We propose a novel approach to recovering translucent objects from a single time-of-flight (ToF) depth camera using deep residual networks. When recording translucent objects using the ToF depth camera, their depth values are severely contaminated due to complex light interactions with surrounding environment. While existing methods suggested new capture systems or developed the depth distortion models, their solutions were less practical because of strict assumptions or heavy computational complexity. In this paper, we adopt deep residual networks for modeling the ToF depth distortion caused by translucency. To fully utilize both the local and semantic information of objects, multi-scale patches are used to predict the depth value. Based on the quantitative and qualitative evaluation on our benchmark database, we show the effectiveness and robustness of the proposed algorithm.
@cite_28: The quality of a 3D range scan should not depend on the surface properties of the object. Most active range scanning techniques, however, assume a diffuse reflector to allow for a robust detection of incident light patterns. In our approach we embed the object into a fluorescent liquid. By analyzing the light rays that become visible due to fluorescence rather than analyzing their reflections off the surface, we can detect the intersection points between the projected laser sheet and the object surface for a wide range of different materials. For transparent objects we can even directly depict a slice through the object in just one image by matching its refractive index to the one of the embedding liquid. This enables a direct sampling of the object geometry without the need for computational reconstruction. This way, a high-resolution 3D volume can be assembled simply by sweeping a laser plane through the object. We demonstrate the effectiveness of our light sheet range scanning approach on a set of objects manufactured from a variety of materials and material mixes, including dark, translucent and transparent objects.
@cite_15: We use polarization analysis in triangulation-based laser scanning to disambiguate the true laser stripe from spurious inter-reflections caused by holes and concavities on met al surfaces. Stripe candidates are discriminated by projecting linearly polarized laser light onto the objects, and measuring the polarization state of the reflected light at each pixel of the various candidates. We sketch a model for predicting the polarization state of the true stripe, and report several experimental results.
@cite_26: This paper presents a method for recovering shape and normal of a transparent object from a single viewpoint using a Time-of-Flight (ToF) camera. Our method is built upon the fact that the speed of light varies with the refractive index of the medium and therefore the depth measurement of a transparent object with a ToF camera may be distorted. We show that, from this ToF distortion, the refractive light path can be uniquely determined by estimating a single parameter. We estimate this parameter by introducing a surface normal consistency between the one determined by a light path candidate and the other computed from the corresponding shape. The proposed method is evaluated by both simulation and real-world experiments and shows faithful transparent shape recovery.
@cite_3: We propose a novel, practical solution for high quality reconstruction of axially-symmetric transparent objects. While a special case, such transparent objects are ubiquitous in the real world. Common examples of these are glasses, goblets, tumblers, carafes, etc., that can have very unique and visually appealing forms making their reconstruction interesting for vision and graphics applications. Our acquisition setup involves imaging such objects from a single viewpoint while illuminating them from directly behind with a few patterns emitted by an LCD panel. Our reconstruction step is then based on optimization of the objects geometry and its refractive index to minimize the difference between observed and simulated transmission refraction of rays passing through the object. We exploit the objects axial symmetry as a strong shape prior which allows us to achieve robust reconstruction from a single viewpoint using a simple, commodity acquisition setup. We demonstrate high quality reconstruction of several common rotationally symmetric as well as more complex n-fold symmetric transparent objects with our approach.
Recovering 3-D transparent objects is known to be a challenging research problem in computer vision, and numerous techniques have been proposed to address this problem. Previous techniques utilized the laser scan with polarization @cite_15 or with a fluorescent liquid @cite_28 for the accurate reconstruction of translucent objects. @cite_26 recovered the 3D shape of transparent objects utilizing a known refractive index and the images captured under controlling the background patterns. @cite_3 analyzed the images recorded by projecting several background patterns, and then reconstructed the shape of axially-symmetric transparent objects. Despite of the impressive quality, their capture systems rely on the controlled environment, unlikely applyable to practical applications.