ID C10C: Flat Panel Display Basics

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1 ID C10C: Flat Panel Display Basics Renesas Electronics America Inc. Robert Dunhouse, Display BU Engineering Manager 12 October 2010 Revision 1.1

Robert F. Dunhouse, Jr. Displays Applications Engineering Manager Application Engineering support for North America Electrical & mechanical consultation. Customer equipment debugging.

2 Robert F. Dunhouse, Jr. Displays Applications Engineering Manager Application Engineering support for North America Electrical & mechanical consultation. Customer equipment debugging. Direct communication with NEC LCD Technologies in Japan to resolve technical issues and advise direction for future designs. Design demonstration computers and display housings for field demo program. Includes circuit design & circuit board layout of LCD video interfaces and mechanical design of equipment housings. 14 years engineering experience with NEC LCD Displays. Over 25 years experience in the electronics industry Research & development at Cincinnati Microwave (founders of ESCORT radar detectors) Opened a branch office in Sydney Australia Founded US design and manufacturing company Creative Circuits 2

3 Display Module Solutions Sophisticated solutions Sustainable support Industrial Mobile Displays LED Backlight LCDs Natural Light TFT (NLT) Emerging Technologies Super-Fine TFT (SFT) Wide Format LCDs Robust feature sets Long-term product support Amorphous silicon (A-Si) displays Low-temperature polysilicon (LTPS) displays Low power consumption Long life LEDs Thin profile and light weight design Replaceable LED light source unit Suited for a variety of ambient-light environments Proprietary transflective LCD technologies Super Reflective NLT (SR-NLT) Super Transmissive NLT (ST-NLT) 2D/3D displays Color enhancement E-paper On-cell touch High luminance and wide color gamut Superior image quality Ultra-wide viewing angles More data on a single screen 16:9 aspect ratio 3

Display Module Solutions Sophisticated solutions Sustainable support Industrial Mobile Displays LED Backlight LCDs Natural Light TFT (NLT) Emerging Technologies Super-Fine TFT (SFT) Wide Format LCDs

4 Display Module Solutions Sophisticated solutions Sustainable support Industrial Mobile Displays LED Backlight LCDs Natural Light TFT (NLT) Emerging Technologies Super-Fine TFT (SFT) Wide Format LCDs Emerging Technologies New 2/3 dimensional displays Color enhancement e-paper On-cell Touch Long Term Support/Production Robust feature sets Long-term product support Amorphous silicon (A-Si) displays Low-temperature polysilicon (LTPS) displays Low power consumption Long life LEDs Thin profile and light weight design Replaceable LED light source unit Suited for a variety of ambient-light environments Proprietary transflective LCD technologies Super Reflective NLT (SR-NLT) Super Transmissive NLT (ST-NLT) 2D/3D displays Color enhancement E-paper On-cell touch High luminance and wide color gamut Superior image quality Ultra-wide viewing angles More data on a single screen 16:9 aspect ratio 4

5 Innovation 5

6 Innovation 6

7 Our High Performance Liquid Crystal Displays Renesas has an extensive lineup of Industrial grade Liquid Crystal Displays. Our products are designed with extended shock, vibration & temperature standards, enhanced front of screen performance and long product cycles. We demonstrate industry leading technologies in transflective, high resolution, high color, 3D, e-paper and low power portable displays all to help solve many of today s design challenges. 7

8 Agenda Overview of an LCD display module Liquid Crystal Displays work as light valves Terms, Definitions & Measurements LCD Selection Checklist 8

9 Key Take aways You will be able to speak intelligently about LCD displays You will be able to make informed decisions when selecting a new panel for your project. You will have enough background to attend the follow up session Beyond the Basics to learn about more advanced design considerations. 9

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12 Selecting the Best Display How things have changed! Selecting the right Liquid Crystal Display determines the face of your product and ultimately its success. It is likely the most expensive and influential component so getting it right the first time is a must. This presentation is an entry level exposure to Liquid Crystal Displays (LCDs). It is intended to provide enough information to understand how they work, the common terms used in the industry and demonstrate a method in which to select from the many displays available in today s market. 12

13 Building a TFT LCD Display 13

14 Backlight Light guide Back reflective sheet CCFL or LED Diffusion sheet Backlight assembly frame 14

15 TFT Glass Assembly TFT glass assembly TFT column driver TAB Timing controller board TFT row driver TAB Row board 15

16 Marriage of Assemblies 16

17 A Closer Look at the TFT Glass Assembly Alignment layer Color filter ITO common electrode Outer polarizer Outer Glass Substrate Epoxy sealer Short Bonding pad Alignment layer a-si TFT layer & pixel electrode (ITO) Inner glass substrate Inner polarizer Ball spacer LC material 17

18 How LCD Displays Work as Light Valves 18

19 The Liquid Crystal Cell 19

20 Light Passing Through 20

21 Primary Color TFT Cells 21

22 Common Terms and Definitions 22

23 Size Size = Diagonal measurement of the active video area. 23

24 Resolution Pixels Lines Resolution = Horizontal pixels x Vertical lines Ie. 640 x 480 is 640 pixels by 480 lines or one video frame. Total Thin Film Transistor (sub-pixel) count would be: 640 x 3 x 480 = 921,600 24

25 Contrast Ratio Contrast ratio = White luminance/black luminance Black is not absolute. When measuring, white must be driven. 25

26 Color Filter LCD display color filters are arranged in Red, Green & Blue vertical stripes. 26

27 Pixels & Lines One pixel is made of three sub-pixels. Red, green & blue are the primary colors. Pixel pitch is the distance between any two like color subpixels Rows of pixels make up one line. 27

28 Viewing Angle θl θu θd θr Viewing angle is measured from center perpendicular to where contrast ratio decreases to 10:1. Specmanship happens when comparing viewing angles of >5:1 contrast ratio. 12 O clock viewing is θu and 6 O clock is θd from the panel s perspective. 28

angles Wash out loss of contrast Color inversion

29 TN Viewing Angle Characteristics Standard TN (Twisted Nematic) panels have optimized vertical viewing angles Wash out loss of contrast Color inversion colors darken and invert. Appears like a film negative effect. 29

30 Gray Scale Gray scale is the transition from white to black. Color is superimposed over gray scale to determine all the various shades of that color. LCD displays are typically either 18-bit or 24-bit color. This is defined as the number of color bits for each primary color times three. 24-bit color = 8 bits of Red + 8 of Green + 8 of Blue Total different colors displayed: 2 = 16.7 million 30

Color Gamut The CIE 1931 diagram represents the total colors the human eye can perceive. CIE 1931 Chromaticity Diagram NTSC Standard Red 0.67, 0.33 Green 0.21, 0.71 Blue 0.14, 0.08 White 0.

31 Color Gamut The CIE 1931 diagram represents the total colors the human eye can perceive. CIE 1931 Chromaticity Diagram NTSC Standard Red 0.67, 0.33 Green 0.21, 0.71 Blue 0.14, 0.08 White , The color gamut of an LCD display is stated as a percentage of the National Television Standards Committee (NTSC) standard. In this example the LCD reproduces 40% of the NTSC standard. 31

32 Panel Response White Luminance 100% 90% Black 10% 0% Ton Toff 32

33 Panel Response Notes The lower the number the better Be sure the measurement represents black-to-white-to-black times. Specmanship happens when only showing one way time. Traditional measurement method is white-to-black. In reality rarely is an image switched this way so newer comparisons will specify gray-to-gray switching times. Surprisingly gray-to-gray times can be larger than white-toblack. Response Time Compensation momentarily applies an overvoltage to the TFT cell to quicken crystal alignment. 33

34 Peak Luminance 50cm Photometer 1 degree focal angle Peak luminance is measured with an optical photometer placed 50cm from the center perpendicular front surface of the display. Measurements are taken in dark room conditions. Same test setup is used to measure contrast ratio. 34

35 Luminance Uniformity Luminance uniformity defines how well an LCD maintains even luminance over the total surface of the display. Maximum and minimum luminance measurements are made in 5 locations. Luminance uniformity = Max Luminance (1 to 5) / Min Luminance (1 to 5) 35

36 LCD Selection Checklist 36

37 LCD Selection Checklist Panel size Select a general size based on your preliminary design. Remember to include margin for frame components. Resolution What clarity of image is needed? The higher the resolution the clearer the image appears. Does the manufacturer have an upgrade path? How much information needs to be displayed and once its translated to the video image will it be useable? Do you need normal aspect or wide format? 4:3 is typical, 16:9 is the newer wide format. Color or monochrome? 37

38 LCD Selection Checklist What format is your video source? Analog RGB Parallel digital CMOS LVDS single, dual or four channel Composite or S-Video DVI Digital Visual Interface HDMI High Definition Multimedia Interface Does the video format match the display? Yes video source and panel are compatible No A video interface will needed to convert the video source format to one compatible with the panel. 38

39 LCD Selection Checklist What type of backlight? LED or CCFL? Most new products have transitioned to LED LEDs may still have a slight initial cost disadvantage Reduction of Hazardous Substances (RoHS) has driven the change to LED LEDs are now more energy efficient, have longer lifetimes and are more mechanically robust. 39

40 LCD Selection Checklist Does the LCD module include a backlight driver? CCFLs use high voltage AC inverters. Safety concerns for medical applications Switching noise considerations LEDs uses constant current drivers. Typical LED string forward voltage is below 40VDC EMI low Both are approximately the same in cost. LED driver board footprints can be small. 40

41 LCD Selection Checklist Power Newer generation LED backlit panels are generally lower power. For maximum power savings consider a reflective technology LCD. These panels enable the user to turn off the backlight in higher ambient lighting. The new e-paper displays only consume power when writing a new image. Once the image is written ALL power can be removed. Certain premium viewing angle technologies consume more logic power. 41

42 LCD Selection Checklist What environment will the panel be used in? Indoor or outdoor Temperature Moisture Direct sunlight exposure Solar thermal loading Preservation of contrast Vandal proof Shock & vibration requirements? Industrial rated panels have higher shock, vibration & temperature parameters. Industrial panels tend to be mechanically larger than commercial panels. Frames are more robust and backlights brighter. 42

43 LCD Selection Checklist Bottom line is the best test is your eyes. Schedule a side-by-side comparison of several panels that look good on paper. The Renesas Display Business Unit has an easy to use demo system. 43

44 Action Obtain several LCD datasheets for comparison purposes. Attend the follow up session ID C22C: Flat Panel Displays Beyond the Basics to learn more advanced design and integration considerations. The session is in room Royal E&F at 5:15-6:15PM. 44

45 Innovation 45

46 Questions? 46

47 Thank You 47

48 Renesas Electronics America Inc.

Flat Panel Displays: LCD Technologies and Trends

Flat Panel Displays: LCD Technologies and Trends Robert Dunhouse, Sr. Engineering Manager, Display BU Class ID: 4C01B Renesas Electronics America Inc. Robert F. Dunhouse, Jr. Sr. Engineering Manager, Display