Projector Calibration in a Two-Layer Flat Refractive Geometry for Underwater Imaging.

In underwater imaging we observe objects in the water through a flat glass interface which defines a two-layer flat refractive geometry. Using structured light for underwater 3D imaging requires that both camera and projector are calibrated, which is a difficult task. In this paper we discuss how to calibrate a projector for underwater imaging under a two-layer flat refractive geometry. We propose to model the projector as an inverse camera which enables the use of known procedures for camera calibration in flat refractive geometry. We discuss how to efficiently collect the calibration data using only a planar calibration board and an uncalibrated camera. Performed experiments show that the results of projector calibration are comparable to the results of camera calibration making it highly applicable in practice.