GB2120040A - Facsimile recorder - Google Patents

Abstract

Facsimile recorder for recording image information line by line, comprising a controllable optical component (2) with a plurality of spot elements (3) from which spots of light are directed onto a record medium along the length of a recording line. The spot elements of the controllable optical components are combined in rows of m>1 spot elements each and these k rows are staggered in a particular relationship parallel to each other. <IMAGE>

Description

SPECIFICATION Facsimile recorder This invention relates to a facsimile recorder for recording image information line by line, ofthe kind comprising a controllable optical component with a plurality of spot elements from which spots of light are directed onto a record medium along the length of a recording line.

Recorders ofthis kind comprise a light-sensitive record medium,e.g. photographic printing paperor an intermediate record medium, and a passive spot exposure system in the form of an electrically controlled optical component with spot elements which pass or block the light; see, for example, German DE-OS 2557254. That component includes optical means for imaging a light source onto the record medium overthewidth of one recording line.

Arranged in the path ofthe light directed onto the record medium are two polarizers equal in width to the light beam, and between the two polarizers is the electro-optical component, which has a plurality of separately energizable lead wires whose number and arrangement correspond to the number and arrangementofthe spots on the lineto be written. The electro-optical component is made oftransparent ferroelectric ceramic, such as lead lanthanum zirconatetitanate (PLZT).

In an active exposure system, the optical component consists of a plurality of controllable light emitters arranged closely side by side, normally with a spacing of about 100um. Suitable light-emitting spot elements are light-emitting diodes, plasma cells or electro-luminescent elements.

Current commercially available facsimile recorders have a resolution of 3.85 lines/mm or 7.7 lines/mm at a transmission period of one to six minutesforone DIN-A4 page, the spots of each line being recorded one after the other. Future facsimile recorders are to have a resolution of 7.7 lines/mm at a transmission period of 5to 20 seconds for one DlN-A4 page, so that 1,728 spots will be recorded in each line of a DIN-A4 page.

Such a high spot density involves technical problems, however. At a resolution of 7.7 Iineslmm, 7.7 electrodes per mm must be driven with a voltage in the range of about 100-200 V (DC voltage). Thus, the electrode leadsmustbeverynarrowin orderto prevent arcing, and they must be separated by as great a spacing as possible. This, in turn, has an unfavourabte effect on the life of the diodes and leads, for it poses adherence and breaking-strength problems and problems associated with thermal over loading due to the high currentdensityintheeletrodes and their leads.Another disadvantage of such passive exposure systems is that the eletrodesthemselves have a certain width, which narrows the lightpenetration windows and, hence, results in optical intensity losses and logically necessitates higher illumination, i.e.,a stronger light source. Thefore- going also appliesanalogouslyto active exposure systems.

Accordingly, itis an objectofthe invention to provide a controllable component for both passive and active spot exposure systems of facsimile recorderv which avoids the above difficulties and disadvantages and permits the required shorter transmission period at a high degree of reliability.

According to the invention in its broadest aspect, a facsimile recorderforrecording image information line by line, of the kind referred to is characterized in that the spot elements ofthe controllable optical component are combined ink rows of m > 1 spot elementseach,thatthese trows are staggered parallel to each other, with the 1 sot, (k+ 1 )th, (2k+1)th...

(nk+1 )th spot element forming the first row, the 2nd, (k+2)th,(2k+2)th... (nk+2)th spot element forming the second row, and the kth,2kth,3kth... nkth spot element forming the kth row, where n = 0 ...m, and that the individual rows are energized successively in time. lnthiswayasinglelinewill beformedonthe intermediate record medium by suitable spot control using electronic circuitry.

Embodiments of the invention will now be described byway of example with reference to the accompanying drawings, in which: Fig. 1 shows the principle of a facsimile recorder in accordance with the invention which uses an active spot exposure system; Fig. 2 shows schematically howwriting is effected with staggered rows of spot elements of a spot exposure system; Fig. 3 is a top view of a passive spot exposure system formed from a PLZTstrip, and Fig. 4 is a top view of a passive spot exposure system consisting of two PLZT strips.

In Fig. 1, the light-sensitive record medium is a drum 1,e.g.,aselenium-coatedaluminumdrum.Theactive spot exposure system 2 has an overall thickness of about 1.6 mm and comprises a slit or aperture mask 3 whose slits or apertures have a width or diameter, respectively, of 100 clam; the distance between the drum 1 and the slit mask3 is about 500 lim. The slit mask3 is followed by a glass substrate 4, about 1.5 mm in thickness, to which is applied an electrode array 8. This electrode array 8 is followed by an electroluminescent layer 5 with a thickness of 40 clam, which is covered with a rear electrode 6. Afocusing device 7 or a device reducing the illumination angle is interposed between the drum 1 and the slit mask 3.The electrodes 8 are staggered with respect two the aperturesofthe mask3.

Fig. 2 again shows the light-sensitive record carrier 1, which rotates clockwise. Shown beside it is the spot exposure system 2 with staggered electrodes 3. As a result of the staggered arrangement ofthe electrodes and with suitable control, each row is "interrogated" twice, namelyfirsttheodd-numberedspotelements and then the even-numbered spot elements in succession. The interrogated odd-numbered spot elements then form the first half line (A) on the record medium 1. Through the lapse of time during the clockwise rotation of the record medium 1 ,the interrogated even-numbered spot elements of the second row then completethefirst half line (at A'). With this system,the spots arethus sequenced in a line through the lapse of time.

As shown in Fig. B,arow of the spot exposure system consists of a PLZTstrip 1 with centre electrode 2, which is at a fixed potential, an electrode array 3, and penetration windows 4 (shown symboli cally). The electrodes and, thus, the penetration windows are not placed opposite each other, but are staggered with respectto each other. The direction of transillumination is normal to the plane ofthe paper.

Fig. 4 shows an embodiment with two PLZT strips 1 having the rear electrodes 2 sandwiched therebetween. The PLZT strips 1 are provided with electrode arrays 3, and the penetration windows 4 are again shown symbolically. The direction of transillumination is again normal to the plane ofthe paper.

The principal advantages offered by the invention are that electrodes and leads of at least double width can be used with passive spot exposure systems, which extends the life ofthe electrodes and leads. In addition, the electrode spacings are greater, whereby the risk of arcing is reduced. Thus, compared with systems in which the electrode leads are provided on one side only, larger manufacturing tolerances are permissibleforthe electrode width. The greaterwidth ofthe electrodes also shows an advantage over interdigital electrode arrays. Another advantage ofthe electrode array according to the invention is that the penetration window is enlarged; this reduces intensity losses and permits the use of a weaker light source.

Theforegoing also applies to active spot exposure systems. The active light-emitting elements can be made at least twice as large. Another advantage results from the fact that the rows of spot elements are first manufactured separately and then fitted together to form a displaced double row. This increases the yield because only half of the spot elements are provided on each row. The foregoing applies in particularto active light-emitting elements based on the electro-luminescent or vacuum4luorescent effect orto light-emitting diodes.

Although onlyfacsimile recorders with an in termediate record medium have been discussed, it is self-evidentthatthe recorder proposed also permits the use of a photosensitive paper if the spectral characteristic and light intensity ofthe active or passive optical component are adapted to the paper.

Claims (8)

1. Afacsimile recorderfor recording image information line by line, ofthe kind comprising a controllable optical component with a plurality of spot elements from which spots of light are directed onto a record medium along the length of a recording line, characterized in that the spot elements of the controll able optical component are combined ink rows of m > 1 spot elements each, that these k rows are staggered parallel to each other, with the 1 sot, (k+1 )th, (2k+1 )to..

. (nk+ 1 Xth spot element forming the first row, the 2nd, (k+2)th, (2k+2)th . . . (nk+2)th spot element forming the second row, and the kth,2kth,3kth... nkth spot elementformingthekth row, where n=O... . and thatthe individual rows are energized successively in time.

2. Afacsimile recorder as claimed in claim 1, characterized in that the controllable optical compo nent is alight-switching, electrically or magnetically controllable component.

3. Afacsimile recorder as claimed in claim 1, characterized in thatthe rows of the controllable optical component are made oftransparentferroelectric ceramic.

4. Afacsimile recorder as claimed in claim 3, characterized in thatthetransparentferro-electric ceramic is lead lanthanum zirconate titanate (PLZT).

5. Afacsimile recorder as claimed in claim 1 or2, characterized in that the spot elements are lightemitting diodes.

6. Afacsimile recorder as claimed in claim 1 or2, characterized in that the spot elements are plasma cells.

7. Afacsimile recorder as claimed in claim 1 or 2, characterized in that the spot elements are electroluminescent elements.

8. Afacsimile recorder substantially as described with reference to the accompanying drawings.