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History of Televison

A Prezi for my TV research paper

Stephen Abcdefg

on 19 October 2010

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Transcript of History of Televison

The History of TV TV as we Currently Know it A Prezi by Stephen Cohen Thin, lightweight profile Sensor for remote control Rotatable base Buttons on front of the TV are present but rarely used Wide 14:9 aspect ratio High Definition LCD display with full 1080p resolution Remote control operates basic functions from afar... As well as some more advanced features accessed only with the remote IN THE BEGINNING... The Baird Televisor The First TV!!! CRT The First USEFUL TV! TV Remotes Plasma Screen TV LCD HDTV and Into the Future... LED Displays Quad-HD 3DTV Who knows what could be next? Back to the Past... Television ... There was radio Invented in 1910's Operates over the airwaves on the AM/FM bands Radio let you HEAR your entertainment and news Radio Waves Operates on the radio spectrum 54 to 88 MHz for channels 2 to 6
174 to 216 MHz for channels 7 through 13
470 to 890 MHz for UHF channels 14 through 83 The first funtioning "television" used spinning disks and a light source to produce images Images flashed onto a light sensitive cell and then transmitted line by line as electrical impulses Images decoded by reversing the process The first remotes worked over a wire connected to the TV For a short time, there were remotes which used dog whistle type sounds to communicate with the TV Modern remotes now use a sort of infared "morse code" When you press a button, you complete an electrical circuit withtin the remote. This is how the remote knows you pressed it. FUN FACT: Did you know that, to a digital camera, your remotes "invisible" morse code looks like purple light? Popular radio shows of the 1930's There are three main differences between SDTV and HDTV Apect Ratio Resolution Frame Rate This is the ratio between the two sides of the screen. HDTV sets have a ratio more like that of a movie screen (14:9), this eliminates the black bars. This is how many pixels fit on the screen. More pixels equal better picture quality. An SDTV has a resolution of 704 x 480 while an HDTV can have up to 1920 x 1080. This is how many times a "frame" (a still image that makes up a moving picture) flashes across the screen per second. These framerates can be either interlaced or progressive. Interlaced means that each frame only fills every other line of pixels on the screen, while progressive uses all of them. SDTVs can techinically achieve some of the same framerates as HD, but the HD models are more likely to have the higher 60i - 60p rates. A thin grid of cells filled with xenon gas is samdwiched between the horizontal and vertical lines of a grid of electrodes Some neon gas may also be present. Each pixel is made up of three cells, one for red, blue, and green.Each of these cells is coated with a phosphor for its respective color. To light up a pixel, it runs an electrical current between the electrodes that intersect at the three cells that make up that pixel. The voltage level determines the intensity of the color. the electrified plasma releases UV radiation which in turn excites the phosphors. A heated filament, or "cathode," releases electrons which are focused and fired at high speeds out of the "anodes." (A and C) The beam of electrons hits a phosphor material coated on the screen causing it to light up.
(D) A phosphor is a material that lights up when exposed to radiation. "Cathode" is another name for the negative terminal of a circuit... ...While "anode" means positive. Following with the TV signal, electromagnetic coils wrapped aorund the tube steer the electron beam across the screen line by line while the cathode varies the intensity of the electron beam to create various shades of black, gray and white. In a color TV, there are three electron beams and three different colored phosphors per pixel (red, green and blue). All three beams move together at the same time, each targeting one color. The proposed next generation of High Definition picture quality is proposed to be 3840 x 2160, a resolution four times that of the now current 1920 x 1080. Early TV Shows I Love Lucy Gunsmoke Wagon Train Over 120 Westerns! Bonanza The Virginian/Men From Shiloh Variety Shows These were based on old radio shows Game Shows LCDs work by blocking light provided by a florescent backlight. The light from the backlight is polarized before it runs through the liquid crystal substance iquid rystal isplay Polarized filters block all light that mathces the direction of its slits The light passes thorugh the naturally twisted LCS. This twisting changes the lights orientation to allow it to pass through a second polarization filter. The light then passes throught colored lenses that make up RGB pixels. To change the color of a pixel, electricity is run through the LCS of the subpixels, causing it to gradually untwist. The more electricity, the more it untwists. Because the LCS is no longer changing the orientation of the light, less of it can pass through the second polarizer, making the subpixel darker. Use the same display technology as LCD TVs. The name "LED" comed from the different type of backlight. Two main types of LED backlights: Edge Lighting and Full Array Edge Lighting has a string of LED lighting built in to the edge of the screen. These displays are thinner than any other type of display, however, they don't have as deep black levels. Full Array screens have LEDs backlighting the entire screen. These screens can employ "local dimming," which lowers the backlighting on a specific area of the screen, leading to better images. Both types of LED displays: are more energy efficient have no mercury have more balanced color saturation Active Shutter Glasses Alternate frame Sequencing Doubled frame rates One frame for each eye LCS darkens the lens for the eye that isn't supposed to see the current frame. The glasses are synced to the screen via a type of wireless frequency.
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