Driving and Technologies. of Electronic Displays

Transcription

1 Driving and Technologies of Electronic Displays Karlheinz Blankenbach University of Applied ciences Pforzheim Department of Electronics, Pforzheim, Germany 1 Table of Contents Basics of Driving Driving Parameters Display Technologies 2

2 Display Driving : Raster can CRT, Laser election and luminance (data) for each pixel by a moving and intensity modulated beam (electron, laser) ingle data at one time erial data : Pixel-at-a-time addressing Deflection frequencies can be changed easily (analogue amplifier) Number of pixels changes automatically with input signal Large depth (disadvantage) A single pixel is only activated for a short time - Flicker - No smearing 3 Raster can

3 Display Driving : Matrix Drive widely used for Flat Panel Displays - canning of rows - Write data to columns - elect one row - Write data of all columns at one time Parallel data : Row-at-a-time addressing Fixed resolution! Column (data) Data from µc, PC,.. Controller Row (line, scan) Display 5 Matrix Driving of FPD - Example LCD Exception PDP Passive Matrix Higher contrast, higher resolution, more grey shades and colours Active Matrix Driving voltage + U Row 'scan' 0 ITO 1 Pixel 0 - U ITO U 0 Column 'data' 2U U (PM LCD simplified example) Ghosting Pixel voltage Data AM LCD (ub-)pixel can MOFET LC torage capacitor Frontplane - Crossings of 2 grids form pixel - No storage of data (if not bi-stable) during frame period - Capacitor stores data during frame period - 1 TFT pp, XGA : 4 Mio. TFTs 6

4 Matrix Drive Basics Passive Matrix napshot of 1 selected row, example for LCDs Active Matrix Leftover from actual scan Data tored from actual scan Data can can Moving image? Leftover from last scan (frame)! tored from last scan (frame)! 7 Raster can vs. Matrix Drive : ignals Raster can : erial Data Matrix Drive : Parallel Data 1 Line (serial) Column 2 Data (video) Pixel Data Column 1 1 Line (parallel) H-ync Row 1 V-ync Row (selected line) 1 Frame 1 Frame t t 8

5 Driving - Luminance - Display Technology Driving (V, I) Luminance L mean Rise effects Activation of pixel AMxxx, bi-stable PM LCD, CRT PM OLED, Laser,... T ON T Frame t t T ON is short for high res displays compared to T frame Flicker can occur Example : XGA CRT pixel is only activated for 10-6 of the frame time AMxxx and bi-stable technologies can be driven with low peak luminance Human eye detects mean value of luminance (L mean ) High peak luminance for fast decay technologies required (PM OLED, laser, phosphor) 9 Driving Parameters Horizontal scan Displays are usually scanned from top to bottom (and left to right for raster scan) Vertical scan Frame rate (frequency) = 1 / time for vertical scan f frame = 1 / T frame Duration of vertical scan = number of lines x time for one line T frame = N x T line (add for 5 % for FPD synchronisation, 20 % for CRT retrace) Horizontal frequ. = 1 / time for one line (incl. sync & retrace) f hor = 1 / T line Driving is limited for - analogue displays by video bandwidth - digital panels by transmission line capability 10

6 How Fast is the Electron Beam of CRT Monitors? Example - 17" (viewable 32 cm) - XGA (1280 x 1024) - Frame frequency 100 Hz 1 frame 10 ms - 10 % retrace 1 line 9 µs v = s/t = 30 cm / 9 µs km/h Each subpixel is activated for 9 µs / ns Retrace for analogue video in CRT-systems needs % of horizontal duration (e.g. CCIR TV : T line = 64 µs, T write = 52 µs) - < 10 % of frame duration (e.g. # write = 576, # frame = 625) 11 Limitation of Image Quality for Analogue ignals peed of CRT beam (s. a.) requires high bandwidth of the video signal amplification ( V). If the bandwidth is to low the sharpness of the picture is reduced - strongly for pixel ON - OFF - ON. This is also relevant for analogue input FPDs. Pixel frequency = pixel clock = # of lines x f frame Note : pixel clock = maximum 'information', so video system has to be capable of driving (see MTF) 12

7 Limitation of Image Quality for Analogue ignals Hands on formula : Recom. video bandwidth > 2 x horizontal resolution x horizontal frequency Note : also applicable to FPDs with analogue input! Example - XGA : 2 x 1024 x 67 khz = 135 MHz (see specs of PC monitors) - TV : 2 x 768 x 15 khz = 23 MHz but limited to 5 MHz (transmission limited) 13 Analogue ignals : Composite Video (CCIR, R-170, FBA) Composite signal which is compatible to monochrome video signals Brightness and color in one signal Abbreviation FBA : F - Farbsignal (color signal) B - Bildsignal (brightness in proportion to voltage: 100% white, 30% black) A - Austastsignal (blanking during horizontal and vertical flyback) - ynchronisation 1 signal : luminance & color (burst) 14

8 Composite Video : Voltage Levels : Video ignal levels are critical : A lower white level (< V) leads to too dark images Higher levels (> V) wash out the higher gray shades Different combinations of graphics adapter and monitor can show various effects (see Display Metrology LCD monitor test!). 15 Analogue ignals : - Video Transmits luminance ("Y", see color) and chroma ("C", color) ignal level and timing like CCIR, 1 line for timing and brightness, 2 nd line for color Better image quality than Composite-Video Also called 'Y/C Brightness Color (no color burst) 16

9 Analogue ignals : RGB Each color and synchronisation is transmitted separately (R G B H V) Image quality is significantly higher than -Video Used in PCs for analogue monitors like CRTs. R G B + ync (H, V) ignal level such as CCIR Σ 5 lines 17 Analogue ignals : YUV The information is split into 3 signals such as RGB & sync (5 lines) YUV is defined as - Luminance ( Y as sum of 59% green, 20% red and 11% blue) - 2 color difference signals (Blue minus Y { U } and Red minus Y { V }) Video signal on DVDs is stored as YUV no loss in image quality Y V U 18

10 PC tuff Norm Resolution / Pixel Number of Pixels Number of Color ub-pixels / Millions More Pixel as VGA More Pixel as VGA VGA 640 x , VGA 800 x , % - XGA 1024 x , % 60 % XGA 1280 x ,310, % 173 % UXGA 1600 x ,048, % 327 % Aspect ratio: 4:3; WxGA: 16:10 Remark The number of pixels published for digital cameras are a total one, e.g. 2.3 Millions. For monitors the number of RGB pixels is defined, in this case Millions, resulting in 2.3 Millions of ub-pixel. The real resolution of cameras is about half of the number of (sub) pixels due to dedicated interpolation algorithms. 19 TV tuff D TV (4:3 aspect ratio) tandard TV : 576 lines, interlaced mode HDTV (16:9 aspect ratio) - HD ready : 720 lines, progressive mode - Full HD : 1080 lines, interlaced mode Remarks - The number of horizontal pixels is not defined but can be calculated via aspect ratio: D: 568 x 576, HD ready: 1280 x 720 (often 1366 x 768), Full HD: 1920 x Interlaced means that an image is transmitted in two subframes (odd, even lines) This keeps the data rate low, but this is optimized for CRTs. FPDs have to use de-interlacers. 20

11 Graphics Adapter & Interface Digital Flat Panel PC IA PCI AGP Graphics Adapter Analog CRT CRT Flat Panel - Most of today s PC adapters have analogue output - Laptop display is driven digitally - Flat panels with analogue input have lower image quality 21 Resolution vs. Pixel Rate Resolution / 10 6 Pixel 5 2 FPD 60 Hz 1600 x 1200 (UXGA) CRT 75 Hz x 768 (XGA) 640 x 480 (VGA) Pixel Rate /MHz Pixel rate = Resolution x frame rate Data rate = Resolution x frame rate x RGB x colour depth 22

12 Analog Interfacing FPDs to PC + Compatible with standard graphics adapters, CRT replacement - Loss of image quality (DAC-ADC) - FRC is necessary, scaling required for displaying various resolutions (s. b.) 23 Analog VGA Connector RGB signal eparate H/V sync tandard cable length ~ 2 m Widespread 24

13 Analogue Input must be Converted to Digital Data For optimum results, ADC has to be adjusted Use 1x1 vertical and horizontal grille 25 Digital Interfacing of FPDs to PC + uperb image quality - no DAC - ADC needed + Lower costs if standard - PCs often used, laptops seldom (2007) 26

14 Digital Transmission tandards Digital RGB (FPD, parallel) + No DAC - ADC needed + High quality - Limited length of cable - 1 Line per Bit - * 3 for color - ync signals Panel Differential ignal - LVD, TMD (DVI), GVIF - Panel same as for Digital RGB + Large cable length Panel - Costs for transmitterreceiver 27 erial Interfacing : LVD, TMD & GVIF Reduction of lines by using twisted pair (serial data) mall and thin cable (a must for laptops) L and H are defined as voltage difference instead of voltage level low sensitivity to EMI LVD is also used for digital image processing cameras Avoid static voltage generation by large numbers of L' or H' Bit inversion 28

15 Low Voltage Differential ignalling Transition Minimised Differential ignalling Multiplexing of 7 signals (7 Bit) on 1 line Both use voltage difference (~ 0.1 V) TMD has current loop (disadvantage for EMI) LVD by NATIONAL EMICONDUCTOR and TEXA INTRUMENT mainly used in laptops and for digital image processing TMD by ILICON IMAGE, also named as PANEL-LINK and Digital Video Interface (DVI) 29 Block Diagram LVD & TMD LVD : 4 data pairs TMD : 3 data pairs 30

16 Bandwidth of PANEL-Link (TMD) GTF (VEA) : Generalised Timing Formula 31 TMD Connectors Digital Flat Panel Digital Video Interface Only digital Digital & analogue 32

17 High Definition Multimedia Interface Focus: Consumer electronics like TV sets, DVD players etc. Different version, latest (2007): supports xvycc (Extended YCC Colorimetry for Video Applications) gamut larger than NTC or PAL DVI (video) + audio With Digital Rights Management: High-bandwidth Digital Content Protection 19 pins (3 data pairs, 1 clock pair, I²C, shields, ground, power, ) Cable length up to ~ 12 m maller than DVI 33 High Definition Television Format Horizontal Resolution Vertical Lines Pixel Aspect Ratio Image Formation Frames per ec. 1080p Mio. 16:9 Progressive 24, 25, i Mio. 16:9 Interlaced 30, 50, p Mio. 16:9 Progressive 24, 25, 30, 60 Only the vertical resolution is defined! 1080 = FullHD, 720 = HD ready PAL has about 0.4 Mio. pixels 24 frames per second = movie mode 25 & 50 Hz ensure PAL compatibility, 60 Hz NTC Panel runs with fixed frequency! D TV has 4:3 PDPs run D with full image because of burn in 34

18 HDTV Equipment ource Transmission TV et TV station atellite HDTV et Top box HDTV hard disc HDTV player (Blue ray or HD DVD) HDMI with HDCP HD TV set - 17 HDTV standard formats are defined - Most relevant: MPEG 4 (MPEG 2), H.264/AVC und DVB-2 35 Comparison DTV vs. HDTV PAL HDTV 36

19 Comparison of Digital Interfaces Introduced 2007 LVD DVI HDMI Unified Display Interface Display Port Analogue support None Optional None None None Laptop support Yes None None Yes Yes No. of pairs 10 4 or 7 4 or 7 4 or 7 1 (1920x1080) to 4 Content protection None HDCP HDCP HDCP DPCP with Advanced Encryption tandard Protocol tream tream tream tream Packet Mobile Display Digital Interface: packet based, 1-8 pairs for display, camera, 37 Typical Flat Panel ignal Processing Design & ystem LCD dedicated back-end unit DAC Analogue display Analogue & digital inputs Universal Front-end processing unit PDP dedicated back-end unit Digital display + DLP dedicated back-end unit Digital display 38

20 LCD History LCD TV 39 LCD TV Race (Prototypes) 2004 : : 82 Commodity up to 65 (2007) 2006 : 100 Gen 9+? 40

21 pecial AM LCDs 9.5 WVGA Harsh environment : Aircraft (PHILIP), automotive (HARP) 41 High Resolution Displays 5 MPixel Only LCDs Applications : Medical, CAD, imulation, PLANAR 21 5 MPixel 42

22 ME/I Active - Matrix - Driving Typical Pixel hape can Data MOFET LC torage capacitor Frontplane - can and data signal on one plate - 1 pixel = 3 RGB subpixel - 1 TFT per pixel (AM OLED 2) - Aperture ratio 60% - Capacitor stores pixel voltage - XGA : 1280 * 1024 * 3 TFTs (data) during frame time 4 Mio. TFTs ME/I 43 Active Matrix Cell 44

23 AMLCD Module 45 Improvement of Viewing Angle (II) TN IP VA, OCB Low driving voltage Narrow viewing angle Very wide viewing angle low response speed Low brightness High contrast ratio Wide viewing angle Fast response speed Viewing angle value without minimum C R or E is useless! 46

24 LCD Mother Glass & Costs Price $/m² Gen 3 Gen Gen 6 Gen 7 Gen 5 : 12 x 17" (87%) ; 6 x 24" (78%) Gen 6 : 8 x 32" (84%) ; 6 x 37" (86%) 50 Gen Gen 7 : 8 x 40" (91%) ; 6 x 46" (90%) 2 x 82" 47 LCD : Merits & hortcomings ize from 1 82 Pixel pitch mm Resolution 128 x 64 Quad HD Lifetime up to 100,000 h Mature Mass production till innovations Viewing angle dependency Response time Image sticking for large panels for e-signage unlight readability for transmissive LCDs 48

25 Organic LEDs ummarises mall Molecules (OLED) & Light Emitting Polymers (LEP, PLED) High luminance (up to 30,000 cd/m² for direct drive) Low driving voltage (~ 5 V), high switching speed (necessary for PM) High efficiency (~10 lm/w, compare to bulb 20 lm/w, CRT 1 lm/w) 49 Organic LEDs O N N Al O O N R 1 Kodak First display application n R 1 Cambridge DT LEP M M : Alq3 Polymer (PPV) Industrialization Prototype Discovery of Anthracen First product (M) Product : 2 M 50

26 Prototypes of AM OLEDs mall Molecules Polymer ONY 13.3 TOHIBA 17 ony 24 4 x tiled PHILIP OLED : Merits & hortcomings ize from 1 5 Pixel pitch mm Resolution 128 x 64 QVGA (commercial 2007) No viewing angle dependency Fast response time Thinner than LCDs Limited lifetime (about 10,000 h) Burn in Immature technology (2007) Only a few makers with mass production (2008) unlight readability for transmissive LCDs 52

27 Plasma Display Panels All- digital driving! First FPD-technology with screen size > 40 Light generation by plasma (compare to fluorescent lamp) Passive Matrix drive, AC memory type widely used 103 Panasonic for 100,000 $ (2006) 53 PDP Light Generation Principle Uses mix of rare gases (Xenon, Neon and Helium), Plasma is the state of the gas V AC discharge in cell stimulates ultraviolet (UV) radiation UV stimulation causes color phosphors to glow and form picture elements Each cell only has a binary state (ON or OFF) 54

28 ME/I All-Digital Technologies : ub - Frame Integration Original Tim e ub-frame As seen by vision 55 ME/I PDP : Merits & hortcomings ize > 37 Resolution WVGA HDTV No viewing angle dependency Fast response time Cheaper than LCDs for large size (2007) Mature technology Limited lifetime (about 20,000 h) Burn in Limited living room capability (recommended for home cinema) Limited white luminance Pixel size > 1 mm 56

29 Projection : Digital Mirror Device Reflective technology with toggling mirrors Each (micro) mirror corresponds to a pixel All-digital driving (Digital Light Processing) Patent : TEXA INTRUMENT All-digital driving! 16 µm 57 DMD Projector Principle 58

30 1 - Chip - DMD Projector Color generated by rotating a color wheel (60 U/s) 5.5 ms per primary 22 µs for LB (8 Bit gray scale) Convergence adjustment not necessary Note : 3 panel DMD needs no color wheel but filters 59 DMD Projector ystems Three Chip One Chip (Non-telecentric, offset) DMD Projection Lens Efficient Lowest cost Auto convergence Relay lenses ystem Aperture Color Wheel Relay Mirror Compact, lightweight Condenser Lens Arc Lamp Highest image quality Highest efficiency Higher cost 60

31 Electronic Paper Idea : Replacement of paper (books, price tags, billboards,...) Advantage : 'Re-write' within seconds Bi-stable and reflective Lowest power consumption mall pixel size High resolution ( dpi) Flexible possible Requires plastics and organic electronics 61 Electronic Paper - Paper Like Displays (PLD) Paper Display (ystem) Merits - Bi-stable - Thin & light - Flexible - Design free - Readability - Low cost - Ease of use + - Rewritable - Re-use - Portable - torage - Data access - Moving images hortcomings - Re-use - Data access - tatic content - Bi-stable - High cost - Rigid & heavy - Reflective - High resolution - Plastic for flexible 62

32 Electronic Paper in Comparison with other Displays Thickness : ~1 mm with glass, ~0.3 mm all-plastic (add bezel, electronics,... ; paper ~ 0.1 mm) Reflective technologies Reflection for white Contrast ratio B/W TN LCD (PDA) with touchscreen : 1 E-INK with touchscreen : 1 Newspaper : 1 Power consumption 5" QVGA 8" VGA Transmissive color - AM LCD 1,000 mw 4,000 mw Reflective Color - AM LCD 25 mw 600 mw Monochrome E-Paper with update every 10 s 1 mw 10 mw Monochrome E-Paper with update every minute 0.15 mw 1 mw ~1000 h with AA battery! 63 Candidates for Electronic - Paper Displays All suitable for Direct Drive, PM & AM (for high resolution) Electrophoretic Rotating ball - Wet-type E-INK, IPIX, HP, - Dry-type XEROX, BRIDGETONE, GYRICON, OJI-PAPER, (Cholesteric) LCD HARP, KENT, FUJITU, ZBD, NEMOPTIC, Electrochromic Membrane Electrowetting NTERA, QUALCOMM, LIQUAVITA, ADT Too many technologies? Only E-INK in MP (2006) No flexible MP (2006) 64

33 Electrophoretic Wet - Type PLDs : E - INK Principle: Microcapsules with black and white, opposite charged particles Bi-stable & high reflectivity Light tate Dark tate + Electrode Electrode Response time ~ 150 ms Most advanced Operating temperature range : C technology Driving voltage ~ 10 V Power consumption h with AAA 10 s update) 65 Examples of E-INK Products Reflectivity 25%, C R 10 : 1 E-Ink, ID

34 What means Flexible? Conformal Bendable Rollable also that or foldable? 67 Flexible Displays for Innovative Devices Today s Prototypes Vision 68

35 Flexible Displays for R2R - Production Example of roll-to-roll manufacturing equipment (Rib developing system) QR - LPD Metal electrode PET base back plane manufactured by roll-to-roll process 69 ummary E-Paper E-paper would / will revolutionise mobile computing Many candidates for e-paper today (will shrink as in every new techn.) Flexibility will give (bi-stable) displays break-through applications Flexible technology enables roll-to-roll manufacturing Flexible & bi-stable displays are NBT However: Hires requires AM on flexible substrates - will this become feasible? 70

36 ummary Displays First step is to decide what has to be displayed incl. viewing distance Determine optical performance in terms of ambient light capability, MTF, viewing angle, response time, Choose the display technology to fulfil the requirements Think also in terms of maintenance, mature technology, Be always aware that a display is - the first impression of a customer - often the most expensive component 71