Last Update October 24, 1996

Types of Projection Systems:

• Liquid Crystal Display (LCD) panels. These come in various resolutions and are either active or passive matrix. They sit on top of an overhead projector. The units are quite portable and can easily be carried to class.

• All in one projection systems: These are a projector plus LCD panel into a built in unit. Until recently, these units were a bit bulky and heavy and were not be convenient for personal transport to a classroom. Now there are some models which weight about 20 lbs and are more easily transportable. These are called LCD projectors or sometimes multimedia or data projectors.

• Ceiling Mounted RGB systems. These are permanent fixtures that have a control panel at the front of the room. In general, this is not a good solution. AT the very least, these units should be mounted only in rooms with fairly high ceilings so that you have a reasonable chance at getting the beam angle correct so that you don't have convergence problems. However, with the new flexibility of today's portable LCD projectors, its not clear to me that ceiling mounted units should even be considered anymore.

Mininum Requirements for decent projection in a classroom:

• A good overhead projector - should be rated at least 4000 lumens but 6000 would be better. A wide angle lens is often necessary as most classroom don't have enough back focal distance to give you a sufficiently large image. The new metal halide overhead porjetors are now rated at 11,000 lumens.

• Good control of lighting. Any ambient light that makes it to the display surface has a significant effect on the visibility. The best room light situation is one where the front of the room is dark. Leaking light from windows is an extreme problem in this regard making many current classrooms on campus unsuitable. The optimal situation is one in which the room lights in the back of the room can be lowered to a point where there is still enough light for note taking. Most of the LCD panels on the market, even with a good overhead, still require fairly low light settings for visibility. The LCD projectors are significantly brighter but still limited to resolutions of 800x600 at the most (see more below). In any case, minimizing stray light on the display surface itself is the key.

• A white, rigid wall is an ideal projection surface. Most screens are not ideal. The convergence properties of most LCD panels (convergence means the letters appear black and are not surrounded by blue or red faint outlines) are quite extreme. A screen is not a hard focal surface and hence focal and convergence variations over the surface of the screen can exist. A fairly rigid screen made of material with glass beads mixed in represents the best projection surface, however, such screens are fairly expensive. A little paint on a wall is an inexpensive alternative.

Important Features:

• Color vs Monochrome: The only reason to ever get a monochrome is if the only classroom application is projection of text and no images.

• Active vs Passive Matrix: The principal difference between these two technologies is the refresh rate of the panel. Active matrix refreshes at a rate of 30--60 times per second. Passive matrix refreshes much more slowly causing two fundamental limitations:
  1. You can not effectively play video or show animation through a passive matrix panel - the individual frames will ghost or blur.
  2. You can not keep track of movements of your pointing device (mouse) on a passive matrix panel as you will move it faster than it can be updated

  Of course, active matrix costs more then passive matrix (see costs section below).

• Resolution: This is key. Units come with either 640x480, 800x600, 1024x768 or 1280x1024 resolution. You pay for resolution at a rate of about $2000 per incremental step. You need to seriously think about the resolution requirements you will need. If your principle classroom application will be to present web pages containing course material and other useful information you will definitely want the 1024x768 resolution. If your principle application is to run software on a PC or MAC and then project it, then you can get by with a resolution that is the same as that on your screen.

  Until very recently, most LCD projectors were limited to 640x480 resolution and could only do 800x600 in a compress and highly pixelated mode. Now, there are two very good true 800x600 projectors that we have evaluated (see below). The higher resolution units do not yet exist, except for one 1280x1024 fixed focal length LCD projector made by ASK. This has a list price of about $17,000.

• Whiteboard: Some panels have whiteboard capability which allow you to draw directly on the screen that you are projecting on. This can be useful at times.

• Monitor loopback cables. Many units offer cabling that allows a monitor to be hooked up as well. This is very useful for the instructor who can then look at the monitor instead of the wall. However, this can also be detrimental to the presentation if the presentor merely stars into the monitor.

• Video Input: The latest active matrix panels accept video/Svideo input. Thus one can hook a VCR/laserdisc directly to the panel and play video through it.

• Remote control pointing features: Newer units offer the ability to use the remote control as a mouse by providing an RS232 port on the projector. However, this requires disabling the internal pointer on your laptop, which is something difficult to do in Windows 95. As an alternative, we recommend the use of a radio (not infrared) controlled mouse such as the Track Man Live product form Logitech. We have had excellent success with this unit and have been able to communicate with the laptop, and hence the presentation, from a distance of up to 30 feet (it depends on the ambient RF in the room).

• Focal Length: Since most LCD presentations by business or in conference rooms this is not an issue. But its a big issue in large classrooms. We are actively searching, without much vendor cooperartion I might add, for a long focal length LCD projector that has a throw distance of 50--80 feet so that we can locate these units in the projection booth along with the slide projectors and 16mm film projectors. Buhl optical makes some reducing optics that can be used but they are expansive and they don't increase the focal length enough. Think of it this way, you know when you go to the movies and before the start of the movie there is a static slide show. Why not use an LCD projector for some multimedia show - because units don't exist with the correct optics to focus the image to fill a theater screen. There is a market out there, are you listening vendors?

Hardware Platforms

• Most units directly accept VGA or SVGA input and are hence designed for use with a PC.

• Interfacing the unit with a MAC requires a special cable.

• If you want to use a unix platform then you should purchase an NCD MCX or HMX X-terminal which has a video out that you take directly to the LCD panel. Alternatively, some units, like the Proxima 920 will take a direct connection from a Sparc 20 workstation.

• Some laptops have non-standard video drivers which are not recognized by LCD panels. Futhermore, many laptops these days are hardware configured to present 800x600 on the laptop screen. When using a 640x480 projector, it is not possible to have simultaneous display on the laptop and the projector in most cases. Still other laptops don't have the functionality to have simultaneous display in any resolution. In most cases, however, the image on the wall is bright enough to be used as a monitor. While this is not an endorsement, we use the IBM Think Pad Model 760-ELD in classrooms here. We also highly recommend the 3Com ethernet connector.

Important Limitations to be aware of

• The brightest projection systems are the all-in-one projector plus LCD panel. However, currently all of these systems are limited to resolutions no greater than 640x480. However, in summer of 96 it is expected that the higher resolution LCD projectors will be available. And indeed, there is a full 1280x1024 unit now on the market made by ASK. However, this unit has fixed focal distance and maximum image size of 12x12 feet. It is also very expensive at the moment (see prices below)

• Loop back monitors when used in conjuction with a MAC are tricky. You must have a good multisync model. Some LCD panels actually use the monitor itself to determine the sync rate. There can be instances where you get a good image on the monitor and a very poor image on the LCD panel itself. There are also instances where the MAC senses the panel as a VGA monitor and the other monitor in the loop won't work at all.

• Bulb life on high intensity overhead projectors is about 25 hours. At the lower setting on these units its 100 hours. For the newer LCD projects that use metal halide bulbs, their life time is 700 - 1000 hours.

• Different colors display differently. In general greens, red and black are the best but blue often doesn't have much constrast.

• There are two types of focus: real focus and convergence. Convergence means the red, blue and green guns all hit the focal target at the same place so that the letters appear black. Often times convergence is a property of the exact location that the LCD sits on the overhead. Moving the LCD panel an inch or so can make a big difference.

• The contrast controls on LCD panels have a wide range of functionality and some are clumsy and redundant. In general, one has to fiddle for a couple of minutes to get the best contrast.

• NEVER switch power supplies and cables- use only those that actually come with the unit. The power requirements are different with each unit and hence applying to much voltage can fry some components.

• NEVER drop heavy weights (like lead) on the glass surface - it breaks.

Recommended Vendors

• Proxima: There equipment seems to be the best and they now are on the leading edge with new technologies. Both the 920 and 846 models are excellent units.

• Sharp: Within the past year, Sharp has come up to Proxima standards first with the QA 1750 and now the QA 1800 and the 2500 high-rez panel. These are as good of units as the Proxima. The one disadvantage is that Sharp continues to put the power connection on the opposite side of the unit as the other cable connections. This can be cumbersome. Sharp's new metal halide projector, the Sharp 1000 has extremely good brightness (I believe it has the highest ansi-lumen rating) and is ideal for fixed situations (i.e. its not real portable). The Sharp XG-630 is a portable (20.5 lbs) 270 ansi lumen 640x480 LCD projector with double the scan lines for video. It has fixed focal length and is the best value for the money (see below). We highly recommend this unit for the K12 classroom.

• In Focus: Also very good and have come out with new products, however, they are no longer the industry leader as they were back in 1993-94.

• Canon: A new player that has made a few mistakes in basic ergonomic design of some units.

• NEC: They make the best high-end stuff where high-end means greater than $10,000

• Sanyo: Another new vendor that makes some excellent stuff. They offer two new products that are worth consideration. The PLC-700M uses a new technology (called TFT - thin film transistor) for more accurate color reproduction. Its truly impressive but definitely not portable as it ways about 50 lbs. The Sanyo 5500, however, is a 16 lb 500 ansi-lumen true 800x600 LCD projector. Its amazing but it costs $7000 (educational discount as of Summer 1996 - price probably lower now).

• 3M: We really like their model 9700 overhead projector. Very good design. The 9800 is quite bright but changing the bulbs is a little more cumbersome. Recently, 3M has introduced what we consider to be the best portable 640x480 projector. The model number is 8020 and its called a multimedia projector. We have done extensive side by side comparisons between the 8020 and the LightPro 580 from In Focus. 3M wins easily. This unit is sufficiently bright that it can be used in mostly normal room light and has excellent video playback capability. The 3M8020 is about to be updated to the 3M8030 which offers ansi-lumens compared to the 300 ansi-lumens of the 8020 (the human eye, however, won't easily detect this 5/3 improvement in brightness). We have bought a number of 8030's for use in 250 seat classrooms here and are quite pleased with their performance (plus its real cool to take a unit home on the weekend and watch football games on your living room wall!)

  3M has also come out with the model 8650 which is a true 800x600 unit which has 1000 ansi-lumens of brightness. This is a beautiful projector if you can afford it. Educational price is $7500. We are also a little wary of buying this resolution if the 1024x768's aren't too far behind.

  Update: Well the 1024x768 LCD projection market is still not here as of Sept. 1997. In the mean time there are several impressive 800x600 UNITS out there including the 3M8640 but we definitely like the SHARP XG-NV1U Notevision - extremely crisp display and nice and portable. Highly recommended.

Prices:

Although prices continue to vary and in general are coming down here is a rough breakdown from the bottom up of the kind of pricing that is available at the educational discount level.

• Black and White 640x480 --> $1000
• Passive Matrix Color 640x480 --> $1500 (these aren't really being made anymore)
• Active Matrix 640x480 --> $3000
• All-in-one 640x480 Active Matrix LCD projector with fixed focal distance --> $3200
• All-in-one 640x480 Active Matrix LCD projector with zoom optics $5200
• 800x600 LCD Projectors with active matrix and zoom optics --> $5-6K
• High resolution 1024x768 Active Matrix Panel --> $7000
• High-resolution ceiling mounted Units --> $12-15,000

• High quality 4000 lumen overhead --> $500
• High quality 6000 lumen overhead --> $800
• High quality 8000-10000 lumen overhead using metal halide bulb -->$1500
• Extra MAC cable --> $90

Links to Projection Vendors and their Products

• Sharp
• 3M Products
• Proxima
• In Focus
• Comprehensive set of presentation tips

The Electronic Universe Project nuts@moo.uoregon.edu