Optical pick-up apparatus

Details Optical pick-up apparatus Optical pick-up apparatus

1999-01-19

2002-06-18

Tran, Thang V. (Department: 2653)

Dynamic information storage or retrieval

Specific detail of information handling portion of system

Radiation beam modification of or by storage medium

C369S112280, C369S094000, C369S044230

Reexamination Certificate

active

06407974

ABSTRACT:

BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to an optical pick-up apparatus adapted to access different disks.
2. Description of the Related Art
An optical disc such as CD (Compact disc) and CD-R (CD-Recordable) is used to store audio, video and digital text information, as a recording medium. In recent years, optical discs have been developed to record larger amounts of information. To this end, there has become recently appeared a DVD (Digital Versatile Disc) capable of recording an amount of information relative to the CD and CD-R. A DVD is not only higher than the CD and CD-R in track density, but also shorter than those in a distance extending from the disc surface to the recording layer. The distance between the disc surface and the recording layer in a DVD is 0.6 mm while that in the CD and CD-R is 1.2 mm. Also, the recording layer of the DVD has characteristics different from that of the CD and CD-R. Due to such the structural differences with CD and CD-R, the DVD demands an optical pick-up apparatus different from the optical pick-up apparatus for the CD and CD-R. There are optical pick-up apparatuses for the DVD and for the CD and CD-R.
Optical pick-up apparatus are used to access the CD and CD-R as well as the DVD. Such a combined optical pick-up apparatus is shown in FIG.
1
. The combined optical pick-up apparatus of
FIG. 1
includes an objective lens
18
for allowing light beams B
1
and B
2
from a laser diode
12
and a hologram module
16
to be irradiated on the recording layer
10
A or
10
B of a disc
10
, and a photo detector
14
for detecting light reflected by the information recording layer
10
A or
10
B of the disc
10
. First information recording layer
10
A represents the recording layer of a DVD, while second information recording layer
10
B represents the recording layer of a CD or CD-R. The laser diode
12
generates a first light beam B
1
having a wavelength of 650 nm adaptable to access the DVD. The photo detector
14
converts light reflected by the recording layer
10
B of the DVD into an electrical signal. The hologram module
16
includes a laser diode (not shown) and a photo detector (not shown). The laser diode of hologram module
16
generates a second light beam B
2
having a wavelength of 780 nm adaptable to access the CD and CD-R. The photo detector of the hologram module
16
detects the light reflected by the recording layer
10
A of the CD or CD-R. A first beam splitter
20
, a collimator
22
and a reflective mirror
24
are installed between the laser diode
12
, the hologram module
16
and the objective lens
18
. The first beam splitter
20
allows the first light beam B
1
from the laser diode
12
and the second light beam B
2
from the hologram module
16
to proceed in an identified path. To this end, the first beam splitter
20
not only reflects perpendicularly the first light beam B
1
from the laser diode
12
, but also passes the second light beam B
2
from the hologram module
16
. The collimator
22
forces the first and second light beams B
1
and B
2
each divergently transmitted from the first beam splitter
20
to proceed in parallel. The reflective mirror
24
reflects perpendicularly the first and second light beams B
1
and B
2
from the collimator
22
toward the objective lens
18
. The objective lens
18
enables the first light beam B
1
from the reflective mirror
24
to be irradiated on the first recording layer
10
A of the disc
10
in the shape of a spot when the first light beam B
1
is applied. Then, the DVD is normally accessed. If the second light beam B
2
is input, the objective lens
18
irradiates the second light beam B
2
from the reflective mirror
24
on the second recording layer
10
B of the disc
10
such that the CD or CD-R is normally accessed. A second beam splitter
26
allows the light beam reflected by the disc
10
to be separately transmitted to the photo detector of the hologram module
16
and the photo detector
14
, respectively. To this end, the second beam splitter
26
causes a part of the light beam from the collimator
22
to be passed toward the photo detector
14
and reflects perpendicularly the rest of the light beam from the collimator
22
toward the first beam splitter
20
. The sense lens
28
converges the light beam to be proceeded from the second beam splitter
26
to the photo detector
14
.
As described the above, the optical pick-up apparatus of
FIG. 1
employs several optical elements for combining the optical systems for the CD/CD-R and DVD. In the optical pick-up apparatus, an aberration in the entire light path is great because the optical elements each generates an aberration. Also, the total aberration produced by the optical elements is greatest due to the combined manufacturing tolerance for each element. Consequently, the combined optical pick-up apparatus does not access accurately all the DVD, CD and CD-R.
SUMMARY OF THE INVENTION
Accordingly, it is an object of the present invention to provide an optical pick-up apparatus capable of accessing different discs with reduced aberration.
It is another object of the present invention to provide an optical pick-up apparatus capable of accessing different discs with a simplified configuration of elements.
In order to obtain the objects of the invention, according to one aspect of the present invention, an optical pick-up apparatus comprises: first light source for generating first light beam having first wavelength; second light source for generating second light beam having second wavelength; an objective lens for converging the first and second light beams on the recording layer of a recording medium in the shape of a spot; and a dichroic optical element for forcing the first and second light beams from the first and second light sources to proceed toward the objective lens along an identified path.
Further, according to other aspect of the present invention, an optical pick-up apparatus comprises: first light source for generating first light beam having first wavelength; second light source for generating second light beam having second wavelength; an objective lens for converging the first and second light beams on the recording layer of a recording medium in the shape of a spot; first and second photo detectors for detecting the first and second light beams reflected by the recording layer of the recording medium, respectively; and a dichroic optical element for forcing the first and second light beams from the first and second light sources to proceed toward the objective lens along an identified path and for distributing the light beam from the objective lens to the first and second photo detectors.


REFERENCES:
patent: 5912868 (1999-06-01), Hayashi et al.
patent: 5933401 (1999-08-01), Lee et al.
patent: 5974020 (1999-10-01), Ju et al.
patent: 5999509 (1999-12-01), Sugiura et al.
patent: 6081498 (2000-06-01), Yoo et al.
patent: 6084845 (2000-07-01), Mizuno

Affiliated with

Also associated with

Rating

Optical pick-up apparatus does not yet have a rating. At this time, there are no reviews or comments for this patent.

If you have personal experience with Optical pick-up apparatus, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Optical pick-up apparatus will most certainly appreciate the feedback.

Rate now

Comments { 0 }

Profile ID: LFUS-PAI-O-2931269