Stirring the pot

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[donaldk]

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Blending, Resolution and Black Levels Top Trends in the Simulation Market

December 6, 2006
By Chris Chinnock
I am writing this column from the I/ITSEC trade show - the main North American event held each year in Orlando Florida to show off the latest in simulation and training technology.  This is a fun show - where else can you get to sit in dozens of flight simulators with full spherical screens and killer graphics?  And to make these simulations as real as possible, a key element is a great display system.

It sometimes takes a few days after a show to fully divine the trends that have shaped the show, so these mid-stream observations will undoubtedly become clearer as I write the news up for our monthly newsletters.  That being said, a few themes have emerged so far.

For big display systems, users want to reach eye-limiting resolution, which for people with good to very good eyesight is  1 to 2 arc-seconds.  To get to this point, you need lots of pixels on the screen.  This is often accomplished by using multiple projectors and blending the images to create one large seamless image.  To increase pixel density, you can increase the resolution of the projectors or use each projector over a smaller area.  The latter approach is usually too costly, however.

This year at I/ITSEC, we are seeing a lot of image blending/warping technology that can now be performed automatically and quite quickly.  This is good for system operators as it reduces downtime and speeds set-up times - both of which affect the bottom line. 

The idea is to use a camera to take snap shots of test patterns generated in sequence by each projector in the cluster.  Then, using software, the geometry of each projector is adjusted to align with the other projectors across a flat, curved or spherical screen.  If a non-flat screen is used, warping technology will make the image appear geometrically correct on the curved screen.  These systems can also reduce brightness of pixels in the blend region so you don't see a brighter band where the projectors overlap.  Barco, Christie, 3Dperception, Mersive Technologies and Scalable Display Technologies all showed versions of this capability.

Some companies will focus on using lower-cost projectors and inexpensive cameras to provide this warping/blending.  This is fine for many applications, but when color accuracy and brightness uniformity are important, or when low-light-level imagery is projected, additional steps must be taken.  To make sure the colors are accurate over all the projectors, higher-performance cameras can be used.  These can also do a better job of evening out brightness non-uniformities among projectors.   

Unfortunately, a multi-projector image will always need to conform to the poorest-performing projector in the group, so it pays to buy good projectors and keep them well maintained.

With low black levels, the blended areas will still stand out if only electronic corrections are added, so optical blending is used.  Optical blending is usually implemented with custom-designed plates that obscure the projected beam at the blend edges.  At I/ITSEC, we learned that Barco is using a variable neutral-density filter approach that eliminates the plates.

The other advancement that created some buzz is the debut of new QXGA (2048 x 1536) projectors.  These projectors feature LCOS panels from Gemidis - a company we have been tracking for a number of years but is only now becoming more visible.  These panels offer very high contrast, as Barco demonstrated in a side-by-side demo of a projector prototype using the Gemidis panels vs. a "competitive" LCOS projector - most likely one from JVC.  The contrast was, indeed, extremely good on the Barco projector.

Another company, SEOS, uses these panels in a unique four-panel architecture that can offer stunningly high contrast ratios.  In the prototype demonstrated at I/ITSEC, the company achieved 150,000:1 sequential contrast in a dark room, but when the first projector using the architecture is launched in early 2007 (at the Hayden Planetarium in New York City), contrast will reach 250,000:1. 

Is this meaningful and needed, you ask?  The answer is yes.  For nighttime flying or planetary fly-throughs, it is necessary for very little light to exit the projector, which is what this high contrast guarantees.  In the fully darkened demo environment at the show, black levels were, indeed, extremely low.  Impressive.

That's it for now.  We will have more later in our newsletters.