Hitachi Maxell showcased a working Stacked Volumetric Optical Disc (SVOD) prototype that promises to deliver terabyte storage, at CEATEC, Japan.
Hitachi Maxell has developed a way of providing terabyte-level storage capacity using multiple ultra-thin layer DVDs. By using nanoimprint technology, the company has reduced the thickness of a DVD to 0.092mm - 1/13th the thickness of regular DVDs - while maintaining the capacity of 9.4GB (4.7GB per side). Disc diameter is 12cm, the same as a regular DVD.
To keep the discs safe each is housed in a protective sleeve inside the cartridge. The cartridge slots into a dedicated drive (recorder) and the discs are pulled out of the cartridge automatically by a mechanism inside the unit and mounted into the drive.
The system features what the company calls Stacked Volumetric Optical Disc (SVOD) technology, which consists of 100 of the ultra-thin DVDs. The 100-disc cartridge offers up to near-terabyte level with 940GB of storage.
According to Hitachi-Maxell, the challenge for in the design of a read/write system for these discs was to keep the ultra-thin media stable while spinning. The goal is to make these filmy discs readable with standard optical head and driver LSI included in typical DVD systems. The answer was to clamp the disc on a transparent turntable made from glass with the same thickness and optical characteristics as the 0.6mm acrylic substrate used for DVDs, and then read the disc by using a laser under the turntable. The laser shines up through the glass/PET sandwich and reflects back down onto a sensor.
The individual discs are picked from the cartridge by an automated finger, slid onto the glass turntable and clamped with a magnetic chuck. Aerodynamic forces hold the disc flat and close to the turntable surface as it spins. Optical markers are used to align the disc and chuck with the turntable centre.
Because it takes around 10 seconds to change discs, the cartridge has onboard memory that buffers the data at around 100Mbps.
Hitachi Maxell claims that blue-laser HD DVD technology could boost cartridge capacity to 10TB (50GB for each double-sided disc).
Hitachi-Maxell also showcased a 300GB holographic disc. Developed with the contribution of Inphase technology, the disc can be recorded using a data transfer rate of 160Mbps. The 300G prototype has a diameter of 130mm. Hitachi-maxell claims that the Holographic Disc is able to reliably store data for 30 years.