What is an LCD Display and how it works? more

What is a Plasma Display and how does it work?

Advantages of LCD Displays

Resolution options

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What is HDMI Plasma and LCD Connections

DTV and HDTV

What LCD Display and how it works?
 

How do LCD TVs work?
Reviewer: Jack Burden

How does a LCD (Liquid Crystal Diode) TV operate?

The Basics: LCD monitors work by blocking light. By sandwiching a solution of TN liquid crystals between two perpendicularly aligned panes of polarized glass, it becomes possible to manipulate the intensity of light as it passes through this crystalline matrix and out the glass panel at the other end. Depending on the voltage of the electrical charge running through them, liquid crystals will untwist so that the intensity of light able to pass through the second polarized pane is affected. Basically, these displays can switch between light states (where the liquid crystals are fully twisted) and dark states (where the liquid crystals are fully untwisted), or somewhere along the gray scale in between.

Addressing: A liquid crystal display consists of an array of tiny segments-called "pixels"-that are manipulated to form images or to present information. Addressing is the process by which pixels are turned on (which disables the passage of light) and off (which enables the passage of light) so as to create an image on the polarized display pane in front of you. So-called active-matrix LCD TVs employ thin film transistors (TFTs), or tiny switching transistors and capacitors arranged in a matrix on a glass substrate, to direct electric charges down columns to reach a particular pixel. This, in turn, causes the liquid crystals to untwist and "display" a predetermined amount of light generated by the light source-usually a florescent bulb-in back of them.

Color (Re) Production: The light source in an active-matrix LCD monitor is a florescent bulb, which emits white light through a polarized glass pane behind the liquid crystal solution. Theoretically, then, you can start with a white display: This is one where its liquid crystals are completely twisted and therefore able to direct the full spectrum of light out through the polarized display screen in front of you. Since all wavelengths can pass through, the full spectrum of light can be manipulated to create the desired color. To achieve a full color pallet on your LCD display, each pixel is divided into three subpixels-red, green, and blue-that work in conjunction to determine the LCD pixel's overall hue. These subpixels are created by subtracting certain wavelengths, and the color(s) corresponding thereto, using special filters. By exploiting a combination of red, green, and blue subpixels of various intensities (or gray scales), a single pixel triad can reproduce approximately 16.8 million colors.

What exactly is a Liquid Crystal Diode (LCD) TV?

LCDs are all around us. Liquid crystal displays so prevalent, in fact, that most people couldn't get through their day without using one. This technology is utilized in digital clocks, microwave ovens, car dashboards, calculators, stereos, thermometers, and even some bathroom scales! The applications for liquid crystal displays are almost limitless, so it should come as no surprise that this technology has revolutionized the most basic home appliance of all-the television set.

Liquid crystal technology has given birth to those slim, cool-looking, bright displays that are popping up everywhere from bank lobbies to living rooms. But how does it work?

What makes a crystal "liquid"?

The twisted nematic (TN) liquid crystal is the most common type of liquid crystal being used in display applications today (e.g., LCD televisions, LCD monitors, and LCD projectors). It has a naturally twisted crystalline structure. A particular feature of this crystal is that it reacts to electric currents in predictable ways-i.e., by untwisting to varying degrees depending on the voltage of the current to which it is exposed. Hence the "liquid" part of the crystal's moniker: Rather than being an oxymoron (How can a solid also be a liquid?), the term refers to the relative pliability of the crystals themselves, which is to say, their twistability.
 

FIND OUT WHO MAKES WHICH PLASMA OR LCD DISPLAYS  Plasma and LCD Mfg. Information

The United States Display Consortium was established in July of 1993 as a partnership created from public and private industry. The Consortium provides a neutral forum for flat panel manufacturers, developers, users, equipment and material suppliers.
USDC's mission is to support our member companies and affiliates in building a world-class competitive display industry.

We're accomplishing this mission by:
1.  Supporting and developing an infrastructure for supply of next generation process equipment, materials and components to the worldwide markets;
2.  Analyzing, benchmarking, and reporting on commercial and military market trends and opportunities;
3.  Presenting member views on issues such as public policy and standards;
4.  Providing opportunities for member participation in technical and financial forums;
5.  Fostering international cooperation among display makers, integrators, and equipment materials and components suppliers;
6.  Facilitating and leveraging relationships between member companies and academic communities.
7.  Promoting innovation and opportunities in display applications through various media outlets.

We invite you to take a tour of the USDC website, and explore our unique industry/government partnership.

FIND OUT WHO MAKES WHICH PLASMA OR LCD DISPLAY  Plasma Mfg. Information AND WEBSITES

Resolution options: Your basic choices for native, or true resolution are the following:

VGA, or "640 x 480" – This is the lowest data resolution currently on the market, and usually the least expensive.
SVGA, or "800 x 600" – This is a popular resolution today, because most notebook computers are SVGA. Matching the plasma resolution with the computer resolution will produce the best results.
XGA, or "1,024 x 768" - XGA plasma tvs are generally more expensive, and are the second most popular resolution format. Many of the newest products are coming out in XGA. They are getting more popular as prices drop and the use of XGA notebook computers increases.
SXGA, or "1,280 x 1,024" – SXGA products are high resolution, and notably more expensive than XGA. These products are targeted for high end personal computer users and low end workstation users. They are used primarily for command and control, engineering and CAD/CAM applications where acute resolution of small details is important.
UXGA, or "1,600 x 1,200" – UXGA is for very high resolution workstation applications that are detail or information intensive. These are expensive plasma tvs that support a broad range of computer equipment. Relatively few products on the market have this native resolution.

Native Resolution
The number rows of horizontal and vertical pixels that create the picture. The native resolution describes the actual resolution of the plasma display and not the resolution of the delivery signal. When the delivery format is higher or lower than the flat screen's native pixel resolution, the delivery signal will be converted to the plasma's native resolution through an internal converter. Generally, the closer the incoming picture signal is to the native pixel resolution on the plasma display monitor - the better the picture. For example, a VGA computer signal of 853X480 will match up perfectly with a plasma monitor with 853X480 native pixel resolution, while an XVGA signal of 1024X768 will match up better with a plasma monitor that has the higher resolution of 1024X1024. There are more considerations here that deal with the quality of the internal converter/scalar, and also whether or not the monitor is progressively scanning (853X480) or interlacing the signal (1024X1024). All 42" inch plasma display monitors are HDTV ready, while none will show the true HDTV signals of 1080i. However, they will benefit from the better signal and show something very close.

The options available for native resolution include: 1024x1024, 1024x768, 1280x768, 1365x768, 640x480, 825x480, 853x480.

Benefits of Higher Resolution: High resolution plasmas are able to show more picture details than low resolution plasma tvs. Also, since there are more pixels used to make the image, each individual pixel is smaller, so the pixels themselves become less visible on the screen. However, you will pay more for higher resolution. So choosing the right resolution is the first step in finding the right plasma screen tv.

Please view our DTV and HDTV comparison chart for further digital tv information.
 

Digital television, or DTV, is the new industry standard for broadcasting picture and sound using digital signals, allowing for dramatic improvements in both picture and sound quality vs. conventional NTSC analog programming. DTV programming can be delivered in either of two basic formats: standard analog definition (SDTV) or high definition (HDTV).


 

 
DTV Format Comparison
Transmission Type
Analog Digital Digital Digital Digital
  NTSC Standard Definition Standard Definition High Definition High Definition
Maximum Resolution 480i 480i 480p 720p 1080i
Aspect Ratio 4:3 4:3 4:3 or 16:9 16:9 16:9
Channel Capacity 1 5-6 5-6 1-2 1
Description Standard TV as we know it today Good Picture and Sound —DVD or DBS Quality Better, depending on source; can be outstanding Best Possible Best Possible
 



HDTV is the highest form of digital television, delivering up to 1,080 interlaced scan lines. HDTV produces images that far surpass any you've ever seen in a home environment! SDTV, or Standard Definition, also represents a dramatic improvement over today's TV, with the added benefit of allowing stations to broadcast multiple programs within the same bandwidth as an HDTV signal.


 

 
DTV Format Detail
Scan Lines
Scan Rate Pixelization Frame Rate Aspect Ratio Formats
SDTV 525 total
480 active
15.75 kHz (60i) 480 x 640 24p, 30p, 60p or 60i fps 4:3 4
525 total
480 active
31.5 kHz (60p) 480 x 704 24p, 30p, 60p or 60i fps 4:3 or 16:9 8 (4x2)
HDTV 750 total
720 active
45 kHz
(60p)
720 x 1080 24p, 30p, 60p 16:9 3
1125 total
1080 active
33.75 kHz
(60i)
1080 x 1920 24p, 30p, 60i 16:9 3

The right distance depends on the size of your TV:

  • For 20 to 27-inch displays, you should be able to watch comfortably from 2.5 to 5 feet away.
  • For 32 to 37-inch TVs, you should sit back 6 to 8 feet from the screen itself.
  • For 42 to 46-inch TVs, you'll need 10 to 14 feet between you and the screen.
  • 50-inch LCD displays look best when viewed from 12 to 16 feet away.

 

What are the advantages of LCD Displays?

To help you find the best LCD screen for your application, we've put together this guide to the features you should look out for. You'll find most of these features listed for each screen we sell under the Buy section.

Reviewer: Jack Burden

Besides looking cool and oh-so futuristic in your living room, what are the advantages of owning an LCD TV or monitor?

It's easier to watch. Flat panel TV displays like LCDs and Plasmas are significantly brighter and feature higher contrasts than traditional CRT sets. Which means that an LCD TV will perform exceedingly well under most ambient light conditions. A brightly lit room won't wash out its picture, nor will lamplight cause a glare on your television screen. The beauty of these flat screens is that you don't have to turn out the lights to see the image clearly and easily. Nor do you have to worry about eyestrain, since neither LCDs nor Plasmas flicker the way old-fashioned TVs do.

And, you can watch TV from almost anywhere in a room since flat-screen LCD television displays can have up to a 160° viewing angle, which means your TV will look good when viewed from any point 80° in either direction from the center of the display.

One issue affecting the overall quality of the picture reproduced on LCDs has to do with dot pitch. This term refers to the distance between subpixels of the same color in adjoining pixel triads. The closer these "dots" are to one another, the sharper the resolution will be. This is especially true when displaying computer signal images and graphs. And the picture in front of you will be more realistic and detailed. Higher dot pitches also increase the viewing angles of LCD panels. Since dot pitch is measure in millimeters (mm), a good rule of thumb is this: Smaller dot pitches make for sharper images. You generally want a dot pitch of .28mm [" 10,000 pixels/in2 of your display] or finer.

Note: Plasma TV displays have long been touted as having wider viewing angles than comparably sized LCD monitors. But recent improvements in quality have made LCD televisions and monitors comparable to Plasma TVs with respect to their viewing angles. According to Sharp, a leading manufacturer of LCDs, the newest generation of LCD displays have just as good viewing angles as plasma sets, but this is only true of the better brands. In any event, even the best LCD monitors have yet to achieve the breadth of viewing angles found on typical Plasma monitors.

You can watch your new television right out of the box because the tuner is included. LCD TVs generally come with tuners and speakers already built in, so they're more or less plug-and-play devices. Since most LCD TVs don't require external tuning devices, they are ideal for smaller applications, where space is at a premium (like bedrooms and small living rooms) or where clutter is inconvenient (like crowed kitchen countertops).

Note: Some LCD televisions have outboard media receivers, though many-like Toshibas-don't. Always inquire about extra hardware before you buy: You won't always see your LCD monitor pictured with an external receiver (even if it has one), so it's up to you to find out whether there is any "extra" hardware you need to know about.

The picture is smooth, colorful, and (best of all) wide. LCDs have none of those annoying scan lines that conventional sets do. This owes to the fact that each subpixel has its own transistor electrode, which creates smooth, evenly lit images across the entire surface of the display. It also enables these displays to reproduce images that are saturated with color. [256 shades of red x 256 shades of green x 256 shades of blue " 16.8 million different colors!]

Note: All this requires an enormous number of transistors-upwards of 2.4 million for displays supporting a typical resolution of, say, 1024x768. This means that, if there is a problem with any one of these transistors, a subpixel will be affected, which causes the pixel associated with it to fail. Dead pixels will emerge over time and with use. In general, though, the number of dead pixels affecting a given display will be few enough so as to go virtually unnoticed by the average viewer.

Recent advances in LCD technology have markedly increased the response time of these displays, resulting in even smoother on-screen presentations. One way to think about response time is in terms of the amount of time it takes a pixel to "refresh" itself-i.e., to go from being active to being inactive, which is to say, ready to be re-activated). Response time is measured in milliseconds (ms), with the best LCD monitors now clocking in with response times under 20ms. Slower response times (>20ms) can cause the image on the panel to lag and appear jerky, an effect known as "streaking" or "trailing." Another phenomenon associated with slower response times is "ghosting." This occurs when the display is made to switch quickly from light to dark states (or vice-versa). In these instances, on-screen images may appear to stay on the screen belatedly.

LCD displays come either with a 16:9 aspect ratio (i.e., 16 units wide to 9 units high), the proper one for viewing HDTV and for watching DVDs, or with a 4:3 aspect ratio, the norm for most broadcast television shows. If you opt to go with a widescreen (16:9) display, does this mean that you'll have to watch some shows where the image is distorted or stretched unnaturally? No. When displaying a "normal" or 4:3 picture image from satellite, VCR, or cable TV, the image can be viewed in a number of ways-in its original format (with black or gray bars on the sides of the screen), or in "full" mode (where the image is converted or "stretched" using specially designed algorithms to reduce the visible stretch marks as much as possible). Again, the quality of the picture produced under such circumstances depends largely on the quality of the television with which you scale-up 4:3 pictures or scale-down 16:9 ones. Nevertheless, this is only a temporary dilemma: Since HDTV is shown in widescreen, this is the format of the future for much of broadcast television.

The display is multi-functional and long-lived. An LCD is a television monitor, capable of displaying HDTV, regular TV, and home video. It's also a computer monitor. In fact, it can accept any video format. LCD displays typically include inputs for (a) composite video, (b) S-video and component video, and (c) one or more RGB inputs from a computer. Because of the high resolution of LCDs, text and graphics look especially sharp when viewed on them, which makes them the best solution for displaying data and web-based content.

Note: Some LCDs (including many by Sharp) do not come with RGB inputs. If you plan to utilize your LCD display as a computer monitor, be sure to check out the specs of the unit you're thinking of purchasing.

You can expect to use your LCD monitor in many capacities for many years: The average lifespan of one of these displays is 60,000 hours. If watching TV was your full-time job, and you did it 24 hours a day, it would take you almost 7 years to wear out your LCD display. With more normal viewing habits of, say, 8 hours per day, you can extend the lifespan of your TV by a decade or more (to about 20 years)!

Note: The lifespan of an LCD display is generally longer than that of similar-sized plasma displays. Some manufacturers claim that their LCDs can last upwards of 80,000 hours when used continuously under controlled conditions (e.g., in a room with "standard" lighting conditions and 77° temperatures throughout). Just how realistic such claims are is debatable. After all, whose living room has no windows and remains at a perfectly comfortable 77 degrees year-round?

A more immediate concern is the actual lifespan of the light source in your LCD. This is perhaps THE critical component of your display unit. It is particularly important for maintaining a proper white balance on your TV. As these florescent bulbs age, colors can become unbalanced, which could result in too much red, for example, in your picture. So, it pays to buy name-brand displays. You will definitely pay more for better LCD display brands like Sharp, Toshiba, JVC, or Sony than you will for cheap Chinese or Korean variety knock-offs, but you'll get a backlighting bulb of higher quality and, in the end, a TV whose colors will stay truer longer.

In some cases, the warranty for this particular feature can be shorter than for the display as a whole. This means you might have to buy a whole new LCD monitor because the coverage on its backlight has expired. Moreover, some bulbs can be replaced, while others are built in to the unit itself. You should definitely do some research on the backlighting system, how it's configured, and how it's warranted.

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When working with us, you can be assured that your computers and peripherals will be delivered Clean, Working and On Time. 

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You get all this with outstanding Service, Trained Support Personal, and Competitive Pricing.

 

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