A kind of field calibration and fixed focus method of ptz camera

Abstract

The invention discloses a PTZ camera on-site calibration and focusing method, which belongs to the technical field of computer vision and camera calibration. The method includes step 1: selecting and measuring the reference point of the calibrated field of view; step 2: camera calibration with the focal length fixed; step 3: selection of the key focal length; step 4: automatic acquisition of the non-calibrated field of view reference point; step 5: PTZ camera Online calibration. Aiming at the non-strictly axisymmetric lens, the present invention designs a method that can effectively realize the distortion correction of the non-strictly axisymmetric lens. Since the reference point covering the entire camera field of view is obtained, not only the calibration workload is reduced, but also different areas of the lens can be described. To achieve effective estimation of distortion at all focal lengths, using the angle invariance of the reference point in the field of view in the camera field of view, the focal length is quickly determined by the least square method, and the distortion correction data of each point is obtained by interpolation.

Description

technical field [0001] The invention belongs to the technical field of computer vision and camera calibration, in particular to a method for on-site calibration and focusing of a PTZ camera. Background technique [0002] PTZ (Pan-Tilt-Zoom, PTZ) camera, also known as zoom pan-tilt camera, can automatically adjust and control the focal length, attitude, aperture, etc. It has the characteristics of flexibility, large field of view, and strong adaptability to lighting conditions. Therefore, it has been widely used in various fields such as video surveillance, electronic security, and robot navigation. The PTZ camera is used in the field of visual measurement, which solves the problems of small measurement viewing angle range and fixed viewing angle. It increases the flexibility of the visual measurement system and reduces the number of cameras required. [0003] In order to improve the accuracy of visual measurement, it is often necessary to pre-calibrate the model parameters ...

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Problems solved by technology

However, the above method is mainly suitable for camera calibration when the focal length is fixed, and still cannot solve the parameter calibration problem of PTZ cameras with continuously changing focal length

[0005] Aiming at the problem of PTZ surveillance camera calibration, many calibration methods have been proposed in the prior art. For example, Sinha and Polleveys proposed a method for discrete sampling calibration of PTZ camera zoom parameters (reference [1] SinhaS N and Polleveys M.Pan -tilt-zoom Camera Calibration and High-resolutionMosaic Generation.Computer Vision and Image Understanding.2006,103(3):170-183P); Sarkis and others proposed a method of using moving least squares to establish the camera internal parameter function (reference [ 2] Sarkis M, Senft C and Diepold K.Calibrating an Automatic Zoom Camera With Moving Least Squares.IEEE Transactions on Automation Science and Engineering.2009,6(3):492-503P); Ashraf and Foroosh et al proposed to use non-overlapping field of view PTZ camera self-calibration method (reference [3] Ashraf N and Foroosh H.Robust Auto-calibration of aPTZ Camera with Non-overlapping FOV.In International Conference on Pattern Recognition,Dec.2008:738-748P), in these known Among the methods, some ignore lens distortion, some assume that the change of lens distortion is a linear change with magnification, and some assume that lens distortion satisfies the distortion model. However, for lenses with uneven processing accuracy, lens distortion cannot Described by a simple distortion model

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