A kaleidoscopic approach to surround geometry and reflectance acquisition

Abstract

We describe a system for acquiring reflectance fields of objects without moving parts and without a massively parallel hardware setup. Our system consists of a set of planar mirrors which serve to multiply a single camera and a single projector into a multitude of virtual counterparts. Using this arrangement, we can acquire reflectance fields with an average angular sampling rate of about 120+ view/light pairs per surface point. The mirror system allows for freely programmable illumination with full directional coverage. We employ this setup to realize a 3D acquisition system that employs structured illumination to capture the unknown object geometry, in addition to dense reflectance sampling. On the software side, we combine state-of-the-art 3D reconstruction algorithms with a reflectance sharing technique based on non-negative matrix factorization in order to reconstruct a joint model of geometry and reflectance. We demonstrate for a number of test scenes that the kaleidoscopic approach can acquire complex reflectance properties faithfully. The main limitation is that the multiplexing approach limits the attainable spatial resolution, trading it off for improved directional coverage.

A Linear Extrinsic Calibration of Kaleidoscopic Imaging System from Single 3D Point

“…In the context of kaleidoscopic imaging, Ihrke et al [10] and Reshetouski and Ihrke [19,20] have proposed a theory on modeling the chamber detection, segmentation, bounce tracing, shape-from-silhouette, etc. In these studies, however, the geometric calibration of the mirrors is simply achieved by detecting chessboards first [29], and then by estimating the mirror normals and the distances from chessboard 3D positions in the camera frame.…”

“…While their original motivation is to estimate the 3D structure from its indirect views via mirrors, they can be used for calibrating the kaleidoscopic system by supposing the direct view were not available. For example, the orthogonality constraint on mirrored 3D points proposed by [27] can be considered as another approach for kaleidoscopic system calibration in [10,20].…”

Structured Light in Sunlight

“…Let the optimal block size be K opt ; the image plane is di- 6 Different laser scanning speeds have been used for generating different camera exposures in a structured light setup [7]. sps.…”

“…In both cases, our method achieves highly detailed 3D structure with a limited power budget (illuminance from source ≈ 50 lux) and few (< 50) images. measured by capturing two HDR images of the scene -one with the projector on, and one with the projector off 7 . Binary Gray code patterns were used as the structured light encoding scheme.…”

A Vignetting Model for Light Field Cameras With an Application to Light Field Microscopy

“…A variety of other optically implemented light field camera designs exist that, in principle, are subject to the vignetting effect discussed here since they also have a virtual camera description [1] that is affected by our analysis: External lens arrays placed before the camera achieve a large baseline [10], [11], [12], while mirror arrays are a good way to cover a large field of view [13], [14], [15], [16]. The number of virtual viewpoints in mirror systems can be augmented considerably by utilizing inter-reflections between mirrors [17], [18]. Kaleidoscopic light field imaging [19], [20] uses a light pipe inside a camera for this purpose.…”