GB2024561A - Digital Facsimile System - Google Patents

Abstract

A data storage and retrieval system includes a scanner for scanning an original document, a digitiser for digitising the output of the scanner to provide a digital representation of the scanned data on the document, and means for storing the digitised data on a computer- compatible record medium whereby the original data may be retrieved and reproduced in human-readable form at a local or remote computer terminal.

Description

SPECIFICATION Data Storage and Retrieval System This invention relates to a data storage and retrieval system.

It is known that the space required to store complete documents, and the access time to retrieve the documents, can both be reduced by microfilm or microfiche techniques. In addition, for character text data which is translatable into machine readable codes, such as ASCII or EBDIC, data can be entered into digital storage media by means of optical character recognition or word processing systems. Such data can be retrieved from the store and read out on a line printer.

An object of the present invention is to provide a data storage and retrieval system which uses digital storage media but which is capable of storing and reproducing a facsimile of a document.

In accordance with the present invention a data storage and retrieval system comprises a scanner for scanning an original document, a digitiser for digitising the output of the scanner to provide a digital representation of the scanned data, and means for storing the digitised data on a computer-compatible record medium whereby the original data may be retrieved and reproduced in human-readable form at a local or remote computer terminal.

Preferably the digital data is coded in such a form as to store a complete facsimile of the document. This is achieved by scanning the document in a series of horizontal scan lines, each scan line being sampled at a number of fixed points known as pixels. Each sample pixel is coded to represent a Grey Scale value.

The resolution of such a system is limited only by the number of scan lines and the number of pixels in each scan line.

The storage medium preferably comprises a mass optical store, such as a laser access memory. In this case, the digitised data is initially fed to an intermediate store such as a magnetic disc store, so that sufficient data can be accumulated and then transferred into the mass store at a sufficiently high rate to provide the required density of storage.

In contrast to known storage systems, the stored pixel data is neither human-readable nor machine readable, and it can only be retrieved and reproduced by feeding the data out to a facsimile receiver at an integrated facsimile terminal.

By way of example only, an embodiment of the invention will now be described with reference to the accompanying drawings in which:~ Fig. 1 is a block diagram of a digitised document storage and retrieval system providing on-line access to an archival data base system by a large number of geographically distributed remote terminals.

Fig. 2 is a block diagram of an integrated facsimile terminal in the system of Fig. 1.

Fig. 3 is a block diagram of the network access controller in the system of Fig. 1.

Fig. 4 is a block diagram of the abstract and index data system in the system of Fig. 1, and Fig. 5 is a block diagram of the archival data base system in the system of Fig. 1.

In Fig. 1, four integrated facsimile terminals IFT 1 to IFT 4 are shown connected to packet switch exchanges PSE, each terminal having a data terminal equipment-packet DT/P device operating in a virtual call mode Data from the packet switch exchanges is fed to a network access controller NAC which also has a data terminal equipmentpacket DTEP device, and is connected to an archival data base system ADBS and to an abstract and index data system AIDS.

An integrated fascimile terminal is illustrated in Fig. 2. This comprises:~ 1. A high resolution digital laser facsimile transmitter/receiver LFT/LFR interfaced to a micro processor unit MPU1 which provides data compression/expansion, grey scale selection, scan timing control, and input/output line scan buffering.

2. A pair of double density floppy discs FD1, FD2 for input/output document data spooling.

3. A visual display unit VDU and keyboard KB interfaced to a micro process unit MPU 2 to provide input/output communication with a terminal operator in interactive conversational mode.

4. A micro processor unit MPU3 to provide overall terminal control functions and line rate control.

5. A micro processor based X25 interface controller ICI providing HDLC level 1,2,3, functions and host protocols.

Data is fed out from the terminal along a data line at 9,600 bps.

The terminal is designed to enable any source document with mixed text structure to be coded at pixel level, indexed, transmitted and stored in the archival data base system ADBS such that the facsimile of the document may be retrieved, transmitted and reproduced either at the originating terminal or any other authorised terminal within the network.

To enter a document into the system, the operator first enters the necessary digital control data via the standard programmable VDU and key board KB, this data being stored temporarily on the floppy discs Fib1, FD2. The document to be entered is then applied to the high resolution laser facsimile transmitter LFT which scans the document in a series of parallel horizontal sweeps, sampling a fixed number of points during each scan. The resolution is 10 lines per mm.

Each point is referred to as a pixel and is converted to a numerical value depending upon the density of print (as measured on the Grey scale) at that point. For example, with 20#22 bit Grey scale coding, values could range from 0 White to 11 Black. It would be possible, however, to provide 2 ~28 bit Grey scale coding for even better resolution.

The digitised output from the LFT is applied to the micro processor unit MPU1 which performs a data compression function depending upon the black/white ratio of the text data, a number of sequential scan lines being stored simultaneously in order to maximise the compression factor. The data in compressed form is then buffered on to the floppy discs FD1, FD2. Upon completion of input of the complete document, a transmission path is established to the ADBS and the data is transmitted.

To illustrate the data compression, suppose the digitised output contained the sequence 00000000110000000000 representing four white pixels, a black pixel, and five white pixels. If a sequence of white pixels is represented by a coded number X, and a sequence of black pixels is represented by a coded number Y, then the above sequence could be transmitted and stored simply as 4X,1Y,5X. Depending on the print size and density, compression factors of between 5:1 and 15:1 can be achieved.

To retrieve a document from the ADBS, the operator enters the necessary digital control data via the VDU and Key Board KB. This data is buffered on to floppy discs FD1, FD2, a transmission path established and the request identifying data sent to the ADBS. Upon receipt of this data the ADBS will retrieve the required document pixel data and transmit this data to the floppy disc unit FD 1, FD2. When transmission and error checking functions have been completed, the transmission path is broken and the document data is fed out to the high resolution laser facsimile receiver LFR via the micro processor unit MPU1 which performs data expansion functions.

The network access controller NAC of Fig. 1 is shown schematically in more detail in Fig. 3. It comprises: 1. A micro processor based X25 interface controller lC2 providing each DCL level 1,2,3 functions and host protocols to support four virtual 9,600 bps circuits.

2. Four micro processor based communication line controllers P1, P2, P3 and P4 which receive data from the interface controller 1C2 and are interfaced with the micro processor routing controllers MPU5 and MPU6.

3. A micro processor routing controller MPU6 for the abstract and index data system AIDS (Fig.

1). This controller is responsible for the routing of digital control and digital text data between the communication line terminal equipment and the abstract and index data system AIDS. It is also responsible for maintainence of the authorised terminal users directory and terminal characteristics tables, the transfer of specific access control information from the AIDS system to enable storage/retrieval operations to be executed by the ADBS facility.

4. A micro processor routing controller MPU5 for the archival data base system ADBS. This controller is responsible for the routing of document pixel data between the ADBS facility and the communication line terminal equipment.

It is also responsible for the transfer of specific access control information from the AIDS facility to the ADBS facility.

5. Communication controllers to provide high speed parallel/synchronous data transfer between the routing controllers MPU5 and MPU6 and the AIDS/ADBS facilities.

The AIDS facility is shown schematically in Fig.

4. It consists of a standard digital data base system with conventional digital computer storage facilitiss. Index and other fast access data is maintained on exchangeable discs D1-D5 while abstract and security dump data are maintained on high density magnetic tapes Ml- M3.

Data is selectively routed to and from the magnetic tapes and storage discs by a central processing unit CPU2.

The archival data base system ADBS is illustrated in Fig. 5. It consists of a standard main/frame digital computer CPU3 with a laser access memory LAM and disc storage facilities.

Data received from and transmitted to the communication controller CC1 is staged by staging controllers SC2, SC3 to the dual access disc storage system D7-D 10. Input digital control data elements are interpreted by the system and control programme SC1 to control access to the laser storage system, in order to store or retrieve document pixel data, via the staging disc system D7-Dl 0. A directory of physical files within the LAM system is maintained on the system disc storage facility Dl 1-D13.

A typical LAM store would have a capacity of 6.1010 bytes and data would be transferred into the store at a rate of 1 M bytes per second. It is necessary to transfer data at this rate in order to provide the required density of storage. A typical A4 page would consist of 2M bytes, and these bytes would be fed to the LAM store in a block on a 128 bit highway.

Because data is fed out from the facsimile transmitter at a transfer rate of only 1 OK bps, whereas data must be transferred into the LAM at 1 M bps, data is first transferred into the staging disc system D7-Dl0. This system has a very rapid access time (say 70 milliseconds compared to 3 or 4 minutes for the laser access memory) but a much slower transfer rate, say 400 K bps.

The system may service say 100 of the integrated facsimile terminals IFT. If several of these terminals request a document at about the same time, the central process unit CPU 3 would control the requests so that they would be held while data was fed out from the laser access memory into the disc storage system D7-Dl 0.

Thereafter the terminals would be able to obtain the data from the discs with an access time of about 70 milliseconds.

It is not necessary that each of the integrated facsimile terminals IFT should include a facsimile transmitter. In many cases the users of such terminals may only wish to retrieve documents from the main store.

Similarly, it is not necessary that data is fed into the laser access memory via a packet switch exchange. A facsimile transmitter would normally be provided at the same terminal as the laser access memory so that document pixel data could be fed directly into the central processing unit CPU3 from the transmitter.

Claims (6)

Claims

1. A data storage and retrieval system comprising a scanner for scanning an orignal document, a digitiser for digitising the output of the scanner to provide a digital representation of the scanned data on the document, and means for storing the digitised data on a computercompatible record medium whereby the original data may be retrieved and reproduced in humanreadable form at a local or remote computer terminal.

2. A system according to Claim 1, in which the scanner and digitiser comprise a facsimile transmitter such that each scan line is sampled at a predetermined number of points or pixels and the sampled data at each point or pixel is digitised.

3. A system according to Claim 1 or Claim 2, in which the record medium comprises a random access memory.

4. A system according to Claim 3, in which the means for storing the digitised data in the random access memory includes a processing unit for selectively routing the digitised data between an intermediate magnetic surface storage system and the main random access memory in response to control data fed to the processing unit with the digitised document data.

5. A data storage and retrieval system comprising scanning an original document, sampling each scan line at a predetermined number of points or pixels, digitising the sampled data at each point or pixel, and storing the digitised data on a computer-compatible record medium such that it may be retrieved and reproduced at a local or remote computer terminal.

6. A data storage and retrieval system substantially as herein described with reference to the accompanying drawings.