Abstract
The stereo-vision system plays an increasingly important role in various fields of research and applications. However, inevitable slight movements of cameras under harsh working conditions can significantly influence the 3D measurement accuracy. This paper focuses on the effect of camera movements on the stereo-vision 3D measurement. The camera movements are divided into four categories, viz., identical translations and rotations, relative translation and rotation. The error models of 3D coordinate and distance measurement are established. Experiments were performed to validate the mathematical models. The results show that the 3D coordinate error caused by identical translations increases linearly with the change in the positions of both cameras, but the distance measurement is not affected. For identical rotations, the 3D coordinate error introduced only in the rotating plane is proportional to the rotation angle within 10° while the distance error is zero. For relative translation, both coordinate and distance errors keep linearly increasing with the change in the relative positions. For relative rotation, the relationship between 3D coordinate error and rotation angle can be described as the nonlinear trend similar to a sine-cosine curve. The impact of the relative rotation angle on distance measurement accuracy does not increase monotonically. The relative rotation is the main factor compared to other cases. Even for the occurrence of a rotation angle of 10°, the resultant maximum coordinate error is up to 2000 mm, and the distance error reaches 220%. The results presented are recommended as practice guidelines to reduce the measurement errors.
Highlights
In recent years, the stereo-vision system has been used widely in many fields, e.g., industrial manufacturing and inspection [1,2,3,4], experimental mechanics [5,6,7,8], structural health monitoring [9,10,11], medical diagnosis [12] and aerospace engineering [13,14,15]
To obtain accurate 3D information, the two cameras in the stereo-vision system should remain stationary during the whole test period
When the stereo-vision systems are employed in autonomous land navigation [20], the road roughness can cause unpredictable camera movements
Summary
The stereo-vision system has been used widely in many fields, e.g., industrial manufacturing and inspection [1,2,3,4], experimental mechanics [5,6,7,8], structural health monitoring [9,10,11], medical diagnosis [12] and aerospace engineering [13,14,15]. Reu [35] presented a study of the influence of calibration errors on the uncertainty in 3D position and object motion for the stereo-DIC system using the Monte Carlo approach This “black-box” method lacks the support of an analytically derived model. Reu [35] presented a study of the influence of calibration errors on the uncertainty in 3D position and object motion for the stereo-DIC system using the Monte C3 oafrl1o7 approach CTohnetcroinbutrtiibountsioanrseatrheatthtahtethcealccaulclautliaotniomn omdoedlselosfo3f D3Dcocooordrdininaatetessaannddddiissttaannccee mmeeaassuurreemmeenntt eerrrroorr aarree ddeerriivveedd bbyy ccoonnssiiddeerriinngg tthhee iiddeennttiiccaall aanndd rreellaattiivvee mmoovveemmeenntt. SSoommee ssttrraatteeggiieess aarree pprrooppoosseedd ttoo rreedduuccee tthhee mmeeaassuurreemmeenntt eerrrroorrss ccaauusseedd bbyy ccaammeerraa mmoovveemmeenntt. From Equation (2), P(Xw, Yw, Zw) in the world coordinate system can be derived as
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