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Display hardware Cathode Ray Tube • vector displays • Main applications – 1963 – modified oscilloscope – 1974 – Evans and Sutherland Picture System – Oscilloscope • raster displays – TV – 1975 – Evans and Sutherland frame buffer – Old monitors – 1980s – cheap frame buffers bit-mapped PCs – 1990s – liquid-crystal displays laptops – 2000s – micro-mirror projectors digital cinema – 2010s – high dynamic range displays? • other – stereo, head-mounted displays – autostereoscopic displays 1 2 1 CRT Electrostatic Deflection • Electron Gun creates an electron beam with controllable intensity. • The deflection system moves the electron beam vertically and horizontally. • When the electron beam strikes the phosphor, it produces visible light on the fluorescent screen. • Only one point is lighted. Electron gun Light beam • Small deflections Deflection system • Used in Osciloscopes 3 4 2 Magnetic Deflection Deflection Signals Hd t Vd t • Greater deflections • Used in TVs 5 6 3 Vector Displays or random scan display Vector Displays – The electron beam is directed only to the parts of the screen where a picture is to be drawn. – Like plotters it draws a picture one line at a time – Used in line drawing and wireframe displays – Picture is stored as a set of line-drawing commands stored in a refresh display file. – Refresh rate depends on number of lines – Typicaly: • Refresh cycle is 30 to 60 times each second • 100 000 short lines at this refresh rate 7 8 4 Vector Display Vector Displays Advantages . Generates higher resolution than other (Raster) systems . Produces smooth line drawings Disadvantage . Not usable for realistic shaded scenes 9 10 5 Raster Scan Frame / Line Rate Frame Rate: 1 Frames / sec. TH = Horizontal Scanning Period FR Quadros / seg. Hz TV TV = Vertical Scanning Period Line Rate: H Hd sinc H 1 Lines / sec. LR FR NL Linhas / seg. T Hz L H H V V Nº de linhas de um quadro: d … sinc V d T 1 NL V TH t TH FR TH Nº de linhas visíveis: Vd NL NL' t TV 11 12 6 Color CRT Shadow Masks 13 14 7 Monitor Example 40VM9H 9” B&W Monitor Screen Size 8.74” Diagonal Resolution >1000 TVL Horizontal 15,750Hz / Vertical 60Hz (EIA) Scanning Frequency Horizontal 15,625Hz / Vertical 50Hz (CCIR) Composite 1Vp-p 75 Ohm loop through BNC via Video Input impedance switch Video Output Composite 1Vp-p CVBS 75 ohms Power Source 90V ~ 120VAC (60/50Hz) Power Consumption <25W (EIA/CCIR) Environmental Operating Temperature 10°C ~ +40°C (14°F ~ 105°F) Operating Humidity 30% ~ 80% (no condensation) Mechanical 222.25mm x 215.9mm x 254mm Dimensions (H x W x D) (8.75” x 85” x 10”) Weight 6.8 kg (15 lbs) Safety Standards UL, LVD, CE, RoHS 15 16 8 Monitor example Monitor Example 5” CRT Monitor 01 Professional Large LCD Monitor SPECIFICATION Model SMT-3222 SMT4022 Standard: CCIR 625 Line 50Hz and RS 170 60Hz interlaced. General Screen Size 32" 40" Aspect ratio: Switchable between 4:3 and 4:1.77 Resolution (HxV) 1366 x 768 1920 x 1080 Pixel Pitch (mm) 0.511 x 0.511 (HxV) 0.46125 x 0.46125 (HxV) Video impedance: 75 ohms ±2%. Brightness(cd/m2) 450 Contrast Ratio 4,000:1 (Dynamic Contrast Ratio 40,000:1) Input type: Differential Response Time (ms) 8 (G-to-G) Grey levels: 16 at 100 cd/m2 Viewing Angle (H/V) 178° / 178° Panel Lamp Life 50,000HR Video bandwidth: >12MHz -3dB Display Colors 16.7M Horizontal Frequency 30 ~ 81KHz Gain control: Contrast control on front panel Vertical Frequency 56 ~ 85Hz Black level control: Brightness control on front panel Horizontal Resolution 600TV Lines Comb Filter 3D Warm up time: 15 seconds after power Sync Format NTSC : 3.5 / PAL : 4.43 / Secam Feature Power requirements: 28V to MIL-STD-1275B Screen Aspect Ratio 4:3 / 16:9 English / French / German / Italian / Portuguese / Russian / Spanish / Power consumption total: <20 watts (at 450cd/m2) Language Swedish / Chinese / Japanese / Korean / Turkish / Taiwanese June 2006 17 18 9 Raster CRT Graphics Card 1 RD D0 R • Raster CRT pros: DAC D3 RAM D4 G – Allows solids, not just wire frames A DAC 15 D A 7 – Low-cost technology (i.e., TVs) 8 D8 B DAC D11 – Bright! Display emits light A70 -A • Cons: DotCLK – Requires screen-size memory array Counter Counter Osc – Discrete sampling (pixels) Hsinc – Practical limit on size Vsinc 19 20 10 Graphics Card Color Map DACs’ resolution Exemple: 4 bits => Nr. of colors = 2(3*4) = 4096 visible colors Memory M = NC * NL * PS Exemple: 256 columns * 256 lines * 12 bits/pixel = 768 kbits = 96 kBytes DotCLK DotCLK = FR * NL’ * NC = LR * NC Exemple: 60 frames/second* 256 lines/frame * 256 pixels/line = 4 MHz 21 22 11 Color Table Page RAM 8192 x 1024 x 8 x 13 x 13 Address A0 - A12 x 10 bits/pixel Nr of simulataneous colors = 2 x 10 Exemple: 8 bits/pixel => 28 = 256 visible colores 23 24 12 VRAM IBM 4MB 3D-RAM 25 26 13 Graphic Computer Dual Buffer + Z 27 28 14 RGB CMY Models • Used in electrostatic and ink-jet plotters that deposit pigment on paper G • Cyan, magenta, and yellow are complements of red, green, and blue, respectively C 1 R • White (0, 0, 0), black (1, 1, 1) M 1 G R Y 1 B CMYK Model: K (black) is used as a primary color to save ink Green Yellow (minus blue) B deposited on paper => dry quicker (minus red) - popularly used by printing press Cyan Black Red Blue Magenta (minus green) 29 30 15 YUV Y’UV Y – luma, brightness, luminance Y’ – gamma corrected Y U, V – chrominance Ideia: Y = R + G + B -> monochromatic image U = Y-B V = Y-R R = Y-V B = Y-U G = Y-R-B Advantages: • A monochromatic receptor can use only the Y channel • Resolution for U and V channels can be reduced …. Variations: Y’UV, YCbCr, YPbPr 31 32 16 HSL Interactive Specification of Color • Many application programs allow the user to specify colors of areas, lines, HSL - Hue, Saturation, Lightness L text, and so on. branco H – Hue: Cor percebida por humanos • Interactive selection: S – Saturation: 100%=cor pura 0%=level of gray vermelho L – Lightness: 100%=white S H 0%=black azul verde preto • Perception of color is affected by surrounding colors and the sizes of colored areas 33 34 17 Analogue Television Interlaced lines • How much bandwidth would we need for uncompressed digital television? • European TV format has 625 scan lines, 25 interlaced frames per second, 4:3 aspect ratio • It uses interlacing to reduce the vertical resolution to 312.5 lines • Horizontal resolution is 312.5*(4/3) = 417 columns • Bandwidth required 625*417*25 = 6.5MHz • Analogue colour information was quite cleverly added without increasing bandwidth (NTSC, PAL and SECAM standards) http://www.answers.com/topic/interlace?cat=technology http://en.wikipedia.org/wiki/PAL 35 36 18 Composite Video Composite Video Monitor H Hd Video Video sinc H Video Hsync Source encoder Composite decoder L video L Vsync V V sinc V d http://en.wikipedia.org/wiki/Composite_video 37 38 19 Composite Video Color TV http://en.wikipedia.org/wiki/Pal 39 40 20 Composite Video CVBS Color, Video, Blanking, Sync Source Monitor Video Video Hsync Hsync encoder Composite decoder Vsync video Vsync R Y Y R RGB YUV G U U G to to V B B YUV V RGB 41 42 21 PAL PAL http://en.wikipedia.org/wiki/DVB-T 43 44 22 SECAM - Sequential Couleur Avec Memoire HSync On Green • France, 1 October 1967 • developed in France (predominantly a political decision). • used in France and territories, C.I.S., much of Eastern Europe, the Middle East and northern Africa. • Line Frequency - 15.625 kHz • Scanning Lines – 625 (same as PAL) • Field Frequency - 50 Hz • Color Signal Modulation System FM Conversion System • Color Signal Frequency - 4.40625 MHz/4.250 MHz • Burst Signal Phase settled • Video bandwidth - B,G,H: 5.0 MHz; D,K,K1,L: 6.0 MHz • Sound Carrier - B,G,H: 5.5 MHz; D,K,K1,L: 6.5 MHz 45 46 23 Sync On Green Resolutions http://en.wikipedia.org/wiki/Display_resolution 47 48 24 Flat Panel Displays Liquid Crystal Displays (LCDs) Volatile • Pixels are periodically refreshed to retain their state • LCDs: organic molecules, naturally in crystalline • Refresh many times a second state, that liquefy when excited by heat or E field • Otherwise image will fade from the screen • Crystalline state twists polarized light 90º. • Plasma, LCD, OLED, LED, ELD, SED and FED-displays Static • Material with bistable color states • No energy needed to maintain image, only to change it. • Slow refresh state • Deployment in limited applications • Cholesteric displays, outdoor advertising, e-book products 49 50 25 Liquid Crystal Displays (LCDs) Color Filters (RGB) Conventional color displays use a specific sub-pixel arrangement. • at high pixel densities, RGB or RGB Delta arrangement is adequate. • when the number of pixels is limited, the GRGB arrangement can be used. 51 52 26 Passive Matrix LCD Problems Thin Film Transistor • Pixel is ON only during scan access. TFT (Thin film transistor): a special kind of FET • More Rows => shorter on-voltage time • Reduced bright, • poor contrast ratio, Basic FET • narrow viewing angle, • fewer gray levels. • Higher voltages => more crosstalk between neighbor pixels • Scan frequency is limited by LC response delay. MISFET • Flicker Solution • placing an active element at each pixel • switch and memory TFT • transistor and capacitor http://www.wikipedia.org 53 54 27 TFT Active Matrix TFT Active Matrix 55 56 28 Display Technology: LCDs CCFL Backlight • LCDs act as light valves, not light emitters, and Cold-Cathode Fluorescent Lamp thus rely on an external light source.
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