Scanning apparatus and method for operating the apparatus

Image scanning apparatus, such as an image pickup device with a photo cathode in a vacuum system or a flat display device with a thermal cathode, having at least one hole matrix for row and column control of the electron stream between its cathode and anode, and at least two separately controllable electrodes for controlling the rows and columns of each row of holes of the hole matrix, the electrodes being arranged in separate planes and tied together in jointly controllable groups permitting a small distance between the cathode and the anode thereby providing a flat camera or display in a television system.

BACKGROUND OF THE INVENTION 
This invention relates to scanning apparatus disposed in a vacuum system in 
general and more particularly to a flat camera or display device for use 
in television systems. 
In one known image pickup tube of a television camera, the image picked up 
by an objective lens is converted into electrical signals. The tube 
contains an image converter part which generates an electric charge image 
from the optical image, by means of a photo cathode or a semiconductor 
layer, which is stored in a storage plate of the image converter. In an 
adjacent scanning arrangement, the storage plate is scanned by an electron 
beam. The scanning beam is controlled by the same clock generator which 
also furnishes the synchronizing pulses. A load resistor is connected into 
the circuit of the scanning beam as an electronic component. The voltage 
drop of load resistor is determined by the electron current of the 
scanning beam and the video signal is taken off this resistor. Since the 
image converter and the scanning device are connected in series in the 
direction of the signal flow and a certain minimum depth is necessary for 
scanning with an analog-controlled electron beam, a flat arrangement 
cannot be obtained with this design. 
In one known display device, a thermal cathode and a hole matrix with an 
electrode arrangement for row and column control, as well as the picture 
screen, are arranged in a vacuum chamber. This display device contains 
electrodes which can be driven by binary signals and which are arranged in 
18 planes parallel to and one behind the other, for instance, for 
controlling 512.times.512 picture elements. The electrodes of the 
individual planes are separated from each other by insulating planes which 
contain holes, assigned to individual picture elements, for the electron 
stream. The electrodes comprise conducting strips arranged on the hole 
plate. They are likewise provided with holes assigned to individual 
picture elements. The electrodes of the individual planes are tied 
together in groups and are provided with common control leads. Of the 18 
electrode planes, 9 are provided for row control and 9 for column control. 
The large number of electrode planes and the insulating layers arranged 
between them produce a relatively thick control arrangement. A long path 
for the electrons which are released from the cathode and are accelerated 
in a direction toward the anode, in the canals which are formed by the 
matrix holes in tandem and are associated with the individual picture 
elements, is thus brought about (IEEE Trans. on Electron Devices, vol. 
ED-20, no. 11, Nov. 1973, pages 1052-1061). 
SUMMARY OF THE INVENTION 
It is an object of the present invention to control an image pickup or 
display apparatus arranged in a vacuum and containing a cathode as well as 
an anode by means of a simplified form of this known hole matrix 
arrangement in such a manner that it can convert picture information by 
means of digital scanning signals into an electronic signal sequence which 
can be transmitted by communications engineering means, or convert such a 
signal sequence for image reproduction. 
It is now an object of the present invention to make the control, i.e., 
scanning arrangement, of the above-described vacuum display device or a 
corresponding image pickup thinner by reducing the number of electrode 
planes and to permit, by special grouping of the electrodes, the row an 
column control of the picture elements by means of digital control pulses 
in accordance with different logical code systems. 
According to the present invention, to solve this problem, at least two 
separately controllable electrodes are provided in a control arrangement 
of the type mentioned at the outset, at least for the holes of the 
individual rows. The electrodes are arranged in separate planes parallel 
to the flat sides of at least one hole matrix. The electrodes of the first 
plane, arranged at a predetermined distance of at least three rows or 
three columns, respectively, always form a jointly controllable electrode 
group. In each of the further planes, at least three adjacent electrodes 
each form a jointly controllable group of electrodes. The highest 
controllable number of rows or columns is therefore the product of the 
number of electrode groups of the first and second plane. 
In a special embodiment of the control arrangement, in which still more 
rows can be controlled with the same number of electrode groups per plane, 
electrodes of further row groups are cyclically connected in the second 
plane, at a predetermined distance, to the corresponding control line of 
this plane and are supplemental by a third plane, in which now all 
adjacent electrodes which are assigned to a respective group cycle of the 
previous plane, can be controlled jointly. The number of jointly 
controllable electrode groups of the different planes is then preferably 
chosen the same. With each further plane, the number of controllable rows 
is increased by another power. With a given number of rows Z, the 
relationship between the number of planes E and the number of groups n per 
plane is found from the relation Z=n.sup.E. In a special embodiment of the 
control arrangement, in which the electrodes are arranged in more than two 
planes, a common hole matrix may also be provided for all electrodes. 
In display apparatus of this type, a line is keyed bright if all electrodes 
associated with it receive a control voltage with "pass" potential. It is 
keyed dark if at least one of the electrodes associated with it receives a 
control voltage with cut-off potential, for instance, -5 V relative to the 
cathode. 
The same arrangement and subdivision into groups and phases can preferably 
be provided for the electrodes for column control. 
With pickup apparatus according to the present invention, stationary or 
varying picture information can be converted, by point-by-point scanning 
of the image transmitted by an optical system, into electronic signals 
which can be transmitted by communications engineering means. As the 
picture elements are scanned by a matrix arrangement of electrodes between 
the photo cathode and the anode instead of by a focused electron beam, the 
pickup apparatus can be designed as a flat structure. The video signal is 
taken off at the load resistor, which is connected into the anode circuit 
outside the vacuum. 
Not only can photo cathodes which emit electrons through excitation of 
electromagnetic waves of the visible range of the wavelength be used, but 
also of the invisible range. 
In a further embodiment of the control arrangement, all the electrodes of 
the different row and column planes can be arranged on a single hole 
matrix, which is preferably provided with grooves which run in the 
direction of the rows or columns, respectively on both flat sides, in 
which grooves the electrodes are arranged. These grooves are then parallel 
to each other and the grooves of the one flat side, in which, for 
instance, the control electrodes for the row scan are arranged, are at 
right angles to the grooves on the other flat side of the matrix, in which 
the electrodes for the column control are accommodated. In this 
embodiment, the grooves can extend advantageously into the matrix on both 
flat sides far enough that their intersections always form a hole for the 
electron stream. 
One embodiment of an image pickup system according to the present invention 
is housed in a flat, hermetically sealed glass vessel which is evacuated 
to at least 10.sup.-3 Torr. A constant anode voltage of at least 30 V, 
which may be several kV and preferably is about 1 kV, is applied between a 
photo cathode and the anode. The electrons emitted from the cathode 
surface by illumination are accelerated by this anode voltage in a 
direction toward the anode. The photo cathode can also be illuminated via 
an objective lens or even directly by applying a picture, for instance, a 
slide. The density distribution of the current of electrons released from 
the cathode surface corresponds to the brightness distribution of the 
image on the photo cathode. 
If care is taken that all the electrons released from the cathode do not 
reach the anode at the same time, but that only electrons of a limited 
area of the cathode surface, especially of an approximately point-size 
electrode area reach it at a given time, then the voltage drop at the load 
resistor in the anode circuit is proportional to the brightness of the 
point on the cathode. Thus, if the entire cathode surface is scanned point 
by point sequentially by lines, then the video signal, which is an a-c 
voltage with which a transmittor can be modulated, is generated at the 
load resistor. 
For scanning, the electrodes are controlled so that the hole matrix is 
permeable for the electrons only at the desired point and is blocked at 
all other points. The receiver is also synchronized with the frequency of 
the scanning signals. 
In a specific embodiment of the display device in the form of a color 
television picture tube, three adjacent column electrodes are always 
associated with fluorescent coatings of the anode. These coatings are then 
chosen so that they correspond to the three primary colors; the first one 
will then have, for instance, green fluorescence, the next one blue and 
the third one red fluorescence and this association with the three primary 
colors is then repeated cyclically through each of the following three 
columns. Corresponding to the strip-shaped column electrodes, the coatings 
for the anodes can also be made in the form of stripes and their 
dimensions can be adapted to the size of the column electrodes. For 
standard television sets, the width of these stripes will be a few tenths 
of a millimeter, e.g., 0.3 mm. Besides the stripe form a dot shape is also 
possible for these coatings on the anode which serves as the picture 
screen. It is also not necessary that the holes of the matrix be round; 
they can also be made as elongated holes, for example. 
To operate this arrangement, sequential control of the individual picture 
elements in rows and columns is necessary. For sequential control of the 
rows, brightening pulses are applied sequentially in repeating control 
phases to the individual control groups of the first electrode plane. 
Simultaneously, the control groups of the second and further planes 
receive brightening pulses which last as long as the duration of a control 
phase of the respective preceding plane. 
In substance, the display device consists of a thermal cathode, a so-called 
incandescent cathode which extends on the back side of the device at least 
approximately over the entire size of the picture, and at least one 
matrix, on the flat sides of which the control electrodes are arranged in 
separate planes, as well as of a fluorescent screen as the anode. The 
entire system is accomodated in a gastight vacuum system, which may 
preferably consist of glass and is evacuated to a vacuum of at least 
10.sup.-3 Torr.

DETAILED DESCRIPTION OF THE INVENTION 
According to FIG. 1, two hole matrices 6 and 8, each of which is provided 
with holes for the electron stream, are arranged between a photo cathode 2 
and an anode 4 associated therewith. Between the cathode 2 and the anode 
4, a d-c voltage U.sub.A of, say, 1 kV is applied in series with an 
electronic component which, in the simplest embodiment of the apparatus, 
is shown as the load resistor 10 and at which video information can be 
taken off as a signal sequence. 
The matrix 6 is provided with electrodes 12 and 13, which are arranged on 
opposite ones of the respective flat sides of the matrix 6 and therefore, 
in two separate planes. These electrodes are used for controlling the 
rows, of which only the holes of the upper row are provided with a 
reference numeral 16. Similarly, the hole matrix 8 is provided with 
electrodes 20 and 21, respectively, for the column control. In the figure, 
only the holes of the first column are designated with 19. The image 
information indicated in the figure by an arrow 24 is fed via an optical 
system shown as a converging lens 26 and a front wall 28, consisting of 
glass, of a vacuum system (not shown in further detail), to the cathode 2 
of the image pickup apparatus. The cathode 2 is scanned by controlling the 
electrodes of the matrices 6 and 8 and the picture information is taken 
off at the load resistor 10 as a signal sequence which corresponds to the 
brightness distribution of the image at the cathode 2. 
In the embodiment of the image pickup apparatus according to FIG. 2, a 
common hole matrix 7 is provided between the cathode 2 and the anode 4. 
The control electrodes of hole matrix 7 for row and column control are 
arranged respectively, in groups of three different planes, I to III and 
IV to VI, respectively. The electrodes 12 and 14 for row control, with 
which further electrodes 15 are associated and form a third plane III, are 
arranged on horizontal ribs 32 in the different planes I to III one behind 
the other in the direction of the electron stream. Similarly, the 
electrodes 20 and 22, with which further electrodes 23 are associated and 
form a plane VI, are arranged on ribs 34 of the matrix 7, which are 
arranged vertically and side by side in the direction of the electron 
stream. The picture information supplied via the optical system 26 is fed, 
through the control of the electrodes in the planes I and III for the row 
of holes of the matrix 7 and through the control of the columns with the 
electrodes in the planes IV to VI, to the load resistor 10. 
The electrodes in the planes I to III always make only the holes of one row 
of the matrix 7 permeable for the electron stream, and the vertically 
arranged electrodes in the planes IV to VI insure that only one hole of 
this row is sequentially permeable for the electron stream. Therefore, 
only one point of the cathode 2 is scanned at a given time for supplying 
the picture information. 
So that television pictures, which change in time, can be transmitted, the 
scanning must be fast enough that at least 25 individual frames per second 
can be picked up sequentially. This means that if the picture is 
sub-divided in the usual manner into 625 lines, the points of a row must 
be covered within 64 usec. 
Arranging the electrodes 12 to 14 and 20 to 22 in separate planes makes it 
possible to step the electron streams assigned to the individual points of 
the picture along line by line, sequentially in one hole of the matrix or 
in several holes of the different matrices 6 and 8, which are associated 
with the same electron stream. The corresponding control signals can be 
coded in one of the logical number systems. Decimal as well as binary 
coding along with any other number system can be used. 
Any point of the picture area of the cathode 2 can be selected with a small 
number of control elements. For this purpose, the electrodes 12 of plane I 
can be tied together, according to FIG. 3, for row stepping in groups 
a.sub.1 to k.sub.1, each of which are provided with a common connecting 
lead. These groups are controlled by the first decade of a decimal code. 
To group a.sub.1, the electrode 12 of the first row, which is enclosed in 
the figure, together with the corresponding electrodes of the further 
planes II and III with a dash-dotted frame, and the eleventh, 
twenty-first, thirty-first electrode etc., are part of group a.sub.1. 
Group b.sub.1 includes the electrodes of the second row as well as the 
twelfth, twenty-second, etc., row. The further groups up to k.sub.1 are 
connected accordingly. The electrodes of plane I are thus combined in 10 
groups and are controlled by the first decade of the decimal code. In the 
second plane II, the electrodes 13 are likewise combined in groups, of 
which only the first three, a.sub.2 to c.sub.2, and the tenth, k.sub.2, 
are indicated in the figure. Each of these groups consist of the 
electrodes of ten succeeding rows. The second electrode plane II thus 
contains likewise ten groups, which can be controlled by the second decade 
of the code. The electrodes 14 in the third plane III likewise contain ten 
groups each with one hundred adjacent electrodes. For the sake of 
simplicity, only part of the first group a.sub.3 is shown and only three 
of the second group b.sub.3 are indicated. They are controlled by the 
third decade of the code. 
In a similar manner, electrodes in further planes can also be combined in 
groups, with the number of adjacent electrodes is always higher by a 
factor of 10 from plane to plane. 
Similarly, the column electrodes arranged in planes IV to VI can be divided 
into groups and controlled as a group. 
According to the diagram of FIG. 4, the control inputs can be switched 
between two voltage levels U.sub.1 and U.sub.2 relative to the cathode 2; 
the one voltage level U.sub.1 makes the associated matrix holes pass the 
electrons, while the other voltage level U.sub.2 blocks the holes. In FIG. 
4, the control voltages U are plotted as a function of the time t. At time 
t.sub.1, for instance, the electrodes of group a.sub.1 in plane I receive 
a control pulse, which makes the upper row of the electrodes 12 permeable. 
With this control pulse U.sub.a1, a control pulse U.sub.a2 is 
simultaneously transmitted for the electrode group a.sub.2 of plane II. At 
the time t.sub.1, a control pulse U.sub.a3 is fed to the electrodes of 
group a.sub.3 in plane III; this pulse U.sub.a3 can also be triggered, for 
instance, by the control pulse U.sub.a1. At the time t.sub.1, therefore, 
only the row electrodes of the first row in all electrode planes are 
provided with a potential which makes the associated holes of this row 
permeable for the electron stream. In planes II and III, a control pulse 
is also received at the time t.sub.1 by the electrodes of the following 
rows, for instance, in plane II up to the tenth electrode and in plane III 
of the electrodes 14 up to the hundredth row. The associated electrodes of 
plane I, however, are blocked. At the time t.sub.2, the control pulse 
U.sub.a1 is blocked and the second group b.sub.1 of the electrodes 12 in 
plane I receives a control pulse U.sub.b1, which makes the holes of this 
row permeable, since the corresponding electrodes of the same row in the 
electrode planes II and II still have a "pass" pulse. Similarly, the 
electrodes of group c.sub.1 receive a control pulse U.sub.c1 at time 
t.sub.3, which makes the third row permeable. In the same manner, the 
following row is controlled at the respective times t.sub.4 to t.sub.10 by 
one of the control pulses U.sub.a1 to U.sub.k1. At the time t.sub.11, 
group a.sub.1 receives a new control pulse U.sub.a1, which also triggers a 
control pulse U.sub.b2 for group b.sub.2 of the electrodes of plane II. 
This control pulse U.sub.b2 for the second group of electrodes in plane II 
lasts, like the control pulse U.sub.a2, until the control pulses for the 
electrode groups a.sub.1 to k.sub.1 of the electrode plane I have been run 
through. The associated electrodes of plane III still have their "pass" 
pulse U.sub.a3, which lasts to the tenth run of the control pulses for the 
electrode groups of plane II. In this system, one thousand rows, for 
instance, can be driven sequentially. The same system can preferably be 
used for controlling the columns. 
An advantageous grouping of the control electrodes 12 to 14 and 20 to 22 is 
obtained from Z=n.sup.E, where Z is the total number of rows, E the number 
of electrode planes and n the number of the electrode groups of a plane 
and at the same time the base of the number system, with which the control 
is coded. Thus, one hundred rows, for instance, can be controlled by a 
two-digit decimal code with electrodes in two planes. 
The image pickup apparatus according to the present invention is also 
suitable for the line interleaving system in common television, where 
first, all uneven-numbered lines and then all even-numbered lines are 
written. 
For color pickup, the apparatus can be constructed, as in conventional 
color cameras, with electron beam scanning either as a three tube system 
with a prism divider or as a single tube system with its stripe filter. It 
is a particular advantage of the apparatus according to the present 
invention that it can also be used for image reproduction. If the photo 
cathode 2 is illuminated with homogeneous light and the control electrodes 
are driven by a received video signal and the anode 4 is at the same time 
constructed as a fluorescent anode, then the device can also serve as an 
image reproduction screen. If the apparatus, so modified, is used for 
taking pictures, then the fluorescent anode can be considered as a 
monitor. 
The image pickup apparatus can also be used as a pickup for measurement 
data for telemetry transmission of analog variables. In that case it is 
sufficient if, according to FIG. 5, only a single matrix 7, which receives 
picture information with only a single row, is arranged between the anode 
2 and the cathode 4. This matrix is therefore provided only with column 
electrodes, since the picture elements then need to be scanned only in one 
dimension. A pointer reading, for instance, can then be picked up thereby 
and can be reproduced on the receiving side by a luminous bar display. 
In FIG. 6, a vacuum display device which contains a thermal cathode 2', a 
hole matrix 6 with electrodes 12 and 13 for row stepping, a further hole 
matrix 8 with electrodes 20 and 21 for column stepping, as well as an 
anode 4 is shown. The entire arrangement is to be arranged in a closed 
vacuum system, of which only the front wall 42 and the rear wall 28 are 
shown in the figure. 
The thermal cathode 2', which may perferably consist of heater wires 44, is 
arranged between the rear wall 28 and the matrix 6 and extends over the 
entire picture area. The incandescent wires 44 of the thermal cathode 2' 
run alongside the rows which are formed by the holes of the individual 
matrices. The holes 16 of the matrix 6, for instance, are to form the top 
row 30. Columns are the respective rows of holes which are arranged 
vertically one below the other. The holes 12 of the matrix 8, for 
instance, form the right hand column 31 of the matrix 8. Between the 
thermal cathode 2' and the anode 4, a constant voltage of, say, 3 kV is 
applied, which accelerates the electrons released from the cathode through 
the holes of the two matrices toward the anode and therefore, to the 
fluorescent screen of the display device. The magnitude of the anode 
voltage is chosen so that sufficient brightness on the picture screen is 
obtained. For black and white reproduction, sensitive flourescent layers 
such as, for instance, zinc oxide can be used in order to keep the anode 
voltage low. 
Since the color reproduction, 3 color components red, green and blue are 
required, three adjacent matrix points are available as a color triad for 
dot information. Therefore, the control electrodes 20 and 21 for the 
column control, which serves for stepping horizontally, form three groups 
as far as color is concerned, namely one for red, one for blue and one for 
green. One of these groups is to relate, for instance, to the first three 
columns arranged at the matrix in FIG. 6, of which the associated holes of 
the matrix 8 are provided with a dashed frame. The upper holes of the 
matrix 8, provided in the figure with a dashed frame 54 then form a color 
dot on the anode 4. In the same manner, the next holes 56 of the column 
electrodes 20 and 21 likewise form a color dot on the anode 4. For this 
purpose, the anode 4 is provided with a special overlay 38. This overlay 
may consist, for instance, of stripes which are assigned to the individual 
column electrodes 20 and 21 and of which only 3 are indicated in the 
figure and are designated as 39 to 41. These stripes are adapted to the 
columns of the matrix 8 as to shape and size. The stripes 39 to 41 are 
assigned to the groups 54 and 56 and consist of a material which 
reproduces one of the primary colors, green, blue or red, respectively, 
especially of green or blue or red phosphor. In the practical embodiment, 
the width of the stripes 39 to 41 will be, say a few tenths of a 
millimeter, for instance, about 0.3 mm. Besides being in the form of the 
stripes of the overlay 38, however, the latter may also consist of other 
geometrical structures, e.g., individual squares, rectangular or circular 
overlays. These overlays are then arranged for one color, respectively, 
one below the other, in the direction of the stripes 39 to 41. 
In the embodiment according to FIG. 6, all control electrodes are shown as 
wires. However, the electrodes can also consist of flat stripes, which can 
be prepared, for instance, by vapor deposition of conductor material on a 
respective flat side of the hole matrix in question. 
In the embodiment of the vacuum display device according to FIG. 8, which 
is of similar construction to the embodiment of FIG. 2, the thermal 
cathode 2' and the anodes are arranged, as in FIG. 6, with a special 
embodiment of a matrix 7 between the walls 42 and 28 of a vacuum system. 
The matrix 7 can consist, for instance, of a flat glass body which is 
provided on one of its flat sides with vertical slots 46 and on the 
opposite flat side with horizontal slots 48. There are formed, by the 
unremoved material of the matrix 7, ribs 34, on which electrodes 52 and 
54, respectively, in wire or strip form, which serve for column control, 
are arranged vertically and parallel to each other in such a manner that 
the electrodes 52 are situated in one plane and the electrodes 54 in a 
further plane parallel thereto. These electrode planes are arranged one 
behind the other in the direction of motion of the electrons emitted by 
the thermal cathode 2'. 
In a similar manner, there are formed on the opposite flat side of the 
matrix 7, by the unremoved parts of the slots 48, ribs 32 which are 
provided with electrodes 62 and 64, respectively. The electrodes 62 and 64 
are arranged horizontally with respect to the matrix 7 and serve for row 
control. The depth of the slots 46 and 48 can now advantageously be chosen 
so that a hole 66 is generated at each of their intersections within the 
matrix 7. These holes then serve for controlling the electron motion from 
the cathode 2' to the anode 4, which constitutes the picture screen of the 
display device. 
In the control arrangement according to FIG. 8 for a vacuum display device 
according to the present invention, the thermal cathode 2', the first 
matrix 6, the electrodes 12 and 13 for row control, the second matrix 8 
and the electrodes 20 and 21 for column control, and the anode with 4, 
corresponding to the design according to FIG. 6 are shown. A d-c voltage 
source 45 which supplies an anode voltage U.sub.A of, say, 3 kV, is 
connected between the cathode 2' and the anode 4. The row electrodes 12 
are arranged in a plane I and the row electrodes 13 in a plane II. The 
control arrangement also includes a clock generator 68 of a control unit 
69, which delivers clock pulses U.sub.T at its output. These are sent into 
a shift register 70 which is preferably designed as a ring counter and the 
stages of which are designated 71 to 74. If the display device is used for 
reproducing television pictures, the clock pulses U.sub.T can be taken 
from the video signal. The ring counter 70 controls the row electrodes 12 
in the plane I. Another shift register 80, which may preferably likewise 
be designed as a ring counter and the stages of which are designated as 81 
to 83, controls the row electrodes 13 in plane II. 
Of the row electrodes 12 in the plane I, the first, fifth and ninth, as 
seen from the top, i.e., from the first row, form an electrode group 
a.sub.1. They are provided with a common lead and are connected to the 
stage 71 of the shift register 70. 
In a similar manner, the second, sixth and tenth electrode form a further 
control group b.sub.1 ; they are provided with a common lead and are 
connected to the stage 72. The third, seventh and eleventh electrode form 
a third control group c.sub.1, which is connected to the stage 73. A 
fourth control group d.sub.1 is formed by the fourth, eighth and twelfth 
row electrode. This group is connected to the stage 74. 
In the plane II with the electrodes 13, each four successive electrodes are 
tied together to form a control group a.sub.2 and are connected to the 
stage 81 of the shift register 80. Similarly, the electrodes of the 
control group b.sub.2 are connected to the stage 82 and the third 
electrode group c.sub.2 to the stage 83. In the same manner, electrodes 
associated with further rows can be connected to the control groups in 
both planes I and II. 
If, for advancing the picture elements, the control electrodes were 
connected individually, one plane of electrodes would be sufficient for 
stepping the rows and columns, but the number of switching and control 
elements would be correspondingly high since, then, each individual 
control electrode would require an electronic switching element, for 
instance, a transistor. According to the present invention, the electrodes 
for the row, and optionally, also for the column stepping are therefore 
arranged in several planes, the electrodes of which are tied together in 
groups in a special manner. Each of the electrodes 12 and 13 can be 
switched between two voltage levels relative to the cathode 2. The one 
voltage level, for instance, zero volts, makes the holes of the matrix 6 
of the associated row passable for the electrons toward the anode 20, 
which is the fluorescent screen. The other level, for instance, -5 V, cuts 
off the electrons. 
Only if all the electrodes associated with the same picture element are 
switched to "pass" can the electrons get through the matrix hole 
associated with the picture element. 
The stepping along of the rows is accomplished by clock pulses of a control 
voltage, the period of which corresponds to the duration of the lighting 
up of a row. The clock pulses are taken from the clock generator 68 or, in 
the case of television picture reproduction, from a video signal and cause 
the shift register 70 to step its output pulses U.sub.71 to U.sub.74 along 
sequentially from stage to stage. 
In the diagram according to FIG. 9, in which the control voltage U.sub.S is 
plotted versus the time t, a clock pulse U.sub.T is to be transmitted at 
the time t.sub.o by the clock generator 68 to the first stage 71 of the 
shift register 70. This clock pulse U.sub.T triggers the shift register 70 
and the stage 71 delivers an output pulse U.sub.71, with a potential of, 
for instance, -5 V relative to the cathode, to the associated control 
group a.sub.1 of the row electrodes 8 in the plane I. This output 
U.sub.71, the length of which from t.sub.o to t.sub.1 determines, as shown 
in FIG. 10, the duration of brightness L of the upper row and is equal to 
the period T of the clock pulse U.sub.T, is simultaneously fed to the 
shift register 80 as an input signal. As shown by FIG. 14, the first stage 
81 of the shift register 80 thereupon delivers an output pulse U.sub.81, 
which is fed to the electrodes of the first control group a.sub.2 in plane 
II. The luminescence duration L of a row will be 64 usec, for instance, 
for 625 lines and 25 frames per second. The control signal set for the 
control phases of the electrodes in plane II by the shift register 80, 
however, is present until all the control groups in the plane I have been 
addressed sequentially. Between t.sub.o and t.sub.1, therfore, only the 
two control electrodes associated with the upper row carry a pass signal 
simultaneously, and only this row is therefore keyed bright. At the time 
t.sub.1, a new control signal U.sub.72 is fed from the stage 72 to the 
second control group b.sub.1 of plane I with a new clock pulse U.sub.T as 
shown on FIG. 11 since the second electrode, associated with this group of 
rows, of the control group a.sub.2 in plane II as per FIG. 14 still has a 
"pass" signal, line 2 will light up until, at the time t.sub.2, the 
electrode group c.sub.1, as shown by FIG. 12, is driven by the control 
signal U.sub.73. Similarly the stage 74 will address the associated 
control group d.sub.1 of plane I with its output signal U.sub.74 at the 
time t.sub.3 as shown by FIG. 13 with the new clock pulse U.sub.T and the 
fourth row will be lit up, as the control group a.sub.2 in plane II still 
carries a pass signal according to FIG. 14 due to its control signal 
U.sub.81. Similarly, a new control pulse U.sub.71 is fed to the associated 
electrode group a.sub.1 in plane I at the time t.sub.4, according to FIG. 
10; this control pulse simultaneously triggers the shift register 80 for 
controlling plane II. This shift register addresses, as shown by FIG. 15, 
the control group b.sub.2 with its output pulse U.sub.82. After traversing 
the row advance through the second control phase, the stage 83 of the 
shift register 80 drives the third control group c.sub.2 of the electrodes 
10 in plane II, with the control pulse U.sub.83 at the time t.sub.5 as 
shown by FIG. 16 with the next control pulse U.sub.71. 
For the customary television picture with a 625-line system, the grouping 
of the electrodes can also simply be chosen so that in the reproduction of 
the television picture, first the uneven and the even numbered lines are 
scanned. 
The column control of the device, i.e., the scanning of the picture 
elements of each row (line) can be accomplished in the same manner as the 
row control. The stepping velocity of the column control, i.e., the 
frequency of the clock voltage U.sub.T, must be chosen high enough so that 
during the lit-up time of a row, all picture elements of the row are 
driven sequentially. If the brightness of the picture screen is not 
sufficient with dot wise control, the picture information of an entire row 
can be put in temporary storage in a multistage interim register. 
Subsequently, all dot signals of a row are then fed simultaneously to the 
column electrodes in a plane, each of which is connected with one of the 
shift register outputs. 
Brightness control of the display device for television picture 
reproduction can be accomplished through a further vertically installed 
electrode plane or also by means of the electrode system already provided 
for the column control by amplitude modulating the column control pulses 
with the brightness. If the anode voltage can be kept low enough, the 
brightness can also be controlled in the anode circuit. 
The flat display device can also be used for displaying time varying 
quantities. The horizontally arranged electrode system then serves for the 
Y-deflection and the vertically arranged electrode system for the 
X-deflection. The time base can be controlled by means of one of the 
stepping methods. 
By arranging the row electrodes in 3 planes I to III as per FIG. 3, control 
of the display by decimal code is also possible as described above. 
For each decade D.sub.1 -D.sub.3 of FIG. 3, one respective shift register 
can be provided which is preferably connected as a ring counter and 
switches back to its first stage after the signal has run through it once. 
These 3 ring counters then each have 10 control stages. The electrodes of 
the first control group in plane II receive control signal which causes 
the electrodes in the respective rows to pass until the electrodes of all 
control groups of plane I are switched through sequentially. After the 
signal has run through the first 10 lines, the second control group of 
plane II receives its signal which lasts until all control groups of plane 
II have again been stepped through sequentially. From the electrodes of 
plane III, the electrodes of the first control group, which are associated 
with the electrodes of rows 1 to 100, receive a pass signal for the 
electrons until the control groups of plane I have been switched through 
sequentially 100 times in 10 control phases and a accordingly, also the 
control groups in plane II 10 times in one control phase. For brightening 
100 row electrodes of plane I, therefore only 10 signal changes are 
necessary for the electrodes of plane II and correspondingly, only a 
single signal of appropriate duration is required for the electrodes of 
plane III.