<title>Vision metrology with superwide-angle and fish-eye optics</title>

Abstract

Photogrammetrists have generally made use of wide or super wide angle rectilinear lenses that are designed to reproduce straight lines in the object space as straight lines in the image space. This paper investigates the use of fish-eye optics as an alternative to the conventional super wide-angle lens for vision metrology. The fish-eye design, whilst still retro-focus in construction, rejects the design constraints of rectilinear imaging in exchange for more even illumination across the image format and the expectation of reduced lens aberration effects. By means of a series of practical comparisons, this paper will investigate the target image performance and practical usage of two off-the-shelf 35mm camera mount lenses, namely an 18mm focal length super wide-angle rectilinear lens and a 16mm quasi fish-eye lens. Investigations include: an image quality assessment of retro-target images of differing sizes; an analysis of the variation in retro-target image quality with lens aperture; the influence of the different lenses on the internal consistency of highly over-determined self-calibrating multi-station photogrammetric networks and; an accuracy test between networks obtained with each lens type against measurement of the same targets using an industrial theodolite system.

Oblique photogrammetry with visible and thermal images of active lava flows

“…Visible images were acquired with a Canon EOS 300D (3072×2048 effective pixels) fitted with a fixed-focus 28 mm lens, the imaging geometry of which had been precalibrated in a laboratory (Robson et al 1999). Thermal images were obtained with a FLIR ThermaCAM S40 which provides a horizontal field of view of 24°(similar to that of a 50-mm lens on a digital SLR with an APS dimensioned sensor).…”