Dynamic information storage or retrieval – With servo positioning of transducer assembly over track... – Optical servo system
Patent
1991-08-26
1992-07-21
Envall, Jr., Roy N.
Dynamic information storage or retrieval
With servo positioning of transducer assembly over track...
Optical servo system
369 4425, 369 4432, 369 4441, 369 54, 318608, 318640, 2502015, G11B 709
Patent
active
051329484
ABSTRACT:
A phase comparing apparatus which outputs a signal of an amplitude corresponding to phase difference between a first and second signals, includes a difference signal operating device for outputting a difference signal generated according to the difference in voltage between the first and second signals, first and second maximum value detecting device for respectively generating first and second maximum value detecting signals when maximum values of the first and second signals are respectively detected, a timing comparing device for outputting a first timing signal in response to one of the first and second maximum value detecting signals which is generated earlier than the other thereof and outputting a second timing signal in response to the other thereof, first and second sample-and-hold devices for respectively sampling and holding the difference signal outputted from the difference signal operating means, in response to the first and second timing signals, respectively, and a differential device for outputting a difference signal generated according to difference in voltage between signals outputted from the first and second sample-and-hold devices. A focus error detecting apparatus includes a light beam emitting device, an objective lens for condensing light beams emitted by the light beam emitting device on a recording medium, and a light receiving device, having two sections outputting the first and second signals, for detecting light beams which has been reflected by the recording medium and converting the light beams into signals, and the phase comparing apparatus.
REFERENCES:
patent: 4589103 (1986-05-01), Tajima
patent: 4710909 (1987-12-01), Tsuyoshi et al.
patent: 4998235 (1991-03-01), Ishibashi et al.
Edun Muhammad N.
Envall Jr. Roy N.
Matsushita Electric - Industrial Co., Ltd.
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