Dispositivos de Saída Gráfica
Bacharelado de Informática
PUC-Rio
Prof. Rodrigo Toledo
CLASSIFICAÇÃO
• Processamento:
– Vetorial
– Matricial
• Tipo:
– Emissora de luz (ex: monitores...)
– Não emissora de luz (ex: impressoras...)
Matricial x Vetorial
Imagem descrita como
um bitmap.
(entrelaçado ou não)
Imagem descrita como uma
seqüência de comandos.
Obs: Raster-calligraphic (combination of two)
DEFINIÇÕES E
NOMENCLATURAS
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•
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Pixel (Picture Element)
Dot Pitch
Resolução (número de linhas e colunas)
Resolução de cores
Aspect ratio
polegadas
Persistência (olho humano e equipamentos)
Refresh Rate e Frame Rate
Refresh Rate e Frame Rate
• Refresh rate é a taxa de varredura (ou exposição). Em
geral especificada em Hz.
• Frame rate é a quantidade de quadros diferentes
projetados por segundo (ex: cinema trabalha com 24
frames por segundo)
• O olho humano trabalha em uma freqüência
aproximada de 48Hz.
Refresh Rate e Frame Rate
• Projetores antigos de cinema projetavam cada quadro
2 vezes, para se trabalhar na freqüência do olho
humano.
• Projetores modernos de cinema projetam 3 vezes cada
quadro.
• Os televisores na Europa trabalham a 50Hz, enquanto
no Brasil e nos EUA trabalham a 60Hz.
• Por isso, dispositivos que fazem uso da estereoscopia
ativa devem trabalhar em freqüências iguais ou
superiores a 100Hz.
• Cuidado para não confundir com o frame rate para se
ter a sensação de tempo real na resposta de um
comando (geralmente o mínimo é 12 frames por seg.)
PLOTTER
• VETORIAL
• TINTA
Bastante usado na engenharia
IMPRESSORAS
• Matricial
• Jato de Tinta
–K
– CMYK
• Xerox
– pb
– colorida
MONITORES
• LCD (displays de cristal líquido)
• Plasma (gás)
• CRT (tubo de raios catódicos)
LCD Displays
• Liquid Crystal Display
• Organic molecules that remain
in crystalline structure without
external force, but re-aligns
themselves like liquid under
external force
• So LCDs realigns themselves to
EM field and changes their own
polarizations
Passive LCD
• LCD slowly transit between states.
• In scanned displays, with a large number of pixels,
the percentage of the time that LCDs are excited is
very small.
• Crystals spend most of their time in intermediate
states, being neither "On" or "Off".
• These displays are not very sharp and are prone to
ghosting.
Active Matrix LCD
• E field is retained by a capacitor so that
the crystal remains in a constant state.
• Transistor switches are used to transfer
charge into the capacitors during
scanning.
• The capacitors can hold the charge for
significantly longer than the refresh
period
• Crisp display with no shadows.
• More expensive to produce.
Plasma Display
• Basically fluorescent tubes
• High- voltage discharge excites gas mixture (He,
Xe), upon relaxation UV light is emitted, UV light
excites phosphors
•Large view angle
•Large format display
•Less efficient than CRT, more power
•Large pixels: 1mm (0.2 mm for CRT)
•Phosphors depletion
CRT
(tubos de raios catódicos)
• Feixes de elétrons são emitidos contra
camadas de fósforos, que sensibilizadas
emitem radiação eletromagnética na faixa
visível do espectro.
• Mesmo sistema dos televisores.
CRT
(tubos de raios catódicos)
PROJETORES
• CRT
• LCD
• DLP (ou na verdade, DMD)
Projections : The basics
CRT
LCD and DMD
optical path
Screen
Screen
Lens
Light source = CRT
Image source = CRT
250 - 500 lumens
3200 x 2500
 high resolution
 geometry
 mature technology
 flexible positioning
 photo-realistic
Lamp
Light source = Lamp
Image source = LCD
2000 - 12000 lumens
1280 x 1024
 brighter
 maintenance
 alignment
 easy setup
 pixelization

CRT technology
CRT technology
CRTs
Electronics
Lenses
Screen

CRT technology
Different tube size
7 inch
8 inch
9 inch
12 inch
Scheimpflug correction
Projection can’t be done on tilted surface
-> focus problem!
Scheimpflug correction
Required for projection on tilted screens
Raster <->Calligraphic
Raster image 1280*1024 60Hz
Day mode 1280*1024 60Hz
16 ms
Pixel remains onscreen for 10 ns
Point remains onscreen for 1.5 µs
150 times longer !
Calligraphy
Calligraphic Light points
Raster Image
CRT technology
Strengths:
Resolution
(up to 2500x2000)
Good contrast
Easy geometrical
correction / flexibility
Color matching and
uniformity
Digital soft-edge
Unbeatable video and data
image quality
Life time picture tubes
Proven technology
Weaknesses:
Limited brightness up to
500 ANSI Lumen
Needs low ambient lighting
conditions
Setup time
Maintenance
Not portable
LCD - technology
 brighter
 maintenance
 alignment
 easy setup
Screen
Lamp
LCD
Lens
Light source = Lamp
Image source = LCD
LCD Panels
Panel sizes
1.1-1.8 inch (p-Si)
3 inch (a-Si)
6 inch (a-Si)
10 inch (single panel)
LCD pros and cons
+Well-established technology, stable
+Compact, rugged, portable
+“zero delay”
+UXGA resolution available
+Efficient in passive stereo projection (see further)
-Response speed limited by LC material
some smearing in fast moving images
-non-perfect black (contrast ratio 200-300:1, but improving)
-pixellization
Lens
XCube
LCD
R
B
G
Integrator
System
Lamp
Illumination unit
Dichroic Mirror
Projection Unit
LCOS: Liquid Crystal on Silicon
• Essentially:
LCD in front of a reflector
• Available for microdisplays,
projection
• D-ILA is JVC’s trade name
for LCOS
LCOS implementation
• LCD on top of CMOS chip that includes
transistors and has reflective surface
• Aperture ratio is higher than that of LCD
(so less pixel visibility)
• Efficiency comparable to LCD due to nonperfect reflection
• Easy to cool the chip!
LCOS addressing
• Requires complex optics:
side at which chip is illuminated is the
same as where the light needs to be
extracted from!
LCOS integration
Complex structure required!
LCOS pros and cons
+
+
+
+
+
Higher resolutions possible (up to QXGA)
small chip size (1.3” and smaller)
good response speed
good pixellization (smooth image)
higher contrast possible: up to and over 1000:1
reported
+ chips can be cooled to take high power
illumination
- alignment hard due to small chip size & high res
- difficult to integrate
- uniformity? (although seems to be countered now)
DMD: another reflective tech
Does not require polarized light!
Ant leg on DMD chip
DMD microstructure
Only allows on/off modulation!
DMD: grayscale synthesis
Frame delay!
•1 frame for de-interlacing
•1 for sending data through CMOS chip
•0-1 frame (depending on gray scale) for gray synthesis
3-chip DMD integration
Each chip runs at 10 bits depth, 60 Hz
NOTE: 10 bit Linear Gamma equals
8 bit LCD Gamma
3-chip DMD pros & cons
+Excellent picture quality (pixels almost invisible)
+can take high power illumination
+long life (?)
+no smearing (but
+good intensity uniformity, good color matching
+good contrast (400:1)
-Expen$ive!
-BIG!
-PWM artifacts
-TI monopoly
-Frame delay
-Resolution limited to SXGA
-Bright edge around chip makes optical blending difficult
Single-chip DMD
•Sequential illumination of single DMD chip
•3 or 4 segment color wheel
•chip runs at 8 bit, 240 Hz
less bit depth!
+Compact
-Moving part inside, requires synchronization
-Motion artifacts (color breakup) due to color wheel
OUTROS (DUET)
What is it?
IG
DUET
Active stereo
@ 96 - 120 Hz
Dual passive stereo
SIM 6, 48-60 Hz
OUTROS (Soft Edge)
Soft Edge:
• ESEM: Electonic Soft Edge Modulation
• OSEM: Optical Soft Edge Modulation
LEFT CHANNEL
CENTER CHANNEL
RIGHT CHANNEL