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| Secrets of the short throw |
| by Joy Zaccaria |
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January 22, 2008
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Gaining popularity as a "killer app" alongside the electronic whiteboard, short throw projectors serve plenty of uses for government installations and training facilities as well as in the corporate world. Mounting inches away from the screen, short throw projectors are all the rage now that a presenter or instructor can get through an entire class or training session without being blinded by the projector beam and without having some important information projected onto his or her backside instead of the screen.
The newest short throw projector from Sanyo is the PLC-XL50, which mounts three inches away from the whiteboard. "It shoots down behind the instructor and there's no shadow or light in the eyes," said Mark Holt, Sanyo vice president/general manager of the projector division.
NEC came out with a smart board earlier this year that was bundled with the company's short throw projectors. "NEC's WT610E short throw projector mounts above the whiteboard itself so the presenter is not in the image line," Rich McPherson, product manager for installation in specialty projectors at NEC. The avoidance of shadows on the screen is going be a more critical issue because of increased interactivity in meetings, he added.
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It's The Mirrors
Mounted 2.5 inches away from the wall, the NEC WD610E will create a 40-inch diagonal image. At 25.8 inches, it's a 100-inch diagonal image. So how does the technology work?
"Instead of having a lens that has to zoom in and out to focus to the screen, we just use mirrors, so there's no lens at all," said McPherson. "The WD610E uses four mirrors. We bounce the image across those mirrors to get it out onto the screen. That's what allows us to have such a short throw."
With Sanyo, the XL50 is equipped with an aspherical lens shooting onto an aspherical mirror, according to Holt. "Think of rear projection units -- you have a light engine that bounces off a mirror back to the screen," he explained. "We built that all in to one box that mounts in front."
As far as the major manufacturers can see, the future for short throw projectors makes the most of interactivity. For Sanyo, the new XL50 is designed to go beyond the whiteboard and wall mount.
"It has the capability to shoot up or shoot down," said Holt. "The XL50 can point straight down and shoot on the floor or can be turned upside down to shoot it up onto a graphic table for engineering drawings."
Short throw projectors, such as the new Hitachi CP-A100, will also work on a tabletop. "You can turn it on its end and project it down on to a tabletop and get a big 60-inch image," said Hitachi's John Glad, product manager for the Ubiquitous Platform Group, Business Division. "Now you can use your tabletop as an interactive place for a number of people looking at a map, for example."
Another advantage of the short throw is in the application of rear projection systems. "Typical rear projection systems would need a sled, a big mechanical system with a mirror that bounces the image off onto the back of the screen," explained McPherson. "That's going to take real estate at least three maybe five feet in depth behind the screen."
With NEC's rear projection, using the WT610E, it only requires about 24 inches. "And you don't need the external sled and mirror system, because it's built in," added McPherson.
Recently, with short throw projectors being widely used beyond the education market, Toshiba is realizing a trend with their business customers adapting to the widescreen format. "With the rising trend to match the increased resolution to widescreen, we came out with the ESPC series, which stands for Extreme Short Projection Capability," explained Jane Poon, product marketing manager for Toshiba projectors. "That's where we are today with our EW25 and EX20.
"Extreme short throw is now designed to meet needs beyond the education market. We're learning from our customers in the government sector that a lot of people are doing training in addition to business presentations."
Inherent Limitations
For short throw projection in front of the screen, there are security and aesthetic advantages over conventional projectors. "With a short throw projector, it has to be quite a bit closer to the ceiling or even up into the ceiling and then shooting down to the screen so that nobody in the room can have access to the controls, lensing, or the mirrors," said McPherson. "If it is over top of the table or training room, the conventional projector is hanging down where people typically can get to it."
However, with a typical short throw projector, there isn't the flexibility a front projector has to increase the size of the image by moving the projector farther from the screen. "You're limited to a certain size image," Holt admitted. "Typically, the lens is fixed on a short throw projector. In our case, you have an image range of 60 inches to 80 inches diagonal.
These projectors can be mounted on the wall without the need to run power or AV cable up to the ceiling. "You don't have the flexibility of a front projector to drastically change the size of the image," Holt added, "but it's offset by the advantages of easier installation."
"The short throw projector doesn't have a lot of zoom to it because it's using a mirror as part of the lens," Glad concurred. "You have to do more playing with it to set it up so that it's square and it's not keystoning on screen."
Earlier attempts at short throw projectors had some optical problems. It was a common complaint that they would either put a hot spot on the screen or there would be focus issues in the corners or edges. However, Sanyo's current product is optically correct, according to Holt. "There's no hot spot and the focus is solid from center to edge and corner to corner."
While short throw projector have some inherent limitations, the technology doesn't impact features like networking or security. "The inside of the projector is pretty much the same as the rest of our projectors," Glad offered. "The only difference is the lens and the optics itself."
MORE INFO
Hitachi hitachi.us
NEC necdisplay.com
Sanyo sanyo.com
Toshiba toshibadirect.com
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