Dynamic magnetic information storage or retrieval – Automatic control of a recorder mechanism – Controlling the head
Reexamination Certificate
1998-03-19
2001-12-04
Hindi, Nabil (Department: 2651)
Dynamic magnetic information storage or retrieval
Automatic control of a recorder mechanism
Controlling the head
C369S112010, C369S112070
Reexamination Certificate
active
06327110
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an optical system and a position detector for positioning a head by using light when recording and/or reproducing information in and/or from an information storage medium such as a high-density floppy disk or optical disk, and a magnetic recorder using the optical system and position detector or an aperture-provided lens for realizing the optical system, position detector, and magnetic recorder.
2. Related Art of the Invention
As recording information in a magnetic disk such as a floppy disk at higher density, the interval between tracks each of which is a string of pieces of information decreases. Therefore, because positioning of a magnetic head in the direction perpendicular, to tracks is difficult at a mechanical accuracy, an art for performing positioning by light has been developed.
For example, when the interval between guide grooves constituted with a pit string for tracking a high-density floppy disk is approx. 20 &mgr;m, it is possible to obtain a track error signal by using an optical system having a light-source wavelength of 780 nm and a numerical aperture of NA=approx. 0.04 at the disk side.
A conventional position detector in the track direction of a high-density floppy disk is described below by referring to FIG.
23
.
As shown in
FIG. 23
, a light beam emitted from a semiconductor laser
101
serving as a light source produces a zero-order light ray and positive and negative first-order diffracted-light rays by a diffraction device
102
though not illustrated. In this case, the zero-order light ray is referred to as a main beam and the positive and negative first-order diffracted-light rays are referred to as sub-beams. The main beam and two sub-beams pass through a half mirror
103
and are condensed by a lens
104
.
Openings of the main beam and sub-beams condensed by the lens
104
are restricted by an aperture
109
so that the openings have a predetermined numerical aperture NA and the main beam and sub-beams are condensed to a floppy disk of an information storage medium (-hereafter referred to as disk)
107
.
Concentric information data strings are recorded in the disk
107
and they are referred to as tracks. Moreover, guide grooves are formed between tracks at proper intervals on the disk
107
so that positioning can be made by light rays. A beam string constituted with the main beam and two sub-beams is arranged so as to form a predetermined angle to the guide grooves on the disk
107
.
Light rays reflected from the disk
107
pass through the aperture
109
and lens
104
again and they are reflected by the half mirror
103
to enter a photodetector
108
.
The photodetector
108
is constituted with a plurality of detection regions, which receives three beams of the main beam and two sub-beams separately from each other and outputs a signal corresponding to the received luminous energy. These three beams irradiate respectively relatively different positions in the direction perpendicular to the guide grooves on the disk
107
on the basis of the guide grooves. Therefore, modulation factors of signals obtained from three detection regions are different from each other. By inputting these signals to an arithmetic circuit
300
and computing them, it is possible to detect the relative positional relations between guide grooves and beam irradiating positions. By using the relations, a magnetic head
201
is positioned to a track on the disk
107
to record and reproduce information into and from a desired track. Description of the arithmetic method by the arithmetic circuit
300
is omitted because the method is described in the official gazette of Japanese Patent Application Laid-open No. 9-161424 in detail.
Moreover, though not illustrated, there is another conventional position detector without a half mirror, having a structure in which condenser lenses are set to the optical path of the light emitted from a semiconductor laser and the optical path of the light reflected on a disk one each in order to separate the both optical paths from each other and light is diagonally applied to the disk
107
.
However, this conventional type of the position detector has a problem that, when a disk tilts from a light beam, some of a light beam reflected on the surface of a disk is interrupted on a returning path and thereby, a position detection signal cannot be stably detected.
SUMMARY OF THE INVENTION
It is an object of the present invention to provide a position detector capable of stably detecting a position compared to a conventional one and a magnetic recorder, and an optical system and an aperture-provided lens to be applied to the detector and the recorder.
To achieve the above object, the invention of claim
1
is an optical system through which an advancing optical path for a light beam to enter a reflector and a returning path of the light beam reflected and/or diffracted from the reflector pass, wherein when
when assuming the thickness of an optical path through which the advancing optical path passes without being interrupted as a first thickness and the thickness of an optical path through which the returning optical path passes without being interrupted as a second thickness, the second thickness is larger than the first thickness.
Moreover, the invention of claim
6
is a position detector comprising:
a light source for emitting a light beam;
condensing means for converging the light beam emitted from the light source on a reflector;
beam branching means for branching the light beam reflected and/or diffracted by the reflector;
a photodetector for receiving the light beam branched by the beam branching means and outputting a signal corresponding to the luminous energy of the light beam; and
an arithmetic circuit for receiving the signal output from the photodetector and outputting a position detection signal; wherein
when assuming the thickness of an optical path through which an advancing path for a light beam emitted from the light source to be bound for the reflector can pass without being interrupted as a first thickness and the thickness of an optical path through which a returning path for the light beam to be bound for the photodetector through the beam branching means from the reflector can pass without being interrupted as a second thickness, an optical system having the second thickness larger than the first thickness is constituted.
Furthermore, the invention of claim
7
is a magnetic recorder comprising:
a light source for emitting a light beam;
condensing means for converging the light beam emitted from the light source on an information storage medium;
beam branching means for branching the light beam reflected and/or diffracted by the information storage medium;
a photodetector for receiving the light beam branched by the beam branching means and outputting a signal corresponding to the luminous energy of the light beam;
an arithmetic circuit for receiving the signal output from the photodetector and outputting a position detection signal;
a magnetic head for recording and/or reproducing information in and/or from the information storage medium; and
transfer means for positioning the magnetic head by receiving the position detection signal; wherein
when assuming the thickness of an optical path through which an advancing optical path for the light beam emitted from the light source to be bound for the information storage medium can pass without being interrupted as a first thickness and the thickness of an optical path through which a returning path for the light beam to be bound for the photodetector through the beam branching means from the information storage medium can pass without being interrupted as a second thickness, an optical system having the second thickness larger than the first thickness is constituted.
Furthermore, the invention of claim
9
is an aperture-provided lens comprising an aperture having a first opening and a second opening correspondingly to the body of a lens, wherein at least one of the both openings is p
Kadowaki Shin-ichi
Sano Kousei
Hindi Nabil
Matsushita Electric - Industrial Co., Ltd.
Ratner & Prestia
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