Abstract
Abstract. Chromatic aberration in colour digital camera imagery can affect the accuracy of photogrammetric reconstruction. Both longitudinal and transverse chromatic aberrations can be effectively modelled by making separate measurements in each of the blue, green and red colour bands and performing a specialized self-calibrating bundle adjustment. This paper presents the results of an investigation with two aims. The first aim is to quantify the presence of chromatic aberration in two sets of cameras: the six individual cameras comprising a Ladybug5 system, calibrated simultaneously in air; and four GoPro Hero 5 cameras calibrated independently under water. The second aim is to investigate the impacts of imposing different constraints in the self-calibration adjustment. To this end, four different adjustment cases were performed for all ten cameras: independent adjustment of the observations from each colour band; combined adjustment of all colour bands’ observations with common object points; combined adjustment of all colour bands with common object points and common exterior orientation parameters for each colour band triplet; and combined adjustment with common object points and certain common interior orientation parameters. The results show that the Ladybug5 cameras exhibit a small (1-2 pixel) amount of transverse chromatic aberration but no longitudinal chromatic aberration. The GoPro Hero 5 cameras exhibit significant (25 pixel) transverse chromatic aberration as well as longitudinal chromatic aberration. The principal distance was essentially independent of the adjustment case for the Ladybug5, but it was not for the GoPro Hero 5. The principal point position and precision were both affected considerably by adjustment case. Radial lens distortion was invariant to the adjustment case. The impact of adjustment case on decentring distortion was minimal in both cases.
Highlights
1.1 BackgroundColour digital cameras are routinely used to make threedimensional measurements from imagery using photogrammetric methods for a vast range of applications
The independent adjustments (Case 1; Figure 4a) show the existence of longitudinal chromatic aberration as the Principal distance (PD) differ between the bands
A set of self-calibration experiments on two types of colour digital cameras has been performed to quantify the amount of chromatic aberration present and to examine the impacts of various types of geometric constraints
Summary
1.1 BackgroundColour digital cameras are routinely used to make threedimensional measurements from imagery using photogrammetric methods for a vast range of applications. As reviewed by Luhmann et al (2006), several means exist to produce colour imagery with solid-state imaging sensors. Colour filters arrays such as the Bayer filter are the most common. It is well known that the imagery captured with colour digital cameras can be affected by imaging distortions, including chromatic aberration. Chromatic aberration is caused by the dispersion of light by the lens assembly. Longitudinal chromatic aberration results in a wavelength-dependent focal length where the focal length increases with wavelength (Ray, 1994). Transverse chromatic aberration causes wavelength dependence of radial lens distortion (Luhmann et al, 2006)
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