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  • 5/19/2018 Revistas IEEE.pdf

    1/9

    COUUTUTARY

    40

    GrGABrr ErneRruer

    AND

    100

    Glcnelr

    ErHenruer:

    THe DvELoPMENT

    oF

    a

    FLrxIaIe

    AncHITEcTURE

    Jonru D'AuBRostA

    lntroduction

    In December

    2007 the IEEE

    Standards Asso-

    ciation approved

    the formation

    of the

    IEEE

    P802.3ba Task

    Force, which

    was chartered

    with

    the development

    of 40

    Gb

    Ethernet

    and

    100

    Gb

    Ethernet.

    The decision

    to do both rates

    of Ether-

    net

    was

    scrutinized by the

    industry

    at the time,

    but ultimately

    the Higher

    Speed Study

    Group

    provided

    a vital forum

    for

    the

    stakeholders

    in the

    next

    generation

    of Ethernet

    to debate this

    very

    issue.

    The

    fact that this

    debate

    actually

    occurred

    is in itself a

    testament

    to

    the success

    of Ethernet.

    Networking

    applications,

    whose

    bandwidth

    requirements

    are doubling

    approximately

    every

    18 months,

    have

    greater

    bandwidth

    demands

    than

    computing

    applications,

    where the bandwidth

    capabilities

    for

    servers

    are

    doubling

    approximate-

    ly

    every 24

    months.

    The impact

    of this difference

    in

    bandwidth

    growth

    is illustrated

    in Fig. 1.

    It

    is

    clear from

    these trend

    lines that

    if

    Ethernet

    is

    to

    provide

    a

    solution for both

    the computing

    and

    network

    application

    space, it needs

    to

    evolve

    past

    its

    own

    tradition

    of

    10x

    leaps

    in operation

    rates

    with

    each

    successive

    generation.

    The

    decision

    to do

    two

    rates

    was

    not

    taken lightly

    by

    par-

    ticipants

    in the Higher

    Speed

    Study

    Group.

    In hindsight,

    this

    author,

    who

    was

    in the

    thick of this

    debate, feels

    that

    the

    deci-

    sion

    to do

    both

    40

    Gb

    and

    100

    Gb

    Ethernet

    was

    the correct

    decision

    for Ethernet.

    Ultimately,

    it was

    the

    IEEE standards

    development

    process

    itself

    that

    proved

    to be the

    key

    to

    resolv-

    ing

    this

    difficult

    decision.

    Support of two

    differing

    data rates

    as

    well

    as

    different

    physical

    layer

    specifications

    selected

    for this

    project

    presented

    the task

    force

    with

    a dilemma.

    The

    task

    force needed

    to

    develop

    an architecture

    that

    could support

    both rates

    simulta-

    neously

    and

    the

    various

    physical

    layer

    specifications

    being

    developed

    today, as

    well as what

    might

    be

    developed

    in

    the

    future.

    This

    column

    will

    provide

    the reader

    with

    insight

    into

    the

    IEEE

    P802.3ba

    architecture,

    and

    highlight

    its inherent

    flexibility

    and

    scalability.

    The

    Physical

    Layer

    Specifications

    Closely

    examining

    the

    different

    application

    spaces

    where

    40

    Gb

    and

    100

    Gb Ethernet

    will

    be used

    led

    to

    the

    identifica-

    tion

    of the physical

    layer

    (PHY)

    specifications

    being targeted

    by

    the Task

    Force. For

    computing

    applications,

    copper

    and

    optical

    physical layer solutions

    are

    being developed

    for

    dis-

    tances

    up to 100

    m

    for

    a

    full range

    of

    server

    form

    factors

    including

    blade,

    rack,

    and

    pedestal

    configurations.

    For

    net-

    work aggregation

    applications,

    copper

    and

    optical

    solutions

    are

    being

    developed

    to

    support

    distances

    and

    media types

    appropriate

    for

    data

    center networking,

    as well

    as service

    provider

    intra-office

    and

    interoffice

    connection.

    Table

    1

    provides

    a summary

    of the

    different

    PHY specifi-

    cations

    that were

    ultimately

    targeted

    by

    the task

    force

    with

    their

    respective

    port

    type names.

    Below

    is a description

    of

    each

    of the

    different

    physical

    medium

    dependents

    (PMDs):

    .

    40GBASE-KR4:

    This

    PMD

    supports backplane

    transmis-

    sion

    over

    four

    channels

    in

    each

    direction

    at 40

    Gb/s. It

    leverages

    the l0GBASE-KR

    architecture,

    already

    devel-

    oped channel

    requirements,

    and

    PMD.

    .

    40GBASE-CR4

    and 1O0GBASE-CR10:

    The

    40GBASE-

    CR4 PMD

    supports

    transmission

    at 40

    Gb/s across four

    dif-

    ferential pairs

    in each direction

    over a twin

    axial

    copper

    cable

    assembly.

    The

    1OOGBASE-CR10

    PMD

    supports

    transmission

    at

    100

    Gb/s

    across

    10

    differential

    pairs

    in each

    direction

    over a twin

    axial copper

    cable

    assembly.

    Both

    PMDs

    leverage

    the lOGBASE-KR architecture,

    already

    developed

    channel

    requirements,

    and

    PMD.

    .

    4OGBASE-SR4

    and

    100GBASE-SR10:

    This

    PMD

    is based

    on 850 nm

    technology

    and supports

    transmission

    over

    at

    Ieast

    100

    m

    OM3

    parallel

    gigabit

    per

    second.

    The

    effective

    date rate per

    lane

    is

    10

    Gb/s. Therefore,

    the

    40GBASE-

    SR4 PMD

    supports

    transmission

    of 40

    Gb

    Ethernet

    over

    a

    parallel gigabit

    per

    second

    medium

    consisting

    of four paral-

    lel

    OM3 fibers

    in

    each direction,

    while the

    100GBASE-

    SR10 PMD

    will support

    the

    transmission

    of

    100

    Gb

    Ethernet

    over a

    parallel

    gigabit

    per

    second

    medium

    consist-

    ing of 10 parallel

    OM3

    fibers

    in

    each

    direction.

    .

    4OGBASE-LR4:

    This

    PMD

    is

    based

    on 1310

    nm

    coarse

    wavelength-division

    multiplexing

    (CWDM)

    technology

    and

    over

    at least

    10 km

    over single-mode

    is based

    on the

    ITU

    G.694.2 specifi-

    ngths

    used

    are

    1270,1,290,1310,

    arrd

    1330

    nm.

    The

    effective

    data rate per

    lambda

    is 10

    Gb/s,

    which

    will help

    maximize

    reuse

    of existing

    10G PMD

    tech-

    nology.

    Therefore,

    the 40GBASE-LR4

    PMD

    supports

    transmission

    of 40

    Gb Ethernet

    over

    four wavelengths

    on

    each

    SMF in

    each direction.

    .

    100GBASE-LR4:

    This

    PMD is

    based

    on

    1310

    nm

    dense

    WDM

    (DWDM)

    technology

    and

    supports

    transmission

    of

    at least

    10 km

    over single-mode

    gigabit

    per

    second.

    The

    grid

    is

    based

    on

    the ITU

    G.694.1

    specification,

    and

    the

    wavelengths

    used

    are 1295,1300,1305,

    and

    1310

    nm. The

    (Continued

    on

    page

    510

    1 00 Gigabit

    Ethernet

    40 Gigabit

    Ethernet

    1

    0

    Gigabit

    Ethernet

    I

    Gigabit Ethernet

    I

    Figure

    1. Bandwidth growth

    forecasts.

    IEEE

    Communications

    Magazine.

    March

    2009

  • 5/19/2018 Revistas IEEE.pdf

    2/9

    I

    Table

    1.

    Summary

    of IEEE

    P802.3ba physical

    layer

    specifications.

    (Continued

    from

    page

    S8)

    effective

    data rate

    per

    lambda

    is 25

    Gb/s. Therefore,

    the

    100GBASE-LR4

    PMD

    supports transmission

    of

    100

    Gb

    Ethernet

    over four

    wavelengths

    on

    each SMF in

    each

    direc-

    tion.

    .

    100GBASE-ER4:

    This

    PMD

    is

    based

    on

    1310

    nm

    DWDM

    technology

    and

    supports transmission

    over at least

    40 km

    over

    single-mode

    gigabit

    per

    second.

    The

    grid

    is based

    on

    the ITU

    G.694.t

    specification,

    and

    the wavelengths

    used

    are

    1295,1300,

    1305, and

    1310

    nm.

    The

    effective

    data rate

    per

    lambda

    is

    25 Gb/s. Therefore,

    the

    1O0GBASE-LR4

    PMD

    supports

    transmission

    of 100

    Gb Ethernet

    over four

    wavelengths

    on each

    SMF in

    each

    direction.

    To

    achieve

    the

    40

    km

    reaches

    called for,

    it

    is

    anticipated

    that implementa-

    tions

    may

    need

    to include

    semiconductor

    optical

    amplifier

    (SOA)

    technology.

    The

    Architecture

    During

    the

    proposal

    selection

    process

    for

    the

    different

    PHY

    specifications,

    it

    became

    evident

    that

    the task force

    would

    need

    to

    develop

    an

    architecture

    that

    would be

    both

    flexible

    and scalable

    in

    order

    to simultaneously

    support

    40

    Gb

    f

    Figure

    2.

    IEEE

    P802.3ba

    architecture.

    and

    100

    Gb

    Ethernet.

    These

    architectural

    aspects

    would

    necessary

    in

    order

    to deal

    with the PHY

    specifications

    bein

    developed

    by the

    IEEE P802.3ba

    Task

    Force,

    as

    well as

    tho

    that

    may

    be developed

    by

    future

    task forces.

    Figure

    2

    illustrates

    the

    overall

    IEEE

    P802.3ba

    architectu

    that

    supports both

    40

    Gb and

    100

    Gb Ethernet.

    While all

    the PHYs

    hve

    a

    physical

    coding

    (PCS)

    sublayer, physic

    medium

    attachment

    (PMA)

    sublayer,

    and

    physical

    mediu

    dependent (PMD)

    sublayer,

    only

    the copper

    cable (-CR)

    an

    backplane (-KR)

    PHYs

    have

    an

    auto-negotiation

    (AN)

    su

    layer

    and an

    optional

    forward

    error

    correction

    (FEC)

    subla

    er.

    For

    40 Gb

    Ethernet

    the

    respective

    PCS

    and PMA

    subla

    ers need

    to

    support

    PMDs

    being

    developed

    by

    the

    IEE

    P802.3ba

    Task Force

    that

    operate

    electrically

    across

    four

    d

    ferential pairs

    in

    each

    direction,

    or optically

    across

    four

    op

    cal

    fibers

    or four

    wavelengths

    in

    each direction.

    It

    w

    realized,

    however,

    that

    in

    the

    future,

    the IEEE

    p802.3b

    architecture

    might

    need

    to support

    other

    40

    Gb

    PMDs

    th

    could operate

    either

    across

    two

    lanes

    or

    a single

    serial

    lan

    Likewise,

    for 100

    Gb Ethernet

    the

    respective

    PCS

    and

    pM

    I EV"1.

    need

    to

    support

    PMDs

    being

    developed

    by

    th

    IEEE

    P802.3ba

    Task

    Force

    that

    operate

    electrically

    across

    differential

    pairs

    in

    each

    direction,

    or

    optically

    across

    10 op

    cal

    fibers

    or

    four

    optical

    wavelengths

    in

    each

    direction.

    It w

    also

    realized

    that in

    the future

    the

    IEEE

    P802.3ba

    archite

    ture might

    need

    to

    support

    other

    100

    Gb PMDs

    that

    mig

    potentially

    operate

    across

    five

    lanes,

    two lanes,

    or a sing

    serial

    lane.

    The

    task

    force

    leveraged

    the

    relationship

    between

    th

    respective

    sublayers

    to

    develop

    the

    flexible

    and

    scalable

    arch

    tecture

    it

    needed

    for 40

    Gb and

    100

    Gb Ethernet,

    as

    well

    for

    future

    rates

    of Ethernet.

    _

    The

    PCS

    sublayer

    couples

    the

    respective

    media indepe

    dent,interface

    (MII)

    to the

    PMA

    sublayer.

    For

    40

    Gb Ethe

    net,

    the

    MII

    is

    called

    XLGMII,

    and for

    100

    Gb Ethernet,

    th

    MII

    is called

    CGMII.

    The

    PMA

    sublayer

    interconnects

    th

    PCS

    to the

    PMD

    sublayer.

    Therefore,

    the

    functionalit

    embedded

    in

    the PCS

    and PMA

    represent

    a two-stage

    proces

    that

    couples

    the respective

    MII

    to

    the

    different

    pMDs

    tha

    were

    envisioned

    for

    40

    Gb and 100

    Gb

    Ethernet.

    Furthe

    more,

    this scheme

    can

    be scaled

    in

    the future

    to

    support

    th

    next

    higher

    rates

    of Ethernet.

    As

    noted

    above,

    the PCS

    sublayer

    couples

    the respectiv

    MII

    to the PMA

    sublayer.

    The

    aggregate

    stream

    coming

    from

    (Continued

    on

    page

    51

    sl0

    IEEE

    Communications Magazine

    .

    March

    200

  • 5/19/2018 Revistas IEEE.pdf

    3/9

    f

    Aggregate

    stream

    of

    64l66b

    words

    ---

    rl

    -

    pCS

    lane

    I

    .

    PCS

    lane 2

    5imple

    66b word

    round

    robin

    PCS

    lane

    n

    \-

    -,'

    \

    -.'

    Lane

    markers

    CotvrurruTARy

    I

    Figure

    3. PCS

    lane

    distibution

    concept.2

    (Continued

    from

    page

    510)

    the

    MII

    into

    the

    PCS

    sublayer undergoes

    the

    6481668 cod

    scheme

    that

    was

    used

    in 10

    Gb

    Ethernet.

    Using

    a round-rob

    distribution

    scheme,

    66-bit

    blocks

    are

    then

    dislributed

    acr

    PCS

    lanes

    for 100

    Gb Ethernet.

    The

    number

    of

    pCS

    lanes

    each rate

    er of

    lan

    that

    migh

    given

    ra

    and

    then

    Jof

    tho

    implemen

    Gb

    Ethernet

    will

    four

    channels

    or

    PCS

    lanes

    for

    10

    employ

    7,

    2,

    4,

    5,

    each

    direction..

    (Continued

    on page

    51

    MAC

    client

    MAC

    control

    (optional)

    MAC

    Reionciliation

    CGMII

    PCS

    PMA

    (20:10)

    CAUI

    PMA

    (10:4)

    PMD

    MD

    Medium

    Z

    1 OOGBASE-LR4

    I

    Figure

    4. Example

    implementation

    of L77GBASE-LR4.

    IEEE

    Communications

    Magazine

    .

    March

    20

  • 5/19/2018 Revistas IEEE.pdf

    4/9

    (Continued

    from

    page

    510)

    I

    Figure

    5.IEEE

    P802.3ba

    timeline.

    Lowesf

    cosfper

    clean

    in

    the

    industry

    Podable

    Palm

    sized

    package

    Etrective

    Wet

    or Dry Cteaning

    Wide

    range

    connectors

    and

    polish

    types

    More

    than

    500x

    cleanngs

    pet

    unit

    We

    hope

    to

    E6e

    you

    at

    Booth

    #

    3030

    for

    a demonsttation

    ,,

    (

    ,.

    ,"

    o:;;,i

    ",

    c"-,.;.;,.o\. .

    h"Rr

    Need

    a

    helping

    hand

    to

    keep

    your

    fibers

    clean?

    CAUI

    interface,

    which

    is

    then

    mult

    plexed

    into

    four

    lambdas,

    each

    with

    effective

    data

    rate

    of

    25

    Gb/s,

    and

    ca

    ried

    across

    10

    km

    of

    SMF.

    Conclusion

    The

    IEEE

    P802.3ba

    Task

    Force

    ha

    ls

    prepanng

    a

    request

    to

    go

    to

    workin

    Group

    Ballot,

    the

    nexistage

    in

    th

    development

    of

    40

    Gb

    and

    10

    Gb

    Eth

    ernet.

    The

    adopted

    schedule

    for

    the pro

    ject

    is shown

    in

    Fig.

    5.

    Regardl

    regarding

    th

    this project

    fashion

    and

    dards

    approval

    in

    June

    2010.

    Further

    more,

    the

    architecture

    this

    task

    force

    ha

    adopted

    will

    allow

    Ethernet to

    scale t

    even

    greater

    speeds

    in

    the

    future,

    which

    should

    interest

    those

    parties

    alread

    starting

    to

    call

    for

    Terabit

    Ethernet.

    SEIKOH

    GIKEN

    www.SeikohGiken,com

    [email protected]

    I

    f 7 7

    O

    -27

    9-6602

    IEEE

    Communications

    Magazine. March

    20(D

  • 5/19/2018 Revistas IEEE.pdf

    5/9

    applications

    RNER:t

    Derek J. Walvoord

    and

    Roger

    L. Easton, Jr.

    scription to assist scholars

    in

    reading

    damased characters

    and

    words.

    MULTISPECTRAL IMAGING

    ACQUtStTtON

    Both the erased Archimedes

    text

    (the

    underwriting)

    and

    the Euchologion

    text

    (ovenruriting)

    were written

    using

    iron

    gall

    ink.

    The

    original

    proposal

    for

    imasingi

    was directed

    at capturing

    and

    enhancin

    a small color

    difference between

    the

    two

    texts

    [Figure

    2(a)]. Each

    page

    was imaged

    under

    two illuminations

    (ultraviolet

    light

    at I

    :

    365

    nm

    and low-wattase

    tunssten

    lights) through five

    different bandpass

    fil-

    ters

    (blue,

    6lreen,

    red, and two IR bands)

    [2]

    to

    create a

    multispectral

    data set for

    subsequent

    processin.

    LEAST-SQUARES

    SPECTRAL

    UNMIXING

    The

    initial

    approach

    used to

    providr

    scholars with enhanced fishlrnsds5

    te$

    Digital

    Transcription

    of the

    Archimedes

    Palimpsest

    he recent

    and

    concurrent

    development

    of

    the technolo-

    gy

    of

    optical

    sensors

    and dig-

    ital

    computers,

    and

    the

    consequent decreases

    in

    their

    cost,

    makes

    possible

    for

    their

    usae

    in

    the

    transcription

    of

    historical manu-

    scripts. Some

    of these documents

    may

    have been

    deliberately erased and

    over-

    written to

    make

    apalimpsest,

    which

    may

    further

    suffer

    from

    many

    other

    forms

    of

    deterioration.

    The

    Archimedes Palimpsest

    includes

    partial

    texts

    from

    seven treatises

    by

    Archimedes, including the only extant

    copy in

    the original

    Greek

    of his

    most

    famous

    work Or

    Floating Bodies,

    the

    only copies in any form of On the

    Method

    of Mechanical Theorems

    (which

    provides

    insight

    into his mathematical

    thought

    process)

    and of Stomachion

    (which

    has been

    identified

    to

    be a very

    early study in combinatorics

    [1]).

    In

    this article

    we

    present

    the

    workflow and

    methods involved

    in

    the digital

    tran-

    scription

    of

    the Archimedes

    palimpsest.

    THE PALIMPSEST

    The

    original codex of Archimedes

    texts

    was copied

    onto

    parchment

    from

    other

    sources in

    the

    10th

    century

    to make a

    bound book.

    Durins

    the

    Fourth

    Crusade

    inL204, the

    bookwas

    disbound,

    the

    origi-

    nal text

    was erased, and the

    pages

    were

    cut

    in

    half. Along

    with

    pases

    from

    the

    other manuscripts,

    the

    erased Archimedes

    pages

    were then overwritten

    with

    the

    Euchologion

    (a

    Christian

    prayer

    book). In

    1906, Johan

    L. Heiber,

    a Danish

    philolo-

    gist,

    identified

    that the undertext of

    the

    palimpsest

    was the

    work

    of

    Archimedes,

    and he had

    65

    photographs

    made

    of the

    book.

    The

    manuscript

    resurfaced in

    1998

    when Christie's

    auctioned

    the

    codex

    for

    US$2

    million dollars to an

    anonymous

    American

    collector,

    who

    has lent it

    to the

    Walters Art Museum

    in Baltimore,

    Maryland,

    and

    generously

    funded

    its con-

    servation,

    imaging, and study. The condi-

    tion of

    the

    book

    has deteriorated

    markedly

    since Heiberg's work, as shown

    by the comparison

    of a Heiber

    photo-

    raph

    to the current

    appearance

    of

    the

    same

    page

    in Figure

    1.

    The manuscript has

    reat

    historical

    importance,

    but

    unfortunately

    much

    of

    the text is

    very

    difficult to

    discern due to

    its

    poor

    condition. Our

    underlying

    objec-

    tive in the transcription of the

    Archimedes

    palimpsest

    was to apply

    mod-

    ern imainS

    techniques

    to

    preserve

    the

    manuscript and

    to

    assist transcription by

    scholars. In this

    process,

    we used multi-

    spectral image

    collection

    and

    processin,

    which

    facilitated

    transcription

    of

    nearly

    8070

    of

    the

    manuscript,

    and

    a digital

    imagin

    tool that

    used

    this

    partial

    tran-

    (a)

    (b)

    [FlGll

    Leaf 57 verso of the Archimedes

    palimpsest:

    (a)

    photograph

    from 1905

    by

    Heiberg

    and

    (b)

    condition in 2007, showing the damage

    that occurred in 100

    years

    (Courtesy

    of the owner

    of the

    Archimedes

    palimpsest.)

    iqitat

    object

    rdmtiliq

    lo.1 logtuspzooa.szgoo

    IEEE

    SIGNAL PROCESSING

    MAGAZINE

    [1OO]

    JULY

    2OO8

    1

    053-5888/08/125

    o(E@G

  • 5/19/2018 Revistas IEEE.pdf

    6/9

    lJ.

    Walvoord

    L.

    Easton,

    Jr.

    ars

    in

    readin

    ords.

    NG

    nedes

    text

    (the

    uchologion

    text

    n

    using

    iron

    gall

    sal

    for

    ima$ing

    g

    and

    enhancing

    between

    the

    tuo

    pa6ie

    was

    imaged

    (ultraviolet

    ligbt

    h,attage

    tunsten

    rcnt

    bandPass

    fi '

    nd

    two

    IR

    bandst

    rtral

    data

    set

    for

    E

    used

    to

    Provide

    I

    fuchimedes

    tef

    rorn

    1906

    bY

    in

    100

    Years'

    employed

    a

    supervised

    least-squares

    spec-

    tral

    unmixing

    algorithm

    [3].

    After regis-

    tering

    each

    band

    in the multispectral

    data, an observer

    selected

    giroups

    of

    pixels

    that

    belonged

    to four object

    classes:

    over-

    writin,

    underwriting,

    parchment,

    and

    mold. The imase

    set

    was

    processed

    to

    estimate

    the

    class

    membership

    of

    each

    pixel.

    Figure 2(b) shows leaf

    28 verso

    (the

    reverse

    side of leaf 28) of lhe Euchologion

    under normal

    illumination

    and

    the

    image

    of

    the

    class map for

    the

    original

    Archimedes text. Note

    that the

    ray

    value

    of

    each

    pixel

    is

    a measure of

    the member-

    ship in this class; underwriting

    is mapped

    to

    white

    and other classes

    to

    black.

    The

    image shows

    how the method

    successful-

    ly stripped off much

    of

    the ink from

    the

    Euchologion,

    leaving only the remnants

    of

    the original Archimedes

    text.

    However,

    the

    additional noise

    in

    the

    processed

    imaes was annoying to the

    scholars

    who

    were transcribing the

    text.

    In

    addition,

    any Archimedes

    character

    that is

    partially

    obscured

    by

    a Euchologion

    character

    showed

    distinct breaks

    in

    the ink

    that

    might

    lead

    to ambiguous

    readings. The

    scholars desired a much

    simpler

    result

    that

    preserved

    the visibility

    of both

    writ-

    ings,

    while distinguishing the texts in

    some manner.

    PSEUDOCOLOR

    IMAGE

    ENHANCEMENT

    After receiving

    the feedback from

    the

    scholars,

    the imaging

    team

    developed

    a

    processing

    method to

    produce

    pseudocol-

    or

    images

    that

    allocated different

    colors to

    the

    underwritin,

    overwriting,

    and

    parch-

    ment

    classes. The

    process

    is

    based on the

    observation

    that the undenvriting

    is bare-

    ly

    detectable

    under

    red

    light,

    while

    both

    texts are visible when

    viewed

    under

    ultra-

    violet

    light.

    W

    illumination

    generates

    vis-

    ible fluorescence

    in

    the

    parchment,

    which

    enhances

    the

    contrast of

    both

    texts

    when

    viewed through a blue filter.

    A

    pseudocol-

    or

    image

    is

    constructed by

    assigning the

    red channel

    of the

    image

    under tungsten

    illumination

    to its

    red

    channel and the

    blue channel under

    UV illumination

    to its

    green

    and

    blue channels. The reddish

    Archimedes

    text appears dark in

    the

    sreen

    and blue channels and

    brighter in red

    light,

    thereby

    showing a

    distinct

    reddish

    tint in

    the

    pseudocolor

    image.

    The

    Euchologion

    text is

    dark

    in

    all three chan-

    nels

    and

    so appears in

    a dark neutral

    shade. This color cue

    assists the scholars

    in

    the

    transcription

    of the text.

    An exam-

    ple

    of a

    pseudocolor

    imase is

    shown in

    Figure

    2(c).

    THE TRANSCRIPTION

    SYSTEM

    While the

    pseudocolor

    system

    sufficiently well for

    much of the

    text,

    transcription

    of

    some

    pase

    problematic

    due to severe

    dam

    interactive

    image

    processins

    and

    system has

    been

    developed

    to

    (a)

    (a)

    lmages

    of a section of

    the

    palimpsest

    under

    illumination

    with

    wavelen

    sing from

    right

    to

    left.

    The

    text

    becomes more visible

    as the wavelength

    o

    illumination

    decreases.

    (b)

    A

    comparison

    of

    the original strobe illuminated

    image

    28

    verso before and

    after least-squares

    spectral

    unmixing.

    (Courtesy

    of the owne

    Archimedes

    palimpsest.)

    (c)

    Pseudocolor

    image

    of disbound leaves

    98

    verso

    -

    102

    of

    the Euchologion

    (Archimedes

    treatise On Spiral Lines).

    The horizontal

    Archimed

    and the diagram appear

    with reddish

    tints,

    while

    the

    prayer

    book text appears

    b

    (Courtesy

    of the owner

    of the

    Archimedes

    palimpsest.)

    85888/08/$25

    00@200

    IEEE

    SIGNAL

    PROCESSING

    MAGAZINE I,I01tr JULY

    2OO8

  • 5/19/2018 Revistas IEEE.pdf

    7/9

    CORNER

    ii

    continued

    additional

    information

    to the scholar

    and

    utilize

    his

    or

    her

    feedback.

    The

    process...

    ing

    uses

    a

    series of

    spatial correlations

    between character

    fragments in

    the

    images

    and a

    trainins

    library

    of charac-

    ters

    extracted

    from relatively

    clean

    regions

    in the manuscript.

    A high-level

    diaram

    of the

    overall

    transcription

    sys-

    tem is

    shown in Figure

    3(a) and a low-

    level diagram

    of the

    processins

    is

    shown

    in Figure

    3(b).

    FEATURE

    EXTRACTION

    The features

    used

    for

    character

    classifica-

    tion

    are

    extracted usins

    advanced

    corre-

    lation techniques

    [Figure

    3(b)].

    Several

    matching

    schemes are

    used

    simultane-

    ously

    to account for

    variability in

    the

    spatial

    structure

    of

    the

    character regions

    under

    scrutiny, thus

    providing

    adequate

    features

    for classification.

    ADVANCED

    CORRELATION

    FILTERING

    The

    feature

    extraction

    process

    benefits

    heavily

    from the inclusion

    of

    filter

    designs that incorporate

    a set of training

    imaes

    into the filter

    mask development.

    Composite

    correlation designs use

    a

    trainin

    set

    from

    a

    particular

    class

    to

    pro-

    vide

    some

    degree of distortion

    tolerance

    for

    within-class

    variation. The maximum

    aueroge

    correlation

    height

    (MACH)

    filter

    [4],

    when

    used

    with other classical

    filter-

    ing

    designs,

    provided

    acceptable

    correla-

    tion results

    for

    feature

    extraction

    using

    the

    palimpsest

    imasery.

    The MACH

    filter

    has

    the form

    h

    :

    y(S-t

    I)-lm,

    (1)

    where h is the

    vector representation

    of

    the filter

    transfer

    function,

    m

    is the

    vec-

    tor containing

    the mean

    trainins

    image

    Fourier

    transform,

    I is

    the identity

    matrix,

    and

    7

    is a normalization

    con-

    stant.

    Note that lower-case

    bold-faced

    symbols

    represent

    vectors

    while

    upper-

    case symbols refer

    to

    matrices.

    The

    matrix

    S in the MACH

    filter is

    given

    by

    lN

    S:

    ,i=

    )'rX-Mr*1Xi-M).

    (2)

    d.1\

    -

    :l

    where ly'

    is

    the

    number

    of training

    imaes,

    d is

    the

    number

    of

    pixels

    in each

    image, and X

    and M are

    diagonal matri-

    ces

    containins

    the

    th

    training

    Fourier

    transform

    and

    the

    average

    Fourier

    transform, respectively.

    To

    achieve high

    tolerance

    to within-

    class

    distortion,

    the filter is

    designed

    to

    minimize

    the

    averase

    similarity measure

    (ASM)

    between

    output

    correlation

    planes

    for

    each

    of the training

    images

    used

    to

    construct

    the filter

    mask. In

    addition,

    the

    output noise

    uariance

    (ONV)

    is also

    mirr

    imized,,

    and the

    aerage correlation

    height

    (ACH)

    is

    maximized.

    These

    crite-

    ria

    are

    [4]

    ASM:1-\to,t*.rt

    N

    ??-*

    -

    S@,r)12

    :

    h+Sh

    (31

    oNV:

    E{hrch}

    (4t

    ,N

    ACH

    :

    * )-.qt0.

    0t

    t5t

    ]\t

    -

    T:I

    where

    g(m,

    n) is

    the correlation

    plar

    corresponding

    to the

    ith

    training

    imagE

    and

    C is the

    covariance matrix

    of tl-

    input noise

    estimation.

    An

    example

    of

    a

    typical

    correlatim

    plane

    produced

    by

    the

    MACH

    filts

    usir

    Greek characters

    from

    the

    underwriting

    h

    training and

    targets is shown

    in Figure

    4

    Probabilistic

    Network

    (b)

    lFlc3l

    (a)

    Block

    diagram

    of the transcription

    system

    and

    (b)

    detailed

    block diagram

    of

    the

    character

    recognition

    of

    (a).

    Probabilities

    of

    CharacterMord

    Library

    ..:

    Character

    Class %

    Classification

    Sum

    Squared Error

    Character

    Class

    Feature

    Vectors

    ROI

    Autocorrelation

    Feature Vector

    L

    r

    IEEE

    SIGNAL PROCESSING

    MAGAZINE

    1102}

    JULY

    2OO8

  • 5/19/2018 Revistas IEEE.pdf

    8/9

    True

    Class

    (Nontraining)

    v

    [FlG4]

    Example

    of normalized

    correlation

    planes

    generated

    using

    the

    MACH

    filter

    for

    (a)

    true

    class

    targets

    and

    (b)

    false

    class'targetsl

    IACHI

    filter

    ssical

    filter-

    rble correla-

    rtion

    using

    ,f{CH

    filter

    L

    (lt

    sentation

    of

    n

    is the

    rec-

    ining

    irnagp

    he identitl

    ization

    con-

    r

    bold-raced

    rile

    upper-

    trices.

    Thc

    sgiwnh-

    l-- lr-

    rZt

    of

    trainin6

    irclsind

    oonal

    mi-

    rE

    Forrrlr

    4le

    Fouricr

    x

    to

    rib

    ;

    rie

  • 5/19/2018 Revistas IEEE.pdf

    9/9

    applications

    CORNER,:

    continued

    using

    the

    probable

    words

    from

    the

    LUT

    or

    perform

    another

    query

    [81.

    CONCLUSIONS

    We have

    applied

    multispectral

    imaging

    techniques

    and

    character

    recosnition

    methods

    based

    on

    a

    library

    of identified

    characters

    to digitized

    data

    from

    the

    Archimedes

    palimpsest

    in

    a

    unified image

    analysis

    and

    classification

    framework.

    The

    process

    presented

    in

    this

    article

    assisted

    scholars

    in

    their

    transcription

    of

    the

    palimpsest,

    which

    is

    one

    of the

    most

    important

    documents

    in

    the history

    of sci-

    ence.

    Among

    them,

    Reviel

    Netz,

    the

    princi-

    pal

    scholar

    in

    translating

    the

    Archimedes

    text, has

    commented

    very

    positively

    on

    the

    value

    of the

    character

    recognition

    tool.

    In

    addition,

    the

    digital

    transcription

    workflow

    has been

    applied to

    a

    tenth

    century Hebrew

    colophon

    [7]

    and

    even

    outside

    the

    digital

    transcription

    of documents

    (for

    instance,

    it

    is

    currently

    being

    used to

    locate

    centroids

    of registration

    markers

    in

    three-dimen-

    sional

    MRI

    breast imaging).

    ACKNOWLEDGMENTS

    The

    authors

    thank

    the other

    members

    of

    the

    Archimedes

    palimpsest

    imaging

    team, Dr.

    Keith

    Knox

    of

    Boeing

    LTS,

    and

    Dr.

    William

    A.

    Christens-Barry

    of

    Equipoise

    Imaging,

    LLC.

    In

    addition, rte

    thank

    the owner

    of the

    Archimedes

    Palimpsest,

    Dr.

    William

    Noel

    and

    Abigai,

    Quandt

    of the

    Walter's

    Art

    Museum

    i::

    Baltimore,

    and Dr.

    Reviel

    Netz

    ,:

    Stanford

    University.

    Photographs

    of

    tlr

    Archimedes

    Palimpsest

    were

    produce;

    by

    William

    A.

    Christens-Barry

    Roger

    L

    Easton,

    Jr.,

    and Keith

    T.

    Knox.

    AUTHORS

    Derek

    J. Waluoord

    ([email protected]

    r

    nr

    Roger

    L.

    Easton,

    -/r

    ([email protected]

    are

    with

    the

    Chester

    E

    Carlson Cent=:n

    Imaging

    Science

    at

    the

    Rochester

    l-=im

    of

    Technology,

    Rochester,

    New

    Yorli

    REFERENCES

    [1]

    R. Netz

    and

    W.

    Noel,

    The

    Archimedu

    (l.rT

    h/Mr

    York

    DaCapo

    Press,

    2007.

    [2]

    R.L. Easton,

    Jr.

    and

    W Noel,'

    imaging

    of

    the Archimedes

    palim

    Liure

    Mdiaal,

    vol. 45,

    pp.

    3949,

    20M.

    [3]

    J.R.

    Schott.

    Remole

    Sensinq:

    The

    t:-,:.t

    -M

    Approach.

    New\ork:

    Oxford

    Univ.

    prs-

    -'

    '

    -

    t4l

    B.VK.

    Vijaya Kumar,

    A.

    Mahalan=

    an

    illXi

    Juday,

    Conelation

    Pattem

    Recogmitio-_

    lw

    mfru

    Cambridge

    Univ. Press,

    2005.

    t5]

    B.V.K.

    Vijaya

    Kumar

    and

    L-

    -_llrrmum[lil

    ''Performance

    measures

    for

    corr.:-_

    :r'Er,

    Appli

    e d

    Op

    t.,

    v

    ol. 20,

    no. 20,

    pp.

    299 i-j

    "r"Ni_

    .lt#]lliltl

    [6]

    S.J. Russell

    and

    P

    Norvig,,lrda-;-

    A

    Modem

    Approach,2nd

    ed.

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    [7]

    D.

    Walvoord,

    R.L.

    Easton.

    lr.. ir

    I,m.

    ruu]lL,

    Heimbueger.

    ''Enhancement

    and

    ;ire

    ulq"

    tion

    of the

    erased

    colophon

    o: ,i.:gmouttlUil

    Hebrew

    prayer

    book,"

    Proc.

    SP1f.

    r':u

    ffi

    pp.

    157-166.

    [8]

    D.J.

    Walvoord,

    R.L.

    Easton.

    -Ir--

    :m 1*

    'Adding

    contextual

    information

    ::

    :m

    ter recognition

    on the

    Archimeda

    :almmsm"

    SPIO,

    vol.

    6500,

    p.

    650008-1, 2tr,ri

    Query Results

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    inference

    across

    six

    Rors.

    (b)

    lllustration

    of the

    passing

    of contextual

    linowledge

    as

    evidence

    into

    the character

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    block.

    (a)

    BOI

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    5 ROt

    6

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    7.57

    IEEE

    SIGNAL

    PROCESSING

    MAGAZINE

    1104' JULY 2OO8