Visual Display Solutions in Traffic Management Centres - DLP Cubes Strike Back

eyevis video wall in a traffic management centre (PresseBox) (Reutlingen, ) Traffic control rooms for the observation of roads and highways are the nerve centres of today's mobile world. At the other end of every video camera, intelligent traffic sign or traffic guidance system there is a control centre staffed with several operators. The amount of traffic in most areas of the industrial countries has grown to an extent that needs control and regulation from the outside. Therefore, these control centres receive comprehensive information from various systems including traffic counters, video cameras, alarm systems and other traffic management systems.

In general, traffic control centres have a video wall system as a master display of all information providing a complete overview to all operators in the room. Since these installations are usually operated 24 hours per day, the technology of choice for the video wall system is DLP® rearprojection. This technology is still the leading solution for professional video walls in continuous operation since it does not suffer from damages to the display quality caused by static content and it also provides the smallest gaps between the individual modules in the video wall. In the past few years manufacturers of LC displays made huge efforts to make their products more competitive compared with DLP rear projection cubes. And in deed, they made substantial improvements. The vulnerability of the LCD screens by static images was decisively improved but is still existent. The bezels of the latest devices were reduced to a minimum allowing video wall arrays with only 7.3 mm gap between the screens. DLP cubes lost many of their unique features. Especially in terms of colours, traditional lamplit DLP cubes were far behind LCD monitors. But DLP cubes stroke back.

In the beginning of 2009, eyevis was first to present an LEDlit DLP cube version. Since then all important manufacturers came up with comparable models which are now available in many different sizes and resolutions. The advantages of this new illumination technology are obvious. First, there the decisively longer lifetime of the LEDs compared with the high performance mercury lamps in lamplit cubes. In numbers this means 60,000 hours in continuous operation for the LED compared with 8,000 to 10,000 hours with lamps. To make this more illustrative, LED cubes are expected to run at least six years, 24 hours a day, 7 days a week. This enhanced lifetime reduces not only the costs for the customer, but also reduces the downtime of the system for service and maintenance works. But even if we take the costfactor out of consideration, LEDcubes remain the method of choice. While their lamplit ancestors had could not compete with LCD screens with regard to their representation of colours, the new LED cubes provide colours of unprecedented quality. This is mainly caused by the fact that there are three individual LEDs in each system, one for every primary colour. The dispensability of colour wheels and other optical components makes the light path less complex and therefore simpler to control. This results in enhanced colour fidelity and better adjustment possibilities for the image quality. The improved lighting behaviour of the LEDs guarantees more stable colours and brightness of the cubes. For a complete video wall comprising several of these cubes this results in a perfect homogenous desktop surface over the entire screen area. The comprehensive sensor measurements inside the cubes provide even more stability. In case of malfunctions or extreme rises of temperature the cubes automatically reduce the performance of the LEDs to protect the system. Of course there is still an image visible bright and colourful enough to keep the control room in operation until the failure is resolved.

No wear parts, almost no colour drift, automatic adjustment of all cubes - you'll be likely to forget where you have bought your system. But as with cars, even the most expensive and reliable ones, we advise to have an inspection made about once a year in order to keep the system clean and orderly.

What LEDlit cubes still have in common with traditional lampbased versions is the robust housing which has a certain depth to take all the necessary components of the system and to enable an optimal light path inside the cube. For some installation this depth is a decisive criterion for the choice of a display technology. This is mainly the cause in smaller control rooms or backup sites which cannot provide enough space for a rear projection cube wall. Here is where LCD screens find their place. It is important to distinguish between consumer LCD TVs and professional LCD monitors. First difference here will of course be the price. But trying to save money in the first place may double the costs when the system has to be replaced because the displays could not stand the requirements in a control room environment. Professional LC displays should feature optimised components to allow for their use in sophisticated areas such as traffic control centres. These include ventilation especially in "tiled" LCD video wall applications, as well as highend panels combining image quality with reliable operation. For socalled "personal wall" applications it is also possible to use large format LCD monitors with resolution beyond HD. Otherwise the reduced viewing distance between operator and screen does not allow a sharp image. Highest definition LCD monitor have a resolution of fourtimes HD or even more on a 56" screen or larger, guaranteeing crisp images even when viewed from a short distance.

The decision between rear projection and LCD depends on numerous factors - the space available, the budget, the size of the final video wall and several others. For large scale video walls there is hardly a chance to get around LED rear projection cubes. Best reliability, perfect colours, low operational costs. For smaller installations using LCD screens it is important to watch out for quality. But a main fact that has to be taken in consideration when talking about visual display systems for traffic management is that the display system is only the visible end of a long signal chain. Before the images can be displayed they have to be produced, transmitted, sometimes encoded and decoded, and various other processes which take place in little black boxes somewhere in the signal chain. This means that the entire chain needs to match certain quality standards in order to grant an efficient operation of the control room. The poorest signals will not look decisively better on a high quality display. Low quality accessory devices may also cause bottleneck in terms of quality to the signals.

For this reason, it is important to have the planning and equipment of the traffic management system and control room done by highquality partners, especially the video wall system which provides the final result of the traffic management tools. And the video wall system does not only include the screen. There are always additional components necessary to visualise the incoming data, such as graphics controllers, cables and comprehensive wall management software tools. A higher investment on the initiate purchase most often turns out to be worth it when we look at future costs for operation and maintenance.

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eyevis Gesellschaft für Projektions- und Großbildtechnik mbH
Hundsschleestrasse 23
D-72766 Reutlingen
Max Winck
Marketing
Marketing Manager

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