Digital holography has high potentials for future 3D imaging and display technology. Due to the capability of recording and projecting realistic 3D images, holography has been extensively studied for decades. However, the requirement of a reference beam in interferometric systems and a limited number of pixels in existing spatial light modulators have been major obstacles for the practical applications of 3D holography technology. Recently, the field of wavefront shaping, or the study of controlling multiple scattering of light, has emerged with numerous interesting applications in digital holography. In this review, we introduce the principles of multiple light scattering in complex media and highlight recent achievements to overcome the limitation in conventional 3D holography by exploiting multiple light scattering. The complexity of multiple light scattering, which had been regarded as a major barrier for conventional optical systems, can provide reference-free 3D holographic imaging and 3D holographic display with several advantages.
Inspired by pioneering work on modern light field displays, we developed a prototype display in which three liquid crystal display (LCD) panels are stacked in front of a backlight. The stacked LCD panels constitute a set of semi-transparent layers, which modulate the out-going light rays. Even though only three layers are used, this display can emit a light field, i.e., a dense set of many multi-view images, in different viewing directions simultaneously. We established a process pipeline from capture to display of the light field of a real 3-D scene. We analyzed the amount of pop-out and motion parallax that can be presented by the display using a given light field data. We used a light field camera (Lytro Illum) and a multi-view camera (ViewPLUS ProFUSIOIN 25) to capture the light field, which was then factorized into layer representations to be displayed. We show several successful results using our prototype display.
We propose a new method that obtains an inverse light transport matrix suitable for radiometric compensation; it creates seamless projection-based displays on unknown 3D structures. We extend the theory of inverse light transport to support uncalibrated projector-camera systems in which the optical axes of the projector and the camera are not aligned. The inverse light transport matrix consists of the inverse matrices of direct light transport matrix and inter-reflection matrix. Given that direct and inter-reflection matrices are separated from the light transport matrix, the inverse inter-reflection matrix is computed by Neumann inverse series. The proposed method introduces compressed sensing to optimally estimate the inverse direct light transport matrix from the sets of projector illumination patterns and the camera responses from which the global components are canceled by the inverse inter-reflection matrix. We visualize the matrix elements of the various light transport matrices generated by our approach to examine its performance. We demonstrate compensation trials that compare the proposed method with existing methods. Our experiments confirm that our method offers excellent projection-based displays on 3D objects.
This paper introduces a method that uses multiple-view videos to estimate the 3D position of a badminton shuttle that moves quickly and anomalously. When an object moves quickly, it is observed with a motion blur effect. By utilizing the information provided by the shape of the motion blur region, we propose a visual tracking method for objects that have an erratic and drastically changing moving speed. When the speed increases tremendously, we propose another method, which applies the shape-from-silhouette technique, to estimate the 3D position of a moving shuttlecock using unsynchronized multiple-view videos. We confirmed the effectiveness of our proposed technique using video sequences and a CG simulation image set.