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Related Concept Videos

Aliasing01:18

Aliasing

Accurate signal sampling and reconstruction are crucial in various signal-processing applications. A time-domain signal's spectrum can be revealed using its Fourier transform. When this signal is sampled at a specific frequency, it results in multiple scaled replicas of the original spectrum in the frequency domain. The spacing of these replicas is determined by the sampling frequency.
If the sampling frequency is below the Nyquist rate, these replicas overlap, preventing the original signal...
Bandpass Sampling01:17

Bandpass Sampling

In signal processing, bandpass sampling is an effective technique for sampling signals that have most of their energy concentrated within a narrow frequency band. This type of signal is known as a bandpass signal. The key principle of bandpass sampling involves sampling the signal at a rate that is greater than twice the signal's bandwidth to prevent aliasing.
A bandpass signal has a spectrum with a lower frequency limit, denoted as ω1, and an upper frequency limit, denoted as ω2. The spectrum...
Upsampling01:22

Upsampling

Managing signal sampling rates is essential in digital signal processing to maintain signal integrity. A decimated signal, characterized by a reduced frequency range due to its lower sampling rate, can be upsampled by inserting zeros between each sample. This upsampling process expands the original spectrum and introduces repeated spectral replicas at intervals dictated by the new Nyquist frequency. To refine this zero-inserted sequence, it is passed through a lowpass filter with a cutoff...
Downsampling01:20

Downsampling

When considering a sampled sequence with zero values between sampling instants, one can replace it by taking every N-th value of the sequence. At these integer multiples of N, the original and sampled sequences coincide. This process, known as decimation, involves extracting every N-th sample from a sequence, thereby creating a more efficient sequence.
The Fourier transform of the decimated sequence reveals a combination of scaled and shifted versions of the original spectrum. This...
Spherical Coordinates01:23

Spherical Coordinates

Spherical coordinate systems are preferred over Cartesian, polar, or cylindrical coordinates for systems with spherical symmetry. For example, to describe the surface of a sphere, Cartesian coordinates require all three coordinates. On the other hand, the spherical coordinate system requires only one parameter: the sphere's radius. As a result, the complicated mathematical calculations become simple. Spherical coordinates are used in science and engineering applications like electric and...
Sampling Methods: Overview01:06

Sampling Methods: Overview

A sample refers to a smaller subset representative of a larger population. In analytical chemistry, studying or analyzing an entire population is often impractical or impossible. Therefore, samples are used to draw inferences and generalize the whole population. The sampling method selects individuals or items from a population to create a sample. Standard sampling methods include random, judgemental, systematic, stratified, and cluster sampling. 
In analytical chemistry, the choice of sampling...

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Applying Hyperspectral Reflectance Imaging to Investigate the Palettes and the Techniques of Painters
07:05

Applying Hyperspectral Reflectance Imaging to Investigate the Palettes and the Techniques of Painters

Published on: June 18, 2021

Spectral sharpening by spherical sampling.

Graham D Finlayson1, Javier Vazquez-Corral, Sabine Süsstrunk

  • 1School of Computing Sciences, University of East Anglia, Norwich, UK.

Journal of the Optical Society of America. A, Optics, Image Science, and Vision
|July 4, 2012
PubMed
Summary
This summary is machine-generated.

This study introduces spherical sampling for spectral sharpening, improving color constancy models by optimizing sharp sensors. This method enhances accuracy in modeling light-surface interactions across multispectral data.

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Area of Science:

  • Color Science
  • Computational Imaging
  • Computer Vision

Background:

  • Traditional color constancy models use von Kries adaptation, applying scaling factors to cone responses.
  • Recent research proposes applying scaling factors to 'sharp sensors,' which are linear combinations of cone responses with narrower support.

Purpose of the Study:

  • To generalize the computational approach to spectral sharpening.
  • To introduce spherical sampling for enumerating cone response linear combinations.
  • To find optimal sharp sensors minimizing various error measures and extend the method to multispectral imaging.

Main Methods:

  • Introduced spherical sampling to systematically explore linear combinations of cone responses.
  • Developed methods to identify optimal sharp sensors by minimizing error metrics like CIE Delta E and color ratio stability.
  • Extended the spherical sampling paradigm to the multispectral domain for modeling light-surface interactions.

Main Results:

  • Spherical sampling provides a principled way to enumerate all linear combinations of cones.
  • Optimal sharp sensors were identified, outperforming previous methods in minimizing color errors.
  • The extended multispectral approach demonstrated improvements over the state of the art in modeling spectral signals.

Conclusions:

  • Spherical sampling is a powerful tool for advancing spectral sharpening techniques in color science.
  • The generalized approach offers enhanced accuracy and robustness for color constancy and spectral analysis.
  • This work provides a foundation for more sophisticated models of color perception and light-surface interactions.