High-precision camera distortion measurements with a "calibration harp".

Area of Science:

• Optics and Photonics
• Computer Vision
• Metrology

Background:

• Traditional digital camera distortion measurement relies on flat patterns, which are difficult to fabricate and validate for flatness.
• This limitation restricts the achievable precision in measuring lens distortion.
• Existing methods may lead to internal compensation errors in global camera calibration algorithms.

Purpose of the Study:

• To develop a high-precision measurement tool for digital camera distortion.
• To introduce a novel method that overcomes the limitations of traditional flat patterns.
• To enable objective and reliable evaluation of distortion correction algorithms and camera calibration.

Main Methods:

• Development of a "calibration harp" using precisely stretched straight lines (strings) as an alternative to flat patterns.
• Implementation of algorithms to automatically compute two complementary lens distortion measurements from harp photographs.
• Evaluation of the method's precision using images corrected by state-of-the-art algorithms and popular software.

Main Results:

• Demonstrated sub-pixel precision (2/100 pixels) in distortion measurement using the calibration harp.
• The harp provides an objective and reliable way to assess the performance of distortion correction techniques.
• The method facilitates the selection of appropriate distortion models for global camera calibration, reducing inherent errors.

Conclusions:

• The calibration harp offers a significant advancement in high-precision camera distortion measurement.
• This technique enhances the automation, reliability, and precision of various distortion correction and camera calibration methods.
• The developed method provides a robust tool for scientific and industrial applications requiring accurate camera metrology.