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Questions tagged [image-processing]

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3 answers
369 views

What is the theoretical limit for image sensors

Telescopes are principaly limited by a diffraction-limit. Does this limit affect the image sensor? The Rubin Observatory LSST Camera, the biggest camera in the world with 3.2 gigapixels is having a ...
0 votes
2 answers
425 views

How can one calculate the velocity of an object that appears as a blur?

Around how could you estimate the speed of an object which appears as a blur to the human eye? And by blur I mean to the extent it is hard to trace or make out. I looked this up but the best I could ...
1 vote
1 answer
2k views

Calculate Modulation Transfer Function from Line Spread Function

I am trying to measure the MTF of a radiology imaging system from a set of CT scans of a phantom. The imaging system is primarily designed for stationary scans so the CT images were low in spatial ...
1 vote
1 answer
50 views

What is the relation between image resolution and Cutoff from 2D FFT functions in frequency space?

This might be dumb, but unfortunately I need some urgent help about Cutoff from 2D FFT functions in frequency space. I am writing my bachelor thesis, near DDL and cannot get a lot of help offline in ...
0 votes
0 answers
23 views

Simple interference confocal microscope

I have the two articles: The first one: First article and The second one: Second article After reading the first article I understood while reading that using the detector A we get confocal ...
2 votes
1 answer
328 views

How to set mask size when apply inverse-FFT to the power spectrum of HAADF-STEM image?

Hello everyone, I want to characterize dislocation in my FIB sample using Titan electron transmission microscopy and I want to use FFT filter to process my HAADF-STEM image with DigitalMicrograph (...
0 votes
0 answers
55 views

Connection between the Modulation Transfer Function (MTF) and Line Spread Function (LSF) in "Hecht - Optics, 5th ed"

I try to understand the derivation of the connection of the MTF and the LSF and found a derivation in the Book "Optics" by Eugene Hecht (5th edition), chapter 11, section 11.3.6. However, ...
0 votes
1 answer
23 views

How to decipher imaging method used in remote sensing images?

I am working on remote sensing for science olympiad (div c) and i am kind of lost on remote sensing image analysis. like how do i look at an image and know it was captured using infrared or microwave ...
1 vote
1 answer
70 views

How do I finde the units of my temporal Fourier transform?

I am trying to extract harmonic motion from series of images. One approach ist to simply take the (discrete) fft: tmp = fft(imageSeries, [], 3); where imageSeries is a stack of black and white images ...
0 votes
1 answer
188 views

What is the input of calculating signal noise ratio (SNR) and detective quantum efficiency (DQE) in estimation of imaging system?

In its definition, the signal noise ratio (SNR) is the ratio of the mean siganl to the standard deviation of the noise. However, for a given picture what is the noise? The detective quantum efficiency ...
28 votes
4 answers
2k views

How specifically does an MRI machine build an image from received radio waves?

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 ...
0 votes
1 answer
260 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, ...
0 votes
2 answers
67 views

On a fundamental level, why is white balance in cameras even necessary?

When searching online about what the white balance setting in cameras does, you'll probably find an answer that goes something like this: When taking a photo, the color of the lightsource might be ...
2 votes
2 answers
2k views

Difference Between Angular Resolution and Spatial Resolution of optical device (Camera)

As per wikipedia angular resolution is the ability of device to capture minute details of an object and is the same definition in case of spatial resolution. Whats the difference Between Angular ...
9 votes
2 answers
5k views

What is meant by 2D fourier transform of an image?

I have some questions about this interesting concept I came across about 2D Fourier transform, please... Firstly, the Fourier transform of a 1D signal (such as a sound recording) is as follows: The ...
0 votes
2 answers
200 views

Myopia far point virtual image

My textbook says that a diverging lens works by rendering the object a virtual image at the myopic eye’s far point. However, wouldn’t the eye then perceive an object farther than its far point at the ...
3 votes
1 answer
380 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.
1 vote
0 answers
27 views

Replica calculation in statistical mechanics

i am reading "Statistical physics of spin glasses and information processing an introduction - Nishimori Hidetoshi", chapter 6, page 119 on image restoration. I tried to understand what ...
18 votes
6 answers
4k 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 ...
1 vote
1 answer
98 views

Is it possible to get a resolution that is better than what is given by the Rayleigh criterion?

I remember reading recently that it is possible to unblur a face that has been blurred by using a computer to process multiple images of the blurred face from different angles. This got me thinking, ...
2 votes
1 answer
227 views

Can an image formed by gravitational lensing be corrected for the inevitable aberration?

Carl Zeiss would not be impressed with your average gravitational lens. Compared with familar optical lenses that are generally used to form sharp undistorted images, gravitational lenses make quite a ...
3 votes
0 answers
37 views

Estimating the focus plane of camera via thin lens equation [closed]

I have a camera that outputs a JSON file for every image taken. In the JSON file, I can find camera-specific and also the photo-specific acquisition parameters used. The issue is I wish to estimate ...
0 votes
0 answers
204 views

Is it possible to change the location of a virtual image without using moving lenses?

The benefit of a head-up display is primarily in reducing the time required by the user to refocus their eyes from the head-down display to the head-up surroundings. In applications such as cars, the ...
3 votes
3 answers
19k 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?
1 vote
1 answer
74 views

Satellite image anomaly

This is a satellite image of somewhere in West Texas: See the localized Red-Green-Blue feature on the road? What could have caused this?
167 votes
9 answers
25k 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 ...
0 votes
1 answer
66 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, ...
23 votes
7 answers
7k 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.
1 vote
1 answer
274 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?
0 votes
0 answers
38 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?
3 votes
1 answer
406 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 ...
0 votes
1 answer
28 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 ...
0 votes
1 answer
186 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 ...
0 votes
2 answers
270 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 ...
2 votes
1 answer
460 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 ...
2 votes
1 answer
290 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 ...
1 vote
2 answers
146 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?
0 votes
0 answers
61 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 ...
0 votes
1 answer
92 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 ...
1 vote
0 answers
168 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?
1 vote
2 answers
310 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 ...
2 votes
1 answer
322 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 ...
0 votes
1 answer
2k 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 ...
1 vote
1 answer
176 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 ...
1 vote
2 answers
2k 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 ...
0 votes
1 answer
1k 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: ...
5 votes
1 answer
3k views

Fresnel transform

How is it possible to encrypt multiple images using fresnel transform and inverse the operation to de-multiplex those images?
14 votes
5 answers
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 ...
0 votes
4 answers
11k 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 ...
3 votes
2 answers
915 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 ...