Dynamic information storage or retrieval – Specific detail of information handling portion of system – Radiation beam modification of or by storage medium
Reexamination Certificate
1998-03-02
2001-03-20
Neyzari, Ali (Department: 2651)
Dynamic information storage or retrieval
Specific detail of information handling portion of system
Radiation beam modification of or by storage medium
C369S112040, C369S044370, C369S094000, C369S124120, C365S108000, C365S235000
Reexamination Certificate
active
06205106
ABSTRACT:
TECHNICAL FIELD
The invention relates to a method and a device for the storing of information. Preferably the device is formed as a memory card. Such a card can be used for public data storage and archiving of documents in libraries, health care, and also for replacing micro fiche systems. The invention relates also to a system for positioning such a card.
PRIOR ART
Prior art optical memory cards are commercially available from Dexter Inc., USA and from Canon, Japan. The storage capacity of prior art cards is 4,2 Mbyte, and the write and read speed is approximately 30KByte/s. The information in the card is stored when a high energy laser beam burns a hole in a thin metal layer of the card. Information stored in the card is read by detecting a difference in reflection from a memory point and from said metal layer.
SUMMARY OF THE INVENTION
According to the invention there is used a passive storage media having a layer of photoinduced light absorbing and transmitive properties. Preferably data is written or stored in the media by exposing an area in the layer having a plurality of elements to an image containing any desired information. When the layer is exposed to light different properties of the elements are changed. Data is read out by exposing said elements to light and analyzing the absorbing proporties in each of the elements. Light is directed and controlled by an optical system.
The optical system including a multiporpose objective is intended to perform the following tasks:
writing data into the storage medium
reading-out data from the storage medium
error signal generation for holding in position the storage medium
positioning the storage medium in Z-direction.
Writing can be defined as a local modification of the optical properties of the storage medium by a linearly polarised laser light, preferably a blue laser. To perform writing it is approriate to control the light wavelength, the light intensity (spatial distribution and magnitude), the intensity pattern, the light polarisation and the wavefront shape.
Reading-out can be defined as the retrieving of information encoded in the storage medium. To perform reading-out it is approriate to control the light wavelength, the light intensity (spatial distribution and magnitude), the the light polarisation and the wavefront shape. Preferably a red laser is used.
An error signal is used by means that moves the storage material to determine when the memory pixels are imaged precisely and sharply onto the CCD pixels. This requires control of:
X-Y position of the storage medium (i.e. translation in its plane)
orientation of the storage medium (i.e. rotation around the Z-axis which is perpendicular to its plane)
position of storage medium along the Z-axis (i.e. perpendicularly to its plane).
The X-Y position of the storage medium will be identified by special “marker symbols” written into the storage medium during its fabrication. The error signal resulting from their misposition (translation as well as orientation) will be generated by photodetectors onto which they are imaged by an objective. This procedure is a kind of “tracking”.
Positioning the storage material along the Z-axis is controlled by other means. There is a lens system which produces spots of focused light at a fixed distance from the objective in the storage material. These spots are reflected by the memory card and then are analyzed through a lens system by photodetectors. This and similar procedures are called “autofocusing”.
The optical system has also to carry out the correction which was determined by the error-signal of autofocusing. This requires that parts of the objective be movable, separately from the other parts of the optical system.
The functions of illumination, directing light containing the information to be stored onto the storage medium, imaging the storage medium onto a detector and the error signal generation preferably will all be implemented by the same objective. However, the different functions require some additional elements.
Preferably a side-chain liquid crystalline (SCLC) polyester film is used as a storage medium. An image containing information to be stored is created in an electrooptical element and is imaged on the storage medium. In one embodiment the storage medium is formed as a “write once read multiplicate” (WORM) device. It is possible to erase stored information in any memory position and again write in an erased position. Data can be erased either by a erasure of the complete storage medium in one step or by a selective erasure of specific memory blocks. It is also possible to use a device according to the invention in a more conventional rotating medium.
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Chu Kim-Kwok
Mathews, Collins Shepherd & Gould P.A.
Neyzari Ali
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