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Upsampling

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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...

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Related Experiment Video

Updated: Jun 16, 2026

Gain-compensation Methodology for a Sinusoidal Scan of a Galvanometer Mirror in Proportional-Integral-Differential Control Using Pre-emphasis Techniques

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Constant variance enhancement: a digital processing technique.

|February 20, 2010

Summary

This summary is machine-generated.

Constant variance enhancement improves image information extraction by equalizing local variances. This image processing technique uses high-pass filtering and gain adjustment, with differential luminance gain assessing its effectiveness.

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Area of Science:

Image processing
Computer vision
Digital signal processing

Background:

Human visual system's information extraction is limited by image properties.
Image enhancement aims to improve visual information accessibility.

Purpose of the Study:

To introduce and explain constant variance enhancement.
To evaluate the effectiveness of this image enhancement technique.

Main Methods:

High-pass filtering to zero local averages.
Applying a gain factor based on local standard deviation.
Illustrating mathematical stages with visual examples.

Main Results:

Achieved output images with equal local variances.
Introduced differential luminance gain as an enhancement metric.
Evaluated the metric numerically for the presented processing.

Conclusions:

Constant variance enhancement equalizes local image regions.
Differential luminance gain provides a measure of enhancement effectiveness.
Addressed the issue of negative differential luminance gain.