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The biggest problem I know of, for a projection-TV system, is the fact that the light bulb is very bright and gets very hot and has a relatively short lifespan. We need a more energy-efficient source of bright light!
One quite-efficient way to generate light is to cause an electrically charged particle
to experience an acceleration. And one way to do that is to force such a particle, travelling at high speed, to follow a curved path.
It is an odd fact of Physics that an object moving at a constant speed, but following a curved path, is nevertheless experiencing "acceleration". That's because the definition of "acceleration" is "ANY change in a velocity" --and the definition of "velocity" encompasses both "speed" and "direction". So, if we change the direction an object is moving, even if its speed is constant, the object can be said to be experiencing acceleration --ANY change, either in speed or direction, suffices.
In various scientific instruments popularly known as "atom smashers" and more accurately known as "cyclotrons" or "synchrotrons", electrically charged particles are accelerated to high speed following a curved path, and they do indeed emit light in the process. One reason modern particle accelerators are built large (the newest one, the Large Hadron Collider, is 8.6 kilometers in Diameter) is because the gentler the curvature that the charged particles travel, the less energy they emit. Obviously it can be difficult to create a high-energy particle beam if most of the energy is lost while simply traveling in a circle! (The lost energy is known as "synchrotron radiation".)
There are some particle accelerators that have been purpose-built specifically to generate synchrotron radiation. That's because, after more than 60 years of development, we can manipulate charged particle beams very precisely, and synchrotron radiation can be a very "pure" light source. It is almost as pure as laser light, but it is easily a great deal brighter, and also is very much more energy-efficient in the way the light is produced, than any laser can yet manage. Not to mention that a synchrotron light source can accomodate an extremely wide range of frequencies, including hard Xrays, which no laser at all can currently do.
See the link. A synchrotron Xray source is quite a large machine, and certainly isn't something you want in your living room for a projection TV! However! The energy of a single Xray photon can be many thousands of "electron volts", and that alone is the main reason a synchroton light source tends to be large. It simply takes a large machine to "pump up" charged particles to the point where it is possible for them to radiate such large amounts of energy.
Photons of ordinary visible light possess approximately 2 electron-volts of energy (not 2 thousand or 2 hundred, just plain 2). This means that a synchrotron light source, designed to create visible light, could actually be a rather small device (on the order of a half-meter, and maybe less)!
I'm envisioning the core of this unit to be triangular-shaped. Each straight tubular section is surrounded by a magnetic field coil, and contains a fairly simple electrostatic acceleration zone for the charged particles in our circulating beam (probably ordinary electrons). Each curved section uses more magnetic fields to force the particles to emit light. We accelerate the particles to slightly different energies in each of the three straight sections, so that red light emerges from one curved section, green light emerges from the second curved section, and blue light emerges from the third curved section (blue light at about 2.5 electron-volts of energy is about twice as energetic as red light). We then combine the beams of colored light appropriately, either before or after modulating them with a TV signal, and project them toward our home theatre screen.
Note that because we use the same circulating electrons over and over and over again, to generate light, this can indeed be an extremely long-lasting light source. The magnetic fields are constant-strength, and the electrostatic acceleration fields are constant-voltage. There is almost nothing changing that can wear out!
(Upon further thought, it appears to be necessary to add some changing electrostatic fields in the vicinity of the curved sections, to ensure the electrons, after following the curve, don't reverse course. Still, this can be electronically controlled, and if not overpowered can still last a long time. <rant>I hate that lots of modern electronics seems deliberately to be operated at such a high power that lifespan suffers. Did you know if you "underclock" the CPU in your computer by maybe half-a-gigahertz the machine likely will last three times as long?</rant> Not to mention any circuit prone to failure can be modularized for easy replacement.)
National Synchrotron Light Source
As mentioned in the main text [Vernon, Dec 21 2009]
STFC Daresbury Laboratory
World pioneer [8th of 7, Dec 21 2009]
Light Source with Electron Cyclotron Resonance [xaviergisz, Dec 21 2009]
Some scientific details, for anyone interested. [Vernon, Apr 20 2018]
Mentioned in my anno. A type of particle accelerator [notexactly, Jun 11 2019]
The Museum of Unworkable Devices: Stevin's principle
Mentioned in my anno. Also, check out the rest of this site if you haven't seen it beforeit's about how all sorts of perpetual motion machines don't work [notexactly, Jun 11 2019]
Wikipedia: Garter spring
Mentioned in my anno. A coil spring bent and joined into a toroidal shape [notexactly, Jun 11 2019]
Advanced Certificate in Powder Diffraction on the Web: Properties of Synchrotron Radiation
Mentioned in my anno. The page that told me synchrotron radiation is unsuitable for these applications [notexactly, Jun 11 2019]
Mentioned in my anno. Spectrally pure light source powered by an electron beam, and the core of a free-electron laser [notexactly, Jun 11 2019]
||Surprisingly, this appears to work [+]
||All projection television (as indeed all television) seems to
be based on the same idea - scanning a spot (either an
electron beam, or a refresh scan, or whatever) rapidly
across a screen in front of the viewer. However large the
screen, the viewer's eyes condense the image onto the
retina, where it is smaller than a postage stamp.
||Therefore, it strikes me that there is a more ergonomic
and economic solution. Simply modulate the intensity of
three fixed lasers (blue, green, red), all of which are aimed
at the eye of the viewer.
||Then, use an electromagnetically actuated head-clamp to
scan the viewer over the image in synch with the
||[MaxwellBuchanan], I do think the laser approach is under active development. Note it is a personal-viewer device, even if it appears to be widescreen. So, every member of a group would need the device to see a particular video. The advantage of a general projection unit is that you only need one to let the group see the video.
||I agree with your points, Vernon. It's just that I'd like to
build a machine which could fire three lasers into the eyes of
people watching Big Brother, whilst shaking their head back
and forth at a 60Hz scan rate.
||How efficient would this be as a source of ordinary lighting in a room? Would it be better than conventional electric lamps?
||[nineteenthly], see the patent that was linked by [xaviergisz]. I sort-of-think the answer is "yes and no", for a couple of reasons. First, the basic light output (quite efficient, yes) is just-one-color, unless specially designed to emit multiple colors (as in triangular version described in main text) --and then the colors need to be mixed with appropriate mirrors and/or lenses, if you want white light. Second, the light will be emitted as a beam more than as a glow. You'll need add more mirrors and/or lenses to be able to illuminate a whole room with it at once. I suspect the price tag will be too high for this purpose.
||The price of projection-TVs is easily high enough to allow research into developing this variant for that purpose, though.
||//as indeed all television) seems to be based on the same idea - scanning a spot//
I'm pretty sure this is not how my LCD TV works.
||I think it still scans, in the sense that pixels are refreshed
dynamically, perhaps row-by-row.
||Though i can see the price would initially be high, i wonder if it might pay for itself. I personally would be happy with monochrome light towards the blue end of the spectrum. I used to use that anyway, the only problem being that it makes a lot of people uncomfortable so it's not conducive to family life or having friends.
||What about Cherenkov radiation?
||It is extremely inefficient to generate Cherenkov radiation. It only occurs when some particle, moving through some medium other than a vacuum (like water), moves faster than the speed of light in that medium. So, in a device specifically intended to do this, you first have to boost the speed of a lot of particles to tremendous velocity (probably in a vacuum), inject them into the relevant other medium, in which the emission of Cherenkov radiation is the mechanism by which they lose energy and slow down to less than the speed of light in that medium -- and then you have to somehow filter them out of the medium so you could accelerate them again. The main energy-wastage will occur after they stop emitting Cherenkov radiation, and lose all the rest of their energy as heat, due to friction-equivalent interactions with particles of the medium.
||Sad. Ah well, stick with synchrotron then. However, presumably that means that transparent media are all very slightly luminous because of the neutrinos.
||Sorry, I should have specified "charged" particles. Neutrinos don't qualify
||Really? I'll go on Wikipedia in a sec to be comfortingly misinformed, but i've always thought of it as analogous to a sonic boom, applying to anything which moves particle-wise.
||I'm pretty sure some sort of interaction with the medium is required. Neutrinos mostly just don't interact, passing through solid matter, so there is no reason for them to slow down. Meanwhile, the vacuum of space is full of "virtual particles" of ALL sorts, including things that neutrinos are practically guaranteed to interact with (if actually encountered). That suffices to ensure any hypothetical FTL neutrinos would quickly become STL neutrinos, via sonic-boom-equivalent interaction mechanism.
||Otherwise I'd expect a fair amount of heating to take place in our bodies, due to all the sonic booms of all the Solar neutrinos passing through them --and this is not reported, so.....
||This is a pretty great idea [+]
||You say a synchrotron for X-rays is quite large
do you think it
would be possible (for me) to make one? How about for
gamma rays? For a few years I've wanted to build a
portable synchrotron to use as a high-brilliance
X-ray/gamma ray source
to be used responsibly, of
||// How efficient would this be as a source of ordinary
lighting in a room?
Would it be better than conventional electric lamps? //
||It would be very efficient, but it would have a CRI near
zero. However, I
think you could modulate the emitted wavelengths by
bending fields, and thereby scan the visible spectrum. If
you did that
rapidly enough, you could achieve a persistence of
near 100. I don't think that would reduce the efficiency
||[notexactly], for gamma rays you would almost certainly
have to accelerate protons in your synchrotron, instead of
electrons. Fortunately for you, lesser acceleration of
protons can yield X-rays.
||You will still need a significantly-sized power source.
Remember, **each** photon of ordinary visible light
carries maybe 2 electron-volts of energy, while an
average X-ray photon might carry a thousand times as
much energy, and an average gamma photon might carry
a million times as much energy. If you can't supply the
power, you can't get a lot of the desired photons.
||With respect to ordinary room lighting, I'm going to
suggest that if we want to use a synchrotron as the
primary light-source, it might be simplest to tune it to
ultraviolet light (about 5 electron-volts per photon; see
the link), and then use fluorescence to change
that to white light.
||Are there such things as electrons?
||Something has been named and the mesh frame of facts as a model works unbelievably extremely well. So yes. But then a single uncovered fact can show a whole new perspective.
||With a sufficiently powerful and focussed synchrotron
beam, it should be possible to write directly to the visual
cortex, eliminating the bulk and clutter of TVs, lighting and
||Ah, a picture, a tan (maybe, stain) and a blinding smile. In 2 seconds flat.
||[+] neat... I'm trying to get a handle on this : so,
||electrons are accelerated linearly, then their path is bent enough to emit a photon(s) - tangentially or radially ? - out of the device onto a cinema screen, assumedly losing speed in the process. They then hit a conductive plate (out of the photon escape path), where they're recycled, their remaining energies averaged out. Rinse and repeat. Yes ?
||So the beam would go through a magnetic field which determines its vertical angle (scanline), then through a horizontal field which determines its horizontal angle and also does the photon-release bending.
||3 slingshots, one for each colour. hmm... could you get that down to one ?
||[FlyingToaster], the electrons are not stopped; they move
continuously through a triangular loop. The sides of the
triangle slowly accelerate them to an appropriate energy;
the sharp corners strongly accelerate them to make them
emit photons. At any single corner all the electrons emit
same color of light. But every electron emits all three
colors as it travels around the overall triangle and pass
through the three corners. We want the triangle to
contain electrons all around its perimeter, so that light is
emitted continuously from the three corners.
||The light has to be collected with mirrors. A rotating
mirror can be used to make the continuous beam scan.
||Alternatively, it could use an SLM (such as a DMD (such as
TI's DLP) or LCD (such as the common 3LCD arrangement))
each color, similarly to existing projectors and RPTVs. It
could evengiven the
the light sourceuse a MOEMS beam steerer (such as a
GLV) in place of the scanning
||// the vacuum of space is full of "virtual particles" of ALL
sorts, including things that neutrinos are practically
guaranteed to interact with (if actually encountered) //
||What things are those? Could they or similar things be
harnessed and concentrated to
neutrino capture for the purposes of an improved
||// [Synchrotron radiation] is almost as pure as laser
light, but it is easily a great
deal brighter, and also is very much more energy-
efficient in the way the light is
produced, than any laser can yet manage. Not to mention
that a synchrotron light
source can accomodate an extremely wide range of
frequencies, including hard
Xrays, which no laser at all can currently do. //
||Except free-electron lasers. But those use synchrotron
radiation to do it.
||A TV, really. A moon beacon or emergency daylight , I suggest is more fitting. Though, if the money comes from the TV.
||[This annotation is pretty much all wrongsee the last
paragraphs, after the bracketed note. I'm posting it
anyway because I think it's still interesting and
potentially inspiring, and some bits of it are still accurate
AFAIK. It's probably worth reading.]
||In your idea, you imply that it's the acceleration, and
thereby the electrons' kinetic energy, that determines the
wavelength of synchrotron radiation emitted in
the bend. In my anno a year ago, I implied that it's the
bending magnetic field strength instead. Upon thinking
about it the other day (after my previous anno), I
realized it does make more sense the way you were
talking about it. It seems to me that the wavelength
emitted does indeed depend on an electron's kinetic
energy rather than how hard it is accelerated around the
curve, while the rate at which it emits photons is what is
dependent on that acceleration (curvature).
Also, it seems to me that the nonzero spectral linewidth
of the synchrotron radiation is due (at least in part) to
the electron's kinetic energy decreasing slightly
as it goes around the bend, due to emitting photons as it
does so; previously, I had been thinking the spectral
broadening was due to the necessary nonuniformity
of the magnetic field.
||But you could still accomplish the spectral scanning for
CRI improvement I described, by the analogous method of
varying the acceleration in each side of the
triangle rather than the bending field in each corner. (Of
course, it doesn't have to be a triangle if you don't
specifically want three wavelengths simultaneously.)
||You could even vary the multiple wavelengths being
emitted from the multiple bends in a multiphase
sinusoidal manner. Things generally prefer to oscillate
sinusoidally, so that (or close to it) would probably be the
easiest modulation waveform for the accelerators (which
I'm presuming to the typical RF cavity type,
so this would be frequency modulation applied to their
drivers). The more phases (i.e. the more bends and the
more accelerators), the denser your spectral
temporal coverage, and the better the CRI for a given
modulation frequency. But I expect that even with only
two or three phases, probably even with only one,
you could modulate it fast enough that human eyes would
perceive good CRI. The other thing about this is that sine
waves are "denser" (spend more time) in the
region around the peaks and troughs than in the region
around the middle. So, if this causes bad CRI, you could
compensate by modifying the waveform, or by
running different phases on different spectral ranges.
Simple examples: multiple phases all centered at the
same wavelength but with different spectral
excursion (modulation amplitude), or multiple phases
with the same spectral excursion but offset center
wavelengths. You could even have the different bends
trade roles, or cycle roles around the ring, in such a
scheme, if that helps with, say, efficiency by allowing you
to resonantly circulate the modulation around the
ring, or something.
||I just had a thought: the synchrotron lamp could be quite
good for spectrophotometry! No need for a
monochromator or a linear CCD with a diffraction grating.
Just a single broad-spectrum photodetector, and have the
synchrotron lamp scan its output wavelength. It would be
faster than a monochromator in scanning,
and it would be optically "faster" than either conventional
type because the lamp would be brighter than an
incandescent lightbulb or a deuterium arc lamp
(and, importantly, would be much more brilliant and
therefore much more efficiently couplable to the input of
the optical system). Due to that much greater
amount of light going through the sample, you might be
able to get away with a cheaper detector than a
photomultiplier. OTOH, the increased amount of light
might damage or affect the properties of the sample.
Synchrotron radiation goes all the way to hard X-rays,
too, much shorter than the ultraviolet produced by a
deuterium lamp, though you might need a different
||And I had another thought just now (after I wrote the
immediately above paragraph, as I started to write the
one above that): you could get the three
wavelengths needed for the display application without
using one corner of triangle for each wavelength, and it
might even be preferable to not do it that way. I
mean that, by modulating the acceleration, you could use
only a single bend to get all three wavelengths,
sequentially. That (sequential RGB light, or sometimes
more than three wavelengths) is the usual input to a DMD,
so that would make integration with existing display
technology easier. You could even use a circular
synchrotron, if you could somehow accelerate in the same
region as bending without any conflict between the two.
(If attempting that, I suggest to take
inspiration from synchrotrons designed before the
discovery of strong focusing.) A microtron [link] or
cyclotron might be better for a continuous-bending
actually, though you might have more difficulty
controlling the outward spiral of the electrons in those
designs. With any of these continuous-bending variants,
the synchrotron radiation would be emitted uniformly
outward in the plane of the device, and could be
collected and concentrated by an annular concave
mirror, possibly with some sort of annular lens or
diffraction grating to remove the tangential component of
the light. (Hmm
that feels illegal. I feel like there's
some kind of geometric equivalent of Stevin's principle of
virtual work [link] for optics that prevents this
radialization of tangential light. It also feels like an
etendue violation: tangential light approaches being
radial as the distance from the source to the observer
approaches infinity, so to make the light radial at
close range feels like it would be a free lunch.)
||It also has occurred to me that your idea as written is
already a pulsed light source, just by using a synchrotron,
which by definition accelerates discrete bunches
of particles, so maybe you might as well do it that way,
unless you want to use three accelerators and optimize
each one for a given amount of kinetic energy.
OTOH, the synchrotron's bunch frequency is probably a lot
higher than the wavelength alternation frequency you'll
want to use for a DMD.
||Another thing I just thought of, while proofreading the
above paragraphs: compact packing of the synchrotron.
AFAIK, most or all existing synchrotrons (and
circulating particle accelerators in general) are built in
the shape of flat rings, because that's the shape that has
the least severe bends and therefore the least
loss of power to synchrotron radiation. But in these
applications, we want bends, and we also want to keep
the overall size of the apparatus down. Therefore,
you could overlap the accelerators in the Z axis and make
something like a figure-eight or a trefoil knot, allowing
you to use the space in the middle of what
would normally be an empty ring. You could even orient
the accelerators parallel to the Z axis, forming a ring or
nested rings around the Z axis, with bends at
the ends of the bundle. It would look like a kind of spring
that I can't find a picture of right now, which is basically a
garter spring [link] extended axially with
straight sections. In such a configuration, it might be
feasible to share the bending field between all of the
bends at each end, using a toroidal magnetic field
||[Here's where I discover I was wrong in most of the
I just looked up some more info on synchrotron
radiation [link] and it turns out that it's actually not
monochromatic at all! If you want to make a
spectrophotometer, you still need to use a
monochromator to filter the synchrotron radiation. The
main advantage for that application is that it's very
smooth over a very wide bandwidth, which is pretty much
the exact opposite of what I was assuming when I wrote
all of the above. (Another advantage is the
high brillianceeven though the monochromator throws
away most of the light that enters it, more of the light
enters it in the first placethe entrance slit is
effectively more efficient.) That broad spectrum also
completely invalidates original synchrotron video
projector idea here, AFAICT. But it's still good for a high-
CRI lamp, actually even better because it doesn't need
any of the wavelength scanning I described.
||I hope that page I found is wrong, but I doubt it. Maybe
some modification to the bending field could make it
work the way we want, but I don't know at the moment
what that might be.
||A currently known technology that can produce
narrow-band radiation from an electron beam is
[link], which uses a static transverse magnetic
field that alternates in direction over a linear region,
causing the electrons to follow a sinusoidal trajectory.
Presumably they are not exhausted and can
continue circulating around the ring after exiting the
undulator. The wavelength of monochromatic on-axis
output is dependent on the spatial frequency of the
magnetic field. It isn't dependent on the electrons'
kinetic energy/speed, so you can't modulate that to
control the output wavelength. Presumably, you could
arrange three of
these (RGB) and one accelerator in a square or doubled
line, using bending magnets at the corners/ends
but not using their synchrotron radiation. Also, an
undulator does produce a lot of other-wavelength
sidelobes, which are usually cut off by its enclosure
they aren't useful. Both of these factors will reduce