Ryusuke Sagawa

Single colour one-shot scan using modified penrose tiling pattern

In this study, the authors propose a new technique to achieve one-shot scan using single colour and static pattern projector; such a method is ideal for acquisition of moving objects. Since projector–camera systems generally have uncertainties on retrieving correspondences between the captured image and the projected pattern, many solutions have been proposed. Especially for one-shot scan, which means that only a single image is required for shape reconstruction, positional information of a pixel of the projected pattern should be encoded by spatial and/or colour information. Although colour information is frequently used for encoding, it is severely affected by texture and material of the object and leads unstable reconstruction. In this study, the authors propose a technique to solve the problem by using geometrically unique pattern only with black and white colour that further considers the shape distortion by surface orientation of the shape. The authors technique successfully acquires high-precision one-shot scan with an actual system.

Phase Estimation of a Single Quasi-Periodic Signal

We propose a method for phase estimation of a single non-parametric quasi-periodic signal. Assuming signal intensities should be equal among samples of the same phase, such corresponding samples are obtained by self-dynamic time warping between a quasi-periodic signal and a signal with multiple-period shifts applied. A phase sequence is then estimated in a sub-sampling order using an optimization framework incorporating 1) a data term derived from the correspondences and 2) a smoothness term of the local phase evolution under 3) a monotonic-increasing constraint on the phase. Such a phase estimation is, however, ill-posed because of combination ambiguity between the phase evolution and the normalized periodic signal, and hence can result in a biased solution. Therefore, we introduce into the optimization framework 4) a bias correction term, which imposes zero-bias from the linear phase evolution. Analysis of the quasi-periodic signals from both simulated and real data indicate the effectiveness and also potential applications of the proposed method.