Tracking servo method using reflective optical filter for holographic data storage system

Abstract

Holographic data storage system is one of the next-generation data storage systems and is characterized by its high storage density and fast data transfer rate. However, holographic data storage systems are very sensitive to disturbances that affect the position of the media. Therefore, tracking servo control is needed to ensure a good performance of the system even if disturbances occur, such as eccentricity of the disk and external shock. In our previous researches on tracking servo methods, we used additional beams or recorded servo track images with data pages to record additional gratings with data pages. Therefore, the recording density may be reduced and the system may be complicated. In addition, the performance of the system may be compromised by cross-talk noise caused between the reference beams and additional beams. In this paper, we propose a tracking servo method using the residual beam, which is reflected by the reflective optical filter. This method does not require recording supplementary gratings or use additional beams, and only needs to record data pages. The residual beam is retrieved with desired retrieved beam by the reference beam and wasted during the retrieving process. We first constructed a holographic data storage system and designed a reflective optical filter to detect tracking error signals. After detecting the tracking error signals, a tracking servo controller using a lead-lag compensator was incorporated to reduce the tracking error signals. The performance of the designed controller was verified by simulated and experimental results. Finally, the performance of the tracking servo method was investigated by comparing the retrieved data images.

Technique for positioning hologram for balancing large data capacity with fast readout

“…By developing an optical architecture for generating angle error signals 10,11) and adaptive final-state control (AFSC), 12) we have successfully demonstrated the servo control of the reference beam angle with a settling time of less than 300 µs and an accuracy of a relative angle of less than ±3.0 mdeg between the recording and the readout state. [10][11][12] On the other hand, although several previous studies of the positioning of the holographic disc in a HDSS using angularly multiplexed recording have been reported, 13,14) an effective technique that satisfies both the highly precise and high-speed positioning of the holographic disc has not yet been proposed. One of the difficulties is the higher moment of inertia of the holographic disc than of the galvano mirror.…”

Disturbances Analysis Considering an Effective Servo System for Holographic Disc Drive

“…Various error measurement and compensation methods tailored to HDS characteristics have been proposed. [7][8][9][10][11][12][13][14][15][16][17] However, previous studies have not considered stop-go rotation of the spindle, which should be applicable to the rotation mechanism of the HDS system. In this paper, the adaptive servo method is proposed based on analysis results regarding the disturbance characteristics of stop-go rotation.…”