Optical waveguides – Planar optical waveguide
Reexamination Certificate
2003-02-03
2004-08-03
Ullah, Akm Enayet (Department: 2874)
Optical waveguides
Planar optical waveguide
C385S147000, C369S108000, C356S073100
Reexamination Certificate
active
06771867
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an optical memory device with optical waveguide fitted therein and to a method for fabricating such device, and more particularly relates to a method and an apparatus for lamination with a filmy member that is useful in fabricating such an optical memory device.
2. Description of the Related Art
One technique recently proposed in the art comprises introducing light into a flat (card-size) waveguide device that has a pattern formed therein for predetermined light scattering to reconstruct the intended image in an area outside the waveguide device (see, for example,
IEEE Photon. Technol. Lett
., Vol. 9, pp. 958-960, July 1997).
Concretely,
FIG. 18
is to schematically show one example of a card-size slab waveguide device
100
that comprises a core layer
101
and two cladding layers (first and second cladding layers)
102
disposed on both sides (both faces) of the core layer
101
to put it between them. In this, the refractive index and the thickness of the core layer
101
are specifically so controlled that the core layer functions as an optical waveguide. When a fine concave and convex pattern is formed in the interface between the core layer
101
and the cladding layer
102
and when light (incident ray, reference beam, laser ray) is introduced into the core layer (waveguide)
101
via a lens
103
, as in
FIG. 18
, then a part of the light having entered the device scatters at the concave and convex pattern, and the scattered light goes out through the cladding layer
102
as shown by the arrows in FIG.
18
.
Accordingly, when the parameters of light scattering intensity and phase for reconstructing a specific image at a predetermined distance from the face of the waveguide device
101
are computed, and when a fine concave and convex pattern (for information and for information recording) is formed in the core layer
101
in accordance with the thus-computed data, then a desired image can be reconstructed in any desired area outside the waveguide device. To that effect, therefore, the core layer
101
in this device functions as an information-recording layer.
In addition, for example, when a CCD image-receiving unit
104
capable of receiving the scattered light having gone out of the waveguide device is disposed in the predetermined site and when the reconstructed image is digitized into a two-dimensional digital pattern signal (for example, into a light/dark binary pattern, or into a brightness (gray scale-based multi-level pattern), then the reconstructed image may be processed and analyzed in any desired manner with an existing digital image processor (not shown).
FIG. 19
is to schematically show another example of a conventional optical memory device. This comprises a stacked structure of multiple cladding layers
102
and core layers
101
that are alternately laminated to form multiple waveguide layers (recording layers)
101
. In this, the light having scattered at a certain waveguide layer
101
shall cross the other waveguide layers
101
. In general, since the refractive index difference between the core layer
101
and the cladding layer
102
is extremely small, the light having once scattered at a certain waveguide layer
101
re-scatters little in the concave and convex pattern formed in the other waveguide layers
101
, and therefore the reconstructed image is disordered little. Accordingly, in the illustrated device, a large number of images and patterns can be reconstructed in proportion of the number of the stacked layers.
This means that the waveguide device
100
can be used as an optical memory device (for recording media such as ROM), of which the capacity is proportional to the number of the stacked layers of the device. In theory, the optical memory device
100
may have a capacity of about 1 Gigabyte or so per one layer, and it is said that about up to 100 layers may be stacked up in the device. Given that situation, the waveguide device of the type is considered as a hopeful device in the future for mass-storage ROM for moving image recording.
Some other proposals have been made for improving the device. For example, the core layer and the cladding layer of the device are made of resin so as to facilitate the concave and convex patterning on the resin layers. This realizes easy and inexpensive fabrication of optical memory devices having a limited volume, but having a larger capacity for increased mass storage of information therein (for example, as in Japanese Patent Application Nos. 11-131512 and 11-131513).
Now back to FIG.
18
. In a case where the information recorded in the optical memory device
100
is reconstructed, an incident ray (incident laser ray) is led into the core layer
101
, as shown in FIG.
18
. If the cross width of the incident laser ray (incident cross width, or that is, the width of the reference beam irradiation area in the cross direction) is too narrow, only a part of the information area where the concave and convex pattern is formed receives the incident laser ray but the other part could not, and therefore, only a part of the information recorded in the information area could be reconstructed. Accordingly, the cross width of the incident laser ray must be broader than the width of the information area.
On the other hand, if the vertical width of the incident laser ray (incident vertical width, or that is, the width of the reference beam irradiation area in the vertical direction) is broad (namely, if the incident laser ray is thick in the vertical direction), the neighboring multiple core layers shall receive the incident laser ray at the same time. Accordingly, the vertical width of the incident laser ray must be as narrow as possible so that it does not cover the neighboring core layers. Therefore, in general, the spot form of the incident laser ray is long oval, which is long in the lateral direction and is as narrow as possible in the vertical direction
In conventional optical memory devices, the width of the information area is relatively narrow, and therefore, even when the device (especially the core layer therein) is warped or bent, it does not cause any serious problem in reconstructing the information recorded in the device. However, the recent tendency in the art is toward the demand for broadening the information area in optical memory devices in order to increase the quantity of information to be recorded in the devices, and, as a result, the width of the information are a in which the concave and convex pattern is formed is being broadened so as to satisfy the requirement of increasing the quantity of information to be recorded in optical memory devices.
If the width of the information area is broadened as in the above, the optical memory device (especially the core layer therein) shall naturally face the problem that it is readily warped or bent, as compared with the conventional devices where the width of the information area is narrow. As a result, the information recorded in the device having a broad information area is difficult to reconstruct.
Specifically, when the optical memory device (especially the core layer therein) is warped or bent, the entire information area where the concave and convex pattern is formed therein could not receive the incident laser ray all at a time even though the cross width of the incident laser ray is satisfactorily broad. In such a case, only a part of the information area receives the incident laser ray but the other part thereof could not, therefore resulting in image reconstruction failure.
In particular, when the information recorded in an optical memory device is reconstructed, the vertical width of the incident laser ray to be applied to the device is made narrow so that the incident laser ray does not reach the neighboring core layers of the device, as so mentioned hereinabove. Therefore, if the optical memory device (especially the core layer therein) is warped or bent, it will be more difficult to make the incident laser ray reach the entire information area o
Mitsubishi Chemical Corporation
Ullah Akm Enayet
LandOfFree
Optical memory device and method for fabricating optical... 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 memory device and method for fabricating optical..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Optical memory device and method for fabricating optical... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3289627