Fast and flexible calibration of a phase-based 3-D imaging system by uneven fringe projection

Abstract

Phase-based 3-D fringe projection imaging systems have been widely studied because of the advantages of fullfield, high accuracy, fast acquisition and automatic processing. The calibration of phase-based 3-D systems is an important procedure, which builds up the relationship between the obtained absolute phase map and the depth information. In this paper, a fast and flexible calibration method for phase-based 3-D imaging systems is presented based on an uneven fringe projection method. The relationship between the measured phase and the object's depth is linear and independent of pixel position, so it is possible to calibrate the 3-D imaging system by using discrete markers (with known separation) on a white plate. Projecting uneven fringe pattern sets onto the plate can calculate the absolute phase of each marker. At the same time, the depth of the markers can be obtained by general camera calibration methods. Therefore, the linear relationship between the measured phase and the depth can be determined. The proposed method was applied to calibrate an existing phase-based 3-D imaging system which utilizes the uneven fringe projection technique. The entire calibration procedure does not require accurate movement of a reference plane within the measurement volume. The calibrated system was evaluated by measuring an accurately positioned white plate. Experimental results show that the proposed calibration method can easily build up an accurate relationship between the absolute phase and the depth information.