PC monitor technology and interfaces

Monitors general information

    PC monitor system is complicated system, but luckily for us it's one that's easy to understand. The following description is centered on traditional analogue CRT PC monitors.

The video adapter in PC sends the signals from it's image memory at fixed rate (usually configurable) through the DAC (digital to analog converter) circuit to the monitor connector on the graphics card. The DAC converts numeric pixel color values to voltage levels for red, green, and blue which are sent to monitor through the monitor cable. Most monitors today use the traditional CRT, which works on the same scientific principle as a television set. This vacuum tube produces an image when an electron beam strikes the phosphorescent surface inside the monitor. Normal PC VGA monitors nowadays are so called "non-interlaced" monitors. The computer requires a "video Interface" sometimes referred to as a video card to communicate with your monitor. Your monitor is the single most important component of your computer system if you want to get good picture quality (also the graphics card can contribute to this).

 

   The visual quality, depends on the quality of your monitor. Consumers have now become more concerned about the visual quality. The flat screens, high resolution, high refresh rates, and recently the USB and solid state screens top the list of desirable features. The multimedia monitor includes loudspeakers of some sort, maybe a microphone and in some cases a camera for video conferencing all in the same box as the monitor.All analog monitors can produce thousands of colors, it is inherent in the design. The limitation on color registration is directly related to what is available in the interface card and the mode selected. There are practically infinite number of colors possible with the analog monitors (although they can not properly display all natural colors correctly).

   Resolution is the number of pixels the graphics card is describing the desktop with, expressed as a horizontal by vertical figure. Standard VGA resolution is 640 x 480 pixels. The commonest SVGA resolutions are 800 x 600 and 1024 x 768 pixels. A typical PC monitor is designed to accept signals at wide resolution and frequency range. When you change the resolution on refresh rate on monitor, just the scan frequencies that are changing to accommodate the new timing/pixel format. The focus (which is sort of the electron beam width, at least as it is seen at the screen) MAY be altered slightly as well, if the monitor has the capability of storing adjustments for that and other parameters (geometry, convergence, etc.) for specific timings, although it is VERY unusual for focus to be included in this. Please not that the monitor physical dot pitch can't change - that's a fixed physical parameter of the CRT itself - but the physical dots on the screen (or the holes in the shadow mask) really have nothing at all to do with the logical pixels of the image, other than being one of the things which ultimately limits the resolution. The scan frequencies do not necessarily change at all when you change the resolution. What happens is that the signal as seen on the VGA plug has (for example) 1024 discrete values between 2 consecutive line syncs as opposed to 800 discrete values and 768 line syncs between frame syncs as opposed to 600 (assuming non interlaced). Typical PC CRT monitor an display all resolutions from the lowest up to the highest supported resolution well. If you have a modern flat panel display, things can be different. On TFT monitors they specify a "recommended" resolution that the TFT works best at and when not run at this resolution they get seriously blocky and in some cases unreadable text.

    Refresh rate, or vertical frequency, is measured in Hertz (Hz) and represents the number of frames displayed on the screen per second. Too few, and the eye will notice the intervals in between and perceive a flickering display. The world-wide accepted refresh rate for a flicker-free display is 70Hz and above (preferably 75 Hz or more). The flicker is strongly dependent upon visual angle, because eye peripheral vision response is faster than the higher resolution center of field vision. The bigger the monitor, or the closer you are to it, the worse the flicker will be, so you will need higher refresh rate to get "flicker free" picture. CFF (Critical Flicker Fusion) also depends on illumination levels. The CFF frequency is lower at lower illumination levels. As the height of the picture increases, it is necessary to increase the number of horizontal lines to create a smooth line-free display image. To do this, the monitor and the interface card increase the frequency of the repetitive horizontal scan rate.

    In order to consistently reproduce the video information at a high resolution, the monitor must have a wide video bandwidth. In order for the term to be meaningful for comparison purposes, the bandwidth expressed in mhz. must be within +- 3dB You might see a term "sync signal" sometimes.All computer monitors require a "sync" signal which determines the resolution of the display. Some monitors require the sync signal to be a separate electrical connection, some monitors require the sync signal to be mixed in with the green video signal (sync on green). Some monitors support both separate sync and sync on green. PC VGA card uses separate sync signals and PC monitors are designed to accept at least this sync format.

   The term "dot pitch" is the measurement in millimeters of the distance between two adjacent phosphor color elements. There are two color phosphor systems in use today in CRT monitors: triad dot shadow mask (most monitors) and aperture grille (used in the trinitron tube from SONY). NEC has developed a hybrid mask type, called slotted mask, which uses elliptically-shaped phosphors grouped vertically and separated by a slotted mask.

Here are some guidelines for suitable resolutions for different monitors:

• 14 inch monitor is adequate for 800 x 600 resolution.
• 15 inch monitor is adequate for 1024 x 768 resolution.
• 17 inch monitor is adequate for 1024 x 768 resolution.
• 19 inch monitor is adequate for 1280 x 1024 resolution.
• 21 inch monitor is adequate for 1600 x 1280 resolution.

    If you use a higher resolution exceeding these guidelines, a very good monitor may deliver adequate pictures but you can also run into a poor quality picture. Keep in mind  what frequencies and resolution your monitor can handle. Trying to use frequencies and resolutions that the monitor was NOT designed to support can severely damage your monitor. To make the monitor installation easy, VESA has produced several standards for plug-and-play monitors. Those standard features (like DDC) should in theory allow your system to figure out and select the ideal settings, but in practice this very much depends on the combination of hardware.

   Here is an overview of different video display resolution standards and de-facto standards in use (not all of them used in PCs):

Computer Standard	Resolution
VGA	640 x 480 (4:3)
SVGA	800 x 600 (4:3)
XGA	1024 x 768 (4:3)
WXGA	1280 x 768 (15:9)
SXGA	1280 x 1024 (5:4)
SXGA+	1400 x 1050 (4:3)
WSXGA	1680 x 1050 (16:10)
UXGA	1600 x 1200 (4:3)
UXGAW	1900 x 1200 (1.58:1)
QXGA	2048 x 1536 (4:3)
QVGA (quarter VGA)	320 x 240 (4:3)
Analogue TV Standard	Resolution
PAL	720 x 576
PAL VHS	320 x 576 (approx.)
NTSC	640 x 482
NTSC VHS	320 x 482 (approx.)
Digital TV Standard	Resolution
NTSC (preferred format)	648 x 486
D-1 NTSC	720 x 486
D-1 NTSC (square pixels)	720 x 540
PAL	720 x 486
D-1 PAL	720 x 576
D-1 PAL (square pixels)	768 x 576
HDTV	1920 x 1080
Digital Film Standard	Resolution
Academy standard	2048 x 1536

    In the late 1980s concern over possible health issues related to monitor use were raised. In  Sweden this resulted a standard MPR1 to be developed. This was amended in 1990 to the internationally adopted MPR2 standard, which called for the reduction of electrostatic emissions with a conductive coating on the monitor screen. In 1992 a further stricter standard, entitled TCO (TCO92), was introduced by the Swedish Confederation of Professional Employees. Other relevant monitor safety standards include: ISO 9241 part 3 (the international standard for monitor ergonomics), EN60950 (the European standard for the electrical safety of IT equipment) and the German TUV/EG mark (monitor has been tested to ISO 9241 part 3, EN60950, MPR2 and German standard for basic ergonomics ZH/618). TCP99 is the latest iteration of the standard TCO99 give regulations on screen refresh rates. To reduce eye fatigue caused by image flicker, the minimum required refresh rate is increased to 85Hz for displays of less than 20in, with 100MHz recommended, and to a minimum of 75Hz for 20in or greater.

    Power consumed by the monitor can also be a significant figure. In 1993, VESA initiated its DPMS standard, or Display Power Management Signaling, which allowed a DPMS compliant graphics card to turn the monitor to standby more or suspend modes which consume considerably less power than normal operation. EPA Energy Star is a power saving standard, mandatory in the US and widely adopted in Europe, requiring a mains power saving mode drawing less than 30W. In 1995, TCO was expanded with a range of conditions to cover environmental issues. TCO95 became the first global environmental labeling scheme. Over and above TCO92, the product may not contain cadmium or lead, the plastic housing must be of biodegradable material and free of brominated flame retardants and the production process must avoid use of CFCs (freons) and chlorinated solvents.

Monitor interfaces

Analogue VGA interface

    Modern PC graphics cards even nowadays still use the old 15 pin VGA connector (known ad HD15 connector). The connector carries the video signal in RGB format. The sync information is carried through separate horizontal and vertical sync signal wires. This whole video signal format (video and sync) is generally referred as RGBHV signal format.The signal levels in RED, GREEN and BLUE signal are 0.7V peak to peak video signals terminated to 75 ohm load in video card and monitor ends. All other signals are TTL level signal (around 0..0.7V means logic 0 and 3..5V means logic 1). Analogue video signals are carried through 75 ohm coaxial conductors. The video signal carried vy VGA connector can also be carried with separate 5 coaxial cables with BNC connectors (some monitors and video projectors use this kind of interface and adapter cables for this are readily available). The pin-out of video signals on VGA connector:

• 1 Red Video
• 2 Green Video
• 3 Blue Video
• 4
• 5
• 6 Red Return (ground)
• 7 Green Return (ground)
• 8 Blue Return (ground)             
• 9
• 10 Sync Return (ground)
• 11
• 12
• 13 Horizontal Sync
• 14 Vertical Sync
• 15

     In addition to video signal, the VGA connector has some monitor identification pins (pins 11, 12 and 15) that allow PC video cards to determine what type of monitor is connected to the graphics card. The original plan used to such that the monitors grounded some of those pins to tell that the monitor is there and what type of monitor is there. Modern plug&play monitor systems have changed their use in such way that pins 11 and 15 are used for DCC data communications between computer and monitor (pin 12 = DDC DATA, pin 15 = DCC Clock). The extra control signals are generally carried through separate wires (all inside one cable main shield). Pin 5 is sometimes referred as GND TEST and sometimes just ground.Pins 4 and 9 are not generally used. Not all connector pins are used in VGA cables. Generally pins 9 has been removed because is is used in many devices as key to stop plugging in full 15 pin connectors. In some scales also pin 15 have been removed for compatibility with all VGA computers (also older ones, because pins 9 and 12 pins were removed in early VGA cables and blocked in old VGA cards).Here is one common wiring used:

Pin New VESA DDC     Old VGA
1   Red              Red 
2   Green            Green
3   Blue                Blue
4   No Connect       Reserved
5   Ground           Ground
6   Ground           Red Ground 
7   Ground           Green Ground
8   Ground           Blue Ground
9   No Connect       No connect
10  Ground           Ground for syncs
11  No Connect       Monitor ID 0 (ground)
12  DDC DAT          Monitor ID 1 (no connect)
13  Horizontal Sync   Horizontal Sync
14  Vertical Sync    Vertical Sync
15  DDC Clock        No Connect

    The video signals carried in VGA connector are designed to be matched to 75 ohm load and use coaxial cable. At least the RGB signals on the cable used to connect VGA signals must have 75 ohm coaxial construction to guarantee good quality high resolution image. A typical high quality VGA monitor cable or VGA extension cable has three three 75 ohm mini coax cables to carry RGB signals and 9 other wires (typically 24 AWG) to carry other signals like syncs and monitor identification. The whole cable has a good metallic shield around all of those wires. Some very high quality cables use five 75 ohm coaxial cables and for RGBHV signals and just few extra wires. In applications where monitor ID signals are not needed, just five 75 ohm coaxes are used to transfer VGA signals. Typical features of flexible mini coax cables (from http://www.drakausa.com/pdfsHHT/AVprcise.pdf for extra flexible miniature coax):

1 MHz:   0.6 dB/100ft
5 MHz:   1.3 dB/100ft
10 MHz:   1.8 dB/100ft
30 MHz:  10.2 dB/100ft
100 MHz:  17.1 dB/100ft

Some attenuation figures of high quality VGA extension cable (for reference of typical features):

10 MHz:  1.6 dB/100ft
50 MHz:  4.0 dB/100ft
100 MHz:  6.1 dB/100ft
200 MHz:  9.8 dB/100ft
300 MHz: 13.0 dB/100ft
400 MHz: 15.9 dB/100ft

    The connector uses in VGA connections is HD 15 connector. This ubiquitous connector is convenient, low cost, and most importantly, adopted by IBM, but technically not the best possible connector. The connector was originally selected to be good enough for the signals existing in the early days of VGA interface and was more than good enough for this use, but VGA connector has it's limitations at high resolutions. Does anyone know the impedance of a 15-pin VGA connector? Unfortunately the HD15 connector used does not match to 75 ohm impedance (in reality the impedance of a typical VGA connection is about 100 ohms). Even though the connector impedance is not exactly right, the primary issue centers on the limited length of the connector interface, so it does not significantly hamper performance in systems we most often deal with.This HD15 connector is still used, because this ubiquitous connector is convenient, low cost, and most importantly, adopted by IBM. It is still with the limitations considered "good enough". And in practice one VGA connector on the route from the graphics card to the monitor does not cause too much problems for picture quality. The primary issue for this centers on the limited length of the connector interface. Because of the limited length, it does not significantly hamper performance in systems we most often deal with. Because there is no no significant effects, hence the popularity of the VGA connector as a low-cost, general interface for the PC even nowadays. The problems of connector impedance mismatch becomes visible if you happen to have more than one VGA connector on the route to monitor and you run high frequency video signal (high resolution at high refresh rate). Impedance mismatch degrades the picture quality. You can see the impedance matching problems usually when you use devices like VGA monitor switch boxes, VGA extension cables etc.

Digital Visual Interface (DVI)

     Digital Visual Interface (DVI) is the standard interface for high-performance connection between PCs and Flat Panel Displays, Digital CRT Displays, Projectors, and HDTV. DVI Cables deliver the high-performance, high-bandwidth interface needed for video displays of today, and leaving headroom for the products of tomorrow. 

    DVI standard is defined by DDWG (Digital Display Working Group). DVI most commonly used digital video interface with PCs in DVI. It comes in these version: DVI-A, DVI-D and DVI-I. The difference on those is that DVI-D support only digital signals, where DVI-I includes both digital and analogue video signals (analogue signals are same as used by VGA interface). DVI supports hot plugging of DVI display devices.

    DVI-A format is used to carry a DVI signal to an analogue display, such as a CRT monitor or an HDTV. Basically this interface has same signal as VGA connector has, but uses different shape connector. DVI-A can transmit a higher quality picture than standard VGA, because the connector user matches better to the needs of transported high frequency video signal than the old 15-pin VGA connector.

   DVI-D is a digital only connector version of DVI interface. DVI-D is the leading connector standard for digital only connection. It comes in two flavors: Single Link and Dual Link. The primary difference between Single Link and Dual link is that each supports varying resolution levels. DVI-D uses LVDS signaling for digital signal and supports cable length up to 5 meters (longer distances are possible with repeaters every 5 meters). In case of longer transmission distances are needed, you need to either have DVI repeater every 5 meters or use a special converter that converts DVI signals to fiber optics and back. Some manufacturers seem to make also 10 meters long DVI-D cables, but because those are longer than standard permits their operation is no guaranteed (causes unreliable operation and signal transmission errors on many equipment, but can work on some equipment). The DVI-D Single Link supports resolutions up to 1920x1080. For gher resolution there is a dual link version also available.

    Within the DVI system, parallel data from the computer graphic memory is serialized (similar to digital television) and transmitted differentially over a minimum of four twisted pair wires:a red channel, green channel, blue channel, and clock channel at about 165 mega-pixels/second per channel (1.65 Gbps on the basic system). The RGB data are not simply serialized and dumped onto the cables. Encoded sync information is carried along and the data is scrambled using a specific routine that minimizes errors during transmission from source to destination. The system operates on 3.3 volts and can operate at lower voltages. The twisted pair differential swing is about 1.0 volt peak-to-peak.

    The DVD-D dual link configuration provides enough bandwidth for resolutions up to 2048 x 1536, and is designed for digital use only. In dual link system the number of wires used to transport red, green and blue component data is doubled (giving total 7 pairs of wire used to transport data). The DVD-D dual link uses DVI-D 24-pin connectors and supports digital signal only. To support those high resolutions, very high data rates are needed in the cable. DVI achieves up to 9.9-Gbps dual-link or 4.95-Gbps single-link data speeds.

DVI-I format is an integrated cable which is capable of transmitting either a digital-to-digital signal or an analog-to-analog signal.DVI-I can supports both digital DVI-D signals AND analog (RGB). The connector has a few more pins than digital only DVI-D. Many graphics cards manufacturers are offering this connector type on their products, so this can be connected to either digital or analogue display device. The signals from DVI-I connector can be adapted to analogue VGA signal by using a simple connector adapter (usually comes with graphics card, can be bought separately). DVI-I format is an integrated cable which is capable of transmitting either a digital-to-digital signal or an analog-to-analog signal. Make sure that you know what format each part of your equipment is before you purchase any DVI cables. Only equipment with a DVI port labeled 'DVI-I' will accept both a DVI-D and DVI-A source signal.

    Determining which type of cable to use for your DVI products is critical in getting the right product the first time. Check both of the female DVI plugs to determine what signals they are compatible with. There are two variables in every DVI connector cable, and each represents one characteristic. The flat pin on one side denotes whether the cable is digital or analog: a flat pin with four surrounding pins is either DVI-I or DVI-A, a flat pin alone denotes DVI-D. The pin sets vary depending on whether or not the cable is single- or dual-link: a solid 27-pin set (rows of 8) for a dual- link cable,two separated 9-pin sets (rows of 6) for a single-link cable. Note: To prevent pins being broken off of mismatched cables, most manufacturers will make their female plugs with all available pins. This means that most every female DVI plug will look like a DVI-I, but this is not necessarily true. Be sure to look for a label, or check the product documentation to make sure you know what type it is.

The physical cable used to do DVI connection has different conductor types depending on the signal they carry. The digital signals are carried through twisted pairs that have 100 ohm +/- 15% impedance (usually separately shielded twisted pairs). Analogue video signals are carried through 75 ohm coaxial conductors.

   Transmission of the TMDS (transition minimized differential signaling) format combines four differential, high-speed serial connections (in its base configuration) transmitted in a parallel bundle. When the DVI specification is extended to the dual mode operation, greater data rates for higher display resolutions are possible, but now there are seven parallel differential, high-speed pairs. Cabling and connection become extremely important. The DVI cable and its termination is very important. The physical parameters of the twisted pairs must be highly controlled. Specifications for the cable and the receiver are given in fractions of bit transmission time, so the requirements depend on the clock rate or signal resolution being used. Transferring the maximum rate (1600 x 1200 at 60 Hz) for a single link system means that one bit time (10 bits per pixel) is 0.1 (1/165 MHz), which is only 0.606 nanoseconds. Ten bit times describe one pixel in this system. The DVI receiver specification allows only 0.40 x bit time, or about 0.242 nanoseconds intra-pair skew (within the twisted pair). A cable for DVI-D should be evaluated on its insertion loss for a given length. The DVI transmitter output eye pattern is specified into a nominal cable impedance of 100 ohms. A normal signal swings +780 mV to -780 mV. The minimum positive signal swing is +200 mV and the minimum negative swing is -200 mV (total swing of 400 mV). When the signals are combined in the differential receiver, the resulting signal level is two times the swing value. But, for the cable situation, we must assume minimum performance on the transmitter side and best sensitivity on the receiver end. The receiver must operate on signals as low as +75 mV to -75 mV, or a total swing of 150 mV. This means that under worst-case conditions, the cable attenuation can be no more than 8.5dB at 1.65 GHz (10 bits/pixel times 165 MHz clock). As you can imagine, maintaining this type of performance on twisted pair wires is relatively difficult. The nominal DVI cable length limit is 4.6 meters (about 15 feet). Electrical performance requirements are similar to serial digital. Signal rise time (0.330 nanoseconds), cable impedance (100 ohms), far end crosstalk (FEXT) of no more than 5%, and signal rise time degradation (160 picoseconds maximum) are the key parameters highlighted in the DVI specification regarding the physical connection.

      Cable for DVI is application specific because maintaining these specifications is no easy feat since the actual bit rate per channel is 1.65 Gbps. And, we're talking twisted pair cable here. Upgrade your system's video performance by connecting VGA- or DFP-configured monitors to fast DVI cables.Use DVI to eliminate resolution or color changes and pixel-lock adjustments in laptop-to-projector connections, too.

29 pin DVI Connector PinOut and Signal Names

Pin #	Signal Name	Pin #	Signal Name	Pin #	Signal Name
1	TMDS Data2-	9	TMDS Data1-	17	TMDS Data0-
2	TMDS Data2+	10	TMDS Data1+	18	TMDSData0+
3	TMDS Data2/4 Shield	11	TMDS Data1/3 Shield	19	TMDS Data0 Shield
4	TMDS Data4-	12	TMDS Data3-	20	TMDS Data5-
5	TMDS Data4+	13	TMDS Data3+	21	TMDS Data5+
6	DDC Clock [SCL]	14	+5 V Power	22	TMDS Clock Shield
7	DDC Data [SDA]	15	Ground (for +5 V)	23	TMDS Clock +
8	Analog vertical sync	16	Hot Plug Detect	24	TMDS Clock -
C1	Analog Red	--	--	--	--
C2	Analog Green	--	--	--	--
C3	Analog Blue	--	--	--	--
C4	Analog Horizontal Sync	--	--	--	--
C5	Analog GND Return: (analog R, G, B)	--	--	--	--

Connecting a Monitor/Projector to Your Laptop

• Getting Set Up

    Advancements in processors, other hardware, and operating systems (OSs) now make multitasking easier than ever. A typical computer session may include browsing the Web while downloading music, or editing a photo while virus scan runs in the background. For example, Intel's latest mobile processors allow laptop users to simultaneously run multiple, resource-intensive programs while consuming very little power.

Because of the increase in energy efficiency and performance, laptops in general have become smaller, thinner, and lighter. Most new models come equipped with dual monitor support and accelerated video technology, making connecting an additional monitor a simple operation. 

Why use a second monitor?

   Dual monitor configurations make complex projects easier to work on. Graphic designers, for example, often have several editing programs running at the same time. Adding an additional monitor doubles visual "real estate," giving users more room to work and play. Your desktop view can either be replicated on the second screen or stretched across it to form a larger work area.

Smaller laptop screens are great for traveling, but can be hard on your eyes for extended use. Connecting a full-size monitor to your laptop computer allows you to choose screen resolutions and refresh rates that cause less eye strain.

Whether you plan to make a presentation, are working on a massive project or your laptop screen suddenly stops working, learning how to connect a monitor to your laptop can save you a lot of time and frustration.

Connect a monitor to your laptop

    Laptops usually have one or more digital visual interface (DVI), video graphics array (VGA), or separate video (S-Video) ports. DVI ports are used to connect some flat panel LCD displays, while VGA ports can connect either LCD or older style CRT monitors. In addition to monitors, S-Video ports can also be used to connect video cameras, DVD players, and TVs.

If you have an older laptop that does not have a monitor port, you can purchase a USB 2.0-to-SVGA video adapter. The adapter plugs into one of your USB 2.0 ports. With it, one or more LCD or CRT monitors can be connected to your computer. They are reasonably priced and can be found online or through your local computer dealer.

Let's get started.

• Shut down your laptop and unplug it. Set the monitor next to the laptop on a secure surface.
• Determine which type of connector your monitor has and plug it into the corresponding port on the back or side of your laptop. DVI ports are usually white, and most VGA ports are blue (refer to your laptop owner's manual if necessary). If your monitor uses a different connector than what is available on your laptop, you can get an adapter to make them work. Tighten the connector screws, and then turn on the monitor.
• Plug your laptop in and turn it on. If the monitor does not show your OS loading, go to the next step.
• On your laptop keyboard, locate the FN key and the display function key (typically F5, F7 or F8), which usually has a picture of a monitor or the words CRT/LCD on it. To activate the monitor display, hold down the FN key, then press the display function key. It may take a few seconds for the monitor to respond. Refer to your laptop owner's manual if you have trouble locating or using the display function key.

Configure the screens

    Most laptops mirror your desktop on the second monitor by default. By changing a few settings, you can extend your desktop across both monitors, allowing you to drag open programs from one screen to the other.

In Windows Vista*:

• Right-click on your desktop and select "Personalize" then "Display Settings."
• Arrange the two virtual monitor displays by dragging the boxes to correspond to the location of your actual monitors. For example, if your laptop is located on the left of the monitor, drag the two boxes so that Monitor 1 is on the left and Monitor 2 is on the right.
• Select the additional monitor from the drop-down menu, check the box beside "Extend the desktop onto this monitor" then click "Apply."
In Windows XP*:
• Right-click on your desktop, then select "Properties." In the Display Properties dialog box, click the "Settings" tab.
• Arrange the virtual monitor displays if necessary. Select the additional monitor, check "Extend my Windows desktop," then click "OK".
Connecting a monitor to your laptop is that easy. Other OSs such as Linux use slightly different software configurations, but they are very similar overall. Experiment with different settings and monitor combinations to get the most out of your new dual-screen workstation.

Computer Maintenance

• Productivity Tips

    Your Windows*-based computer needs a small amount of regular attention to keep it running its best. Performing the tasks listed here (some can even be scheduled to take place automatically) will help you maintain your machine's performance.

Microsoft Update: the easiest critical maintenance you'll ever do.

    Software manufacturers are constantly on the lookout for problems ranging from bugs to security issues with their products. When they identify a problem, their programmers produce a software update that corrects it. Microsoft has made it simple to get these updates to you using the Windows Update and Microsoft Update services. (Windows* Update provides updates for only Windows, while Microsoft* Update gives you updates to other Microsoft software, like Microsoft Office*.)

 

    A new Windows computer is set to download critical updates (the ones that solve big functionality and security problems) automatically. If you want to change the automatic setting or manually check for updates, from the Start menu, click Windows Update or Microsoft Update, and then follow the on-screen instructions.

Disk cleanup: like housecleaning for your hard drive.

   Over time, your computer collects junk, just like an overstuffed closet. And just like a closet, you can take back some of that space if you clean up your hard drive once in a while. Windows makes it easy with Disk Cleanup. To start the tool, from the Start menu, just click Programs, Accessories, System Tools, and then Disk Cleanup. The dialog box that appears will list several types of files you can delete to free up space on your hard drive.

    Select the appropriate checkboxes, and then click OK. This could take a while (maybe ten minutes or more) depending on what you select, but Windows will do the rest for you.

Defragment your hard drive: make things easier for your processor.

   Your computer constantly stores and deletes files on your hard drive. Over time this process can become disorganized, with files divided up into smaller and smaller chunks that are saved all over the place. To understand how this works, consider this example.

    The Windows Disk Defragmenter tool reorganizes all of your files so the chunks are put back together and the machine can run faster again. Running this tool is strictly manual in Windows XP*, but you can schedule it to run automatically in Windows Vista*. In either case, to launch the tool: from the Start menu, click Programs, Accessories, System Tools, and then Disk Defragmenter.

• Say you delete a file on your computer that's five kilobytes (5 KB), leaving a 5 KB chunk of empty hard drive space.
• Later, you save a 10 KB file. The computer wants to store that file in the 5 KB space it just freed up on the hard drive. It will save 5 KB of the file in that space, but if there is no empty space adjacent to that location, the computer will find somewhere else to put the other 5 KB.
• The file you just saved now exists on the hard drive as two 5 KB "fragments." That's OK, but over time, more and more files are divided into more and more fragments.
• When you open one of these files, the computer must gather the fragments from all over the hard disk, which forces the processor to work harder. Unfortunately, this additional work means your computer will work more slowly.

Windows Vista*: You can either run Disk Defragmenter with the Defragment now button or schedule defragmentation by clicking the Modify schedule button.

Windows XP*: To find out how fragmented the drives are, click the Analyze button. To defragment them, click the Defragment button.

Protecting Your Computer from Viruses

• System Health

    As everyone who has ever had the flu knows, viruses can be devastating—and computers don't get off any easier than people. Even though a flu virus and a computer virus have obvious differences, there are some similarities: Both you and your computer get viruses from others who are already infected, and prevention can help keep both of you healthy.

Keep in mind that the steps listed in this article are only recommendations that may help prevent virus infection and help deal with it if one does occur. This topic is complex, and it changes rapidly, so it's important to stay vigilant and stay informed.

Prevention is the key.

    Your best defense is to keep your system from getting infected in the first place because once it is, it can be very difficult, if not impossible, to get rid of the virus. The road to prevention begins with these steps:

• Install effective anti-virus software. Anti-virus software is widely available; any online or brick-and-mortar store that sells software will offer a number of products. These products typically require an annual subscription, which lets you keep your anti-virus software up to date and ready to detect the latest threats.
  Tip: For added protection, consider buying a security suite that includes firewall software and other protection (such as spam filtering).
  
• Avoid risky behavior. For example: never open an email attachment that comes from someone you don't know, and avoid downloading anything from the Internet that might not be trustworthy. Keep in mind that humorous material is often passed along, from address to address, through email. It's best not to open this type of file, because even if the attachment is from someone you know, they may be unknowingly passing along a virus.

Make regular virus scans a habit.

    Anti-virus software typically lets you choose whether to schedule a scan on a regular basis or perform a manual scan. Because a full scan can take an hour or more to complete, many anti-virus software packages also let you perform a quick, but less thorough, scan of the most commonly infected parts of the computer. See your product documentation for details.

Tip: While you shouldn't depend on it for your main anti-virus solution, another option is to use a free online service to scan your computer, like Trend Micro HouseCall* or Symantec Security Check*.

You've discovered an infection. Now what?

If you discover a virus or related threat during a scan, follow these steps:

• Follow your anti-virus software's on-screen instructions. Many viruses can be easily removed using this method. Another option for Windows-based systems is to use the Microsoft Windows Malicious Software Removal Tool*, free software distributed through Windows Update* and updated monthly. Re-scan your computer after you've removed the virus (just to be sure).
  Tip: It's also a good idea to scan again with a separate scanner, such as an online service, for added assurance.
• Contact an expert. If first efforts aren't enough, check your anti-virus product's Web site for additional information. Sometimes—especially for high-profile threats—major anti-virus software manufacturers will provide a tool to help get rid of specific viruses. However, these tools can be complicated to use, so depending on how comfortable you are with the procedure, you might want to bring in an expert. Many large retail chains now provide in-store services that specialize in removing viruses. The cost involved can be a small amount to pay to resolve the problem.
• Use restore disks or re-install the operating system. A new computer often comes with a set of one or more emergency "restore" disks. If you haven't been able to remove the virus, this set of disks might help you to resolve the problem. However, you will lose any files that haven't been backed up on separate media. Although many anti-virus programs let you make a set of emergency restore disks when you install the software. Similarly, if your computer came with a set of one or more operating system disks, you can re-install the operating system and return the computer to factory condition. These options are strong medicine, but if everything else fails, they may be the only way to restore your computer's health.

Keeping virus-free

• Install anti-virus software and keep it up to date
• Don't open suspicious email attachments or download untrustworthy Internet content
• Set Windows Update to automatic mode
• Use firewall software

What is DLP Projector?

    Digital Light Processing (DLP) is a trademark owned by Texas Instruments, representing a technology used in some TVs and video projectors. It was originally developed in 1987 by Dr. Larry Hornbeck of Texas Instruments.

DLP is used in DLP front projectors (small standalone projection units) and DLP rear projection television.

   DLP, along with LCD and LCoS, are the current display technologies behind rear-projection television, having supplanted CRT rear projectors. These rear-projection technologies compete against LCD and plasma flat panel displays in the HDTV market.

The single-chip version of DLP and 3LCD are the two main technologies used in modern color digital projectors, with the two technologies being used in over 95% of the projectors sold in 2008.

   DLP is also one of the leading technologies used in digital cinema projection.

In March 2008, TI announced the initial production of the DPP1500 chipset, which are micro projectors to be used in mobile devices. Availability for final products would show up in the market early 2009.

  

Digital micromirror device

   In DLP projectors, the image is created by microscopically small mirrors laid out in a matrix on a semiconductor chip, known as a Digital Micromirror Device (DMD). Each mirror represents one or more pixels in the projected image. The number of mirrors corresponds to the resolution of the projected image (often half as many mirrors as the advertised resolution due to wobulation). 800x600, 1024x768, 1280x720, and 1920x1080 (HDTV) matrices are some common DMD sizes. These mirrors can be repositioned rapidly to reflect light either through the lens or on to a heat sink (called a light dump in Barco terminology). Rapidly toggling the mirror between these two orientations (essentially on and off) produces grayscales, controlled by the ratio of on-time to off-time.

  

Color in DLP projection

   There are two primary methods by which DLP projection systems create a color image, those utilized by single-chip DLP projectors, and those used by three-chip projectors. A third method, sequential illumination by three colored light emitting diodes, is being developed, and is currently used in televisions manufactured by Samsung. Yet another method, color LASERs, is currently in use by Mitsubishi in their LASERVUE products.

Single-chip projectors

 In a projector with a single DLP chip, colors are produced either by placing a color wheel between a white lamp and the DLP chip or by using individual light sources to produce the primary colors, LEDs or LASERs for example. The color wheel is divided into multiple sectors: the primary colors: red, green, and blue, and in many cases secondary colors including cyan, magenta, yellow and white. The use of the secondary colors is part of the new color performance system called BrilliantColor which processes the primary colors along with the secondary colors to create a broader spectrum of possible color combinations on the screen.

The DLP chip is synchronized with the rotating motion of the color wheel so that the green component is displayed on the DMD when the green section of the color wheel is in front of the lamp. The same is true for the red, blue and other sections. The colors are thus displayed sequentially at a sufficiently high rate that the observer sees a composite "full color" image. In early models, this was one rotation per frame. Now, most systems operate at up to 10x the frame rate.

 

The color wheel "rainbow effect"

DLP projectors utilizing a mechanical spinning color wheel may exhibit an anomaly known as the “rainbow effect.” This is best described as brief flashes of perceived red, blue, and green "shadows" observed most often when the projected content features high contrast areas of moving bright/white objects on a mostly dark/black background. The scrolling end credits of many movies are a common example, and also in animations where moving objects are surrounded by a thick black outline. Brief visible separation of the colours can also be apparent when the viewer moves their eyes quickly across the projected image. Some people perceive these rainbow artifacts frequently, while others may never see them at all.

This effect is caused by the way the eye follows a moving object on the projection. When an object on the screen moves, the eye will follow the object with a constant motion, but the projector will display each alternating color of the frame at the same location, for the duration of the whole frame. So, while the eye is moving, it will see a frame of a specific color (red for example). Then, when the next color is displayed (green for example), although it gets displayed at the same location overlapping the previous color, the eye will have moved toward the object's next frame target. Thus, the eye will see that specific frame color slightly shifted. Then, the third color gets displayed (blue for example), and the eye will see that frame's color slightly shifted again. This effect is not perceived only for the moving object, but the whole picture.

The effect varies with the rotational speed of the color wheel and the frame refresh rate of the video signal. There is a maximum rotational speed limit for the wheel, typically 10,000 to 15,000 RPM. Video framerate is usually measured in frames per second and must be multiplied by 60 to find the wheel speed, whereas 60 frames/sec equals 3,600 frames/minute. If the color wheel spins 4 times per frame, it is rotating at a speed of 14,400 RPM. (Projector specifications often list the wheel speed at specific framerates as 2x, 3x, 4x, etc.)Increasing the video refresh rate to 85 frames per second does not necessarily further reduce the rainbow effect since this rate would increase the wheel speed to 20,400 RPM, potentially exceeding the safe limits of wheel rotation and requiring the projector to drop back to 3x speed, at 15,300 RPM.

Multi-color LED-based and LASER-based single-chip projectors are able to eliminate the spinning wheel and minimize the rainbow effect since the pulse rate of LEDs and LASERs are not limited by physical motion.

 Three-chip projectors

   A three-chip DLP projector uses a prism to split light from the lamp, and each primary color of light is then routed to its own DLP chip, then recombined and routed out through the lens. Three chip systems are found in higher-end home theater projectors, large venue projectors and DLP Cinema projection systems found in digital movie theaters.

    According to DLP.com, the three-chip projectors used in movie theaters can produce 35 trillion colors, which many suggest is more than the human eye can detect. The human eye is suggested to be able to detect around 16 million colors, which is theoretically possible with the single chip solution. However, this high color precision does not mean that three-chip DLP projectors are capable of displaying the entire gamut of colors we can distinguish (this is fundamentally impossible with any system composing colors by adding three constant base colors). In contrast, it is the one-chip DLP projectors that have the advantage of allowing any number of primary colors in a sufficiently fast color filter wheel, and so the possibility of improved color gamuts is available.

Light source

   The main light source used on DLP-based rear screen projection TVs is based on a replaceable high-pressure mercury-vapor metal halide arc lamp unit (containing a quartz arc tube, reflector, electrical connections, and sometimes a quartz/glass shield), while in some newer DLP projectors high-power LEDs or LASERs are used as a source of illumination.

Metal-halide lamps

   For metal-halide lamps, during start-up, the lamp is ignited by a 5000 volt pulse from a current-regulating ballast to initiate an arc between two electrodes in the quartz tube. After warmup, the ballast's output voltage drops to approximately 60 volts while keeping the relative current high. As the lamp ages, the arc tube's electrodes wear out and light output declines somewhat while waste heating of the lamp increases. The mercury lamp's end of life is typically indicated via an LED on the unit or an onscreen text warning, necessitating replacement of the lamp unit.

    Older projectors would simply give a warning that the lamp life had expired but would continue to operate. Newer projectors will not power up until the lamp is replaced and the lamp hours are reset. Most devices include a lamp hours reset function for when a new lamp is installed, but it is possible to reset a projector to continue to use an old lamp past its rated lifespan.

   When a metal-halide lamp is operated past its rated lifespan, the efficiency declines significantly, the lightcast may become uneven, and the lamp starts to operate extremely hot, to the point that the power wires can melt off the lamp terminals. Eventually, the required startup voltage will also rise to the point where ignition can no longer occur. Secondary protections such as a temperature monitor may shut down the projector, but a thermally overstressed quartz arc tube can also crack and/or explode, releasing a cloud of hot mercury vapor inside and around the projector. However, practically all lamp housings contain heat-resistant barriers (in addition to those on the lamp unit itself) to prevent the red-hot quartz fragments from leaving the area.

LED-based DLPs

    The first commercially-available LED-based DLP HDTV was the Samsung HL-S5679W in 2006, which also eliminated the use of color wheel. Besides long lifetime eliminating the need for lamp replacement and elimination of the color wheel, other advantages of LED illumination include instant-on operation and improved color, with increased color saturation and improved color gamut to over 140% of the NTSC color gamut. Samsung expanded the LED model line-up in 2007 with products available in 50", 56" and 61" screen sizes. For spring 2008, the third generation of Samsung LED DLP products are available in 61" (HL61A750) and 67" (HL67A750) screen sizes.

   Ordinary LED technology does not produce the intensity and high lumen output characteristics required to replace arc lamps. The special patented LEDs used in all of the Samsung DLP TVs are PhlatLight LEDs, designed and manufactured by US based Luminus Devices. A single RGB PhlatLight LED chipset illuminates these projection TVs. The PhlatLight LEDs are also used in a new class of ultra-compact DLP front projector commonly referred to as a "pocket projector" and have been introduced in new models from LG Electronics (HS101), Samsung electronics (SP-P400) and Casio (XJ-A series). Home Theater projectors will be the next category of DLP projectors that will use PhlatLight LED technology. At InfoComm, June 2008 Luminus and TI announced their collaboration on using their technology on home theater and business projectors and demonstrated a prototype PhlatLight LED based DLP home theater front projector. They also announced products will be available in the marketplace later in 2008 from Optoma and other companies to be named later in the year.

LASER-based DLPs

    The first commercially-available LASER-based DLP HDTV was the Mitsubishi L65-A90 LASERVUE in 2008, which also eliminated the use of a color wheel. Three separate color LASERs illuminate the digital micromirror device (DMD) in these projection TVs, producing a richer, more vibrant color palette than other methods. See the laser video display article for more information.

 Digital cinema

    DLP is the current market-share leader in professional digital movie projection, largely because of its high contrast ratio and available resolution as compared to other digital front-projection technologies. As of December 2008, there are over 6,000 DLP-based Digital Cinema Systems installed worldwide.

DLP projectors are also used in RealD Cinema for 3-D films.

Manufacturers and market place

   Texas Instruments remains the primary manufacturer of DLP technology, which is used by many licensees who market products based on T.I.'s chipsets. The Fraunhofer Institute of Dresden, Germany, also manufactures Digital Light Processors, termed Spatial Light Modulators, for use in specialized applications. For example, Micronic Laser Systems of Sweden utilizes Fraunhofer's SLMs to generate deep-ultraviolet imaging in its Sigma line of silicon mask lithography writers.

    DLP technology has quickly gained market share in the front projection market and now holds roughly 50% of the worldwide share in front projection. Over 30 manufacturers use the DLP chipset to power their projectors.

 Pros

• Smooth (at 1080p resolution), jitter-free images.
• Perfect geometry and excellent grayscale linearity achievable.
• Usually great ANSI contrast.
• No possibility of screen burn-in.
• Less "screen-door effect" than with LCD projectors.
• DLP rear projection TVs generally have a smaller form factor than comparable CRT projectors.
• DLP rear projection TVs are considerably cheaper than LCD or plasma flat-panel displays and can still offer 1080p resolution.
• The use of a replaceable light source means a potentially longer life than CRTs and plasma displays (this may also be a con as listed below).
• The light source is more-easily replaceable than the backlights used with LCDs, and on DLPs is often user-replaceable.
• New LED and LASER DLP TVs and projectors eliminate the need for lamp replacement.
• Using two projectors, one can project full color stereoscopic images using polarized process (because beams can be polarized).
• Lighter weight than LCD and plasma televisions.
• Unlike their LCD and plasma counterparts, DLP screens do not rely on fluids as their projection medium and are therefore not limited in size by their inherent mirror mechanisms, making them ideal for increasingly larger high-definition theater and venue screens.
• DLP Projectors can process up to 7 separate colors giving them strong color performance
• DLP projectors do not suffer from “Color Decay” often seen with LCD projectors in which the image on the screen turns yellow after extended periods of usage.

 Cons

• Some viewers are bothered by the "rainbow effect," explained above.
• Not as thin as LCD or plasma flat-panel displays (although approximately comparable in weight), although some models as of 2008 are becoming wall-mountable (while still being 10" to 14" thick)
• Replacement of the lamp / light bulb. The average life span of a TV light source averages 2000-5000 hours and the replacement cost for these range from $99 – $350, depending on the brand and model. After replacing the bulb a few times the cost can easily exceed the original purchase price of the television itself. Newer generations units use LEDs or LASERs which effectively eliminates this issue, although replacement LED chips could potentially be required over the extended lifespan of the television.
• Some devices may have fan noise.
• Dithering noise may be noticeable, especially in dark image areas. Newer (post ~2004) chip generations have less noise than older ones.
• Error-diffusion artifacts caused by averaging a shade over different pixels, since one pixel cannot render the shade exactly.
• Response time in video games may be affected by upscaling lag. While all HDTVs have some lag when upscaling lower resolution input to their native resolution, DLPs are commonly reported to have longer delays. Newer consoles such as the Xbox 360 do not have this problem as long as they are connected with HD-capable cables.
• Reduced viewing angle as compared to direct-view technologies such as CRT, plasma, and LCD.