Video-Data Projection Systems Come of Age
Terian Tyre · T.H.E. Journal Technological Horizons in Education · 1989
Video/Data Projection Systems Come of Age The value of visual aids in instruction is well established and their employ in instruction has a long tradition. Time and technology continue to progress, however, and now it is computer-generated material that needs to be presented. Enter video/data projection systems. Expressly designed to convey software-based information to groups of people, video/data projection systems fall into two distinct types--projectors and LCD projection panels. Each utilizes totally different technologies and is best suited for different physical environments and applications. As a tool, these devices have endless range. Just about anything that can be created and displayed by a computer can be projected onto a screen or wall. Text, charts, graphics, even animated simulations may be broadcast. Extra versatility is gained by the ability to manipulate the data while it is being displayed. Processes can be shown as they occur. Relationships become crystal clear. What if situations can be played out on the spot. And audiences, whether students or peers, can't help but pay attention. Thus the virtues of video/data projection systems are twofold: access to more types of instructional material, and, more access to those being instructed. Projectors Large-screen projection systems are not new, but the current crop are almost another breed. Less bulky and easier to use than their ancestors, the devices can be used with either computers or a video source. Projectors display information in either monochrome or full color. Measured diagonally, image size ranges from about six feet to 25 feet, making projectors the device of choice for instructing large groups of people. In addition, projectors offer sharp, crisp images so material may include a lot of detail. Most video/data projectors have either three lenses or a single lense. Three-lense systems contain a separate lense for each of the three primary colors--red, green and blue--and require careful adjustment to get all three aligned and focused. Called convergence, in the old days this was accomplished by hand--a tricky business at best and further complicated by the fact that many systems are mounted on the ceiling. Modern projectors, however, often contain microprocessors that automate convergence. Three-lense systems usually provide better brightness than single-lense ones, but because of their mechanics, operate best when in a relatively permanent installation, like a lecture hall. Single-lense systems converge colors through dichroic mirrors inside the device, making them more suitable for applications in which they are likely to moved to various locations. A projector's horizontal scan rate determines its compatibility with computers and video recorders. If the range is narrow, interfacing ability is limited. A system that can handle rates between 15.75 KHz and 33 KHz will work with most personal computers including IBM PCs and compatibles, the Apple II series and the Macintosh family. Newer models feature autolock, which is the ability to automatically lock onto whatever scan rate the source is using. Remote controls, often infrared and wireless, are now part of many packages. Convergence, system diagnostics, and on-screen menus for various functions are among the operations that may be controlled through the remote. Other new features of video/data projectors include battery-backed memory for storing set-up instructions for different input sources or actual data for display; a built-in speaker for audio capability; and variable focus control for changing the size of an image without reconverging. LCD Panels Advances in liquid-crystal display (LCD) technology have resulted in a new type of projection device--the LCD panel. These are designed to be used in conjunction with overhead projectors and offer educators a low-cost alternative to video/data projectors. …