Hideharu Takeshima

The 4.7 GB Recordable Digital Versatile Disc (DVD-R) for Multiple Speed Recording

We studied the characteristics of the 4.7 GB recordable digital versatile disc (DVD-R) with high-speed recording up to 4X (14 m/s) speed. We demonstrated that metal-azo dyes with either a small amount of heat generation or the low absorption show good recording characteristics, and also indicated the write pulses suitable for multiple speed recording.

Recordable Digital Versatile Disc for High Data Transfer Rate Recording

We studied the characteristics of the 4.7 GB recordable digital versatile disc (DVD-R) for a high data transfer rate higher than 44 Mbps. Using simulation, analytical pulse sequence and atomic force microscopy (AFM) measurement, we analyzed the thermal interference. We also used originally synthesized dye with low thermal interference and realized good recording characteristics with jitter values of around 8% at 66 Mbps recording and 11% at 89 Mbps recording.

Feasibility Study of High Density Land/Groove Recording on Magnetooptical Disks

Land/groove recording on a magnetooptical disk with polyolefin and polycarbonate substrates was demonstrated. The laser wavelength, numerical aperture of the objective lens and focused beam spot size were 680 nm, 0.55 and 1.15 µm, respectively. With a groove pitch of 1.3 µm, a carrier-to-noise ratio (CNR) of more than 45 dB with 0.6 µm mark length and crosstalk of less than -30 dB with 2.4 µm mark length were obtained. The effect of crosstalk cancellation in the polymer substrates was confirmed. Decreasing the vertical birefringence of the substrate improved the jitter and the CNR. The crosserase margin was 0.8 mW. It was identified that the CNR declined with the CNR phase shift.

Dependence of Signals from Embossed Recording Fields and Grooves on Filling of Aperture of Objective Lens

The dependence of signals from embossed recording fields and grooves on the filling of the aperture of the objective lens was studied using a simulation based on a scalar diffraction method. The results indicated that this dependence is too large to ignore and consequently, the difference in the filling D/W between testers should be considered for the correlation between testers.

Low-cost ultrahigh areal density optical disc system towards 400 Gbyte/disc

We introduce a new 400 Gbyte disc system, which has twice as much areal density as BDXL™ does, retaining the use of the conventional optical head and disc technology. Our proposal is based on the application of code modulations with enlarged minimum run length (d) and land/groove (L/G) geometry to increase linear recording density and track density by 1.5 and 1.33 times, respectively. Also, saw tooth wobble (STW) was introduced for a multilayered L/G disc system to suppress readout signal fluctuations. Here, we demonstrated that the linear recording density increased to 45.5 Gbyte/layer by applying d = 3 to a commercially available BDXL™. Also, we checked that crosstalk, which is a major concern in an L/G disc with a track pitch of 240 nm, was suppressed to below −30 dB by choosing the proper groove depth. Moreover, the investigation of the effect of track width modulation on the write/read performance demonstrated that an adverse influence can be suppressed by employing STW.

4X Speed Recording HD DVD-Recordable Media Using Dye Material

The optical disc for blue laser system using dye material is introduced. High PRSNR and low SbER value are obtained at 4X(26.44m/sec) recording.

Compatible 8.5-Gbyte double-layer recordable DVD disc

A single-sided double-layer recordable DVD disc with a storage capacity of 8.5 Gbyte has been developed. Backwards compatibility with the existing DVD read-only format has been achieved through the use of organic dye recording layers that have intrinsically low absorption at lasers wavelength used for recording and reading. We describe the disc technology that we have developed, present recording results for both layers, and discuss double-layer effects. We demonstrate for the first time the feasibility of a compatible double-layer recordable DVD disc.

Recordable digital versatile disc for high data transfer rate

The broadcasting of high-definition digital television has been recently introduced and its data transfer rate is 23 Mbps. As for the storage media, 30-40 Mbps data transfer rate is said to be preferable. Although 4.7 GB recordable digital versatile disc (DVD-R) will be soon available in the market, we investigated the potential of DVD-R for higher data transfer rate.

Characteristics of optical read-only media with PWM recording

Characteristics of optical read-only media (O-ROM) having both grooves for tracking and pits that represent data by length were studied. Servo signals were observed over a wide bandwidth up to the data clock frequency and, in addition, the surface structures of the disks were observed. These observations showed that servo signals depend not only on the depth of grooves but also on that of the embossed data pits. Optimizing the depths of pits and grooves based on the results of pit density dependency of servo signals is necessary to ensure good characteristics of pit and groove signals.