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Idea for Stroboscopic Flat Panel Display

I

IsaacKuo

I have this idea for creating a large flat panel display, and wonder
if it's feasible.

The basic idea is for the panel to be a thin slab chamber of
water or gel. The edges are coated with a reflective mirror
surface, so total light reflection keeps light inside the panel.
One side is perforated with tiny holes, so the water's surface
tension keeps it flat.

Three stroboscope LEDs feed red, green, and blue light
in turn into the edge of the slab. These need to be able to
provide extremely short duration flashes at precisely
60hz (or greater).

The display is shaped using a row of ultrasonic transducers
along one edge of the display. These act as a phased array,
concentrating sound waves onto individual pixels. The
computer electronics sum up the waveforms of every displayed
pixel. As a result, when the strobe flashes, the "active" pixels
are places where the sound is concentrated. In these places,
water pressure causes the water surface at the perforations
to be bumpy. These bumps spoil total internal reflection,
and as a result light can escape at the active pixels.

Note that these sound waves only concentrate onto the desired
pixels momentarily. This is why a strobe is required. The
light "captures" the image at the precise point in time when
the sound waves are concentrated as desired. The rest of
the time, these sound waves interfere in arbitrary ways. If
light were applied continuously, imaging may still be vaguely
possible but it will be extremely blurry--each active pixel
would have an hourglass shaped halo around it.

The duration of the strobe pulses need to be maybe one
microsecond or less, but the brightness needs to be able to
illumate the entire panel, if necessary (for a pure white image).
Is that feasible? Would multiple LEDs be necessary or better?

I'm not sure what requirements are for the linear transducer
array. Assuming a pixel size of around 1mm, the transducers
need to operate at at most a 1mm wavelength and need to
be at most 1mm wide.

I think this concept could be suitable for inexpensive flat
panel displays. Most of the display is simply a water
chamber surrounded by bulk glass or plastic. One
edge has the ultrasonic transducer array, which I
imagine would be the most expensive component. Is
there a way to make this component less expensive?

The display itself is naturally transparent. For use as a
TV or computer display, you'd want it to be backed by
a black coating, of course. For an artistic display, the
transparency may be considered a feature rather than
a flaw. This panel may be cut to any convex shape
(as long as the transducer array has an unobstructed
view to all pixels in the active display area).

Ideas? Criticisms?

Isaac Kuo
 
J

Jan Panteltje

Ideas? Criticisms?

Isaac Kuo

I am not 100% sure how your system works, _one_ array of
transducers would have problems creating _one_ pixel
or one row of pixels in the other dimension.
The idea to use fluid is not new, look up 'Eidophore'.
In the Eidophore a scanning electron beam was used to manipulate
the surface of an oil film.
In a vacuum and electron beams can go anywhere fast.
So how do you addres coordinate x,y?
 
I

IsaacKuo

On a sunny day (17 Mar 2007 10:48:58 -0700) it happened "IsaacKuo"
<[email protected]>:
I am not 100% sure how your system works, _one_ array of
transducers would have problems creating _one_ pixel
or one row of pixels in the other dimension.

My idea was to build up an image in time, so that the waves
constructively reinforced to create the desired image at the
instant the strobe light was flashed.

However, I have since realized that I had the approach all
backwards. This approach requires very precise control
of the transducers in a highly complex way.

The transducers were doing a very complex job, while
the LEDs were doing a very simple repeating job (just
strobing periodically).

Instead, the greatly superior approach is to have the
transducers do a relatively simple repeating task, while
the LEDs do a relatively simple modulated task. The
transducers produce sound waves to constructively
reinforce on a simple raster scanning pixel, while the
LEDs create the image by modulating their brightness
levels.

My new refined idea has a different construction. From
back to front:

1. Black rear coating.

2. Clear reflection coating.

3. Plastic optical chamber.

4. Perforated clear mask.

5. Water chamber.

6. Clear front wall of water chamber.

The plastic optical chamber is a slab of plastic with a
mirrored coating around the edge. It's made of a
hydrophobic material. Red, greed, and blue LEDs
feed this chamber with light from the edge, where
total internal reflection contains the light.

The perforated clear mask is also made of a
hydrophobic material. The surface of the water
has bumps which poke into the perforations, but
these bumps don't touch the optical chamber
unless sound vibrations provide sufficient pressure.

The water chamber has maybe a dozen blade
shaped sonic actuators spaced across the bottom
edge. These form sound waves which constructively
reinforce to a raster scanning pixel. Within the
currently active pixel, pressure is sufficient to
make the water bumps touch the optical chamber.
Light leaks out from the chamber at these contact
points, and reflects off the curved bump surfaces
to deflect the light into a forward cone.

The waveform required for creating the raster
scanned pixels is calculated in a straightforward
manner. For each pixel, there's a particular time
"t" when it should be activated. The required
waveform is a spike at time t-d/s, where d is
the distance between this pixel and the sonic
actuator, and s is the speed of sound in water.
By summing up all of the spikes, you get a
periodic waveform for each sonic actuator.

This approach vastly simplifies the electronics
design task. The Red, Green, and Blue LEDs
are simply fed analog amplified signals straight
from the VGA cable. The challenge is calculating
the transducer waveforms and syncing them
up to the incoming hsync and vsync signals.

Isaac Kuo
 
J

Jan Panteltje

This approach vastly simplifies the electronics
design task. The Red, Green, and Blue LEDs
are simply fed analog amplified signals straight
from the VGA cable. The challenge is calculating
the transducer waveforms and syncing them
up to the incoming hsync and vsync signals.


Perhaps you could make a small prototype to see if any
problem some up.
A prototype with only a few pixels, and one color.
 
M

Michael Brown

IsaacKuo said:
I have this idea for creating a large flat panel display, and wonder
if it's feasible.

No idea ... but an interesting variation would be to feed audio into the
transducers and shine powerful LED or laser light from below (for
transmission) or above (for reflection) such that the "picture" gets
projected onto a ceiling or wall. You could even put a small amount of oil
on top for a thin-film effect.

Hmm, might have to go and try this ...

[...]
 
I

IsaacKuo

On a sunny day (17 Mar 2007 22:28:34 -0700) it happened "IsaacKuo"
<[email protected]>:
Perhaps you could make a small prototype to see if any
problem some up.
A prototype with only a few pixels, and one color.

Yes, I think this refined design is getting simple
enough that I can try it out. My original concept was
just excessively complex.

I've currently refined the concept so there's no need
for messing with water. There are now only two
layers:

1. Rigid optical sheet of clear plastic edged with
mirror coatings and three LEDs.

and

2. Flexible vibrating sheet of with a frosted inner
surface. The edge is supported at 12+ points
by vibration actuators.

Instead of sound pressure waves, this sheet is
vibrated transversely, like a rubber sheet.
The frosted inner surface contacts the optical
sheet at a single pixel at a time (raster scanning).

Compared to my earlier concept using water,
this is a lot less "fiddly". Unfortunately, the frosted
surface will reflect ambient light so the black
levels are no better than a front projector. This
may be mitigated by using a dark coating, but
of course this cuts down on the display's own
light also.

Isaac Kuo
 
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