r eproducing optics are placed outside the rotary drum. With this system , a high carrier-to-noise-ratio of 51 Db for 1 mum mark length has bee n achieved. Using the tracking method, which includes a starting point servo loop, written marks have been reproduced track by track with a 2 mum pitch.