We propose a new system to visualize depth-dependent patterns and images on solid objects with complex geometry using multiple projectors. The system, despite consisting of conventional passive LCD projectors, is able to project different images and patterns depending on the spatial location of the object. The technique is based on the simple principle that multiple patterns projected from multiple projectors interfere constructively with each other when their patterns are projected on the same object. Previous techniques based on the same principle can only achieve 1) low resolution volume colorization or 2) high resolution images but only on a limited number of flat planes. In this paper, we discretize a 3D object into a number of 3D points so that high resolution images can be projected onto the complex shapes. We also propose a dynamic ranges expansion technique as well as an efficient optimization procedure based on epipolar constraints. Such technique can be used to the extend projection mapping to have spatial dependency, which is desirable for practical applications. We also demonstrate the system potential as a visual instructor for object placement and assembling. Experiments prove the effectiveness of our method.
Multiple projectors are also used for applications in light-field displays @cite_8 @cite_12 . For these applications, in order to create the large number of rays needed for the light field, each ray is projected separately for a specific viewpoint and is not intended to be mixed with other rays. This is in contrast with our proposed method, where the multiple independent images are created at the intended depths and on the intended surfaces exactly by leveraging the mixing properties of rays from the projectors.
@cite_12 @cite_8
2159951673 2162369476 1560037313 2014008866
We present a concept for a full-parallax light field display achieved by having users look directly into an array of video projectors. Each projector acts as one angularly-varying pixel, so the display's spatial resolution depends on the number of video projectors and the angular resolution depends on the pixel resolution of any one video projector. We prototype a horizontal-parallax-only arrangement by mechanically moving a single pico-projector to an array of positions, and use long-exposure photography to simulate video of a horizontal array. With this setup, we determine the minimal projector density required to produce a continuous image, and describe practical ways to achieve such density and to realize the resulting system. We finally show that if today's pico-projectors become sufficiently inexpensive, immersive full-parallax displays with arbitrarily high spatial and angular resolution will become possible. X-ray computed tomography (CT) images could be improved using iterative image reconstruction if the 3D cone-beam forward- and back-projection computations can be accelerated significantly. We investigated the feasibility of a field-programmable gate array (FPGA) implementation of the separable footprint (SF) forward projector. A 16-bit fixed-point quantization introduces negligible numerical errors without affecting the perceptual image quality. The SF-based 3D cone-beam projector can be efficiently parallelized and its memory bandwidth reduced by exploiting projection geometry and data locality. We demonstrate a fully pipelined, 75-way parallel hardware architecture of the SF forward projector on a Xilinx Virtex-5 FPGA that can complete one forward projection of a 320×320×61 object over 3,625 views in 6.3 seconds. Active vision techniques use programmable light sources, such as projectors, whose intensities can be controlled over space and time. We present a broad framework for fast active vision using Digital Light Processing (DLP) projectors. The digital micromirror array (DMD) in a DLP projector is capable of switching mirrors "on" and "off" at high speeds (106 s). An off-the-shelf DLP projector, however, effectively operates at much lower rates (30-60Hz) by emitting smaller intensities that are integrated over time by a sensor (eye or camera) to produce the desired brightness value. Our key idea is to exploit this "temporal dithering" of illumination, as observed by a high-speed camera. The dithering encodes each brightness value uniquely and may be used in conjunction with virtually any active vision technique. We apply our approach to five well-known problems: (a) structured light-based range finding, (b) photometric stereo, (c) illumination de-multiplexing, (d) high frequency preserving motion-blur and (e) separation of direct and global scene components, achieving significant speedups in performance. In all our methods, the projector receives a single image as input whereas the camera acquires a sequence of frames. Multi-view autostereoscopic displays provide an immersive, glasses-free 3D viewing experience, but they require correctly filtered content from multiple viewpoints. This, however, cannot be easily obtained with current stereoscopic production pipelines. We provide a practical solution that takes a stereoscopic video as an input and converts it to multi-view and filtered video streams that can be used to drive multi-view autostereoscopic displays. The method combines a phase-based video magnification and an interperspective antialiasing into a single filtering process. The whole algorithm is simple and can be efficiently implemented on current GPUs to yield a near real-time performance. Furthermore, the ability to retarget disparity is naturally supported. Our method is robust and works well for challenging video scenes with defocus blur, motion blur, transparent materials, and specularities. We show that our results are superior when compared to the state-of-the-art depth-based rendering methods. Finally, we showcase the method in the context of a real-time 3D videoconferencing system that requires only two cameras.