Multimedia Power For Your Overhead Projector

by Terrence E. McCormack
MC Journal: The Journal of Academic Media Librarianship, v2 no.1, Winter 1994:70-72.

The ongoing development of the color Liquid Crystal Display(LCD) overhead projection panel has the potential of drastically altering the way visual and audio media are now utilized for presentations and instruction. It is now possible for media departments to produce full multimedia programs using an overhead projector, an LCD panel, and a laptop computer. A panel with multimedia capabilities can provide a presentation that combines computer animation, textual information, photographs, and full action video.

Similar in appearance to their monochrome predecessors of a few years ago, the color LCD panel of today still resides on the glass platforms of overhead projectors. They are equipped with translucent LCD screens and receive data from microcomputers. However, unlike the earlier panels, today's LCD models are more compact, have distinctive levels of color capability, have much higher resolution, and the varying degrees of electronic aptitude required for advanced graphics, full motion video and audio applications. In order for a panel to function as a true multimedia unit, it must meet minimum requirements in the above mentioned areas.

Visual capacity is the most important factor to consider in selecting an LCD panel. This alone determines the operating level of the panel and its ultimate cost. The quality of an LCD panel is measured by colors available, image resolution, and whether the system is a passive or active matrix.

Availability of color in a panel will range from 8 to 16 million color types. The more colors available result in superior rendition of an image.

Resolution is determined by the number of pixels available to construct the image on the screen. The more pixels available result in a sharper and easily focused image. Most panels have

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a minimum of approximately 300,000 pixels that the industry informally considers the standard. However, some LCDs designed for full motion video may have considerably more than the standard.

Whether an LCD panel is a passive matrix or an active matrix defines the differences between multimedia and non-multimedia panels. A passive matrix system delivers an electronic pulse along rows of pixels in a wave form across the screen. Most of the older monochrome and the inexpensive color panels use this system. Passive systems are considered to have a slow response time and are suitable for display of computer generated graphics, and textual information. The complex nature of a full motion video signal requires a system that can react much faster. Active matrix panels also use a pulsing system, however, each pixel has an electric storage element that releases energy between pulses to maintain a constant image.

Most top of the line active matrix LCD panels will accept, directly or through a converter, conventional video, S-VHS or RGB signals. A majority of panels in this group can also accept multiple broadcast standards such as NTSC, PAL or SECAM; and some can be regulated for international voltage levels. Some are also equipped with mini audio speakers that are only marginally effective.

Most, if not all panels are equipped with remote controls and on-screen menus which may allow presenters the ability to adjust image quality, and perform some special effects such as moving video or text images. With the use of presentation software the active matrix panels are capable of choreographing multiple media forms in the same context, for example text information together with a full motion video image frame and an audio track playback.

Active matrix LCD panels may prove to be the ultimate source for future multimedia presentations, however, there are some

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significant costs involved. Quality active matrix panels start around $4,000.00 and can go as high as $9,000.00. While the cost is high, the image quality of most active matrix panels is outstanding and rivals that of the best video projectors. In some situations the investment may pay off by avoiding the purchase of other expensive equipment that may only have occasional use.

In the future expect continual improvement of panels in the areas of higher resolution, color and greater flexibility. Some multimedia models to consider are: Sharp's QA-1650 and QA-1150, the Telex M2X, Proxima's 822C and the In Focus Systems Panelbook 525 projection panel.

Terrence McCormack is Head, M. Robert Koren Center for Clinical & Legal Education, Charles B. Sears Law Library, State University of New York at Buffalo.

MC Journal: The Journal of Academic Media Librarianship
ISSN 1069-6792
January 1994

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