Optical pickup for optical disk and light source for optical...

Details Optical pickup for optical disk and light source for optical... Optical pickup for optical disk and light source for optical...

1998-06-10

2001-04-03

Hindi, Nabil (Department: 2651)

Dynamic information storage or retrieval

Specific detail of information handling portion of system

Radiation beam modification of or by storage medium

C369S112040, C369S044240

Reexamination Certificate

active

06212154

ABSTRACT:

BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an optical pickup capable of recording information on or reproducing information from an optical recording medium, and more particularly, to an optical pickup adopting a light-emitting diode (LED) capable of forming a light spot of an appropriate size for a high-density recording/reproduction.
2. Description of the Related Art
In general, in an optical recording/reproduction field of technology, an optical disk such as a laser disk (LD), a compact disk (CD) or a digital versatile disk (DVD) has been focused on as an optical recording medium capable of recording a large amount of information. In particular, the DVD has been highlighted due to its large scale information processing capability. In order to increase the recording density of the DVD, it is necessary to minimize the size of the light spot formed on the recording surface of the DVD.
Referring to
FIG. 1
, a conventional optical pickup includes a light source
11
for generating/emitting a laser beam, a beam splitter
13
for converting the traveling path of the incident light, an objective lens
14
for condensing the light emitted from the light source
11
via the beam splitter
13
, and a photodetector
16
for receiving the light incident via the beam splitter
13
after being reflected from an optical disk
1
. The light source
11
is a semiconductor laser for generating and emitting the laser beam. The photodetector
16
receives the light reflected from the optical disk
1
and performs a photoelectric conversion to detect a radio frequency (RF) signal, a tracking error signal and a focus error signal.
A collimating lens
12
is provided between the light source
11
and the beam splitter
13
, which collimates the divergent light emitted from the light source
11
. Also, a light reception lens
15
is arranged between the beam splitter
13
and the photodetector
16
, which causes astigmatism so that a focus error signal can be detected.
As described above, when forming a light spot on the optical disk
1
using an optical pickup having the above structure, the size of the light spot is determined by the following equation (1).
size of light spot≅
λ
NA
where &lgr; represents the wavelength of the light source
11
of the optical pickup, and NA represents the numerical aperture of the objective lens
14
of the optical pickup.
Thus, if the objective lens
14
of the optical pickup has a predetermined numerical aperture, a shorter wavelength of the light emitted from the light source
11
will form a smaller light spot. On the other hand, since the light source
11
is a semiconductor laser, it is difficult for the wavelength of the light to be approximately 635 nm. Thus, if the numerical aperture of the objective lens is 0.6, the size of the light spot formed on the optical disk is approximately 1.08 &mgr;m based on the equation (1). Thus, it is difficult to record optical information of 5 gigabytes or more on an optical disk having a diameter of 130 mm.
SUMMARY OF THE INVENTION
To solve the above problems, it is an object of the present invention to provide an optical pickup capable of recording/reproducing a large amount of information by adopting a light-emitting diode (LED), instead of a semiconductor laser.
Additional objects and advantages of the invention will be set forth in part in the description which follows and, in part, will be obvious from the description, or may be learned by practice of the invention.
To achieve the above and other objects of the present invention, there is provided an optical pickup including a light-emitting diode (LED) to generate and emit light; a condensing unit to condense the light emitted from the LED; an optical filter to selectively transmit a predetermined wavelength of the light emitted from the LED; a spatial filter having a pin-hole, to limit the transmission range of the light condensed by the condensing unit; and a collimating lens to condense the divergent light passed through the spatial filter.
Preferably, the LED generates light having a wavelength of approximately 600 nm or less.


REFERENCES:
patent: 2238735 (1941-04-01), Hullegard
patent: 3295142 (1966-12-01), Slaven
patent: 3716286 (1973-02-01), St John et al.
patent: 3736046 (1973-05-01), Zook
patent: 3980818 (1976-09-01), Browning
patent: 4115809 (1978-09-01), Ueno
patent: 5400314 (1995-03-01), Lee
patent: 5625613 (1997-04-01), Kato et al.
patent: WO 96/27143 (1996-09-01), None

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