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2003
A system of coordinated projectors and cameras enables the creation of projected light displays that are robust to environmental disturbances. This paper describes approaches for tackling both geometric and photometric aspects of the problem: (1) the projected image remains stable even when the system components (projector, camera or screen) are moved; (2) the display automatically removes shadows caused by users moving between a projector and the screen, while simultaneously suppressing projected light on the user. The former can be accomplished without knowing the positions of the system components. The latter can be achieved without direct observation of the occluder. We demonstrate that the system responds quickly to environmental disturbances and achieves low steady-state errors.
2003
A system of coordinated projectors and cameras enables the creation of projected light displays that are robust to environmental disturbances. This paper describes approaches for tackling both geometric and photometric aspects of the problem: (1) the projected image remains stable even when the system components (projector, camera or screen) are moved; (2) the display automatically removes shadows caused by users moving between a projector and the screen, while simultaneously suppressing projected light on the user. The former can be accomplished without knowing the positions of the system components. The latter can be achieved without direct observation of the occluder. We demonstrate that the system responds quickly to environmental disturbances and achieves low steady-state errors.
2005
Projection systems can be used to implement augmented reality, as well as to create both displays and interfaces on ordinary surfaces. Ordinary surfaces have varying reflectance, color, and geometry. These variations can be accounted for by integrating a camera into the projection system and applying methods from computer vision. The methods currently applied are fundamentally limited since they assume the camera, projector, and scene are static. In this paper, we describe a technique for photometrically adaptive projection that makes it possible to handle a dynamic environment.
IEEE Transactions on Visualization and Computer Graphics, 2004
Front-projection displays are a cost-effective and increasingly popular method for large format visualization and immersive rendering of virtual models. New approaches to projector tiling, automatic calibration, and color balancing have made multiprojector display systems feasible without undue infrastructure changes and maintenance. As a result, front-projection displays are being used to generate seamless, visually immersive worlds for virtual reality and visualization applications with reasonable cost and maintenance overhead. However, these systems suffer from a fundamental problem: Users and other objects in the environment can easily and inadvertently block projectors, creating shadows on the displayed image. Shadows occlude potentially important information and detract from the sense of presence an immersive display may have conveyed. We introduce a technique that detects and corrects shadows in a multiprojector display while it is in use. Cameras observe the display and compare observations with an expected image to detect shadowed regions. These regions are transformed to the appropriate projector frames, where corresponding pixel values are increased and/or attenuated. In display regions where more than one projector contributes to the image, shadow regions are eliminated.
Proceedings of the 2001 IEEE Computer Society Conference on Computer Vision and Pattern Recognition. CVPR 2001, 2001
A major problem with interactive displays based on frontprojection is that users cast undesirable shadows on the display surface. This situation is only partially-addressed by mounting a single projector at an extreme angle and prewarping the projected image to undo keystoning distortions. This paper demonstrates that shadows can be muted by redundantly-illuminating the display surface using multiple projectors, all mounted at different locations. However, this technique alone does not eliminate shadows: multiple projectors create multiple dark regions on the surface (penumbral occlusions). We solve the problem by using cameras to automatically identify occlusions as they occur and dynamically adjust each projector's output so that additional light is projected onto each partially-occluded patch. The system is self-calibrating: relevant homographies relating projectors, cameras and the display surface are recovered by observing the distortions induced in projected calibration patterns. The resulting redundantly-projected display retains the high image quality of a single-projector system while dynamically correcting for all penumbral occlusions. Our initial two-projector implementation operates at 3 Hz.
2003 IEEE Computer Society Conference on Computer Vision and Pattern Recognition, 2003. Proceedings., 2003
Two related problems of front projection displays which occur when users obscure a projector are: (i) undesirable shadows cast on the display by the users, and (ii) projected light falling on and distracting the users. This paper provides a computational framework for solving these two problems based on multiple overlapping projectors and cameras. The overlapping projectors are automatically aligned to display the same dekeystoned image. The system detects when and where shadows are cast by occluders and is able to determine the pixels which are occluded in different projectors. Through a feedback control loop, the contributions of unoccluded pixels from other projectors are boosted in the shadowed regions, thereby eliminating the shadows. In addition, pixels which are being occluded are blanked, thereby preventing the projected light from falling on a user when they occlude the display. This can be accomplished even when the occluders are not visible to the camera. The paper presents results from a number of experiments demonstrating that the system converges rapidly with low steady-state errors.
2003
Photometric variation in multi-projector displays is ar- guably the most vexing problem that needs to be addressed to achieve seamless tiled multi-projector displays. In this paper, we present a scalable real-time solution to correct the spatial photometric variation in multi-projector displays. A digital camera is used to capture the intensity variation across the display in a scalable fashion. This information
… UbiComp Workshop on …, 2004
We believe projectors are currently the best technology for creating very large displays that are flexible, affordable, and easy to configure and deploy. Such displays have nu-merous applications in ubiquitous computing: generating a shared display for a spon-taneous hallway ...
Computer Graphics Forum, 2008
This article report focuses on real-time image correction techniques that enable projector-camera systems to display images onto screens that are not optimized for projections, such as geometrically complex, colored and textured surfaces. It reviews hardware accelerated methods like pixel-precise geometric warping, radiometric compensation, multi-focal projection, and the correction of general light modulation effects. Online and offline calibration as well as invisible coding methods are explained. Novel attempts in super-resolution, high dynamic range and high-speed projection are discussed. These techniques open a variety of new applications for projection displays. Some of them will also be presented in this report.
We recently have seen illumination using Light Emitting Diodes (LEDs) on the street. The current illumination is difficult to control of flexibly and dynamically. In response to this problem, we propose a method controlling numerous LEDs collectively, dynamically, and flexibly by using a projector and small devices with optical sensors. We designed and implemented a small device to achieve our mechanism, which has an LED, an optical sensor, and a microcomputer to react to the light illuminated from a projector. Moreover, it has functions to self adjust the threshold and recognize optical commands, which are required for collective control. We discuss how effective our proposed device was in a study to evaluate it and in field tests done at actual events.
ITE Transactions on Media Technology and Applications
We previously studied methods leveraging pixel-level visible light communication (PVLC) that embeds imperceptible information for human eyes in each pixel of an image. The PC computation load and amount of data transferred between the PC and projector in previous PVLC systems were excessive because the PC executed both the video and data encoding processes. As a result, it was impossible to achieve both high-dynamic-range images and dynamic updates of the images and data. In this paper, we propose a dynamic PVLC system that offers high video quality and interactively updates the PVLC information through hardware encoding processing. Our system can project a 24-bit gradation color PVLC video that contains 64-bit data at 120 fps by synchronously controlling the ON/OFF states of the DMD and LED light sources at the given performance limit of the projector.
2006
Abstract. This paper describes the use of computer vision to support the operation of a handheld projector, and describes four applications. Projectors in the past have been used as fixed devices, but the latest generation of 'pocket projectors' is small and portable. We demonstrate the feasibility of using a projector held in the hand, and the types of applications that can be done with a handheld projector. We attach a camera to the projector to support its operation in two ways.
2001
Abstract We describe a calibration and rendering technique for a projector that can render rectangular images under keystoned position. The projector utilizes a rigidly attached camera to form a stereo pair. We describe a very easy to use technique for calibration of the projector-camera pair using only black planar surfaces. We present an efficient rendering method to pre-warp images so that they appear correctly on the screen, and show experimental results.
Proceedings of the 4th International Symposium on Pervasive Displays, 2015
Emerging research and growing use of mobile projectors reveal a need for better understanding of how to design interaction with such devices. This paper examines key aspects affecting the use of mobile projectors during motion. With the help of two prototypes we explore visibility issues of mobile projectors, in particular how surface colors and geometry affect the visibility of projected information. We then consider the choice of placement of information in the human field of view in the context of peripersonal and extrapersonal spaces. Finally, we raise the issue of body mount location and design implications of long-term use of this type of pervasive display. The paper presents two design explorations using projected displays to address projection on outdoor regular surfaces (snow) and projection on indoor irregular surfaces (indoor and outdoor), in the form of useable prototypes presenting map navigation. Use of the prototypes was explored in various contexts, leading to insights into the limitations and possibilities of such displays. These insights are presented in a set of design considerations intended to inform designers of future mobile projector applications.
Proceedings Visualization, 2001. VIS '01., 2001
Front-projection display environments suffer from a fundamental problem: users and other objects in the environment can easily and inadvertently block projectors, creating shadows on the displayed image. We introduce a technique that detects and corrects transient shadows in a multi-projector display. Our approach is to minimize the difference between predicted (generated) and observed (camera) images by continuous modification of the projected image values for each display device. We are unaware of any other technique that directly addresses this problem. Furthermore, we speculate that the general predictive monitoring framework introduced here is capable of addressing more general radiometric consistency problems such as displaysurface inter-reflections and the changes in display color and intensity due to projector bulb temperature variation.
1999
Abstract Conventional projector-based display systems are typically designed around precise and regular configurations of projectors and display surfaces. While this results in rendering simplicity and speed, it also means painstaking construction and ongoing maintenance. In previously published work, we introduced a vision of projector-based displays constructed from a collection of casually-arranged projectors and display surfaces.
This thesis describes a novel multiple steerable projector system that can display an image anywhere on surfaces in a wide environment. The system can not only display an undistorted image but also control the image's position and size precisely. In addition, by operating the multiple projectors simultaneously, the system can show an image larger or brighter than the capacity of a single projector by tiling or overlaying projected images. These properties enable the system to be utilized in a variety of applications: visual annotations on objects and places, human navigation, a flexible screen for lectures, remote instructions, color and texture simulations of non-textured surfaces, and many other augmented reality (AR) applications. To realize such a projection system, it is necessary first to implement a steerable projector and calibrate it precisely. Calibration has been difficult and unstable,however, because conventional steerable projectors had much more complicated structures than fixed ones. In this thesis, a new structure is proposed, whose projection center corresponds precisely with its rotation center, so that the projection center does not move whichever direction it is oriented in. This unique structure reduces the parameters of the projector and enables its intrinsic calibration to be correct and stable. An extrinsic calibration method is also proposed, which is easy and effective as long as the image is projected onto planar
ACM Transactions on Graphics, 2004
Although display devices have been used for decades, they have functioned without taking into account the illumination of their environment. We present the concept of a lighting sensitive display (LSD)-a display that measures the incident illumination and modifies its content accordingly. An ideal LSD would be able to measure the 4D illumination field incident upon it and generate a 4D light field in response to the illumination. However, current sensing and display technologies do not allow for such an ideal implementation. Our initial LSD prototype uses a 2D measurement of the illumination field and produces a 2D image in response to it. In particular, it renders a 3D scene such that it always appears to be lit by the real environment that the display resides in. The current system is designed to perform best when the light sources in the environment are distant from the display, and a single user in a known location views the display.
2011
Abstract 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.
2008 19th International Conference on Pattern Recognition, 2008
In this paper, a dynamic appearance enhancement method for the less saturated object is proposed. The appearance enhancement method proposed in this paper is realized with a projector camera dynamic feedback system. Therefore, the proposed method has an ability of the rapid and continuous appearance enhancement and it is useful for the human visual perception assistance. Also, the system not
2004
Abstract Projectors have traditionally been used as fixed devices making fixed displays. But projector dimensions are shrinking and projectors are just now on the threshold of being compact enough for handheld use. Should handheld projection prove viable, it offers revolutionary new possibilities for display, with opportunistic projection onto nearby surfaces like walls and tabletops to create a display wherever needed. But there is a missing element here.
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