| After a year and a half of development, Kinoptics
(Shanghai, China) has publicly unveiled its new single-panel
LCOS solution. The remarkably simple concept uses a single
LCOS panel with a matrix of spatially colored filters coupled
to a light and polarization recovery illumination stage. |
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Kinoptics has not yet developed the LCOS panels or optical
engine to demonstrate functionality, but is now in advanced
stages of fundraising and partnership negotiations, so it
is ready to be more open about the concept.The LCOS panel
itself will be an all-digital design that will likely incorporate
some unique features that will be revealed later. RGB subpixels
will be used to create a full-color pixel.
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Key to the system operation are the dichroic filters used in
the LCOS panel. Here, CEO Fan Bin borrowed an idea from the Scrolling
Color Recapture (SCR) concept developed by TexasInstruments. Instead
of using heavily absorbing dye filters to create RGB light under
each pixel, she decided to use the same thin film technology used
to create the color bands on the SCR color wheel. These thin film
stacks pass light within the R, G or B color bands, but reflect
out-of-band light. This out-of-band light is not lost, but is
recaptured in a polarization and light recycling light tunnel.
| As shown in the single-panel system
schematic, light from the lamp is collected and UV/IR filtered
before entering the light tunnel. The entrance to the light
tunnel has a small aperture to let light in, but the interior
surface has a mirror to reflect light. |
| The light tunnel evens out the illumination
and shapes it for imaging onto the display. A quarter waveplate
and Moxtek wire-grid polarizer are placed on the exit port
of the light tunnel to provide polarized light for the LCOS
panel. This light is imaged onto the panel through a PBS,
with the desired light exiting the system through the projection
lens.At each pixel, red, green or blue light is passed through
respective microfilters. As mentioned before, out-of-band
light is reflected off the filter and PBS and back into the
light tunnel. |
 |
| The quarter waveplate allows the
correct polarization to be maintained, while the mirror on
the entrance aperture recycles light and sends it back to
the LCOS panel. This light can be used again to illuminate
the LCOS panel, thus boosting efficiency. |
Kinoptics has modeled the performance of this single-panel
system, as shown in the table below. The first two lines describe
the overall system efficiency without light recycling. Here
the company assumes a standard PBS assembly with the noted
efficiencies for the rod (light tunnel), polarization conversion
system (PCS), polarizer, microfilter, LCOS panel, analyzer
and projection lens. Multiplying all of theses together produces
an engine efficiency of 10.5%.
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The second line assumes the use of a 3M optical
core for the PBS. Since this assembly contains its own analyzer
and is more efficient than a standard PBS, Bin has adjusted the
numbers to reflect this, coming up with an improvement to 12.4%
overall system efficiency.
The addition of the light recovery system is modeled in the third
line. Again, the efficiencies of the entrance aperture/reflector,
spacer, PBS, aperture ratio, PCS, rod and recapture rate are modeled.
The aperture ratio refers to the percentage reflective area on
the entrance of the light tunnel (70%). The spacer refers to the
gap that surrounds each microfilter and the added light that can
be collected from this if a reflective metal is used. This component
must be added to the 0.66 reflectivity factor first before multiplying
by the rest of the efficiency terms. The recovery rate term accounts
for losses as light passes back and forth through optics like
the field lens that are in between the light tunnel and LCOS panel.
Multiplying all of these factors yields a 28.4% gain in efficiency
with the light cycling elements.
Multiplying this 28.4% gain times the first or second PSB implementation
cases results in a boost in system efficiency to 14.4% (standard
PBS) or 17.3% (3M core).
Bin also has a clever way to improve efficiency
even more through color balancing. Since UHP lamps are red deficient,
she proposes making the red pixel a bit bigger so that less light
needs to be wasted in the green part of the spectrum to achieve
proper color balance.
Kinoptics has been in touch with both Ocean Optics and OCLI, the
two providers of the SCR thin-film filter technology, and both
have agreed to fabricate the microfilters on the glass for use
in making the LCOS panels. Other partnerships to make the panels
and system are in the works, with announcements expected later.
With three-panel LCOS projection systems struggling to reach a
commercial critical mass, all are looking to single-panel LCOS
solutions for the future. This approach is simple, elegant, small
and potentially low cost. It has no moving parts, offers reduced
thermal loading (fewer birefringence problems), and is compatible
with many LCOS designs and foundries. This is definitely worth
looking at.
And there is more - but we will hold that story for another day.
Kinoptics, Fan Bin, [86] 21-5047-6535, fanbin@kinoptics.com
Contact:
Insight Media
Annmarie Gabisch, 203-831-8464
annmarie@insightmedia.info
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