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Skin Res Technol. 2011 Aug;17(3):339-47. doi: 10.1111/j.1600-0846.2011.00504.x. Epub 2011 Feb 22.

Chromatic aberration correction: an enhancement to the calibration of low-cost digital dermoscopes.

Author information

1
School of Computing Science, Simon Fraser University, Burnaby, BC, Canada.

Abstract

BACKGROUND/PURPOSE:

We present a method for calibrating low-cost digital dermoscopes that corrects for color and inconsistent lighting and also corrects for chromatic aberration. Chromatic aberration is a form of radial distortion that often occurs in inexpensive digital dermoscopes and creates red and blue halo-like effects on edges. Being radial in nature, distortions due to chromatic aberration are not constant across the image, but rather vary in both magnitude and direction. As a result, distortions are not only visually distracting but could also mislead automated characterization techniques.

METHODS:

Two low-cost dermoscopes, based on different consumer-grade cameras, were tested. Color is corrected by imaging a reference and applying singular value decomposition to determine the transformation required to ensure accurate color reproduction. Lighting is corrected by imaging a uniform surface and creating lighting correction maps. Chromatic aberration is corrected using a second-order radial distortion model.

RESULTS:

Our results for color and lighting calibration are consistent with previously published results, while distortions due to chromatic aberration can be reduced by 42-47% in the two systems considered.

CONCLUSION:

The disadvantages of inexpensive dermoscopy can be quickly substantially mitigated with a suitable calibration procedure.

KEYWORDS:

calibration; chromatic aberration; color and lighting correction; digital dermoscopy

[Indexed for MEDLINE]

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