computer peripherals “it's been said that a million monkeys typing on a million keyboards...

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Computer Peripherals “It's been said that a million monkeys typing on a million keyboards would reproduce the works of Shakespeare. Thanks to the Internet, we now know that is incorrect.” -unknown

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Computer Peripherals

“It's been said that a million monkeys typing on a million keyboards would reproduce the works of Shakespeare. Thanks to the Internet, we now

know that is incorrect.”

-unknown

Computer Peripherals

VIDEO MONITORS

Cathode Ray Tube

1. Construction

Cathode Ray Tube

2. Operation

Cathode Ray Tube

3. Software concerns

Random Access Memory Digital-Analog

Converter (RAMDAC)

Vertical Sync

Rasterization (aliasing)

Cathode Ray Tube

Pros Responsiveness

(vs. LCD)

Price No Dead Pixels High contrast ratio Higher brightness No Native Resolution Virtually no viewing

angle

Cons Size

Heat

Vertical refresh rates

cause ‘flicker’

Liquid Crystal Displays Thin flat displays Color or Monochrome Made up of segments or arrays Low power draw Used often in portable or battery operated devices because of low power consumtion

Example of a monochrome segmented display

LCD History

1888

1904

1911

1936

19621964

19701972

2008

Friedrich Reinitzer discovers the liquid crystalline nature of cholesterol extracted from carrots

Otto Lehmann publishes his work "Liquid Crystals".

Charles Mauguin describes the structure and properties of liquid crystals.

The Marconi Wireless Telegraph company patents the first practical application of the technology, "The Liquid Crystal Light Valve".

• The first major English language publication on the subject "Molecular Structure and Properties of Liquid Crystals", by Dr. George W. Gray

• Richard Williams of RCA found that liquid crystals had some interesting electro-optic characteristics and he realized an electro-optical effect by generating stripe-patterns in a thin layer of liquid crystal material by the application of a voltage. This effect is based on an electro-hydrodynamic instability forming what is now called “Williams domains” inside the liquid crystal

In the fall, George H. Heilmeier, then working in the RCA laboratories on the effect discovered by Williams realized the switching of colors by field-induced realignment of dichroic dyes in a homeotropically oriented liquid crystal. Practical problems with this new electro-optical effect made Heilmeier to continue work on scattering effects in liquid crystals and finally the realization of the first operational liquid crystal display based on what he called the dynamic scattering mode (DSM). Application of a voltage to a DSM display switches the initially clear transparent liquid crystal layer into a milky turbid state. DSM displays could be operated in transmissive and in reflective mode but they required a considerable current to flow for their operation

• The twisted nematic field effect in liquid crystals was filed for patent by Hoffmann-LaRoche in Switzerland

• Produced displays for wrist watches

The first active-matrix liquid crystal display panel was produced in the United States by T. Peter Brody

LCD TVs are the main stream with 50% market share of the 200 million TVs forecasted to ship globally in 2008 according to Display Bank

Overview – TN (Twisted Nematic)

1. Polarizing filter film with a vertical axis to polarize light as it enters.

2. Glass substrate with ITO electrodes. The shapes of these electrodes will determine the dark shapes that will appear when the LCD is turned on or off. Vertical ridges etched on the surface are smooth.

3. Twisted nematic liquid crystals.

4. Glass substrate with common electrode film (ITO) with horizontal ridges to line up with the horizontal filter.

5. Polarizing filter film with a horizontal axis to block/pass light.

6. Reflective surface to send light back to viewer. (In a backlit LCD, this layer is replaced with a light source.)

With the top polarizer removed and set on top

With the top polarizer removed and aligned parallel to the bottom

polarizer

LCD Terms Resolution: The horizontal and vertical size expressed in pixels (e.g., 1024x768). Unlike CRT

monitors, LCD monitors have a native-supported resolution for best display effect. Dot pitch: The distance between the centers of two adjacent pixels. The smaller the dot pitch

size, the less granularity is present, resulting in a sharper image. Dot pitch may be the same both vertically and horizontally, or different (less common).

Viewable size: The size of an LCD panel measured on the diagonal (more specifically known as active display area).

Response time: The minimum time necessary to change a pixel's color or brightness. Response time is also divided into rise and fall time. For LCD Monitors, this is measured in btb (black to black) or gtg (gray to gray). These different types of measurements make comparison difficult.

Refresh rate: The number of times per second in which the monitor draws the data it is being given. A refresh rate that is too low can cause flickering and will be more noticeable on larger monitors. Many high-end LCD televisions now have a 120 Hz refresh rate (current and former NTSC countries only). This allows for less distortion when

movies filmed at 24 frames per second (fps) are viewed due to the elimination of telecine (3:2 pulldown). The rate of 120 was chosen as the least common multiple of 24 fps (cinema) and 30 fps (TV).

Matrix type: Active or Passive. Viewing angle: The angle the display is completely readable Color support: How many types of colors are supported (coll., more specifically known as

color gamut). Brightness: The amount of light emitted from the display (coll., more specifically known as

luminance). Contrast ratio: The ratio of the intensity of the brightest bright to the darkest dark. Aspect ratio: The ratio of the width to the height (for example, 4:3 (square), 16:9 or 16:10

(wide)). Input ports: Types include DVI, VGA etc.

Color LCDs Active Matrix for high

pixel counts and high-resoultion displays Multiple types

Passive matrix for small amount of segments (e.g. watches, alarm clocks, microwaves.. Etc)

Position of the pixels produces different methods to produce images (see images)

Cutting Edge and Beyond

Organic Light Emitting Diode (OLED)

Cutting Edge and Beyond

OLED

E-Paper

Cutting Edge and Beyond

OLED

E-Paper

Holographic