Precise 3-D Measurement using Uncalibrated Pattern Projection

Three-dimensional measurement methods using structured light projection enable accurate depth measurements by decoding the disparity between the projector-camera pair from an observed pattern. However, actual projection devices have various systematic error sources that distort the structured light pattern, directly affecting the accuracy of 3-D measurements. We propose a new method of measuring depth that is not affected by the systematic errors in the projected pattern. In our method, the image of a pattern projected onto a plane is referenced to cancel errors. Based on the invariance of the cross-ratio under perspective projections, depth is obtained from the disparity determined on the referenced image. In experiments, our method removed the systematic errors and improved the accuracy of depth measurement without any extra calibration or measurement.