Патент USA US3418525

Dec. 24, 1968
3,418,518
E. G. REESE, JR
CATHODE RAY TUBE DOT MATRIX SHIFTING
Filed May‘ 31, ‘1967
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ICATHQDE RAY TUBE DOT MATRIX SHIFTTNG
Flled May s1,_ 1967
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United States Patent 0
3,438,518
CC
Patented Dec. 24, 1968
1
2
3,418,518
A second de?ection means is provided for positioning the
cathode ray beam vertically in a plurality of successive
dot positions. Circuit means are provided for modifying
at least one of the waveforms provided by the ?rst or
CATHODE RAY TUBE DOT MATRIX SHIFTING
Edward G. Reese, In, Mitford, N.H., assignor to West
inghouse Electric Corporation, Pittsburgh, Pa., a cor
poration of Pennsylvania
Filed May 31, 1967, Ser. No. 642,470
5 Claims. (Cl. 315-22)
second de?ection means such that the cathode ray beam
may be positioned intermediate the normal dot positions,
as dictated by the speci?c character to be displayed on
the cathode ray tube face. The speci?c character to be
displayed also governs an unblanking circuit means which
ABSTRACT OF THE DISCLOSURE
10 causes the cathode ray beam to turn on at speci?c ones
of the dot positions.
First and second de?ection generators position the
cathode ray beam of a cathode ray tube at a plurality of
dot positions forming an n x in matrix array with each
dot position located at a normal row and column co
For more than one character to be displayed, a main
horizontal and vertical sweep generator means may be
provided to position each complete set of dot positions
ordinate of the matrix. A shift circuit is provided and 15 generated by the ?rst and second de?ection means.
adds a predetermined positive or negative voltage to the
BRIEF DESCRIPTION OF THE DRAWINGS
de?ection generator voltage to cause a shifting of the
FIGURE
1 illustrates a typical dot position matrix for
normal dot position, in accordance with a speci?c char
displaying a character;
acter to be displayed. By providing a shifting circuit for
FIG. 2 illustrates the dot matrix of FIG. 1 displaying
both the horizontal and vertical sweep a normal dot posi 20
the character N;
tion may be shifted to eight other positions depending
FIG. 3 is a block diagram illustrating an embodiment
upon the combination of shift signals. The cathode ray
of the present invention;
beam is unblanked at certain dot positions in accordance
FIG. 4 illustrates various waveforms at certain points
with a character to be written, so that the character may
25 in the circuit of FIG. 3; and
be displayed on the cathode ray tube face.
FIG. 5 illustrates the shift circuit portion of FIG. 3 in
somewhat more detail.
BACKGROUND OF THE INVENTION
Field of the invention.-The invention relates to a
cathode ray tube display system, and in particular, to
a read-out display where various characters including
letters, symbols, numerals, punctuation marks etc. are
written on the face of a cathode ray tube for visual or
photographic inspection.
DESCRIPTION OF THE PREFERRED
EMBODIMENT
Referring now to FIGURE 1 there is illustrated a 5 x 7
dot matrix array wherein each of the 35 dot positions
have been given a respective number 1 through 35. Each
dot position represents a point on a cathode ray tube
face where the cathode ray beam would strike (if it were
turned on) as the beam is de?ected horizontally and
Description of the prior art.~——Various methods are em
ployed to display characters on the face of a cathode ray
tube and one of the most basic methods is the dot matrix
method. In the dot matrix method a stepping waveform
vertically by de?ection circuitry. Travel of the cathode
positions the cathode ray beam in a rectangular dot posi
a scan along the Y axis.
tion array and the cathode ray beam is unblanked at each
dot position forming the character to be written, so that
the cathode ray tube face will light up in a plurality of
tiny areas, thus forming the character.
ray beam in a horizontal direction is a scan along the X
axis whereas movement of the beam vertically represents
Normally, the de?ection circuitry provides voltage
waveforms which would position the cathode ray beam
at dot position 1 and thereafter at the next successive
dot position 2 and thereafter at the next successive dot
Generation of extremely high quality characters de
position 3, etc. The present invention includes shifting
pends upon the number of dot positions generated. With
means whereby the normal dot position may be shifted
fewer dot positions there is an inferior diagonal quality
to a point intermediate normal dot positions. By way of
in such letters as A, K, M, N, R, V, W, X, Y and Z.
example, consider dot position 18, a positive shift along
In fact, in many displays there is only one dot position
the X axis will move dot position 18 to dot position 18E
to represent the entire diagonal line. In other instances 50 whereas a negative shift along the X axis will position
rounding off of certain letters such as B, C, D, G, J, O,
it to a point designated 18W. Similarly, a positive shift
P, Q and U is desired.
along the Y axis will move dot position 18 to 18N where
A problem arises however in that to generate enough
as a negative shift will move it to 185. By combinations
dot positions for a high quality array, proportionally
of a positive and negative shifting along the X and Y
more decoding circuits are needed thereby increasing 55 axis, dot position 18 may also be moved to positions
cost and complexity. In addition to the increase in the de
ISNE, 185E, 188W and 18NW.
coding circuits, the unblanking circuits increase in com
One method of shifting a normal dot position would
plexity and there is a proportional increase in memory
be to provide an analog voltage proportional to a desired
requirements.
variable shift distance. However this would require a
If enough dot positions are generated, then the beam 60 somewhat complex analog de?ection circuit. As an alter
energy requirements of the cathode ray tube increase
native a dot position may be shifted by a predetermined
with writing speed.
A general object of this invention is to provide a high
quality character display which obviates the need for the
additional circuitry as required in the prior art.
SUMMARY OF THE INVENTION
There is described a character display apparatus for
a cathode ray tube system which includes a ?rst de?ec
and ?xed amount upon the occurrence of a shift signal.
For most applications this would result in a high quality
character display. By way of example, if the distance
between successive dot positions is D then a normal dot
position may be caused to move 1/3 D. In FIGURE 1
therefore and considering the distance between dot posi
tions 18 and 17, the cathode ray beam may strike the
cathode ray tube face at any one of four points, that
tion means for positioning the cathode ray beam of the 70 is, dot position 18, dot position 18E, dot position 17, and
cathode ray tube horizontally in a plurality of successive
dot position 17W. With both vertical and. horizontal shift
dot positions in accordance with a de?ection waveform.
ing a total of 9 different dot positions is possible; consid
3
3,418,518
4
ering 2 normal dot positions, such as 17 and 18 there
fore, a total of 18 different dot positions is possible.
The provision of shifting a dot position to a point M; the
distance between normally successive dot positions results
in a capability to display high quality characters. In FIG
network which may include various memory and decoding
circuits which then provide the necessary timing and un
blanking signals vfor a proper display of the character. In
the present invention not only are the unblanking signals
provided for character display but means are additionally
URE 2 there is illustrated a character, the letter N, dis
played on a 5 x 7 matrix such as illustrated in FIGURE 1.
provided for modifying at least one of the waveforms of
When the scanning is such that the cathode ray beam
would be at dot position 1 the beam is unblanked, that is
the beam is turned on such that the beam strikes the
cathode ray tube phosphor and dot position 1 is caused to
glow. The Scanning proceeds until dot position 5 where
upon the cathode ray beam is unblanked to cause excita
tion of the cathode ray tube phosphor. The beam is then
de?ected in a Y direction to dot position 6 where it is
unblanked and then scanned from right to left until dot
position 9 at which time a negative shift is provided such
that the cathode ray beam strikes the cathode ray tube
the dot matrix generators for positioning the cathode ray
beam to a point intermediate the normal successive dot
positions as dictated by speci?c characters to be displayed.
In FIGURE 3 provision is made for modifying the output
of generators 42 and 48 by means of shift circuitry 50 and
51 respectively. Each of the shift circuits 50 and 51 receive
respective positive and negative shift signals on lines 53
and 56 from the decode network 60 which is operable not
only to provide the shift signals but to provide an un
blanking signal to the unblanking ampli?er 62 for turning
on the cathode ray beam. The decode network 60 may pro
vide respective shift and unblanking signals in response
to an instruction from computer 64 or alternatively the
face at dot position 9W after unblanking. The cathode
ray beam is unblanked at subsequent dot positions indi 20 decode circuit 60 could be an integral part of the computer
cated, including dot positon 12E shifted positively from
dot position 12, dot position 24W shifted negatively from
dot position 24 and dot position 27E shifted positively
from dot position 27 to thereby provide four extra lighted
64.
The output of the shift circuit 50 is a positive or nega
tive voltage on line 67 and is combined with the output of
tions in a second row, the next plateau labelled 11-15
maintaining the next 5 dot positions in a third row etc.
The combination of waveforms a and b therefore applied
to the de?ection circuitry of the cathode ray tube is oper
trons 1 and 5. The ?rst unblanking signal of waveform c
the matrix generator 42 in the summing circuit 69, the
output of which is eventually fed to the de?ection ampli
areas in the diagonal of the character N instead ‘of just
?er 72 for sweeping the cathode ray beam in the X direc—
one lighted area, that is dot position 18.
tion. Similarly, when the shift circuit 51 receives a positive
In FIGURE 3 there is illustrated apparatus for dis
or negative shift input signal, a positive or negative voltage
playing high quality characters on a face of a cathode ray
of a predetermined value is provided on output line 74
tube in accordance with the present invention. Letter des
and is combined with the output of the matrix generator
ignations in FIGURE 3 refer to corresponding waveforms
48 in summing circuit 75. The de?ecton ampli?er 78 is
of FIGURE 4. The apparatus includes a cathode ray tube
responsive to the output of the summing circuit 75 for
unit 37 including a cathode ray tube 38 the face of which
controlling the cathode ray beam in the Y direction.
is illustrated and upon which is displayed a plurality of
The apparatus thus far described is operable to provide
characters 40‘.
In order to position the cathode ray beam horizontally 35 positioning voltages for a cathode ray beam for the dis
play of a single character. In the majority of instances it is
in a plurality of successive dot positions for displaying
desired to display a plurality of characters so that a mean
a single character, there is provided a ?rst de?ection means
ingful message maybe visualized. Accordingly, there is
in the form of dot matrix generator 42 which is operable
provided de?ection means in the form of main sweep de
to provide a staircase waveform illustrated as solid curve
?ection circuit 81 for the X axis sweep and main sweep
a of FIGURE 4. Each voltage plateau represents a speci?c
circuit 82 for the Y axis sweep, the outputs of which are
X coordinate for the cathode ray beam and each plateau
combined in summing circuits 84 and 85 with the outputs
has been given the number corresponding to the respective
of summing circuits 69 and 75, respectively. The main
dot position such as illustrated in FIGURE 1. In other
sweep de?ection waveforms therefore when combined
words, a de?ection waveform provided by the dot matrix
with the dot matrix generator waveforms have the effect
generator 42 having a magnitude of level 1 will position
the cathode ray beam at dot position 1; with a voltage 45 of providing a plurality of rows of dot matrices each
matrix having the form as in FIGURE 1. In other opera
level at plateau 2 the cathode ray beam will be poistioned
tions, the main sweep de?ections may be governed by a de
at dot position 2, etc. With the waveform a, the cathode
coded computer instruction so that a character may be
ray beam sweeps (facing the tube 38) from left to right
displayed anywhere on the face of the cathode ray tube
for the ?rst row, from right to left for the second row,
such as in aircraft identi?cation and control situations.
from left to right for the third row, etc., although, obvi
Waveforms c and d of FIGURE 4 illustrate the neces
ously other de?ection waveforms could be provided for
sary signals provided by the decode circuit 60 for dis
positioning the cathode ray beam horizontally in a plu
playing the character N as illustrated in FIGURE 2. With
rality of successive dot positions. In an analogous manner,
second de?ection means for positioning the cathode ray
reference therefore to FIGURES 2, 3 and 4, waveform c
beam vertically in a plurality of successive dot positions
appears on output line 88 of the decode circuit 60 and
comprises a plurality of precisely timed pulses. For ease
are provided and takes the form of the dot matrix gener
of understanding each pulse has been given the number
ator 48 which provides the staircase waveform b illustrated
corresponding to the dot position where the pulse occurs
in FIGURE 4 with the ?rst plateau designated 1~5 main
for displaying the character N. By way of example, in the
taining the ?rst 5 dot positions in a ?rst row, the second
?rst row the cathode ray beam is unblanked at dot posi
plateau designated 6-10 maintaining the next 5 dot posi
is labelled 1 and occurs at the same time that waveform a
is at the ?rst plateau. The next unblanking signal labelled
5 occurs when the waveform a is at the plateau labelled 5.
able to provide the dot position matrix of FIGURE 1. 65 After plateau 5 has been reached waveform b drops down
to plateau 6-10 for writing in the second row of the dot
Dot matrix generators such as 42 and 48 for generating
matrix. The third unblanking signal labelled 6 occurs
staircase waveforms are well known to those skilled in the
when waveform a is at plateau 6 and the next unblanking
art. Having the capabilities of providing a dot position
signal occurs at dot position 9. At dot position 9 however,
matrix, means are generally provided for unblanking,
the decode circuit in accordance with the present inven
that is turning on the cathode ray beam at speci?c dot
tion receives on line 54 a negative shift signal and the
positions in accordance with characters to be written.
shift circuit 50 provides a negative pulse labelled 9 in
Generally in such display systems an instruction to display
a certain character or characters may emanate from a char
acter generator or more often, from a computer. The in
waveform d to modify waveform a. This modi?cation
shows up as a decrease in voltage of plateau 9, the de_
struction so provided is received by some sort of decoding 75 crease being illustrated in dotted lines labelled 9W and
5
3,418,518
being equal to 1/3 the difference in voltage between
plateaus 9 and 10 since, it will be remembered, in the
embodiment of the present example the dot position is
1. Display apparatus for displaying characters on the
face of a cathode ray tube comprising:
(A) ?rst de?ection means for providing a ?rst de?ec
tion waveform for positioning the cathode ray beam
horizontally at a plurality of successive normal dot
operable to move 1/3 the distance between normal succes
sive dot positions. The normal unblanking sequence con
tinues up until dot position 12 at which time the decode
circuit provides a positive shift signal on output lead 53
to the shift circuit 50 which then provides an output signal
labelled 12 in waveform d serving to modify the de?ec
positions;
(B) second de?ection means for providing a second
tion waveform a. This modi?cation shows up as a 1/3 in
crease in voltage and is represented by the dotted plateau 10
designated 12E.
This general sequence is continued until the entire
character is displayed. Since the character N does not
require any vertical or diagonal shifts, waveform e rep
resenting the output of shift circuit 51 does not provide
any modifying voltages to the output of dot matrix gen
erator 48 although for those characters which require a
vertical or diagonal shift, waveform b is modi?ed by such
6
I claim as my invention:
15
pulses as was waveform a by the output of shift circuit 50. 20
With respect to the pulses of waveform c it is to be
noted that the pulses do not commence when waveform a
changes to a next plateau, but occur at a time after the
plateau has been reached. This is to ensure that all tran
sients have decayed and then when unblanking occurs the 25
cathode ray beam will strike the cathode ray tube face at
exactly the required dot position. That is, by giving wave
form a time to settle to the respective plateaus, accurate
positioning of the cathode ray beam may take place.
To perform the function of shift circuits S0 or 51 any 30
one of a variety of circuits may be utilized, one such
illustrative arrangement being shown in FIGURE 5 which
additionally shows one type of summing circuit in some
what more detail. The shift circuit 50 includes electronic
switches 90 and 91 connected respectively to positive 35
potential +V and to negative potential —V. The electronic
switches 90 and 91 are normally in an OFF condition such
that neither of the voltages +V or ~V appears at circuit
point 92. Upon the application of a positive shift signal
on lead 53 from the decode circuit 60, electronic switch 40
90 will close thereby applying the +V voltage through
resistor 96 to circuit point 92. Similarly, if a negative shift
voltage is provided on line 54, the electronic switch 91
de?ection waveform for positioning the cathode ray
beam vertically at a plurality of successive normal
dot positions;
(C) shift circuit means for modifying at least one of
said waveforms for positioning the cathode ray beam
to a position intermediate normal successive dot posi
tions in accordance with speci?c characters to be dis
played; and
(D) unblanking circuit means for causing the cathode
ray beam to turn on at certain ones of said positions
in accordance with speci?c characters to be displayed.
2. Apparatus according to claim 1 wherein:
(A) the shift circuit means is operable to supply posi~
tive and/or negative voltages during the course of a
character displayed; and which includes
(B) signal combining means for combining at least one
of the de?ection waveforms with said positive and/
or negative voltages.
3. Apparatus according to claim 1 wherein:
(A) the distance between successive normal dot posi
tions is D; and
(B) the shift circuit means is operable to shift the
normal dot position by 11/3 D.
4. Apparatus according to claim 1 wherein:
(A) the ?rst de?ection means includes a ?rst staircase
waveform generator;
(B) the second de?ection means includes a second
staircase waveform generator; and which includes
(C) decode circuit means for providing output signals
in accordance with particular characters to be dis
played;
(D) a ?rst shift circuit means responsive to the output
of said decode circuit means for changing the level
of particular steps in said ?rst staircase waveform,
and
(E) a second shift circuit means responsive to the
to the circuit point 92.
output of said decode circuit means for changing the
The output of dot matrix generator 42 is applied through
level of particular steps in said second staircase wave
resistor 99 to circuit point 92 which forms the input to
form.
summing ampli?er means 101. Since the output of sum~
5. Apparatus according to claim 1 which additionally
ming ampli?er means 101 is the inversion of the input
signal, there is provided an inverting ampli?er 103 the 50 includes:
output of which constitutes the output signal of the sum
(A) main horizontal and vertical sweep generator
ming circuit 69.
means for positioning each set of dot positions pro
Although the present invention has been described with
vided by the ?rst and second de?ection means.
a certain degree of particularity, it should be understood
that the present disclosure has been made by way of ex 55
References Cited
Will close, applying the voltage —V through resistor 97
ample. The provision of shifting voltages for certain
characters to be displayed in combination with a dot posi
tion matrix generation means may be accomplished with
various other types of circuitry. In addition, the principles
applicable to shifting various dot positions may be applied
UNITED STATES PATENTS
3,090,041
5/1963
Dell _____________ __ 340——324
RODNEY D. BENNETT, Primary Examiner.
to the main X and Y sweeps for variably positioning each 6
character from a normal character position on the tube
face. Other modi?cations and variations of the present
T. H. TUBBESING, Assistant Examiner.
invention are made possible in the light of the above
3l5—24; 340-324
teachings.
U.S. Cl. X.R.