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We had a chance to see a laser projection display system at a
recent visit to Eastman Kodak (Rochester, NY) (www.kodak.com).
In a dark room, we saw a 115-inch display system that offers very
crisp and beautifully saturated images.
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Kodak has developed a new spatial light modulator to go
with the laser display, which we profiled in the June 2004
edition of Projection Monthly, page 8. The technology is
called Grating Electro Mechanical System (GEMS) and it is
used to construct a 1 x 1080 array of diffractive elements.
It is similar in concept to the Grating Light Valve (GLV)
being developed by Silicon Light Machines and Sony, but
there are some important differences.
First, the mechanism to create the grating is different
from a GLV device. In a GEMS device, for example, the diffracted
light orders are scattered perpendicularly to the long axis
of the modulator, whereas in a GLV, the orders are created
along the long axis. This leads to a simpler optical system.
In addition, the second and higher orders in a GEMS device
are high-contrast orders - not the case with GLV. This will
lead to more efficient systems with higher-contrast images.
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To create a display system, red, green and blue laser light are
formed into narrow lines of illumination. Kodak says that with
a GLV device, the positioning of this light must be very precise
- about 10 microns. But the tolerance is much looser with a GEMS
structure. The benefit: a lower-cost and more manufacturable system.
Kodak can manufacture GEMS arrays in almost any length. Two pixel
pitch designs have been demonstrated so far; one at 36 microns,
which is used in the demo, and one at 18 microns. Kodak feels
comfortable being able to produce 1 x 2000 element arrays and
might be able to achieve 4K later.
The laser light illuminates three GEMS devices, and it is combined
at a spinning galvanometer that sweeps these lines of light horizontally
to create an image. The 115-inch prototype system created a 1920
x 1080 resolution image at 60 Hz with 11 bits of grayscale per
color.
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The image quality of the system is excellent. It is high
contrast (1000:1 sequential, 250:1 ANSI) with crisp images
and no obvious motion, rendering artifacts or pixelization.
The system is not that bright, but was fine in the dark
room. The dark state also needs improvement, as there is
a noticeable glow and horizontal "streaks" of
light. All of this is a consequence of the prototype status
of the system. Plus, there is noticeable speckle in the
white and green parts of images. Kodak has implemented some
speckle reduction techniques and is working on additional
methods to address this.
The most impressive part of the system is the color saturation.
This was most noticeable in the blues, which are the deepest
and richest we have even seen. The CIE chart shows the achievable
wider gamut.
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To drive home the point, Kodak set up a side-by-side demo with
a JVC G10 LCOS projector, specifically designed to produce high-quality
color images. A red to blue color transition mage was first shown
on the JVC projector, which most would say showed a very good
gamut and rich, saturated colors. When the laser GEMS version
was shown, the extra depth of the color saturation in red, green
and blue was very apparent. Unfortunately, this difference is
impossible to show in a newsletter like Projection Monthly. You
have to see it.
Kodak is now evaluating the market opportunities for the technology.
Stay tuned.
Kodak, Chris Johnson, (585) 477-4550, chris.johnson@kodak.com
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