双光头多层数据存储系统同步聚焦误差检测

Synchronizing Focus Error Detection of Dual-Pickup in Multi-Layer Data Storage System

为实现共焦双光头多层数据存储系统,需要对双光头同步聚焦误差进行检测,以确定聚焦伺服跟踪精度,验证系统的可行性。首先利用几何光学的ABCD变换矩阵计算双光头输出能量与光头间距离的关系,确定其线性工作范围;其次通过输入不同频率的正弦信号驱动音圈电机,获得静止状态、下光头运动状态以及双光头同步运动状态下,四象限探测器的输出信号;最后对输出信号进行频域分析,可计算得到由于双光头参量失配而导致的同步聚焦误差在不同频率下的幅值。实验结果表明,在20 Hz、峰-峰值0.5 V正弦信号作用下,同步聚焦误差幅值在1μm以下,可以满足共焦双光头多层数据存储系统的聚焦伺服跟踪要求。

To implement dual-pickup-head multilayer data storage system, it is necessary to measure the synchronizing focus error of the two pickup heads to validate the feasibility of the focus servo method. By using the ABCD transforming matrix method of the geometric optics, we calculate the relationship between the output energy and the space interval of the two pickup heads. After confirming the detection system working in linear area, the coil motors of the two pickup heads were driven by sine signal with different frequency and record the output signals of the photo-detector under different movement states respectively, such as rest, single pickup head movement and dual-pickup-head synchronizing movement. The synchronizing focus error, which is caused by the characteristic parameter mismatch of the two pickup heads, could be obtained through frequency-domain analysis of these output signals. The experimental result shows that the amplitude of synchronizing focus error under 20 Hz is less than 1 μm, which could satisfy the focus servo requirement of the multilayer data storage system well.