Dynamic information storage or retrieval – Specific detail of information handling portion of system – Radiation beam modification of or by storage medium
Reexamination Certificate
1999-10-18
2002-04-02
Huber, Paul W. (Department: 2651)
Dynamic information storage or retrieval
Specific detail of information handling portion of system
Radiation beam modification of or by storage medium
C369S112050, C369S112170, C369S121000
Reexamination Certificate
active
06366548
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an optical pickup and optical device for use in a playback unit for an information recording medium such as an optical disc and more particularly to an optical pickup and optical device preferable for a compatible playback system for digital versatile disc (DVD) and compact disc-write once (CD-R).
2. Description of the Related Art
Currently, a DVD system has been proposed and marketed, and its prevalence has started, the DVD system having a higher density than an optical compact disc (CD) which had already prevailed as a consumer product. In DVD player as a playback unit of this system, compatible playback with CD is indispensable to avoid an overlapping of the devices and complexity of operation upon use. Likewise, the DVD player is also required to be compatible with the CD-R which can be played back by the CD player. A technology for playing back discs of various standards has been developed and further, simplification and reduction of cost for achieving it are problems to be solved.
For the aforementioned CD-R, a laser beam source having 780 nm band laser beam source different from 650 nm band for the DVD is required because reflectivity of an information recording medium has a high wave length dependency and therefore, an optical pickup containing a light source for two wave lengths (wavelengths) is necessary.
FIG. 1
is a schematic structure diagram of a conventional example of the optical pickup device. Referring to
FIG. 1
, a first laser beam source
51
is fixed on a first light receiving device (photodetector) substrate
50
and this first laser beam source
51
emits a light having a wave length (wavelength) of 650 nm. An emission light from the first laser beam source
51
passes through a first hologram device
52
, and a light transmitting through a half mirror
53
is converged by an objective lens
54
and irradiated onto a disc
55
as an information recording medium. Alight reflected by the disc
55
is introduced to the hologram device
52
through the objective lens
54
and half mirror
53
, and in the hologram device
52
, the light is diffracted and divided. Then, ±primary-order (± 1st-order) diffracted light is irradiated to the first light receiving device substrate
50
. A second laser beam source
57
is fixed on a second light receiving device (photodetector) substrate
56
and the second laser beam source
57
emits a light having a wave length of 780 nm. An emission light from the second laser beam source
57
passes through a second hologram device
58
and is reflected by the half mirror
53
and converged by the objective lens
54
and irradiated to the disc
55
as an information recording medium. A light reflected by the disc
55
is introduced to the second hologram device
58
again through the objective lens
54
and half mirror
53
. In the hologram device
58
, the light is diffracted and divided and the ±primary-order (± 1st-order) diffracted light is irradiated to the second light receiving device substrate
56
.
FIG. 2
is a schematic structure diagram of other conventional example of the optical pickup device. In
FIG. 2
, a first laser beam source
60
and a second laser beam source
61
are disposed in the vicinity of each other. The first laser beam source
60
emits a light having a wave length of 650 nm and the second laser beam source
61
emits a light having a wave length of 780 nm. The emission lights from the first laser beam source
60
and second laser beam source
61
are emitted along substantially the same optical axis and reflected by a half mirror
62
. The reflected lights are converged by an objective lens
63
and irradiated to a disc
64
as an information recording medium. Light reflected by the disc
64
passes through the objective lens
63
, passes through the half mirror
62
and is irradiated to a light receiving device substrate
65
.
However, because, in the former conventional example, optical paths from the laser beam sources
51
,
57
to the half mirror
53
of the respective wave lengths are different from each other and the first laser beam source
51
and first light receiving device substrate
50
are disposed apart from the second laser beam source
57
and second light receiving device substrate
56
, therefore, the optical pickup cannot be constructed in a compact configuration.
In the latter conventional example, the first laser beam source
60
and second laser beam source
61
are disposed in the vicinity of each other and although the optical paths thereof are the same, an optical path of incident light to the disc
64
is different from that of reflected light from the disc
64
. Consequently, the first and second laser beam sources
60
,
61
are disposed at a different position from that of the light receiving device substrate
65
. Therefore, the optical pickup can be constructed in a compact configuration like the former example.
Here, such a structure in which the optical paths of the respective lights are the same and an optical path of an incident light to a disc coincides with that of a reflected light from the disc can be considered. In this case, a means for diffracting and dividing lights having different wave lengths is indispensable and further, if such a means is just disposed, usability of light from a laser beam source up to a light receiving device substrate via the disc drops considerably, so that practicability thereof is very low.
On the other hand, in a case for producing an optical device for the former conventional optical pickup, although as shown in
FIG. 1
, an optical device
70
in which a first laser beam source
51
, a first light receiving device substrate
50
and a first hologram device
52
are integrally fixed in a casing(package) and an optical device
71
in which a second laser beam source
57
, a second light receiving device substrate
56
and a second hologram
58
are integrally fixed in a casing(package) can be constructed in a compact configuration each, this example cannot make it possible to combine these optical devices to produce a compact single optical device.
In case for producing an optical device for the latter conventional optical pickup, although as shown in
FIG. 2
, an optical device
73
in which a first laser beam source
60
and a second laser beam source
61
are fixed in a casing(package) can be constructed, this example cannot make it possible to combine the first and second laser beam sources
60
,
61
, light receiving device substrate
65
and the like to produce a compact single optical device.
SUMMARY OF THE INVENTION
Accordingly, the present invention is achieved to solve the above problems, and therefore it is an object of the invention to provide an optical pickup and optical device in which light usability in a process from a laser beam source up to a light receiving device substrate hardly deteriorates unlike a conventional example and which can be constructed in a compact configuration.
To achieve the above object, according to a first aspect of the present invention, there is provided an optical pickup for irradiating light to an information recording medium and reading information by using a reflected light from the information recording medium, the optical pickup comprising: a first laser beam source having a first wave length; a second laser beam source having a second wave length; a first diffraction grating; a second diffraction grating provided on a face different from a face on which the first diffraction grating is provided; and a light receiving device substrate having a plurality of light receiving regions on the same plane, wherein the first laser beam source and the second laser beam source are disposed in the vicinity of each other, emission lights from the first laser beam source and the second laser beam source are emitted to the information recording medium along substantially the same optical axis and a reflected light from the information recording medium is returned along the optica
Berkowitz Marvin C.
Huber Paul W.
Nath Gary M.
Nath & Associates PLLC
Victor Company Of Japan
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