Registers – Coded record sensors – Particular sensor structure
Reexamination Certificate
1999-06-29
2004-05-04
Lee, Michael G. (Department: 2876)
Registers
Coded record sensors
Particular sensor structure
C235S375000, C235S457000, C235S462340, C369S112090, C369S112100, C369S112270
Reexamination Certificate
active
06729541
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to information technologies, and relates in particular to an apparatus for quickly accessing information stored in any specific recording layer in an ultra-high capacity storage device based on laminated holograms, a recording medium for information storage and a method of accessing the information and an illumination head for use in such a recording apparatus.
2. Description of the Related Art
There has been a growing need for compact, high capacity memory devices to meet the demands of mobile computing devices and other similar data storage devices. The simplest card type memory device currently in use is a magnetic stripe bonded to a card base, but because of its inherent small memory capacity, they are only useful in a limited number of applications.
FIG. 23
shows an example of the card type IC memory device &egr; having a higher memory capacity than the magnetic card. Such a device &egr; is comprised by embedding a memory element, such as ROM and flash ROM, in an IC card medium
23
, and is supported by a card guide
24
provided on a data accessing device. Data are read from or written in the memory element by contacting a read/write electrode
25
with a read/write head
26
provided on the accessing apparatus.
However, in the case of the conventional IC cards, although the memory capacity is higher than the magnetic cards, it is still insufficient to meet the future requirements for increasing the memory sizes to several hundred megabits to several gigabits. Costs of bits in such devices are also high and, therefore, they are not suitable as practical future high capacity memory devices.
FIG. 24
shows another example of a similar IC card
101
to be processed by a reading apparatus comprised by a read head
102
, electrodes for read or write functions, and guide rollers
104
for positioning the IC card
101
. Compared with the magnetic cards, their memory capacity is much higher but is still insufficient to meet the needs of mega to giga range of bit memory capacity. This device is also not suitable for future high capacity memory device because of the high costs for making a three-dimensional architecture required for uses in multilayer devices and information input/output circuits.
It has been suggested that higher memory capacities can be realized by using holograms to record information. Hologram recording is anticipated to be a likely future medium for software distribution because of the low unit cost of bits as well as the difficulty of counterfeiting. In particular, planar hologram ROMs can be mass-produced using a printing technology, and a further increase in the density of recording volume is possible through the use of a holographic card in which a planar hologram is embedded in a waveguide and the data are replicated from one specified layer using waveguided light as reference light (refer to a Japanese Patent Application, Second Publication, Hei 10-32578).
In the holographic data storage method, a multi-layered waveguide recording medium is produced by alternating a core layer and a clad layer, and information is recorded as scattering centers in each waveguide layer. Desired information can be reproduced by coupling an input light with a target waveguide layer to reproduce only the desired hologram image. This technology presents a distinct feature that the card medium can be structured such that other waveguide layers are prevented from coupling, thereby suppressing the chances of cross talk.
FIG. 25
shows an example of a candidate for the high capacity holographic memory card
105
, containing multi-layered ROM devices of ten to several tens of micrometers interlayer spacing The card type recording medium
105
includes a plurality of recording layers
106
, each layer having a wedge-shaped hologram (ROM) to be read as a hologram image H out of the layer (actually, on both surfaces of the layer) when an illumination light is injected from a wedge tip
106
a
. The hologram image can be read at highspeed by a solid-state recording device
107
.
The information recording card
105
can be manufactured by a relatively simple process of laminating the hologram recording layers
106
, resulting in increasing the thickness of the data storage section and the memory capacity.
However, it is necessary for this recording card
105
to be able to produce a hologram image from a specific layer of the laminated structure, by focusing the beam L precisely at a definable hologram layer of the card medium, so as to propagate and scatter the input light within that layer only to produce the desired hologram image H while avoiding a cross talk between the layers.
For this purpose, the beam spot La of the light beam L is not only required to focus on the light injection end
106
a
(base of the wedge) but also to move on one axis in the thickness direction of the card medium
105
, as well as to be able to move in the x and y directions as shown in FIG.
25
. As illustrated in
FIG. 25
, the card medium
105
is scanned in the x, y directions quickly and smoothly by a beam spot La, generated from a light source
108
, to focus the light through a lens
100
of an optical system
109
on the specific layer of the multilayer card medium
105
.
FIG. 26
shows another example of the IC card. This IC card
201
is similar to the IC card
101
shown in
FIG. 24
, and it is still insufficient to hold data in the range of several hundred mega bits to giga bits, and considering the difficulty of producing a laminated magnetic card in three-dimensions and the high cost of bits, there is little practical potential for this design.
FIG. 27
shows another example of a high-capacity memory medium in the form of a hologram card
203
, comprised by a lamination of hologram patterns spaced apart at about several tens of micrometers, recorded in wedge type recording layers
241
. Input light is injected from the base of the wedge and a hologram image is produced on both sides of the memory section, and is recorded with a solid state imaging element
205
.
The hologram card medium
203
can be made by laminating recording layers, and each recording layer produces a two-dimensional hologram which can be transmitted quickly. In this system also, the beam spot La must be moved in three-dimensions to access data recorded in individual recording layers.
The primary problem in such systems is the precision required in the complex movement of the beam spot La in a three-dimensional space, at sub-micron precision to obtain the required degree of recording density. For this reason, such systems have not been practical for the needs of high speed data transmission.
Although a potential for low cost recording has been indicated by the use of holographic recording technology, some of the important basic needs have not been properly addressed in this technology. For example, it is necessary to couple the light to a specific waveguide layer in order to access data recorded on this specific waveguide layer, but presently, neither the method of simple detection of the coupling state between the input light and the waveguide layer nor the method of targeting the specific waveguide layer has been established. Without having such basic techniques firmly in place, it is not possible to establish highspeed accessing to reproducing the data or to devise a practical compact device at low cost.
The holographic technology is used sometimes to prevent counterfeit card as disclosed in a Japanese Patent Application, First Publication, Hei 7-306630. Counterfeit cards can be identified by checking for a hologram image that contains machine readable information recorded on the card medium as well as a decorative hologram image not containing any hard information. However, conventional hologram cards can only record information on one layer only, so that a high capacity memory requires a large recording area. To increase the memory size, a multi-layered card is necessary, but to use such a laminated holographic card for practical pur
Kurokawa Yoshiaki
Ohkubo Toshifumi
Tanabe Takaya
Yagi Shogo
Yamamoto Manabu
Kim Ahshik
Lee Michael G.
Nippon Telegraph & Telephone Corporation
Thelen Reid & Priest LLP
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