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Edge detection | Edge detection

Key Words: darkfield, diascopic, episcopic, digital imaging, Normarski DIC, gray scale processing, 8-segment LED ring illumination

Definition:Edge detection is a process in digital image analysis that detects changes in light intensity. These changes can be used to determine the depth, size, orientation and surface properties of features within a sample or work piece


Edge detection is a digital image analysis technique that can be applied to images of both 2-D and 3-D samples. An edge can be regarded as the boundary between two dissimilar regions of an image. An edge may result from changes in light absorption (color / shadow), texture etc and, at its simplest, can be identified by recording changes in light intensity over a number of pixels (gray scale processing). For example, if a linear series of pixels recorded light intensities of; 2, 3, 2, 4, 3, 2, 95, 97, 96 an edge or discontinuity would be expected between pixels with recorded intensities of 2 and 95. These pixels may be referred to as 'edge points'.

Digitally analyzing any image for edges involves filtering out unimportant information to leave selected 'edge points'. The detection of subtle edges may be confounded by 'noise' and is dependent on the threshold in pixel change that defines an edge. Nikon uses complex edge detection algorithms in its software to make edge detection simple.


Edge detection is a fundamental process in industrial metrology as it defines the boundary of a feature to be measured. Precision edge detection improves accuracy in on-going process and quality control procedures.


Nikon's NEXIV video measuring systems automatically detect edges using either gray scale (gradient) processing via video edge probes or with its proprietary edge detection algorithm. This enables the detection of minute, low contrast edges that are difficult to detect using gray scale techniques. Detection speeds are amongst the world’s fastest allowing measurement of any work piece with speed and precision.

Edge detection can also be carried out with Nikon's DS-2Mv digital camera in association with E-Max software. This offers advanced edge detection functions, ranging from two-dimensional data processing and image measurements to data storage capabilities.


Please consult your Nikon representative for advice specific to your needs.

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