Dynamic information storage or retrieval – Control of storage or retrieval operation by a control... – Mechanism control by the control signal
Patent
1988-04-22
1989-12-19
Psitos, Aristotelis M.
Dynamic information storage or retrieval
Control of storage or retrieval operation by a control...
Mechanism control by the control signal
369 45, 369122, 250201, G11B 709
Patent
active
048887579
DESCRIPTION:
BRIEF SUMMARY
FIELD OF TECHNOLOGY
The present invention relates to a focused-spot-position detection device of an optical information recording and reproducing device in which an information is recorded in and reproduced from an information recording medium and erased by means of light beam and, particularly, to a focusing error and tracking error detection device.
BACKGROUND ART
FIGS. 10 and 11 show an example of a focusing error detection device for an optical head such as shown in Japanese Patent Application Laid-open No. 93223/1977 or J. M. Broat and G. Bouwhuis, "Position Sensing In Video Disc Read Out", Applied Optics, vol. 17, No. 13, pp. 2013-2021, (1978).
In FIG. 10, 1 depicts a light source such as a He Ne laser and 2 is an auxiliary lens for expanding a diameter of light beam emitted by the light source 1. 3 depicts an information recording medium such as an optical disk, 4 an information recording plane of the information recording medium 3 and 5 an information track, the information recording medium 3 being rotatable around a rotary shaft 6. 7 depicts a half mirror for separating irradiation light to the information recording medium 3 from reflection light from the information recording medium 3, 8 a mirror for bending an optical path of the irradiation light to the information recording medium 3, and 9 an objective lens for focusing the irradiation light from the light source 1 onto the information track 5. 10 depicts a focusing error detection sensor which is composed of a plurality of optical detecting elements. 11 depicts an auxiliary lens for projecting an image formed on an exit pupil of the objective lens 9 by a reflection light from the information recording medium 3 onto the optical detecting elements in the focusing error detecting sensor 10. In FIG. 10, an image of a point a on the exit pulpil of the objective lens 9 is formed on the focusing error detecting sensor 10 as a point a' by the auxiliary lens 11.
In FIG. 11, 12 and 13 depict the optical detecting elements in the focusing error detecting sensor, 14 a subtractor for providing a difference between output signals from the optical detecting elements 12 and 13, 15 an adder for adding the output signals of the detecting elements 12 and 13, 16 a phase shifter for shifting a phase of an output signal of the adder 15 by 90.degree., 17 a multiplier for multiplying an output of the phase shifter 16 with the output signal of the subtractor 14, and 18 a low pass filter for passing a low frequency component of the output signal of the multiplier.
The operational principle of this focusing error detecting device is based on the fact that, in reading an information on the information recording plane 4 which acts as a diffraction grating, there is produced a phase difference between 0 order light directly reflected by the information recording medium and the first order diffraction light reflected and diffracted by information pits on an information track thereof and the phase difference corresponds to a focusing error. The phase difference between the 0 order light and the first order diffraction light can be measured by analysing interference fringes in an interference region of the 0 order light and the first order diffraction light in a plane remote enough from the information recording medium, that is, a plane in which the 0 order light and the first order diffraction light can be observed with an enough distance therebetween (the latter plane will be referred to hereinafter as a plane disposed in a "far field" of the information recording medium) and, in the conventional device, a focusing error signal is produced by electrically processing outputs of a plurality of optical detecting elements arranged in the remote region.
A coordinate system necessary to describe an operation of this conventional device will be defined firstly. As shown in FIG. 10, .xi. and .eta. axes are set on the information recording plane 4 of the information recording medium 3 in parallel with a center line of the information track 5 and orthogonally of the center line,
REFERENCES:
patent: 4768179 (1988-08-01), Gottfried
patent: 4805162 (1989-02-01), Stahl et al.
patent: 4807214 (1989-02-01), Getreuev
Mitsubishi Denki & Kabushiki Kaisha
Psitos Aristotelis M.
LandOfFree
Focused-spot-position detection device for optical information r does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Focused-spot-position detection device for optical information r, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Focused-spot-position detection device for optical information r will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-1907595