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Publication numberUS3713134 A
Publication typeGrant
Publication dateJan 23, 1973
Filing dateSep 16, 1970
Priority dateSep 16, 1970
Publication numberUS 3713134 A, US 3713134A, US-A-3713134, US3713134 A, US3713134A
InventorsChaney H
Original AssigneeCorning Glass Works
Export CitationBiBTeX, EndNote, RefMan
External Links: USPTO, USPTO Assignment, Espacenet
Digital stroke character generator
US 3713134 A
Abstract
A system for generating characters by deflecting an electron beam over a screen having orthogonal X and Y axes. Beam deflection and modulation commands for each segment of each character are stored in read only memories. The deflection commands are read out to a binary rate multiplier after a character has been selected. The binary rate multiplier generates X and Y pulse trains having independently variable binary rates under the control of the deflection commands. The pulse trains are then applied to X and Y UP/DOWN counters and digital-to-analog converters to generate X and Y deflection signals in analog form having independently variable rates of change corresponding to the binary rates of the digital deflection signals. The polarity or direction of the rate of change is determined by deflection commands which control the direction of count in the UP/DOWN counters.
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Description  (OCR text may contain errors)

United States Patent [19] Chaney DIGITAL STROKE CHARACTER [451 Jan. 23, 1973 1 57 ABSTRACT GENERATOR [75] Inventor: Harry Chaney, Raleigh A system for generating characters by deflecting an 27609 electron beam over a screen having orthogonal X and Y axes. Beam deflection and modulation commands 3] Asslgnee: Commg Glass works commg for each segment of each character are stored in read only memories. The deflection commands are read out [22] Filed; Sept. 16, 1970 to a binary rate multiplier after a character has been selected. The binary rate multiplier generates X and Y [21 1 Appl' 726l3 pulse trains having independently variable binary rates under the control of the deflection commands. The [52] US. Cl. ..340/324 A, 315/18, 315/22 pulse trains are then applied to X and Y UP/DOWN [51] Int. Cl. ..G06f 3/14 count r and digitaLto-analog converters to generate Fleld Search 315/13, 22 X and Y deflection signals in analog form having independently variable rates of change corresponding to [56] Rderences C'ted the binary rates-of the digital deflection signals. The

UNITED STATES PATENTS polarity or direction of the rate of change is determined by deflection commands which control the 3,482,238 12/1969 Stine ..340/324 A direction of count in the UP/DOWN counters. 3,587,083 6/1971 Tubinis ..340/324 A 3,510,865 5/l970 Callahan et al ..3l5/18 3,334,304 8/1967 Fournier etal........ .....340/324 A Primary Examiner-- Donald J. Yusko 5 Claims 4 Drawing Figures Assistant Examiner-Marshall M. Curtis Attorney-Woodcock, Washburn, I Kurtz 8g 7 Mackiewicz, Clarence R. Patty, Jr. and Walter Zebrowski 38x 58X 6 x 74: X 76x 44x 3 1 (A- '32 7/ 32 32 I EEI l6 IS IS 42x8 ,363 2 f5 AND 22 OR "1 co ll en l 3 1 1 I I I DEFLECTION ear 1 48x SOURCE 3 56 68x 35 I 82 1 1 i 62 l g Y 32 I 32 84K g9 88 I u 4 46 gga'- 54 an 0R AND INT. CRT 36 COUNTER 4 a L PULSE SHAPER 4 40 ml 2 1 502 1 T T Boy 8y 4 L m ee DEFLECTION A 32 32 32 42 DATA e a L we y .7- ROM 4 2 AND 2 0R COUNTER l 1 1 K I 44y r 584 y y y DIGITAL STROKE CHARACTER GENERATOR BACKGROUND OF THE INVENTION This invention relates to character generators of the stroke type.

More and more emphasis is being placed on a basic technique which may be utilized for generating characters and symbols for display regardless of the desired shape of these characters and symbols. The dot matrix character generator wherein the electron beam intensity or Z modulation is cut on or off depending on required intensification at particular dots is the simplest way to present characters. However, this method limits the display to a certain type of characters. In particular, it does not permit the display of anything but the simplest block type characters and does not permit the display of script type characters.

Because of the limitation on the types of characters which may be displayed with a dot matrix character generator, stroke generators are in general preferred. In a stroke generator, Z modulation is substantially continuous as the electron beam moves through a continuous stroking display in response to horizontal X axis or vertical Y axis deflection. Although the stroke character generator is preferred in those instances where characters other than the block type are to be displayed, there are difficulties associated with a stroke character generator. One very significant difficulty involves the necessary coordination between X axis and Y axis deflection where the electron beam is being deflected in both the X axis and Y axis directions simultaneously. If coordination between the X axis and Y axis deflection is not maintained, it is not possible to accurately trace any character or symbol having any segment which is non-parallel to either the X axis or the Y axis. Obviously, many characters and symbols include such segments.

SUMMARY OF THE INVENTION It is an object of this invention to provide an improved stroke generator for accurately displaying all character segments for a wide variety of characters.

In accordance with one important aspect of the invention, the character generator comprises a control means having stored deflection commands. A binary rate multiplier means generates X and Y axis pulse trains having independently variable binary rates under the control of the stored deflection commands. The X and Y axis pulse trains are then converted to analog signals having rates of change corresponding to the variable rates for deflecting an electron beam through each segment of each character during uniform segment time intervals.

In accordance with another aspect of the invention, the control means generates modulation commands for Z axis modulation or electron beam intensity control.

In accordance with still another aspect of the invention, the X and Y axis pulse trains are applied to UP/DOWN counters having a direction of count under the control of deflection polarity commands generated by said control means and then converted to analog X and Y deflection signals.

The foregoing and other objects, aspects, features, and advantages of the invention may be better un derstood from the following more detailed description, the appended claims and the drawings.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 schematically represents the display of a character on the screen of a stroke character generator embodying the invention;

FIG. 2 is a block diagram of a stroke character generator embodying the invention;

FIG. 3 is a schematic diagram of particular gate means used in the stroke character generator of FIG. 2; and

FIG. 4 depicts various signals generated by the stroke character generator of FIG. 2.

DESCRIPTION OF A PREFERRED EMBODIMENT FIG. 1 schematically illustrates a screen 20 of a display device such as a cathode ray tube. The screen 20, which has been subdivided into an imaginary grid for purposes of explaining the invention, comprises a continuum of material capable of emitting light energy under electron bombardment from the cathode ray tube electron beam source. The imaginary grid comprises a series of equally spaced! lines parallel to the horizontal X axis and a series of equally spaced lines parallel to the vertical Y axis. For purposes of illustrating the invention, the letter M is shown as displayed on the screen 20.

In order to generate the character M, the following strokes can be made. In generating a first segment 22, the electron beam is deflected along the Y axis from a grid position of 0, 0 to a grid position 0, 32. The stroke of the first segment 22 is achieved by providing increasing Y axis deflection in the form of a ramp function beginning with a magnitude of zero units and increasing to 32 units. No X deflection is applied during this stroke.

In generating a second segment 24, the electron beam is deflected from the grid position 0, 32 to the grid position l3, 15 by simultaneously applying chang ing X and Y deflection forces to the electron beam. In A order to achieve the straight line 24 connecting these positions, the X deflection force must increase by a magnitude of 13 units while the Y deflection force must simultaneously decrease by a magnitude of 17 units.

Third, the electron beam is stroked through a segment 26 from the position 13, 15 to the position 25, 32 by again simultaneously applying changing X and Y deflection forces to the electron beam. For this third stroke, the X deflection force must increase by a magnitude of 12 units while the Y deflection force simultaneously increases by a magnitude of 17 units.

The fourth and last stroke generating a segment 28 deflects'the electron beam from the position 25, 32 to the position 25, 0 by the application of a decreasing Y deflection force and a constant X deflection force.

In accordance with this invention, the deflection for generating each of the segments 22, 24, 26, and 28 in forming the letter M, are generated by X axis deflection signals in the formof ramp functions having various rates of change as well as Y axis deflection signals in the form of ramp functions having various rates of change as shown in FIG. 4. The segments 24 and 26 of the character M are generated by X axis and Y axis deflection signals in the form of ramp functions having different rates of change asshown in FIG. 4. In order to generate segments 22 and 28 of the character M, ramp function Y axis deflection signals are generated as also shown in FIG. 4 while simultaneously generating zero or constant X axis deflection signals. In order to generate the horizontal segments of the letter 2, it is similarly necessary to generate X axis deflection signals which are ramp functions while generating zero or constant Y axis deflection signals. Finally, in order to generate the letter H, it is necessary to generate intensity control signals for modulating the electron beam. A system embodying the invention and capable of generating the foregoing deflection signals for characters such as M, Z, and H will now be described with reference to FIG. 2.

As shown in FIG. 2, the stroke character generator system comprises a control section 30, a pulse train generating section 32, an analog deflection signal section 34, a modulation section 35 and a display device 36. The control section 30 comprises a pair of data ROMs (read only memories) 38X and 38Y for storing X and Y axis deflection commands for each segment of each character to be displayed. The memory section 30 also comprises a control ROM 40 for storing additional commands including Z axis modulation or beam inten sity control commands for each segment of each character to be displayed. In order to provide random access for the particular characters selected at one of the character selection inputs 42X and 42Y, the ROMs 38X and 38Y may comprise diode matrices where the character selection inputs 42X and 42Y are the input lines for the diode matrices and binary deflection command outputs 44X and 44Y, (1, 2, 4, 8, 16, 32) are the output lines of the diode matrices. Depending upon the particular characters selected at one of the input lines 42X, certain of the binary outputs 44X will be energized and the resulting binary outputs will be applied to the digital deflection signal section 32.

The control ROM 40 having character selection inputs 46, one for each character to be selected, may also comprise diode matrices where the character selection inputs 46 are the input lines and deflection polarity command outputs 48X and 48Y are the output lines which are connected to the analog deflection generation section 34. A binary Z axis modulation command output 50Z is connected to the intensity control section 35. The control ROM 40 also includes means for changing the deflection and intensity control commands after each character segment is generated. This may be accomplished by applying suitable control signals from the control ROM 40 to the ROMs 38X and 38Y as shown. The control function may be provided by appropriate logic circuitry well known in the art.

The pulse train generating section 32 comprises a source of clock pulses which may be gated by the control ROM 40 through a connection not shown and a BRM (binary rate multiplier) 53 comprising a ripple counter 54, a pulse shaper 56, AND gate means 58X and 58Y and OR gate means 60X and 60Y. As the clock pulses from the source 52 enter the ripple counter 54 having a four bit section 62 and a two bit section 64, a plurality of pulse trains are generated at each of the pulse train outputs 66. The pulse rates of each of the pulse trains correspond to the binary outputs 44X and 44Y (1, 2, 4, 8, 16, 32), i.e., of one pulse per unit of time, two pulses per unit of time etc. Each of the pulses of the pulse train is then applied to the pulse shaper 56 before application to the AND means 58X and 58Y at inputs 68X and 68Y.

As shown in FIG. 3, each of the AND gate means 58X and 58Y comprises a group of six AND gates 70, one for each of the pulse trains from the ripple counter 54. By selectively enabling particular AND gates in response to deflection commands from the ROMs 38X and 38Y, particular pulse trains will be passed by the AND gate means 58X and 58Y and the OR gate means 60X and 60Y. Where more than one AND gate 70 is enabled, more than one pulse train will be passed and the pulse trains leaving the OR gate means 60X and 60Y will be composite pulse trains having pulse rates equal to the sum of the rates of the component pulse trains.

The analog deflection signal section comprises the UP/DOWN counters 74X and 74Y in series with digital-to-analog convertors 76X and 76Y respectively. As the pulse trains from the OR gate means 60X and 60Y enter the UP/DOWN counters 74X and 74Y respectively, binary outputs of the UP/DOWN counters produce a count representing the pulse rate of the composite pulse trains. Note that pulse rate is a direct function of particular deflection commands at the output 44X and 44Y which are then applied to the AND gate means 58X and 58Y. Since the deflection commands at the outputs 44X and 44Y are mutually and independently variable depending upon the particular segment of a particular character, the binary rate of the composite pulse trains applied to the UP/DOWN counters 74X and 74Y are mutually and independently variable. Of course, the resulting analog deflection signal generated by the digital-to-analog convertor 76X and 76Y are ramp functions having mutually independent rates of change corresponding to the binary rates. Accordingly, the analog deflection signals which are applied to deflection circuitry 80X and 80Y associated with a cathode ray tube 82 of the display section 36 are mutually independent.

The composite pulse trains from the OR gate means 60X and 60( are also applied to the intensity control section 35 comprising an OR gate 84 in series with an AND gate 86 selectively enabled by the intensity control commands at the modulation command output 50Z of the control ROM 40. The resulting digital intensity control signal is then applied to intensity control circuitry 88 of the display section 36.

The operation of the stroke character generator of FIG. 2 will now be described by describing the generation of the character M as shown in FIG. 1. With the character M selected at the character selection inputs 42X, 42Y, and 46, the ROM outputs 44X, 44Y, 48X, 48Y, and 50Z are as follows:

44X 48X 50Z 48Y 44Y 32168421 32168421 0000000 11 100000 0011011 10 010001 0011001 11 010001 0000000 10 100000 During the stroking of the segment 22, the outputs 44X are all in the low state 0 while the output 44Y (32) is in the high state l so as to enable the AND gate 70 of the AND gate means 58Y having a pulse train input of 32 pulses per unit of time as shown in FIG. 4. By placing the UP/DOWN counter 74Y in the up counting state by a 1 at the output 48Y and modulating the beam with an output of 1" at the output 50Z, the ramp function for stroking the segment 22 is generated as shown in FIG. 4.

At the end of this stroke, the control ROM 40 changes the commands from the control section 30. In particular, the outputs 44X (8, 4, and l) are now I with the outputs 44Y (16 and l) l to stroke the segment 24. As a result, the AND gates 70 of the AND gate means 58X which are coupled to pulse trains having 8, 4, and l pulses per unit of time and the AND gates 70 of the AND gate means 58Y which are coupled to pulse trains having a pulse rate of 16 and 1 pulses per unit of time are applied to the UP/DOWN counters 74X and 74Y. Because of the OR gate 60X and 60Y, composite pulse trains comprising 13 pulses per unit of time and 17 pulses per unit of time as shown in FIG. 4 are applied respectively to UP/DOWN counters 74X and 74Y. The UP/DOWN counter 74X is maintained in the up counting state since the output 48X is I while the UP/DOWN counter 74Y is in the down counting state since the output 48Y is 0 to generate the ramp functions shown in FIG. 4. The electron beam is modulated throughout the stroking of the segment 24 since the output 50Z is 1 The stroking of the segment 26 is similar to the stroking of the segment 24 except that the outputs 44X (8 and 4) are l to produce only 12 pulses per unit of time as shown in FIG. 4 for application to the UP/DOWN counters 74X. In addition, the UP/DOWN counter 74Y is now in an up counting state due to the 1 at the output 48Y.

The stroking of the segment 28 is substantially identi cal to the segment 22 except that the UP/DOWN counter 74Y is in the down counting state due to the 0" at the output 48Y and the count of the UP/DOWN counter 74X remains at 25 since all outputs 44X are iKOQQ Although the letters M, Z, and H are specifically mentioned in the foregoing, it should be appreciated that character generator of FIG. 2 may be utilized to generate a wide variety of characters including the ASCII business characters. It should also be understood that the various'components shown in block form comprise commercially available and otherwise substantially conventional elements well known to those of ordinary skill in the art.

Although the invention has been described in terms of a particular embodiment, various changes and modifications may be made without departing from the spirit of the invention or the scope of the appended claims.

What is claimed:

1. A character generator system of the type having a display device including a screen, an electron beam source, an X deflection means for deflecting the beam across the screen in a direction parallel to the X axis, and a Y deflection means for deflecting the beam across the screen in a direction parallel to the Y axis, said system comprising:

a control means for generating digital X axis deflection commands representing appropriate X axis deflection and digital Y axis deflection commands representing appropriate Y axis deflection during time intervals of substantially uniform length for each segment of each character to be displayed;

a pulse train generating means comprising a source of pulses and a binary rate multiplier coupled to the output of said control means for generating digital X axis and Y axis pulse trains for each segment having independently variable binary rates determined by said X axis and Y axis deflection commands, said X axis and Y axis pulse trains for each segment being generated in one of said time intervals of substantially uniform length regardless of segment length;

an analog deflection signal generating means coupled to the output of said pulse train generating means for generating analog X axis and Y axis deflection signals from said X axis and Y axis pulse trains respectively for application to the X deflection means and the Y deflection means respectively, said analog X axis and Y axis deflection signals generating each segment of each character during one of said time intervals of substantially uniform length, said analog signals having rates of change corresponding to said independently variable binary rates; and

an intensity control gating means having an input coupled to the output of said. binary rate multiplier and an output coupled to said display device for controlling the intensity of said electron beam in response to said X axis and Y axis pulse trains.

2. The character generator system of claim 1 wherein said control means includes means for generating Z axis modulation commands for each segment of each character to be displayed for selectively enabling the intensity control gating means in response to said Z axis modulating commands.

3. The character generator system of claim 2 wherein said control means generates polarity commands for each segment of each character to be displayed, and said analog deflection signal generating means includes means for controlling the polarity of said rate of change of said analog X axis and Y axis deflection signals in response to said polarity commands.

4. The character generator system of claim 1 wherein said binary rate multiplier comprises:

a counter generating a plurality of outputs having different binary rates;

AND gate means comprising an X group of gates and a Y group of gates, the plurality of said outputs from said counter being applied to corresponding inputs of said X group of gates and said Y group of gates, said X group of gates and said Y group of gates being selectively enabled by said deflection commands so as to generate a combined output at said X group of gates and a combined output at said Y group of gates having binary rates equal to the sum of the binary rates for the particular gates enabled in said X group of gates and said Y group of gates respectively; and

an X OR gate means and a Y OR gate means having inputs coupled to the outputs of said X group of gates and said Y group of gates respectively, the outputs of said X OR gate means and said Y OR gate means providing the inputs to said X analog deflection signal means and said Y analog deflection signal means respectively.

5. The character generator system of claim 4 wherein said control means generates deflection polarity commands for each segment of each character to be displayed, said analog deflection signal generating means comprising X and Y axis UP/DOWN counters coupled to the output of said X OR gate means and said Y OR gate means respectively and further comprising X and Y axis digital-to-analog convertors coupled to the outputs of said X and Y axis UP/DOWN counters, the counting direction of each said UP/DOWN counter being controlled by said deflection polarity commands.

Patent Citations
Cited PatentFiling datePublication dateApplicantTitle
US3334304 *Mar 1, 1965Aug 1, 1967IbmAsynchronous character generator for successive endpoint definition
US3482238 *May 27, 1966Dec 2, 1969Burroughs CorpMultilevel blanking control and momentary stroke inhibition for visual display apparatus
US3510865 *Jan 21, 1969May 5, 1970Sylvania Electric ProdDigital vector generator
US3587083 *Sep 28, 1967Jun 22, 1971Xerox CorpCharacter generation and display system
Referenced by
Citing PatentFiling datePublication dateApplicantTitle
US3775760 *Apr 7, 1972Nov 27, 1973Collins Radio CoCathode ray tube stroke writing using digital techniques
US3911417 *Apr 27, 1973Oct 7, 1975Univ IllinoisMethod and apparatus for plotting line segments and characters on a display device
US4115863 *Dec 7, 1976Sep 19, 1978Sperry Rand CorporationDigital stroke display with vector, circle and character generation capability
US4143360 *Aug 27, 1976Mar 6, 1979The Magnavox CompanyMethod and apparatus for controlling a display terminal
US4156915 *Mar 28, 1977May 29, 1979Vector General, Inc.Font generating system
Classifications
U.S. Classification345/18
International ClassificationG06F7/60, G09G1/06, G06F7/68, G09G1/10
Cooperative ClassificationG06F7/68, G09G1/10
European ClassificationG06F7/68, G09G1/10