Stacked Volumetric Optical Discs (SVOD)
Hiroyuki Awano a, Hiroshi Ido bab

Toyota Technological InstituteResearch and Development Division, Hitachi Maxell Ltd.

ABSTRACT
Data capacity of a developing optical disk (multi-layer, holographic, etc.) is increasing toward to a few 100
GB, however that of HDD and computer tape (LTO) is already beyond 1TB. From the data storage view
point, data capacity of optical disk should be increased rapidly. Therefore, we had proposed the stacked
volumetric optical discs (SVOD) with sub tera Byte. By using a special cartridge in which is included 100
thin optical discs of 25GB data capacity, the optical disk cartridge capacity becomes 2.5TB. We had
developed thin film production nano-imprint line, multi stack cartridge, small sized thin disk auto changer,
and the prototype model controlled by optical disk library system. Especially, the most important result isthat a commercialized standard BD drive without any change is used for the thin disk R/W. Using only
overlapping a special stabilizer to the thin disk, W/R performance for whole data area (r=24mm to 58mm)
of the thin disk is almost same as that of a commercialized BD-R thick disk. The system size is very small,so you can put it beside your PC on your desk. Only using normal USB connection between the SVOD andyour PC, you can use it like an external HDD.
Keywords

SVOD, nano-imprint, thin disk, sheet disk, thin disk auto changer, multi stack cartridge, TBINTRODUCTION
Multi-layer disk and Holographic memory researches are going well for future optical disk. However, thedata capacity is discussing in the range of few 100GB. HDD and computer tape data capacity is alreadyover 1 TB. Now, a favorite archive media is still required for a data center, broadcast, medical, network
companies. Therefore, we had proposed the stacked volumetric optical discs (SVOD 1-5)) with sub tera Byte.
We prepared 100 thin optical disks and a cartridge, and they are put in the cartridge with separate sheet foreach thin disk with pull out tag. Also we developed the special auto disk changer. It pulls out an arbitrary
thin disk from the cartridge with the tag and mounts it to a BD drive with a special stabilizer disk. The alldisks in the cartridge are well controlled by commercialized standard software of optical disk library. Whenthe thin disk data capacity is 25GB, the cartridge capacity becomes 2.5TB. Thus, it is possible to provide afew Tera Byte optical disk system, using a commercialized optical drive and library software without any
special change. This is one quick way to set up Tera Byte optical storage system.
EXPERIMENTAL METHODS & RESULTS
In order to realize a Tera Byte optical disk system quickly, we had developed SVOD with 100 thin disks
made by a nano-imprint technology as shown in Fig.1. To avoid several kinds of contaminations on the thindisk surface, a nano-imprinted fabrication system was prepared. The performance test was done using astandard commercialized BD drive as shown in Fig.2. That is, our main purpose was a quick developmentof Tera Byte optical storage system. However, thin disk could not rotate stably on the normal drive, wedeveloped a special aerodynamic stabilizer as shown in Fig.3. The structure and air dynamic flow during
9000 rpm is shown in Fig.4. It shows a stable rotation. Because there are 8 holes inner area of the stabilizer
and stable air flow can be realized between the thin disk and the stabilizer. When we use no inner holestabilizer, a measurement result of axial acceleration is shown in Fig.5. The thumping vibration of the axial
acceleration can be observed and it is over the specification. However, by using 8 hole stabilizer as shownin Fig.6, the axial acceleration was drastically decreased and it is in the specification.
Thus, we succeeded to obtain stable thin disk rotation tangential and radial tilt margins are measured.

Both results of the thin disk are almost same as those of 1.2mmt commercialized disk. In Fig.7 thetangential tilt margin of the thin disk is shown. Concerning radial tilt margin, it is shown in Fig.8. the wide
margin can be confirmed, And it is also same as that of 1.2mmt standard disk.
Fig.9 shows the Arrhenius plot of lifetime of the thin disk for durability test. The lifetime is estimatedover 100 years. The result is also same as that of 1.2mmt product one. From these performance test result,
there is no difference between thin disk and thick normal 1.2mmt disk. Readout durability test wasperformed. The result is shown in Fig.10. After 1million readout cycle, the jitter increase is very small.
This result is almost same as that of 1.2mmt standard disk. How about a cramping test for the thin film? We
made the cramping test machine and checked it. The result shows the thin disk hole shape change could not
be observed after 1 million cramping test. Therefore, there is only little change of eccentricity of the thindisk.
Fig.11 shows recording power margin of BD type SVOD. In all data area, wide power margin can beobserved. Several evaluated results (Jitter, modulation and asymmetry) of the thin disk are arranged in thetable I. Thus, nano-imprinted thin disk can be used under the condition of blue laser and high NA of 0.85.
In all data area of the thin disk, full high vision TV can be recorded and playback completely.
Next we prepared the cartridge as shown in Fig. 12. 48 thin disks are stocked in the cartridge with anenvelope for each disk. 1 disk data capacity is 25 GB. In this case, the data capacity of the cartridge
becomes 1.2TB. 48 disks are covered with thin envelope. These structures are very important to keep cleansurface of the thin plastic disk. After 10,000 cycle set unset test, there is no change of PI error distribution
in all data area. And cartridge drop off test was confirmed. Thus, this cartridge system is durable.
Using this cartridge, auto thin disk mini changer was fabricated as shown in Fig.13. The changer can beconnected to the PC with USB. In the PC, optical disk library software is installed and user can operate theSVOD mini changer like an external HDD. For example, it is very easy to copy from 1TB HDD to SVOD
mini changer. It is only one drag operation from HDD icon to SVOD icon on the PC screen.
CONCLUSIONSAn auto nano-imprinted thin disk maker was constructed. Using this machine, 0.1mmt thin disk for blue
laser high NA was fabricated and the W/R performance in all data area of 24mm-58.5mm was confirmed assame as that of 1.2mmt commercialized BD disk. To make a 1.2TB optical storage system, the cartridge
included 48 disks was designed and the cartridge durability test was also confirmed. Moreover, thin disk
auto mini changer was demonstrated using the cartridge with 48 disks. Using USB connection between theSVOD library and PC, durable disk set and unset operations were confirmed. Thus, the SVOD is very
durable and long life storage. When 5 SVOD mini libraries are connected each other, a RAID 5 optical disk
system can be operated. When a cartridge changer is prepared, 1 Peta Byte SVOD Rack Unit System canbe realized. In near future, we hope to use the SVOD as a century archive system and that this is useful toreduce IT energy problem.

REFERENCIES1) H. Awano, H. Ido, T. Iida, Y. Watanabe, H. Kishi, A. Inaba, M. Tani, H. Yamanaka, S. Osawa, N. Nagai,
M. Yoshihiro, T. Uchida, M. Yamazaki, N. Ota, T. Yoshida, T. Shimizu, I. Naniwa, Y. Abe, K. Yoshida,and K. Sato : Optical Data Storage Abs. , 2006, WP24
2) T. Yoshida, T. Shimizu, I. Naniwa, Y. Abe, K. Yoshida, K. Sato, H. Awano, H. Ido, T. Iida, Y. Watanabe,H. Kishi, A. Inaba, M. Tani, H. Yamanaka, S. Osawa, M. Yoshihiro, and N. Ota : ISOM Tech.Dig., 2006,Mo-C-02.
3) A. Inaba : JJAP Vol.47, No.7, 2008 pp.5496-5498
4) A. Inaba, H. Ido, H. Kishi, H. Yamanaka, S. Osawa, M. Tani, T. Uchida, Y. Watanabe, S. Arai, M.
Yoshihiro, T. Iida, H. Awano, N. Ota, T. Yoshida, Y. Abe, and K. Yoshida : JJAP Vol.47, No.7, 2008
pp.5812-5813
5) A. Inaba, and H. Awano : The Review of Laser Engineering, June 2009 PP. 461-466

Fig.1 Schematic figure of nano-imprint

Fig.2 Thin film disk is put on the motorof commercialized standard BD drive.

Fig.3 Aerodynamic stabilizer is mounted on the disk.

Fig.4 Aerodynamic stabilizer with inner holes.

Fig.5 Axial acceleration without inner holes.
Dashed line is the specification, and theexperimental result is over the spec..

Fig.6

Axial acceleration with inner holes.
The experimental result is in the spec..
Air flow keeps flat disk rotation.

Fig.7 Tangential tilt margin curves of 92um SVOD
and 1.2mmt product disk. These are overlapped.
Thus, thin disk can be used as a standard disk.

Fig.8

Radial margin curves of thin disk.
These are overlapped. This shows thatthin disk can be used as a standard disk.

Fig.9 Arrhenius plot of thin disk for durability test.
The result is almost same as 1.2mmt disk.

Fig.10 Readout power durability test of thin disk.
This result is almost same as 1.2mmt disk.

Fig.11 Recording power margin of thin
BD type SVOD.

Fig.12 Cartridge of SVOD with 48 disks.

Fig.13 Proto type of SVOD mini auto disk changer
USB connection between SVOD changer and PC
Also optical library software is installed. User canoperate SVOD very easily like an external HDD.