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A one-dimensional calibration object consists of three or more collinear points with known relative positions. It is generally believed that a camera can be calibrated only when a 1D calibration object is in planar motion or rotates around a ¯ xed point. In this paper, it is proved that when a multi-camera is observing a 1D object undergoing general rigid motions synchronously, the camera set can be linearly calibrated. A linear algorithm for the camera set calibration is proposed，and then the linear estimation is further re¯ ned using the maximum likelihood criteria. The simulated and real image experiments show that the proposed algorithm is valid and robust.-A one-dimensional calibration object con sists of three or more points with Conic kno wn relative positions. It is generally believe d that a camera can be calibrated only when a 1D ca libration object is in planar motion or rotates around a