Dynamic information storage or retrieval – With servo positioning of transducer assembly over track... – Optical servo system
Patent
1989-02-17
1991-07-16
Richardson, Robert L.
Dynamic information storage or retrieval
With servo positioning of transducer assembly over track...
Optical servo system
369 4441, 369112, G11B 700
Patent
active
050330403
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
The present invention relates to an optical information recording/reproducing apparatus for irradiating a reproducing beam and a recording beam onto an information recording medium, and more particularly to an optical information recording/reproducing apparatus improving the tracking performance.
BACKGROUND OF THE INVENTION
FIG. 10 is a structural view of the conventional optical information recording/reproducing apparatus described on Pages 58 through 62--"LD Array Head For DRAW"--of "Micro-Optics News"(Vol. 3, No. 1, edited on Feb. 4, 1985) by Ito and Ohta.
Referring to FIG. 10, reference numeral 1 designates a semiconductor laser array emitting two light beams a recording beam L1 of high intensity of light and reproducing beam L2 of low intensity of light. Reference numeral 2 designates a collimator lens for collimating the parallel light beams L1 and L2 emitted from the semiconductor laser array 1, and 3 designates a beam shaping prism for correcting the distribution of optical strength of the respective collimated beams L1 and L2.
Reference numeral 4 designates a polarizing beam splitter, which is adapted to transmit therethrough the beams L1 and L2 to a beam shaping prism, toward an information recording medium (to be discussed below) and to reflect toward an error detecting system (to be discussed below) a recording reflected beam L1' and a reproducing reflected beam L2' from the information recording medium.
Reference numeral 5 designates a reflecting mirror, and 6 designates a 1/4 wavelength plate, which are disposed on an optical path at the transmission side of the polarizing beam splitter 4.
Reference numeral 7 designates an objective lens for focusing onto the beams L1 and L2 on the information recording medium the beams L1 and L2, said beams having already passed the reflecting mirror 5 and 1/4 wavelength plate 6 respectively. 8 designates an information recording medium comprising an optical disc rotatable around a rotary shaft 8a, and 9 designates an information track 9 formed concentrically or spirally in the information recording medium 8.
Reference numeral 10 designates a convex lens disposed on an optical path at the reflection side of the polarizing beam splitter 4, and 11 designates a spatial filter disposed at the focal point of convex lens 10, which cuts off the recording reflected beam L1' reflected from the information recording medium 8 and allows only the reproducing reflected beam L2' to transmit through the lens 11.
Reference numeral 12 designates a beam splitter for dividing the reproducing reflected beam L2' which has already passed the spatial filter 11. The beam is directed toward a tracking error detection system and toward a focusing error detection system (both to be discussed below). Reference numeral 13 designates a two-divided photodetector for receiving the reproducing reflected beam L2' which has passed the beam splitter 12. Reference numeral 14 designates a convex lens, 15 designates a knife edge, and 16 designates a two-divided photodetector for receiving the reproducing reflected beam L2' through the knife edge 15. All of the components 14, 15 and 16 are disposed on the optical path at the reflection side of the beam splitter 12.
Reference numeral 17 designates a differential amplifier which takes in a difference between the two signals output from the two-divided photodetector 13. Reference numeral 18 designates a tracking actuator for driving the objective lens 7 in the traversing direction (in the direction of the arrow T) with respect to the information track 9 on the basis of an output signal of the differential amplifier 17. Reference numeral 19 designates a differential amplifier which takes in a difference between the two signals output from the two-divided photodetector 16, and 20 designates a focusing actuator for driving the objective lens 7 in the vertical direction (in the direction of the arrow F) with respect to the surface of the information recording medium 8 on the basis of the output signal of the differential amplif
REFERENCES:
patent: 4498159 (1985-02-01), Daimon
patent: 4945529 (1990-07-01), Ono et al.
Mitsubishi Denki & Kabushiki Kaisha
Richardson Robert L.
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