About LCD Monitors and CRT Monitors

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  • 7/31/2019 About LCD Monitors and CRT Monitors


    About LCD Monitors and CRT monitors - Comparison of technology andadvantages

    - A comprehensive list of characteristics, advantages and disadvantages of LCDs and CRTs

    Is it time to upgrade to LCD monitors from your CRT computer monitors? There is no doubtthat CRT computer monitors have a very limited mass-market lifespan. Several manufacturers have

    stopped manufacturing CRTs completely, which means they are not easy to purchase, yet there areattributes of CRTs that LCD screens have not been able to match. The LCD is simply not a good choicein some environments based on their needs. The characteristics your job's requirements will helpdetermine whether you switch to an LCD.

    What's inside CRT monitors?Despite the decades of technologicaladvances in computing, the work horse of personal computing has been,until very recently, the large, desk mounted CRT monitors. These computermonitors managed to revolutionize computing, and allowed personalcomputers to become a fact of daily life by utilizing the technology of thecathode ray tubes; a technology first suggested for transmitting images in1907. Yet, if opened by professionals for examination, what you would seeinside the standard CRT monitor is basically the inner workings of acathode ray tube television.CRTs produce images when the moving electron beam inside the largecathode tube moves back and forth, firing electronic beams at phosphordots on the inside of the glass tube line by line. The phosphors in your CRTare chemicals that emit red, green, or blue light when struck by electrons.The smoothness of the image is determined by the scan rate of the beam(screen flicker increases as the speed decreases).

    LCD monitors, liquid crystal displays, are flatpanels. This digital technology was first invented in1971.Initially used in watches and calculators, itsfunctionality was quickly adopted and began redefiningcomputer, medical, and industrial electronics. Incomputing, LCDs have been used for years in laptops,and are now ever present as flat panel computer

    screens, as well as being integrated into new technologytelevision screens. It took until 2003 for the volume ofthese flat screens to escalate and capture half themonitor market. As of 2005, LCD monitors exceed CRTssales by more than 2-to-1. They are also known as flatpanels in both computer monitor and television screendesign.

    Going Within

    Basic CRT internals Sandwiched layers of an LCD designHow are images created in LCD monitors? There are no cathode ray tubes in the very thin LCDmonitors. Instead, thin "sandwiches" of glass contain liquid-crystal filled cells (red, green and blue cells )that make up a pixel. Arrays of TFTs (thin film transistors) provide the voltage power causing the crystals

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    to untwist and realign so that varying amounts of light can shine through each, creating images. Thisparticular sensitivity to light makes LCD technology very useful in projection (such as LCD front projectors),where light is focused through LCD chipsSpecifically, there are five layers to the flat display: a backlight, polarized glass sheet, colored pixellayering, coating of liquid crystal solution that responds to signals off a wired grid of x and y coordinates,followed by a second glass sheet. To create an image, electrical charges, precision coordinated in various

    degrees and volts effect the orientation of the liquid crystals, opening and closing them and changing theamount of light that passes through specific colors of pixels. Liquid crystal display technology hasincreased its accuracy, thanks to advances such as thin film transistors (TFTs - also known as active-matrix technologies) that can produce sharp and more accurate color images than earlier passive-matrixtechnologies.

    Advantages of LCDsLight weight; can be about 15 lbs for a thinLCD.Smaller footprint on desk leaving, freeing upwork area on the user's desk.

    Flicker free screen.More usable display area than on comparablysized CRTs.Low frequency radiation is practicallyeliminated.Easy adjustment, storage, and movementEnergy efficient, using only 1/3 to 1/2 theelectricity of CRTs, and they don't generateheat.Potentially less eyestrain due to reduced screenglare.Good for basic web surfing.Newest TFT liquid crystal technology hasprovided LCDs in competitive position withCRTs for image and color clarity.OLED, a new technology (Organic light-emittingdiodes) in limited use presently in handheldpersonal video players, uses little power andprovides a better image than present LCDtechnology; it thus holds the promise of makingup for a significant weakness in LCD imagequality.Plentiful mounting arm options available,enabling these light LCDs, whether computer orTV monitor to be ergonomically raised off thework surface.

    Advantages of CRTsSignificantly lower cost compared to CRTs,because the technology has matured.Color fidelity, so essential for graphic artists,has not been matched by LCDs.Contrast ratio allows perception of true black.Darks are darker.Ability to adjust (multisync) images.Good for basic web surfing as well as usesrequiring crisp, color-rich graphics and sharptext.Work better at multiple resolution.Displays full motion video better.Give you more pixels, translating to greaterscreen detail and ability to view more of adocument without scrolling.Screen images viewed from side angle are asgood as when viewed straight-on (no dilution ofclarity or color.)Modern versions may include a sleep-mode forenergy efficiency.Many now available with flat viewing screensfor less glare, viewing convenience.Strong glass screen can withstand routinehandling, and is not easily damaged by casualtouch.

    Disadvantages of LCDs Disadvantages of CRTsFragile screen; may result in both screen andbacklight lamp damage if touched or handled.Thus, not recommended in environments whereit may be handled roughly.Contrast ratio causes darkness to not bedisplayed true. Darkest areas may be viewedas dark gray rather than black.

    Radiation Emission; ELF from 60 Hz to 75 Hzand VLF from 10kHz to 30kHz.Larger size takes up more desk space; thebigger the screen, the bigger the footprint.Heavy weight, 40 lbs and more.Heavier size limits easy and convenientmovement.

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    Designed only for one optimum resolution; can'tadjust images.Best view of screen is straight-on, limiting clarityand colors of information for those viewing froman angle.The backlight is the potential weak link and its

    failure can be costly. Many warranties onlycover it for 1 year.

    Expends more energy and throws off heat.Measurement differs from usable screen area.EX: a 19" CRT provides about 18" of usablescreen area.Less off-the-desk mounting options available.

    CRT "Flat Screens". While most CRT monitors have in the past been designed with a curved screen,technological innovation has led to the manufacture of CRT computer and television glass screens that arealmost completely flat. These Flat Screens are still bulky in size and weight due to the cathode ray tubewithin, but glare is all be eliminated and the overall quality of viewing is considered better due to the screendesign. To learn about the distinction between the terminology of flat screens and flat panels, check Aboutflat screen & flat panel.Addressing CRT radiation concerns: The health effectsof the radiation emitted by CRTs continues to be debated.Meanwhile, concerned users of CRTs are able to

    purchaseanti-radiation/glare filters without foregoing theuse of their existing PC monitors. These computer filters arealso available for flat panels with a privacy option (see phototo the right)