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13
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4answers
4k views

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 ...
12
votes
3answers
1k views

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 ...
10
votes
3answers
1k views

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 ...
8
votes
5answers
133 views

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 ...
7
votes
4answers
568 views

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 ...
7
votes
1answer
36 views

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 ...
6
votes
1answer
94 views

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 ...
6
votes
2answers
229 views

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 ...
5
votes
4answers
1k views

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 ...
5
votes
5answers
1k views

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 ...
5
votes
1answer
90 views

Shadow of a Jovian moon over the Great Red Spot

Where can I find pictures of the shadow of any of the Jovian moons partially covering the Great Red Spot? A series of such pictures over time would even be better. The idea is to learn more about the ...
4
votes
2answers
166 views

What is an extreme deep field image (XDF) and how is it captured?

NASA recently took this Extreme Deep Field image (XDF) that is the area of only small fraction of the dia of moon and contains 5,500 galaxies. Nasa says this was capture by extreme long exposures so ...
3
votes
1answer
523 views

Took a picture of my laptop screen with my iPhone. The blue pattern in the image seems to magnetic lines. How is this possible?

The pattern seems consistent with the magnetic force lines of a bar magnet.
3
votes
2answers
595 views

why isn't the variance of Fano noise proportional to the number of photon arrivals?

I've been reading "Photon Transfer" by James Janesick and in Chapter 3 (http://spie.org/samples/PM170.pdf) he describes the various sources of noise in a CCD. Basically, incoming photons interact with ...
3
votes
1answer
679 views

What's the significance of the definition of T1 and T2 relaxation times

In MRI we measure $T_1$ and $T_2$ relaxation times. $T_1$ relaxation time is defined as the time it takes for the longitudinal component of magnetization to recover $1-1/e$ of its original value, and $...
3
votes
1answer
2k views

How does a stronger magnet affect the MRI image quality?

In which ways is a stronger magnet better for magnetic resonance imaging? I read that: The field strength of the magnet will influence the quality of the MR image regarding chemical shift ...
3
votes
1answer
10 views

Laser speckle reduction for integration time of microseconds

How to reduce laser speckle noise for an imaging system that demands integration times of microseconds? I am aware of these two commercial solutions: Optotune laser speckle reducer. It has a ...
2
votes
2answers
71 views

What is the optimal distance to sit from a TV? [on hold]

I was wondering how to calculate the optimal distance to sit away from a TV. I don't quite know the full set of parameters it will depend on, I would suspect it to include the following: Size of the ...
2
votes
2answers
153 views

Can a point source be located more accurately out-of-focus or in-focus?

Let's say I am taking a picture, and I know a priori that the image is of a single ideal point source of light at infinity. With a perfect imaging system in focus, the image shows an Airy disk. I ...
2
votes
2answers
338 views

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 ...
2
votes
2answers
256 views

What is the difference between scattering and backscattering?

I sometimes hear people talking about scattering and backscattering, but I really cannot distinguish between the two? Can some one please explain what is meant by these two concepts from a physical ...
2
votes
1answer
258 views

How does the focal length of the lens change the distance from the camera to an object?

I am reviewing some old image processing notes and have the following problem: I have a camera with a projection plane of $2cm\ by\ 2cm$ and a $15mm$ lens. If you want an $1.5m$ object to take ...
2
votes
1answer
506 views

How to determine the required resolution to view an image at a certain size?

If I have several camera specifics, can I determine the required resolution to view an image at the size I want? For example, let's say I want a picture of a square painting to be at least ...
2
votes
1answer
318 views

Curved lines in a picture (Photography)

My problem is when I take a picture (a close one) the straight edge looks a little curved. In a standard camera, like a CyberShot. I would like to know if there is some relationship between the ...
2
votes
1answer
2k views

How to determine the field of view for a pinhole camera with given parameters?

I am reviewing some old material I learned years ago and am having trouble figuring this one out. Can somebody confirm that I have done my math correctly, and tell me how I can recover the field of ...
2
votes
0answers
43 views

Calculating the Diameter of Jupiter through Image [closed]

I was trying to calculate the diameter of Jupiter from a picture I took of it. Here's the information I was able to get that I needed to calculate the diameter: Focal Length of Telescope: 1.2 m ...
2
votes
0answers
35 views

What is the shape of the MTF curve in coherent imaging?

For incoherent imaging, the shape of the diffraction-limited MTF curve would look roughly like a triangle, with normalized contrast starting at 1 for zero spatial frequency and decreasing to 0 at the ...
2
votes
0answers
30 views

Searching for a textbook on Imaging

I'm hoping someone can recommend a book that will cover the physics involved in optical range image capture. I have a degree in physics, so I am looking for something on the technical end. To expand, ...
2
votes
0answers
40 views

Determining the spatial imaging resolution based on a pinhole diffraction pattern

I aimed a 780 nm/1mW laser at a 1μm pinhole and took a picture of it using a lens and a CCD camera. The magnification of my imaging system is ~25 times. I wrote some code that takes the image of the ...
2
votes
1answer
153 views

Peak deconvolution [closed]

I need some help understanding how much information I can pull out of this data. I have a sample made up of two materials. Materials A and material B. Then I took a picture of the sample. The two ...
1
vote
1answer
504 views

Photo of reflection in magnifying mirror shows normal magnification. Why?

I just took a picture of myself in one of those magnifying shaving mirrors and in the photo I am unmagnified! Why is this?
1
vote
1answer
9k views

X-ray imaging and diamond

Why doesn't diamond show up in X-ray imaging? Diamond is the hardest substance ever known, and as we know, X-ray radiation is produced when a cathode ray of high frequency hits a very high atomic mass ...
1
vote
1answer
30 views

Wavelength for imaging an ultracold atom?

I was reading Stamper-Kurn's article Experimental Methods in Ultracold Atomic Physics (link). In the imaging section (page 13), he mentions: Cold atoms are conventionally probed by optical imaging....
1
vote
1answer
60 views

Why aren't pictures of Pluto darker than those of other planets?

Just as the intensity of the light from a candle decreases with distance, I would expect the light from the sun to illuminate the distant planets less than the closer ones. However, the pictures of ...
1
vote
1answer
71 views

Optical interferometers resolution

I found this interesting list of optical interferometers: http://en.wikipedia.org/wiki/List_of_astronomical_interferometers_at_visible_and_infrared_wavelengths But I can't understand which is the ...
1
vote
1answer
212 views

why shadows become dark when light intensity increases? [closed]

I observed following phenomena today: in my room with some lightings, there is a stuff toy placed in front of a wall. The ambient lighting doesn't cause any shadow on the wall currently. Scene 1: ...
1
vote
1answer
119 views

Infinite plane wave and ray vectors

I want to clear my mind on one basic optics thing: If I have a point source some distance away from a lens, the position of the image formed can be found using traditional geometrical optics ray ...
1
vote
1answer
47 views

What type of interferometry set up do I need to image a small structure at a distance?

Please forgive me, optics isn't my forte. I'm trying to work out how to image the surface structure of an object at a distance. Considerations are: Monochromatic light- it must be imaged in the ...
1
vote
0answers
21 views

What is vortex row image system in fluid mechanics?

What is vortex row image system in fluid mechanics? I have lot search but I did not find any best answer about this question. Please explain about this topic or give me best link of book or site.
1
vote
1answer
22 views

Why do smaller wavelengths image particles more clearly when the particle size is already big?

Yesterday I scanned an ultrasound phantom that had cylindrical inclusions (1.5mm diameter). When I boosted the ultrasound frequency from 3MHz to 4MHz, these inclusions became much more clear. I ...
1
vote
0answers
21 views

What is the difference between a coherent and an incoherent imaging system? [closed]

Could this please be explained in terms of an abstract system and then an imaging system?
1
vote
0answers
90 views

How can I determine spatial resolution from an Airy disk diffraction pattern?

From introductory optics, the angular resolution of a lens (in radians) can be described by the Rayleigh criterion: \begin{align*} \theta = 1.220 \frac{\lambda}{d} \end{align*} This has its ...
1
vote
0answers
28 views

Imaging and the Electric Field

In this book (pg. 162), it mentioned that conventional lenses only focus propagating waves, thereby creating an imperfect image. In contrast, superlenses focus both propagating and evanescent waves, ...
1
vote
0answers
68 views

Inverse problem for MRI imaging

Background: Recently, I read a paper describing the existence of what are known as "concomitant gradient fields" in MRI. When a linear gradient is applied along one axis, concomitant gradient fields ...
1
vote
1answer
61 views

Can a virtual image created by a mirror have position in front of the mirror?

I dont think so, because then the rays will intersect and the image will be real. Please let me know if you know a case in which a virtual image is formed in front of the mirror.
1
vote
0answers
146 views

Penetration and skin depth in 'metallic' magnetic induction tomography (classical electromagnetism)

Does anyone know how AC magnetic fields behave in 'metallic' magnetic induction tomography (MIT). Do they form a magnetic circuit around a metallic specimen or penetrate through it, or both? This ...
1
vote
0answers
19 views

Conjugated-Phase Matching

I am working on imaging applications of phase-conjugation in optics, in particular phase-conjugation imaging from recorded holograms. I have found several useful sources, but I cannot find a book ...
1
vote
0answers
103 views

3D Surface Related Multiple Elmination (SRME)

Let's assume we are looking at first order multiples of the same surface (i.e no peg leg, etc). I am looking at marine 3D SRME and I am a little confused as to how this works. I understand that in the ...
0
votes
1answer
35 views

Where does this formula for prediction of a multiple wave come from?

On the slide I am reading, it says this: Any surface related multiple can be construced of primaries: $\hspace{5cm}$Multiple = Primary$_1$ (green) + Primary $_2$ (red) $$T_2 = T_1 + \...
0
votes
1answer
75 views

How to determine the angle a camera has to be at to image a desired scene, given the camera parameters?

Reviewing old material I learned years ago, having a hard time rewrapping my head around the relationships in capturing images from a camera. Imagine a scenario with the camera placed on the ground (...