Visual Display Unit

The primary disadvantage to the usage of dual monitors is that the resources of the video card are effectively halved when the second display device is connected. The decreased processing power and VRAM available to each display may lead to unacceptable performance on both devices. In this case, the second display device may be connected to an additional video adapter installed in the computer allowing the full processing and VRAM capability for each device. Thus, as newer and more powerful graphics cards are introduced, this problem is not so much of an issue.

Full-screen software also poses a problem on multi-monitor PCs. A large amount of full-screen applications makes use of the absolute edge of the display to control view movement. Unfortunately, this software generally does not work properly on a multi-monitor PC unless the software specifically was designed to be multi-monitor aware.

You can often find “edge-scrolling” in full-screen image viewers, 3D model editors, and RTS (RealTime Strategy) genre video games.

Despite that the use of multi-monitor PCs is steadily growing, there still are significantly more single monitor PC users out there. As a result of this vast majority of single display users, software developers often see adding multi-display support to their titles as a low priority (since so little of their potential market-base uses multi-display systems). This will likely change someday as the percent of multi-monitor PC users increases, yet at present multi monitor computing is still fairly limited in the home consumer market.

The problem that full-screen applications present is that they generally only cover one of the displays on a multi-monitor computer. Edge-scrolling still works in these applications if you position the mouse cursor on the absolute edge of the screen, yet this is often impractical and hard to do. The reason that you cannot easily position the mouse on the absolute edge is simple; the desktop space on a multi-monitor PC is not limited to just that display. Instead of the mouse cursor stopping at the screen’s edge (where the software developers assumed that it would), the cursor migrates into the adjacent monitor’s desktop space.

Problems can arise if the user clicks outside of the full-screen application’s display area. Clicking in another display has a similar effect to hitting the Windows key or Alt-Tab. In other words, clicking on another display causes the desktop to gain focus, which in turn causes the full-screen application to lose focus.

Ideally, software should be written to be multi-monitor aware. However, until that happens there is a variety of ways to overcome the edge-scrolling problem.

One of the most common methods of overcoming the edge-scrolling problem is to set up your multi-monitor orientation on a diagonal. With a diagonal orientation there is no desktop space to the left, right, top, or bottom of the full-screen application. What this does for full-screen applications is prevent the mouse cursor from moving beyond the screen edge (since there’s no desktop space there), thus permitting the user to edge-scroll properly. As a downside, a diagonal orientation can make moving the mouse from monitor to monitor difficult. It also often does not match the physical arrangement of monitors, adding to difficulty in working between displays.

Another method is to temporarily remove the offending monitors (literally). While this clearly lets a person run their software properly, it may not be desired to disable all other displays. On a Windows platform removing displays from the screen layout tends to also push all shortcuts onto the remaining active monitor(s). This can be overcome by using utilities that can store shortcut locations, such as ATT (ATI Tray Tools).

There are also some programs that provide full workarounds to the issue. One such utility is CSMMT

In “extended” mode, additional desktop area is created on additional monitors. Each monitor can use different settings (resolution, color, refresh rate). Macintosh computers have supported the “extended desktop” concept since the late 1980s, providing a robust experience for graphic designers, video editors, and even game developers.

This concept was further developed by PC manufacturers and led to the “extended” or “independent displays” mode and the “spanning” or “stretched” display mode. In both these modes, display devices are positioned next to each other in order to create the illusion that the two displays are logically contiguous.

Autostereoscopy is a method of displaying three-dimensional images that can be viewed without the use of special headgear or glasses on the part of the user. These methods produce depth perception in the viewer even though the image is produced by a flat device.

Several technologies exist for autostereoscopic 3D displays. Currently most of such flat-panel solutions are using lenticular lenses or parallax barrier. If the viewer positions their head in certain viewing positions, they will perceive a different image with each eye, giving a stereo image. Consequently, eye strain and headaches are usual side effects of long viewing exposure to autostereoscopic displays that use lenticular lens or parallax barriers. These displays can have multiple viewing zones allowing multiple users to view the image at the same time. Other displays use eye tracking systems to automatically adjust the two displayed images to follow the viewer’s eyes as they move their head.

A wide range of organisations have developed autostereoscopic 3D displays, ranging from experimental displays in university departments to commercially available displays. Examples include: Alioscopy, Apple, Dimension Technologies, Fraunhofer HHI, Holografika, i-Art, NewSight, Philips (see WOW VX), SeeFront, SeeReal Technologies, Spatial View, and Tridelity. Sharp also claim to have the technology, although not for commercial sale at the moment.

Autostereoscopy is a method of displaying three-dimensional images that can be viewed without the use of special headgear or glasses on the part of the user. These methods produce depth perception in the viewer even though the image is produced by a flat device.

Several technologies exist for autostereoscopic 3D displays. Currently most of such flat-panel solutions are using lenticular lenses or parallax barrier. If the viewer positions their head in certain viewing positions, they will perceive a different image with each eye, giving a stereo image. Consequently, eye strain and headaches are usual side effects of long viewing exposure to autostereoscopic displays that use lenticular lens or parallax barriers. These displays can have multiple viewing zones allowing multiple users to view the image at the same time. Other displays use eye tracking systems to automatically adjust the two displayed images to follow the viewer’s eyes as they move their head.

A wide range of organisations have developed autostereoscopic 3D displays, ranging from experimental displays in university departments to commercially available displays. Examples include: Alioscopy, Apple, Dimension Technologies, Fraunhofer HHI, Holografika, i-Art, NewSight, Philips (see WOW VX), SeeFront, SeeReal Technologies, Spatial View, and Tridelity. Sharp also claim to have the technology, although not for commercial sale at the moment.

Many monitors have other accessories (or connections for them) integrated. This places standard ports within easy reach and eliminates the need for another separate hub, camera, microphone, or set of speakers. Integrated accessories are often of substandard quality.

Most modern monitors contain a power saving mode that will switched to if no video input signal is received. Modern operating systems can thus power down a monitor after a specified period of inactivity. This also extends the service life of the monitor.

Some monitors will also switch themselves completely off after a time period on standby.

Most modern laptops provide a method of gradually dimming the screen after periods of inactivity, or when the battery is in use. This is to extend battery life, and reduce wear.

Multiple devices can be connected to the same monitor using a video switch, in the case of computers, this usually takes the form of a “Keyboard Video Mouse switch” (KVM) switch, which is designed to switch all of the user interface devices for a workstation between different computers at once.

More than one monitor can be attached to the same device. Each display can operate in two basic configurations:

* The simpler of the two is mirroring (sometimes cloning’,) in which at least two displays are showing the same image. It is commonly used for presentations. Hardware with only one video output can be tricked into doing this with an external splitter device, commonly built into many video projectors as a pass through connection.
* The more sophisticated of the two, extension allows each monitor to display a different image, so as to form a contiguous area of arbitrary shape. This requires software support and extra hardware, and may be locked out on “low end” products by crippleware.
* Primitive software is incapable of recognizing multiple displays, so spanning must be used, in which case a very large virtual display is created, and then pieces are split into multiple video outputs for separate monitors. Hardware with only one video output can be tricked into doing this with an expensive external splitter device, this is most often used for very large composite displays made from many smaller monitors placed edge to edge.

Newer connectors are being made which have digital only video signals. Many of these, such as HDMI and DisplayPort, also feature integrated audio and data connections. One less popular feature most of these connectors share are DRM encrypted signals.

The first popular digital monitor connectors, such as DVI-I and the various breakout connectors based on it, include both analog signals compatible with VGA and digital signals compatible with new flatscreen displays in the same connector. This made the connector nearly painless for users of both technologies.