Optical pick-up apparatus

Details Optical pick-up apparatus Optical pick-up apparatus

1998-12-21

2002-04-23

Hudspeth, David (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

06377536

ABSTRACT:

BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to an optical pick-up apparatus adapted to access different types of disks.
2. Description of the Related Art
An optical disc such as CD(Compact disc) and CD-R(CD-Recordable) is used to write audio, video and digital text information and so on, as a recording medium. The optical disc are used to record large amounts of information. To this end, there has recently appeared a DVD(Digital Versatile Disc) capable of recording amounts of information comparable to the CD and CD-R. A DVD is not only higher than the CD and CD-R in track density, but also the distance extending from the disc surface to the recording layer is less than previous disks. For example, the distance between the disc surface and the recording layer in a DVD is 0.6 mm while that in a CD and CD-R is 1.2 mm. Also, the recording layer of a DVD has characteristics different from that of the CD and CD-R. Due to the structural differences between a DVD and a CD and CD-R, the DVD demands an optical pick-up apparatus different from the optical pick-up apparatus for a CD and CD-R. The optical pick-up apparatus for a DVD cannot access a CD and CD-R because of the aberration of the light beam. Aberration of the light beam is generated between the surface and recording layer of a CD and CD-R due to the larger distance between the surface and recording layer than the distance in a DVD. Also, the aberration of the light beam appears on the optical pickup apparatus for a CD and CD-R as the difference between the wave lengths of the light beams.
FIG. 1
shows an optical pick-up apparatus of an infinite optical system having a flux diameter controller to remove such aberrations when a CD and CD-R are accessed. The optical pick-up apparatus includes a first hologram module
12
, a beam splitter
14
, a collimator
16
and a reflective mirror
18
aligned in a horizontal direction. Also, the optical pick-up apparatus of
FIG. 1
also includes a second hologram module
20
located at the beam splitter
14
, a flux diameter controller
22
and an objective lens arranged between the reflective mirror
18
and a disc
10
A or
10
B. The first and second hologram modules
12
and
20
each have a light source and a photo detector. The light source of first hologram module
12
generates a light beam having a wavelength of 650 nm to be irradiated on the DVD
10
A, while the light source of the second hologram module
20
irradiates another light beam having a wavelength of 780 nm on the CD or CD-R
10
B. The beam splitter
14
transmits the light beams from the first and second hologram modules
12
and
20
to the collimator
16
, and allows the light beams from the collimator
16
to be distributed to both the first and second hologram modules
12
and
20
. The collimator
16
causes the light beams from the beam splitter
14
to proceed toward the reflective mirror
18
in parallel. The flux diameter controller
22
controls the flux diameter of a light beam transmitted between the reflective mirror
18
and the objective lens
24
, according to the disc
10
A or
10
B. If DVD
10
A is accessed, i.e., when the light beam has the wavelength of 650 nm, the flux diameter controller
22
allows the light beam from the reflective mirror
18
to go directly toward the objective lens
24
. On the other hand when accessing CD/CD-R
10
B, the flux diameter controller
22
decreases the flux diameter of the light beam from the reflective mirror
18
and transmits the light beam having a decreased flux diameter to the objective lens
24
. The objective lens
24
converges the light beam from the flux diameter controller
22
onto the recording layer of the disc
10
A or
10
B, i.e., on the recording layer of the DVD
10
A or on the recording layer of the CD or CD-R
10
B, in the shape of a spot. Light beams having a wavelength of 650 nm are irradiated on the recording layer of DVD
10
A in the shape of a spot, while light beams having a wavelength of 780 nm are irradiated on the recording layer of the CD or CD-R
10
B in the shape of a spot.
In the optical pick-up apparatus of
FIG. 1
, since the flux diameter controller
22
is located between the collimator
18
and the objective lens
24
, the configuration is complex and the manufacturing costs are great. Also, a light beam can only be traced to a track on the disc
10
A or
10
B if the flux diameter controller
22
an objective lens
24
are driven by actuator
26
. The heavy weight load of the actuator limits the speed at which the disc may be access to a critical speed. Furthermore, in the optical pick-up apparatus of
FIG. 1
, each of the first and second hologram modules
12
and
20
must be accurately installed at the demanded location such that the center axis of the light beam proceeding from the first hologram module
12
is united with the center axis of the light beam proceeding from the second hologram module
20
. However, the center axis of the light beam proceeding from the first hologram module
12
can not be united with the center axis of the light beam proceeding from the second hologram module
20
due to a locating error and an angle error caused in the combination of the optical pick-up apparatus.
SUMMARY OF THE INVENTION
Accordingly, it is an object of the present invention to provide an optical pick-up apparatus which can adaptively compensate for the aberration of the light beam according to the type of disk.
It is another object of the present invention to provide an optical pick-up apparatus which has the facility to unite center axes of light beams from two light sources.
In order to obtain said objects of the invention, according to one aspect of the present invention, an optical pick-up apparatus comprises: a first light source for generating a first light beam having a first wavelength to be irradiated on a disk; a second light source for generating a second light beam having a second wavelength to be irradiated on the disk; and a light path for irradiating the first light beam from the first light source on the disk in the shape of a spot by a finite optical system and the second light beam from the second light source on the disk in the shape of a spot by an infinite optical system.
Further, according to other aspect of the present invention, an optical pick-up apparatus comprises: a first light source for generating a first light beam having a first wavelength to be irradiated on a disk; a second light source for generating a second light beam having a second wavelength to be irradiated on the disk; an objective lens for irradiating the first and second light beams from the first and second light sources on the disk in a shape of spot; a beam splitter for guiding the first light beam from the first light source and the second light beam from the second light source to the objective lens; and light axis control means between the first light source and the beam splitter to remove the center axis of the first light beam.
Furthermore, according to another aspect of the present invention, an optical pick-up apparatus comprises: a first light source for generating a first light beam of a first wavelength to be irradiated on a disk; a second light source for generating a second light beam of a second wavelength to be irradiated on the disk, the second including a light element for generating the second light beam and a location controller for controlling the location of the light element in the planer; and a light path for irradiating the first light beam from the first light source and the second light beam from the second light source on the disk in the shape of a spot.


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patent: 11-39701 (

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