| 摘要 |
An optical data storage system includes a laser which is focused on an optical disk by an objective lens. A tracking actuator and a focus actuator move the objective lens about a tracking axis and focus axis respectively. The tracking and focus actuators respond to signals provided by a focus and tracking detector. The focus and tracking detector is formed by four photodetectors which are electrically isolated from one another. The third and fourth photodetectors are disposed about the outer peripheries of the first and second photodetectors, respectively, about an axis. Each photodetector emits an electrical signal representative of the radiation detected thereon.
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