An Approach for Image and Height Calibration for Borescope Based Surface Characterization

When the topology of a surface is characterized using triangulation with a structured light beam, the image quality and mapping charge coupled device (CCD) pixel offset to a height variation assumes utmost importance. A typical optical is adversely affected by the distortions in the images introduced by the optical components. In this specific case, the optical system employs a borescope that introduces distortions visible even to a naked untrained eye. One reason for this is the view angle of the borescope and the other is the presence of the lenses in the borescope. For borescopes to be used for quantitative characterization purposes, these distortions need to be corrected. Mapping the offset in the CCD chip into a height variation is a popular approach for triangulation. In this presentation, we will introduce an algorithm on how we remove the distortions from borescope images, and how we perform a height calibration for determining the surface topology through a borescope based system.