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— Presentation at ISOM 2015 —
November 12, 2015
Photo 1 Presentation scene
ISOM 2015 (International Symposium on Optical Memory 2015) was held in Toyama International Conference Center, Toyama prefecture from 4th to 7th in October. ISOM is the largest international conference on optical memory. In ISOM 2015 both oral and poster sessions are combined for 72 reports, discussed Hologram, Nano-Photonic Material and LD/LED or its applications. At this conference, from Hitachi R&D Group's Center for Technology Innovation - Information and Telecommunications made 6 reports and Center for Technology Innovation - Electronics made 1 report. Among these reports, I presented "High-Speed Reference Beam Angle Control Technique for Holographic Memory Drive" (Photo 1).
We have been developing a holographic memory known as next generation optical memory. At this conference, especially, I presented about, a key technology that realizes high-speed transfer rate for reproduction, a high-speed control technique for reference beam angle.
Fig. 1 Issue for reproduction of hologram
In reproduction for holographic memory, there is an issue that the best reference beam angle during reproducing varies due to a distortion of the medium derived from temperature variation, beam irradiation, and moisture absorption. Thus, a reference beam angle control technique is required to locate the reference beam to the best angle (Fig. 1). Thus we developed a new optical system which generates an angle error signal to detect the best reference beam angle using an optical axis. And, to realize high-speed control technique using the new optical system, we developed a new control technique AFSC (Adaptive Final-State Control) which adds 2nd control input, at a timing of angle error signal detection, to 1st input derived from conventional FSC (Final-State Control) and realize high-speed control to the best reference beam angle (Fig. 2). In an actual experimental system applied AFSC, we could realize a page seek within a target time (300 µs). In multiple page seeks, we could realize positioning to the best angles which maximizes diffracted beam intensities (Fig. 3). By applying AFSC to holographic data storage system, realization of a giga bit/s class transfer rate is highly expected.
At this conference, Center for Technology Innovation - Information and Telecommunications could show some technologies developed for holographic memory and appeal our advanced technology level.
This presentation is a part of the result of the development technology in the industry-university co-operation collaborative investigation with Tokai University.
(By YAMADA Kenichiro)