Como funciona un Video Beam? Data projectors - How do work? Video Beam

• Data projectors – page overview
• Principle of data projectors
• Technologies
• Resolution
• Features, functions and applications
• Important maintenance instructions for data projectors
• Important notes regarding the warranty for data/video projectors

Data projectors have established themselves as the indispensible tools for professional presentations. Great progress has been made to make the installation and operation of portable projectors as easy as possible so that there is no need for any time-consuming preparation of the equipment.

The information on these pages has been devised to assist you in obtaining the best possible projection image of your information. This is not difficult when you understand the design and functional principles that are shared between virtually all data projectors. Simply take a few minutes to read this chapter – and any problems you might have encountered will be a thing of the past. As data projectors are widely available and offer a wide range of functions, they are sometimes not used to their full potential so that the quality of the image is rather poor. Please note that not all data projector functions are useful in all projection situations.

Principle of data projectors

Nearly all portable data projectors work in the same way. The image to be projected is transmitted in the form of electrical signal data from a PC or a video source through a number of interfaces to the projector. These signals are then converted into an image on the microdisplay in the projector. A strong light – normally consisting of a long-life gas discharge lamp – emits its light onto the microdisplay. The resulting image is then projected through a vario (zoom) lens onto a screen, which should be located above the lens level.

Technologies

At the moment, there are two predominant technologies available in the market of portable projectors, namely the DLP^TM technology by Texas Instruments and the 3LCD technology promoted by Epson and others. Both technologies have their advantages and disadvantages. To understand these, we must first examine their technical principles.

DLP™

DLP stands for Digital Light Processing. The key components are a tiny chip and micromirrors. Each micromirror represents one pixel of the image. These mirrors can be repositioned rapidly to reflect light either through the lens or on to a heatsink where it is absorbed. Depending on the mirror position, a bright or dark pixel is projected. Multi-coloured images are produced by placing a spinning colour wheel between the lamp and the micromirrors, which deflects the light into the primary colours of red, green and blue (RGB), which are projected in sequence. As these rapid changes are invisible to the human eye, the impression of a continuous colour image is created.

3LCD

3LCD technology uses three microdisplays made of polycrystalline silicone. LCD stands for Liquid Crystal Display. The liquid crystals act like valves, each representing one pixel of the image. The white light from the lamp is split into the basic colours and then beamed separately through the three displays. The three colour images are combined using a prism to form a full-colour image, which is then projected onto the screen through a lens (source of figure: AV-Views).

LCOS

LCOS (Liquid Crystal on Silicon) technology is a relatively new development. Similar to DLPTM technology, it is based on reflection of the light. With LCOS, the light is not, however, controlled by mechanical mirrors but by liquid crystals. As the silicon chip surface coated with liquid crystals is completely smooth, the projected image does not show any raster structure. With LCOS technology, it is possible to produce high-resolution images using low-cost chips. As with DLPTM, three chips are used for the three primary colours. The design of the optical engine is, however, much more complex than in 3LCD or DLPTM. With the launch of the XEED series, Canon was the first company to offer compact and powerful LCOS projectors with high resolution.

Advantages and disadvantages

What is the effect of the data projector technology on the projector and the image? DLPTM data projectors are simpler in design and therefore tend to be more compact, sturdy and lighter in weight than 3LCD data projectors. A perfect example of this technology is the Geha compact 215. As the light is reflected on the surface, DLPTM technology produces images without interfering stray light, allowing for better contrast. This is, however, not of great significant in everyday business use, as the contrast is limited by the ambient light. As the pixels of the image are very close to each other, the image is homogenous. With 3LCD projectors, the design of the image-generating unit leads to shadows that are visible as a faint "fly screen" in the image.

On the other hand, 3LCD data projectors produce vibrant saturated colours, while DLP^TM projectors for business applications compromise in this area to improve brightness, which is achieved by adding a white sector to the RGB colour wheel. The "rainbow effect" associated with older DLPTM models, which is created by sequential colour projection has virtually been fully eliminated in new data projectors.

As the chips used in 3LCD technology are not transparent, they must be cooled with air, which makes the projectors highly susceptible to dust. The organic filter materials used in 3LCD data projectors decompose under the influence of light, so that they are not suitable for continuous use and must be replaced regularly. For more information on the above technologies, see www.dlp.com und www.3lcd.com.

Resolution

The resolution of the image is determined by the number of pixels it contains. It is normally indicated in numbers of columns and rows. Resolution of currently available models:

Designation	Pixels	Image format
Business
SVGA	800 x 600	4 : 3
XGA	1024 x 768	4 : 3
SXGA	1280 x 1024	5 : 4
SXGA+	1400 x 1050	4 : 3
UXGA	1600 x 1200	4 : 3
WXGA	1280 x 800	16 : 10
WXGA	1440 x 900	16 : 10
Video
NTSC	640 x 480	4 : 3
PAL / SECAM	768 x 576	4 : 3
Wide NTSC	852 x 480	16 : 9
PALplus	1024 x 576	16 : 9
HD720	1280 x 720	16 : 9
HD1080	1920 x 1080	16 : 9

The following general rule applies: the greater the resolution, the more details are visible in the projected image. The resolution of data projectors is fixed and cannot be adjusted. In a series of projectors, the image quality is therefore determined by the weakest link. To achieve best results, all elements from the signal to the projection screen must be compatible and carefully chosen. The resolution of all components must match that of the displays built into the projector. All other resolutions must be calculated, which can lead to blurry images. For business applications, an image format of 4 : 3 is the standard. Home cinema systems use image formats of 16 : 9. The new business format of 16 : 10 is still rarely used and only a limited number of data projector models are actually able to detect it!

Features, functions and applications

Many of the data projector features are very useful in particular situations. There are, however, some pitfalls with certain functions!

Automatic source detection:

This user-friendly function ensures that the image source is detected automatically by the data projector.

Blank, mask, shutter:

The projected image is dimmed down. These functions are very useful if you wish to shift the audience's attention away from the projection to the speaker. They might also be activated during short breaks to avoid switching off and restarting the data projector. While this prolongs the service life of the lamp, it can damage the 3LCD chips, so that this function is normally limited to a maximum of 15 minutes. When this period has lapsed, the lamp is automatically switched off.

Ceiling installation:

Portable projectors generate an image above the projection level. If you wish to install the data projector on the ceiling, the image must be produced below the projection level. To achieve this, you can simply mount the projector upside down and activate the ceiling installation function. The projected image is then put on its head to appear correctly on the screen. Data projectors feature threaded bores for easy installation on ceilings.

Digital zoom:

Use the zoom function to ensure that even the people sitting in the last row can read the fine print in your tables. The size of the image is not changed in the process. See also •Zoom function.

Freeze:

With the freeze function, the projected image can be frozen during the presentation. You might use this function to page forward through your slides or to work on the PC without your audience noticing it.

OSD:

The OnScreenDisplay function projects the data projector function buttons onto the image. A variable OSD is most useful, as it ensures that certain sections of the image are not constantly covered. In some data projectors, the dialogue can also be completely switched off, so that no parts of the image are hidden.

Projection ratio, PR (see fig. 1):

The projection ratio varies from model to model and is used to calculate the size of the image and its distance from the projector. This ratio is denoted as the distance (between the lens and the projection screen) over the image width. If the image width is given, simply multiply it by the PR to calculate the distance. If the distance is fixed, divide it by the PR to determine the image width. For zoom lenses, the calculations are based on the extreme values.

Reset, default settings:

This feature is known to most people from their PC. If everything freezes, try to reset the data projector. All settings are reset to the default, or average, settings. You might need to change the menu language from English to German.

Trapezoid correction, keystone correction:

With parallel projection, all portable data projectors produce a rectangular image above the projection level. If the image is to be projected to a higher position, data projectors can normally be tilted slightly by adjusting its front foot. The resulting image is however trapezoid in size, so that its upper edge is wider than the bottom one. Using the automatic (or manual) trapezoid correction, the image can be corrected. This, however, affects the image quality, as the pixels must be recalculated. While this function is very useful for portable data projectors that are in frequent use at various locations, it should never be used for fixed installation. A much better image can be achieved by placing the data projector on a projector table that can be adjusted in height, or by adjusting the projection screen with the keystone bracket.

Wide angle lens:

To create large images in rooms where space is restricted, many portables are equipped with lenses with a short focal length and thus a smaller projection ratio. Such projectors are, however, more prone to produce trapezoid images. It is therefore very important to project the image parallel to the data projector!

Zoom function:

The size of the projected image can be easily adjusted to the size of the projection screen by turning the zoom ring at the lens. The zoom range of data projector lenses is, however, only 1.3 to 1 (largest image to smallest image at a constant distance) and thus much smaller than that of cameras.

Important maintenance instructions for data projectors

Please note that projectors must cool down after use. Therefore do not disconnect the projector immediately from the power supply, unless, of course, you have an "unplug & go" data projector. Regularly clean the air filters, following the instructions in the data projector manual. This is normally required every 200 to 300 operating hours. It must, of course, also be done in projectors that are mounted on ceilings and might not easily be accessible! 3LCD data projectors are not suitable for continued operation from six hours per day upwards! The organic filter materials must be allowed to cool down for a prolonged period every day, as they are otherwise destroyed. If the image shows cloudy discolouration, immediately switch off the projector.

Important notes regarding the warranty for data/video projectors

Data/video projectors are subject to special warranty terms.

Normally, the warranty period is 36 months, unless specified otherwise in the documentation. It does not cover consumables and wear parts, such as lamps, air filters, LCD panels, polarisation filters and colour wheels. Lamps are covered by a separate lamp warranty.

It is only valid if the device is used according to the instructions and if the use restrictions (< 6 hours per day) are adhered to. In addition, all maintenance instructions must be adhered to.

Damage caused by improper use or installation, external impact, transportation, repairs or modification carried out by unauthorised parties are not covered by warranty. Neither is damage due to artificial fog, high air humidity, cigarette smoke or other aggressive media and solvent vapours. The warranty further excludes damage caused by the use of consumables such as lamps and air filters that do not meet the required technical specifications. Projectors operated in continuous mode are not covered by warranty (with the exception of the Panasonic PT-D-4000, PT-D5700 und PT-DW5100 models).

Geha lamp warranty for data projectors

The first lamp installed in Geha data projectors is covered by warranty for a period of 180 days or 500 hours (whichever is reached first). The warranty does not cover replacement lamps.  

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