GB1577220A

GB1577220A - Facsimile recording apparatus

Info

Publication number: GB1577220A
Application number: GB5254376A
Authority: GB
Original assignee: Agfa Gevaert AG
Current assignee: Agfa Gevaert AG
Priority date: 1975-12-19
Filing date: 1976-12-16
Publication date: 1980-10-22
Also published as: FR2336013B3; DE2557254A1; FR2336013A1

Description

(54) FACSIMILE RECORDING APPARATUS (71) We, AGFA-GEVAERT AKTIENGESELLSCHAFT, a body corporate organised according to the laws of Germany, of Leverkusen, Germany, do hereby declare the invention for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement: The invention relates to facsimile recording apparatus, and especially to facsimile recording apparatus suitable for the recording of information in linear image form, in which the information contained in an original to be recorded is transmitted in the form of a plurality of electric signals, for example, in chronological sequence, which are modulated according to the required intensity of individual elemental image areas, or image points, and are transformed into light signals which are arranged to strike a light-sensitive recording carrier point by point.

In previously proposed facsimile recording apparatus, of the above mentioned type, a beam of light, for example, a modulated laser beam, is normally produced, and is modulated in accordance with the electric signals. This beam is deflected step by step or continuously by means of suitable moving optical means in such a manner that it successively exposes each point or elemental area of the line image to be registered on the recording carrier. The optical deflecting means used may be, for example, oscillating mirrors, rotating disc mirrors, or rotating helical mirrors.

Mechanically moving parts are, however, always prone to a certain amount of wear and to mechanical breakdown. In addition, the mechanical movement of the optical deflecting means mentioned above must be absolutely synchronised with the sequence of electric pulses, and this requirement, in view of the normally high registering speed of a facsimile apparatus, requires a not inconsiderable amount of mechanical and electronic complexity. Also, the reflection of the registering beam at a mirror surface always involves a certain expansion of the beam, so that either a beam of an undesirably large cross-section is incident on the recording carrier, or, alternatively, additional means must be provided to collimate the registering beam before it strikes the recording car river.

An object underlying the invention is to avoid the above-mentioned difficulties and disadvantages associated with moving mechanical optical deflectors, by seeking to provide a facsimile recording apparatus having a very simple mechanical construction and to thereby enhance the chances of it having a high degree of operational reliability.

The invention provides a facsimile recording apparatus for recording information in the form of an image, which apparatus comprises means for providing in operation polarised light, a light-sensitive recording carrier in the path of light from the means for providing polarised light, an element located in the optical path between the means for providing polarised light and the recording carrier, which element comprises material that is capable of rotating the plane of polarisation of polarised light transmitted through it when that material is activated by subjecting it to an electric field, the element comprising a plurality of individually activatable portions, a polarising filter in the optical path between the element and the recording carrier, the arrangement being such that, in operation, the proportion of the polarised light that is transmitted by the filter depends on whether or not the element is activated, and means for transmitting each one of a plurality of electrical signals, each corresponding to a particular elemental image area to be recorded, to a different individually activatable portion so that the spatial pattern of activation of the element corresponds to the image to be formed on the recording carrier.

The term "electro-optically activatable" is used herein to describe a material which is capable of rotating the planer of polarisation of polarised light transmitted through it when that material is activated by subjecting it to an electric field.

Preferably, the apparatus comprises a further polarising filter located in the optical path between a light source and the element, which further filter produces the polarised light that, in operation, is incident upon the element. In that preferred apparatus, the light from the light source is polarised in the further polarising filter in a specific plane. By selective application of an electric field to individual very small areas of the electro-optically activatable material, these individual areas become active, that is, they rotate the plane of polarisation of the incident polarised light. The first-mentioned polarising filter is then optically permeable either to all those rays of the light beam which have been rotated in their planes of polarisation, or to all those which have not been rotated in their planes of polarisation, depending on the orientation of that first mentioned polarising filter with respect to the further polarising filter, it being optically impermeable to the nonrotated or rotated rays respectively in each case.

In this manner, very small areas of the filter arrangement, which correspond to the individual image points or elemental image areas to be recorded, can be made optically transparent, and the light-sensitive recording carrier is hence exposed point by point. The individual points of an image, which will, in general, be of linear form, may be either successively or, alternatively, simultaneously exposed. The desired degree of exposure of the individual image points or elemental areas can be achieved either by variation of the duration of exposure or by variation of the intensity of the exposuring light; this latter may be achieved, for example, by producing a variation of the electric field strength in each individually electro-optically activatable portion according to the required intensity of its corresponding recorded image point or elemental image area.

The apparatus of the invention has a particularly compact design, and no mechanically moving parts are needed. In addition, the apparatus can have an especially high registering speed, particularly in the case where all the image points of one line are registered and recorded simultaneously.

Advantageously, in the case of the preferred apparatus described above, the electrooptically activatable element comprises transparent ferroelectric ceramic material, preferably lanthanum-doped lead zirconate-titanate (PLZT).

It is especially advantageous if the axes of polarisation of the two polarising filters are substantially perpendicular to one another. This filter arrangement is normally impermeable to slight, with the result that only those rays of light having rotated planes of polarisation can pass through the filter arrangement. With this particular arrangement, only the required optical window portions of the electrooptically activatable element/filter arrangement must be activated; in the case of non-activation of any portion of the element the arrangement is non-transmitting in such regions.

Apparatus constructed in accordance with the invention will now be described, by way of example, with reference to the accompanying drawing, in which the single figure shows a semischematic representation of a facsimile recording apparatus.

With reference to the drawing, light from a lamp 1, which is powered by constant direct cur rent, is focussed through a cylinder lens 2 onto a narrow strip of a copying drum 3 having a photoconductive coating. The drum 3 forms part of a photo electric copying station (not shown in entirety). A short distance in front of the copying drum 3 are arranged two polarising filters 4 and 5, respectively, the axes of polarisation of which are mutually perpendicular and also perpendicular to the exposure ray path between the lamp 1 and the drum 3. Between the two polarising filters 4 and 5 is located a transparent ceramic element 6 made of lanthanumdoped lead zirconate-titanate (PLZT). The element 6 has attached to it, adjacent its upper edge, a plurality of electrodes 6a, each of which is connected to an electrical connection or lead.

The other ends of the leads 7 are connected to a shift register 10. A counter-electrode 6b, extending along the complete width of the element 6, adjacent its lower edge and in opposed relationship to the upper electrodes 6a, is earthed via a lead 8. By applying an electric voltage to any of the upper electrodes 6a, an electric field is established across the element 6 between that upper electrode and the counter-electrode 6b.

The operation of the above described apparatus is as follows: When there is no electric field across the element 6, light from the lamp 1, focussed by means of the cylinder lens 2, is polarised in one plane by the polarising filter 4, passes substantially unchanged through the element 6, and is incident on the second polarising filter 5. This light cannot be transmitted through the polarising filter 5 since the plane of polarisation of the light is perpendicular to its axis of polarisation. Thus no light is incident on the photosensitive, cylindrical surface of the copying drum 3.

Electric signals, each corresponding to the brightness of an individual image point, or elemental area of a line image to be registered on the copying drum 3, are fed in suitable form via a lead 9 to the shift register 10, and this results in the successive energisation of the leads 7. In passing along the leads 7, the signals are amplified in amplifying elements 11 before they reach the electrodes 6a, and each amplified signal, on arrival at its respective electrode 6a, creates a local electric field across the element 6, the intensity of this field corresponding to the intensity of the elemental image area to be recorded on that portion of the surface of the drum 3 directly behind the area of the element 6 in which the field is present.

These local electric fields cause corresponding local optical activation of the element 6, with the result that the plane of polarisation of the light penetrating these activated areas is rotated to an extent dependant on the degree of optical activation of each area. The polarising filter 5 transmits the light having a rotated plane of polarisation, so that for each activated area of the element 6, a narrow light beam, the intensity of which is dependent on the degree of activation of that area, strikes the recording carrier 3, and an image point, or elemental image area, is registered thereon.

Hence, by energising each of the electrodes 6a in turn in the manner described above, the entire image line to be registered is recorded on the drum 3, each of the local electric fields formed between the individual electrodes 6a and the counter-electrode 6b corresponding to one image point.

Subsequently, the copying drum may be rotated, in a known manner, over the space of one image line so that it is ready to record a further line image to be registered.

WHAT WE CLAIM IS: 1. Facsimile recording apparatus for recording information in the form of an image, which apparatus comprises means for providing in operation polarised light, a light-sensitive recording carrier in the path of light from the means for providing polarised light, an element located in the optical path between the means for providing polarised light and the recording carrier, which element comprises material that is capable of rotating the plane of polarisation of polarised light transmitted through it when that material is activated by subjecting it to an electric field, the element comprising a plurality of individually activatable portions, a polarising filter in the optical path between the element and the recording carrier, the arrangement being such that, in operation, the proportion of the polarised light that is transmitted by the filter depends on whether or not the element is activated, and means for transmitting each one of a plurality of electrical signals, each corresponding to a particular elemental image area to be recorded, to a different individually activatable portion so that the spatial pattern of activation of the element corresponds to the image to be formed on the recording carrier.

2. Apparatus as claimed in claim 1, wherein the means for providing polarised light comprises a further polarising filter located in the optical path between a light source and the element, which further filter produces the polarised light that, in operation, is incident upon the element.

3. Apparatus as claimed in claim 2, wherein the axes of polarisation of the two polarising filters are crossed at right angles with respect to each other.

4. Apparatus as claimed in any one of claims 1 to 3, wherein the element comprises transparent ferroelectric ceramic material.

5. Apparatus as claimed in claim 4, wherein the transparent ferroelectric ceramic material comprises lanthanum-doped lead zirconate titanate.

6. Apparatus as claimed in any one of claims 1 to 5, wherein the element is elongate with the individually activatable portions arranged in sequence along it, and there is provided projection means arranged to project a strip of light onto the element so that the image recorded on the recording carrier is of a linear or strip-like configuration.

7. Apparatus as claimed in claim 6, wherein the recording carrier comprises a rotatable drum having a light-sensitive surface, the linear image being formed, in operation, on a strip of the curved surface parallel to the axis of the drum.

8. Apparatus as claimed in claim 7, wherein the curved outer surface of the drum is made from photo-conducting material and the apparatus includes photo-electric copying apparatus, of which the drum forms part.

9. Apparatus as claimed in any one of claims 1 to 8, wherein the individually activatable portions of the element are so arranged that they can be sequentially activated by the signals transmitted from the transmitting means.

10. Apparatus as claimed in any one of claims 1 to 9, wherein the individually activatable portions of the element are so arranged that they can be simultaneously activated by the signals transmitted from the transmitting means.

11. Apparatus as claimed in any one of claims 1 to 10, wherein the element has a first electrode extending substantially the length of one edge, and a plurality of further electrodes, each extending over a portion of the length of the opposing edge, each of the further electrodes being connected to the transmitting means and arranged to receive a signal corresponding to the intensity of the elemental image area of the image to be formed on that portion of the recording carrier directly behind the area defined between that further electrode and the first electrode.

12. Facsimile recording apparatus substantially as hereinbefore described with reference to the accompanying drawing.

**WARNING** end of DESC field may overlap start of CLMS **.

Claims

**WARNING** start of CLMS field may overlap end of DESC **. intensity of the elemental image area to be recorded on that portion of the surface of the drum 3 directly behind the area of the element 6 in which the field is present. These local electric fields cause corresponding local optical activation of the element 6, with the result that the plane of polarisation of the light penetrating these activated areas is rotated to an extent dependant on the degree of optical activation of each area. The polarising filter 5 transmits the light having a rotated plane of polarisation, so that for each activated area of the element 6, a narrow light beam, the intensity of which is dependent on the degree of activation of that area, strikes the recording carrier 3, and an image point, or elemental image area, is registered thereon. Hence, by energising each of the electrodes 6a in turn in the manner described above, the entire image line to be registered is recorded on the drum 3, each of the local electric fields formed between the individual electrodes 6a and the counter-electrode 6b corresponding to one image point. Subsequently, the copying drum may be rotated, in a known manner, over the space of one image line so that it is ready to record a further line image to be registered. WHAT WE CLAIM IS:

1. Facsimile recording apparatus for recording information in the form of an image, which apparatus comprises means for providing in operation polarised light, a light-sensitive recording carrier in the path of light from the means for providing polarised light, an element located in the optical path between the means for providing polarised light and the recording carrier, which element comprises material that is capable of rotating the plane of polarisation of polarised light transmitted through it when that material is activated by subjecting it to an electric field, the element comprising a plurality of individually activatable portions, a polarising filter in the optical path between the element and the recording carrier, the arrangement being such that, in operation, the proportion of the polarised light that is transmitted by the filter depends on whether or not the element is activated, and means for transmitting each one of a plurality of electrical signals, each corresponding to a particular elemental image area to be recorded, to a different individually activatable portion so that the spatial pattern of activation of the element corresponds to the image to be formed on the recording carrier.