GB2184315A - Reading electric charge images - Google Patents

Abstract

In a system for transferring a latent image from a charge carrying surface, 30 the surface is moved relatively past and in contact with a brush (10), 38, 38', the brush is formed of a plurality of 'hairs' 44 or 'points' (12) spaced apart in lines, preferably lines of regularly spaced contacting 'points' or 'hairs' of the brush are aligned so that the points or hairs in adjacent lines are offset in the direction of movement of the brush and charge carrying surface. The charge varying over the width of the surface may then be easily detected and displayed as a formed image on a suitable electronic or electro chemical display. <IMAGE>

Description

SPECIFICATION An imaging system The present invention relates to imaging systems.

In order to record images permanently it is known to provide a substrate such as polyester with a conductive layer and a superimposed semi-conducting layer of crystalline cadmium sulphide. This material will hereafter be referred to as a semi-conductive imaging material.

In order two produce an image on the crystalline surface the material is charged in the dark increasing the resistivity to 1014ohm centimetres. The material is then exposed to an image. Sufficient lightfrom the image will completely discharge the surface when the resistivity drops to about 1 07 ohm centimetres.

Exposure to intermediate light levels result in corresponding intermediate resistivity so that the remaining charge on the surface will vary directly as a result of the strength of the imaged light. So as to record the image this film is coated with tonerto produce a visible image.

Whilst toning has certain applications it is essentially a once only use of the material.

An imaging system according to the present invention comprises an imaging station, a sheet of semiconductive crystalline material, means for charging the material, meansforsupporting said material at the imaging station, a brush comprising a plurality of separate conductors and means for moving the brush relative across a crystalline surface of the material so as to detect simultaneously the charge and voltage levels applicable at a plurality of positions on said material's surface and meansforvisuallydisplaying said voltage levels.

Preferablythesemi-conductive material is the aforesaid known material comprising a substrate, a conductive layer and a semi-conductive crystalline layer of cadmium sulphide. It isthecadmium sulphide layerwhich is constructed by the brush.

A fu rther aspect of the invention comprises providing a sheet of semi-conductive crystalline material, charging the material, exposing the charged material to an illuminated image, detecting the voltage ofthe charge at a plurality of points across the width or length of the sheet simultaneouslyand continuing to detect the voltage over an imaged area and displaying the level of voltages detected on a screen to produce a visible image.

The advantage ofthe system and method of the invention isthat an image can be very rapidly 'viewed' and either be displayed locally or transmitted to a remote station.The system is essentially an analogue image detecting system which can display a fine variation of shades between light and dark orwhite and black so as to produce a very true image. The resultant image is finer than that produced by digital imaging methods but has many of the advantages in ease oftransmission enjoyed bydigital systems.

Furthermore due to the fine size of the crystalline formation obtainable with cadmium sulphide ofthe order of 14,000 crystals per linear millimetre, each crystal acting as a recording element, it is possible to use such a system for very dense or highly reduced imageswithfinerreductionsthan48times.Thus microdata recording is a suitable subject.

The brush construction is probable a limiting factor in the construction, however, it is believed possible to reduce separation between individual detectors in the brush to 4 microns and by providing a double row of detectors with the second row scanning the gaps between the detectors in the first row,itshould be possible to reduce the effective detector separation to 2 microns with a resultantdetection capability of 500 lines per millimetre.

Such a replication of an image issufficientlyfinefor useofthesystem in micrographicdata handling.

The meansfordisplaying the iamge may bea cathode ray screen, a micro LED screen, or else the voltages detected can be applied to a toned sheet of material such as paper so as to produce a print out.

The sheet of material to which toner may be applied may also beanothersheetofsemi-conductive imaging material, the image detecting brush ofthis invention is used to 'draw off' the image which can be amplified oraltered before applying back again to the further sheet of semi-conductive imaging material by similar brush means.

Embodiments of the inventorwill now be described byway of example with reference to the accompanying drawings in which: Figure 1 shows in plan view a brush forthe imaging system of the invention according to a first arrangement, wich a magnified inset showing the conductor layout.

Figure 2 shows side elevation ofthe brush of Figure 1, Figure 3 shows an end elevation of the brush of Figure 1, Figure4shows a film to be read or recorded on being moved diag ram matical Iy across the brush of Figure 1, FigureS is a diagram of the system of the invention, Figure 6 is a perspective view of another brush for the imaging system ofthe invention, and Figure 7 is a prospective magnified view ofthe imaging material used in the invention.

The imaging system ofthe invention is shown diagrammatically in Figure 5 in which 2 is an imaging station, 4 is a sheet ofsem-conductive crystalline imaging material preferably of the crystalline cad mium sulphide type as already described and 6 isa charging device which can be of the corona type over which the material 4 is moved. The sheet material 4 is supportedatthe imaging station by either an airflow system as shown in US Patent No. 4,176,947 or else be means of a positioning mechanism such as is used in US Patent No. 4,118,123orany other suitable conveying system. The supporting system is diagrammaticallyshown at8.

Abrush 10 can be ofthe sort shown in Figures2 and The drawing(s) originally filed was (were) informal and the print here reproduced is taken from a later filed formal copy.

The claims were filed later than the filing date within the period prescribed by Rule 25(1) of the Patents Rules 1982.

3 orelse as shown in figure 6 and which will be described later is positioned so that the material 8 can be moved across its surface. The brush has a plurality ofseparate conductors and the supporting means 8 moves the material 4 across the brush surface so as to conductsimultaneouslythe charge and voltage levels applicable on a plurality of positions on the material's surface,a magnified view of which is shown in Figure 7.

Meansforvisuallydisplaying the voltage levels over the material's surface may be either a cathode ray tube and LED display or else a similar brush system to the detecting arrangements shown in Fig. 2 which is shown diagrammatically at 14 in figure 5. The cathode ray tube or LED display is shown as an alternative display at 16 in Figure 5.

In orderto enhance the signal received at the imaging station 2, an amplifier 18 is provided and control circuitry 20 may be provided to analyse and amend the image as is necessary.

The crystalline structure of the imaging material is shown in detail in Figure 7 in which crystals spaced some 700A apart (14,000 per linear millimetre) and 3,500 high are deposited on an ohmic layer32 some 200 thickwhich is deposited in turn on a substrate 34 of a plastics or even metal backed material.

The resulting crystalline density issome 196,000,000 elements pew square millimetre. Each crystal can store four a long period a charge dependent on a light level impinging on it after being charged, so thatthe variation of light overthe surface of the material may be recorded as an analogue record ratherthan even in part a digital presence or non presenceofa point charge.

Whilst it is known to use the data recorded by toning the surface, this is a substantial waste of its storage capacitywhich is capable of recording in extremely fine form very varying light levels.

In orderto detect the light level at a group of crystals, which is sufficient for normal purposes, a brush comprising a large number of conductive elements is used. These brushes are either of the 'fakir'sbed' form of Figure 2 or else in the form shown in Figure 6.

It is the aim to achieve a read out of about 1,000 lines per millimetre andtothis enda stacked offset array of pins is used in thefakir's bed version. The inset in Figure 1 shows lines ofthe conductors 12 designed diagonally to the direction of film travel. In this way by relatively wide distancing apart of conductors it is possible to achieve a very fine distancing in the direction of fi I m travel .

In the Figure 6 brushes arrangement, offset brushes 38 reformed by deposition of a mettalic coating 40 on a substrate 42 of polyester or ceramic material Individual 'hairs' 44 of the brushes are formed by cutting by laser channels 46 at intervals. Several brushes3 & an be providedwith their rows hairs offsetto the line of film movement. Even with one brush it could be possible to achieve 2 micron spacing between hairs in one brush or 1 micron (1,000 lines per millimetrelwithtwo brushes 38,38'.

Claims (7)

1. An imaging system comprising an imaging station, a sheet ofsemi-conductive crystalline mate rial,meansforcarryingthematerial,meansfor supporting said material at the imaging station, a brush comprising a plurality of sepa rate conductors and means for moving the brush relatively across a crystalline surface ofthe material so asto detect simultaneously the charge and voltage levels applicable at a plurality of positions on said material's surface and means for visually displaying said voltage levels.

2. A system as claimed in claim 1 wherein the crystalline material comprises a substrate, a conductive layer and a semi-conductive crystalline layerof cadmium sulphide, the cadmium sulphide layers being arranged to be contacted by the brush.

3. Asystem accordingtoclaim 1 or2whereinthe brush informed of a plurality of lines of elements angled to the direction of relative movement between the brush and material.

4. A system as claimed in 1 or 2 wherein the brush comprises a plurality of strips of substrate electrically insulating material on which are electro-conductive 'hairs' formed by cutting at intervals an electroconductive coating applied to the substrate so as to form lines of conductive material separated by nonconductive material.

5. A method offorming a visible image comprising providing a sheet of sem-conductive crystalline material, charging the material, exposing the charged material to an illuminated image, detecting the voltage of the charge at a plurality of points across the width or length ofthesheetsimultaneouslyand continuing to detectthe voltage overan imaged area and displaying the level of voltages detected on a screen to producetheyisible image.

6. An imaging system substantially as described with reference to the accompnaying drawings.

7. A method offorming a visible image substantially as described with reference to the accompanying drawings.