A new microscope?
Robert Karl Stonjek
approach might be viable, or whether this approach has already been explored
by others. Perhaps someone on this forum knows.
In principle, imaging with a microscope requires bathing the object in light
which is then focussed by a series of lenses. At the finest scale, the
required light becomes very intense or the exposure times become very long.
Specially prepared samples can be imaged with electrons.
The light is the problem at the finest scale. Perhaps the object can be
tricked into emitting light rather than being bathed in it.
To do this, the object needs to be heated. It will then emit light of its
own accord as it cools to the ambient temperature. Now, here comes the
clever bit: what if the ambient temperature is just above absolute zero?
Wouldn't the sample glow like a little sun for up to an hour? A quick
google seems to indicate that Cryogenic Microscopy usually involves cooling
the sample and/or microscope *before* imaging. I am suggesting that the
cooling process itself provides light.
Thus I am wondering if this form of cryogenic microscopy is a viable idea or
if the idea has already been explored (which it most probably has :)
Kind Regards
Robert Karl Stonjek
Androcles
"Robert Karl Stonjek" <sto...@ozemail.com.au> wrote in message
news:HP1uk.32422$IK1....@news-server.bigpond.net.au...
Bathing the subject in light isn't the issue, what matters is that the
subject
reflects the light back to the eye (or detector).
Consider this:
I have a common laser pointer that emits red light. If I aim it at my green
wall above my desk the wall scatters the light in all directions, and so I
see
a spot on the wall from any vantage point in the room. BUT.... I do
not see green wall, I see red reflected light. If I aim the beam at a
mirror,
I don't even see red light on the mirror (well, not much, the mirror isn't
perfect), what I see is a red spot on my white ceiling from which the light
is scattered.
If you take a photograph of a mirror, you'll get an image of a reflection
of a distant object and not see the mirror.
So now we suppose that I use a microwave maser, with a suitable detector,
and can see scattered microwaves from objects I want to "see".
What I want to see is the grid on the front of your microwave oven,
it's full of holes and I should be able to see it clearly... but I can't,
it reflects the microwaves like a mirror. The wavelength of the
microwave is too long to get through the holes.
An electron microscope detects scattered electrons that have a shorter
wavelength than light, just as optical light has a shorter wavelength
than microwaves, but a cold object, while it will still radiate, will
radiate at a much longer wavelength.
Tom Roberts
> Thinking about imaging at the finest scale, [...]
Using EM radiation to image an object, one cannot see details smaller
than the wavelength of the radiation used. Visible light has a
wavelength around 500 nm, and optical microscopes can indeed resolve
image details about a micron in size, but not much smaller.
Your idea of "heating" is worse, unless you heat the object so hot it
melts or vaporizes. The infrared radiation emitted by objects with
temperatures below ~500 K has longer wavelength than visible light. This
gets worse as the object gets colder, and at cryo temperatures the
resolution limit could be millimeters or worse.
Electron microscopes can image smaller than a micron, because they use
electrons with wavelengths much shorter than visible light. They are
limited by the available energy of the electron beam, the quality of
their optics, and by the destruction of the sample by the beam.
Atomic force microscopes can image some objects down to atomic sizes
(~0.1 nm), because they don't use radiation.
Tom Roberts
Robert Karl Stonjek
RKS:
Not if you heat it up first, as I suggested. But as it cools, the
wavelength will increase.
But there is no reason why longer wavelengths can not be detected. The
problem with longer wavelengths used to illuminate an object are obvious,
but if the object is emitting those longer wavelengths then I don't see the
problem.
The problem with viewing very small objects is that the intensity of light
must increase and the wavelength must shorten. Either case is sufficient to
cook the object or otherwise change its properties. The cooling object is
emitting light and so its properties are not changing due to the observation
of it, only due to the effect of cooling.
I was being cute with 'bathed in light'.
Robert
Robert Karl Stonjek
"Tom Roberts" <tjrobe...@sbcglobal.net> wrote in message
news:fY2uk.36028$co7....@nlpi066.nbdc.sbc.com...
RKS:
The problem of longer wavelengths and resolution can be solved simply by
arraying detectors around the object. This is not possible if the light is
to be reflected, but if the object is radiating light then detectors can, in
principle, be arrayed anywhere around or above the object. Even if the
wavelength is longer, the light emitted in different directions will have
slightly different properties if the object's shape is not uniform.
Could an object be continuously heated so that it continues to radiate? A
fluctuating magnetic field or laser burst (heat, view, heat, view) may have
potential.
My point is that reflected light has been the main focus of attention
whereas naturally emitted light may have potential under the right
conditions.
--
Sam Wormley
> Thinking about imaging at the finest scale, I wonder if an entirely new
> approach might be viable, or whether this approach has already been explored
> by others. Perhaps someone on this forum knows.
>
> In principle, imaging with a microscope requires bathing the object in light
> which is then focussed by a series of lenses. At the finest scale, the
> required light becomes very intense or the exposure times become very long.
> Specially prepared samples can be imaged with electrons.
>
Classically -- finer resolution requires shorter wavelenght...
but the energy is inversely proportional to wavelength. Too much
energy disrupts what one is viewing.
Quantum Illumination
http://arxiv.org/abs/0803.2022
(Submitted on 13 Mar 2008 (v1), last revised 13 Mar 2008 (this version, v2))
Abstract: The use of entangled light to illuminate objects is shown
to provide significant enhancements over unentangled light for detecting
and imaging those objects in the presence of high levels of noise and
loss. Each signal sent out is entangled with an ancilla, which is
retained. Detection takes place via an entangling measurement on the
returning signal together with the ancilla. Quantum illumination with
e bits of entanglement increases the effective signal-to-noise ratio of
detection and imaging by a factor of 2^e, an exponential improvement
over unentangled illumination.