CA1275334C - Raster scanning system - Google Patents
Raster scanning systemInfo
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- CA1275334C CA1275334C CA000551459A CA551459A CA1275334C CA 1275334 C CA1275334 C CA 1275334C CA 000551459 A CA000551459 A CA 000551459A CA 551459 A CA551459 A CA 551459A CA 1275334 C CA1275334 C CA 1275334C
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Abstract
ABSTRACT
IMPROVED RASTER SCANNING SYSTEM
A unique intra-dot scanning system which gives superior quality speed performance. The intra-dot and inter-dot scanning system is applicable to both serial and line impact dot matrix printers, line and serial thermal printers, ink jet, laser and LCD printers, as well as computer monitors and television. The scanning is perpendicular to the beam's motion over the tube and one synchronized cycle is completed while the beam travels one-half dot diameter to three dot diameters.
In the preferred embodiment, the raster scanning system is a cathode ray tube display having a source of an intensity modified electron beam and a main means for deflecting the beam to create a series of horizontal sweeps of the beam from the top to the bottom of a display screen; the deflection means comprises a secondary means for deflecting the electron beam; and, the driver means comprises signal producing means for applying a repetitive sinusoidal electrical signal to the deflection means.
IMPROVED RASTER SCANNING SYSTEM
A unique intra-dot scanning system which gives superior quality speed performance. The intra-dot and inter-dot scanning system is applicable to both serial and line impact dot matrix printers, line and serial thermal printers, ink jet, laser and LCD printers, as well as computer monitors and television. The scanning is perpendicular to the beam's motion over the tube and one synchronized cycle is completed while the beam travels one-half dot diameter to three dot diameters.
In the preferred embodiment, the raster scanning system is a cathode ray tube display having a source of an intensity modified electron beam and a main means for deflecting the beam to create a series of horizontal sweeps of the beam from the top to the bottom of a display screen; the deflection means comprises a secondary means for deflecting the electron beam; and, the driver means comprises signal producing means for applying a repetitive sinusoidal electrical signal to the deflection means.
Description
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B_ckqr_und _f the Invention The presen~ invention xelates to raster scanniny systems such as dot ma-trix printers, televisions, CRT
monitors, and the like.
Many devices use a so-called "raster" scanning system. These include dot matrix prin~ers and cathode ray tube (CRT) displays such as used in television sets and computer monitors. In any raster device, a dot-producing entity moves across the display area repeatedly on a line-by-line basis. In a printer/ it is a printhead moving across the paper. With the CRT, it is an electron beam moving across the phosphors of the CRT screen.
There are two dot matrix principles used in dot matrix print-ers today. One uses a matrix which is approximately equal to the dot size. The second uses a dot size that is up to ten times larger than the matrix.
As used herein, "Matrix" means the spacing between the possible dot positions or the number of possible dot positions per inch horizontally and vertically.
All quality printing by impact dot matrix printers uses a dot size considerably larger than the matrix.
While in the draft mode, the dot size and the matrix are usually approximately the same.
Quality printing is generally performed by using a seven to nine pin printhead and using multiple passes of the printhead while moving the printhead or paper a fraction of a dot between passes (Reference: R.C.
Sanders Patent No. ~,159,882). Another method currently used is to use eighteen to twenty-four pins arranged in two or three staggered rows. At the same time, the matrix used for firing pins during the horizontal sweep of the carriage is a fraction of a dot width.
Most thermal and laser printers use a dot size equal to the matrix, while ink jet printers have been designed both ways. Most, if not all, CRT monitors use a dot size equal to the matrix size. The new improved CRT monitors will use dot sizes that are equal to the matrix size as ~ 7 ,~
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well as dot sizes that are much larger than the matrix size.
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This invention is based on using a dot size much larger than the ma-trix size regardless of the type of device. To achieve scanning by a dot matrix printing system accoxding to the present invention, the printing means is moved relative to the recording means with a scanning motion having a major direction and means are provided for imposing on the scanning motion a cyclical variation in the direction of the motion transverse to its major direction. In one preferred form of the invention (intra dot scanning), the cyclical variation completes at least one cycle during a scan equal to the dot size. The cyclical scan has a duration equal to or longer than the dot refire time and an integral number of dots can be created at predetermined points along the cyclical path. In order to minimize confusion, the application of this principle to various types o~
~0 printers is described separately in the following detailed description. The use of the present invention with CRT monitors is then addressed. Where dimensions and performance capabilities are given, they are by way of example only and reflect tested modifications of actual devices performed by applicant herein.
In accordance with one aspect of the present invention, there is provided a raster scanning system comprising: (a) means Eor repeatedly sweeping an image producing means across a display medium to produce a series of sweeps for the creation of visual images in said series of sweeps; (b) deflection means for cyclically deflecting the image producing means in a direction substantially normal to the sweep direction in a repetitive series of like oscillations throughout each image producing sweep across the display medium; (c) means for controlling the image producing means to vary the brightness of pixels created; (d) means for supplying a first image information signal synchronized with said repetitive series of oscillations to con~rol the controlling means to produce vlsual image information on said display medium at one set of desired S corresponding locations on each of desired ones of the oscillations during a the sweep; and (e) means for supplying at least a second image information siynal synchronized with the repetitive series of oscillations to control the controlling means to produce visual image information on said display medium at another set of desired corresponding locations on each of desired ones of said oscillations during the said sweep.
In accordance with another aspect of the present invention, there is provided a cathode ray tube display such as a computer monitor, television, or the like including a raster scanning system having a source of an int~nsity controllable electron beam and a main means for deflecting the beam to create a series of horizontal sweeps of the beam from the top to the bottom of a 2~ display screen for selectively creating a series of pixel dots in a series of parallel rows comprising: (a) deflection means for deflecting the dot creating means in a direction substantially normal to the sweep direction;
(b) drive means operably connectad to the deflection means for cyclically deflecting the dot-producing means in a repetitive pattern throughout each dot-producing sweep across the display medium, the driving means comprising a signal producing means for applying a repetitive electrical signal to the deflection means to produce a peak to peak amplitude of the pattern which is equal to the spacing between horizontal sweeps; and (c) means for providing an image information signal synchronized with the repetitive pattern to control said intensity controllable electron beam to generate two parallel image lines for each sweep.
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-- 3a -Descri~L~ L~ ~LZ ~lls Figure 1 is an end view of one type of dot matrix S printhead that can be used with the present invention.
Figure 2 is a side view of the printhead o-f Figure 1 showing the means for oscillating the printhead transversely to the major scanning direction.
Figure 3 is an enlarged schematic diagram of the path of the print pins across the paper for the printhead oE Figures 1 and 2.
Figure 4 is an enlarged view of typical type font like characters producsd by the printhead of Figures 1 and 2 when moved through the path of Figure 3 according lS to the technique of the present invention.
Figure 5 is a side view of a vertical scanning mechanism for one and two pin prin-ters employing the ~,7 pres~nt invent;on~
Figure 6 ;s an enlarged schemat;c diagram of the path of ~he electron beam scan in a CRT for a 1~'~
computer ~onitor when operated according to the present 5 invent;on.
Figures 7 and 8 are front and top v;ews~
respectively, of a magnetic CRT adapted to operate according to the present ;nvention.
Figure 9 is an enlarged schematic diagram of the path of the electcon beam scan in a CRT according to the presen~ invention when using offset deflection to obtain pseudo sawtooth scanning~
Figures 10 and 11 are front and side vie~s, respectively, of an electrostatic CRT adapted to operate according to the present invention.
Figure 12 is an enlarged schematic diagram of the path of the electron beam scan in a CRT according to the present invention when using a clippéd sine wave with electrostat;c deflection to obtain pseudo square ~ave Scanning Figure 13 is an enlarged schematic diagram of the path of the electron beam scan in a CRT according to the present invention during hor;zontal scan ~ith fractional scan shown.
F;gure 14 is a diagram of a group of adjacent pixels in a CRT.
Figures 15 and 16 are block diagrams of circuits according to the present invention for interpolating between horizontal scans in a CRT~
F;gure 17 is a block diayram of another embodiment of the invention~
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Serial Impact Dot Matri~ Pr;nter Using A twelve pin printhead 10 ;s used in th;s first :
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~ 5 example arranged in two ro~s of six p;ns 12 as sho~n in F;gure 1. The vert;cal spacing of the p;n centers is 1/~8" irl each row and d~e~ to the staggeringD the e~fective spacing between the p;n centers is appro~imate~y 1/96". The pin d;ameter ;s1/72" and the dot diameter made on the paper is sixteen mils. If the p;n diameter is reduced or increased, it is important to scale the above dimensions as well as to increase or decrease the number of pins in the printhead.
The ends of the pins are moved ;n sinusoidal fashion five mils as the carriage (not shown) is moved hori20ntally across the paper. Referring to F;gure 2, this notion is created by driver 14 operatin~ on the pr;nthead 10~ Since the printhead 10 is supported on a frame 18 by spr;ng means 1b, the printhead ~;ll oscillate at a freqlJency controlled by the drive and the spring mount~ One cycie is made every time the carriage is moved 1/96" horizontally~ The perm;ss;ble firing points (;.e. the matrix) are approx;mately ten points --equally div;ded ;n time for every complete vert~cle sine wave cycle. This gives a matrix size of 9601;nch horizontally and about 300/inch vertically. It should be obvious to one skilled in the art that the intra-dot scanning cycle could be divided into a lesser or greater number of permissible firing points, say six to t~enty po;nts. It is ;mportant that there be an integral number of fir;ng points per intra-dot scanning cycle~
The motion of the end of the pins for a twelYe p;n pr;nthead ;s shown ;n Figure 3. A typical dot as produced by the pins 12 is indicated as 20 while the sinusoidal path traversed by each of the pins 12 as the carriage moves across the paper is indicated as 22~ The carria~e speed ;s adjusted so that the refire time is equal ~o 3t4 of an intra-dot scan cycle for quali~y printing~ If the refire time is 400 microseconds~ the 3~ 7 t~ ~
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carriage speed would be 18.75 inches/second~
Figure 4 is an enlarged illustrat;on of a word printed with various Letters as produced w;th the Figure 3 matrix. One can see by the layout o-f the dots 20 that 5 the qual;ty is at least as good as four pass, nine pin output. Using a 250Q Hz printhead, the speed of the intra-dot scan printer (twelve pins) would be 187.5 cps tdraft speed 500 cps~ for the four pass, nine pin printer. The speed advantage is obvious. If these same letters were made ~ith a 2sno Hz eighteen pin printhead with two passes~ the speed would be 120 cps ~draft speed SOOcps)~ A 1875 Hz twenty-four pin printhead would give the same speed and almost the same quality.
The advantage of the intra-dot scanning system of the present invention is that it gives the same performance as a twenty-four pin printhead ~ith, of course, far less parts and cost. It gives superior performance to both the nine pin and eighteen pin printhead used in a multipass printing system and does not have the stringent horizontal position indicator requ;rements. (For additional information see recent R.S. Sanders Patent No. 4~533,269.~ The intra-dot scanning system need not be sinuso;dal, although that or a triangular scan is near optimum and, therefore, preferred ;n most cases. To obtain a square wave, one preferred ~ethod comprises having the paper stationary during the hor;zontal scan and a stationary printhead during ~he vertical scanO Obviously, scan waves could ; be used that lie bet~een the trianglar wave and the sine ~ave and between the sine ~ave and the square waveO
The vertical scanning ~otion is given to the end o~
; the p1ns by moving the printhead 10 supporting the p;ns 12 plus or minus five mils at a frequ~ncy of ~875 Hz.
The mounting of the printhead 10 is made resonant at or near 1875 Hz to min;mize the driv;ng power. This .~ .
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frequency is der;ved by subdividing the matr1x pulses that deter~ine the matrix points a~d i5 phase adjusted so that one of the matrix pulses is synchronized with the top o~ the sign wave~ It is also ;mportant that the separation of the two rows of p;ns 12 is an exact multiple of the 1/96" horizontal motion during a single vertical scan.
Alternately, the entîre print rnechan;sm, generally ind;cated as 2~, can be moved so as to g;ve the desired motion to the end of the pins 12 either by rotating ths ~echanism 24 or mov;ng it vertically as an alternate to moving the printhead 10.
While dot ~atr;x printing using print w;res has been described above, the ;nvention is equally applicable to ink jet printers o~ the type described in "Printout"~
Vol. VIII~ No. 3, March, 1984. In this case the jet nozzle assem~ly is osc;llated to achieve the transverse scanning motion superimposed on the major scann;ng mot;onO
Scaling ~;th Dot Size If the dot size were reduced to twelve mils, the vert;cal scan would be plus or minus 3.75 mils and the horizontal mot;on for a vert;cal scan would be 7.5 ~ miLs. Th;s would increase the number of p;ns to ;~ 25 ~ixteen. If the refire time was then 333 micro seconds~
the carriage speed would be 17"1second. The letter quality (LQ~ speed wouLd be 170 cps. The design cons;deration being used ;s ~o keep the dot overlap in a 45 line at 1.8 of a dot diameter~ Vertical and horizontal lines would have a dot overlap of 3.8 of a dot diameter. Lines at intermediate angles or parts of curves would have dot overlaps that range between 3.8 of a dot and 1/8 of a dot with the fast majority at 3/8 dot d~ameter overlap~ If the dot is reduced to eight ~;ls or belo~, it is not necessary to overlap the dotsr , Between e;ght and twelve mil dots, the amount of overlay needs to be determined emp;rically.
Effect~v ~
The effective matrix size of the example of Figure 3 is 960/inch horizontally and somewhat variable in the vert;cal direction~ but worst case is 300/;nch vertically. Th;s is somewhat better vertically than a twenty-four pin head ~216/inch vertically) and equivalent to four pass~ nine pin printing (28R/inch verticallY)-It is re~atively easy to increase the matrix definition ~ith no reduction in printing speed and only minor penalties in electronic cost by doubling the number of fir;ng points. This gives a matri~ ;ze of lS 1920/jnch hor;zontally and 600/;nch verticaily. The only limitation to increasin~ the definit;on with synchronized intra-dot scanning or multipass printing ~s that the dot si~e ;s the mintmum ~ine width.
There i5 an ;mproved variat;on of the invont;on 1 deflection of the scan is ;ncreased to plus or minus 10 mils. The matrix then can be increased to t~enty points per cycle~ This ~ives a matrix size of 1920/;nch horizontaliy and 480t;nch vertically. This provides a hybrid inter-dot and intra-dot scan. Us;ng this technique, the possibLe matrix points are a lot more uniform~ When printing letter quality~ the carriage speed can be increased to 25"/second because of the increased interleav;ng. The ref;re time of 400 microseconds is one complete vert;cal scan. ~his increases the Letter qual;ty speed to 260 cps for ten ~¦ pitch and 325 cps for proport;onal Times Roman.
When the carriage ;s speeded up to 41.6 ;ps with pLus or m;nus 10 mils d~flection, a matrix size that is 960J;nch hor;Yontally and 430t;nch vert;cally can be ~ ' ' : ' : ' ' ' : .
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_ 9 _ achieved. This is a pure inter~dot scan in both directions~ The only limitation is that there is a reduced nu~ber of vertical pos;tions (i~e., two) that can print horizontal l;nes~ One must therefore reduce the point size of near letter quality (NLQ) or ;ncrease the number of pins by one or two pins.
When the speed is increased up to 83~2 ips, a matrix size of ~80Jinch hori~ontally and vertically ;s achieved. ~8 dpi draft characters ~hich uould be printed at 832 tten p;tch~ have a quality which is about the same as conventional 48 dpi draft characters. The only limita~ion is the reduced number of vert;cal positions that can print horizontal lines~ One must either reduce the po;nt s;ze of draft letters or ;ncrease the number of p;ns.
In summary, using a triangular scan with plus or minus 10 m;ls, letter quality is obtained at 260 cps (ten pitch) and 325 cps ~proportional~. Th;s is a four to one improvement over conventional four pass printing. Near letter quality is obtained at 416 cps ~ten pitch) and 520 cps (proportional), a three to one improvement. A 48 dp; draft at 830 cps ~ten pitch) gives a 1~3 to 1 improvement~ This also m;nimizes the registrat;on problems of multipass pr;nting and is, therefore, a s;gnificant improvement for that reason alone.
As can be seen9 the complete scanning cycle is longer than the dot d;ameter (;nter-dot scanning)~
However~ this embodiment shares with the intra~dot scanning system the common point of novelty of the present inventionr i.e~ a transverse scan imposed on the major scanning motion. When using inter-dot scann;n~, ¦
it is necessary to have the scanning cycle complete within about three or four dot diameters; otherwiseO the ability to achieve des;red quality of prlnting ~ill be ~ ~>7~
- lO -lost. Preferably, the inter-dot scanning is complete w;thin one and one-half to t~o cyclesa The few minor disadvantages of this embodime.nt are as follo~s: The printhead ;s tw~lve p;ns rather than S nine pins. Additionally, one actuator is needed for vertical scanning~ Thus~ there is an added cost of four pins and the associated pin driversa Due to the higher pin tip velocity~ there is also slightly higher dot position uncertainty and dot elongation~
There is an extension of the in~er-dot scanning as described above. ~y changing the angle of the transverse pin motion to slightly off ver~;cal~ the generally triangular path over the paper prev;ously described can be changed to a sa~t~oth path. This ~orks for e;ther direct;on of carriage travel~ although there : ~ould be minor changes ;n the front depend;ng on ~he direction of carriage travel. Just ~hich ;s more desirabLe ;n a given pr;nter des;gn depends on the detailed printer specif;cation~ ~a Figure 5 sho~s the preferred vertical scann;ng mechanism, generaLly indicated as 2~, to be used on one and two pin printers, and the l;ke. A T-shaped member 28 has the pr;nthead 10 mounted to the crossmember 30 of the "T". Also mounted thereto are two spring-b;ased : 25 soleno;ds 32 used to dr;ve the two print pins 12. The other end of the member 28 ;s mounted to p;vot pin 34 ~ith torsion spring 36 pass;n~ through the pin 3~ to : bias the ~ember 28 to a neutraL pos;tion from ~h;ch it Gan be oscillated in e;ther direction ~i~e~ up and down) by the drive solenoid 38~ The ~hole scanning mechanism 26 1s osciLlated by the dr;ve colenoid 38 to oscillate the printhead 10 to moue the pins 12. As mentioned above~ to create a sa~toothed scanning path, the p;vot : pin 34 is positioned slightly off of horizontal to make the plane of oscillation of the pr;nthead 10 slightly , ,:''' '. ~" ' ' , ~5;~ ~
off vertical. Tes~s have shown that with one pin, one can ach;eve speeds of 44 cps dra~tp fourteen cps La and that a two pin pr;nthead can ach;eve print speeds of 104 cps draft, 28 cps LQ ~ten pitch~ and 35 cps L~
~proportional).
A four pin pr;nthead is really a hybrid cross between the in-tra-dot scann;ng and the extra dot scanning of the one and two pin printers. Here, one can achieve 156 cps draft, 52 cps L~ (ten p;tch)o and ~5 cps LQ (proportional). The mechanism for vertical scann;ng could be as shown and described above.
Also poss;ble is a s;% pin printer w;th pLus or m;nus twenty mil vertical scanning. The print speed ach;evable ~ith this approach is 234 cps draft~ 78 cps LQ ~ten pitch) and 97 cps (proportional). The ssanning again is a some~hat different hybrid from the four pin scanning.
Serial Thermal Printer Using Synchronized Intra-Dot Scanning A serial thermal printer would be implemented ;n a very similar fash;on to the serial impact dot matri~ ¦
printer as described above. Several examples of such printers th~t can be modified in accordance w;th the present invention are shown on page 3 of the Kyocera brochure "~hin Film Thermal Pr;ntheads", CAT/1T8504FTK/2192E, and page 4 of "Printou~", Vol. VI~ i No~ 12, Dec., 1983 as well as "Printout", Vol. IX~ No.
9, Sept. 1985. The design of the printhead 10 of Figure 1 can be modified for use ~i~h a thermal printer ~ith twelve printing elements in place of the p;ns 12 being mounted ;n t~o rows of six ~ith the element centers twenty mils apart and staggered so that the ef~ectiYe element spacing is ten mils ~ith the vertical sinusoidal scanning being plus or minus 5 mils with a carriage moeiQn of ten mils and the printing elements producing a , .
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dot of sixteen mils diameter ~the "dot" could, of course, also be square or other convenient shapes even though a round dot is sho~n ;n the f;gures3. The intra--dat scanning could be triangularv square wave or any shape in-between, but s;nusoidal or triangular is nearly op-t;mum and~ therefore, preferred. Assuming the refire speed ~as six milliseconds, the carriage speed would be 13 ;nch~second~ The printing speed for high quality letters (ten pitch) would be 130 cps, which would be the same as a thirty-si~ pin printhead. The savings would be in using a twelve pin pr;nthead with the resulting elimination of the assoc;ated element drivers and electronics. In the case of a thermal printhead, however, the entire printhead would need to be rotated or moved vertically to obtain the desired scann;ng motion.
L;ne Thermal Printer or Electrostat;c Printer Using Synchronized Intra~dot Scanning . . . _ _ _ . . . ~ _ A line thermaL printer utilizes synchronized intra-dot scanning by impart;ng a sinusoidal horizontal motion to the pr;nthead as the paper is fed vertically, thus giving the desired path to the printing eLementsO
The printing elements would be two rows of printing elements. An example of such a line thermal printer that could be modified in accordance ~ith the present invention is shown on pages 4 and 5 of the above-mentioned Kyocera brochure. The printing elements would produce a dot sixteen m;ls in diameter tor square~
etc. as ment;oned above). The effective spacing of the 3Q printing elements is ten mils and the paper advances ten mils ~hrough one sinusoidal cycle. The effective matrix of such a configuration ;s 300/inch horizontaLly and 10001inch vertically Assuming the refire speed is eight milliseconds, the paper speed ~ould be 1"/second and the print speed would ,~ .
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- l3 -be 360 l;nes/minute. The savin~s would be the reduction in printing elements from 2000-4000 elem~nts to 1000 elements for a 10" printlineO
Electrostatic Printer An electrostati ~ cording to the present invention operates in much the same way as the previously described devices; that is, the printhead oscillating horizontally as the paper moves vertically~
An example Df such a printer that could be modified ;n accordance with the present invention is shown ;n Versatek 8ulletin No. 525-2, April 1984, describlng its V-80 pr;n~ers. The printhead would have a sinuso;dai motion as the paper is fed vertically~ The printing eLements wo~ld produce dots of sixteen mils in diameter~ The effective spacing of the pr;nting elements is ten mils and the paper advances ten mils through one sinusoidal cycle. The e~fective matr1x is 300/inch hori~ontally and 1000~inch verticalLy. The --intra-dot scanning could be triangular, square wave or almost any shape in-between, although s;nusoidal or triangular is, aga;n, nearly optimumy and therefore, preferred. The major saving would be the reduction in elements and the;r associated drivers from 2Dû0-4000 elements and drivers to 1000 elementsO
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Intra-dot scann;ng can improve Let~er quaLity print;ng by a factor of two over conventional methods in addition to improving the vertical matrix size. Using the technique~ draft printing is nearly doubled. Also, the intra-dot scanning allows the printer to compensate for continuous paper motion el;minat;ng the rap;d paper motion at the end of eaGh shuttle motion. This is accomplished by mod;fying the matrix patterns to take t into account continuous paper mot;on. Different ' .
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character PROMS are used for each character pos~tion and directions (onLy four combinations in a s;xty-eight pin printer). When th;s feature is used, throughput is ;ncreased as much as 50%~ For example~ a sixty-eight p;n ~13.6" line length) pr;nter sould print 2300 l;neslm;nute wh;le a t~elve pin (8" l;ne length~ printer could pr;nt 730 l;nes/m;nute. It also greatly reduces the cost of the paper handling mechanism in the printer.
Laser_Printers Using ~ Scannin~
In the case o~ a laser printer employing the present invention a technique sim;lar to that employed ~;th CRT
display ~to be described shortly) ;s used; that ;s, the beam is deflected vertically as the beam is swept horizontally so the beam makes a sinusoidal track across the drum. An example of such a printer that can be modified to utilize the present invention is shown in "Printout", Vol. IX, No. 6, June 1985, and "Printout"~
Vol. IX, No. 5, May 1985. If the dot size were ten , mils, the modulaticn would be swch that the beam deflec~ed plus or minus 3~5 mils vert;cally while the beam was moving horizontally 1/144~o The beam could be deflected by a vibrating m;rror in the light path~ In such case, the effective matrix would be 1500/inch horizon~ally by 480/inch Yertically.
The advantage of this method is that a larger size laser beam can be used, which could result in faster printing by a factor of t~o or three times. The intra-dot ssanning could be triangular~ square ~ave or almost any shape in-between although sinusoidal is nearly optimum, and therefore, preferred.
~h Emitting _ de (LED) or Liqu;d Cr~t-L D;~d- ~L~ Pri~er In LED tor LCD) printers tsuch as produced by Richo or IBM), synchronized intra-dot scanning would again `', : . ' ' ~', : ' ,5 ~ Jr~~3 ~ l~ ~
prov;de an advantage~ An example of such a printer that could be mod;fied ;n accordance w;th the present ;nvention is shown in "Printout", Vol. IX, No~ 10, October, 1985. Two rows of LED's (or lCD's) are empLoyed. Each LED or LCD makes a dot on the drun o~
sixteen mils diameter and the effective spacing is 1/96". The path the LED or LCD elements make on the drum is due to a s;nusoidal motion ;mparted to the LD
or LCD elements that move pLus or minus 50D m;ls s;nuso;dally as the drum moves 1/144". The e~fective matr;x is 480/inch horizontally and 1500/inch vert;cally.
The advantage of this over conventional LED or LCD
pr;nters is that it uses one-third or one-fourth the LED
or LCD eLements that the convent;onal LED or LCD
pr;nters use for the same matrix definition~ The print;ng speed would be increased by a factor of two or three. The intra-dot scann;ng couLd be tr;angular~
square wave or almost any shape ;n-between although s;nusoidal is nearly optimum~ and once~ again therefore, ~. 0 preferred.
Application to Imag;n~ S~stems While the present invent;on has been described initially in the context of ;ts use in dot matrix pr;nt;ng, the basic pr;ncipals and points of novelty involved can be utilized equally in image scanning as well as image print;ng, as ~ill now be discussed.
Scanner for Graphic_ Input to Synchronized ~ Intra dot Scannin~ _r _ters ln order to input graphic data into synchronized scanning printers, it is necessry to scan the graphic data in exactly the same way as the dots are printed.
Scanner for Serial Dot Matrix Printer or Serial Thermal Printer Us;ng ning In th;s case, -he scanning head consists of tweLve .
' - l6 -elements arranged ;n the same manner as the pins 12 in the pr;nthead 10 of Figure 1~ In the scanning caseO the eLements would be photo diodes~ for example~ ra~her than print pins. The elements are made to move vertically sinusoidally ~s the he3d moves hori~ontally so that the head scans plus or minus f;ve mils 35 the head moves 1/~6" mils horizontally. The scanning could be accomplished mechanically by moving or rotating the scann;ng head~ or~ it could be done optically.
During the scanning, the effect is to p;ck up horizontal lines as the scanner is moving vertically and vertical lines as the scanner moves horizontally. This type of scanner thus has a matrix def;nition of 960/inch horizontally by 300/inch verticaLly~
The intra-dot~(or inter-dot) scann;ng ~ust be identical to that used in print;ng~ Commerçial optical scanning systems wh;ch could be modified to utilize the present ;nvention are described in Richo ~ulletin, IS30 No. 8506-TA-8506, 8401, April, 1984.
Scanner S stem for L~ne Thermal or CCD Pr;nter Using Synchronized Intra-dot Scanning .~
In this case, the scanning head should match the printhead both in geometry and mot;on. As a result, the sranning elements should be as previously shown and ~he motion should be as previously described for the applicable associated pr;nthead.
Converting Standard Raster Graphics to Synchronized Intra-dot Scanni_~ Format - Assuming that standard raster graphics are in 30 sufficient detail to warrant it, the conversion to synchronized intra-dot scanning format can be made as part of a sof~ware program. ~asically, the method i5 as follows. The s~andard raster graph;cs (with a dot size to match the matrix size) ;s put ;nto a bit map windo~
35 ~hich progresses as the processin~ is completed. The .. "
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l7 -sof~ware moves a Larger doe (as used in synchronized scanner format) through the bit map on a scanning path that matches the synchronized scanning format until a match is obtained. So, basicallyf the software does wha~ ~as proposed in the physicaL scanner in the two previous paragraphs~ In the same way, it is poss;ble to convert from intra-dot scanning to inter-dot scanning.
Facs;mile System_Using ~y~
Intra-Dot Scann;ng Th;s system uses a synchroni~ed scanner for transm;tting a synchronized scanner printer for reception. A good combination would be the synchronized scanner described above with the thermaL line printer~
The major advantage is an increase in matrix definition (resuLt;ng in Letter quaLity output) with increased printer speed and no increase in transmission time using : 3 modified group 3 or 4 compression system. (For descript;on of such compression system, reference shouLd l be had to EIA standards).
n~er- and Intra-dot Scanning As ment;oned earl;er herein, the present invention ~ is as applicable to CRT type d;spLays as it ;s to ; print;ng on paper. In fact, it is in this area that the present ;nvention has, perhaps, its greatest potential.
Such use will now be described~
The electron beam is verticalLy deflected as it I scans horizontally as shown ;n F;gure ~. Assuming a spot size of fi~teen mils with a spacing between scans of sixty m;Ls, in moving along its path 41, the electron beam would be deflected sinusoidaLly plus or minus ~hirty mils while ~he beam was moving horizontally fifteen mils. The vertical beam deflect;on sho~n in Figure 6 is a sawtooth. This could very well be accomplished by a sinusoidaL deflection that was tilted .
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^~L~
~ l8 -to give a sawtooth-like pa~hO A sinuso;dal vertical deflection will give very sim;lar results. An alternate preferred method is sho~n in F;gure 6a us;ng stepped square wave modulat;on ~hich be~ter lum;nesce uniFormityO The hor;zontal scan;frequency ;s 15.6 KHz with about a ten ~;lliseco~d retrace. The vert;cal scar1n;ng frequency ;s s;xteen MHz. The beam deflect;on of plus or m;nus th;rty mils g;ves a non-interlaced display~ This requ;res a sixty-four MHz video. The result is a 1024 x 863 display~
In using an interlac~d display, the vert;cal deflection is reduced to plus or m;nus fifteen mils.
This reduces the video to thirty-two MH2 and the resul~
is still a 1024 x 860 display.
~y increas;ng the dot access frequency (consequently decreas;ng memory access time) the matr;x definition in both directions is ;ncreased. Thus, with 2 sixty-four -~
MHz dot access frequency, the result ;s a 2048 x 1720 display using interlaced scanning, although mini~um line width remains fifteen mils; however, the increased matrix s;ze w;ll perm;t letter quality fonts of the same quaLity as shown in Fi~ure 4 and eliminate the "jaggies"
in d;agonaLs and cur~ed lines in the graph;cs mode. j~
Inter- and Intra-dot Scanning Inter- and ;ntra-dot scanning in a CRT can be acco~pl;shed e;ther magnetically or electrostatic3lly, d~pend;ng on the type of CRT employed. If magnetically~
a separate small deflection coil 42 is mounted immediately after the electronic lens 44. It is preferable to resona~e ~he coil 42 with a capacitor 46 a~ the vertical scanning rate as illus~rated in F;gures 7 and 8~ I~ is not efficient to use the vertical deflection coils (not sho~n~ of the CRT itself. The - coil ~2 is ~oun~ed horizontally if sine waves are desired and off horizontal if pseudo-sawtooth scannirg '- ' . ~ ' .
as sho~n in Figure 9 is desired. The angle from horizontal 5~) is picked to match the horizontal scanning rate.
A preferable way to obtain inter and intra-dot scannlng in an electrostatic CRT is to use small electrostatic deflection plates 4g ;mmediately after the electronic focusirlg lens 44 as shown in Figures 10 and 11~ These plates 48 are placed vert;cally if sinuso;dal scanning is ~anted, or off vertical if pseudo-sa~tooth scann;ng is the desired result. Figure 12 illustrates pseudo-square Aave scanning if the sine wave driving the electrostatic plates is limited. This scanning is useful in some applications.
High Definition Pictures ~TV) If the p;cture ;s scanned in the same way as the monitor, definition of the resulting images can be improved in the same fashion~ This could be very useful in all the cases where current TV standards are not involved~ For example: photographic ima~es of aLl types, closed circuit TV, map projections, etc.
Vertical Def~nition Enhancement ~Apparent) of Televi_i_n Picture t A television picture is produced every one-thirtieth of a second by scanning each alternate line on a 25 television tube (CRT~ during the first one-sixtieth of a li second (i.el~ one-half of the picture); and, during the subsequent one-sixtieth of a second, scanning the lines intermedia~e ~hose scanned in the previous one-sixt1eth, with ~he second half of the pic~ureO This is a well-known and much-used technique known as 'interLacing"~
To improve the apparent vertical definition, it is desirable to scan all lines everyone-sixtieth of a s~cond~ The bLank intermediate scan lines could then be filled ;n by memoriz;ng a preceding line, comparin~ the .
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~ o data ;n that memory with the succeeding llne~ and then fill;ng the intermed;ate l;ne ~;th averaged, ;nterpolated, or otherw;se der;ved ;nformation. A
simple, less effective method normally employed simply repeats the scan l;ne twice.
There is much interest in improving the quality of ord;nary TV as transmitted by today's standards~ The major opportunity for qual;ty improvement results from elim;nating the above~descr;bed ;nterlace, which causes problems when the human eye moves vertiGally ~saccades) over the picture. For example, if you store an entire frame including the interlace~ combine the two, and then put the comb;ned picture on the tube at approx;mately 60 Hz~ you obta;n a much better qual;ty p;ctureu The major disadvantage of th;s is the expense~ Storing an ent;re frame and comb;n;ng ;t is still expensive to do electron;cally. Doubl;ng the hori7intal scan frequ~ncy is also expens;ve.
Another method that has been tried ;s to store one scan l;ne and then repeat the stored scan line ln tha ;nterlaced l;ne below. Th;s gives improvement, but not as much as the case where you combine the entire frame7 Further, it is st;ll relatively expens;ve because you must still double the horizontal scan frequency~
Using inter-dot scanning in various forms, one can dupl;cate or come close to these above-descr;bed ;mprovements; but, in a much less expensive way. The present invention achieves this not by doubling the hori~ontal scan to produce a complete picture every one-s;xtieth of a second; but, by a technique der;ved from ;nter-dot scanning in which the scanning electrode beam is caused to oscillate vertically with an amplitude equal to the space between adjacent scan lines and equal to the elec~ron beam diameter produc;ng the trace. By this means, the electron beam can produce picture - ~ ' 75~
information for one scan trace directly from the broadcast signal while on the peaks of its vertical oscillation and from deriYed informat;on from the preceding ~nd succeeding scan l;nes wh;le in the troughs of the oscillat;on. In th;s way, a single scan can produce ad~acent scan traces simultaneously, ~;th the electron beam being modulated to vary the intens;t;es as described~
The derived~ intermediate signal may be generated by storing, on the fly, one Line of scan information and comparing the s;gnal from the output of the store with the s;gnal on the input o~ the store ~the store being dynamic ;n that the stored ;nformation proceeds serially from the input to the output, i~e. a FIF0 store) and deriving ;ntermediate scan information from th;s.
Hence, the compared information will always be of sisnals synchronized vertically from preced;ng and succeeding scan lines.
The vertical oscillation of the electron beam may be of a sawtooth form whereby the scan line information of the preceding and intermediate scan lines are synchronized vertically one above the other essentially at the top and bottom of the vertical of the sawtooth form. The oscillation may be produced by the techniques of Figures 7 and 8 or Figures 10 and 11, as prev10usly described in detailO More detailed explanations ~ill now be provided~
Vertically scan the electron beam 40 sinuso;dalLy as in Figure 13 plus or minus one-half dot diameter at t~ice the maximum video frequency tsay seven to ten MHz)~ This produces a dot that is the same spot size horizontally, but tu;ce as high vertically. O~her than t~is, leave th~ monitor the same as before. This does the same th;ng as storing one scan line and repeating .
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the scan line in the interlaced line belo~. ~owever, lt does not need to store a line nor does it double the horizontal frequency. The disadvantage of this scheme is that the top and bottom horizontal lines ~ill act as follows. Assume top of horizontal contrast shift starts on an interlaced line. Extending donn the non-interlaced line above gives no intensity where there should be such~ The interlaced frame line gives the proper ;ntensity. So, the net result is that the top of hori20ntal edges are at one-half of proper intensity and blinking at the thirty H2 interlace rate. The same effect takes place at the bottom of the horizontal edge, The diagonal edges develop a sort of f~z7y/jagyy effect for the same reason. This technique ~;ll, ho~ever, fill ;n uertical l;nes. The apparent improvement takes place because much less of the picture is blinking at the thirty Hz ;nterlace rate~
Method 2 - Increased Picture $morovement Vertically scan the beam s;nuso;dally as in Figure 13 plus or minus one-half diameter at the maximum video frequency in a synchronized manner during the hor;zontal scan. Store one scan line on a CCD ch;p (such as the Fairchild CCD321A). Derive the interlace line by averaging the first and second ;nterlaced lines;combine the ori~inal in the derived inter`laced line so that a video synchronized signal that records the first line and the f;rst interlaced line on the face of the tube ;n one hori~ontal scan is obtained. This process is ~, repeated for the entire frame for one sixtieth of a second. When the interlaced frame comes up, ths ; forego;ng process is repeaeed. The superimposed p;cture resulting therefrom should be much improved.
Just how much better the picture actually is depends on the quality of the interpola~ion between the t~o scans. The simplest scheme is to average the intensi~y ' . .
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oF adjacent vertical pix~ls. The d;sadvantage of th;s scheme ;s similar to Method 1, described above. The effect on horizontal and diagonal l;nes is the same as Method 1~ except the edge ;ntensity ;s three-fourths of the proper value tas opposed to one-half); and, it still blinks at the ;nterlace rate of th;rty H~
Method 3 - Maximum P;cture Improvement The best technique is to compare three adjacent horizontal pixels on one scan ~;th three adjacent hor;zontal pixels immediately belo~ on the second scan as sho~n in Figure 14. I~ p;xel H1 ;s the same ;ntensity as pixel B2~ we make B12 the same intens1ty.
If B1 and ~2 are not the same ;ntensity, we make B12 the average of ~he two intens;ties unless A1 intensity is the same as C2, ;n ~hich case we make ~12 the same intensity as A1 or C2. In a similar manner, ;f A2 is the same intensity as C1~ we make 812 the same intens;ty. The advantage of th;s method over Method 1 ;s that most diagonal edges are continued almost perfectly. Horizontal fuzziness should be about the same as Method 2.
In Methods 2 and 3, special circuitry is needed to interpolate between horizontal scans. Figures 15 and 16 show in block d;agram form two circuits tha~ could b~
employed to perform this interpolation. figure 15 shows a CCD32A chip 50 connec~ecl wi~h a multiplexer 52 to provide th~ video signal synchronized with the vertical pseudo-square wave scanning for Method 2c The CCD321A
chip S0 ;s connected in series mode providing 910 bits of analog shift register~ After one horizontal sweep is stored in the CCD321A, the timing signals are such that the correspond;ng b;t of the subsequent horizontaL scan signal is going into the CCD321A as the corresponding bit of the previous horizontaL scan signal is going out .
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of it~ By ~verag;ng the correspond;ng b;ts, one can obta;n the ;nterpolated ;nterlaced s;gnal that ;s desired~ The video signal to the CRT at 54 is the result;ng of the multiplexer 52 multiplexing between the prev;ous horizontal scan signal and the ;nterpolated interlaced s;gnal at the ;nter-dot scanning frequency.
It should be noted that when us;ng this techn;que~ the s;gnals appear on line 54 to the CRT one hor;zontal scan line late.
To accompl;sh Method 3, the more complicated c1rcu1t shown in F;gure 16 must be used. In th;s case, a spec;al modified CCD321A ch;p 50 wh;ch makes available the f;rst three bits of the incoming s;gnal and the last three bits in memory ;s used. Here, again, the timing is such that there are three corresponding bits of two adjacent horizontal scan signals. These are fed to a special logic chip 56 which includes three comparators and which includes logic to perform ~he steps of Method 3~ The output is aga;n multiplexed by the multiplexer --52 ~t the scanning freq~ency and fed to the CRT on output line 54. HereO aga;n, the picture displayed is one scan line late.
Method ~
Still another embodiment of the invention is shown in Fig. 17 ~hich is a schematic circuit diagram showing a modif;ed digital TV system. With the advantage of 1/2 frame and full frame digital storage, Fig~ 17 shows ho~
to eLiminate any interpolation and elim;nate the ;nterlaced scan us;ng a standard TV transmission.
The video s;gnal goes into a 1/2 frame store and ~e multiplex the incoming signal ~;th the signal delayed 1/2 frame as shown by the diagram at ~he bottom of Figure 17. This gives a non-interlaced picture with no interpolation. If we add the interpolation used by Method 2 or 3, we can double the number of displayed .' ' ~ ' .:
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l;nes ~ithout interlace by us;ng the scan pattern shown on F;gure 6A still only using standard TV transm;ssions and only 15.6 KHz horizontal scan.
Pro~ection_TV
Projection TV us;ng three tubes of different colors will operate as ~escribed above as there are no complicati~ns oF color shadow masks or trinitron aperature ~rilles.
~d~
In order to make sure that we don't have to match the vertical scan ~ith the shadow mask holes, ue must use a vertical scanning frequency twice the frequency which the horizontal scan intercepts the shadow mask~
Th;s insures that the beams hit the mask as well as they do w;thout any vertical scanning. Its disadvantage is that the final video amplifier must be quadruple the band ~idth and the beam current must be larger to compensate for the shorter time the beam is in the shadow mask. If we use the pseudo-square wa~e scanning trequ;rin~ eLectrostat;c deflection as in Figure 10 and 11) as iLlustrated in F;gure 1Z, ~e minimize the ;ncrease injbeam current required. With double the shado~ mask frequency, ~e get half the beam current on ~he phosphor in one horizontal scan as compared to ~he current if we were not inter-dot scanning; however, since we pain~ each line twice as much, the beam current required remains about the same.
Tr ini ~ , ~ [~
When using a trin;tron type color tube, ~he inter-dot scanning ~requency should be equal to tw;ce the frequency at w~ich the hori20ntal scan lntercepts the aperature grill. Pseudo-square wave modulation as ;n f;gure 12 should also be used again. Once again, we ~et half the beam current pn the phosphor in each ~, . .
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5;~4 horizontal scan; but, because we have tw;ce the scan, there is no appreciabLe increase ln beam current required.
Wherefore, having thus described my invent~on~ I
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B_ckqr_und _f the Invention The presen~ invention xelates to raster scanniny systems such as dot ma-trix printers, televisions, CRT
monitors, and the like.
Many devices use a so-called "raster" scanning system. These include dot matrix prin~ers and cathode ray tube (CRT) displays such as used in television sets and computer monitors. In any raster device, a dot-producing entity moves across the display area repeatedly on a line-by-line basis. In a printer/ it is a printhead moving across the paper. With the CRT, it is an electron beam moving across the phosphors of the CRT screen.
There are two dot matrix principles used in dot matrix print-ers today. One uses a matrix which is approximately equal to the dot size. The second uses a dot size that is up to ten times larger than the matrix.
As used herein, "Matrix" means the spacing between the possible dot positions or the number of possible dot positions per inch horizontally and vertically.
All quality printing by impact dot matrix printers uses a dot size considerably larger than the matrix.
While in the draft mode, the dot size and the matrix are usually approximately the same.
Quality printing is generally performed by using a seven to nine pin printhead and using multiple passes of the printhead while moving the printhead or paper a fraction of a dot between passes (Reference: R.C.
Sanders Patent No. ~,159,882). Another method currently used is to use eighteen to twenty-four pins arranged in two or three staggered rows. At the same time, the matrix used for firing pins during the horizontal sweep of the carriage is a fraction of a dot width.
Most thermal and laser printers use a dot size equal to the matrix, while ink jet printers have been designed both ways. Most, if not all, CRT monitors use a dot size equal to the matrix size. The new improved CRT monitors will use dot sizes that are equal to the matrix size as ~ 7 ,~
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well as dot sizes that are much larger than the matrix size.
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This invention is based on using a dot size much larger than the ma-trix size regardless of the type of device. To achieve scanning by a dot matrix printing system accoxding to the present invention, the printing means is moved relative to the recording means with a scanning motion having a major direction and means are provided for imposing on the scanning motion a cyclical variation in the direction of the motion transverse to its major direction. In one preferred form of the invention (intra dot scanning), the cyclical variation completes at least one cycle during a scan equal to the dot size. The cyclical scan has a duration equal to or longer than the dot refire time and an integral number of dots can be created at predetermined points along the cyclical path. In order to minimize confusion, the application of this principle to various types o~
~0 printers is described separately in the following detailed description. The use of the present invention with CRT monitors is then addressed. Where dimensions and performance capabilities are given, they are by way of example only and reflect tested modifications of actual devices performed by applicant herein.
In accordance with one aspect of the present invention, there is provided a raster scanning system comprising: (a) means Eor repeatedly sweeping an image producing means across a display medium to produce a series of sweeps for the creation of visual images in said series of sweeps; (b) deflection means for cyclically deflecting the image producing means in a direction substantially normal to the sweep direction in a repetitive series of like oscillations throughout each image producing sweep across the display medium; (c) means for controlling the image producing means to vary the brightness of pixels created; (d) means for supplying a first image information signal synchronized with said repetitive series of oscillations to con~rol the controlling means to produce vlsual image information on said display medium at one set of desired S corresponding locations on each of desired ones of the oscillations during a the sweep; and (e) means for supplying at least a second image information siynal synchronized with the repetitive series of oscillations to control the controlling means to produce visual image information on said display medium at another set of desired corresponding locations on each of desired ones of said oscillations during the said sweep.
In accordance with another aspect of the present invention, there is provided a cathode ray tube display such as a computer monitor, television, or the like including a raster scanning system having a source of an int~nsity controllable electron beam and a main means for deflecting the beam to create a series of horizontal sweeps of the beam from the top to the bottom of a 2~ display screen for selectively creating a series of pixel dots in a series of parallel rows comprising: (a) deflection means for deflecting the dot creating means in a direction substantially normal to the sweep direction;
(b) drive means operably connectad to the deflection means for cyclically deflecting the dot-producing means in a repetitive pattern throughout each dot-producing sweep across the display medium, the driving means comprising a signal producing means for applying a repetitive electrical signal to the deflection means to produce a peak to peak amplitude of the pattern which is equal to the spacing between horizontal sweeps; and (c) means for providing an image information signal synchronized with the repetitive pattern to control said intensity controllable electron beam to generate two parallel image lines for each sweep.
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-- 3a -Descri~L~ L~ ~LZ ~lls Figure 1 is an end view of one type of dot matrix S printhead that can be used with the present invention.
Figure 2 is a side view of the printhead o-f Figure 1 showing the means for oscillating the printhead transversely to the major scanning direction.
Figure 3 is an enlarged schematic diagram of the path of the print pins across the paper for the printhead oE Figures 1 and 2.
Figure 4 is an enlarged view of typical type font like characters producsd by the printhead of Figures 1 and 2 when moved through the path of Figure 3 according lS to the technique of the present invention.
Figure 5 is a side view of a vertical scanning mechanism for one and two pin prin-ters employing the ~,7 pres~nt invent;on~
Figure 6 ;s an enlarged schemat;c diagram of the path of ~he electron beam scan in a CRT for a 1~'~
computer ~onitor when operated according to the present 5 invent;on.
Figures 7 and 8 are front and top v;ews~
respectively, of a magnetic CRT adapted to operate according to the present ;nvention.
Figure 9 is an enlarged schematic diagram of the path of the electcon beam scan in a CRT according to the presen~ invention when using offset deflection to obtain pseudo sawtooth scanning~
Figures 10 and 11 are front and side vie~s, respectively, of an electrostatic CRT adapted to operate according to the present invention.
Figure 12 is an enlarged schematic diagram of the path of the electron beam scan in a CRT according to the present invention when using a clippéd sine wave with electrostat;c deflection to obtain pseudo square ~ave Scanning Figure 13 is an enlarged schematic diagram of the path of the electron beam scan in a CRT according to the present invention during hor;zontal scan ~ith fractional scan shown.
F;gure 14 is a diagram of a group of adjacent pixels in a CRT.
Figures 15 and 16 are block diagrams of circuits according to the present invention for interpolating between horizontal scans in a CRT~
F;gure 17 is a block diayram of another embodiment of the invention~
~ I
Serial Impact Dot Matri~ Pr;nter Using A twelve pin printhead 10 ;s used in th;s first :
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~ 5 example arranged in two ro~s of six p;ns 12 as sho~n in F;gure 1. The vert;cal spacing of the p;n centers is 1/~8" irl each row and d~e~ to the staggeringD the e~fective spacing between the p;n centers is appro~imate~y 1/96". The pin d;ameter ;s1/72" and the dot diameter made on the paper is sixteen mils. If the p;n diameter is reduced or increased, it is important to scale the above dimensions as well as to increase or decrease the number of pins in the printhead.
The ends of the pins are moved ;n sinusoidal fashion five mils as the carriage (not shown) is moved hori20ntally across the paper. Referring to F;gure 2, this notion is created by driver 14 operatin~ on the pr;nthead 10~ Since the printhead 10 is supported on a frame 18 by spr;ng means 1b, the printhead ~;ll oscillate at a freqlJency controlled by the drive and the spring mount~ One cycie is made every time the carriage is moved 1/96" horizontally~ The perm;ss;ble firing points (;.e. the matrix) are approx;mately ten points --equally div;ded ;n time for every complete vert~cle sine wave cycle. This gives a matrix size of 9601;nch horizontally and about 300/inch vertically. It should be obvious to one skilled in the art that the intra-dot scanning cycle could be divided into a lesser or greater number of permissible firing points, say six to t~enty po;nts. It is ;mportant that there be an integral number of fir;ng points per intra-dot scanning cycle~
The motion of the end of the pins for a twelYe p;n pr;nthead ;s shown ;n Figure 3. A typical dot as produced by the pins 12 is indicated as 20 while the sinusoidal path traversed by each of the pins 12 as the carriage moves across the paper is indicated as 22~ The carria~e speed ;s adjusted so that the refire time is equal ~o 3t4 of an intra-dot scan cycle for quali~y printing~ If the refire time is 400 microseconds~ the 3~ 7 t~ ~
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carriage speed would be 18.75 inches/second~
Figure 4 is an enlarged illustrat;on of a word printed with various Letters as produced w;th the Figure 3 matrix. One can see by the layout o-f the dots 20 that 5 the qual;ty is at least as good as four pass, nine pin output. Using a 250Q Hz printhead, the speed of the intra-dot scan printer (twelve pins) would be 187.5 cps tdraft speed 500 cps~ for the four pass, nine pin printer. The speed advantage is obvious. If these same letters were made ~ith a 2sno Hz eighteen pin printhead with two passes~ the speed would be 120 cps ~draft speed SOOcps)~ A 1875 Hz twenty-four pin printhead would give the same speed and almost the same quality.
The advantage of the intra-dot scanning system of the present invention is that it gives the same performance as a twenty-four pin printhead ~ith, of course, far less parts and cost. It gives superior performance to both the nine pin and eighteen pin printhead used in a multipass printing system and does not have the stringent horizontal position indicator requ;rements. (For additional information see recent R.S. Sanders Patent No. 4~533,269.~ The intra-dot scanning system need not be sinuso;dal, although that or a triangular scan is near optimum and, therefore, preferred ;n most cases. To obtain a square wave, one preferred ~ethod comprises having the paper stationary during the hor;zontal scan and a stationary printhead during ~he vertical scanO Obviously, scan waves could ; be used that lie bet~een the trianglar wave and the sine ~ave and between the sine ~ave and the square waveO
The vertical scanning ~otion is given to the end o~
; the p1ns by moving the printhead 10 supporting the p;ns 12 plus or minus five mils at a frequ~ncy of ~875 Hz.
The mounting of the printhead 10 is made resonant at or near 1875 Hz to min;mize the driv;ng power. This .~ .
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frequency is der;ved by subdividing the matr1x pulses that deter~ine the matrix points a~d i5 phase adjusted so that one of the matrix pulses is synchronized with the top o~ the sign wave~ It is also ;mportant that the separation of the two rows of p;ns 12 is an exact multiple of the 1/96" horizontal motion during a single vertical scan.
Alternately, the entîre print rnechan;sm, generally ind;cated as 2~, can be moved so as to g;ve the desired motion to the end of the pins 12 either by rotating ths ~echanism 24 or mov;ng it vertically as an alternate to moving the printhead 10.
While dot ~atr;x printing using print w;res has been described above, the ;nvention is equally applicable to ink jet printers o~ the type described in "Printout"~
Vol. VIII~ No. 3, March, 1984. In this case the jet nozzle assem~ly is osc;llated to achieve the transverse scanning motion superimposed on the major scann;ng mot;onO
Scaling ~;th Dot Size If the dot size were reduced to twelve mils, the vert;cal scan would be plus or minus 3.75 mils and the horizontal mot;on for a vert;cal scan would be 7.5 ~ miLs. Th;s would increase the number of p;ns to ;~ 25 ~ixteen. If the refire time was then 333 micro seconds~
the carriage speed would be 17"1second. The letter quality (LQ~ speed wouLd be 170 cps. The design cons;deration being used ;s ~o keep the dot overlap in a 45 line at 1.8 of a dot diameter~ Vertical and horizontal lines would have a dot overlap of 3.8 of a dot diameter. Lines at intermediate angles or parts of curves would have dot overlaps that range between 3.8 of a dot and 1/8 of a dot with the fast majority at 3/8 dot d~ameter overlap~ If the dot is reduced to eight ~;ls or belo~, it is not necessary to overlap the dotsr , Between e;ght and twelve mil dots, the amount of overlay needs to be determined emp;rically.
Effect~v ~
The effective matrix size of the example of Figure 3 is 960/inch horizontally and somewhat variable in the vert;cal direction~ but worst case is 300/;nch vertically. Th;s is somewhat better vertically than a twenty-four pin head ~216/inch vertically) and equivalent to four pass~ nine pin printing (28R/inch verticallY)-It is re~atively easy to increase the matrix definition ~ith no reduction in printing speed and only minor penalties in electronic cost by doubling the number of fir;ng points. This gives a matri~ ;ze of lS 1920/jnch hor;zontally and 600/;nch verticaily. The only limitation to increasin~ the definit;on with synchronized intra-dot scanning or multipass printing ~s that the dot si~e ;s the mintmum ~ine width.
There i5 an ;mproved variat;on of the invont;on 1 deflection of the scan is ;ncreased to plus or minus 10 mils. The matrix then can be increased to t~enty points per cycle~ This ~ives a matrix size of 1920/;nch horizontaliy and 480t;nch vertically. This provides a hybrid inter-dot and intra-dot scan. Us;ng this technique, the possibLe matrix points are a lot more uniform~ When printing letter quality~ the carriage speed can be increased to 25"/second because of the increased interleav;ng. The ref;re time of 400 microseconds is one complete vert;cal scan. ~his increases the Letter qual;ty speed to 260 cps for ten ~¦ pitch and 325 cps for proport;onal Times Roman.
When the carriage ;s speeded up to 41.6 ;ps with pLus or m;nus 10 mils d~flection, a matrix size that is 960J;nch hor;Yontally and 430t;nch vert;cally can be ~ ' ' : ' : ' ' ' : .
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_ 9 _ achieved. This is a pure inter~dot scan in both directions~ The only limitation is that there is a reduced nu~ber of vertical pos;tions (i~e., two) that can print horizontal l;nes~ One must therefore reduce the point size of near letter quality (NLQ) or ;ncrease the number of pins by one or two pins.
When the speed is increased up to 83~2 ips, a matrix size of ~80Jinch hori~ontally and vertically ;s achieved. ~8 dpi draft characters ~hich uould be printed at 832 tten p;tch~ have a quality which is about the same as conventional 48 dpi draft characters. The only limita~ion is the reduced number of vert;cal positions that can print horizontal lines~ One must either reduce the po;nt s;ze of draft letters or ;ncrease the number of p;ns.
In summary, using a triangular scan with plus or minus 10 m;ls, letter quality is obtained at 260 cps (ten pitch) and 325 cps ~proportional~. Th;s is a four to one improvement over conventional four pass printing. Near letter quality is obtained at 416 cps ~ten pitch) and 520 cps (proportional), a three to one improvement. A 48 dp; draft at 830 cps ~ten pitch) gives a 1~3 to 1 improvement~ This also m;nimizes the registrat;on problems of multipass pr;nting and is, therefore, a s;gnificant improvement for that reason alone.
As can be seen9 the complete scanning cycle is longer than the dot d;ameter (;nter-dot scanning)~
However~ this embodiment shares with the intra~dot scanning system the common point of novelty of the present inventionr i.e~ a transverse scan imposed on the major scanning motion. When using inter-dot scann;n~, ¦
it is necessary to have the scanning cycle complete within about three or four dot diameters; otherwiseO the ability to achieve des;red quality of prlnting ~ill be ~ ~>7~
- lO -lost. Preferably, the inter-dot scanning is complete w;thin one and one-half to t~o cyclesa The few minor disadvantages of this embodime.nt are as follo~s: The printhead ;s tw~lve p;ns rather than S nine pins. Additionally, one actuator is needed for vertical scanning~ Thus~ there is an added cost of four pins and the associated pin driversa Due to the higher pin tip velocity~ there is also slightly higher dot position uncertainty and dot elongation~
There is an extension of the in~er-dot scanning as described above. ~y changing the angle of the transverse pin motion to slightly off ver~;cal~ the generally triangular path over the paper prev;ously described can be changed to a sa~t~oth path. This ~orks for e;ther direct;on of carriage travel~ although there : ~ould be minor changes ;n the front depend;ng on ~he direction of carriage travel. Just ~hich ;s more desirabLe ;n a given pr;nter des;gn depends on the detailed printer specif;cation~ ~a Figure 5 sho~s the preferred vertical scann;ng mechanism, generaLly indicated as 2~, to be used on one and two pin printers, and the l;ke. A T-shaped member 28 has the pr;nthead 10 mounted to the crossmember 30 of the "T". Also mounted thereto are two spring-b;ased : 25 soleno;ds 32 used to dr;ve the two print pins 12. The other end of the member 28 ;s mounted to p;vot pin 34 ~ith torsion spring 36 pass;n~ through the pin 3~ to : bias the ~ember 28 to a neutraL pos;tion from ~h;ch it Gan be oscillated in e;ther direction ~i~e~ up and down) by the drive solenoid 38~ The ~hole scanning mechanism 26 1s osciLlated by the dr;ve colenoid 38 to oscillate the printhead 10 to moue the pins 12. As mentioned above~ to create a sa~toothed scanning path, the p;vot : pin 34 is positioned slightly off of horizontal to make the plane of oscillation of the pr;nthead 10 slightly , ,:''' '. ~" ' ' , ~5;~ ~
off vertical. Tes~s have shown that with one pin, one can ach;eve speeds of 44 cps dra~tp fourteen cps La and that a two pin pr;nthead can ach;eve print speeds of 104 cps draft, 28 cps LQ ~ten pitch~ and 35 cps L~
~proportional).
A four pin pr;nthead is really a hybrid cross between the in-tra-dot scann;ng and the extra dot scanning of the one and two pin printers. Here, one can achieve 156 cps draft, 52 cps L~ (ten p;tch)o and ~5 cps LQ (proportional). The mechanism for vertical scann;ng could be as shown and described above.
Also poss;ble is a s;% pin printer w;th pLus or m;nus twenty mil vertical scanning. The print speed ach;evable ~ith this approach is 234 cps draft~ 78 cps LQ ~ten pitch) and 97 cps (proportional). The ssanning again is a some~hat different hybrid from the four pin scanning.
Serial Thermal Printer Using Synchronized Intra-Dot Scanning A serial thermal printer would be implemented ;n a very similar fash;on to the serial impact dot matri~ ¦
printer as described above. Several examples of such printers th~t can be modified in accordance w;th the present invention are shown on page 3 of the Kyocera brochure "~hin Film Thermal Pr;ntheads", CAT/1T8504FTK/2192E, and page 4 of "Printou~", Vol. VI~ i No~ 12, Dec., 1983 as well as "Printout", Vol. IX~ No.
9, Sept. 1985. The design of the printhead 10 of Figure 1 can be modified for use ~i~h a thermal printer ~ith twelve printing elements in place of the p;ns 12 being mounted ;n t~o rows of six ~ith the element centers twenty mils apart and staggered so that the ef~ectiYe element spacing is ten mils ~ith the vertical sinusoidal scanning being plus or minus 5 mils with a carriage moeiQn of ten mils and the printing elements producing a , .
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dot of sixteen mils diameter ~the "dot" could, of course, also be square or other convenient shapes even though a round dot is sho~n ;n the f;gures3. The intra--dat scanning could be triangularv square wave or any shape in-between, but s;nusoidal or triangular is nearly op-t;mum and~ therefore, preferred. Assuming the refire speed ~as six milliseconds, the carriage speed would be 13 ;nch~second~ The printing speed for high quality letters (ten pitch) would be 130 cps, which would be the same as a thirty-si~ pin printhead. The savings would be in using a twelve pin pr;nthead with the resulting elimination of the assoc;ated element drivers and electronics. In the case of a thermal printhead, however, the entire printhead would need to be rotated or moved vertically to obtain the desired scann;ng motion.
L;ne Thermal Printer or Electrostat;c Printer Using Synchronized Intra~dot Scanning . . . _ _ _ . . . ~ _ A line thermaL printer utilizes synchronized intra-dot scanning by impart;ng a sinusoidal horizontal motion to the pr;nthead as the paper is fed vertically, thus giving the desired path to the printing eLementsO
The printing elements would be two rows of printing elements. An example of such a line thermal printer that could be modified in accordance ~ith the present invention is shown on pages 4 and 5 of the above-mentioned Kyocera brochure. The printing elements would produce a dot sixteen m;ls in diameter tor square~
etc. as ment;oned above). The effective spacing of the 3Q printing elements is ten mils and the paper advances ten mils ~hrough one sinusoidal cycle. The effective matrix of such a configuration ;s 300/inch horizontaLly and 10001inch vertically Assuming the refire speed is eight milliseconds, the paper speed ~ould be 1"/second and the print speed would ,~ .
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- l3 -be 360 l;nes/minute. The savin~s would be the reduction in printing elements from 2000-4000 elem~nts to 1000 elements for a 10" printlineO
Electrostatic Printer An electrostati ~ cording to the present invention operates in much the same way as the previously described devices; that is, the printhead oscillating horizontally as the paper moves vertically~
An example Df such a printer that could be modified ;n accordance with the present invention is shown ;n Versatek 8ulletin No. 525-2, April 1984, describlng its V-80 pr;n~ers. The printhead would have a sinuso;dai motion as the paper is fed vertically~ The printing eLements wo~ld produce dots of sixteen mils in diameter~ The effective spacing of the pr;nting elements is ten mils and the paper advances ten mils through one sinusoidal cycle. The e~fective matr1x is 300/inch hori~ontally and 1000~inch verticalLy. The --intra-dot scanning could be triangular, square wave or almost any shape in-between, although s;nusoidal or triangular is, aga;n, nearly optimumy and therefore, preferred. The major saving would be the reduction in elements and the;r associated drivers from 2Dû0-4000 elements and drivers to 1000 elementsO
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Intra-dot scann;ng can improve Let~er quaLity print;ng by a factor of two over conventional methods in addition to improving the vertical matrix size. Using the technique~ draft printing is nearly doubled. Also, the intra-dot scanning allows the printer to compensate for continuous paper motion el;minat;ng the rap;d paper motion at the end of eaGh shuttle motion. This is accomplished by mod;fying the matrix patterns to take t into account continuous paper mot;on. Different ' .
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character PROMS are used for each character pos~tion and directions (onLy four combinations in a s;xty-eight pin printer). When th;s feature is used, throughput is ;ncreased as much as 50%~ For example~ a sixty-eight p;n ~13.6" line length) pr;nter sould print 2300 l;neslm;nute wh;le a t~elve pin (8" l;ne length~ printer could pr;nt 730 l;nes/m;nute. It also greatly reduces the cost of the paper handling mechanism in the printer.
Laser_Printers Using ~ Scannin~
In the case o~ a laser printer employing the present invention a technique sim;lar to that employed ~;th CRT
display ~to be described shortly) ;s used; that ;s, the beam is deflected vertically as the beam is swept horizontally so the beam makes a sinusoidal track across the drum. An example of such a printer that can be modified to utilize the present invention is shown in "Printout", Vol. IX, No. 6, June 1985, and "Printout"~
Vol. IX, No. 5, May 1985. If the dot size were ten , mils, the modulaticn would be swch that the beam deflec~ed plus or minus 3~5 mils vert;cally while the beam was moving horizontally 1/144~o The beam could be deflected by a vibrating m;rror in the light path~ In such case, the effective matrix would be 1500/inch horizon~ally by 480/inch Yertically.
The advantage of this method is that a larger size laser beam can be used, which could result in faster printing by a factor of t~o or three times. The intra-dot ssanning could be triangular~ square ~ave or almost any shape in-between although sinusoidal is nearly optimum, and therefore, preferred.
~h Emitting _ de (LED) or Liqu;d Cr~t-L D;~d- ~L~ Pri~er In LED tor LCD) printers tsuch as produced by Richo or IBM), synchronized intra-dot scanning would again `', : . ' ' ~', : ' ,5 ~ Jr~~3 ~ l~ ~
prov;de an advantage~ An example of such a printer that could be mod;fied ;n accordance w;th the present ;nvention is shown in "Printout", Vol. IX, No~ 10, October, 1985. Two rows of LED's (or lCD's) are empLoyed. Each LED or LCD makes a dot on the drun o~
sixteen mils diameter and the effective spacing is 1/96". The path the LED or LCD elements make on the drum is due to a s;nusoidal motion ;mparted to the LD
or LCD elements that move pLus or minus 50D m;ls s;nuso;dally as the drum moves 1/144". The e~fective matr;x is 480/inch horizontally and 1500/inch vert;cally.
The advantage of this over conventional LED or LCD
pr;nters is that it uses one-third or one-fourth the LED
or LCD eLements that the convent;onal LED or LCD
pr;nters use for the same matrix definition~ The print;ng speed would be increased by a factor of two or three. The intra-dot scann;ng couLd be tr;angular~
square wave or almost any shape ;n-between although s;nusoidal is nearly optimum~ and once~ again therefore, ~. 0 preferred.
Application to Imag;n~ S~stems While the present invent;on has been described initially in the context of ;ts use in dot matrix pr;nt;ng, the basic pr;ncipals and points of novelty involved can be utilized equally in image scanning as well as image print;ng, as ~ill now be discussed.
Scanner for Graphic_ Input to Synchronized ~ Intra dot Scannin~ _r _ters ln order to input graphic data into synchronized scanning printers, it is necessry to scan the graphic data in exactly the same way as the dots are printed.
Scanner for Serial Dot Matrix Printer or Serial Thermal Printer Us;ng ning In th;s case, -he scanning head consists of tweLve .
' - l6 -elements arranged ;n the same manner as the pins 12 in the pr;nthead 10 of Figure 1~ In the scanning caseO the eLements would be photo diodes~ for example~ ra~her than print pins. The elements are made to move vertically sinusoidally ~s the he3d moves hori~ontally so that the head scans plus or minus f;ve mils 35 the head moves 1/~6" mils horizontally. The scanning could be accomplished mechanically by moving or rotating the scann;ng head~ or~ it could be done optically.
During the scanning, the effect is to p;ck up horizontal lines as the scanner is moving vertically and vertical lines as the scanner moves horizontally. This type of scanner thus has a matrix def;nition of 960/inch horizontally by 300/inch verticaLly~
The intra-dot~(or inter-dot) scann;ng ~ust be identical to that used in print;ng~ Commerçial optical scanning systems wh;ch could be modified to utilize the present ;nvention are described in Richo ~ulletin, IS30 No. 8506-TA-8506, 8401, April, 1984.
Scanner S stem for L~ne Thermal or CCD Pr;nter Using Synchronized Intra-dot Scanning .~
In this case, the scanning head should match the printhead both in geometry and mot;on. As a result, the sranning elements should be as previously shown and ~he motion should be as previously described for the applicable associated pr;nthead.
Converting Standard Raster Graphics to Synchronized Intra-dot Scanni_~ Format - Assuming that standard raster graphics are in 30 sufficient detail to warrant it, the conversion to synchronized intra-dot scanning format can be made as part of a sof~ware program. ~asically, the method i5 as follows. The s~andard raster graph;cs (with a dot size to match the matrix size) ;s put ;nto a bit map windo~
35 ~hich progresses as the processin~ is completed. The .. "
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l7 -sof~ware moves a Larger doe (as used in synchronized scanner format) through the bit map on a scanning path that matches the synchronized scanning format until a match is obtained. So, basicallyf the software does wha~ ~as proposed in the physicaL scanner in the two previous paragraphs~ In the same way, it is poss;ble to convert from intra-dot scanning to inter-dot scanning.
Facs;mile System_Using ~y~
Intra-Dot Scann;ng Th;s system uses a synchroni~ed scanner for transm;tting a synchronized scanner printer for reception. A good combination would be the synchronized scanner described above with the thermaL line printer~
The major advantage is an increase in matrix definition (resuLt;ng in Letter quaLity output) with increased printer speed and no increase in transmission time using : 3 modified group 3 or 4 compression system. (For descript;on of such compression system, reference shouLd l be had to EIA standards).
n~er- and Intra-dot Scanning As ment;oned earl;er herein, the present invention ~ is as applicable to CRT type d;spLays as it ;s to ; print;ng on paper. In fact, it is in this area that the present ;nvention has, perhaps, its greatest potential.
Such use will now be described~
The electron beam is verticalLy deflected as it I scans horizontally as shown ;n F;gure ~. Assuming a spot size of fi~teen mils with a spacing between scans of sixty m;Ls, in moving along its path 41, the electron beam would be deflected sinusoidaLly plus or minus ~hirty mils while ~he beam was moving horizontally fifteen mils. The vertical beam deflect;on sho~n in Figure 6 is a sawtooth. This could very well be accomplished by a sinusoidaL deflection that was tilted .
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~ l8 -to give a sawtooth-like pa~hO A sinuso;dal vertical deflection will give very sim;lar results. An alternate preferred method is sho~n in F;gure 6a us;ng stepped square wave modulat;on ~hich be~ter lum;nesce uniFormityO The hor;zontal scan;frequency ;s 15.6 KHz with about a ten ~;lliseco~d retrace. The vert;cal scar1n;ng frequency ;s s;xteen MHz. The beam deflect;on of plus or m;nus th;rty mils g;ves a non-interlaced display~ This requ;res a sixty-four MHz video. The result is a 1024 x 863 display~
In using an interlac~d display, the vert;cal deflection is reduced to plus or m;nus fifteen mils.
This reduces the video to thirty-two MH2 and the resul~
is still a 1024 x 860 display.
~y increas;ng the dot access frequency (consequently decreas;ng memory access time) the matr;x definition in both directions is ;ncreased. Thus, with 2 sixty-four -~
MHz dot access frequency, the result ;s a 2048 x 1720 display using interlaced scanning, although mini~um line width remains fifteen mils; however, the increased matrix s;ze w;ll perm;t letter quality fonts of the same quaLity as shown in Fi~ure 4 and eliminate the "jaggies"
in d;agonaLs and cur~ed lines in the graph;cs mode. j~
Inter- and Intra-dot Scanning Inter- and ;ntra-dot scanning in a CRT can be acco~pl;shed e;ther magnetically or electrostatic3lly, d~pend;ng on the type of CRT employed. If magnetically~
a separate small deflection coil 42 is mounted immediately after the electronic lens 44. It is preferable to resona~e ~he coil 42 with a capacitor 46 a~ the vertical scanning rate as illus~rated in F;gures 7 and 8~ I~ is not efficient to use the vertical deflection coils (not sho~n~ of the CRT itself. The - coil ~2 is ~oun~ed horizontally if sine waves are desired and off horizontal if pseudo-sawtooth scannirg '- ' . ~ ' .
as sho~n in Figure 9 is desired. The angle from horizontal 5~) is picked to match the horizontal scanning rate.
A preferable way to obtain inter and intra-dot scannlng in an electrostatic CRT is to use small electrostatic deflection plates 4g ;mmediately after the electronic focusirlg lens 44 as shown in Figures 10 and 11~ These plates 48 are placed vert;cally if sinuso;dal scanning is ~anted, or off vertical if pseudo-sa~tooth scann;ng is the desired result. Figure 12 illustrates pseudo-square Aave scanning if the sine wave driving the electrostatic plates is limited. This scanning is useful in some applications.
High Definition Pictures ~TV) If the p;cture ;s scanned in the same way as the monitor, definition of the resulting images can be improved in the same fashion~ This could be very useful in all the cases where current TV standards are not involved~ For example: photographic ima~es of aLl types, closed circuit TV, map projections, etc.
Vertical Def~nition Enhancement ~Apparent) of Televi_i_n Picture t A television picture is produced every one-thirtieth of a second by scanning each alternate line on a 25 television tube (CRT~ during the first one-sixtieth of a li second (i.el~ one-half of the picture); and, during the subsequent one-sixtieth of a second, scanning the lines intermedia~e ~hose scanned in the previous one-sixt1eth, with ~he second half of the pic~ureO This is a well-known and much-used technique known as 'interLacing"~
To improve the apparent vertical definition, it is desirable to scan all lines everyone-sixtieth of a s~cond~ The bLank intermediate scan lines could then be filled ;n by memoriz;ng a preceding line, comparin~ the .
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~ o data ;n that memory with the succeeding llne~ and then fill;ng the intermed;ate l;ne ~;th averaged, ;nterpolated, or otherw;se der;ved ;nformation. A
simple, less effective method normally employed simply repeats the scan l;ne twice.
There is much interest in improving the quality of ord;nary TV as transmitted by today's standards~ The major opportunity for qual;ty improvement results from elim;nating the above~descr;bed ;nterlace, which causes problems when the human eye moves vertiGally ~saccades) over the picture. For example, if you store an entire frame including the interlace~ combine the two, and then put the comb;ned picture on the tube at approx;mately 60 Hz~ you obta;n a much better qual;ty p;ctureu The major disadvantage of th;s is the expense~ Storing an ent;re frame and comb;n;ng ;t is still expensive to do electron;cally. Doubl;ng the hori7intal scan frequ~ncy is also expens;ve.
Another method that has been tried ;s to store one scan l;ne and then repeat the stored scan line ln tha ;nterlaced l;ne below. Th;s gives improvement, but not as much as the case where you combine the entire frame7 Further, it is st;ll relatively expens;ve because you must still double the horizontal scan frequency~
Using inter-dot scanning in various forms, one can dupl;cate or come close to these above-descr;bed ;mprovements; but, in a much less expensive way. The present invention achieves this not by doubling the hori~ontal scan to produce a complete picture every one-s;xtieth of a second; but, by a technique der;ved from ;nter-dot scanning in which the scanning electrode beam is caused to oscillate vertically with an amplitude equal to the space between adjacent scan lines and equal to the elec~ron beam diameter produc;ng the trace. By this means, the electron beam can produce picture - ~ ' 75~
information for one scan trace directly from the broadcast signal while on the peaks of its vertical oscillation and from deriYed informat;on from the preceding ~nd succeeding scan l;nes wh;le in the troughs of the oscillat;on. In th;s way, a single scan can produce ad~acent scan traces simultaneously, ~;th the electron beam being modulated to vary the intens;t;es as described~
The derived~ intermediate signal may be generated by storing, on the fly, one Line of scan information and comparing the s;gnal from the output of the store with the s;gnal on the input o~ the store ~the store being dynamic ;n that the stored ;nformation proceeds serially from the input to the output, i~e. a FIF0 store) and deriving ;ntermediate scan information from th;s.
Hence, the compared information will always be of sisnals synchronized vertically from preced;ng and succeeding scan lines.
The vertical oscillation of the electron beam may be of a sawtooth form whereby the scan line information of the preceding and intermediate scan lines are synchronized vertically one above the other essentially at the top and bottom of the vertical of the sawtooth form. The oscillation may be produced by the techniques of Figures 7 and 8 or Figures 10 and 11, as prev10usly described in detailO More detailed explanations ~ill now be provided~
Vertically scan the electron beam 40 sinuso;dalLy as in Figure 13 plus or minus one-half dot diameter at t~ice the maximum video frequency tsay seven to ten MHz)~ This produces a dot that is the same spot size horizontally, but tu;ce as high vertically. O~her than t~is, leave th~ monitor the same as before. This does the same th;ng as storing one scan line and repeating .
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the scan line in the interlaced line belo~. ~owever, lt does not need to store a line nor does it double the horizontal frequency. The disadvantage of this scheme is that the top and bottom horizontal lines ~ill act as follows. Assume top of horizontal contrast shift starts on an interlaced line. Extending donn the non-interlaced line above gives no intensity where there should be such~ The interlaced frame line gives the proper ;ntensity. So, the net result is that the top of hori20ntal edges are at one-half of proper intensity and blinking at the thirty H2 interlace rate. The same effect takes place at the bottom of the horizontal edge, The diagonal edges develop a sort of f~z7y/jagyy effect for the same reason. This technique ~;ll, ho~ever, fill ;n uertical l;nes. The apparent improvement takes place because much less of the picture is blinking at the thirty Hz ;nterlace rate~
Method 2 - Increased Picture $morovement Vertically scan the beam s;nuso;dally as in Figure 13 plus or minus one-half diameter at the maximum video frequency in a synchronized manner during the hor;zontal scan. Store one scan line on a CCD ch;p (such as the Fairchild CCD321A). Derive the interlace line by averaging the first and second ;nterlaced lines;combine the ori~inal in the derived inter`laced line so that a video synchronized signal that records the first line and the f;rst interlaced line on the face of the tube ;n one hori~ontal scan is obtained. This process is ~, repeated for the entire frame for one sixtieth of a second. When the interlaced frame comes up, ths ; forego;ng process is repeaeed. The superimposed p;cture resulting therefrom should be much improved.
Just how much better the picture actually is depends on the quality of the interpola~ion between the t~o scans. The simplest scheme is to average the intensi~y ' . .
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oF adjacent vertical pix~ls. The d;sadvantage of th;s scheme ;s similar to Method 1, described above. The effect on horizontal and diagonal l;nes is the same as Method 1~ except the edge ;ntensity ;s three-fourths of the proper value tas opposed to one-half); and, it still blinks at the ;nterlace rate of th;rty H~
Method 3 - Maximum P;cture Improvement The best technique is to compare three adjacent horizontal pixels on one scan ~;th three adjacent hor;zontal pixels immediately belo~ on the second scan as sho~n in Figure 14. I~ p;xel H1 ;s the same ;ntensity as pixel B2~ we make B12 the same intens1ty.
If B1 and ~2 are not the same ;ntensity, we make B12 the average of ~he two intens;ties unless A1 intensity is the same as C2, ;n ~hich case we make ~12 the same intensity as A1 or C2. In a similar manner, ;f A2 is the same intensity as C1~ we make 812 the same intens;ty. The advantage of th;s method over Method 1 ;s that most diagonal edges are continued almost perfectly. Horizontal fuzziness should be about the same as Method 2.
In Methods 2 and 3, special circuitry is needed to interpolate between horizontal scans. Figures 15 and 16 show in block d;agram form two circuits tha~ could b~
employed to perform this interpolation. figure 15 shows a CCD32A chip 50 connec~ecl wi~h a multiplexer 52 to provide th~ video signal synchronized with the vertical pseudo-square wave scanning for Method 2c The CCD321A
chip S0 ;s connected in series mode providing 910 bits of analog shift register~ After one horizontal sweep is stored in the CCD321A, the timing signals are such that the correspond;ng b;t of the subsequent horizontaL scan signal is going into the CCD321A as the corresponding bit of the previous horizontaL scan signal is going out .
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of it~ By ~verag;ng the correspond;ng b;ts, one can obta;n the ;nterpolated ;nterlaced s;gnal that ;s desired~ The video signal to the CRT at 54 is the result;ng of the multiplexer 52 multiplexing between the prev;ous horizontal scan signal and the ;nterpolated interlaced s;gnal at the ;nter-dot scanning frequency.
It should be noted that when us;ng this techn;que~ the s;gnals appear on line 54 to the CRT one hor;zontal scan line late.
To accompl;sh Method 3, the more complicated c1rcu1t shown in F;gure 16 must be used. In th;s case, a spec;al modified CCD321A ch;p 50 wh;ch makes available the f;rst three bits of the incoming s;gnal and the last three bits in memory ;s used. Here, again, the timing is such that there are three corresponding bits of two adjacent horizontal scan signals. These are fed to a special logic chip 56 which includes three comparators and which includes logic to perform ~he steps of Method 3~ The output is aga;n multiplexed by the multiplexer --52 ~t the scanning freq~ency and fed to the CRT on output line 54. HereO aga;n, the picture displayed is one scan line late.
Method ~
Still another embodiment of the invention is shown in Fig. 17 ~hich is a schematic circuit diagram showing a modif;ed digital TV system. With the advantage of 1/2 frame and full frame digital storage, Fig~ 17 shows ho~
to eLiminate any interpolation and elim;nate the ;nterlaced scan us;ng a standard TV transmission.
The video s;gnal goes into a 1/2 frame store and ~e multiplex the incoming signal ~;th the signal delayed 1/2 frame as shown by the diagram at ~he bottom of Figure 17. This gives a non-interlaced picture with no interpolation. If we add the interpolation used by Method 2 or 3, we can double the number of displayed .' ' ~ ' .:
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l;nes ~ithout interlace by us;ng the scan pattern shown on F;gure 6A still only using standard TV transm;ssions and only 15.6 KHz horizontal scan.
Pro~ection_TV
Projection TV us;ng three tubes of different colors will operate as ~escribed above as there are no complicati~ns oF color shadow masks or trinitron aperature ~rilles.
~d~
In order to make sure that we don't have to match the vertical scan ~ith the shadow mask holes, ue must use a vertical scanning frequency twice the frequency which the horizontal scan intercepts the shadow mask~
Th;s insures that the beams hit the mask as well as they do w;thout any vertical scanning. Its disadvantage is that the final video amplifier must be quadruple the band ~idth and the beam current must be larger to compensate for the shorter time the beam is in the shadow mask. If we use the pseudo-square wa~e scanning trequ;rin~ eLectrostat;c deflection as in Figure 10 and 11) as iLlustrated in F;gure 1Z, ~e minimize the ;ncrease injbeam current required. With double the shado~ mask frequency, ~e get half the beam current on ~he phosphor in one horizontal scan as compared to ~he current if we were not inter-dot scanning; however, since we pain~ each line twice as much, the beam current required remains about the same.
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When using a trin;tron type color tube, ~he inter-dot scanning ~requency should be equal to tw;ce the frequency at w~ich the hori20ntal scan lntercepts the aperature grill. Pseudo-square wave modulation as ;n f;gure 12 should also be used again. Once again, we ~et half the beam current pn the phosphor in each ~, . .
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5;~4 horizontal scan; but, because we have tw;ce the scan, there is no appreciabLe increase ln beam current required.
Wherefore, having thus described my invent~on~ I
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Claims (23)
1. A raster scanning system comprising:
(a) means for repeatedly sweeping an image producing means across a display medium to produce a series of sweeps for the creation of visual images in said series of sweeps;
(b) deflection means for cyclically deflecting the image producing means in a direction substantially normal to the sweep direction in a repetitive series of like oscillations throughout each image producing sweep across the display medium;
(c) means for controlling the image producing means to vary the brightness of pixels created;
(d) means for supplying a first image information signal synchronized with said repetitive series of oscillations to control said controlling means to produce visual image information on said display medium at one set of desired corresponding locations on each of desired ones of said oscillations during a said sweep; and (e) means for supplying at least a second image information signal synchronized with said repetitive series of oscillations to control said controlling means to produce visual image information on said display medium at another set of desired corresponding locations on each of desired ones of said oscillations during the said sweep.
(a) means for repeatedly sweeping an image producing means across a display medium to produce a series of sweeps for the creation of visual images in said series of sweeps;
(b) deflection means for cyclically deflecting the image producing means in a direction substantially normal to the sweep direction in a repetitive series of like oscillations throughout each image producing sweep across the display medium;
(c) means for controlling the image producing means to vary the brightness of pixels created;
(d) means for supplying a first image information signal synchronized with said repetitive series of oscillations to control said controlling means to produce visual image information on said display medium at one set of desired corresponding locations on each of desired ones of said oscillations during a said sweep; and (e) means for supplying at least a second image information signal synchronized with said repetitive series of oscillations to control said controlling means to produce visual image information on said display medium at another set of desired corresponding locations on each of desired ones of said oscillations during the said sweep.
2. A raster scanning system according to claim 1 where said oscillations are contiguous throughout each image producing sweep.
3. A raster scanning system according to claim 1 wherein the display medium is a cathode ray tube, the image producing means is an intensity controllable electron beam, the sweeping means deflects the beam to produce a series of parallel sweeps of the beam across the display screen of the cathode tube, the deflection means comprises a secondary means for deflecting the electron beam disposed following said sweeping means in the path of said electron beam between the source and the display screen, and the controlling means controls the intensity of the electron beam.
4. A raster scanning system according to claim 3 wherein the first and second image information signals have an effective video frequency equal to the frequency of said oscillations.
5. A raster scanning system according to claim 3 wherein the oscillation comprise one of a clipped sine, sine, square or saw-tooth wave form.
6. A raster scanning system according to claim 2 wherein the oscillation amplitude (peak to peak) is equal to the spacing between adjacent raster sweeps.
7. A raster scanning system according to claim 4 wherein said electron beam produces a series of dots to form said visual images and the amplitude of said oscillations is substantially equal to the diameter of said dots produced by said electron beam.
8. A raster scanning system according to claim 1 comprising a FIFO (first in first out) storage means for serially storing one scan line of an incoming video signal and the output of said storage means provides said first image information signal while a simultaneous input to said storage means provides a said second image information signal.
9. A raster scanning system according to claim 1 comprising a FIFO (first in first out) storage means for serially storing one scan line of an incoming video signal and a logic means for comparing the output from the storage means with the simultaneous input thereto to provide a derived signal which forms the first image information.
10. A raster scanning system according to claim 9 wherein said desired first image information signal controls the controlling means to form an interlace line between the lines of an interlaced raster currently being scanned while the input to said storage means comprises the second image information signal to form a line of the interlaced raster currently being scanned and next adjacent said interlaced line.
11. A raster scanning system according to claim 10 comprising multiplexing means combining said first and second image information signals to produce a video synchronized signal to control said controlling means whereby said image producing means will create a line and an interlace line on said display medium during each horizontal scan.
12. A cathode ray tube display such as a computer monitor, television, or the like including a raster scanning system having a source of an intensity controllable electron beam and a main means for deflecting the beam to create a series of horizontal sweeps of the beam from the top to the bottom of a display screen for selectively creating a series of pixel dots in a series of parallel rows comprising:
(a) deflection means for deflecting the dot-creating means in a direction substantially normal to the sweep direction;
(b) drive means operably connected to said deflection means for cyclically deflecting the dot-producing means in a repetitive pattern throughout each dot-producing sweep across the display medium, said driving means comprising a signal producing means for applying a repetitive electrical signal to said deflection means to produce a peak to peak amplitude of said pattern which is equal to the spacing between horizontal sweeps;
and (c) means for providing an image information signal synchronized with said repetitive pattern to control said intensity controllable electron beam to generate two parallel image lines for each said sweep.
(a) deflection means for deflecting the dot-creating means in a direction substantially normal to the sweep direction;
(b) drive means operably connected to said deflection means for cyclically deflecting the dot-producing means in a repetitive pattern throughout each dot-producing sweep across the display medium, said driving means comprising a signal producing means for applying a repetitive electrical signal to said deflection means to produce a peak to peak amplitude of said pattern which is equal to the spacing between horizontal sweeps;
and (c) means for providing an image information signal synchronized with said repetitive pattern to control said intensity controllable electron beam to generate two parallel image lines for each said sweep.
13. A raster scanning system according to claim 3 wherein said first image information signal is a received signal and said second image information signal is a derived signal.
14. A raster scanning system according to claim 2 wherein the oscillation amplitude, peak to peak, is greater than the spacing between adjacent raster sweeps.
15. A raster scanning system according to claim 14 wherein the oscillation amplitude, peak to peak, is approximately double the spacing between adjacent raster sweeps.
16 A raster scanning system according to claim 14 wherein the oscillation amplitude, peak to peak is approximately four times the spacing between adjacent raster sweeps.
17 A cathode ray tube display such as a computer monitor, television, or the like including a raster scanning system having a source of an intensity controllable electron beam and a main means for deflecting the beam to create a series of horizontal sweeps of the beam from the top to the bottom of a display screen for selectively creating a series of pixel dots in a series of parallel rows comprising:
(a) deflection means for detecting the dot-producing means in a direction substantially normal to the sweep direction;
(b) drive means operably connected to said deflection means for cyclically deflecting the dot-producing means in a repetitive pattern throughout each dot-producing sweep across the display medium to allow production of a derived interlace raster or sweep pattern, said driving means comprising a signal producing means for applying a repetitive electrical signal to said deflection means to produce a peak to peak amplitude of said pattern which is equal to the spacing between horizontal sweeps;
(c) storage means for storing a scan line of an incoming video signal;
(d) logic means for producing a derived interlace video signal from the incoming video signal; and (e) means for combining the incoming and derived signals to produce a video synchronized signal that displays a line and a derived interlace line on the display screen for each horizontal scan.
(a) deflection means for detecting the dot-producing means in a direction substantially normal to the sweep direction;
(b) drive means operably connected to said deflection means for cyclically deflecting the dot-producing means in a repetitive pattern throughout each dot-producing sweep across the display medium to allow production of a derived interlace raster or sweep pattern, said driving means comprising a signal producing means for applying a repetitive electrical signal to said deflection means to produce a peak to peak amplitude of said pattern which is equal to the spacing between horizontal sweeps;
(c) storage means for storing a scan line of an incoming video signal;
(d) logic means for producing a derived interlace video signal from the incoming video signal; and (e) means for combining the incoming and derived signals to produce a video synchronized signal that displays a line and a derived interlace line on the display screen for each horizontal scan.
18. A raster scanning system according to claim 1 wherein the means for repeatedly sweeping produces an interlaced raster scan and the oscillation amplitude (peak to peak) is equal to the spacing between a current sweep and the next adjacent interlace sweep.
19. A cathode ray tube display according to claim 12, wherein the means for creating a series of horizontal sweeps produces an interlaced raster scan and the oscillation amplitude, peak to peak is equal to the spacing between a current sweep and the next adjacent interlace sweep.
20. A cathode ray tube display according to claim 17 wherein the means for creating a series of horizontal sweeps produces an interlaced raster scan and the oscillation amplitude, peak to peak is equal to the spacing between a current sweep and the next adjacent derived interlace sweep.
21. A raster scanning system according to claim 2 wherein the oscillation amplitude (peak to peak) is approximately three quarters of the spacing between adjacent raster sweeps.
22. A raster scanning system according to claim 2 wherein the oscillation amplitude (peak to peak) is approximately one half the spacing between adjacent raster sweeps.
23. A raster scanning system comprising:
(a) means for repeatedly sweeping an image producing means across a display medium to produce a series of sweeps for the creation of visual images in said series of sweeps;
(b) means for controlling the image producing means to vary the brightness of pixels created;
(c) deflection means for generating a first and a second parallel image line for each said sweep by cyclically deflecting the image producing means in a direction substantially normal to the sweep direction in a repetitive series of like oscillations throughout each image producing sweep across the display medium;
(d) means for supplying a first image information signal synchronized with said repetitive series of oscillations to control said controlling means to produce visual image information on said display medium at at least one desired location on each of desired ones of said oscillations to produce said first of said image lines; and (e) means for supplying at least a second image information signal synchronized with said repetitive series of oscillations to control said controlling means to produce visual image information on said display medium at at least another desired location on each of desired ones of said oscillations to produce said second of said image lines.
(a) means for repeatedly sweeping an image producing means across a display medium to produce a series of sweeps for the creation of visual images in said series of sweeps;
(b) means for controlling the image producing means to vary the brightness of pixels created;
(c) deflection means for generating a first and a second parallel image line for each said sweep by cyclically deflecting the image producing means in a direction substantially normal to the sweep direction in a repetitive series of like oscillations throughout each image producing sweep across the display medium;
(d) means for supplying a first image information signal synchronized with said repetitive series of oscillations to control said controlling means to produce visual image information on said display medium at at least one desired location on each of desired ones of said oscillations to produce said first of said image lines; and (e) means for supplying at least a second image information signal synchronized with said repetitive series of oscillations to control said controlling means to produce visual image information on said display medium at at least another desired location on each of desired ones of said oscillations to produce said second of said image lines.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA000551459A CA1275334C (en) | 1987-11-10 | 1987-11-10 | Raster scanning system |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA000551459A CA1275334C (en) | 1987-11-10 | 1987-11-10 | Raster scanning system |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1275334C true CA1275334C (en) | 1990-10-16 |
Family
ID=4136822
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000551459A Expired - Lifetime CA1275334C (en) | 1987-11-10 | 1987-11-10 | Raster scanning system |
Country Status (1)
| Country | Link |
|---|---|
| CA (1) | CA1275334C (en) |
-
1987
- 1987-11-10 CA CA000551459A patent/CA1275334C/en not_active Expired - Lifetime
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