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US3609745A - Symbol display apparatus - Google Patents

Symbol display apparatus Download PDF

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Publication number
US3609745A
US3609745A US721477A US3609745DA US3609745A US 3609745 A US3609745 A US 3609745A US 721477 A US721477 A US 721477A US 3609745D A US3609745D A US 3609745DA US 3609745 A US3609745 A US 3609745A
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United States
Prior art keywords
deflection
sequence
signals
character
constant
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Expired - Lifetime
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US721477A
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English (en)
Inventor
William R Lamoureux
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International Business Machines Corp
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International Business Machines Corp
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    • G—PHYSICS
    • G09—EDUCATION; CRYPTOGRAPHY; DISPLAY; ADVERTISING; SEALS
    • G09G—ARRANGEMENTS OR CIRCUITS FOR CONTROL OF INDICATING DEVICES USING STATIC MEANS TO PRESENT VARIABLE INFORMATION
    • G09G1/00—Control arrangements or circuits, of interest only in connection with cathode-ray tube indicators; General aspects or details, e.g. selection emphasis on particular characters, dashed line or dotted line generation; Preprocessing of data
    • G09G1/06—Control arrangements or circuits, of interest only in connection with cathode-ray tube indicators; General aspects or details, e.g. selection emphasis on particular characters, dashed line or dotted line generation; Preprocessing of data using single beam tubes, e.g. three-dimensional or perspective representation, rotation or translation of display pattern, hidden lines, shadows
    • G09G1/08—Control arrangements or circuits, of interest only in connection with cathode-ray tube indicators; General aspects or details, e.g. selection emphasis on particular characters, dashed line or dotted line generation; Preprocessing of data using single beam tubes, e.g. three-dimensional or perspective representation, rotation or translation of display pattern, hidden lines, shadows the beam directly tracing characters, the information to be displayed controlling the deflection and the intensity as a function of time in two spatial co-ordinates, e.g. according to a cartesian co-ordinate system
    • G09G1/10—Control arrangements or circuits, of interest only in connection with cathode-ray tube indicators; General aspects or details, e.g. selection emphasis on particular characters, dashed line or dotted line generation; Preprocessing of data using single beam tubes, e.g. three-dimensional or perspective representation, rotation or translation of display pattern, hidden lines, shadows the beam directly tracing characters, the information to be displayed controlling the deflection and the intensity as a function of time in two spatial co-ordinates, e.g. according to a cartesian co-ordinate system the deflection signals being produced by essentially digital means, e.g. incrementally

Definitions

  • Symbols are selectively generated as a sequence of strokes from a capacitor read-only storage. By applying these strokes through the deflection control circuitry of the cathode-ray tube at a rate which exceeds the time constant of the high frequency yoke, a quasi-integration of the input staircase is provided resulting in uniform display intensity.
  • one method of character generation is the full screen scan technique in which the CRT beam scans either horizontally or vertically and is selectively unblanked to define characters either as a raster of dots or as a sequence of horizontal or vertical strokes.
  • Such systems have the advantage that the beam traverses the phosphor at a uniform velocity, providing a constant grid-tocathode voltage change on the cathode-ray tube and a resultant uniform intensity.
  • a CRT display system which combines the desirable features of the scan and stroke systems without the corresponding disadvantages by operating a variable velocity system in a simulated constant velocity mode.
  • Characters which are initially identified by digitally encoded information from a data processor or an associated storage device are decoded to select a specific character for display.
  • the character code representations for said selected character are then translated into a sequence of short strokes from a read-only storage in which the individual stroke information for each specific character is stored.
  • a sequence of five-bit digital words are generated under the control of a timing pulse distributor on l25-nanosecond centers.
  • a primary object of the present invention is to provide an improved direct view display apparatus.
  • Another object of the present invention is to provide an improved variable velocity cathode-ray tube character generator adapted to provide uniform display intensity without intensity correction apparatus by simulating a constant velocity operational mode.
  • Still another object of the present invention is to provide an improved cathode-ray display system wherein uniform intensity is provided by generating character component strokes which are applied directly to the deflection yoke of the CRT at a rate which exceeds the time constant of the deflection yoke to simulate a constant velocity system.
  • Another object of the present invention is to provide an improved display system wherein a capacitive read-only matrix storage device is employed to generate video signals for a CRT display.
  • FIG. 1 illustrates in block logical form a preferred embodiment of the present invention.
  • FIG. 2 illustrates in schematic form a preferred embodiment of the read-only storage.
  • FIG. 3 illustrates an illustrative character generated in accordance with the present invention.
  • coded character signals are applied from a data source which might comprise, for example, a data processor or an associated storage unit to a character select decoder 21.
  • a data source which might comprise, for example, a data processor or an associated storage unit
  • the coded character signals were stored on a recirculating delay line.
  • a character capability of 2 or 64 characters is contemplated, so that six binary bits are used in the character code.
  • the character select decoder 21 will select one of 64 characters and energize the selected line as more fully described hereinafter.
  • each character is composed of a number of individual segments called strokes, the number of strokes being determined by the character configuration, the length of each individual stroke being controlled by the time between pulses from timing pulse distributor 27.
  • a maximum of 40 strokes is required to generate the most complex character contemplated.
  • the time required for 40 strokes is allotted to each character, although the invention could be modified for asynchronous operation.
  • each character may be considered composed within a l0 6 strobe matrix, positioned within a 12x8 character box.
  • the character will be initially positioned by a main deflection yoke (not shown) to the starting position, which for most characters, is the 00 position in the lower left portion of the character box and represents the reset position of the deflection counters, then generated upwardly as 10 vertical segments to the point 33 where a horizontal deflection is initiated. Since at any point in the construction of a character it may be necessary to move the beam upwardly or downwardly, to the left or right, or at 90 combinations, four binary bits of deflection information are required for each stroke. For purpose of illustration, a binary 1 will be assumed to deflect the beam to the right or up, and a binary O to move the beam to the left or down in the horizontal or vertical directions respectively.
  • the time constant of the high-speed deflection yoke employed in the preferred embodiment of the instant invention is l75 nanoseconds, while the individual vector segments are generated on l25-nanosecond centers, or a ratio of approximatelyfi.
  • the yoke is never allowed to settle during a character generation cycle. Due to the characteristics of the yoke and specifically the setting time, the deflection will vary as a function of the deflection voltage and when it occurred in the cycle.
  • the generation of the character B is shown to illustrate the operation of the subject invention. At the initiation of the cycle, the character generator is set to the position shown as point 31.
  • the first vertical command will produce a deflection of about one-half unit
  • the next vertical deflection coupled with the settling of the first vertical command will terminate a 1%. units
  • the third vertical command, summing with the first two will settle at about 2% units
  • the fourth will settle at nearly 3 units
  • the fifth command at nearly four units.
  • the position of the beam will never be more than one unit behind its associated timing pulse. Since the vertical bar in the B character is intended to be units high, it requires 11 units of current to obtain 10 units of deflection distance.
  • the settling resulting from steps 8, 9, l0 and ll, if not inhibited, would carry the beam to the point 35 beyond turning point 32 as desired.
  • a negative vertical deflection signal is applied at point 33 to counteract the deflection produced by settling of the yoke at the same time that the first horizontal positive deflection signal is applied.
  • the approximately square root relationship between the stepping time of the deflection signals and the time constant of the high frequency yoke produces a nearly perfect right angle turn.
  • the fact that the yoke is then allowed to settle also provides for angles which are not at the major points of the compass, and produces an apparent fine line curve as shown in FIG. 3b.
  • the stroke generator comprises in the preferred embodiment capacitor diode read-only memory in which the individual strokes for each character are stored.
  • capacitor diode read-only memory in which the individual strokes for each character are stored.
  • each character position is addressed.
  • the address time for character position constitutes a substantial portion of the total cycle time relative to character draw time. For example, if character draw time is 4 microseconds, the address time could be 2 microseconds or more.
  • the read-only storage system employed in the instant invention does not operate on a normal memory cycle mode.
  • the expanded code (video) behind the address is fetched, and the memory is readdressed for the next cycle.
  • the read-only storage 25 employed in the preferred embodiment addresses a block of words for the next character during the character move time when the beam is being repositioned by the main deflection for the next character.
  • the block of words thus addressed contains all of the strokes within a given ASCII code.
  • the only storage employed in the preferred embodiment is a capacitor-diode-gating arrangement comprising a rectangular array of capacitors which are batch fabricated using double-clad flexible circuitry.
  • lt consists of a capacitor matrix etched on a two-sided copper clad Mylar sheet.
  • Mylar is a trademark for a polyester film and more specifically a polyethylene terephthalate film.
  • An information bit is contained at the intersection of a time pulse line and a sense line by the pressure or absence of an etched capacity plate on both sides of the Mylar sheet.
  • the intersections containing capacitor plates are arbitrarily defined as binary ones, and those without plates are defined as binary zeros.
  • FIG. 2 shows the configuration for a specific character including five individual outputs for the +X, X, +Y, Y and Z intensity lines respectively.
  • a positive reference signal is applied to input terminal 41 and to the biasing resistors 43, 44, 45, 46 and 47 associated with the five outputs l-X, X, +Y, Y and 2 respectively.
  • the signal level applied to the character select terminal 41 during normal operation is approximately +3 volts.
  • the signal level applied from the timing pulse inputs labeled TP 1 through TP 40 is normally maintained at about a 3 volts level so that during the nonselected operation, the voltage across the capacitors is normally zero.
  • the resultant output applied to character select terminal 41 is approximately zero volts.
  • Each of the five output lines has a diode 51, S2, 53, 54 and 55 associated therewith, and a reference voltage is applied to bias these diodes through 7.5 K. resistor 49.
  • the signal level applied to character select terminal 41 drops to approximately zero volts for 2 microseconds, and all of the capacitors of the associated character are correspondingly biased.
  • each of the timing pulse terminals As a negative timing pulse is of approximately 3 volts and -lO0-nanosecond duration is applied to each of the timing pulse terminals in turn, a signal will be coupled wherever a capacitor exists through the associated output diode 51 through 55 to the associated sense amplifiers (not shown). The remaining inputs to each of the sense amplifiers will be the corresponding stroke signal associated with the remaining 63 characters. Thus, each sense amplifier has 64 inputs, only one of which will be energized at any given time.
  • the intensity control line 67 will generate signals through its associated capacitors to control a latch or any bistable device which in turn controls the blank/unblank condition of the cathode-ray tube such that the beam is intensified only during the character-generating sequence.
  • the subject invention operates in a push-pull environment such that the horizontal and vertical deflection will receive a positive signal in one of the two directions required to drive the yoke.
  • a timing pulse applied to TP 1 will cause an output to be generated from capacitor 69, 71 and 73 corresponding to the +X, +Y and Z intensity lines, respectively.
  • each succeeding timing pulse will produce an output on its associated output lines 5659 and 67 which in turn will be coupled through the associated diodes 51 through 55 to generate its respective signal on lines 81-85 which in turn are detected by the associated sense amplifiers.
  • the specific pattern illustrated in H0. 3 is a random pattern which does not apply to any specific character, but is employed merely to illustrate the principles of the present invention.
  • a sequence of 1 1 successive timing pulses will be applied to generate the initial vertical line associated with the character, while on the uppermost portion as previously indicated, a negative vertical deflection signal will be applied to counteract the positive beam movement resulting from the yoke settling.
  • the same technique is used in both axes regardless of direction of movement to counteract the effect of yoke settling.
  • the horizontal condition would remain the same so that no capacitors would be associated with the horizontal sequency during this interval.
  • the resultant output signals on lines 81 through 85 are applied to a sense and control circuit shown as block 87 in FIG. 1.
  • the sense and control circuits shown as block 87 include sense amplifiers and control circuitry for the X and Y counters 91 and 93 and the intensity control circuit 95. These signals are applied as a parallel five-bit word, two bits to each of the X and Y counters 91, 93 and a single intensity control bit to the intensity control circuit 95.
  • a +X signal on line 97 will increment the X counter 91 by one, a -X signal on 99 will decrement the X counter 91 by one.
  • a +Y signal on line 101 will increment the Y counter 93 by one, and a -Y signal on line 103 will decrement the Y counter 93 by one.
  • the X and Y counters 91 and 93 are not binary counters since S-megacycle operation of binary counters is not suitable for this application. ln the character format described in the present invention, it was noted that characters were generated in an 8X12 character box. Accordingly, the X counter contains eight bits and the Y counter 12 bits and each counter position requires one latch. While various counters having the above-described characteristics may be employed, a preferred digital counter is shown in copending application Ser. No.
  • the yoke drivers 117 and 119 drive the X-windings 127 and 129 of yoke 125 in a push-pull mode, while the Y-current drivers 121 and 123 drive the Y-windings 131 and 133, respectively.
  • the X- and Y-yoke windings are damped by their associated resistors 137, 139, and 141, 143, respectively, such that the magnetic field is continually changing at a uniform rate via the applied S-megacycle pulses to provide uniform and constant intensity.
  • a yoke having an inductance of 100 microhenries is employed, while the associated windings have a damping resistor of 2 k. ohms.
  • the same technique could be utilized in electrostatic deflection by using the RC time constant instead of the L/R utilized in the preferred electromagnetic embodiment.
  • the individual segments were 16 mils, or approximately the same as a spot size, and the system was synchronous in that time pulses were allowed for each character.
  • an asynchronous system could be readily provided and in its simplest embodiment would require only an additional sense line with a capacitor positioned after the last segment to be generated to provide the control signal indicating the end of the character.
  • the character selection signal applied to the character select decoder 21 originated in a recirculating delay line memory wherein only the six bit coded signal indicative of the characachieves the benefits of the scan and monoscope systems in that fine lines are achievable as with the absolute vector system, a uniform brightness is provided for a given grid-tocathode voltage, plus the inherent digital accuracy of the read only memory without the adjustment and drift of some of the monoscope systems and without the loss of reliability in a dual CRT machine and the increased scheduled maintenance implied by the balancing of two independent analog subsystems.
  • a cathode-ray tube having beam deflection and beam intensity control means, said beam deflection means having a predetermined time constant
  • a display system according to claim 1 wherein said means for generating said sequence of unit increment deflection signals corresponding to said selected symbols comprises a read-only storage device.
  • a display system of the type claimed in claim 1 wherein said beam deflection means comprises a magnetic deflection system including a magnetic yoke having a predetermined time constant.
  • Apparatus of the type claimed in claim 6 wherein said means for generating said sequence of substantially unit increment deflection signals comprises a read-only storage device.
  • said beam deflection means comprises an electrostatic deflection means having a predetermined R.C. time constant.
  • beam deflection means having a predetermined time constant
  • said beam deflection means comprises a magnetic yoke having a predetermined time constant.

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  • Engineering & Computer Science (AREA)
  • Radar, Positioning & Navigation (AREA)
  • Remote Sensing (AREA)
  • Physics & Mathematics (AREA)
  • Computer Hardware Design (AREA)
  • General Physics & Mathematics (AREA)
  • Theoretical Computer Science (AREA)
  • Controls And Circuits For Display Device (AREA)
  • Details Of Television Scanning (AREA)
  • Video Image Reproduction Devices For Color Tv Systems (AREA)
US721477A 1968-04-15 1968-04-15 Symbol display apparatus Expired - Lifetime US3609745A (en)

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Application Number Priority Date Filing Date Title
US72147768A 1968-04-15 1968-04-15

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US3609745A true US3609745A (en) 1971-09-28

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US (1) US3609745A (nl)
AT (1) AT297106B (nl)
BE (1) BE731529A (nl)
CH (1) CH479917A (nl)
FR (1) FR2006224A1 (nl)
GB (1) GB1244084A (nl)
NL (1) NL163642C (nl)
SE (1) SE339582B (nl)

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US20090322655A1 (en) * 2008-06-26 2009-12-31 Honeywell International Inc. Systems and methods for modifying an intensity of a cathode ray tube stroke signal within a digital display system

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US20090322655A1 (en) * 2008-06-26 2009-12-31 Honeywell International Inc. Systems and methods for modifying an intensity of a cathode ray tube stroke signal within a digital display system

Also Published As

Publication number Publication date
NL6905592A (nl) 1969-10-17
DE1918372A1 (de) 1970-01-15
AT297106B (de) 1972-03-10
DE1918372B2 (de) 1972-10-19
NL163642C (nl) 1980-09-15
CH479917A (de) 1969-10-15
NL163642B (nl) 1980-04-15
BE731529A (nl) 1969-09-15
GB1244084A (en) 1971-08-25
SE339582B (nl) 1971-10-11
FR2006224A1 (nl) 1969-12-26

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