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Printing Devices - · PDF filePrinting Devices Lecture 10 Ink Jet ... Dye Sublimation Halftoning Dithering Error Diffusion. Plotter Dot Matrix Printer ElectroMagnet ... an electrostatic

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Text of Printing Devices - · PDF filePrinting Devices Lecture 10 Ink Jet ... Dye Sublimation...

  • Printing Devices

    Lecture 10

    Ink Jet PrintersLaser PrintersThermal PrintersDye SublimationHalftoningDitheringError Diffusion

  • Plotter

    Dot Matrix Printer

    ElectroMagnet

    pin motion

    ink covered tape

    paper

    Older Printing Devices

  • Ink Jet Printer

    paper

    unused inkreturned to

    reservoir

    filterink supply

    drop generator

    chargeelectrode

    high voltagedeflection plates

    ink drops

  • View of the nozzles in athermal bubble inkjet.

    (some 300-600 nozzles per head)

    Thermal-Bubble Ink Jet Printer

    Initial Statewith fluid at

    rest.

    Resistor is heated and

    bubblenucleates.

    Bubble growsto maximum

    ink drop is ejected.

    Bubble collapses.

    Drop breaks off.

    Vacuum createdby bubble sucks

    ink fromcartridge.

    (Canon,Hewlett Packard)

    Demo: http://www.howstuffworks.com/inkjet-printer3.htm

  • Piezoelectric Inkjet(Epson)

    Piezo crystals are located at the back of the ink reservoir of each nozzle. The crystal receives a tiny electric charge that causes it to vibrate. When the crystal vibrates inward, it forces a tiny amount of ink out of the nozzle. When it vibrates out, it pulls some more ink into the reservoir to replace the ink sprayed out.

    Demo: http://www.howstuffworks.com/inkjet-printer3.htm

  • DetachCorona

    wire

    Laser Printer

    ChargeCorona

    wire

    TransferCorona

    wire

    Charge corona wire gives drum initial positive charge. Laser "draws" the image to be printed as a pattern of electrical

    charges -- an electrostatic image. Image is negatively charged. Positively charged toner clings to drum. Toner is deposited on paper (via Transfer wire = charged roller). Paper is discharged (via Detach wire) Toner is fused into paper with heated fuser.

  • Dot Pattern of Ink Jet and Laser

    Ink Printing Laser Printing

    Liquid ink drops are shot onto paper

    Solid particles are attracted to specific

    points on paper.

  • Color Laser Printer

    4 x toner and developer mechanisms.Drum rotates x4 for a single print.

  • Dye Sublimation Printer

    color plastic roll

    paper

    thermal elements

    paper

    plastic inkthermal elements

    High quality photo prints

  • Thermal Wax Printer

    paper

    color wax roll

    printer head

  • Resolution Measuresdots per inch and addressability

    Dots per inch (600)

    Addressable (3000)

  • Additive Subtractive

    Lights vs Inks Additive vs subtractive

  • Reflectance Concepts

  • Color Mixtures

  • Subtractive Color System - CMYK

    cyan

    magenta

    yellow

    black

    = removes red

    = removes green

    = removes blue

    = removes all

    Printer Dyes:

    cyan magenta yellow

    B G R B G R B G R

    trans

    mit

    Ideal block dyes:

  • Cyan - controls amount of red in print:

    low C = high R (also high G and B)high C = low R (high G and B)

    R G BR G BR G BHigh density

    cyanMedium density

    cyanLow density

    cyan

    cyan

    B G R

    trans

    mit

    Similarly Magenta - controls amount of greenand Yellow controls amount of blue.

  • yellow

    Multiplicative (Subtractive) Color Systemred = magenta + yellow

    magenta

    B G R

    red

    *

    =

    B G R

    = magenta + yellow= cyan + yellow= magenta + cyan

    redgreenblue

  • Subtractive Colors - Summary

  • Color Separations

    OriginalRGB

    RGB Color Bands

  • Color Separations

    OriginalRGB

    C = 1 - RM = 1 - GY = 1 - B

    CMY Color Bands

  • Color Separations

    OriginalRGB

    C = 1 - RM = 1 - GY = 1 - B

    CMY Color Bands

  • Undercolor Removal

    C + M + Y = K (black)

    Using three inks for black is expensive C+M+Y = dark brown not black Black instead of C+M+Y is crisper with more

    contrast.

    100 50 70

    (gray component replacement)

    =

    50 0 2050

    +

    C M Y C M YK

  • Gray Component Removal

    K(x,y) = min(C(x,y),M(x,y),Y(x,y))

    C M Y

    K

  • CMYK Separations With GCR

  • Spatial Effects: CMY All Blurred

  • Spatial Effects: only K Blurred

  • cyan

    magenta

    yellow

    B G R

    B G R

    B G R

    Ideal block dyes:

    Ideal Block Dyes vs Printer Dyes

    B G R

    B G R

    B G R

    Actual Printer dyes:

  • Problems with Printer Dyes

    red = magenta+yellow:

    green = cyan+yellow:

    blue = magenta+cyan:

    B G R

    B G R

    B G R

  • Example:Reflectance Spectra of Real Inks

    HP printer

    Full density

    Wavelength (nm)400 500 600 700

    Ref

    lect

    ance

    0.1

    0.3

    1

    Magenta at various densities

    Wavelength (nm)500 600 700

    1

    0.1

    0.3

    400

    Ref

    lect

    ance

  • Tone Reproduction Curves

    Black ink level (dv)

    Lum

    inan

    ce (r

    e: w

    hite

    pap

    er)

    Magenta ink level (dv)

    Lum

    inan

    ce (r

    e: w

    hite

    pap

    er)

  • 0 0.2 0.4 0.6 0.80

    0.2

    0.4

    0.6

    0.8

    x

    y

    printerdisplay

    Printer Gamut

    Colors within the Gamut can be printed.

  • Gamut Mapping

    0 0.2 0.4 0.6 0.80

    0.2

    0.4

    0.6

    0.8

    x

    y

    printerdisplay

    How does one print this color?

    This color never needed?

  • Monochrome Printing

    GrayScale

    Threshold

  • Halftoning

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