Search

We have developed a new error correction method (Picket: a combination of a long distance code (LDC) and a burst indicator subcode (BIS)), a new channel modulation scheme (17PP, or (1, 7) RLL parity preserve (PP)-prohibit repeated minimum transition runlength (RMTR) in full), and a new address format (zoned constant angular velocity (ZCAV) with headers and wobble, and practically constant linear density) for a digital video recording system (DVR) using a phase change disc with 9.2 GB capacity with the use of a red (λ=650 nm) laser and an objective lens with a numerical aperture (NA) of 0.85 in combination with a thin cover layer. Despite its high density, this new format is highly reliable and efficient. When extended for use with blue-violet (λ≈405 nm) diode lasers, the format is well suited to be the basis of a third-generation optical recording system with over 22 GB capacity on a single layer of a 12-cm-diameter disc.

We detected bits sized at 0.237 µm bit length and 0.85 µm track pitch recorded by magnetic field modulation on a magneto-optical disk with a 690-nm laser diode and 0.60-numerical-aperture-objective using a partial-response maximum-likelihood detection method. We confirmed that the optimum partial-response for this high linear density had four coefficients of 1 by analyzing difference metrics of error critical paths. The recorded bits with areal density of 5.6 bit/µm2 were also detected at a low error rate, which combination is 0.237-µm bit length and 0.75-µm track pitch. Its write power tolerance is limited to ±22%.

SNR of a polycarbonate MO disk with a narrow track of 0.85 μm and with a quadrilayer structure was improved by optimizing and improving the groove geometry, film composition / thickness, and birefringence of the substrate. By using a 690 nm LD, an NA of 0.55, magnetic field modulation, and RLL(1,7) coding, a high areal recording density of 2.5 Gbit/in2 was obtained. Moreover, the PRML detection of PR(1,2,1) increased the density up to 2.9 Gbit/in2.

Using a new tracking method, high track density recording on an optical 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 the optical design, moving parts, both focus and tracking actuators, light source and reproducing optics are placed outside the rotary drum. With this system, a high carrier-to-noise-ratio of 51 dB for 1 µm mark length has been achieved. Using the tracking method, which includes a starting point servo loop, written marks have been reproduced track by track with a 2 µm pitch.