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2005 IEEE Computer Society Conference on Computer Vision and Pattern Recognition (CVPR'05) - Workshops
A steerable projector is a digital projector whose beam can be moved under computer control to illuminate different objects in its environment. Various projects have explored the possibilities of steerable projectors but they have not addressed the calibration of a generalized optical and mechanical system. We present a method for calibrating a device comprised of a projector and a pan-tilt mirror. It starts by obtaining the internal parameters of a camera and the projector, then the pan-tilt mirror is placed in a series of positions and for each one the reflected projector position is calculated from a pattern projected onto a planar surface. From those readings a coarse version of the steerable projector parameters is obtained, which is then iteratively refined. We describe real results from our physical setup and a range of results from simulated data to characterize the performance of our algorithm.
2012 Second International Conference on 3D Imaging, Modeling, Processing, Visualization & Transmission, 2012
Structured-light systems are simple and effective tools to acquire 3D models. Built with off-the-shelf components, a data projector and a camera, they are easy to deploy and compare in precision with expensive laser scanners. But such a high precision is only possible if camera and projector are both accurately calibrated. Robust calibration methods are well established for cameras but, while cameras and projectors can both be described with the same mathematical model, it is not clear how to adapt these methods to projectors. In consequence, many of the proposed projector calibration techniques make use of a simplified model, neglecting lens distortion, resulting in loss of precision. In this paper, we present a novel method to estimate the image coordinates of 3D points in the projector image plane. The method relies on an uncalibrated camera and makes use of local homographies to reach sub-pixel precision. As a result, any camera model can be used to describe the projector, including the extended pinhole model with radial and tangential distortion coefficients, or even those with more complex lens distortion models.
2004
Abstract Projection technology typically places several constraints on the geometric relationship between the projector and the projection surface to obtain an undistorted, properly sized image. In this paper we describe a simple, robust, fast, and low-cost method for automatic projector calibration that eliminates many of these constraints.
We describe a new steerable projector, whose projection center precisely corresponds with its rotation center, which we call a "fixed-center pan-tilt (FC-PT) projector." This mechanism allows it be set more easily to display graphics precisely on the planes in the environment than for other steerable projectors; wherever we would like to draw graphics, all we have to do are locate the FC-PT projector in the environment, and directing it to the corners of the planes whose 2D sizes have been measured. Moreover, by describing multiple planes in the environment by an integrated 2D coordinate system, it can display even a graphic that lies across a boundary line of two planes in a similar way to a paper poster folded along the planes.
The accuracy of 3-D reconstructions depends substantially on the accuracy of active vision system calibration. In this work, the problem of video projector calibration is solved by inverting the standard camera calibration work flow. The calibration procedure requires a single camera, which does not need to be calibrated and which is used as the sensor whether projected dots and calibration pattern landmarks, such as the checkerboard corners, coincide. The method iteratively adjusts the projected dots to coincide with the landmarks and the final coordinates are used as inputs to a camera calibration method. The otherwise slow iterative adjustment is accelerated by estimating a plane homography between the detected landmarks and the projected dots, which makes the calibration method fast.
Journal of Applied Research and Technology, 2014
In this paper we proposed a method for geometric calibration of a projector. This method makes use of a calibrated camera to calibrate the projector. Since the projector works inversely with a camera i.e., it projects the image instead of capturing it, so it can be considered as a reverse camera. The projector is calibrated with the help of a calibrated camera using two types of chessboard, a printed chessboard and a projected chessboard by the projector. The object points of the projected chessboard pattern are measured with the help of calibrated camera and the image points are directly acquired from the chessboard pattern to be projected. Then using these object points and image points the projector is calibrated. Once the projector calibration is done, the transformation matrices (from projector to screen, from camera to screen and from camera to projector) are determined which are used for the reconstruction of the 3D geometry.
2000
Dense surface acquisition is one of the most challenging tasks for optical 3-D measurement systems in applications such as inspection of industrial parts, reverse engineering, digitization of virtual reality models and robot guidance.
2011 IEEE International Conference on Multimedia and Expo, 2011
This paper proposes convenient and useful approaches to automatically calibrate the projectors of a multi-resolution display. The proposed approaches estimate both the keystone effect and misalignment of the projections with an assistance of a color camera. Structured light patterns are employed to construct the geometric relationship between projectors and the projection surface, and then pre-warp the images so that they appear undistorted as a result. Experimental results demonstrate that the proposed approaches successfully reduce the human-effort and lower the calibration time of multi-resolution display calibration task.
2005 IEEE Computer Society Conference on Computer Vision and Pattern Recognition (CVPR'05) - Workshops, 2005
We describe a new steerable projector, whose projection center precisely corresponds with its rotation center, which we call a "fixed-center pan-tilt (FC-PT) projector. " This mechanism allows it be set up more easily to display graphics precisely on the planes in the environment than for other steerable projectors; wherever we would like to display graphics, all we have to do are locating the FC-PT projector in the environment, and directing it to the corners of the planes whose 2D sizes have been measured. Moreover, as the FC-PT projector can recognize automatically whether each plane is connected to others, it can display visual information that lies across the boundary line of two planes in a similar way to a paper poster folded along the planes.
2007 6th IEEE and ACM International Symposium on Mixed and Augmented Reality, 2007
: Basic object manipulation techniques such as translation (a) and rotation (b) are illustrated in long exposure photographs. Augmentation can be projector-based (a-c) or via video-see-through (d). These application examples show basic augmentations of building structures (a,b,d), distance measurements (c) and material-color simulations (c). They are described in more detail in section 7.2.
In the past, 3D shape reconstruction process was based on passive stereo which do not require direct control of any illumination source, instead relying entirely on light. Nowadays, 3D shape reconstruction is based on active stereo which replace one camera with a projector. The projector plays an important part in solving the correspondence problem. It projects coded patterns on the scanned object. By capturing the deformed pattern using cameras, the correspondences between image pixels and projector (columns-rows) can be found easily. To do that, the projector must be calibrated. In this work, the problem of projector calibration is solved by passive stereo and triangulation. Our system consists of two cameras, projector, and planner board. A checkerboard pattern is projected on the board and then captured by the two cameras. Using triangulation, the corresponding 3D points of the projected pattern is computed. In this way, having the 2D projected points in the projector frame and its 3D correspondences (calculated using triangulation) the system can be calibrated using a standard camera calibration method. A data projector has been calibrated by this method and accurate results have been achieved.
In this paper a new calibration method is proposed for projector using an uncalibrated camera. The difficulty to get a set of 2D-3D points in order to compute the projection matrix between the projector and the world has no easy solution. Methods are either inaccurate or inflexible. We propose an easy and automatic way to calibrate a projector. This method is a combination of pattern detection and visual servoing. The idea is to project a calibration pattern and superimpose it on a known printed pattern. We tested and demonstrated the feasibility and accuracy of our approach.
2017 IEEE Conference on Computer Vision and Pattern Recognition (CVPR), 2017
We present a novel method that allows for simultaneous geometric and radiometric calibration of a projectorcamera pair. It is simple and does not require specialized hardware. We prewarp and align a specially designed projection pattern onto a printed pattern of different colorimetric properties. After capturing the patterns in several orientations, we perform geometric calibration by estimating the corner locations of the two patterns in different color channels. We perform radiometric calibration of the projector by using the information contained inside the projected squares. We show that our method performs on par with current approaches that all require separate geometric and radiometric calibration, while being more efficient and user friendly.
2013
The most critical factor affects accuracy of a Structured Light System (SLS) is calibration. Camera calibration is easy to complete because of its extensive study. To simplify projector calibration, previous work models the projector as an inverse camera and tries to build similar 3D-2D mapping data for projector calibration. Achieved mapping data is directly fed to some classic two-step camera calibration methods. When projector comes with a large distortion lens, this kind of methods will fail because their first steps use closed-form solution to calculate initial guess for optimization in next steps. We proposed a new method to calibrate the projector by removing its distortion first. Because projector cannot “see” anything, not like camera case, constraints such as “straight lines remain straight” working just on 2D image is invalid for distortion estimation. With 3D-2D mapping data, the estimation will involve several extra unknowns into a non-linear optimization. We use partia...
Computer Vision and Pattern …, 2009
In this paper we address the problem of geometric cal-ibration of video projectors. Like in most previous meth-ods we also use a camera that observes the projection on a planar surface. Contrary to those previous methods, we neither require the camera to be calibrated nor the pres- ...
2004
Abstract By treating projectors as pin-hole cameras, we show it is possible to calibrate the projectors of a casually-aligned, multi-projector display wall using the principles of planar auto-calibration. We also use a pose estimation technique for planar scenes to reconstruct the relative pose of a calibration camera, the projectors and the plane they project on.
2010 IEEE International Conference on Image Processing, 2010
This contribution deals with the calibration of active stereoscopic systems consisting of a camera and a structured light projector. Usually, expensive equipments like precise calibration pieces or dedicated positioning devices are used for the projector calibration. We developed a flexible calibration method using only a planar target as calibration board without other equipment. The method requires only two image acquisitions from which the projector parameters are estimated using an optimization method. A quantitative evaluation demonstrates the accuracy and flexibility of the proposed calibration method.
2005
Advances in display and input technologies have led to growing desire for creating a more immersive visual experience in interactive display systems. Research on constructing a large-scale, high-resolution display environment based on multi-projector mosaic has also become increasingly important to meet the costeffective consideration. In our previous work, we had developed a system called i-m-Top, which integrated one steerable fovea projector for high-resolution projection and another fixed wideangle projector for low-resolution. The touch-sensing is on the basis of diffused illumination and analyzed by computer vision approach. In this paper, we propose a fast, low-cost method for automatic projector calibration with the assistance of one color camera, to eliminate both the keystone effect and misalignment of the projections. Structured light patterns are projected to construct the geometric relationship between projectors and the projection surface, and then pre-warp the images ...
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
2018 IEEE International Symposium on Mixed and Augmented Reality Adjunct (ISMAR-Adjunct), 2018
Existing camera-projector calibration methods typically warp feature points from a camera image to a projector image using estimated homographies, and often suffer from errors in camera parameters and noise due to imperfect planarity of the calibration target. In this paper we propose a simple yet robust solution that explicitly deals with these challenges. Following the structured light (SL) camera-project calibration framework, a carefully designed correspondence algorithm is built on top of the De Bruijn patterns. Such correspondence is then used for initial camera-projector calibration. Then, to gain more robustness against noises, especially those from an imperfect planar calibration board, a bundle adjustment algorithm is developed to jointly optimize the estimated camera and projector models. Aside from the robustness, our solution requires only one shot of SL pattern for each calibration board pose, which is much more convenient than multi-shot solutions in practice. Data validations are conducted on both synthetic and real datasets, and our method shows clear advantages over existing methods in all experiments.
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.
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