LCD Monitors

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# LCD Monitors - PowerPoint PPT Presentation

LCD Monitors How they work John Orth and Adam Powell LCD (Liquid Crystal Displays) Polarized Filters LCD monitors use polarized filters to vary the intensity of light emitted from a pixel. Light polarized parallel to the filter is transmitted. Light polarized at an angle is blocked.

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### LCD Monitors

How they work

John Orth and Adam Powell

Polarized Filters
• LCD monitors use polarized filters to vary the intensity of light emitted from a pixel.
• Light polarized parallel to the filter is transmitted.
• Light polarized at an angle is blocked.
• Question – How does anything more than a tiny fraction of perfectly aligned light get transmitted?
Answer - Quantum Mechanics
• In the quantum world everything is governed by probability.
• There is often a significant probability that seemingly impossible events will occur.
• Example: In classical physics a frog that can only jump one foot cannot get out of a two foot deep well.
In a quantum world, a frog that can only jump one foot has a finite probability of getting out of a two foot deep well. The process is called quantum tunneling.
• The transmission of light through a polarized filter is analogous to quantum tunneling.
Even if polarized light is not perfectly aligned with the filter, there is still a non zero probability it will be transmitted.
• This probability function is given by cos Φ.
• It is impossible to tell whether a single photon will be transmitted or not

(unless Φ = 0 or 90). We only know the probability.

(demo)

There are two basic LCD types that operate on the principle just demonstrated.
• IPS (In Plane Switching).
• MVA (Multi Domain Vertical

Alignment.)

• In the off state liquid crystal is perpendicular to the polarized filter and the pixel is black.
• Applying voltage aligns the liquid crystal closer to parallel and light transmits.

(demo)

In quantum mechanics, performing a measurement can cause a change of state in the thing being measured. Example, alter the polarization of a photon.
• TN (Twisted nematic) LCD monitors operate on the principle just demonstrated.
• A spiral of liquid crystals is sandwiched between horizontal and vertical polarized filters.
• In the off state the liquid crystals “twist” the light polarization from vertical to horizontal. Pixel is white.
• Applying voltage disrupts the spiral and the pixel is black.
FLCD/FLCOS
• Bistable Ferroelectric Liquid Crystal Displays
• Bistable Ferroelectric Liquid Crystal On Silicon
• Proposed in 1992 by Thorn EMI
• Keeps a static state without an electric charge
• Color’s are created using a “digital greyscale” method
Sources
• http://www.tomshardware.com/reviews/comparison-15,409-9.html
• http://www.sidchapters.org/sandiego/ColorSeminar-Marcu.pdf
• http://www.mtnmath.com/whatrh/node78.html