Display Technology INFO410 & INFO350 S2 2015 Jack Pinches INFORMATION SCIENCE

Outline CRT Plasma Display LCD Projectors DLP https://0.s3.envato.com/files/20601835/Pixels.jpg

Electrons (-) attracted to anode (+) Cathode Ray Tube (CRT) Electrons (-) attracted to anode (+) Electron beam flies through vacuum, hits the flat screen. Screen phosphor coated. Anode: positive Cathode: negative Phosphor: substance that phenomenon of luminescence. Luminescence: emission of light not from heating. In this case its electrical energy. http://electronics.howstuffworks.com/tv3.htm

Phosphor inner close up Cathode Ray Tube (CRT) Electron guns Electron beams Focusing coils Deflection coils Anode connection Mask Phosphor layer Phosphor inner close up https://en.wikipedia.org/wiki/Cathode_ray_tube#/media/File:CRT_color_enhanced.png

Holes aligned with phosphor Fire beam as needed. Cathode Ray Tube (CRT) Shadow mask Holes aligned with phosphor Fire beam as needed. Mask: thin metal screen, perforated with small holes. White: All beams. Black: No beams. http://electronics.howstuffworks.com/tv10.htm

Cathode Ray Tube (CRT) Advantages: Good black level Reliable Viewing angle Disadvantages: Bulky Power consumption Burn in Screen size limited Health Concerns: Ionizing radiation Toxicity Flicker High frequency noise Radiation: xray radiation a result of electron beams bombardment of the mask. Toxicity: Toxic substances used, likely older CRTs. Flicker: some low end monitors have a low refresh rate, and so can cause discomfort. Noise: Operation of some monitors can cause a high pitched tone.

Burn in example Uneven usage of pixels. Phosphor compounds lose luminance over time. Burn in example https://upload.wikimedia.org/wikipedia/en/9/97/Emerson-McDonalds_CNN_Burn-In.jpg

Plasma Display Panel (PDP) Tiny cells containing gas Voltage causes plasma Releases UV photons Photons interact with phosphor Mg0 = Magnesium Oxide Plasma = ionized gas with positive ions and free electrons, resulting in roughly no electric charge http://electronics.howstuffworks.com/plasma-display2.htm

Plasma Display Panel (PDP) Advantages: Produce deeper blacks High refresh rate and response time Cheaper? Disadvantages: Screen burn in Bulkier High power consumption Altitude requirements

Liquid Crystal Display (LCD) Backlight Millions of pixels Polarizing filters Liquid crystal http://www.explainthatstuff.com/lcdtv.html

Liquid Crystal Display (LCD) Backlight Horizontal filter Horizontal light waves Electricity off Vertical light waves Vertical filter Pixel lit http://www.explainthatstuff.com/lcdtv.html

Liquid Crystal Display (LCD) Advantages: Thinner, lighter Lower power consumption Lower radiation emission Size variability Disadvantages: Image persistence Black levels can be poor Dead pixels Viewing angle Fixed colour depth Image persistence: similar to burn in. Seems to be also from non uniform usage of pixels. Exact reasons unclear. Reversible, leave display off. Colour depth: number of bits used to indicate colour in a single pixel

Light Emitting Diode Projector (LED) Projectors Light Emitting Diode Projector (LED) Liquid Crystal Display Projector (LCD) Digital Light Processing Projector (DLP) Two general types: Transmissive Reflective Transmissive: passing light through panels Reflective: using a mirror to direct the images

Digital Micromirror Device (DMD) Array of mirrors (reflective) DLP Projector DLP chip: Digital Micromirror Device (DMD) Array of mirrors (reflective) Up to 8.8 million Hinges, independent movement DLP chip, rectangular array of mirrors on hinges Hinges to tilt towards the light source, or away from it. This gives a grayscale image. http://www.ti.com/lsds/ti/dlp-technology/about-dlp-technology/how-dlp-technology-works.page https://en.wikipedia.org/wiki/Digital_Light_Processing#/media/File:DLP_Logo.svg

DLP Projector Beam of light Spinning Wheel DMD chip Lens Projection Screen

Convergence (single chip) Image persistence Projector size DLP Projector Advantages: Fully sealed chip Convergence (single chip) Image persistence Projector size Colour degradation Disadvantages: Colour wheel not sealed Rainbows Restricted zoom capabilities Representation of greys Rainbows: issue with single chip projectors, displaying sequential colour. Meaning there is actually only 1 colour on the screen. Bright objects appear to have trails of multi-coloured light, often on a dark background. Some people notice these.

LCD Projector LCD panel Tiny cells Mirrors divide light Three panels Combiner/Prism Dichroic mirrors: reflect only certain colours (specific wavelengths) Panels: all have same image, but different hues. http://www.projectorpoint.co.uk/images/LCDProjectorworks.gif

Generally less expensive than DLP Support use with zoom lenses LCD Projector Advantages: No moving parts Generally less expensive than DLP Support use with zoom lenses Sharper image Disadvantages: Pixels can burn out Dust can interfere Limited lifetime Black levels Size and weight Image persistence Limited lifetime: panel degradation causing colour degradation

Resources Title Slide Image: http://www.smarttvradar.com/wp-content/uploads/2013/01/tv.jpg http://www.displaymate.com/ShootOut_Comparison.htm http://www.explainthatstuff.com/lcdtv.html https://www.youtube.com/watch?v=qOsibeDX8jM http://www.ebay.com/gds/Understanding-the-Differences-between-LED-LCD-and-DLP-Projectors-/10000000177630814/g.html http://www.projector-guide.com/projector-guide/projector-structure/lcd-disadvantages.html