GB2228817A - Document imaging apparatus - Google Patents

Abstract

Light from a light source (28) is sent along a non coherent optical fibre bundle (26) into a carrier which is positioned adjacent to individual characters (12) on a passing document (10) in a document encoding or cheque sorting machine. A first lens assembly focuses an image of the individual characters (12) down a coherent optical fibre bundle (32) into a housing (38) through a second lens assembly (36) onto the active surface of an integrated circuit chip held on a remote printed circuit board (34) and situated beneath the housing (38). The coherent optical fibre bundle (32) comprises more discreet optical fibres in its diameter than there are picture element in a row of sensors on the integrated circuit chip. Scanning of the characters (12) in a printed row or line of print (14) is achieved by advancement of the document (10) along a track. <IMAGE>

Description

DOCUMENT IMAGING APPARATUS The present invention relates to an apparatus for providing an electronic representation of the image of characters printed upon a document, the electronic representation then being provided for character identification.

Document encoding and cheque sorting machines accept a plurality of documents in an input stack and move them one-by-one through document reading and document printing devices to be sorted into selected output bins.

Whereas, in the past, such machines were of great size and enormous power, and used in relatively small numbers in central locations, it has become the trend in latter years to distribute cheque sorting and document encoding to the peripheral parts of, for example, a banking system.

The enormous cost of high power, high capacity, large machines is inappropriate to such distributed operation and there is a trend towards the creation of ever smaller machines.

In document encoders and cheque sorting machines, it is required to recognise characters, printed upon a cheque or document. The derived data is then used by associated data processing equipment to identify the cheque or document and to pass on charges to the appropriate account or cost centre. One class of machines senses magnetic characters printed upon the document.

Another class of machine, to which the present invention relates, employs an optical image of characters printed on the document and converts the image to electronic signals which can be analysed to determine the identity of the printed characters. In general terms, an optical imaging carrier, bearing optical imaging devices and electronic conversion circuitry, is positioned adjacent to the expected height of a line of printing on a document. The document is moved along a track adjacent to thecarrier. A lens system, an optical image sensor and a lighting system are accommodated upon the carrier and provide, as output, an electrical representation of character images. The carrier is thus bulky and has many electrical wires connected thereto.The requirement for such complete image conversion systems, situated upon a single mechanical carrier adjacent to the document, has proved an impediment to the development of more compact machines, since the carrier requires to be large.

A coherent optical fibre bundle is hereinbefore and hereinafter defined as a bundle of optical fibres, each operative- to transmit light from a first end to a second end, held so that all respective first ends are in alignment, one with another and so that all respective second ends are in alignment, one with another; the individual fibres being so arranged that an image, cast upon a plurality of fibres at said first end, can be recovered unaltered at said second end.

The present invention consists in an apparatus for providing an electronic representation of sensed images of characters on a document, said apparatus comprising: a sensor head proximate to the document; an optical imaging integrate circuit remote from the document; a non-coherent optical fibre bundle operative to carry light from a light source to said sensor head to illuminate the document; a coherent optical fibre bundle operative to transfer an image of the document from said sensor head to the integrated circuit; a first lens for focusing an image of the document into said coherent optical fibre bundle; and a second lens for focusing light from said coherent optical fibre bundle onto said integrated circuit.

In order that light may be best transmitted along the coherent optical fibre, there should be the minimum number of total internal reflections. This is achieved when the light is launched as parallel rays along the coherent optical fibre. Further, it is advantageous that the lens at either end of the coherent optical fibre be of identical design. The present invention therefore provides that the first lens and the second lens each operate with parallel light within the coherent optical fibre so that the same lens assembly may be used at either end of the coherent optical fibre and so that light transmission is optimised.

The assembly of the apparatus, according to the present invention, is greatly simplified by the present invention providing that the second lens is mounted in a housing which clips over the integrated circuit package. In this way, the relationship of the position of the image, projected by the second lens, is constant with regard to the integrated circuit.

In a preferred embodiment of the invention a circuit board, containing electronic decoding circuits, is located remotely from an optical imaging carrier, adjacent to a passing document and at the same height as characters printed thereon. A light source provides light in a non-coherent optical fibre bundle which passes through an angled channel in the carrier to illuminate the document. Light from the non-coherent optical fibre bundle illuminates the document in the field of view of a first lens which focuses an image of characters printed on the passing document into a coherent optical fibre bundle. The coherent optical fibre bundle transfers its image to the printed circuit board and through a housing fixed over a charge-coupled-device optical imaging, integrated circuit. Light from the coherent optical fibre bundle is focused onto the integrated circuit by means of a second lens.The integrated circuit creates electrical representations of character images, capable of subsequent electronic analysis. For preference, the imaging integrated circuit is a linear charge coupled device consisting in a single row of adjacent, mutually contiguous ! imaging cells and scanning of the characters of the document is accomplished by moving the document progressively past the carrier and using movement of the document to advance the image of the document on the imaging integrated circuit which creates a representation, line by line, of characters thereon.

For preference, the lens assembly on the housing is identical with the lens assembly on the carrier and the housing clips onto the printed circuit board by means of elastic clips. The light source is selectably a lightemitting diode, an incandescent source, or any other type of source of illumination suitable to operation of the apparatus.

The present invention is further explained by way of an example, by the following description, taken in conjunction with the appended drawings in which: FIG.1 is an exploded diagram of the component parts of the apparatus of the present invention.

FIG.2 is a cross sectional view through the carrier of FIG.1 along the line X-X' looking in the direction of the arrows.

FIG.3 shows a cross sectional view of each of the non-coherent optical fibre bundles and the coherent optical fibre bundle, of FIG.1.

FIG.4 is a plan view of the optical imaging device which is directly attached to the printed circuit board of FIG.1.

FIG.5 is a cross sectional view taken along the lines Y-Y' of FIG.1 and looking in the direction of the arrows, showing the content of the housing of FIG.1.

FIG.1 shows an exploded view of the apparatus embodying the present invention. In a document or cheque encoding machine, a document 10 bearing characters 12, optically printed along a line of print 14, is moved along a track 16 by wheels, pulleys and any other means well known in the art. The document 10 is trapped between a rear retaining wall 18 and a front retaining wall 20 to move adjacently to an optical imaging carrier 22 whose height, with respect to the document 10, is adjustable in a slot 24 in the front retaining wall 20, the height being selected for the carrier to be adjacent to the line of print 14 on the document 10. A non-coherent optical fibre bundle 26 transmits light from a light source 28 into the carrier 22 to illuminate individual characters 12 on the document 10 as they pass the carrier 22. A first lens assembly 30 is attached to a coherent optical fibre bundle 32 and is held in the carrier 22 to focus images of the characters 12 on the document 10 into the coherent optical fibre bundle 32.

A printed circuit board 34 is located within the document encoding or cheque sorting machine at some distance from the carrier 22. The printed circuit board 34 can be a few centimetres or a few metres away from the carrier 22. The coherent optical fibre bundle 32 joins the printed circuit board 34 to the carrier 22.

The light source 28 may be located at any convenient position within the document encoding or cheque sorting machine. For preference, the light source 28 is situated on the printed circuit board 34. The light source 28 is preferably a light-emitting diode, but can equally be an incandescent source, a laser, a laser diode, or any other device capable of supplying light to the noncoherent optical fibre bundle 26. The non-coherent optical fibre bundle 26 and the coherent optical fibre bundle 32 are ducted tgether between the printed circuit board 34 and the carrier 22. The coherent optical fibre bundle 32 terminates in a second lens assembly 36 passing into a housing 38 which, as will later be described, contains an optical imaging integrated circuit.The printed circuit board 34 contains a microprocessor, data stores and digitizing circuits, according to well known methods in the art, whereby electronic representations of the characters 12 in the line of print 14 on the document 10 can be analysed and identified for further processing. The exact manner of electronic character analysis employed does not form part of this invention.

FIG.2 shows a cross-sectional view through the carrier 22 of FIG.1, cut along the line X-X' and looking in the direction of the arrows. The first lens assembly 30 is provided in a first channel 40 in the carrier 22. The first channel 40 is a straight channel through which the coherent optical fibre bundle 32 passes at a right angle to the plane of the document 10. The first lens assembly 30 is affixed by friction or adhesive over the end of the coherent optical fibre bundle 32 and at the end of the first -channel 40 nearest the document 10. The first lens assembly 30 serves to focus an image of the surface of the document 10 as parallel rays into the coherent optical fibre bundle 32.Stated otherwise, the surface of the document 10 nearest to the first lens assembly 30 is coincident with the focal plane of the first lens assembly 30 so that images of the document 10 are focused at infinity in the coherent optical fibre bundle 32.

The second channel 42 in the carrier 22 is angled towards the first channel 40 proximate to the document 10 and serves to carry the non-coherent optical fibre bundle 26. The terminal end 44 of the non-coherent optical fibre bundle 26 is thereby angled to point straight at that portion 46 of the document 10 focused by the first lens assembly 30. Thus, the non-coherent optical fibre bundle 26 illuminates the document 10 just at that place 46 whose image is focused as parallel light into the coherent optical fibre bundle 32.

FIG.3 shows respective cross-sectional views of the coherent optical fibre bundle 32 and of the noncoherent optical fibre bundle 26. The coherent optical fibre bundle 32 is characterized by comprising many very small optical fibres 47, all parallel to one another and held in a fixed relationship to one another. Thus, an image entering one end of the coherent optical fibre bundle 32 retains its integrity and can be perceived from light exiting from the far end of the coherent optical fibre bundle 32. In the present embodiment, the optical fibre bundle is chosen to be in the region of 0.3 centimetres in active diameter, and to comprise many fibres 47 across its diameter, each coherent optical fibre 47 being close packed in contiguous proximity with adjacent fibres 47 and each fibre being approximately 13 microns in diameter.The coherent optical fibre bundle 32 thereby comprises more than 300 individual fibres 47 across its diameter. By contrast the non-coherent optical fibre bundle 26 contains as few as one, and in any case, relatively fewer larger diameter, not necessarily parallel fibres 49, whose purpose is simply to convey light from one end to the other. It is advantageous in the non-coherent optical fibre bundle 26 that the maximum amount of mixing and confusion of images occurs and jumbling of fibres 49 in order to achieve a uniform illumination field at its far end.

FIG.4 shows a plan view of an integrated circuit imaging device 48 attached to the printed circuit board 34 beneath the housing 38. A window assembly 50 comprises a transparent area 52 beneath which is situated a charge-coupled-device integrated circuit chip 54 having a single row of charge-coupled-device optical sensors 56. In the selected device, there are 256 individual picture elements in the row 56 of optical sensors. The number of fibres in the diameter of the coherent optical fibre bundle 32 exceeds 256 and accordingly, a sharp image of individual line elements of characters 12 can be obtained.As the document 10 moves, as indicated by the arrow 58 (FIG.1), a fresh portion of each character 12 has its image fall upon the row 56 of sensors in the integrated circuit chip 54 and, as is well known in the art, the electronic representation of that portion (or line element) of the character 12 can be retrieved from the chip 54 and stored for analysis. Legs 58 pass through the printed circuit board 34 to hold the package 60 on the printed circuit board and to provide electrical connection to the chip 54.

FIG.5 shows a cross-sectional view along the line 'Y-Y' of FIG.1 looking in the direction of the arrows. The second lens assembly 36 passes through a top aperture 62 in the housing 38 wherein it is affixed by friction or glueing. The second lens assembly 36 reconstructs the image, carried in parallel light down the coherent optical fibre bundle 321on the integrated circuit chip 54. The housing 38 is made of opaque plastic material and comprises attachment legs 64 which pass through attachment holes 66 in the printed circuit board 34 to be held in place by spring clips 68 integrally moulded with the attachment legs 64.By this means, the second lens assembly 36 and the coherent optical fibre bundle 32 are always located at the correct height above the integrated circuit chip 54 and centrally thereover so that an accurate representation of the image is cast upon the surface of the chip 54.

While the image has been hereinbefore described as being focused as parallel light down the coherent optical fibre bundle 32, it is to be understood that other focusing systems could equally be applied. In the present invention, the first lens assembly 30 and the second lens assembly 36 are simply required to cast a sharp focused image of the characters 12 upon the integrated circuit chip 54. Those, skilled in the art will be aware of use of different combinations of lenses of different focal lengths and imaging distance which can fulfil this criterion. In the present embodiment, the use of parallel light in the coherent optical fibre bundle 32 maximizes transmitted light intensity by minimising the number of wall reflections in each optical fibre and the use of identical lenses 30,36, simplifies construction and minimizes cost. Because the -light source 28 and the integrated circuit 48 can be provided on a remote board, it becomes possible to incorporate the electronic components, required for image conversion, previously required to be mounted with the carrier 22, on a single board 34. This greatly simplifies construction and miniaturization of the document encoding or cheque sorting machine and is a major contributor to reduction of cost in manufacture.

Claims (7)

1. An apparatus for providing an electronic representation of sensed images of characters on a document, said apparatus comprising: a sensor head proximate to the document; an optical imaging integrate circuit remote from the document; a non-coherent optical fibre bundle operative to carry light from a light source to said sensor head to illuminate the document; a coherent optical fibre bundle operative to transfer an image of the document from said sensor head to the integrated circuit; a first lens for focusing an image of the document into said coherent optical fibre bundle; and a second lens for focusing light from said coherent optical fibre bundle onto said integrated. circuit.

2. An apparatus according to Claim 1 comprising a housing supporting said second lens in a fixed relationship with said integrated circuit.

3. An apparatus according to Claims 1 or 2 wherein said first lens assembly is identical to said second lens assembly.

4. An apparatus according to any of the previous claims wherein said first lens assembly is operative to focus and image of the document into parallel light rays in said coherent optical fibre bundle; and wherein said second lens assembly is operative to focus parallel rays from said coherent optical fibre bundle onto said integrated circuit.

5. An apparatus according to any of the previous claims wherein said coherent optical fibre bundle comprises a parallel array of individual fibres close-packed to a diameter of 0.3 centimetres, each parallel fibre having a diameter of 13 microns.

6. An apparatus according to any of the preceding claims wherein said sensor head comprises a carrier for holding said first lens and said non-coherent optical fibre bundle proximate to the document, said carrier comprising a first, straight channel for receiving said coherent optical fibre bundle and a second, angled channel for directing the terminal end of said non-coherent optical fibre bundle to shine light in the field of visibility of said first lens.

7. An apparatus substantially as described with reference to the appended drawings.