Camera Projection Research Articles

Motion-invariant Coding Using a Programmable Aperture Camera

A moving object or camera causes motion blur in a conventional photograph, which is a fundamental problem of a camera. In this research, we propose to code a motion-invariant blur using a programmable aperture camera. The camera can realizes virtual camera motion by translating the opening, and as a result, we obtain a coded image in which motion blur is invariant with the object velocity. Thereby, we recover motion blurs without estimation of the motion blur kernels or knowledge of the object speeds. We model the projection of the programmable aperture camera, and also demonstrate that our proposed coding works for a prototype camera.

プロジェクタカメラ系を用いた光沢感と透明感の実時間操作

プロジェクタカメラ系を用いた光沢感と透明感の実時間操作

Effects of Camera Project Language Activities on Verbal Skills and Creativity of Preschoolers

Effects of Camera Project Language Activities on Verbal Skills and Creativity of Preschoolers

Designing robot eyes for communicating gaze

Abstract—Human eyes not only serve the function of enabling us “to see” something, but also perform the vital role of allowing us “to show” our gaze for non-verbal communication, such as through establishing eye contact and joint attention. The eyes of service robots should therefore also perform both of these functions. Moreover, they should be friendly in appearance so that humans may feel comfortable with the robots. Therefore we maintain that it is important to consider gaze communication capability and friendliness in designing the appearance of robot eyes. In this paper, we propose a new robot face with rear-projected eyes for changing their appearance while simultaneously realizing the showing of gaze by incorporating stereo cameras. Additionally, we examine which shape of robot eyes is most suitable for gaze reading and gives the friendliest impression, through experiments where we altered the shape and iris size of robot eyes. Keywords: Gaze reading; facial design; projector camera system

GPGPU를 이용한 단일 영상에서의 깊이 추정에 관한 연구

In this paper, a depth estimate method is proposed using GPU(Graphics Processing Unit) in monocular image. a monocular image is a 2D image with missing 3D depth information due to the camera projection and we used a monocular cue to recover the lost depth information by the projection present. The proposed algorithm uses an energy function which takes a variety of cues to create a more generalized and reliable depth map. But, a processing time is late because energy function is defined from the various monocular cues. Therefore, we propose a depth estimate method using GPGPU(General Purpose Graphics Processing Unit). The objective effectiveness of the algorithm is shown using PSNR(Peak Signal to Noise Ratio), a processing time is decrease by 61.22%.

An integrated stereo visual odometry for robotic navigation

In this paper, we propose a novel method to accurately estimate the arbitrary motion of a calibrated stereo rig from a noisy sequence. In the proposed method, a projective camera model is used which is appropriate for scenes where the objects are close to the camera or where there is depth variation in the scene. We propose a feature-based method that estimates large 3D translation and rotation motion of a moving rig. The translational velocity and acceleration and angular velocity of the rig are then estimated using a recursive method. In addition, we account for different motion types such as pure rotation and pure translation in different directions. In our studies, we assume that the rig motion is noisy, i.e., the acceleration and velocity of the camera are not perfectly constant. Our experimental results show that we obtain accurate estimates of rotation matrix and translation vector parameters across different test-cases with large and small baselines. For long sequences, the estimated motion parameters are within ±0.2 mm.

Phase error analysis and compensation considering ambient light for phase measuring profilometry

The accuracy of phase measuring profilometry (PMP) system based on phase-shifting method is susceptible to gamma non-linearity of the projector–camera pair and uncertain ambient light inevitably. Although many researches on gamma model and phase error compensation methods have been implemented, the effect of ambient light is not explicit all along. In this paper, we perform theoretical analysis and experiments of phase error compensation taking account of both gamma non-linearity and uncertain ambient light. First of all, a mathematical phase error model is proposed to illustrate the reason of phase error generation in detail. We propose that the phase error is related not only to the gamma non-linearity of the projector–camera pair, but also to the ratio of intensity modulation to average intensity in the fringe patterns captured by the camera which is affected by the ambient light. Subsequently, an accurate phase error compensation algorithm is proposed based on the mathematical model, where the relationship between phase error and ambient light is illustrated. Experimental results with four-step phase-shifting PMP system show that the proposed algorithm can alleviate the phase error effectively even though the ambient light is considered.

Development of an Information Projection Interface Using a Projector–Camera System

SUMMARYThis paper proposes an interface system that enables a user to input and obtain information independent of position within a certain area in an environment with a projector–camera system. Hand gestures detected in the image are used as a cue to start the system, to distinguish gestures based on the user's intention to operate the system from other daily‐life motions, and to specify the position of the user's hand. Hand gesture detection is implemented based on a combination of the background subtraction method and skin color extraction. The user can designate the projection area freely on a flat surface in the environment with his/her hand. The projector is mounted on a pan‐tilt unit that projects information according to the user's indications. Then, the user's fingertip is detected using simple template matching and he/she interacts with the projected information to input commands without any equipment. As one application, we developed an interface system to operate electrical appliances such as a television intuitively in an everyday environment. © 2013 Wiley Periodicals, Inc. Electron Comm Jpn, 96(11): 70–81, 2013; Published online in Wiley Online Library (wileyonlinelibrary.com). DOI 10.1002/ecj.11477

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.

Machine Vision-based Measurement System for Vehicle Body Inspection

The main contribution of the paper is to propose a system for fast and easy measurement of car body parts to support their inspection. The proposed system is composed from a camera-projector (CP) subsystem and a multi-camera and active marker based tracking system (TS). During the reconstruction process rotating gray code pattern is projected onto the targeted surface which improves the robustness and accuracy of the measurement. Afterwards based on triangulation the 3D coordinates of surface points are estimated.

Projective Multiview Structure and Motion from Element-Wise Factorization

The Sturm-Triggs type iteration is a classic approach for solving the projective structure-from-motion (SfM) factorization problem, which iteratively solves the projective depths, scene structure, and camera motions in an alternated fashion. Like many other iterative algorithms, the Sturm-Triggs iteration suffers from common drawbacks, such as requiring a good initialization, the iteration may not converge or may only converge to a local minimum, and so on. In this paper, we formulate the projective SfM problem as a novel and original element-wise factorization (i.e., Hadamard factorization) problem, as opposed to the conventional matrix factorization. Thanks to this formulation, we are able to solve the projective depths, structure, and camera motions simultaneously by convex optimization. To address the scalability issue, we adopt a continuation-based algorithm. Our method is a global method, in the sense that it is guaranteed to obtain a globally optimal solution up to relaxation gap. Another advantage is that our method can handle challenging real-world situations such as missing data and outliers quite easily, and all in a natural and unified manner. Extensive experiments on both synthetic and real images show comparable results compared with the state-of-the-art methods.

A Two-Omni-Camera Stereo Vision System With an Automatic Adaptation Capability to Any System Setup for 3-D Vision Applications

A stereo vision system using two omni-cameras for 3-D vision applications is proposed, which has an automatic adaptation capability to any system setup before 3-D data computation is conducted. The adaptation, which yields the orientations and distance of the two omni-cameras, is accomplished by detecting and analyzing the horizontal lines appearing in the omni-images acquired with the cameras and a person standing in front of the cameras. Properties of line features in environments are utilized for detecting more precisely the horizontal lines that appear as conic sections in omni-images. The detection work is accomplished through the use of carefully chosen parameters and a refined Hough transform technique. The detected horizontal lines are utilized to compute the cameras' orientations and distance from which the 3-D data of space points are derived analytically. Compared with a traditional system using a pair of projective cameras with nonadjustable camera orientations and distance, the proposed system has the advantages of offering more flexibility in camera setups, better usability in wide areas, higher precision in computed 3-D data, and more convenience for nontechnical users. Good experimental results show the feasibility of the proposed system.

Structured light self-calibration with vanishing points

This paper introduces the vanishing points to self-calibrate a structured light system. The vanishing points permit to automatically remove the projector’s keystone effect and then to self-calibrate the projector–camera system. The calibration object is a simple planar surface such as a white paper. Complex patterns and 3D calibrated objects are not required any more. The technique is compared to classic calibration and validated with experimental results.

Multi-projector color structured-light vision

Research interest in rapid structured-light imaging has grown increasingly for the modeling of moving objects, and a number of methods have been suggested for the range capture in a single video frame. The imaging area of a 3D object using a single projector is restricted since the structured light is projected only onto a limited area of the object surface. Employing additional projectors to broaden the imaging area is a challenging problem since simultaneous projection of multiple patterns results in their superposition in the light-intersected areas and the recognition of original patterns is by no means trivial. This paper presents a novel method of multi-projector color structured-light vision based on projector–camera triangulation. By analyzing the behavior of superposed-light colors in a chromaticity domain, we show that the original light colors cannot be properly extracted by the conventional direct estimation. We disambiguate multiple projectors by multiplexing the orientations of projector patterns so that the superposed patterns can be separated by explicit derivative computations. Experimental studies are carried out to demonstrate the validity of the presented method. The proposed method increases the efficiency of range acquisition compared to conventional active stereo using multiple projectors.

Quantitative lung SPECT applied on simulated early COPD and humans with advanced COPD

BackgroundReduced ventilation in lung regions affected by chronic obstructive pulmonary disease (COPD), reflected as inhomogeneities in the single-photon emission computed tomography (SPECT) lung image, is correlated to disease advancement. An analysis method for measuring these inhomogeneities is proposed in this work. The first aim was to develop a quantitative analysis method that could discriminate between Monte Carlo simulated normal and COPD lung SPECT images. A second aim was to evaluate the ability of the present method to discriminate between human subjects with advanced COPD and healthy volunteers.MethodsIn the simulated COPD study, different activity distributions in the lungs were created to mimic the healthy lung (normal) and different levels of COPD. Gamma camera projections were Monte Carlo simulated, representing clinically acquired projections of a patient who had inhaled 125 MBq 99mTc-Technegas followed by a 10-min SPECT examination. Reconstructions were made with iterative ordered subset expectation maximisation. The coefficient of variance (CV) was calculated for small overlapping volumes covering the 3D reconstructed activity distribution. A CV threshold value (CVT) was calculated as the modal value of the CV distribution of the simulated normal. The area under the distribution curve (AUC), for CV values greater than CVT, AUC(CVT), was then calculated. Moreover, five patients with advanced emphysema and five healthy volunteers inhaled approximately 75 MBq 99mTc-Technegas immediately before the 20-min SPECT acquisition. In the human study, CVT was based on the mean CV distribution of the five healthy volunteers.ResultsA significant difference (p < 0.001) was found between the Monte-Carlo simulated normal and COPD lung SPECT examinations. The present method identified a total reduction of ventilation of approximately 5%, not visible to the human eye in the reconstructed image. In humans the same method clearly discriminated between the five healthy volunteers and five patients with advanced COPD (p < 0.05).ConclusionsWhile our results are promising, the potential of the AUC(CVT) method to detect less advanced COPD in patients needs further clinical studies.

Preliminary Study on CAD of Removable Partial Denture Framework

This study explored a method for CAD of removable partial denture (RPD) framework, which contributes to the development of a specialized software system used in restorative dentistry. Point cloud data of a mandibular partially edentulous cast was captured by an optical scanning system with projective grating and high-resolution digital camera. The 3D model of the cast was rebuilt by a CAD software system from the 3D cloud points. Based on the principle of clinical design, the digital survey line and inserting path were determined automaticly. The tissue surfaces and polishing surfaces of every component of RPD were built also by the CAD software. Furthermore, the characteristic structures of the framework including the lingual bar, the internal and external finish lines, the tissue stop were fabricated on the base of the rebuilt model. 3D surface model of the RPD framework was created at last. In this study, geometric model of the RPD framework was fabricated successfully, which took on good fitting, high visibility and easy to modify, and the data converted to STL format that could be read by any other CAD/CAM software system was in preparation for subsequent computer aided manufacture (CAM) of RPD framework.

Calibration of a camera–projector measurement system and error impact analysis

In the camera–projector measurement system, calibration is a key to the measurement accuracy; especially, it is more difficult to obtain the same calibration accuracy for projector than camera due to the inaccurate corresponding relationship between its calibration points and imaging points. Thus, based on stereo vision measurement models of the camera and the projector, a calibration method with direct linear transformation (DLT) and bundle adjustment (BA) is introduced to adjust the corresponding relationships for better optimization purpose in this paper, which minimize the effect of inaccurate calibration points. And an integral method is presented to improve the precision of projection patterns to compensate the projector resolution limitation. Moreover impacts of system parameter and calibration points errors are evaluated when the calibration points positions change, which not only provides theoretical guidance for the rational layout of the calibration points, but also can be used for the optimization of system structure. Finally, the calibration of the system is carried out and the experiment results show that better precision can be achieved with those processes.

Acoustic simulation of the church of San Francesco della Vigna

San Francesco della Vigna is the oldest church in Venice for which there is evidence that acoustic considerations were taken into account in the architectural design. Francesco Zorzi, a humanist scholar, recommended that the church have a flat wooden coffered ceiling to improve the intelligibility of the sermons preached there. But instead of Zorzi’s recommended flat ceiling, the church was built with a plaster vault ceiling. Using measured acoustic data from the CAMERA project, a virtual model of the church was constructed in Odeon whose simulated parameters matched the measured values at different source-receiver combinations. After obtaining a good match to the measured values, this virtual model was then altered to reconstruct the flat ceiling recommended by Zorzi. This ceiling was then placed at the two different heights at which it might have been built in Zorzi’s time. The simulations show that the more absorptive ceiling might have slightly reduced the long reverberation time in the church. However, the ceiling would have been too high to make any significant change in the D50, which still remains extremely low. Thus this simulation indicates that Zorzi’s ceiling would not have made the impact on speech intelligibility he had expected.

Heel strike detection based on human walking movement for surveillance analysis

Heel strike detection is an important cue for human gait recognition and detection in visual surveillance since the heel strike position can be used to derive the gait periodicity, stride and step length. We propose a novel method for heel strike detection using a gait trajectory model, which is robust to occlusion, camera view, and low resolution. When a person walks, the movement of the head is conspicuous and sinusoidal. The highest point of the trajectory of the head occurs when the feet cross (stance) and the lowest point is when the gait stride is the largest (heel strike). Our gait trajectory model is constructed from trajectory data using non-linear optimisation. Then, the key frames in which the heel strikes take place are calculated. A Region Of Interest (ROI) is extracted using the silhouette image of the key frame as a filter. For candidate detection, Gradient Descent is applied to detect maxima which are considered to be the time of the heel strikes. For candidate verification, two filtering methods are used to reconstruct the 3D position of a heel strike using the given camera projection matrix. The contribution of this research is the first use of the gait trajectory in the heel strike position estimation process and we contend that it is a new approach for basic analysis in surveillance imagery.

ACCURACY EVALUATION OF STEREO CAMERA SYSTEMS WITH GENERIC CAMERA MODELS

Abstract. In the last decades the consumer and industrial market for non-projective cameras has been growing notably. This has led to the development of camera description models other than the pinhole model and their employment in mostly homogeneous camera systems. Heterogeneous camera systems (for instance, combine Fisheye and Catadioptric cameras) can also be easily thought of for real applications. However, it has not been quite clear, how accurate stereo vision with these cameras and models can be. In this paper, different accuracy aspects are addressed by analytical inspection, numerical simulation as well as real image data evaluation. This analysis is generic, for any camera projection model, although only polynomial and rational projection models are used for distortion free, Catadioptric and Fisheye lenses. Note that this is different to polynomial and rational radial distortion models which have been addressed extensively in literature. For single camera analysis it turns out that point features towards the image sensor borders are significantly more accurate than in center regions of the sensor. For heterogeneous two camera systems it turns out, that reconstruction accuracy decreases significantly towards image borders as different projective distortions occur.