GB1604885A - Image pickup arrangement wiht means for controlling electron flow therein - Google Patents

Description

(54) AN IMAGE PICK-UP ARRANGEMENT WITH MEANS FOR CONTROLLING ELECTRON FLOW THEREIN (71) We, SIEMENS AKTIENGESELLSCHAFT, a German Company, of Berlin and Munich, 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: This invention relates to image-pick up arrangements.

According to the present invention there is provided an image pick up arrangement comprising: an evacuated vessel containing a photocathode for emission of electrons, and an anode; an anode circuit comprising impedance means; means for detecting a voltage drop across said impedance means, which voltage drop is a function of the current of electrons flowing from the photo-cathode to the anode; and means for controlling electron flow between the photo-cathode and the anode, which means comprises at least one matrix element defining a plurality of sets of electron permeable channels, "a set of channels" being as hereinafter defined, and a plurality of sets of electrodes, each set of electrodes comprising first, second and third elongate electrodes, the longitudinal directions of elongation of all these electrodes being mutually substantially parallel, and wherein the electrodes are arranged to control the passage of electrons through a respective one of said sets of channels in response to electrical signals applied to the electrodes and are spaced in the direction of electron flow: all of the first electrodes being disposed in a first plane and being interconnected to form first groups the electrodes of each of which are commonly energisable independently of the other first groups, and are spaced from one another by a plurality of electrodes of the other first groups, all of the second electrodes being disposed in a second plane and being interconnected to form second groups, the electrodes within each respective second group being adjacent to one another and not spaced from one another by any electrodes of the other second groups, and the electrodes of each second group being commonly energisable independently of the other second groups, all of the third electrodes being disposed in a third plane and being interconnected to form third groups, the electrodes within each respective third group being adjacent to one another and not spaced from one another by any electrodes of the other third groups, and the electrodes of each third group being commonly energisable independently of the other third groups; and the arrangement being such that the common energisation of any one of said first groups, together with any one of said second groups, and any one of said third groups, energises a unique one of said set of electrodes to allow electrons from the photo-cathode to selectively pass to the anode.

Preferably, the arrangement comprises further sets of electrodes arranged and interconnected in a corresponding manner to said plurality of sets, for controlling the passage of electrons through respective different sets of said channels, in such a manner that individual channels can be controlled.

It will be appreciated that with a preferred pick-up device embodying the invention, static or variable picture information can be converted, by dot-wise scanning of an image transmitted by an optical system, into electronic signals that can then be transmitted by a telecómmunications technique, and that, since the scanning of the image dots takes place, not by means of a concentrated electron beam, but by means of a matrix arrangement of electrodes between the photo-cathode and the anode, such a pick-up device can be constructed in flat form. An arrangement according to this preferred embodiment can have a relatively short electron path in the channels, compared to that in conventional arrangements (e.g. those described in IEEE Transact. on Electron Devices, Vol.ED-20, No.11, Nov.73, pages 1052 to 1061).

Preferably, the number of first groups of commonly energisable first electrodes is equal to the number of second groups of commonly energisable second e ectrodes, and the number of third groups of commonly energisable third electrodes.

Each set of electrodes may further comprise fourth or more electrodes spaced from said first to third electrodes, all of said fourth or more electrodes being correspondingly arranged in fourth or more groups, and said common energisation including energisation of any one of said fourth groups and any one of said more groups.

Preferably, the number of first groups of first electrodes is equal to E/ , where Z is the number of said plurality of sets of channels, and E is the number of spaced electrodes in each set.

Photo-cathodes which emit electrons when excited by electromagnetic waves of wavelength in the visible range may be used, or alternatively those which emit electrons when excited by electromagnetic waves in the non-visible range.

A particular advantage of such an arrangement resides in that it may also be used to reproduce received images.

In one embodiment of the invention, the electrodes are provided for both row and column control and are disposed on a single perforated matrix. This is formed on respective faces with grooves which extend in the direction of the rows and columns respectively and in which the electrodes are disposed. The grooves in respective faces extend parallel to one another, and the grooves in one face, in which the control electrodes for the row scanning are disposed, for example, extend at right angles to the grooves in the other face of the matrix, in which the electrodes for the column control are accommodated. The grooves extend into the matrix to such a distance in each face that their crossing points form respective holes, which constitute channels, for the flow of the electrons from the photo-cathode in the direction of the anode.

The term "set of channels" is intended to cover the case of a set having only one channel.

For a better understanding of the present invention, and to show how the same may be carried into effect, reference will now be made, by way of example, to the accompanying drawings, in which: Figure 1 diagrammatically illustrates features of an image pick-up device though the electrode arrangement is not in accordance with the invention, Figure 2 is a section through one embodiment of an image pick-up device having an electrode arrangement according to the invention; Figure 3 indicates the terminal connections of electrodes suitable for row scanning with decimal-coded control signals in a device according to Figure 2 Figure 4 illustrates control signals pertaining to the device of Figure 2; and Figure 5 is a diagrammatic perspective illustration of a particular form of image pick-up device, although this is not in accordance with the present invention.

Figure 1 shows a photo-cathode 2 and an anode 4 associated therewith, between which are disposed two perforated parts 6 and 8 of a matrix. Each part 6 and 8 is formed with holes or channels, permeable to an electron stream. The holes are arranged in a plurality of sets, in the illustrated case these sets being horizontal rows and vertical columns.

A unidirectional voltage UA of, for example, 1 KV is applied between the cathode and the anode in series with an electronic component element, which is shown in Figure 1 as a load resistance 10 and from which picture information can be taken as a signal train.

The matrix part 6 has first electrodes 12 and second electrodes 13, disposed on respective faces. Electrodes 12 and 13 are consequently situated in spaced planes.

Each of these electrodes serve to control a set of holes, ie a row. Thus, holes of an upper row (or set) denoted by reference numeral 16, are controlled by a set of electrodes which consists of the upper first electrode 12, and the upper second electrode 13. Likewise, the perforated matrix part 8 is provided with electrodes 20 and 21 for the column control. In figure 1 the holes of the first column are denoted by 19. The picture information indicated in the figure by an arrow 24 is applied to the cathode 2 of the pick-up device by way of an optical system 26 which is shown as a condenser lens and by way of a glass front wall 28 of the device. The cathode is scanned by the control of the electrodes of the matrix 6 and 8 and picture information is taken from the load resistance 10 as a train of signals corresponding to the brightness distribution of the image on the cathode 2.

In the form of construction of the pick-up device according to Figure 2, a common perforated matrix 7 is provided between the cathode 2 and the anode 4. The control electrodes for the row and column control respectively are disposed in three different planes denoted by I to III, and IV to VI respectively. Sets of first and second elec trodes 12 and 13 for row control, which sets further include third electrodes 14 in the third plane III, are disposed on horizontally extending ribs 32 in the various planes I to III in line with one another in the direction of the electron beam current. Thus, each set of row electrodes comprises one first electrode 12, one second electrode 13, and one third electrode 14, which electrodes are all associated with the same row (set) of holes (channels) in the matrix 7.

Likewise, sets of electrodes 20 and 21 for column control, which sets further include electrodes 22 in the plane VI, are disposed on ribs 34 of the matrix, which are disposed vertically and in juxtaposition to one another in the direction of the electron beam current. The picture information supplied through the optical system 26 is applied to the load resistance 10 by the control of the electrodes in the planes I to III for the rows of holes in the matrix 7 and by the control of the columns by means of the electrodes in the planes IV to VI.

The electrodes in the planes I to III ensure that only the holes of one row in the matrix 7 at a time, are enabled to pass the electron beam current, and the vertically disposed electrodes in the planes IV to VI ensure that the stream of electrons only passes successively through one hole of this row at a time. Consequently only one point of the anode 2 is scanned at a time for supplying the picture information.

When images varying as a function of time, e.g. television type images, are to be transmitted, the scanning must take place so rapidly that at least about 25 individual images can be successively picked up per second. This means that, with an image split up into the usual 625 lines, the dots of one line must always be scanned within 64 llsec.

The arrangement of the electrodes 12 to 14 and 20 to 22 in separate planes allows row wise advance of the electron streams associated with individual dots of an image, in succession to one another, the electron streams passing each through one hole of the matrix 7, or through the holes of various matrices (of the form of matrices 6 and 8 shown in Fig 1) associated with the same electron stream. Corresponding control signals may be coded in accordance with a logic notation system. Either the decimal system or the binary system may be employed, or any other numerical system.

Any image dot on the image area of the cathode 2 can be selected using a small number of control elements. Figure 3 shows all of the first electrodes 12 of the plane I (for row control) interconnected in first groups al to ki, each of which is provided with a common connecting conductor.

These first groups are controlled by the first decade of a decimal coded pulse train.

Group al connects that electrode of the top row which, with the corresponding electrodes of the further planes II and III, is enclosed in the figure by a dash-dotted border, to the eleventh, twenty-first and thirty-first electrodes and so on. Group b1 connects the electrodes of the second row and of the twelfth, twenty-second, and so on. The further groups up to kl are correspondingly connected. The electrodes of the plane I are thus combined to form ten first groups and are controlled by the first decade of the decimal code. In the second plane II, all of the second electrodes 13 are interconnected in second groups, of which only the first three a2 to c2 and tenth k2 are indicated in the figure. These second groups each consist of the electrodes of ten successive rows. The second electrode plane II thus also contains ten second groups which can be controlled by the second decade of the code. The third electrodes 14 in the third plane III are also interconnected to form ten third groups, each connecting one-hundred adjacent electrodes together. Of these third groups, only a part of one group a3 is shown, and only three of the next group b3 are indicated, for the sake of simplicity. The third groups are controlled by the third decade of the code.

Likewise, electrodes may also be correspondingly disposed in further planes, and interconnected in fourth or more groups, the number of adjacent electrodes in each group. increasing tenfold in each successive plane.

The column electrodes are similarly disposed in the planes IV to VI and are also divided into groups and controlled groupwise in each instance.

Control inputs may be connected between two voltage levels U1 and U2 with respect to the cathode 2, one voltage level U1 making the associated matrix holes conductive for the electrons, while the other voltage level U2 makes the holes non-conductive. In Figure 4,-the control voltages U are plotted against the time t. At the time tl, for example, the electrodes 12 of first group al in plane I receive a control pulse which turns on the respective electrodes. Simultaneously with this control pulse Uai, a control pulse Ua2 is applied to the second electrode group a2 of the plane II. In addition, at the time tl, there is also applied to the electrodes of the third group a3 in the plane III a control pulse Ua3, which may also be initiated, for example, by the control pulse Ural. At the time tl, therefore, only the row electrodes of the first matrix row in all the electrode planes I to III is provided with a potential suitable to allow the associated holes of this row to pass the electron stream. It will be noted that, although in the planes II and III, the electrodes of other, succeeding, rows also receive control pulses, for example up to the tenth electrode in plane II anup up to the hundredth row in plane III, the associated matrix holes of these succeeding rows cannot pass the electron stream as the associated electrodes of plane I are nonconducting. Thus, common energisation of the groups al, a2 and a3 energises a unique one of the sets of row electrodes, namely, the upper set of electrodes 12, 13 and 14 in Figure 2.

At the time t2, the control pulse Uai is blocked and the next group bl of the first electrodes 12 in the plane I receives a control pulse Ubl, which makes the holes of this row conductive, since the corresponding electrodes of the same row in the electrode planes II and III also still have a pass pulse.

Likewise, at the time t3, the electrodes of the next group cl receive a control pulse Uci, whereby the third row is rendered conductive. Similar at each of the instants t4 to tlo, the succeeding row is controlled by one of the control pulses Ud, to Ukl. At the time tll, the initial first group al receives a further control pulse Uai, which also initiates a control pulse Ub2 for the next group b2 of the second electrodes 13 of the plane II. This control pulse Ubl for the next group of the second electrodes in the plane II lasts, like the control pulse Ua2, until the passage of the control pulses for the electrode groups al to kl of the electrode plane I. The associated third electrodes of the plane III still have their pass pulse Ua3, which lasts until the tenth passage of the set of control pulses for the electrode groups of the plane I. In this system, for example, one-thousand rows can be successively turned on. The same system may be used for the control of the columns.

The image pick-up arrangement is accommodated in a flat, gas-tight glass vessel which is exhausted to at least 10 3mm.Hg. A constant anode voltage of at least 30 V is applied between the photocathode and the anode. In some cases the voltage may be up to a number of kV, though it is preferably about 1 kV. The electrons emitted from the cathode surface as a result of its exposure to light are accelerated towards the anode by this anode voltage. The photo-cathode may be exposed to light through an objective lens or directly by application of an image, for example of a transparency. The dense distribution of the flow of electrons emitted from the cathode surface corresponds to the brightness distribution of the image on the photocathode.

If it is ensured that not all the electrons emitted from the cathode simultaneously reach the anode, but only electrons of a limited zone of the cathode surface, more particularly of a substantially punctiform electrode zone (image dot) the voltage drop across the load resistance in the anode circuit is proportional to the brightness of the dot on the cathode. If the whole cathode area is thus scanned dot-by-dot, an image signal is set up at the load resistance as an alternating voltage by which a transmitter can be modulated.

For the scanning, the electrodes are so controlled that the perforated matrix arrangement allows the passage of the electrons only at one desired dot at a time, and prevents it at all other dots. The receiver is also synchronised with the frequency of the scanning signals.

A favourable grouping of the control electrodes 12 to 14 and 20 to 22 is obtained by application of the equation: Z = nE, where Z is the total number of rows (or columns), E the number of electrode planes, and n gives the number of electrode groups of one plane and also corresponds to the base of the digital notation system by which the control is coded. Consequently, for example, one thousand rows containing electrodes in three planes may be controlled by a ten-place decimal code.

An image pick up device as described above may also be suitable for application to the conventional interlaced scanning method used in television, in which all the odd lines are scanned first and then all the even lines.

For colour images, the device may be constructed, as in colour cameras using electron beam scanning, either as a threetube system with a prism divider or as a single tube system with a strip filter.

A device as described above can also be used for image reproduction if the photocathode 2 is irradiated by homogenous light, the control electrodes are driven by a received image signal and the anode 4 is additionally fluorescent.

Such an image pick-up device may also be used as a receiver for telemetric transmission of analogue quantities. A receiver which is not in accordance with the invention is shown in Fig 5 and including a single matrix 7 disposed between the anode 4 and the cathode 2 is sufficient-as illustrated in Figure 5. This matrix picks up the image information by successive rows and only has column electrodes 23. The control of this device is thereby correspondingly simplified, because the image dots need then only be scanned in one dimension. In this way, for example, the position of a pointer may be detected on an analogue basis and be indicated at the reception end as a luminous bar.

WHAT WE CLAIM IS: 1. An image pick up arrangement comprising: an evacuated vessel containing a photocathode for emission of electrons, and an

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

Claims (9)

**WARNING** start of CLMS field may overlap end of DESC **. also receive control pulses, for example up to the tenth electrode in plane II anup up to the hundredth row in plane III, the associated matrix holes of these succeeding rows cannot pass the electron stream as the associated electrodes of plane I are nonconducting. Thus, common energisation of the groups al, a2 and a3 energises a unique one of the sets of row electrodes, namely, the upper set of electrodes 12, 13 and 14 in Figure 2. At the time t2, the control pulse Uai is blocked and the next group bl of the first electrodes 12 in the plane I receives a control pulse Ubl, which makes the holes of this row conductive, since the corresponding electrodes of the same row in the electrode planes II and III also still have a pass pulse. Likewise, at the time t3, the electrodes of the next group cl receive a control pulse Uci, whereby the third row is rendered conductive. Similar at each of the instants t4 to tlo, the succeeding row is controlled by one of the control pulses Ud, to Ukl. At the time tll, the initial first group al receives a further control pulse Uai, which also initiates a control pulse Ub2 for the next group b2 of the second electrodes 13 of the plane II. This control pulse Ubl for the next group of the second electrodes in the plane II lasts, like the control pulse Ua2, until the passage of the control pulses for the electrode groups al to kl of the electrode plane I. The associated third electrodes of the plane III still have their pass pulse Ua3, which lasts until the tenth passage of the set of control pulses for the electrode groups of the plane I. In this system, for example, one-thousand rows can be successively turned on. The same system may be used for the control of the columns. The image pick-up arrangement is accommodated in a flat, gas-tight glass vessel which is exhausted to at least 10 3mm.Hg. A constant anode voltage of at least 30 V is applied between the photocathode and the anode. In some cases the voltage may be up to a number of kV, though it is preferably about 1 kV. The electrons emitted from the cathode surface as a result of its exposure to light are accelerated towards the anode by this anode voltage. The photo-cathode may be exposed to light through an objective lens or directly by application of an image, for example of a transparency. The dense distribution of the flow of electrons emitted from the cathode surface corresponds to the brightness distribution of the image on the photocathode. If it is ensured that not all the electrons emitted from the cathode simultaneously reach the anode, but only electrons of a limited zone of the cathode surface, more particularly of a substantially punctiform electrode zone (image dot) the voltage drop across the load resistance in the anode circuit is proportional to the brightness of the dot on the cathode. If the whole cathode area is thus scanned dot-by-dot, an image signal is set up at the load resistance as an alternating voltage by which a transmitter can be modulated. For the scanning, the electrodes are so controlled that the perforated matrix arrangement allows the passage of the electrons only at one desired dot at a time, and prevents it at all other dots. The receiver is also synchronised with the frequency of the scanning signals. A favourable grouping of the control electrodes 12 to 14 and 20 to 22 is obtained by application of the equation: Z = nE, where Z is the total number of rows (or columns), E the number of electrode planes, and n gives the number of electrode groups of one plane and also corresponds to the base of the digital notation system by which the control is coded. Consequently, for example, one thousand rows containing electrodes in three planes may be controlled by a ten-place decimal code. An image pick up device as described above may also be suitable for application to the conventional interlaced scanning method used in television, in which all the odd lines are scanned first and then all the even lines. For colour images, the device may be constructed, as in colour cameras using electron beam scanning, either as a threetube system with a prism divider or as a single tube system with a strip filter. A device as described above can also be used for image reproduction if the photocathode 2 is irradiated by homogenous light, the control electrodes are driven by a received image signal and the anode 4 is additionally fluorescent. Such an image pick-up device may also be used as a receiver for telemetric transmission of analogue quantities. A receiver which is not in accordance with the invention is shown in Fig 5 and including a single matrix 7 disposed between the anode 4 and the cathode 2 is sufficient-as illustrated in Figure 5. This matrix picks up the image information by successive rows and only has column electrodes 23. The control of this device is thereby correspondingly simplified, because the image dots need then only be scanned in one dimension. In this way, for example, the position of a pointer may be detected on an analogue basis and be indicated at the reception end as a luminous bar. WHAT WE CLAIM IS:

1. An image pick up arrangement comprising: an evacuated vessel containing a photocathode for emission of electrons, and an

anode; an anode circuit comprising impedance means; means for detecting a voltage drop across said impedance means, which voltage drop is a function of the current of electrons flowing from the photo-cathode to the anode; and means for controlling electron flow between the photo-cathode and the anode, which means comprises at least one matrix element defining a plurality of sets of electron permeable channels, "a set of channels" being as hereinbefore defined, and a plurality of sets of electrodes, each set of electrodes comprising first, second and third elongate electrodes, the longitudinal directions of elongation of all of these electrodes being mutually substantially parallel, and wherein the electrodes are arranged to control the passage of electrons through a respective one of said sets of channels in response to electrical signals applied to the electrodes and are spaced in the direction of electron flow: all of the first electrodes being disposed in a first plane and being interconnected to form first groups the electrodes of each of which are commonly energisable independently of the other first groups and are spaced from one another by a plurality of electrodes of the other first groups, all of the second electrodes being disposed in a second plane and being interconnected to form second groups, the electrodes within each respective second group being adjacent to one another and not spaced from one another by any electrodes of the other second groups, and the electrodes of each second group being commonly energisable indepedently of the other second groups, all of the third electrodes being disposed in a third plane and being interconnected to form third groups, the electrodes within each respective third group being adjacent to one another and not spaced from one another by any electrodes of the other third groups, and the electrodes of each third group being commonly energisable independently of the other third groups; and the arrangement being such that the common energisation of any one of said first groups, together with any one of said second groups, and any one of said third groups, energises a unique one of said sets of electrodes to allow electrons from the photo-cathode to selectively pass to the anode.

2. An arrangement according to claim 1, wherein each set of electrodes further comprises fourth or more electrodes spaced from said first to third electrodes, all of said fourth or more electrodes are disposed in respective planes and are correspondingly arranged in fourth or more groups, and said common energisation includes energisation of any one of said fourth groups and any one of said more groups.

3. An arrangement according to claims 1 or 2, wherein each said group comprises the same number of electrodes.

4. An arrangement according to any preceding claim, wherein the number of first groups is equal to the number of second, third, fourth or more groups.

5. An arrangement according to claim 4, wherein the number of first groups of electrodes is substantially equal to E Z, where Z is the number of sets of channels, and E is the number of spaced electrode planes in each set of electrodes.

6. An arrangement according to any preceding claim, comprising further sets of electrodes, interconnected in a corresponding manner to the said plurality of sets, for controlling the passage of electrons through respective different sets of said channels, in such a manner that individual channels can be controlled.

7. An arrangement according to claim 6, wherein said plurality of sets and said further sets of electrodes are arranged in row and column fashion, as are said plurality of sets and said different sets of channels.

8. An arrangement according to any preceding claim, wherein the anode is such that it is additionally usable for image display by illuminating the cathode with homogeneous light and providing the electrodes with control signals corresponding to an image to be displayed.

9. An image pick-up arrangement substantially as hereinbefore described with reference to Figures 2 and 3 of the accompanying drawings.