Questions tagged [image-processing]

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40 views

Is Sentinel able to obtain wave spectrum by interferometric Data?

I have recently read many articles on recovering wave spectrum from the AT-INSAR image spectrum (through interferometric images). However, it is not clear to me whether Sentinel is a viable option, ...
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1answer
45 views

Erosion vs Dilation [closed]

What exactly is erosion and dilation? What is the difference between them in digital image processing? Can anyone explain the process that is happening behind the scenes of erosion and dilation?
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25 views

Does the recent picture of the black hole have a native resolution?

Can the resolution be measured in pixels? If so, what is the pixel resolution?
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1answer
218 views

Why EHT have to use Fourier transform to process the image?

I read that Fourier transform is a mathematical tool to deconstruct a wave taken from a source into basic sine and cosine waves, since visible light coming from the M87 accretion disk will be obscured ...
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23 views

Magnification Factor

so I have to write a lab report about an experiment I did in class with using the equation for magnification factor = known length/measured length (this was used to find the length of a bridge ...
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1answer
43 views

What does the width of the 2D Fourier transform of a speckle pattern mean?

Speckle patterns can be studied by capturing an image of the speckle pattern produced on a rough surface when light from a laser passes through an aperture stop. When analysing this speckle pattern, ...
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1answer
13 views

What operation is used to construct single image of dual-energy x-ray scanned object?

I know that for dual-energy x-ray screening, two different energies are used which produces two distinct images. I want to know how these images are combined to result in a single image. I know that ...
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1answer
36 views

Differnce between color image and false color image

I am currently trying to understand the difference between true colour and false colour. So true colour to me is what we perceive as a person, i.e I take a photo and the photo is a true colour image ...
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2answers
77 views

Spatial frequency and high contrast imaging

I am having a issue with a question with regards to how spatial frequency and high contrast are related. Explain how high contrast resolution of an imaging system may be expressed in terms of a ...
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1answer
127 views

Rectilinear image projection in image stitching [closed]

For the pinhole camera model, the mapping from 3D to 2D coordinates is described by a perspective projection(rectilinear projection). However for the image stitching application, perspective ...
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1answer
88 views

From K-space to wavelets in compressed SENSE MRI (cSENSE)

In compressed sensing MRI (cSENSE MRI) technology the idea seems to entail sampling from the Fourier domain (k space) in a way that, when transformed to the wavelet domain ("sparsification"), the ...
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2answers
67 views

How does ultrasound work? How is the signal processed?

Why is ultrasound 2D? Is there a way of making ultrasound 3D without piecing together 2D? How close is ultrasound to sonar?
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0answers
32 views

Defraction limits of muli-image super resolution for satellites

Is it possible to increase the resolution of satellite imagery with multiple passes through the use if multi-image super resolution algorithms? I would imagine that probably the optical systems are ...
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1answer
26 views

How to find bright fringe peaks from an image?

I am working on the Zeeman Effect lab experiment. It involves diffraction and splitting of circular fringes due to magnetic fields. I have taken pictures of the interference pattern, described by a ...
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0answers
80 views

What is the pixel size of Hitachi SU8230 SEM at 100k magnification?

I have a publication showing an SEM micrograph taken by Hitachi SU8230 model. Is there anyway to learn the pixel sizes?
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2answers
84 views

Defocusing the eye and computer monitors

Im not sure whether this is the right site to post this on, but here goes : We are often told to relax our eyes when using computer/tv screens for extended periods of time. I often find that I forget ...
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1answer
455 views

Is it possible to read vinyl records with a camera? [closed]

As far as I know a vinyl record stores information as surface irregularities in a spiral on a plastic disk. In theory is it possible to read this information based on a single or multiple photos of ...
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1answer
94 views

Question about motion blur [closed]

My goal is to model motion blur for a supposedly simple case: Consider a 1 dimensions image I of a scene. Also consider that the scence is in relative motion to the camera. This means that at time ...
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2answers
103 views

Can you tell the actual size of an object in a photo by just measuring the image (with some reference objects)?

For example, you took a photo of the surface of a table, which is a rectangle. You also know the length of the table, say 50 inches. In the photo, the surface appears as a trapezoid (whose parallel ...
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1answer
761 views

How to calculate the size of object in pixels, knowing the camera properties?

I'm trying to calculate the size of an object in pixels in an image, when I have these information: ...
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5answers
3k views

Is there any advantage in stacking multiple images vs a single long exposure?

Suppose I have a source object that is not time varying, to be concrete let's say it's a galaxy. Is there anything additional that can be learned or done with multiple short exposure images of exactly ...
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7answers
5k views

Why are light rays able to cross each other?

See the image first: Why are light rays able to cross each other? Air isn't able to.
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5answers
2k views

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 ...
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3answers
7k views

How do I read a scanning electron microscopy (SEM) image?

I'm trying to figure out the magnification of this image. Can anyone explain how to read the numbers at the bottom? What do they mean and how can I determine the magnification from them?
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1answer
1k views

Why do we see an inverted image in a spoon when kept far from our face with concave side towards our face?

We see a virtual inverted image whereas in case of concave mirror we can see a virtual image which is erect.
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2answers
752 views

Error calculation of physical quantities calculated from a image

I have an assignment related with the physical characterization of some images taken in a SEM (microscope). I have images of some salt grains and the goal is to find the area and perimeter of those ...
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1answer
181 views

Calculation Of Resulting 2D Image After Lens

This is a tough question! I would like to calculate how an image (a real 2D photograph) looks if I place a lens at a certain distance d1 from it and I observe it at a certain distance $d_2$. It is ...
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1answer
262 views

What do certain pixels in the Fourier transform of a 2D image represent?

I understand the 1D Fourier transform but I don't have any experience with the 2D version so there are a couple of things I'm wondering about. If you take the Fourier transform of a 2D image you end ...
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0answers
331 views

Difference between Fast Fourier transform of a 2D lattice image and its reciprocal lattice image

I have constructed an image of nXn pixels with each pixel having values either 0 or 1. I have added circles in the form of square lattice with definite period a. The image basically looks like (a). ...
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3answers
109 views

Why are $L^2$ spaces preferred over $L^1$ spaces in some applications?

In various applications where we are dealing with electromagnetic or acoustic waves, such as medical imaging, we use the space $L^2$ or the related Sobolev space $W^{1,2}$. I have never seen a reason ...
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0answers
469 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 ...
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3answers
2k views

Is it possible that a person with myopia will see a blurry picture as normal? [duplicate]

I am trying to process an image in good quality to appear blurred to a normal person and good to a person suffering from myopia as seen in this source. Is it possible that a picture that is blurry ...
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1answer
2k 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: ...
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1answer
81 views

Given a size of a known object in the image, how can we calculate the size of other objects in the same image?

The question considers a very specific scenario in which we have an image with let us say, two rectangle objects. We know width and height of one object. How can we calculate the dimensions of the ...
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1answer
1k views

How to extract depth of a pixel from an image?

I'll have a few pictures that show the same scene, but only a few things move around a little bit. Now I don't have an information about any size in real life but I'd like to extract a scaling factor ...
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3answers
2k views

How to recover an unfocussed image

If the lenses in a camera are not set correctly, the intended subject will be "out of focus" in the resulting image. There seems to be no loss of information here. The photons are just steered to the ...
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1answer
213 views

Why do we need the eigenvalue? [closed]

Now I'm trying to review about the image noise. http://people.csail.mit.edu/celiu/denoise/estnoise/and I have found an article about the eigenvalue. Why do we need the eigenvalue, what is its use?
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0answers
72 views

What is the concept of phase congruency?

I am beginner in signal processing. I am studying the importance of phase in signals. I want to know about Phase Congruency, but there is very little information available on internet. So can anybody ...
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0answers
192 views

Measuring typical distance between patches using 2D Fourier Transform

I need to extract information about the typical distance between the black patches in an image like the one I attached here. I tried to perform 2D FFT on it (using OpenCF fdt function in Python), but ...
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4answers
2k views

How to measure the size of a laser dot?

I'm not a physicist, that's why I'm asking you if there is maybe an easy way (e.g. a mathematical law) to measure the size of a laser dot, or its diameter. The setup It contains a laser, a high ...
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1answer
276 views

What makes a system linear?

Lately I have been interested in Image Processing, and I started by following this course: https://class.coursera.org/digital-001, which is quite awesome in my opinion. But in weeks 2, Linear Shift-...
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3answers
2k views

Verifying radiation measurement smart phone applications

I've stumbled upon a strange class of Android applications lately. (And I'm sure such applications are available for other platforms too.) These apps claim the ability of detecting radiation. The ...
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2answers
248 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 ...
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9answers
19k views

Could Legolas actually see that far?

The video “How Far Can Legolas See?” by MinutePhysics recently went viral. The video states that although Legolas would in principle be able to count $105$ horsemen $24\text{ km}$ away, he shouldn't ...
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4answers
5k views

Phase and amplitude information of an image

By applying Fourier Transform to an image we can get its magnitude as well as phase spectrum. A magnitude spectrum describes how various frequencies are attenuated and accentuated in that image but ...
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1answer
933 views

Image Reconstruction:Phase vs. Magnitude

Figure 1.(c) shows the Test image reconstructed from MAGNITUDE spectrum only. We can say that the intensity values of LOW frequency pixels are comparatively more than HIGH frequency pixels. $$ f(x,y)=...
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3answers
1k views

How specifically does an MRI machine build an image from received radio waves? [on hold]

Unlike the excellent Wikipedia page on ultrasound imaging, the one on MRI only explains the principle theory behind MRI - that oscillating strong magnetic fields cause water molecules to emit ...
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1answer
179 views

How do they draw collision pictures in Atlas?

Is the picture below a simulation? How to they draw these pictures? The picture is from here.
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2answers
2k views

How do you define an aperture for seismic data processing?

Lets consider this in marine seismic processsing. I am assuming you know what a first order primary reflection is, if not, I can define it. Ok, so if we were to have a source $(S)$ and receiver $(R)$...
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0answers
351 views

Maximum-Entropy Method deconvolution implementation?

I am looking for an implementation of the Maximum Entropy Method for image deconvolution, ideally in MATLAB or Mathematica. I'm trying to reconstruct an image from fringe visibilities, as is often ...