FLAT-PANEL
`DISPLAYS
`AND CRTs
`
`Edited by
`Lawrence E. Tannas, Jr.
`
`r displal's industry for
`ti form with the color
`r) and adapted as such
`r en approximation of
`L Lancaster, PA., and
`
`VAN NOSTRAND REINHOLD
`New York
`
`

`

`Copyright O 1985 by Van Nostrand Reinhold
`
`Library of Congress Catalog Card Number 84 -11839
`ISBN 0-442-28250-8
`
`All rights reserved. No part of this work covered by the copyright hereon may
`be reproduced or used in any form or by any means-graphic, electronic, or
`mechanical, including photocopying, recording, taphg, or information storage
`and retrieval systems-without permission of the publisher.
`
`Manufactured in the United States of America
`
`Van Nostrand Reinhold
`ll5 Fifth Avenue
`New York, New York 10003
`
`Van Nostrand Reinhold International Company Limited
`I I New Fetter Lane
`London EC4P 4EE, England
`
`Van Nostrand Reinhold
`480 La Trobe Streer
`Melbourne, Victoria 3000, Australia
`
`Nelson Canada
`ll20 Birchmounr Road
`Scarborough, Ontario MIK 5G4, Canada
`
`1 5 1 4 1 3 t 2 1 1 1 0 9 8 7 6 5 4 3
`
`Library of Congress Cataloging in Publication Data
`Main enty undet tifle:
`
`Flat-panel displays and CRTs.
`
`Includes index.
`1. Information display systems. 2. Cathode-ray tubes.
`I. Tannas, Jr., Lawrence E.
`381.3819',s32 84 -1 1839
`TK7882J6F53 1984
`rsBN 0-442-28250{
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`l-
`
`18 FLAT-PANEL OISPLAYS AND CRTs
`
`1.5 CLASSIFICATION NOMENCLATURE
`
`In any field of endeavor, it is desirable to use
`standard classification nomenclature. In the
`display industry, there has been a rush to form
`new acronyms. Without denying inventors the
`right to name their new display, a standard
`generic classification of displays can be used.
`The outline for such a classification is shown in
`Table l-3. The table lists the key words which
`can be used to categorize any display device. As
`an example of the use of this scheme, one of
`the first liquid-crystal displays is classified as:
`
`e Phenomenon: Liquid crystallinity (LC)
`o Material: MBBA and EBBA with dopant
`o Contrast: Dynamic scattering with back
`lighting
`o Addressing: Direct with ac refresh
`o Application: Numeric
`
`This generic classification could be reduced
`to key words to describe display devices in
`technical reports, papers, and dissertations.
`
`for
`Table 1-3 Generic Classification
`Flat-Panel Displays
`
`Phenomenon
`
`Material
`
`Contrast
`
`Addressing
`
`The primary physical phenomenon
`used to create a particular visual
`effect. Examples: liquid crystal-
`linity, electrophoresis, light-
`emittine diodes.
`
`The chemical name and physical
`state of the display material. Ex-
`amples: Mn activated ZnS thin-
`film phosphor, doped MBBA/
`EBBA.
`
`The electrically alterable medium
`used to create contrast between
`picture elements. Examples: bi-
`refringence, absorption, green
`luminance on ablack background.
`
`The method for controlling an iuray
`of picture elements. Examples:
`direct, scan, grid shift, or matdx
`addressing, with memory or re-
`fresh, ac or dc. intrinsic or
`extrinsic.
`
`Application
`
`The display category most suited.
`Examples: analog, alphanumeric,
`vectorgraphic, or video.
`
`If an acronym is needed in the paper, the phe-
`nomenon need only be abbreviated, such as
`LED for light-emitting diode, LC for liquid
`crystallinity, or GD for gas discharge. The
`reader has been informed of the other features
`such as ac or dc, memory or refresh, thin film
`or powder. Trademarks could be used in place
`of the abbreviations where it is necessary to
`refer to specific manufacturer's product or
`approach.
`Further, it makes for easier reading if the
`letter "D" for display is left out of the acronym.
`It is easier to read "The EL display uses less
`power . . ." than "The ELD uses lesspower. . ."
`and there is more information in "an EL dis-
`play" to assist the unfamiliar reader. Addi
`tionally, the acronym can be used as an adjec-
`tive, such as in EL powder, EL light, etc.
`
`1 . 6 P I C T U R E E L E M E N T O R P I X E L
`
`The basic building block for all displays is the
`picture element as shown in Fig. l-10. The
`noun "pixel" is formed from the contraction
`of "picture element" and is almost universally
`used in its place. The pixel is the smallest re-
`solvable spatial-information element as seen by
`the viewer. There is no spatial information in a
`display below the resolution of the pixel area.
`Some authors, particularly in the word-pro-
`cessing industry use the contraction "pel." By
`consensus, "pixel" is preferred. Pixel has been
`directly translated into French, German, Japa-
`nese, and other languages with the same meaning.
`The pixel may be further subdivided to
`achieve color (see Fig. 1-ll) or gray shades
`(Fig. l-12). The key point is that the pixel is
`the lowest resolvable spatial incremental quan-
`tum. The other display dimensions of hue
`(color), saturation (color purity), luminance
`(gray shades), and time are all independent of
`the spatial dimension.
`As an example of pixel subdivision, color is
`often achieved using three dots per pixel, one
`red, one green, and one blue within the spatial
`area. A clever geometric arrangement can be
`used with matrix-addressed displays, as depicted
`in Fig. l-1lb. Neighboring pixels can share
`color dots if properly programmed. In this case,
`the active area is much larger than the pixel
`spatial area.
`
`a ' . * 1
`
`.
`
`' ' {
`
`! : r
`
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`
`l ;
`
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`

`

`r, the phe.
`l. such as
`for liquid
`arge. The
`:r features
`, thin film
`d in place
`cessary to
`:oduct or
`
`ing if the
`acronym.
`uses less
`o*'er . , ."
`n EL dis-
`er. Addi-
`an adjec-
`
`t / -
`
`E L
`
`11 s is the
`-10. The
`ntraction
`niversally
`allest re-
`; seen by
`rtion in a
`:l area.
`rord-pro-
`pel." By
`has been
`rn, Japa-
`neaning.
`rided to
`; shades
`' pixel is
`al quan-
`of hue
`minance
`tdent of
`
`color is
`xel. one
`: spatial
`can be
`lepicted
`n share
`his case,
`re pixel
`
`I N T R O D U C T I O N 1 9
`
`C o l u m n s
`
`Y3
`
`%r mT
`T mn m
`rutr m[ttl
`
`P i x e l a c t i v e a r e a O f f - p i x e l
`
`O n - p i x e l
`
`I n a c t i v e a r e a
`
`t s x "
`cc
`
`3
`
`P i x e l
`s p a t i a l
`area
`
`Fig. l-10. Nomenclature of a flat-panel display pixel array,
`
`Several resolution lines in the rows or col-
`Jmns or both can be used for gray shades. For
`:xample, the intersection of two row and two
`;olumn electric leads in matrix addressing can
`:e used to define a single pixel. The pixel is
`:hen made up of four dots, and the excitation
`oi different numbers of dots can be used for
`gray shades. In Fig. 1-12 the dots are of dif-
`:erent size so that fairly uniformstepsof sixteen
`gray shades can be portrayed using all combina-
`:ions of the four dots.
`The pixel spatial dimensions can be defined
`11' their pitch. The resolution is the reciprocal
`of pitch and is quoted as display lines per inch
`or millimeter. Display lines do not have spaces
`
`in the sense that optical lines have spaces. For
`example, it takes a minimum of two display
`lines to represent an optical line and its space.
`An optical line space is represented by a display
`line turned off.
`To display 20 optical lines per inch, for ex-
`ample, requires 40 display lines (TV lines) times
`the Kell factor of 1.4 for a total of 56 display
`lines per inch. The Kell factor is used to deter-
`mine the number of TV raster lines needed to
`reproduce a resolution test chart. Other meth-
`ods are used today, as discussed in Chap. 4.
`The active area may be less than the pixel
`area, as shown in Fig. l-10. The checkerboard
`pattern in Fig. l-10 is useful as a test pattern
`
`Pixel Column Lines
`
`l 2
`
`P i x e l C o l u m n L i n e s
`
`2 3
`
`Pixel P,,
`Active
`
`P i x e l
`Spatial Area P.,,
`
`p,
`"
`
`: {
`
`= , {
`
`, {t
`
`o f: 't
`
`= (
`9 3 1
`i i L
`
`^ {
`I
`
`Conventional Pixel Subdivision
`for Three-Color D isplay
`
`(b) Shared Pixel Subdivision For lvlore Ef{icient
`Active Area at Higher Resolution
`
`Fig. l-11. Pixel subdivision for color.
`
`

`

`I
`
`20 FLAT-PANEL DISPLAYS AND CRTs
`
`Yet there are many su
`play applications Prir
`power and sunlight re
`
`1.7 DISPLAY ARF
`
`A display is simPlY r
`controllable Pixels. Tl
`lcpends uPon the aP
`rven pixels is needer
`A four-digit watch d
`tnes seven Plus one I
`fhe colon is onlY o
`&ts are not indePend
`-ion System Commi
`requiresaPl
`drision
`flEO rows bY 320 cr
`r lixel arraY (digital t
`The total Pixel ct
`time, color, etc.
`l$
`instantaneous i
`:d
`Itture.
`The arraY is nonn
`rlrmns. The addrec
`number and t
`p
`from thc
`Fting
`in Fig. l-10.
`brn
`the state of tl
`It
`-css.
`h matrix'addresr
`t: mrmallY addrer
`complete arnY
`L
`end the tirnc t'
`I.
`r Cc'o set bY thc m
`timc Per row- I
`-
`in order to
`F
`dutY fr
`Gniz.
`of thc tod
`lpt
`rnd b thclc
`Fd
`e
`of rotl
`fc
`criticel
`I sl
`$ch rs i
`-||l
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`lli
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`5? n
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`ar* srGs;:s
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`GE
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`o -
`9 oL X
`c C
`
`E g
`
`J v
`g r g
`> x
`; a
`i l g
`
`off
`
`Pixel Column Llnes
`2
`1
`
`1
`
`Column Electrlc Leads
`2
`3
`/ \
`
`. . .
`
`. . .
`
`4
`'
`
`l t liii
`
`o
`
`d
`f r
`>
`g
`( , <
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`
`6
`d
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`o
`c
`E E E 3
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`II
`I
`3 j
`
`L t o
`' '
`
`I
`
`J
`
`o l u l
`
`- te -;
`f
`t:
`l ;,1
`It
`
`. . l l l l l l !
`I
`:
`"
`
`l l l l l l l l
`
`. { _ __ f-t_! _ l-l_!_ _-_ }
`
`I
`l
`\---Y-----J
`
`t l l
`i l l l
`V
`
`I
`
`\---Y-----J
`
`l l l
`l l
`
`V
`
`Pixel Active Area = A+B+C+D
`A = 2 8 = 4 C = 8 D
`(a) GraPh of Pixel Subdivision'
`
`Fig. l-12. Pixel subdivision for gray shades.
`
`0
`1 X 1
`2 X 2
`3 X X 3
`4 X 4
`5 X X 5
`6 X X 6
`7 X X X 7
`8 X 8
`9 X X 9
`1 0 x x 1 0
`1 1 X
`1 2 X X 1 2
`1 3 X X X 1 3
`1 4 X X X 1 4
`1 5 X X X X 1 5
`
`X Area turned on
`
`(b) Gray Shade Table
`
`X X 1 1
`
`for measuring contrast ratio between on-pixel
`and off-pixel. Using this test pattern would lead
`to a conservative measure of contrast ratio, since
`each off-pixel is surrounded by on-pixels which
`can indirectly contribute to the brightness of
`the off-pixel by light piping or scattering. Studies
`have shown that the readability of an emissive
`display is not adversely affected with pixel-
`active areas as low as 5O% or less. Diffusers can
`be used to spread out the pixel luminance to fill
`the pixel spatial area.
`Except for CRTs and some flat CRTs, the
`inventioh of a display begins with the pixel. It
`must be electronically alterable and reversible.
`The contrast ratio must be high, the speed of
`response fast, and the power consumption low.
`Additionally, it must be operable over a wide
`temperature range with long life. It is not im-
`portant whether it is an emissive or nonemissive
`technique. There are thousands of ways to create
`a pixel. Only a few are worthy of pursuit. In
`genergl, the pixel must have the following prop-
`erties to be suitable forageneral-purpose display
`(500 rows by 500 columns):
`
`.
`.
`
`.
`
`Resolution: 64 lines/in.
`Pixel contrast ratio: 10:1 (over a wide
`ambient illumination range)
`Directionality: Lambertian over 60-deg
`cone from normal
`Operating temperature range: - 40oC to
`g0"c
`Life (maintenance): Memory-106 cycles
`Refresh-104 hours
`Dwell time: 20 trlsec
`Power (less than 25 W total): 0.1 mW per
`pixel
`Duty cycle: Memory-l00%
`Refresh (lO0Hz\-}.2Vo
`o Discrimination ratio (luminance of on-pixel
`to off-pixel at one-third voltage): l0a :1
`
`.
`
`.
`
`.
`.
`
`It is necessary but not sufficient that a pixel
`have all these properties. If it does not, then it
`may be suitable as a smaller display or special-
`purpoie display depending upon the limita-
`tions. There are no liquid-crystal materials which
`possess all these pixel properties, and there are
`no successful 500 by 500Jine LC displays either.
`
`

`

`\ :r there are many successful liquid-crystal dis-
`..r applications primarily because of the low
`t.er and sunlight readability properties.
`
`1.7 DISPLAY ARRAY
`
`\ Jisplay is simply an array of independently
`- , rtrollable pixels. The number of pixels needed
`:::'ends upon the application. A minimum of
`.:r.'n pixels is needed for a numeric character.
`\ :our-digit watch display would require four
`'-:1es seven plus one for the colon, or 29 pixels.
`l:e colon is only one pixel if the two colon
`: :s are not independent. NTSC (National Tele-
`'.iron System Committee) standard commercial
`':.Erision requires approximately I 50,000 pixels
`3i0 rows by 320 columns) when displayed in
`i :rrel array (digital equivalent).
`The total pixel count is independent of re-
`":sh time, color, etc. The pixel count limits the
`
`'-:al instantaneous information content of the
`: . i I u r e .
`The array is normally organized in rows and
`- -.umns. The address of a pixel is defined by its
`' . e number and column number, normally
`- . .rnting from the upper left-hand corner as
`;-,$'n in Fig. l-10. The electronic drive con-
`':-'ls the state of the pixels according to their
`. : iress.
`In matrix-addressed displays, all the columns
`i-': normally addressed in parallel to save time.
`l:le complete array is addressed one row at a
`'-:re, and the time to address the complete array
`-i rhen set by the number of rows multiplied by
`'.:e time per row. The rows are kept to a mini-
`-:um in order to minimize frame time and
`-.arimize duty factor. The duty factor is the
`rrcent of the total time spent on each row or
`::rel and is therefore the reciprocal of the
`-.rmber of rows, a key point. The duty factor
`r very critical for slowly responding display
`-:.rterial such as in liquid-crystal displays. Liq-
`-:J-crystal displays are so slow that only 64 to
`It rows can be addressed per frame directly.
`ilcwever, the display can be made to have more
`::splay rows than it has addressed rows. Tech-
`-:ques for doing this are shown in Fig. l-13. In
`-'r;rmple Fig. l-13d, every set of four addressed
`- ,lumn lines are rotated to appear as row lines.
`i:ris complicates the data signal and electrode
`
`I N T R O D U C T l O N 2 1
`
`lines, but it increases the useful display row lines
`by a factor of 4 or more. Since the columns are
`addressed in parallel, the number of addressed
`column lines is of no consequence, time-wise.
`A flat-panel display array is. normally a fixed-
`digital set due to its construction; the excep-
`tions are the flat-CRT Aiken Tube, the Gabor
`Tube, and others that use the scan addressing
`techniques which will be discussed in the next
`section. The number of rows and columns is
`constrained by the electrode configuration. The
`number of rows and columns is discrete. To
`make the best use of electronic counters in the
`electronic drive, and of memory locations in a
`picture memory map, the number or rows and
`columns is often a power of two, such as 256
`rows by 512 columns.
`The CRT, Aiken Tube, and Gabor Tube are
`analog displays. The pixel locations are defined
`by an analog voltage on the vertical and hori-
`zontal deflection amplifiers. The display array
`is called a raster scanning pattern or Lissajous
`pattern. The pixel size, called a spot size (diam-
`eter at 50% Iuminance), is principally defined
`by the electron beam focus, the video amplifier
`bandwidth, and the phosphor light diffusion.
`The number of rows and columns possible in a
`CRT corresponds to the raster vertical dimen-
`sion divided by the spot vertical dimension and
`the raster horizontal dimension divided by the
`spot horizontal dimension, respectively.
`The CRT display phosphor screen is usually
`continuous and without electrode definition.
`The deflection and video amplifiers are external
`to the tube itself. These analog amplifiers can
`be adjusted or modified to greatly alter the
`pixel size and raster size of a CRT display with-
`out changing the tube. This capability is used
`in the zoom feature of some commercial TV
`sets.
`The number of row lines greatly impacts
`upon the display media performance require-
`ments in the following way:
`
`l. Refresh duty factor is inversely propor-
`tional to the number of electronic row
`lines, and
`2. Prxel contrast ratio is inversely propor-
`tional to the number of electronic row
`lines.
`
`o
`
`' = !
`
`- . o
`2 6
`
`E :
`off
`
`12 J 45678 Y
`
`1 0
`1 1
`1 2
`
`I J
`
`1 4
`1 5
`
`wide
`
`)-deg
`
`C t o
`
`cles
`trs
`
`V per
`
`pixel
`: l
`
`pixel
`ren it
`ecial-
`mita-
`;hich
`e ale
`ther.
`
`nE
`
`

`

`I
`
`22 FLAT-PANEL DISPLAYS AND CBTs
`
`Pixel P,,
`Spatial Area
`
`Addressed
`R ows
`
`Addressed Columns
`
`Address Upper Columns, Set
`
`Addr.rr"d
`fRows
`t
`
`=-_ltl
`;l tl
`lll--]
`
`l a ,
`
`C o n v e n t i o n a l A r r a y
`{ A d d r e s s 1 2 b y 6 ; D i s p l a y 1 2
`
`b y 6 )
`
`A d d r e s s e d C o l u m n s
`o f U p p e r S e t
`
`L---__--Y----____
`Address Lower Columns, Set
`
`Folded Array
`Two-to-One Reduction in Addressed Rows
`(Address 6bv 12: Display 12 by 6)
`
`Addressed Columns
`
`T*T:?I
`
`uooer set
`
`1_
`
`Addr".r"d
`I
`Rows .l
`L"#s"
`I
`
`\___________Y____-/
`
`A d d r e s s e d C o l u m n s
`o f L o w e r S e t
`
`Add ressed
`R o w s 3
`
`j
`
`, r r
`
`l . : r : r r : R t
`
`( b ) P a r a l l e l A r r a y
`T w o - t o - o n e l n c r e a s e i n R o w D w e l l T i m e
`( A d d r e s s 2 s e t s o f 6 b y 6 ; D i s p l a y 1 2 b y 6 )
`
`(d) Distorted Column Array
`Four-to-One Reduction in Addressed Rows
`( A d d r e s s 3 b v 2 4 ; D i s p l a y 1 2 b y 6 )
`
`Fig. l-13. Techniques for reducing row addressing time.
`
`The requirements on the display media can
`be reduced if the electronically addressed row
`lines can be reduced. The first and obvious
`thing is to simply skew the presentation by
`increasing the column lines and reducing the
`row lines. This distorts the display presentation
`and can only be used within limits. The next
`step is to reduce the electronic rows without
`reducing the displayed rows by using tech-
`niques such as those shown in Fig. l-13.
`
`1.7.1 Duty Factor. A display is addressed
`or strobed sequentially. The time spent on each
`pixel is inversely proportional to the number of
`
`pixels and is called the duty factor. For an array
`of 500 by 500 the duty factor becomes 4 parts
`per million, or .0004%, which is quite small.
`Only CRT phosphors and LEDs can operate
`satisfactorily with a duty factor this small.
`The duty factor can be greatly increased by
`using line-at-a-time addressing. That is to say,
`a complete row is addressed in parallel, and the
`rows are then commutated sequentially. For an
`array of 500 by 500 the duty factor becomes 2
`parts per thousand, or .2%, which is a signifi-
`cant improvement. This is why line-at-a-time
`addressing is used whenever it is at all practical
`and why the number of addressed rows is kept
`
`

`

`I
`
`24 FLAT-PANEL DISPLAYS AND CRTs
`
`Most display technologies in combination with
`the addressing techniques have a limited dis-
`crimination ratio.
`
`1 . 8 A D D R E S S I N G
`
`For the uninitiated, the least understood and
`most underestimated task in flat-panel displays
`is that of addressing the hundreds of thousands
`of pixels. It is the single most difficult problem.
`The solution chosen has a great impact on the
`display cost. The problem is to convert a serial
`electrical data sequence into a rectilinear pixel
`array in real time.
`The success of the CRT is directly attributable
`
`to the simplicity of its scan-addressing technique
`used to generate the raster or Lissajous patterns.
`Scan addressing is possible because of highly
`efficient, fast-responding cathodoluminescent
`phosphors. Scan addressing is further unique
`and ideal in that it can directly accept data in
`real time at video speeds from a single serial
`data channel without the need for intermediate
`data storage or shift registers.
`In flat-panel displays, the addressing problem
`is similar in many ways to that in randomly ad-
`dressable digital memories and solid-state imag-
`ing devices. The cross-coupling anomaly of a
`partial selection of nonselected pixels is identi
`cal. However, with displays the array must be
`of a size appropriate for viewing. It rnust be
`planar, with the proper linearity, size, shape,
`and percent active area. The viewing signal-to-
`noise ratio and power must be appropriate for
`human interpretation. There is no opportunity
`for noise filtering or error correction once the
`information is displayed.
`All electronic displays are addressed by one
`of five basic techniques as summarized in Table
`1-4. Normally, power is applied at the same
`
`time the pixels are addressed. In some flat-panel
`displays, the information is applied by one ad-
`dressing scheme and the power is applied by
`another. The pixelg in the array must effectively
`have three or four electrical leads when infor-
`mation and power are applied separately.
`Addressing becomes more and more difficult
`as the humber of pixels in the array becomes
`Iarger and larger. A successful addressing solu-
`-for
`tion
`an atruy of 64 rows by I28 columns
`may not work at all for an array of 128 rows by
`128 columns using the same display media. The
`
`reason for this is that the requirements of dis-
`crimination ratio (nonlinearity), speed of re-
`sponse, duty factor, dwell time, and power
`increase in proportion to the number of rows in
`the array. Typically, one axis is used for timing
`and the other is used for data input. It does not
`matter which one is used for which, except that
`there is some economy in the overall device if
`the smaller of the two is used for timine. For
`purpoie, of this book. the timing axis Iiries are
`called the rows and the data axis lines are called
`the columns. The addressing techniques are dis-
`cussed in more detail in Chao. 5.
`
`1.8.1 Direct Addressing. Direct addressing
`applies to the hard wiring of each pixel to a
`driver amplifier. It is only used with discretes
`and a few alphanumeric characters. Direct ad-
`dressing becomes unacceptable for five or more
`numeric character displays. For example, for
`five seven-segment numeric displays with deci-
`mal, direct addressing would require 40 leads
`plus power return (8 for the seven segments
`plus decimal times 5 characters). If an inte-
`grated circuit were used to drive the display,
`40 pins in the package would be dedicated to
`drive the display which greatly impacts the cost
`of the integrated circuit. Additional pins would
`be required for data-in, clock, and power. With
`
`matrix addressing, the number of leads could be
`reduced to 8 for the seven segments and deci-
`mal plus 5 for the five characters, making 8
`column lines plus 5 row lines for a total of 13
`leads. The afiay cafl be visualized as five rows
`and eight columns, and would be wired accord-
`ingly for matrix addressing. Direct addressing is
`sometimes used on large signs where there is
`adequate space and large amounts of power are
`required.
`
`1.8.2 Scan Addressing. The addressing prob-
`lem can best be understood by studying an
`array of pixels such as would be required for
`a commercial TV picture. There are approxi-
`mately 480 rows (controlled by the raster sync
`signals) and 320 columns (limited by the video
`amplifier bandwidth) for a total of 153,600
`usable addressable pixels in NTSC standard TV.
`To use an individual lead as in the direct-ad-
`dressing technique would require 153,600 leads.
`This is virtually impossible except for a direct-
`view display the size of a billboard. Also, the
`
`trt€--
`
`. t i
`
`*
`
`,:
`
`I :r:
`
`r-t t" '
`
`

`

`Table 1-4 Classification of All Known Addressing Techniques
`
`INTRODUCTION 25
`
`Addressing
`Technique Name
`
`Typical Pixel
`Electrode
`
`Direct
`
`Scan
`
`Grid
`
`shift
`
`Matrix
`
`One lead to each pixel
`with a common signal
`return for power or a
`pair ofleads to each
`pixel
`
`Each pixel defined by
`beam size focused on
`continuous screen of
`pixel media
`
`Each pixel defined by
`the grid hole geom-
`ety; one to four grids
`typically
`
`Each pixel electrically
`connected between
`one row channel and
`a pair of column leads
`
`Each pixel electronically
`connected between
`one row lead and one
`column lead
`
`Number of Amplifiers
`
`Display Applications
`
`Number of rows multiplied
`by the number of columns
`
`Four or fewer alphanumeric
`characters
`
`One for horizontal scan de-
`flection; one for vertical
`scan deflection; one for
`beam intensity control
`
`Variable, dependent upon
`number of grids and sub-
`division of each grid but
`fewer than in matrix
`addressing
`
`Number of rows plus num-
`ber of columns divided
`typically by four for shift
`articulation (assume shift
`is along the rows only)
`Number of rows plus number
`of columns
`
`Cathode-ray tube and some
`flat CRT's
`
`Vacuum fluorescence, some
`flat CRT's, and some gas
`discharge technqiues
`
`Uniquely used with some gas
`discharge and plasma panels
`
`Possible with all flat-panel
`technologies with high dis-
`crimination ratio (large
`nonlinearity)
`
`jJst of completing all the connections, routing
`r-l the wires, and assembling all the amplifiers
`-s prohibitive. The best technique is scan ad-
`::essing, which unfortunately adds depth to the
`::splay. Scan addressing is uniquely integral to
`:re CRT and to date has not been successfully
`:rplied to a flat-panel display except in flat
`CRTs.
`
`1.8.3 Grid Addressing. The number of line
`:rivers in matrix-addressing display arrays is a
`srgnificant cost factor. Grid addressing is used
`:o reduce the number of line driverseven further
`rt the cost of increasing the physical structural
`:omplexity. The grids must all be electroded
`rnd constructed with holes. The display media
`reed not possess a nonlinearity when grid
`iddressing is used. However, the media must be
`:ensitive to charged particles which can be
`,'ontrolled with a grid, such as gas discharge
`:riming particles, electrons, or ions. Grid ad-
`Jressing does not have the partial-selection
`problem that matrix addressing has. Each grid
`lttectively adds another electrode to each pixel.
`However, the array must be addressed pixel-
`rt-a-time or row-at-a-time to prevent direct
`
`cross-coupling as with matrix addressing. The
`name "grid" is used because the grid structure
`function is analogous to the grid of a triode
`vacuum tube.
`
`1.8.4 Shift Addressing. Another way to re-
`duce the number of line drivers even further is
`with the shift-addressing technique. Typically,
`the data are introduced in parallel in all the
`columns of one row at the left side of the dis-
`play and shifted to the right. The gas-discharge-
`controlled switching characteristics are particu-
`larly suited for this approach. It is not the
`nonlinearity but the gas switching or priming
`properties that permit shifting of the input
`information. Channels may be constructed along
`each column to contain the discharge and pre-
`vent column-to-column crosstalk. After a gas
`discharge has been started in a gas-filled column
`channel, priming particles drift and diffuse
`along the column (data) channel to the next
`row (timing), lowering its tiring voltage. When
`the scanning voltage is applied to a row, the
`pixel that has been primed turns on, and the
`pixel that has not been primed remains off.
`In this manner, the gas discharge can be articu-
`
`Ints of dis-
`eed of re-
`nd power
`of rows in
`tor timing
`It does not
`rxcept that
`ll device if
`iming. For
`is lines are
`s are called
`ues are dis-
`
`addressing
`pirel to a
`h discretes
`Direct ad-
`ve or more
`ample, for
`with deci-
`e -10 leads
`r segments
`,f an inte-
`re display,
`'dicated to
`:ts the cost
`pins would
`rg er. With
`ls could be
`; and deci-
`making 8
`otai of 13
`i five rows
`'ed accord-
`ldressing is
`re there is
`power are
`
`sing prob-
`udfing an
`quired for
`e approxi
`raster sync
`the video
`i 153,600
`ndard TV.
`direct-ad-
`.600leads.
`r a direct-
`Also, the
`
`-lE
`
`

`

`26 FLAT-PANEL DISPLAYS AND CRTs
`
`lated along the channel by means of four inter-
`laced and interconnected row-line drivers. With
`the shift-addressing technique, additional time
`is needed to shift the data into the display.
`Minimizing columns saves on the number of
`amplifiers-minimizing rows saves addressing
`time. Here the rows run vertically and the col-
`umns run horizontally.
`
`1.8.5 Matrix Addressing. Matrix addressing is
`
`the most commonly used method for flat-panel
`displays. In comparison with direct addressing,
`the number of leads is reduced from the product
`of the number of rows and columns to the sunr
`of the number of rows and columns. The over-
`all physical construction is quite simple. How-
`ever, the display media must possess a strong
`nonlinear characteristic to prevent partial selec-
`tion of the nonaddressed pixels, and the array
`must be addressed pixel-at-a-time or line-at-a-
`time to prevent direct cross-coupling. Examples
`of display media that inherently possess a strong
`nonlinearity found to be most suitable for
`matrix addressing are light-emitting diodes,
`thin-film electroluminescence, and gas
`ac
`discharge.
`If the media does not inherently possess
`sufficient intrinsic nonlinearity, as for example
`with liquid crystallinity and electrochromism,
`active electronic components must be added at
`each pixel. This has been successfully accom-
`plished using transistors and/or diodes. How.
`ever, complexity has now been added at each
`pixei. The necessary nonlinearity has also been
`achieved by introducing another material such
`as nonlinear resistor films of ZnO or ferroelec,
`tric wafers to act in concert with the display
`media to render a net nonlinear response. Mild
`nonlinear characteristics are realizable with
`liquid-crystal materials, permitting matrix ad-
`dressing for small arrays.
`When something is added to the display media
`to achieve matrix addressability, it provides
`"extrinsic matrix addressing." Otherwise it is
`simply matrix addressing or intrinsic matrix
`addressing. The adjectives "extrinsic" and
`"intrinsic" are analogous to extrinsic and intrin-
`sic semiconductor materials. An extrinsic semi
`conductor is one where a dopant has been added
`to get the desired semiconductor properties. An
`intrinsic semiconductor inherently has the
`desired properties without adding a dopant.
`
`___--
`
`1 . 9 D I S P L A Y D E V I C E D E V E L O P M E N T
`
`Display device development requires a sustained
`effort of advanced technical talent over an ex-
`tended period of time. The effort requires the
`appropriate balance of research, engineering,
`manufacturing, marketing, finance, and manage-
`ment. A single organization with a grasp of the
`total technical problem, the stability for a pro-
`longed development cycle, and the proper blend
`of corporate functions is indeed rare.
`Moreover, a display is only a component.
`Production orders for displays come only after
`production of the product using the display has
`been committed to. After the display prototype
`is released for product application, it takes
`three years at a minimum until production
`quantities are ordered. The reasons for this are
`imbedded in corporate annual planning and
`budgeting procedures. There are three phases
`in new-product development, each of which
`takes a significant increase in commitment of
`company resources and financial support. The
`first year or phase is spent by the company, or
`organization responsible for the product, in eval-
`uating the display and designing the product and
`making breadboards of the product or critical
`parts of the product. The second year or phase
`is spent rnaking several engineering prototypes
`meeting functional requirements and evaluating
`them internally. The third year or phase is spent
`making pilot line units to form , fit, and function
`for limited sales and evaluation by product cus-
`tomers and users, planning production, anc
`making marketing evaluations for prodution
`recommendations. Production could commence
`the fourth year. The production order for the
`display component comes only after the com-
`mitment to production and sales have been
`made.
`The three-or-more-year delay from display
`prototype delivery to receipt of production
`order is a real negative aspect in any business
`plan for display development or in any present-
`value analysis or return-on-investment analysis.
`If a large investment is needed during the display
`prototype phase, the aspect of not getting pro-
`duction orders until three years after the first
`prototypes are delivered turns most investors
`away to greener pastures.
`The development of a new display technology
`is often very long and financially and technically
`
`== =-=
`
`4
`
`

`

`i.quence. When this signal is synchronized with
`':.e addressing timing signal, the exact row and
`. lumn location of the light pen is known, as-
`-ning pixel-at-a-time addressing. This tech-
`-..iue is used with raster-addressed CRTs.
`Coupling through the display may be done
`.:rh a light pen. The light pen emitsUV at the
`::rropriate wavelength which can be made to
`'-:gger the operation of pixels which had been
`:r-'ited up to just below operating threshold.
`lris has been demonstrated with EL and GD
`:::plays. The electronics detect the extra cur-
`-:nt that flows in the corresponding row and
`. iumn lines due to the new operating pixel.
`
`2.6.4 Electronics. The electronics are gener-
`:.-r organized into several parts