A flexible technique for slide projector calibration

摘要

With the development of non-contact measurement in the close range photogrammetry, the use of the slide projector becomes familiar and frequent. In order to take full advantage of the slide projector in the procedures of diverse photogrammetric measurements, the slide projector needs to be calibrated at first. Namely, the intrinsic paramters of the slide projector have to be calibrated in advance. In this paper a flexible technique is proposed to calibrate the slide projector easily. The technique only requires an ordinary slide projector, a camera and a planar grid. The algorithm with 2D direct linear transformation (2D-DLT) and collinear equations is used to calibrate the slide projector. The operation method in detail and the algorithm are addressed systematically and entirely. First, the restricting condition among 2D-DLT parameters is worked out using the correspondence of 2D-DLT and collinear equation. Then, the decomposition of initial values of the slide projector intrinsic and extrinsic parameters using 2D-DLT is deduced. Finally, the slide projector calibration parameters are worked out by the whole adjustment. The feasibility and the exactness of the slide projector calibration technique put forward in this paper are verified by the results of real data.