Calibration device and calibration method for outer parameters of camera for photogrammetry

Abstract

The invention discloses an outer parameter calibration device and a calibration methodof a camera for photogrammetry. The calibration device is composed of target mark post, a centering rod, a leveling mechanism and a datum mark. The calibration method comprises the following steps: firstly, adjusting a camera to point a target to be measured, embedding four datum points in a camera pointing direction; measuring a coordinate with high precision in a reference coordinate system; adjusting the centering rod of the calibration device to be vertical in accordance with the designed size of the calibration device; when the leveling mechanism is horizontally placed, and deriving the coordinate of a mark point in the reference coordinate system; secondly, shooting a landmark image on a calibration device through a camera, extracting a mark point coordinate by adopting an elliptic fitting algorithm, and resolving the outer parameters of the camera and the reference coordinate system to complete calibration by combining the parameter calibration results of the coordinate and the camera in the reference coordinate system. Compared with the prior art, the scheme is applicable to a three-dimensional calibration occasion of a plurality of cameras in a wide measurement scope, and has the characteristics of being convenient to operate and high in calibration precision.

Description

technical field [0001] The invention relates to the technical field of camera calibration for photogrammetry, in particular to a camera external parameter calibration device and calibration method for photogrammetry. Background technique [0002] Photogrammetry is widely used in 3D model reconstruction, object surface size measurement, target position and attitude measurement, space docking, medical diagnosis and sports recovery and other fields. In order to obtain the three-dimensional information of the target, photogrammetry generally requires two or more cameras to perform intersection measurement to form a stereo vision measurement system. Therefore, calibrating the position and attitude of multiple cameras in the unified reference coordinate system becomes a key to the measurement accuracy of the measurement system. influencing factors. The external parameters of the camera in the present invention are the rotation matrix and translation vector of the camera relative ...

AI Technical Summary

Problems solved by technology

Traditional camera parameter calibration is more typical. Youzhang proposed a method based on coplanar calibration reference objects. This method allows the coplanar reference objects to move freely in the field of view. By acquiring multiple high-quality calibration images, the internal parameters of the camera are calibrated. , fixedly shooting a certain frame, you can calibrate the external parameters of the camera relative to the fixed calibration reference coordinate system at this time, the calibration process of this method is simple, and the requirements for the target are low, but this method cannot realize multiple plane coordinate systems and reference coordinates The unification of the system is only applicable to camera calibration occasions with a small measurement range; in addition, there is a full field of view calibration using the auxiliary camera, which requires the auxiliary camera to simultaneously collect the control points of the calibration reference system and the reference system. image, which requires the auxiliary camera to have a larger field of view, so that its imaging resolution will be relatively low, which will affect the accuracy of calibration; the auxiliary camera in the above calibration method can be replaced by a laser tracker (Laser Tracker). The instrument can measure space points with high precision. For the case of a large "full field of view", using the laser tracker instead of the auxiliary camera for full field of view calibration is beneficial to improve the calibration accuracy, but the cost of the laser tracker is high, and The calibration process is more cumbersome

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