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Interleaved (or
separated) Fresnel lenses can be registered to a
flat panel display to send stereoscopic images to
the viewer.
In the Figure, mixed (R
and L) LCD pixels 1 are intended to be viewed by
a viewer 2. The backlighting 3 of the LCD 4 is
collimated normal to the panel surface 5 by the
use of louvered glass 6. This glass 6 is
auxiliary to, and therefore bound to, one of the
liquid crystal material side walls or optionally
could be used as the bounding plate itself. If
the louvers are placed between the backlights and
liquid crystal material 8, reduced heating takes
place. Between the LCD Panel 1 and the viewer 2,
there is placed carefully aligned field optics 9
and 10, each of whose Fresnel-optic terrace
corresponds to a given column of pixels. The
optics 9 and 10 direct the main ray from the
respective left or right pixels directly into the
viewer's eyes 2. The first acceptance angle of
the louvers defines a finite CRT pupil. The
Fresnel-optic can be made of a molded plastic,
like acrylic.
The left and right parity
views can also be made contiguous within
themselves and simply butted laterally together.
This latter implementation has the advantage that
a field lens (of sufficiently high pitch) could
be made of two conventional lenses, centers
offset, simply butted together over their
corresponding parity images, without any
requisite relationship between pixel position and
Fresnel terrace. It exploits the well-known fact
(from the practicality of stereopticon views)
that the two stereo views need not be
overlapping.
The field optics in the
proposed designs need not be cylindrical.
Focussing action in the vertical direction would
be desirable to maintain brightness at the top
and bottom of the displays indeed.
In operation, a small,
thin, lightweight panel could be easily moved
about to provide maximum viewer comfort, so that
the "fixed" nature of the relatively
small exit pupils of the proposed display is
reduced.
Since the louvers
restrict transmission of light through the LCD to
small angles off the normal, even today's
"poor" viewing angle multiplexed
twisted nematic displays would be acceptable for
use. Note that doubling the pixel count for such
a display to produce stereo images need not
increase the multiplex level, which would have
reduced optical contrast.
Of course, a large
variety of liquid crystal devices and other light
valves might be used to implement such displays,
other than the simple multiplexed twisted nematic
LC device. A louvered backlight could pass light
through the narrow optimum viewing angle of the
LCD, so a Lambertian diffuser could be used in
place of the field optics of the proposed design.
Of course, to obtain sufficient brightness, the
backlighting would have to be greater.
Disclosed anonymously
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