Marc-Antoine Drouin

Deconvolution-Based Structured Light System with Geometrically Plausible Regularization

This paper presents a new deconvolution-based energy formulation for segmenting the image of stripe-based patterns projected by structured light systems. Our framework features an explicit modeling of the blurring introduced by the lens of a structured light system. This allows a significant improvement when working out of focus, a situation which occurs when performing depth measurement. The proposed iterative algorithm includes two steps: a deconvolution and a segmentation. For both steps, a geometrically plausible regularization term is used. It considers the projected displacement induced by the camera, projector and scene configuration. We validate our method using real imagery acquired using off-the-shelf equipment.

Camera-projector matching using an unstructured video stream

This paper presents a novel approach for matching 2D points between a video projector and a digital camera. Our method is motivated by camera-projector applications for which the projected image needs to be warped to prevent geometric distortion. Since the warping process often needs geometric information on the 3D scene that can only be obtained from triangulation, we propose a technique for matching points in the projector to points in the camera based on arbitrary video sequences. The novelty of our method lies in the fact that it does not require the use of pre-designed structured light patterns as is usually the case. The back bone of our application lies in a function that matches activity patterns instead of colors. This makes our method robust to pose, to severe photometric and geometric distortions. It also does not require calibration of the color response curve of the camera-projector system. We present quantitative and qualitative results with synthetic and real life examples, and compare the proposed method with the scale invariant feature transform (SIFT) method and with a state-of-the-art structured light technique. We show that our method performs almost as well as structured light methods and significantly outperforms SIFT when the contrast of the video captured by the camera has been degraded.

Camera–projector matching using unstructured video

This paper presents a novel approach for matching 2-D points between a video projector and a digital camera. Our method is motivated by camera–projector applications for which the projected image needs to be warped to prevent geometric distortion. Since the warping process often needs geometric information on the 3-D scene obtained from a triangulation, we propose a technique for matching points in the projector to points in the camera based on arbitrary video sequences. The novelty of our method lies in the fact that it does not require the use of pre-designed structured light patterns as is usually the case. The backbone of our application lies in a function that matches activity patterns instead of colors. This makes our method robust to pose, severe photometric and geometric distortions. It also does not require calibration of the color response curve of the camera–projector system. We present quantitative and qualitative results with synthetic and real-life examples, and compare the proposed method with the scale invariant feature transform (SIFT) method and with a state-of-the-art structured light technique. We show that our method performs almost as well as structured light methods and significantly outperforms SIFT when the contrast of the video captured by the camera is degraded.

Active 3D Imaging Systems

Active 3D imaging systems use artificial illumination in order to capture and record digital representations of objects. The use of artificial illumination allows the acquisition of dense and accurate range images of textureless objects that are difficult to acquire using passive vision systems. An active 3D imaging system can be based on different measurement principles that include time-of-flight, triangulation and interferometry. While time-of-flight and interferometry systems are briefly discussed, an in-depth description of triangulation-based systems is provided. The characterization of triangulation-based systems is discussed using both an error propagation framework and experimental protocols.

High Resolution Projector for 3D Imaging

This paper proposes a hybrid software-hardware high-resolution projection system for 3D imaging based on fringe projection. The proposed solution combines the advantages of a digital projection with those of an analogue one. It is programmable and allows a high projection rate by avoiding mechanical displacements in the projection system. Moreover, it does not suffer from the limitations of digital systems such as the presence of inter-pixel gaps and limited resolution. The proposed projection system is relatively inexpensive to build since it is composed of a simple arrangement off-the-shelf components. The system is a combination of a low-resolution digital device such as a DMD, LCoS or LCD, some optical components and software to generate the fringe patterns. A prototype of a 3D scanner based on the proposed projection system is used to asses the fitness of the proposed technology.

Efficient representation of the variant PSF of structured light system

This paper proposes a novel and efficient representation of the point-spread function (PSF) well suited for structured light systems used in digital profilometry. For this particular application the PSF is spatially variant over the working volume and the current parametric as well as non-parametric representations are insufficient. We validate our method using a standard data set and imagery acquired using an off-the-shelf multimedia projector and an industrial camera.

Characterizing the impact of optically induced blurring of a high-resolution phase-shift 3D scanner

A model to predict and characterize the impact of out-of-focus blurring on the range uncertainty associated with the measurement by a phase-shift 3D scanner is presented. First, the reduction of the sine wave magnitude introduced by the projector lenses and the camera lenses is considered. Then, the noise reduction effects related to the camera image blurring introduced by the camera lenses are also included in the model. The main results of this study indicate that the uncertainty for a high-resolution system varies and exhibits a slanted “W” shape, which significantly differs from the inverse square of the range expected from the triangulation equation or the slanted “U” shape, which may be intuitively expected when combining blurring caused by a limited depth of field and the triangulation equation. We provide a comprehensive experimental characterization of a purposely constructed 3D scanner designed to isolate the performance degradation caused by out-of-focus projection and acquisition lenses. This scanner is designed to mimic the characteristics of a high-resolution scanner that can be employed for demanding quality control applications. In the tested configurations, the predicted depth-of-fields were within 16.3% of the corresponding measured values. This concordance between the theoretical results and experimental results suggests that the proposed model can be used to assist the design of phase-shift scanners.

A Methodology for Creating Large Scale Reference Models with Known Uncertainty for Evaluating Imaging Solution

We propose a methodology for acquiring reference models with known uncertainty of complex building-sized objects. Those can be used to quantitatively evaluate the performance of passive 3D reconstruction when working at large scale. The proposed methodology combines the use of a time-of-flight scanner, a laser tracker, spherical artifacts and contrast targets. To demonstrate the soundness of the proposed approach, we built a reference model composed of a 3D model of exterior walls and courtyards of a 130m × 55m × 20m Building. The expanded uncertainty of the 3D reference model and the spatial resolution were calculated.