display technologies by kasai

DISPLAY TECHNOLOGIES

A presentation by:

• Zuwayr Wajid• Abdullah Jehangir Yousaf• Muhammad Yaar• Anaan Javed Ramay

CONTENTS• Pixel• Colour Depth• Resolution• List of Common Resolutions • History• CRT• Video Projector

CONTENTS• LCD• TFT• TN• IPS• OLED• Comparison• Implementation in the mobile

industry(Demo)• Conclusion

PIXEL A minute area of illumination on a

display screen, one of many from which an image is composed.

Each pixel is a sample of an original image; more samples typically provide more accurate representations of the original. The intensity of each pixel is variable. In color image systems, a color is typically represented by three or four component intensities such as red, green, and blue, or cyan, magenta, yellow, and black.

A Photograph of the pixels on a laptop screen. It can be clearly seen that it is a RGB ( Red, Green, Blue ) sub pixels

COLOUR DEPTH The number of distinct colors that can be

represented by a pixel depends on the number of bits per pixel (bpp). A 1 bpp image uses 1-bit for each pixel, so each pixel can be either on or off. Each additional bit doubles the number of colors available, so a 2 bpp image can have 4 colors, and a 3 bpp image can have 8 colors:

• 1 bpp, 2^1 = 2 colors (monochrome)• 2 bpp, 2^2 = 4 colors• 3 bpp, 2^3 = 8 colors• ... • 8 bpp, 2^8 = 256 colors• 16 bpp, 2^16 = 65,536 colors ("Highcolor" )• 24 bpp, 2^24 ≈ 16.8 million colors ("Truecolor")

RESOLUTION The display resolution of a digital

television, computer monitor or display device is the number of distinct pixels in each dimension that can be displayed. It can be an ambiguous term especially as the displayed resolution is controlled by different factors in cathode ray tube (CRT), Flat panel display which includes Liquid crystal displays, or projection displays using fixed picture-element (pixel) arrays.

It is usually quoted as width × height, with the units in pixels: for example, "1024 × 768" means the width is 1024 pixels and the height is 768 pixels. This example would normally be spoken as "ten twenty-four by seven sixty-eight" or "ten twenty-four by seven six eight"

With the evolution of modern technology advancements have been made in the field of displays and resolutions introducing new standards such as HD (High Definition)

LIST OF COMMON RESOLUTIONS VGA (Video Graphics Array) 640x480 XGA (Extended Graphics Array) 1024x768 HD or WXGA (High Definition) 1280x720 HD+ (High Definition Plus) 1600x900 FHD (Full High Definition) 1920x1080 UHD (Ultra High Definition) 3840x2160

UHD is also known as 4K . A normal FHD display has 2 Million pixels whereas a UHD display has 8 Million pixels , 4 times that of FHD, hence the name 4K

Sony shows off their all new 4K Bravia Televisions in the Japan Expo.

HISTORY Display is an electronic device for the

visual representation of data. The originally displays were used for data processing , however later on they were also used for entertainment purposes. Displays have become a fundamental part of our lives, television screens, mobile phone screens, digital clocks, video player, they are everywhere and most of us have these in our pockets at the moment. Our main topic of discussion will be computer displays.

CRT (CATHODE RAY TUBE) The first computer monitors

used cathode ray tubes (CRT). The image quality was poor and they flickered. In 1981 IBM introduced the colour graphics adapter which could display 4 colours with a resolution of 320x200 or 2 colors with 640x200. CRT Displays remained dominant until the new millennium due to their low production costs and great viewing angles.

The original IBM pc with a CRT display from the 1980s. Note that only green is displayed on the screen as the colour adapter was still not introduced.

VIDEO PROJECTOR A video projector is an image projector that

receives a video signal and projects the corresponding image on a projection screen using a lens system. All video projectors use a very bright light to project the image, and most modern ones can correct any curves, blurriness, and other inconsistencies through manual settings. Video projectors are widely used for many applications such as, conference room presentations, classroom training, home theatre and concerts. Projectors are widely used in many schools and other educational settings, sometimes connected to an interactive whiteboard to interactively teach pupils.

Video Projectors are used in computer lab along with smart boards and provide an interactive learning experience

LCD(LIQUID CRYSTAL DISPLAY) A liquid-crystal display (LCD) is a flat

panel display that uses the light modulating properties of liquid crystals. Liquid crystals do not emit light directly. A back light such as a fluorescent light is used to light up the display. Throughout the 1990s, the primary use of LCD technology as computer monitors was in laptops where the lower power consumption, lighter weight, and smaller physical size of LCDs justified the higher price versus a CRT.

A game-changing product, a sleek, slim and vibrant rival to the CRT

TFT (THIN FILM TRANSISTOR) A thin-film-transistor liquid-crystal

display (TFT LCD) is a variant of a liquid-crystal display (LCD) that uses thin-film transistor (TFT) technology to improve image qualities such as addressability and contrast. In a TFT, the pixels are addressed in rows and columns, reducing the connection count from millions down to thousands. The column and row wires attach to transistor switches, one for each pixel.

The one-way current passing characteristic of the transistor prevents the charge that is being applied to each pixel from being drained between refreshes to a display's image

Diagram of Pixel layout in TFT Panels.

The Xperia Z uses a TFT capacitive display which provides natural colours with high quality images and text.

TN (TWISTED NEMATIC) The Twisted Nematic (TN) is a variant of

the LCD and TFT family. Its is the most common consumer display type due its low cost. The pixel response time on modern TN panels is sufficiently fast to avoid the shadow-trail and ghosting artifacts of earlier production. TN displays suffer from limited viewing angles, especially in the vertical direction. Colors will shift when viewed off-perpendicular. In the vertical direction, colors will shift so much that they will invert past a certain angle.

Also, most TN panels represent colors using only six bits per RGB color, or 18 bit in total, and are unable to display the 16.7 million color shades 

TN display under a microscope, with transistors visible in the bottom

IPS (IN-PLANE SWITCHING) In-Plane Switching (IPS) was

developed by in 1996 to improve on the poor viewing angle and the poor color reproduction of TN panels at that time.

Its name comes from the main difference from TN panels, that the crystal molecules move parallel to the panel plane instead of perpendicular to it. This change reduces the amount of light scattering in the matrix, which gives IPS its characteristic wide viewing angles and good color reproduction.

Initial varieties of IPS technology were know by their slow response time and a low contrast ratio but later revisions have made great improvements to these shortcomings. Because of its wide viewing angle and accurate color reproduction (with almost no off-angle color shift), IPS is widely employed all over the world.

The new iPhone uses an IPS LCD display which provides wide viewing angles and accurate colour reproduction.

OLED (ORGANIC LED) OLEDs are used to create digital

displays in devices such as television screens, computer monitors, portable systems such as mobile phones, handheld games consoles and PDAs. An OLED display works without a backlight. Thus, it can display deep black levels and can be thinner and lighter than a liquid crystal display (LCD).

In low ambient light conditions ,OLED screen can achieve a higher contrast ratio than an LCD, whether the LCD uses cold cathode fluorescent lamps or LED backlight.

This is a sneek peek at the rumored upcoming Galaxy Round with a curved OLED display.

OLED is the future of Displays.

COMPARISONS In the next set of slides we shall show

you the comparisons of the previously mentioned technologies.

Please note that information was correct at the time of presentation, it may change over time.

As you can clearly notice that the phone on the top right has the most vivid display with the deepest blacks.

Parameter CRT LCD LED

Brightness Visible in ambient light

Good but poor in direct sunlight

Good in low ambient light, very poor in direct light

Contrast Over 15,000:1 Over 20,00:1 Over 1,000,000:1

Black Level Excellent Poor due to bleed through

Excellent

Ghosting or smearing

No ghosting or smearing but slightly fuzzy

Some blur on old panels

No blur even during fast motion

Parameter CRT LCD LED

Viewing Angle Excellent Poor but getting better on newer models

Excellent

Weight Heavy Heavy , but less weight gain per size increase

Very light

Energy Consumption and Heat Generation

High Low with old backlight, even low with LED

Varies with brightness but lower than LCD

Cost Inexpensive Inexpensive but LED back lit displays are not

Expensive to manufacture

PROJECTOR SCREEN TEST

CONCLUSION In reality, it all depends upon our needs

and wants, OLED has bright vivid colours, IPS has more natural colours, CRT has no input lag and is very cheap.

Abdullah prefers TFT LCD display due to its natural colours.

Zuwayr prefers IPS-LCD, like the one found on the new iPhone (Retina Display)

Muhammad Yaar Prefers the OLED display, like the one found on his S3

Ramay likes projectors due their massive displays

Thank You