Questions tagged [imaging]
187 questions
17
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4 answers
Usage of helium in MRIs
More and more articles pop up on the shortage of helium, and on the importance of it. Its usage in MRI's spring to mind for example. I looked it up and found out that helium is used for its 'low boiling point' and 'electrical superconductivity'. So…
user14445
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14
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3 answers
Can we make images of single atoms?
I was wondering how far in imaging physics had gotten. Do we hold the technology to actually take a picture of, say, an alpha particle, or even a single atom?
I realise we aren't talking about camera pictures, so what kind of imaging techniques have…
Ole Christian
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14
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5 answers
Technical explanation of "Hitachi lensless camera"
Hitachi is bragging about a thin lensless camera. I can't find any technical information on how it works---just press releases etc.† Can anyone work backwards from the published descriptions to reconstruct how this works?
The "concentric-circle…
Steve Byrnes
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12
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3 answers
Put a sensor at the focal length, behind, or in front?
My intuition tell me that at the focal length a convex lens all the light converges to a point. Following that logic, it would make sense to me that a camera chip would either need to go slightly in front or slightly behind the focal point in order…
dinkelk
- 275
12
votes
1 answer
Orange ring in a black hole image
What exactly is the origin of the orange ring around M$87$?
I understand that the image was not taken in the visible light range. The colors are therefore artificial.
I also read that the image shows the shadow of the black hole on a brighter…
user1583209
- 4,362
8
votes
5 answers
Exoplanet detection via space-based parasol
I remember from watching Cosmos years ago, Carl Sagan suggested an interesting hypothetical method for directly seeing exoplanets. He proposed that in the 'future' we could launch a satellite designed to block the light from distant stars,…
Fergal
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8
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1 answer
Took a picture of my laptop screen with my iPhone. The yellowish pattern in the image look like magnetic lines. How is this possible?
The pattern seems consistent with the magnetic force lines of a bar magnet.
mightwork
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7
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5 answers
do lenses with curved focal planes exist
I know about spherical, aspherical, cylindrical lenses, but are there lenses that could have a curved focal plane? for example, the retina of the eye is curved, and still we see sharp images of distant objects.
In a recent problem I studied, I…
MrBrody
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7
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1 answer
Is There Reddening on Objects Other than the Moon Upon Entry into Earth's Umbra?
With the recent lunar eclipse, for some reason this question came to me: The reason the Moon turns red is that the only appreciable sunlight hitting it when it's in Earth's umbra is refracted through Earth's atmosphere and shorter wavelengths are…
Stuart Robbins
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7
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4 answers
How to guess the content of a christmas present?
Let us assume that the present does not make any recognizable sounds when shaken (meow splat - the present now contains a dead kitten). Let us furthermore assume that the internal state of the present does not change, so that any measurements can be…
hpekristiansen
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6
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3 answers
PSF Measurements In Fluorescence Imaging
Quite a technical question!
I have measured the Point Spread Function of 100nm fluorescent breads with my Olympus scanning head. I'm two-photon exciting the beads with a wavelength of 800nm and focused in the sample with a 100x with N.A.: 1.4
The…
Steve
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6
votes
4 answers
Optical explanation of images of stars?
Very often when viewing pictures of the cosmos taken by telescopes, one can observe that larger/brighter stars do not appear precisely as points/circles on the image. Indeed, the brighter the light from star, the more we see this effect of four…
Noldorin
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Detecting dim objects
What are the minimum conditions (switching times, sensitivity ...) for a camera to detect dim objects, e.g. Oort cloud or Kuiper belt objects, passing by in front of a star in the background?
I've read the Hubble did this. Is it possible also from…
draks ...
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5
votes
2 answers
How to produce a loss-free combination of two "identical" beams?
This is for anyone with experience in optics/imaging/photography as well as anyone who likes to puzzle over tricky physics problems.
As the title suggests, this is about combining two (for all practical purposes) identical light beams in an…
Tolllike
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5
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Why do we see a black hole shadow despite the fact that there is hot gas all around it and not all radiation is absorbed by the horizon?
If the accretion disk surrounds the black hole (like that seen in M87 by the Event Horizon Telescope) but is too far away from the black hole to have its light captured, why do we still see a black shadow? Is the 'shadow' not covered from our…
Jumales
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