Dynamic information storage or retrieval – Specific detail of information handling portion of system – Radiation beam modification of or by storage medium
Reexamination Certificate
1997-12-19
2001-09-18
Hindl, Nabil (Department: 2651)
Dynamic information storage or retrieval
Specific detail of information handling portion of system
Radiation beam modification of or by storage medium
C369S044230
Reexamination Certificate
active
06292453
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an optical disc recording/reproduction apparatus and method and in particular, to an optical disc recording/reproduction apparatus and method using two groups of lenses enabling to accurately recording and reproducing a data.
2. Description of the Prior Art
The most widely known disc as an optical disc is a CD (Compact Disc). As the CD has a large recording capacity, it is now spreading as a medium for providing a computer program and data, including CD-ROM.
As an optical disc capable of recording or reproducing a data with a higher density than this CD, a DVD (Digital Versatile Disc) has been developed and normalized.
In general, when a disc recording capacity is made to have a high density, it is necessary to make larger a numerical aperture of a pickup lens used for recording or reproducing a data. That is, in order to increase a recording density, it is necessary to reduce the size of an optical spot as much as possible. A size of an optical sport formed on an optical disc is defined as L/2NA, assuming L to be a wavelength and NA to be a numerical aperture of the lens. Consequently, in order to increase a recording density, it is necessary either decrease the wavelength or increase the numerical aperture NA of the lens.
For example, because a DVD has a higher recording density than a CD, reproduction of the DVD requires a lens numerical aperture of about 0.6 in comparison to about 0.43 required for reproduction of the CD.
It is expected that the optical disc can have a further higher density than the DVD. For this, the lens numerical aperture should be a further greater value. However, the maximum numerical aperture which can be realized by a single lens is considered to be 0.6 because of the processing accuracy.
To cope with this, U.S. Pat. No. 5,125,750 discloses a solid immersion lens (SIL) to be used in combination with an objective lens, as a two-lens group, so as to realize a greater numerical aperture.
When this two-lens group is used for realizing a high numerical aperture, there is a problem that as the light coming out of the SIL enters an optical disc with a great angle, if a distance between the two lenses is deviated from a predetermined value, a wave front aberration is caused and it becomes difficult to carry out an accurate data recording or reproduction.
SUMMARY OF THE INVENTION
It is therefore an object of the present invention to enable to carry out an accurate data recording or reproduction when using a lens unit consisting of at least two lenses.
An optical disc recording/reproduction apparatus claimed in claim
1
comprises: first drive means for driving both of the first lens and the second lens in a focusing direction; second drive means for relatively driving the second lens with respect to the first lens in the focusing direction; focus servo means for carrying out focus servo by driving the first drive means so as to drive both of the first lens and the second lens in the focusing direction; and jog mode adjustment means for driving the second drive means after the focus servo is locked, so as to carry out a jog mode adjustment of the position of the second lens with respect to the first lens.
An optical disc recording/reproduction method claimed in claim
14
is characterized by a focus servo step for driving both of the first lens and the second lens in a focusing direction for carrying out a focus servo; and a jog mode adjustment step, after the focus servo is locked, for carrying out a jog mode adjustment of a position of the second lens with respect to the first lens.
In the optical disc recording/reproduction apparatus claimed in claim
1
and the optical disc recording/reproduction method claimed in claim
14
, the focus servo is locked before carrying out the jog mode adjustment of the position of the second lens with respect to the first lens. Consequently, it is possible to accurately record or reproduce a data.
REFERENCES:
patent: 5526336 (1996-06-01), Park et al.
patent: 5689480 (1997-11-01), Kino
patent: 5691971 (1997-11-01), Kim
patent: 5712842 (1998-01-01), Yamamoto et al.
patent: 5764613 (1998-06-01), Yamamoto et al.
patent: 5828635 (1998-10-01), Choi
patent: 5889749 (1999-02-01), Katsums et al.
patent: 6005834 (1999-12-01), Maeda et al.
Ichimura Isao
Maeda Fumisada
Ohsato Kiyoshi
Suzuki Akira
Watanabe Toshio
Hindl Nabil
Kananen Ronald P.
Rader Fishman & Grauer
Sony Corporation
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