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Description  |
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TECHNICAL FIELD
The present invention relates to a system for controlling the raster-like
pictured representation of information on a data display device with
picture elements, the display area of which has a predetermined side ratio
in the x-direction and y-direction by line-by-line readout of picture
element information at a predetermined speed of readout from a picture
information storage which is addressable
picture-element-by-picture-element in the x-direction and y-direction.
BACKGROUND ART
Data display devices have a screen area which possesses a side ratio which
is usually 4:3. As the picture element resolution corresponds to this
ratio, each picture element information displayed on the screen has a
corresponding side length or expansion in x-direction and y-direction.
Thus, in the corresponding picture information storage, a true-to-picture
pattern of the picture information elements is stored. By the thus
obtained square form of the picture elements it is rendered possible to
electronically manipulate the stored content in the picture information
storage such that on the screen rotary movements of figures, for example,
can be displayed without distortion.
Information can also be displayed in the form of pictures with picture
elements which differ from the above-described standards of data display
devices, as for example, by the video text method. For this method,
picture elements are used which have a side ratio of 3:2, i.e. a
rectangular form. Then the picture information elements, when displayed on
the area of these picture elements, do not have the form of a circular dot
but of an ellipse. When, according to the video text method, a square area
is displayed, the latter does not consist of the same number of picture
information elements in x-direction as in y-direction, but of, for
example, 30 picture information elements in the x-direction and 20 in the
y-direction.
If such a video text picture is displayed on the screen of a usual data
display device, picture distortion occurs which results in the
representation of a square as a rectangle with a side ratio which
corresponds to the circular picture dots or to the display areas of the
picture elements, which have a square form due to the other kind of
scanning. This distortion has hardly any influence on the readability of
alphanumeric characters when displayed. There is, however, a falsification
of the information content in the representation of geometrical figures,
as the information will appear more depressed in the y-direction than in
the x-direction.
SUMMARY OF THE INVENTION
"An object of the present invention is" to render possible the
representation of information with picture elements of different side
ratios on a data display device such that there is no falsification.
A system of the kind initially described for achieving this objective is
designed such that for the display of information with picture elements
the side ratio of which differs from the predetermined side ratio, the
speed of readout of the respective picture element information from the
picture information storage is changed such that the picture elements
generated on the data display device are geometrically similar to the
picture elements with differing side ratio.
In accordance with the present invention, information, the display of which
is achieved using picture elements with differing side ratios, can also be
displayed on a data display device the picture elements of which have the
usual side ratio of 1:1. The information is not reproduced true-to-area
but geometrically similar, i.e. a square is reproduced as a square and a
circle is reproduced as a circle. There is a change in size of such
figures but this is of no importance and only become obvious when compared
with a screen using the same size but of another type of representation.
The invention can be applied to practically all types of differing side
ratios and can be realized with minor additional hardware expense. A
change of speed of readout of the picture information store may only be
provided for the x-direction or only for the y-direction or for both
directions, dependent on which direction the equalization is to be carried
out. The speed of readout can be decreased or increased, but in most cases
decrease is more suitable, as the resolving power of the data display
device has limits which prevent an arbitrary reduction of picture dots.
The decrease of the speed of readout for the y-direction can easily be
effected by the fact that each line of picture element information from
the picture information stored is repeatedly read out in succession. The
picture elements and consequently the picture dots are thereby elongated
in the y-direction by one or more line thicknesses.
BRIEF DESCRIPTION OF THE DRAWINGS
Advantageous embodiments of the invention, which can be applied to any
difference in side ratios of two different types of representation, will
now be described with reference to the accompanying drawings in which
FIGS. 1a and 1b are two picture elements with different side ratios,
FIG. 2 is a representation of information with picture elements of
different side ratios on the same screen,
FIGS. 3a and 3b are further picture elements with different side ratios,
FIG. 4 is a representation similar to FIG. 2 but for the practical use of
the invention,
FIG. 5 is an embodiment of a circuit according to the invention,
FIGS. 6a and 6b are schematic representations of the addressing principle
of a picture information storage when using the invention in a video text
display with a data display device,
FIG. 7 shows the addressing in the circuit according to FIG. 5 for the case
of a picture-in-picture representation,
FIG. 8 shows an addressing procedure similar to FIG. 7 but for use in an
embodiment of the invention,
FIGS. 9a and 9b each is a schematic picture-in-picture representation of a
practical use of the invention,
FIG. 10 is another embodiment of a circuit according to the invention, and
FIG. 11 is a representation of address circuits used in the circuit
arrangement of FIG. 10.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
FIG. 1a schematically shows a picture element A as it is commonly used in
data display devices for the representation of information. The picture
element A has a width Az and a height Ay. These two values are conforming
so that the picture element A is of a square form, and width and height
have a ratio of 1:1. On the square area of representation of the picture
element A an information element in form of e.g. a circular picture dot
can be displayed.
In FIG. 1b, a picture element B, indicated by a dashed line, is shown which
has a width Bx and a height By. When the width and height have a ratio of
2:3, the picture element is a picture element B which can be used for the
representation of information on a video text display device. Therein the
picture element B can be represented on the display area as e.g. an
ellipse-shaped picture dot.
Neither of the above-explained picture elements A and B of a data display
device and of a video text display device correspond in their size nor in
their side ratios.
FIG. 2 shows an enlarged section of the screen of a data display device.
This section has 16 columns of square picture elements in the x-direction
and 16 lines of picture elements in the y-direction, the square picture
elements being of the size of the picture element A as shown in FIG. 1a
and indicated by straight lines. This screen section could also accomodate
9 columns and 6 lines of such picture elements which correspond to the
picture element B as shown in FIG. 1b. This arrangement of picture
elements is indicated in FIG. 2 by dashed lines which are numbered
correspondingly.
In FIG. 2, a square with a side length Q is shown in the right-hand bottom
part of the screen section, which consists of 6 rectangularly shaped
picture elements a to f which each correspond to the picture element B of
FIG. 1b. This square would appear on a video text display device as
representation of 6 video text picture dots, i.e. as 6 information
elements. If these information elements are displayed on a data display
device, they would form a rectangle which, in the screen section in FIG.
2, consists of the square picture elements a' to f'. From the different
form of the two partial areas having 6 information elements on the screen
section it can be seen that for the display of video text information on
data display devices a video text object is reduced differently in the x-
and y-directions, i.e. it is distorted. Thus, in the representation of
video text information on data display devices, for instance squares
become rectangles, circles become ellipses, and letters appear depressed
in their height. For alphanumeric texts, this distortion in general does
not result in a negative effect on the readability. For geometrical
figures, however, a change in information is inevitable.
In order to prevent this distortion so that a true-to-area representation
of the picture information of the video text on a data display device is
achieved, an elongation of the picture elements A of the data display
device, as can be seen from FIG. 2, has to be provided in the x-direction
and in the y-direction, which corresponds to the sizes of the picture
elements A and B (FIG. 1). Furthermore, it can be seen from FIG. 2 that an
object of the video text, the top left-hand corner of which has the
x,y-address 6, 4, would appear on a data display device dislocated in the
top left-hand direction, when it would be represented with the same
address but with picture elements of a data display device.
If, in a data display device, the height of the picture elements is to be
changed in the y-direction, extensive modifications have to be carried out
which lead to a line number different from the standard. An adaptation of
the representation of a data display device to the representation on a
video text display device with the result that video text information will
be reproduced true-to-area on a data display device would cause some
difficulties.
In FIG. 3 one kind of modification of the picture element A of a data
display device is shown, by which it is rendered possible to represent
video text information on a data display device not true-to-area but
similar-to-area, i.e. there is a uniform distortion in the x-direction and
the y-direction so that only the scale but not the form of the information
to be displayed is changed. FIG. 3a shows a picture element which consists
of two picture elements A of the type shown in FIG. 1a so that width and
height have a ratio of 1:2. FIG. 3b shows a picture element A' which is a
result of the widening of the picture element of FIG. 3a and which has the
width A'x and the height A'y. The invention has as an object the display
of video text information with picture elements of this kind. As the
height A'y is double as high as the height Ay of the picture element of
FIG. 1a, the picture element A' can be produced on a data display device
by representing the respective picture dot twice on top of each other.
Consequently, the picture dots of a picture line are to be represented
twice one below the other. Then, when each picture dot is widened in
x-direction, with the information of each picture dot a picture element is
filled which corresponds to the picture element A' of FIG. 3b.
The result of such a display can be seen in FIG. 4. Also shown is a picture
section of a data display device, which has the same size as the picture
section shown in FIG. 2 and which comprises the square with the side
length Q which consists of the picture elements a to f. The top left-hand
corner of this square has the x,y-address of 6, 4 in the raster, indicated
by dashed lines, of picture elements which correspond to the picture
element B of FIG. 1b. FIG. 4 shows another square with the side length Q'
the top left-hand corner of which also has the x,y-address 6, 4 in the
raster indicated by straight lines and which consists of the picture
elements a'' to f'' which correspond to the picture element A' as shown in
FIG. 3b. The square form of the figure reproduced with these picture
elements a'' to f'' is obtained when width and height of the picture
element A' of FIG. 3b have a ratio of 2:3, as this is also required for
the picture element B of FIG. 1b. It can be readily appreciated that this
kind of ratio is obtained when there is A'x=4/3 Zx for A'y=2Ay. In
general, for the elongation of a square picture element A in the
x-direction, when there is a duplication of the height in the y-direction,
in order to form a picture element which is similar to a rectangularly
shaped picture element B with the width Bx and the height By the following
equation is employed
##EQU1##
In FIG. 4, it is shown that, in putting this principle, to practical use a
video text object is reproduced geometrically similar on a data display
device, wherein the shifting to the top left-hand direction is less than
according to FIG. 2, and a reduction in size takes place which only
becomes obvious for corresponding screen sizes but yet can be tolerated.
In FIG. 5, a circuit arrangement is shown by which it is rendered possible
to alternatively display normal data information or video text information
on a data display device. This circuit arrangement comprises a picture
information storage or memory 40 into which picture information of e.g.
the working storage of a data processing unit (not shown) can be written
via a data bus 41. This picture information which, for example, can
indicate the intensity and the color of picture elements are transferred
via a data bus 42 form the picture information storage 40 to a converter
43 which transforms the picture information in analog red-green-blue
signals for the control of a screen 44. The vertical and horizontal
synchronization circuits necessary for the pictured representation of such
information are not shown in FIG. 5 It is assumed, however, that the
picture repetition frequency and consequently the vertical and horizontal
synchronization frequency are constant, independent of the information to
be displayed.
For the addressing of the picture information storage 40 a column counter
46 and a line counter 52 are used. The column counter 46 addresses the
picture information storage 40 in the x-direction and the corresponding
address signals are supplied to the latter via an address bus 45. Via this
address bus 45, these address signals are also supplied to the two
comparators 47 and 48 which compare the respective relevant address with
predetermined values X or X'. The two comparators 47 and 48 generate an
output signal, respectively, when the relevant address corresponds to the
value X or X'. This output signal is supplied via a change-over switch 49
to the rest input R of the column counter 46, to one side of a change-over
switch 51, and to the clock input of a D-flipflop 50. By the connection of
the output signal of the comparators 47 and 48 with the reset input R of
the column counter 46, the maximum possible number of picture elements per
line is determined, in which picture information can be displayed on the
screen 44. When this maximum value is reached, column counter 46 starts
counting from the value of zero on. This counting is controlled by a
frequency f1 which is supplied to the clock input of the column counter 46
via a change-over switch 57. The change-over switch 57 as well as the
change-over switches 49 and 51 are controlled via a control signal 4 which
is supplied to these change-over switches by the data processing unit (not
shown).
The D-flipflop 50 is utilized as a factor 2-divider, since its data input
is connected with its negative output Q. The signals supplied to the clock
input of the D-flipflop occur at the other side of the change-over switch
51 with half the frequency. The change-over switch 51 is connected with
the clock input of the line counter 52 so that the latter is clocked via
the output signals of the D-flipflop 50 at the respective position of the
change-over switch 51. This means that its counter reading is increased by
the value 1 with each or each second resetting of the column counter 46,
depending on the position of the change-over switch 51. The output of the
line counter 52, as well as the output of the column counter 46, is
connected via an address bus 53 with the picture information storage 40
and two comparators 54 and 55. Thereby the picture information storage 40
is addressed in the y-direction, wherein the line counter 52 is reset each
time when comparator 54 signals the reaching of the line value Y or
comparator 55 signals the reaching of the line value Y', and this signal
is supplied to the reset input of line counter 52 via a change-over switch
56. The change-over switch 56 is also controlled via the control signal U
from the data processing unit (not shown).
In the position of the change-over switches 49, 51, 56, and 57, as shown in
FIG. 5, the content of the picture information storage 40 is represented
on the screen 44 by picture elements the raster of which corresponds to
the one of a normal data display device. Therein, the speed of readout in
the x-direction is determined by the frequency f1 and is switched over to
the next line with each resetting of the column counter 46. The last
column or line is determined by the comparators 47 and 54 which signalize
the counter reading X or Y.
When the picture information storage 40 contains picture information which
is to be represented in picture elements which differ from the size of the
picture elements of a common data display device, the change-over switches
49, 51, 56, and 57 must be put in their second position by using the
control signal U. In this position, the speed of readout is determined by
the frequency f2 which forms the ratio of 3:4 with frequency f1. This
results in a slower readout of the picture information and consequently in
the their elongation in x-direction with a factor 4/3 in contrast to the
previous representation. The speed of readout in the y-direction is
reduced by the factor 2 by means of the D-flipflop 50. As a constant value
of the horizontal and vertical synchronization of the screen 44 is taken
for granted, the picture information of one line is reproduced anew in the
next line by means of the change-over. The two comparators 48 and 55
determine the resetting of the column counter 46 and of the line counter
52 each time the counter reading X' and Y' is reached. The necessary
magnitude of these values will be described in the following with
reference to FIG. 6.
In FIG. 6a, the counting volumes of the column counter 46 (FIG. 5) and of
the line counter 52 (FIG. 5) are shown as a diagram for the case of the
representation of information on the screen 44 with square picture
elements the number of which is 820 per line and the line number is 615.
Thus, inclusive of the counter reading zero the column counter 46 is reset
when reaching the counter reading X=819 and the line counter 52 when
reaching the counter reading Y=164. The diagram shown in FIG. 6a,
consequently, does not only indicate the counting volumes in the
x-direction and the y-direction but also multiples of the clock time
t1=1/f1 in the x-direction and multiples of the clock time X.multidot.t1
of the line counter 52 in the y-direction. Furthermore, it is also
possible to interpret the diagram of FIG. 6a as a reproduction of the area
of the screen 44.
When, for the representation of information on the screen, rectangular
picture elements are to be used instead of square ones, and these
rectangular picture elements correspond to the picture element A' as shown
in FIG. 3b, and when, furthermore, this information representation
consists of video text information, the diagram of FIG. 6b is obtained
which indicates the counting volume 615 for the column counter 46 and the
counting volume 308 for the line counter 52. In the x-direction this
corresponds to a clock time t2=1/f2 and in the y-direction to a clock time
X'.multidot.t2. Then, inclusive of the counting value zero, the column
counter 46 and the line counter 52 only reach the counting value X'=614
and Y'=307, respectively. The counting volumes 615 and 308 are obtained by
the fact that the picture elements of monitor 44 are widened by the factor
4/3 in the x-direction and their height is to be duplicated in the
y-direction according to the requirements. Then the screen 44 can only
accomodate 615 picture elements in the x-direction and 308 in the
y-direction. As, however, the representation of video text information
according to standards is carried out with 480 picture dots in the
x-direction and 240 lines in the y-direction, the screen 44 of the data
display device cannot be totally used for the representation of a video
text picture. The unused area is indicated by hatches in FIG. 6b. As a
constant line synchronization control is also required for the display of
video text information on screen 44, additional 135 counting steps have to
be carried out after 480 counted picture information addresses during
scanning in the x-direction. Similar measures have also to be taken in the
y-direction for a constant picture repetition rate, wherein the line
counter 52 has to take not only 240 counting steps but also 68 additional
ones.
The diagram of FIG. 6b also corresponds to the actual picture display of
the video text object when the scanning beam of screen 44 for the
x,y-address 0, 0 of the video text picture also has the position 0, 0 in
screen 44. Otherwise the hatched section can also appear at another
position, i.e. the white display area shown in FIG. 6b then has another
location. The picture information storage 40 should also contain
predetermined information for the hatched section, e.g. a constant color
reproduction, as the readout of information during the addressing of the
picture information store 40 basically is not interrupted.
In the foregoing it was assumed that by the circuit arrangement shown in
FIG. 5 either a representation of information with picture elements A of
the kind shown in FIG. 1a or with picture elements A' of the kind shown in
FIG. 3b is to be controlled. This can be achieved without any problems by
the circuit arrangement of FIG. 5, if the filling of the whole screen
either with tone or the other kind of information is concerned. But when a
picture-in-picture representation with picture elements of different
dimension in the x- and y-directions is to be carried out, as it is shown
in FIG. 4 for the square with the side length Q' in an enlarged screen
section, by using the circuit arrangement of FIG. 5, effects can occur
which can only be avoided by increased circuitry expense. For purposes of
explanation reference is now made to FIG. 7 in which a diagram of the
chronological order of the addressing of the column counter 46 in the
x-direction is shown. The course 20 shows the increase in the counter
reading of the column counter 46 starting from zero up to the final value
X which is reached at the point of time Ts. The course 21 indicated by
dashed lines respectively show the counter reading of the column counter
46 starting from zero up to the final value X' which is also reached at
the point of time Ts. The slopes of the two courses 20 and 21 correspond
to the clocking of the column counter 46 with the frequency f1 or f2.
Subsequent to the point of time Ts the counting for the column counter 46
starts again from the counter reading zero. When one part of the screen
surface is to display information with picture elements which are broader
than the picture elements used in the other part of the screen surface,
the counting has to be delayed during the time which corresponds to the
width of the different picture section. For this time tx, a course 22 is
indicated by dot-dash lines in FIG. 7, by which it becomes obvious that
the column counter 46 is clocked more slowly during the time tx and after
the time tx reaches a lower counter reading then for a normal course 20.
Starting from this lower counting reading, the column counter 46 is then
clocked at a higher speed again. The counter reading of the column counter
46, however, according to the course 23 which is a continuation of the
line of course 22, can only reach the final reading Xe at the point of
time Ts. When the counting is continued, the column counter 46 reaches the
final reading X, which corresponds to its counting volume, but only at a
later point of time Te for which the scanning beam of the screen can
already be located in the next line. The difference X-Xe is obtained,
which has to be individually determined for the respective size of a
picture section to be represented within a larger picture from the ratio
tx:Ts in order to carry out a respective correction when the picture
information storage 40 (FIG. 5) is addressed. It is not so simple to
obtain a correction of the shifting in the x-direction to which a picture
dot P which, according to the course 20, would normally be represented at
a certain location of the screen, is subjected due to the changed course
23. Thereby, the picture dot P is displayed as incorrect picture dot P' at
a alter point of time, i.e. shifted in the x-direction. Information with a
column address which has a value greater than Xe can no longer be
displayed.
Problems similar to the kind described above also occur with regard to the
addressing of the picture information store 40 in the y-direction.
Extensive additional circuits for respective corrections become unnecessary
when two separate picture information storages for picture elements A on
the one hand and for picture elements A' on the other hand are used. When
the one picture information storage can be addressed according to the
course 20 as shown in FIG. 7 and the other picture information storage
according to the course 21 as shown in FIG. 7 in the x-direction and the
y-direction, respectively. The addressing of both picture information
storage must have the same picture repetition frequency so that a fixed
picture-in-picture representation is obtained when using two picture
information storage with separate column and line addressing. This is
easily obtained by the fact that the clock frequencies of both column
counters are derived from the same source and the final values of the
column counters comply with the requirements described with respect to
FIG. 6. It is also useful to synchronize the column counter and the line
counter of the one picture information storage with the column counter and
line counter of the other picture information storage in order to connect
the zero points of all counters fixedly with regard to time. Otherwise the
counters would always each reach the same counter reading in a
corresponding time but the absolute counter reading reached at the
respective point of time would be determined by undetermined states in the
moment when the circuit arrangement is switched on.
In FIG. 8 the course of the addressing of two picture information storages
in the x-direction is shown, which is a combination of the individual
courses 20 and 21 as already indicated in FIG. 7 so that during the time
tx a jump from the course 20 to the course 21 is obtained, which
corresponds to the section 24 of the combined curve. At the beginning of
time tx there is a change-over to this section 24 and thus from one
picture information storage to the other, and at the end of time tx there
is a change back to the first picture information storage.
A similar characteristic is also obtained for the addressing of two picture
information storages in the y-direction.
The switching over from one picture information storage to another is
carried out according to the representation of FIG. 8 at the points of
time ta and tb. As a criterion for the switch-over, the counter reading of
one of the two column or line counters can be used, as these counters
continue counting independent of the change-over. Correspondingly, e.g.
for the column counter with the counting characteristic 20, there is a
counter reading Xa or Xb, respectively, at the beginning and at the end of
the period tx. In the same manner two counter readings for the line
counters can be obtained, which define a period tx which corresponds to
the extension in y-direction of the picture section to be represented.
By the switching over in the x- and y-directions, in the representation on
the screen of a data display device a time window or an area is opened on
which a further picture can be represented with picture elements A' (FIG.
3b) within a picture with picture elements A (FIG. 1a). Such kind of
representation is shown in FIG. 9a, corresponds to the representation of
FIG. 6b, i.e. on the display are 30 of a data display device a total
picture could be represented which, e.g. is a video text picture. A
section 32 of this video text picture is only represented within the
limits determined by the described counter readings Xa, Xb, Ya, and Yb.
In FIG. 9a a further section 33 of the video text picture is indicated by
dot-dash lines. When this partial picture 33 is to be displayed at the
location of the display area 30, at which also the partial picture 32 will
be displayed, this can be obtained by a shifting of the whole video text
picture 31, as it is shown in FIG. 9b. This shifting results from
displacement of the zero points of these counters which address the
picture information storage containing the video text picture. When the
corresponding column counter is reset with a delay of Xr, the respective
first picture dot of a line is read out from the picture information
storage with the corresponding delay. At this point of time, however, the
scanning beam is at a position which corresponds to the address Sr of FIG.
9b. A corresponding shifting can be provided in the y-direction by the
amount of Yr.
In FIG. 10, a circuit arrangement is shown by which the function of FIG. 8
and 9 is enabled and which operates with two picture information storages.
Via an address data bus 61, a data processing unit 60 supplies to a first
picture information storage 62 picture information which is to be
displayed with picture elements A' (FIG. 3b). The picture information
store 62 is addressed by a column-line counter 63 in the x- and
y-directions. The clock input of the column-line counter 63 is controlled
via a clock generator 64 which supplies the clock frequency f2.
A further picture information storage 65, which is also supplied with
picture information via the address data bus 61, is provided for the
display of this picture information with picture elements A (FIG. 1a). The
picture information storage 65 is addressed by a column-line counter 66 in
the x- and y-directions, which is clocked by the clock signals of the
frequency f1 which is also supplied by the clock generator 64. Similar to
the circuit arrangement of FIG. 5, the frequencies f1 and f2 have the
ratio 4:3. Suitable frequency values are e.g. f1=50 MHz and f2=37,5 MHz.
The column-line counter 66 synchronizes the column-line counter 63 via two
outputs 67 and 68 in the x- and y-directions.
The output signals of the two picture information storages 62 and 65 are
supplied via a change-over switch 69 to a color table storage 70 which
contains a transformation table 71 or 72, respectively, for the picture
information from the picture information storage 62 or 65. Thereby the
picture information is transformed in digital values for the individual
colors red, green, and blue. These values are subsequently supplied to a
digital/analog converter circuit 73 which converts the digital values for
each color into the respective analog values. These signals are then
supplied to the display screen. Furthermore, it is also supplied with a
horizontal-vertical synchronization signal which is generated by the
column-line counter 66.
The column-line counter 66 also controls the change-over switch 69 and the
color table storage 70. The change-over has the advantage that for both
color tables 71 and 72 a common storage device and a common digital/analog
converter circuit can be used.
The setting of a picture-in-picture-window according to the principle of
FIG. 8 is carried out in the column-line counter 66 with values supplied
thereto via the address bus 61.
FIG. 11 shows an embodiment of the column-line counters 63 and 66 as given
in FIG. 10. In the top part of the figure, the column-line counter 63 is
represented and in the bottom part the column-line counter 66. The
column-line counter 63 comprises a first column counter 75 the clock input
of which is controlled by the clock signals of the frequency f2. The
output signals of the first column counter 75 are supplied to a comparator
76 as well as to the picture information storage 62. When the output
signals correspond to the predetermined counter reading X', the comparator
76 supplies a reset signal via an OR element 77 to the rest input of the
column counter 75. The OR element 77 is also triggered by the
x-synchronization signal from the column-line counter 66.
The output of the comparator 76 is connected with a D-flip-flop 78 which
functions as a factor 2-divider. The latter's negative output Q is
connected with the clock input of a first line counter 79. The latter, as
well as the column-line counter 75, is connected with a comparator 80
which, when a predetermined counter reading Y' is reached, supplies an
output signal via an OR element 81 to the reset input of the line counter
79. The output signals of the line counter 79 are also supplied to the
picture information storage 62. The OR element 81 is triggered at its
second input by the y-synchronization signal from the column-line counter
66.
The column-line counter 66 comprises a second column counter 85 to the
clock input of which the clock signals with the frequency f1 are supplied.
The output of the column counter 85 is connected with the picture
information 65 and with the first inputs of the comparators 86, 87, 88,
89. The comparators 87, 88, 89 are connected at their second inputs with
the address data bus 61 and via the latter are supplied with the values
Xr, Xa, and Xb (FIGS. 8, 9). The comparison value X of the comparator 86
is fixedly set. The output of the comparator 86 is connected with the
reset input of the column counter 85 and the clock input of a second line
counter 90. The output of comparator 87 supplies the x-synchronization
signal. The outputs of the comparators 88 and 89 are connected with the
two inputs of an AND element 91 the output of whic | | |
